MSD I - Final Group Report (Biomass-Powered Gas Disctrict Cooling Plant)

GROUP PROJECT REPORT

MECHANICAL SYSTEM DESIGN 1 (MSD 1)

JANUARY 2015 SEMESTER

BIOMASS-POWERED GAS DISTRICT COOLING PLANT DESIGN

SUPERVISOR: IR. KAMARUDDIN SHEHABUDDIN

GROUP MEMBERS MATRIX ID

1. MUHAMMAD ZULFAQQAR BIN MOHD KASIM 14367

2. MUHAMMAD AMIR ADLI BIN NAZARUDIN 16831

3. RAZIN AKMAL B RUSLAN 16931

4. KU MUHAMMAD FAEZ BIN KU ARIFFIN 16917

5. CHOONG WENG HONG 16777

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Table of Content

Content Page

1. Introduction 1

1.1 Overview 1

1.2 Project Background 2

1.3 Problem Statement 3

1.4 Project Objectives 4

1.5 Scope of Project 4

1.5 Selected Datum – KLIA GDC plant 5

2. Methodology 9

2.1 Design Process Diagram 10

3. Concept Generation 11

3.1 Physical Decomposition of Biomass-powered 11 GDC plant

3.2 Functional Decomposition of Biomass-powered 12 GDC plant

3.3 Morphology Chart 13

3.4 Concept Generated (all members) 17

3.4.1 Design Concept (Concept 1: Zulfaqqar’s) 17

3.4.2 Justification of the chosen system (Concept 1: Zulfaqqar’s) 18

3.4.3 Concept sketch (Concept 1: Zulfaqqar’s) 20

3.5.1 Design Concept (Concept 2: Adli’s) 21

3.5.2 Justification of the chosen system (Concept 2: Adli’s) 22

3.5.3 Concept sketch (Concept 2: Adli’s) 24

3.6.1 Design Concept (Concept 1: Razin’s) 25

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3.6.2 Justification of the chosen system (Concept 2: Razin’s) 26

3.6.3 Concept sketch (Concept 2: Razin’s) 28

3.7.1 Design Concept (Concept 1: Faez’s) 29

3.7.2 Justification of the chosen system (Concept 2: Faez’s) 30


3.8.1 Design Concept (Concept 1: Choong’s) 33

3.8.2 Justification of the chosen system (Concept 2: Choong’s) 34


4. Concept Evaluation 11

4.1.1 Fuel Supply & Pre-Treatment System Objective Tree and 37

Decision Matrix

4.1.2 Justification (Fuel Supply & Pre-Treatment system) 39

4.2.1 Co-combustion System Objective Tree and Decision Matrix 41

4.2.2 Justification (Co-combustion system) 43

4.3.1 Co-generation System Objective Tree and Decision Matrix 45

4.3.2 Justification (Co-generation system) 47

4.4.1 Heat Recovery System Objective Tree and Decision Matrix 48

4.4.2 Justification (Heat Recovery system) 50

4.5.1 Refrigeration System Objective Tree and Decision Matrix 51

4.5.2 Justification (Refrigeration system) 53

4.6.1 Heat Rejection System Objective Tree and Decision Matrix 55

4.6.2 Justification (Heat Rejection system) 57

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5. Selected Concept 59

5.1 Winning Concept 59

5.2 Winning concept’s sketch (Faez’s) 62

5.3 Subsystems for winning concept 63

6. Detailed Selected Concept’s Working Principle 65

6.1 Overall system’s working principle 65

6.2 Subsystem’s working principle 67

6.2.1 Working principle (Drying of Biomass) 67

6.2.2 Working principle (Indirect co-firing) 69

6.2.3 Working principle (Gas turbine) 71

6.2.4 Working principle (Heat Recovery Steam Generator) 72

6.2.5 Working principle (Absorption chiller) 74

6.2.6 Working principle (Induced Draft Cross Flow Cooling Tower) 76

6.3 Peer evaluation of the selected concept

6.3.1 Zul’s evaluation 78

6.3.2 Adli’s evaluation 80

6.3.3 Razin’s evaluation 81

6.3.4 Faez’s evaluation 82

6.3.5 Choong’s evaluation 84

7. Governing Equation 86

7.1 Gasification 86

7.2 Closed-cycle Gas Turbine 86

7.3 Absorption Chiller 88

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8. Conclusion 89

9. References 91

List of Figures

Figures Page

Figure 1: KLIA GDC Plant (rear entrance) 7

Figure 2: KLIA GDC Plant (main entrance) 8

Figure 3: KLIA GDC Plant (storage tank and chimneys in view) 8

Figure 4: Physical Decomposition of the Biomass-powered GDC system 11

Figure 5: Functional Decomposition of the Biomass-powered GDC system 12

Figure 6: Rotary dryers operation flow for biomass drying 68

Figure 7: Schematic Diagram of Gasifier 69

Figure 8: Working principle of basic gas turbine 71

Figure 9: Components of HRSG 73

Figure 10: Absorption Chiller 74

Figure 11: Absorption Chiller process 75

Figure 12: Example of fill which being used in the cooling tower 76

Figure 13: Induced Draft Cross Flow Cooling Tower 76

Figure 14: Fan being setup on top of the cooling tower 77

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List of Tables

Table Page

Table 1: Output capacity and demand for KLIA GDC plant 6

Table 2: Main equipment details of the KLIA GDC plant 6

Table 3: Weighted decision matrix for Fuel Supply & Pre-Treatment System 38

Table 4: Weighted decision matrix for Co-Combustion System 42

Table 5: Weighted decision matrix for Co-Generation System 46

Table 6: Weighted decision matrix for Heat Recovery System 49

Table 7: Weighted decision matrix for Refrigeration System 52

Table 8: Weighted decision matrix for Heat Rejection System 56

Table 9: Concept Selection 59

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1. INTRODUCTION

1.1 Overview

District Cooling is a concept in which that the central source is utilised to supply

cooling to a number of buildings instead of using multiple individual cooling systems. The

concept of this system starts with the production of the chilled water in a centralized plant,

and the chilled water will be then distributed through a district cooling system via

underground pipelines to heat exchangers within buildings to provide air cooling [9].

It is very common for the District Cooling system to be coupled along with District

Heating system or/and being integrated along with the Co-Generation system to produce

outputs other than chilled water. District Energy System (DES) for instance, covers both

District Cooling and also District Heating as well. This system will produce and distribute

both steam, as well as chilled water from a centralized plant, to individual buildings to

provide space heating and cooling, domestic hot water, and also industrial process energy

[22]. By having DES, boilers and chillers will no longer have to be installed in individual

buildings and hence could eliminate costs of installing and maintaining those individual

chillers and boilers. This kind of system was widely used in countries/regions which are

experiencing winter as well as summer season.

Meanwhile, the Co-Generation system which also known as Combined Heat and

Power (CHP) system produces both electric supply and also heat supply, from one fuel

source [2]. The electrical output produced will be distributed via national grid network for

domestic use or will be directly used by plants/facilities such as universities, airports,

government buildings, etc. On the other hand, the heat produced by this Co-Generation

system will then be used to generate steam via Heat Recovery Steam Generators (HRSGs)

and the steam produced will be passed through the Absorption Chiller as part of the District

Cooling system to produce chilled water. The chilled water produced will then be distributed

to individual buildings for space cooling and air conditioning. This system is much more

commonly used and existed in most District Cooling Plants. Depending on the type of turbine

used, the Co-Generation system is quite flexible in terms of the usage of fuel. Gas turbines in

the Co-Generation system is mainly utilising natural gas as its main fuel but it could also use

other type of fuel as backup during emergency (fuel depletion) such as the Jet A1 fuel [17]

and also Methane gas.

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Biomass system meanwhile, is renewable and sustainable system which

produces/utilizes fuel out of organic materials that are readily available such as the

agricultural by-products, forest debris, and etc. [22]. The most common types of Biomass

systems are; Direct-fire Biomass system, and also the Biomass Gasification system. For the

Direct-fire Biomass system, the biomass fuel (from organic materials) will be burned in a

boiler to produce a high-pressured steam which will then be used to power the steam turbine-

powered electrical generator. There are also many other applications which utilizes the steam

output from the Direct-fire Biomass system such as for space cooling, space heating, and also

as the process heat for industrial purposes [19].

Differing to the Direct-fire Biomass system, the Biomass gasification system is

basically a means to create fuel (in the form of flammable gas) out of the raw Biomass

source. It starts by heating up the biomass in the environment in which the solid Biomass

breaks down to form a flammable gas [11]. The flammable gas produced (i.e. Methane) will

then could be used for domestic purposes such as cooking and heating, or as the fuel source

for electric generation, or could also be used as the synthetic gas for producing a higher

quality fuels or chemical products such as Methanol and Hydrogen.

1.2 Project Background

This project is mainly to propose a design of the GDC plant which utilizes Biomass as

its main fuel source. The designed GDC plant is supposed to have two useful outputs which

is the electricity and chilled water which will be used internally (not to be supplied to the

outside grid network and also buildings outside the complex). As for the reference for this

project (datum), Kuala Lumpur International Airport (KLIA) GDC plant under the care of

Gas District Cooling (M) Sdn. Bhd. (subsidiary of PETRONAS) will be taken as datum, and

the design will be made mostly in reference to it. All the design specifications and the design

capacity will be referred to the datum chosen (KLIA GDC plant).

Additionally, this project will also be comparing some advantages and disadvantages

of having a Biomass-powered GDC to the gas-powered GDC plant and to the conventional

individual, non-centralized cooling system. The comparison will cover the scopes of energy

efficiency, cost efficiency, ease of maintainability, environmental effects and also the fuel

availability (for Biomass GDC plant and conventional GDC plant).

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Flexibility was given in deciding which components/subsystems to be incorporated

inside the design of the plant in order to achieve the best ever solution in terms of cost and

efficiency. The end product of the design will not necessarily be the same as the datum

chosen earlier and it may have certain improvements in any form of aspects. In this project,

each team members were given a chance to come up with their own concepts with their own

justification, and later, the suggested designs will be evaluated using design concept

generation tools to see which design is the best as a whole.

1.3 Problem Statement

For this project, there are several issues regarding the current conventional GDC plant

and also the individual, non-centralized cooling system which we had found and will be taken

into focus to set our design objectives. The issues are as follows;

• Maintenance issue

In the individual, non-centralized cooling system, all the components for the cooling

system were installed in the individual building, only for the usage of that particular

building alone. If there are 20 buildings in the complex, it means that there will be 20

individual systems installed in each and every building. Having to maintain 20

separate cooling systems will costs a huge money, and massive waste of time and

energy. So, to address this issue, a centralized cooling system needed to be utilized in

the design.

• Cost issue

A conventional gas-powered GDC plant commonly use natural gas (Liquified

Petroleum Gas) as the main source of fuel to power the plant. With ever increasing

price of petroleum-based fuel and also the fact that it is non-renewable, the cost of

running a conventional gas-powered GDC plant will be increasing by time to time.

Hence, cheaper and renewable alternatives for the natural gas must be incorporated

into the design of a GDC in order to provide a means of reducing the running cost of

the currently available GDC plant and at the same time maintaining/improve the level

efficiency of the GDC system.

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• Environmental effect

Commonly, a conventional GDC plant will be using natural petroleum gas as the fuel

to power up the gas turbine. It was known that the usage of natural petroleum gas will

somehow contribute in the depletion of fossil fuel, especially within a plant which

will consume a huge amount of fuel to produce power. On top of that, utilising a fossil

fuel will produce by-products that are harmful to environment. Due to these concerns,

it is very vital to have a design of GDC plant which utilizes alternative fuel that is

clean and renewable as a source to generate power and to produce chilled water for

cooling purposes.

1.4 Project objectives

There are several objectives set for this design project. Those objectives are;

• To produce a Biomass-powered GDC design that has a better or comparable output

compared to conventional GDC.

• To design a cost-efficient Biomass-powered GDC plant throughout its service in

terms of maintenance costs and also in terms of fuel cost.

• To produce a cleaner Biomass-powered GDC by utilising a renewable alternative

source of fuel.

1.5 Scope of project

The project will be focusing on the usage of GDC within Malaysian region and all the

requirements, supply and demand data, required specifications will be made according to the

Malaysian environment. As mentioned earlier in Project Background part, KLIA GDC plant

will be taken as the reference/datum for this design project, and all the outputs, projected

performance and specifications of the Biomass-powered GDC plant to be designed will be

referred and compared to it (KLIA GDC plant).

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Due to time, knowledge and resource limitation, this project will only be focusing

onto 6 out of many critical subsystems of the Biomass GDC Plant. There will be lists of

options of subsystem types to be chosen as design concepts and all of the team members will

be having their individual personal design concepts which will be justified accordingly

according to the concept’s pro and cons. All the preliminary personal design concepts will be

evaluated one after another until a decision can be made on which of the design concept the

best is using the evaluation tool such as Pugh’s Evaluation matrix. The best Biomass GDC

plant concept design will be chosen as the design of choice.

1.6 Selected datum – KLIA GDC Plant

To design a GDC plant that is excellent in terms of its efficiency and reliability, a

datum of an established system must be taken into account as reference. Hence, this design

project had chosen the Kuala Lumpur International Airport (KLIA) GDC plant as the datum.

This GDC plant is owned, being managed, and being maintained by Gas District Cooling (M)

Sdn. Bhd. which is one of the many Petroliam Nasional Berhad’s (PETRONAS) subsidiaries.

Gas District Cooling (M) Sdn. Bhd. is also owns 7 other GDC plants which are serving high

profile development areas within Klang Valley, Kuala Lumpur City Center (KLCC), and also

in Malaysia’s Administrative centre, Putrajaya [8].

KLIA GDC plant’s customers that make use of the chilled water for their air

conditioning needs include, Malaysia Airport (Sepang) Berhad (MAHB) – (For the main

terminal, Administration Management Centre, Satellite A, Contact Pier, Car Park A, B, C

&D complex, VVIP Engineering Complex and Custom Complex of the KLIA), Malaysia

Airline System (MAS) – (Flight Crew Centre & MAS Complex), KL Airport Services

(KLAS) – (KLAS Cargo & KLAS Kitchen), KL International Airport Berhad – (Air Traffic

Controller), Air Asia Berhad – (Air Asia Simulator complex), Kuala Lumpur Airport Hotel

Sdn. Bhd. – (Pan Pacific Hotel)[14]. Meanwhile, most of the electrical output produced by

the GDC plant is being exported to the KLIA grid and small portion of it is being used

internally for the plant’s equipment. All the plant’s output capacity, performance, equipment

and specifications are listed at the following page.

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Table 1: Output capacity and demand for KLIA GDC plant

Table 2: Main equipment details of the KLIA GDC plant

Equipments Remarks Co-Generation system General Electric (GE) LM2500 Gas Turbine

• 2 Units of this Gas turbine installed • Each Gas Turbines produces 20MW of

power • Both Units combined produces total

power of 40MW • Utilizes Natural Gas as main fuel • In case of emergency, Jet-A1 fuel can

be utilized as back-up reserve fuel

Steam Generator System Heat Recovery Steam Generator (HRSG) manufactured and installed by Mechmar Sdn. Bhd.

• 2 Units of this HRSG installed • Each HRSG is capable of producing

output of 40 Tonne/hr of 8 bar pressure of saturated steam

• Both units produces 80 Tonne/hr of saturated steam

• Steam produced by both HRSGs (and auxiliary boilers) is channelled to Steam Absorption Chillers to produce chilled water for cooling

Type of output Capacity

Chilled Water output 30000RT (Refrigeration Tonne – unit for cooling loading capacity)

Electrical output 40 MWe (34MW is distributed to the KLIA grid network and 6MW for the plant’s internal use) [10]

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Refrigeration System & Heat Rejection system Chiller plant, built by Shinryo International Corporation housing 12 units of absorption chillers, and 7 Cooling Towers

• Single absorption chiller’s capacity is 2500 RT (12 x 2500 = 30240 RT)

• Produces chilled water outlet temperature of 7⁰C and the return water inlet 14⁰C

• Return water (from served building complexes) is reused again for steam generation

• Cooling Tower used is the Mechanical Towers type.

• The function of the cooling tower is to create condensate from the return water inlet which is used again for in HRSG for steam generation

Here are some of the pictures of the KLIA Gas District Cooling plant retrieved via Google Streetview and Google Maps;

Figure 1: KLIA GDC Plant (Rear Entrance)

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Figure 2: KLIA GDC Plant (Main Entrance)

Figure 3: KLIA GDC Storage Tank and chimneys in view

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2. METHODOLOGY

In carrying out the design process of the GDC plant, several methods and design tools

will be used. All of the methods and design tools are meant to assist system designers to

make sure each and every aspect of design is thoroughly covered, without having anything

left behind. Below are the methods and tool used in conducting the design process;

a) Taking a Datum/reference for this project

This design project will be referring to an existing GDC plant, KLIA GDC plant as

our datum. All of its output and specifications will be used as reference and will be

compared with the Biomass-powered GDC plan to be designed. The details of the

Datum chosen were presented in the part 1.6 – Selected Datum.

b) Design Process Diagram

Design process diagram functions as the reference of design steps which will be used

in designing the Biomass-powered GDC plant. The Design Process Diagram will be

included later in the end of this chapter.

c) Physical and functional Decomposition of the overall system

Physical Decomposition of the system will be used to help the understanding of the

overall system by dividing the overall complex system into smaller chunks of

subsystems or smaller group of components that are responsible to their respective

functions.

d) Morphological chart

From the Physical and functional decomposition chart, lists of options of

alternatives can be generated for all the subsystems determined earlier. From the lists

of alternatives, several new forms of concepts of Biomass GDC plants could be made.

e) Pugh’s Chart

After having several design concepts of the Biomass GDC plants, all of the design

concepts will be evaluated later on using Pugh’s Chart to determine which conceptual

design is the best. The concepts generated will be compared datum set in all possible

aspects to determine whether it is better or not compared to the datum.

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2.1 Design Process Diagram (Conceptual Design)

Define problem:

• Setting problem statement • Choosing the datum • Determining the Plant Design

Specification

START

Gather Information:

• Via multiple trusted sources; Internet, Patents, Technical articles, journals.

Concept Generation:

• Brainstorming • Functional & Physical decomposition • Morphology chart • Multiple individual concepts

Evaluation of Concept:

• Decision making • Pugh Chart • Decision matrix

END

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Biomass-powered GDC Plant

Fuel supply and Pre-treatment system

(Biomass)

Co-combustion system (Biomass)

Co-Firing

Co-Generation system

Gas Turbine

Steam Generation system

HRSG

Auxiliary Boiler

Refrigeration cycle system

Absorption Chiller

Heat Rejection System

Cooling Tower

3. CONCEPT GENERATION

3.1 Physical Decomposition of Biomass-powered GDC system

Based on the information gathered from the whole working system of the datum (KLIA GDC plant) and also from the requirement needs

for this project, decomposition of the plant was done. This decomposition will only include main systems of the plant which will be the

concentrated more throughout this design project. Figure 4 and figure 5 are the physical and functional decomposition of the Biomass-powered

GDC plant.

Figure 4: Physical Decomposition of the Biomass-powered GDC system

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3.2 Functional Decomposition of Biomass-powered GDC

Figure 5: Functional Decomposition of the Biomass-powered GDC system

Chilled water

Hea

t Electricity Energy

Bio

mas

s

Combust biomass

Prepare and pre-treat biomass

Generate electricity and heat

Chi

lled

wat

er

Generate chilled water

Store and supply

chilled water

Bio

mas

s

Chilled water

Chilled water

Wat

er

Cooling

Returned water

Stea

m

Steam

Steam

Generate steam

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3.3 Morphology chart

After the physical and the functional decomposition of the whole Biomass-powered GDC system, a morphology chart was done in which

all the possible alternatives of components/systems that are possible to be included in the system is being grouped in its own subsystem

classifications. All of the listed alternatives will be chosen to create several Biomass GDC plant concepts.

Subsystem Components & Equipment - Means/How

1 2 3 4 5 Fuel Supply & Pre-Treatment System Pre-treatment of the biomass fuel (e.g.woody/herbaceous) produces upgraded quality of fuel which reduce in storage, transport and handling as well as removing impurities within the fuels.

Pre-treatment of waste wood The waste wood is shredded and added with iron pieces later screened into mesh sizes. Results in wood waste with metals composition.

Balling of fuels Herbaceous fuels pressed into bales (with square or round size) using machines.

Pellets & Briquettes Compressing fuels into cylindrical shape by applying varying processes.

Drying of Biomass Reducing moisture contents of the fuels using different techniques.

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Co-combustion system Combustion of different types of fuel (e.g coal-biomass) at the same time to improve on the combustion rate with lower emission.

Direct Co-firing Involves direct feeding of biomass to coal firing system or furnace.

Indirect Co-Firing Involves gasification of the biomass and the produced fuel gas is used for combustion in the furnace.

Parallel Co-Firing Involves combustion of biomass in different combustor and boiler. Produced steam is utilized for power generation systems.

Co-generation (CHP) system Generation of electricity and useful cooling/heating by utilizing heat engine or power station.

Steam turbines Power derived from expansion of steam to the engine driving electricity generator. Capacity power of (<120 MW).

Gas Turbines Combustion of fuel (natural gas) and air to generate power to drive electricity generator. High efficiency and capable of producing up to 120 MW.

Combined-Cycle Gas/ Steam Turbine Incorporates the gas turbine and steam turbine generating set. HRSG creates steam from exhaust gas to power steam turbine.

Stirling engines Main operation from cyclic compression or expansion of air/other gas to produce work. Small scale applications of 1kW to 100 kW.

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Heat Recovery Steam Generators (HRSG) system Hot waste gases are passed through the heat exchanger which produces steam that is used for cogeneration or powering steam turbine.

Horizontal HRSG The gases flow horizontally with vertical coils providing natural circulation in the system. Simple design with more floor space.

Vertical HRSG The gas flow vertically with horizontal coils and has low air circulation rate that is assisted with water circulation. More compact in design.

Once-Through Steam Generators (OTSG) Advance version of HRSG without boiler drums. Water enters the coil and immediately converts to steam.

Refrigeration Cycle system Circulation of refrigerants through various cycles to absorb or reject heat creating low temperature condition.

Vapor Compression-Cycle Chiller The compressor pumped the refrigerant to a condenser unit to reject heat from refrigerant to cooling water or air outside the system.

Absorption Chiller Mixture of liquid refrigerant water & absorbent with high pressure, directed to condenser which rejects heat.

Exhaust Gas Fired Chiller Double-effect (two-stage absorption system) machine powered from hot exhaust gases and can be direct coupled to combustion engine.

Generator-Absorber Heat Exchange (GAX) cycle Heat Pump Gas-cooling by absorption of heat based on difference from high temperature end of absorber and the low temperature end of generator.

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Heat Rejection System Removal of excess heat from a refrigeration system to the outside environment.

Natural Draft-Type Cooling Tower Inducing airflow from difference of density between the ambient air entering the bottom of tower and vapor mixture leaving the system.

Forced -Draft Cross Flow Cooling Tower Air is forced into the tower from axial flow fans. Hot water distribution system may be used at the bottom.

Forced-Draft Counter Flow Cooling Tower Axial or centrifugal fans mounted at low level forcing air to flow upwards. Enable reduction in overall height of tower.

Induced-Draft Cross Flow Cooling Tower More distribution of air through the tower from axial fans. Available in twin pack versions.

Induced-Draft Counter Flow Cooling Tower Air is circulated using axial flow fans. Input air comes from openings at the base of the tower.

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3.4 Concepts generated (all members)

3.4.1 Design Concept (Concept 1: Zulfaqqar’s)

Subsystem Alternatives

1 2 3 4 5 Fuel Supply & Pre-treatment system

Pre-treatment of waste wood Baling of fuels Pellets & Briquettes Drying of biomass

Co-combustion System Direct Co-firing Indirect Co-Firing Parallel Co-Firing

Co-generation System Steam turbines Gas turbines

Combined-Cycle Gas Turbine/Steam

Turbine Stirling engines

Heat Recovery Steam Generators (HRSG) System

Horizontal HRSG Vertical HRSG Once-through

Steam Generators (OTSG)

Refrigeration Cycle System

Vapor Compression Cycle Chiller Absorption Chiller Exhaust Gas Fired

Chiller

Generator-Absorber Heat Exchange

(GAX) Heat Pump


Natural-Draft Type Cooling Tower

Forced-Draft Cross Flow Cooling Tower

Forced-Draft Counter Flow Cooling Tower

Induced-Draft Cross Flow Cooling Tower

Induced-Draft Counter Flow Cooling Tower

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3.4.2 Justification of the chosen system (Concept 1: Zulfaqqar’s)

a) Fuel Supply and Pre-Treatment system.

For this subsystem, the drying of Biomass raw materials was proposed as the means

of preparation of the Biomass fuel. Drying of Biomass process is very important in

maximizing the energy efficiency of the whole Biomass process. This process is mainly to

eliminate any moisture content that exists in the Biomass raw material before they can be

used as fuel for the next stage; which is the direct co-firing process. By eliminating the

moisture content of the raw Biomass material, the combustion of the fuel can be performed

more efficiently, producing more heat energy.

b) Co-combustion system.

Meanwhile, for the co-combustion system, direct co-firing process was used for this

subsystem. This process is the faster means to consume the Biomass fuel and produce steam

at much faster rate compared to then indirect co-firing system. This means that the waiting

time for a system which adopted the direct co-firing system to start up is much less compared

to the gasification process. Additionally, since this system will be producing steam as its

output, the usage of Heat recovery steam generators (HRSGs) can be omitted from the whole

system. This can be very helpful in reducing the maintenance bills. The less component to

maintain, the cheaper the maintenance bill would be.

c) Co-generation system

Next, it was proposed that this particular subsystem will be using a steam turbine

instead of gas turbine. The main reason for it is since direct co-firing system was adopted in

the design of the GDC system, the only type of turbine that is compatible is the steam turbine.

On top of that, a steam turbine can help reducing the fuel cost as it will not be consuming any

petroleum-based fuel. The price of Natural gas (one of the petroleum-based fuel) kept

increasing, which had cause the cost of running a system with gas turbines also rising. To

curb this, adopting the steam turbine as an alternative will be a very smart choice. Having a

steam turbine adopted in the GDC system could also help in terms of maintenance costs.

Since the process in the steam turbine does not involve any combustion process, there will be

no carbon residue formed within the steam turbine system. This also means there will be no

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reduction of efficiency due to ‘dirty’ turbine internals and there will be no need for

maintenance to address this issue when steam turbine is adopted to the system.

d) Refrigeration cycle system

For this subsystem, absorption chiller was chosen. The main reason for the absorption

chiller to be used in the system is due to its energy efficiency. The absorption chiller

consumes less electricity, which will be very helpful in reducing the electricity bill compared

to the rest. Additionally, the absorption chiller was also known to be quiet and produces less

vibration compared to the other type of chiller. This type of chiller will also be very useful in

eliminating the CFC emission which will be produced by some other chiller system, making

it a greener and cleaner chiller alternative to be used in any plant, particularly in a GDC plant.

e) Heat rejection system

This particular subsystem will be using the induced-draft cooling tower as the main

heat rejection system. The reason for this cooling tower to be chosen is because it is could

sustain a constant airflow regardless of whatever the ambient temperature might be. On top of

that, this type of cooling tower can be adapted to any water flow, slow of fast. This type of

cooling tower is also able to adapt in the condition in which the thermal condition at that time

is severe. (i.e. draught, extreme cold). By having the mentioned qualities above, it is clear

that the induced-draft cooling tower is the best choice of component to be used in the Heat

rejection system.

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3.4.3 Concept sketch (Concept 1: Zulfaqqar’s)

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3.5.1 Design Concept (Concept 2: Adli’s)








Heat Recovery System Horizontal HRSG Vertical HRSG

Once-through Steam Generators

(OTSG)

Condenser Heat Recovery System



Chiller


(GAX) Heat Pump







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3.5.2 Justification of the chosen system (Concept 2: Adli’s)

Fuel Supply & Pre-treatment System

Pre-treatment of waste wood involves processing the waste wood obtained through logging

from the forest. The waste wood is developed into biomass fuel through processing plant

which have four main working steps. In the first step, the wood passes through the low speed

shredder which include 100mm screen basket. Through this, an overband and magnetic roller

remove the iron pieces from the composition of waste wood. Later, the waste wood is

screened through 10mm mesh which separates the ferrous and non-ferrous metal wood. This

results in wood waste which is free from other metal composition or impurities and produced

for size between 10 and 100mm. The beneficial part of this waste wood processing involves a

reduction of costs for ash disposal. It has been shown that pre-treated waste wood have lower

amounts of ashes produced during combustion which result in less deposit formation in the

furnace and the boiler. Therefore, the combustion plant will has better availability and

reduced operating costs due to this initiative.

Co-Combustion System

The indirect co-firing is based on the gasification of biomass where the produced fuel gas will

be combusted directly in the coal-fired furnace. After the gas emitted from combustion of

biomass fuel is passed through the gasifier, the product of the gasification process has low

calorific value fuel gas (syngas) and similar property as natural gas. The gasifier installed in

the indirect co-firing system has the function to process bio-fuel which termed as synthetic

natural gas (SNG). This may acts as a substitute for natural gas as the main source of fuel to

the gas turbine.

Co-generation System

Combined cycle gas turbine & steam turbine incorporates the gas-turbine generator with heat

recovery steam generator (HRSG) and steam-turbine generator, condenser and auxiliary

system. The HRSG acts as the heat exchanger which provides steam from the hot exhaust

gases of the gas turbine and later is used to power the steam turbine. Based on the

cogeneration system, the heat recovered through the HRSG is projected as in the form of

high-pressure steam which later injected to the steam cycles (in steam turbines) to produce

additional power. It is beneficial to employ the combined cycle where the facility or plant has

23

large low or high-pressure steam load where the steam can be used for the intermediate stage

of the steam turbine. Besides, additional electric power generated by the steam turbine can be

used for mechanical drive service in smaller capacity applications. Mainly in facility plants or

district heating/cooling plants this include the use of steam turbines to drive chillers, pumps

and other related equipment. Conventional combined-cycle system is employed where power

plants have medium-to-large scale of power production from 100 MW to 1000 MW. Further,

combine-cycle system has high efficiency compared to conventional power plants and

reduction in compensation cost to the society due to emission of pollution and other damaging

externalities.

Heat Recovery System

Horizontal HRSG design is incorporated with natural circulation under all conditions of

operation. It composed of simple design with fewer platforms and light supporting structure.

Usually, the stack is supported from the ground hence providing zero load acting on the

structure which means greater stability. Basically, it requires pump assistance for blowoff and

draining as the headers are low and the blow tanks are at higher level than the boiler system.


Vapor Compression Chiller basically comprises of four primary components which are the

compressor, evaporator, condenser and metering device. It is equipped with different types of

compressor namely reciprocating, scroll, screw-driven and centrifugal powered by motors or

gas turbines to pump refrigerant to the condenser unit which later rejects heat energy from the

refrigerant to the cooling water or air outside the system. With evaporative cooling, the

coefficient of performance (COP) for this type of chiller is quite high.


Induced-Draft Cross Flow Cooling Tower is equipped with axial fans to give more even

distribution of air through the system but makes control of drift difficult. Due to distribution

of air in the tower, it is able to maintain constant airflow throughout the operation. Besides,

the tower is able to operates in any given operating condition regardless of ambient

temperature (e.g. winter, summer) thus providing maximum performance output.

24

3.5.3 Concept sketch (Concept 2: Adli’s)

25

3.6.1 Design Concept (Concept 3: Razin’s)













Chiller


(GAX) Heat Pump







26

3.6.2 Justification of the chosen system (Concept 3: Razin’s)

Sub-System Justification

a) Fuel Supply and Pre-treatment system

- Drying of biomass

• Able to utilize whole Biomass

process as this process is mainly to

eliminate any moisture content that

exists in the Biomass raw material

before they can be used as fuel for the

next stage

• Eliminating the moisture content

inside the biomass material, will help

the in term of combustion process.

b) Co-combustion system.

- Co - Firing

• Co-firing process was choosen for

this subsystem.

• Able to produce steam steam faster

rate because the biomass is feed

directly to the firing system or

furnace.

• Output of the system is steam

compare to indirect firing which is

fuel gas.

• Able to omitted HRSG from the

system.

c) Co-generation system

- Steam turbine

• Use steam to move the turbine.

• Able to use steam directly from the co

– firing system.

• Less maintenance as no combustion

and carbon deposited on the turbine.

• Save cost as using easily obtainable

renewable resources.

d) Refrigeration cycle system

- Vapor Compression Cycle Chiller

• The vapor-compression uses a

circulating liquid refrigerant as the

medium which absorbs and removes

27

heat from the space to be cooled and

subsequently rejects that heat

elsewhere from the system.

• Relatively inexpensive, so able to

save in term of costing.

• Efficient up to 60%.

e) Heat rejection system

- Forced-Draft Cross Flow Cooling Tower

• Crossflow is a design in which the air

flow is directed perpendicular to the

water flow.

• Gravity water distribution allows

smaller pumps and maintenance while

in use.

• Typically lower initial and long-term

cost, mostly due to pump

requirements.

28

3.6.3 Concept sketch (Concept 3: Razin’s)

29

3.7.1 Design Concept (Concept 4: Faez’s)













Chiller


(GAX) Heat Pump







30

3.7.2 Justification of the chosen system (Concept 4: Faez’s)

Subsystem Alternatives Justification

Fuel Supply & Pre-

treatment system

Drying of biomass - Biomass can be burned efficiently

and much faster due to low

humidity level.

- The amount of energy burnt from

the dry biomass is much higher

compare to other alternatives

- Cheap, easily maintained with

low capital cost.

Co-combustion

System Indirect Co-Firing - Increase the energy produced in

order to drive the turbine much

faster.

- Increase the efficiency of the

burning process of the biomass

product, thus reduce the energy

wasted during the process.

Co-generation

System Gas turbines - High efficiency in producing

power, especially in electricity.

- High power capacity produced.

- Low time taken to generate

electricity as the energy from

combustion is enormous.

Heat Recovery

Steam Generators

(HRSG) System

Vertical HRSG - Low space required, thus save

some space for other equipment.

- Easily maintained as it uses

natural circulation, assisted with

water flow during the process.

31

Refrigeration Cycle

System

Absorption Chiller - Environmental friendly, no CFC

emission.

- Quiet operation, less vibration

produced.

- Lower electricity cost incurred.

- Reliable, yet low in maintenance.

Heat Rejection

System

Induced-Draft Cross Flow

Cooling Tower

- Induces hot moist air quickly.

- Reducing the recirculation effect

due to low input velocities and

high output velocities.

- Increase rate of cooling due to

induced process.

32

3.7.3 Concept sketch (Concept 4: Faez’s)

33

3.8.1 Design Concept (Concept 5: Choong’s)

Subsystem Components & Equipments

1 2 3 4 5 Fuel Supply & Pre-Treatment System

Pre-treatment of waste wood

Balling of fuels

Pellets & Briquettes

Drying of Biomass

Co-combustion system

Direct Co-firing

Indirect Co-Firing

Parallel Co-Firing

Co-generation (CHP) system

Steam turbines Gas Turbines

Combined-Cycle Gas/ Steam Turbine

Stirling engines

Heat Recovery Steam Generators (HRSG) system

Horizontal HRSG

Vertical HRSG

Once-Through Steam Generators (OTSG)

Refrigeration Cycle system

Vapor Compression-Cycle Chiller

Absorption Chiller

Exhaust Gas Fired Chiller

Generator-Absorber Heat Exchange (GAX) cycle Heat Pump


Natural Draft-Type Cooling Tower

Forced -Draft Cross Flow Cooling Tower




34

3.8.2 Justification of the chosen system (Concept 5: Choong’s)

i. Fuel Supply and Pre-Treatment System

Fuel supply and pre-treatment system is functions to prepare the biomass before it is supplied

for energy conversion process. For this subsystem, drying of biomass is chosen. For all

biomass conversion technologies, biomass is heated in order to produce steam or hot gas.

Therefore, the dryness of biomass has significant effect on the efficiency of biomass

conversion process.

Besides that, low moisture content of the biomass feedstock will result in higher energy

efficiency of the conversion process. This is because moisture biomass needs more energy for

heating and vaporizing the moisture content, this energy is lost in the stack. Hence, drying

process of biomass is needed in the design for proper process function and control [21].

ii. Co-Combustion System

Co-combustion system is functions to produce hot gas or steam and uses it to drive turbine

generator. There are three different types of co-combustion system and in-direct firing has

been selected in this design. In-direct firing system is also known as gasification. By

comparing to the direct-firing system, gasification is more environmental friendly. Fuel

contaminants are removed in gasification and it assists in reducing emissions [21].

iii. Co-generation system

Gas turbine is chosen in co-generation system. The reason why gas turbine is chosen is that it

generates high power up to 120MW. High power generation is needed in this design of GDC

system because it is used to power up the plant and supplied to a district.

The second reason is that gasification produce hot gas and it is commonly used to drive gas

turbine. Thus, gas turbine is chosen. The benefits of gas turbine include high reliability and

high power density, which makes it has lower operating cost and higher efficiency compare

to steam turbine. In addition, the exhaust heat from gas turbine has high quality and usable.

The heat produce can be used in other processes such as generate steam [15].

35

iv. Heat Recovery Steam Generator (HRSG) system

HRSG system in this design is functions to convert the waste heat from the exhaust of gas

turbine to steam. Once-through steam generator (OTSG) is picked in this system because it

provides high degree of flexibility as the sections are allowed to grow or contract based on

the heat load from gas turbine.

In this design, the inlet feedwater follows continuous path without segmented sections for

economizers, evaporators and superheater. Moreover, OTSG is a special type of HRSG

which without drum, this characteristic allows for quick changes in steam production and

fewer variables to control [18].

v. Refrigeration Cycle System

Absorption chiller is chosen as the refrigeration cycle system in this design. The use of

absorption chillers eliminates the high incremental cost of electric cooling. Furthermore,

absorption chiller utilize the waste heat from the gas turbine that would otherwise be unused

greatly increases the cost-effectiveness of the systems. Absorption chillers are also have

several non-energy benefits which are environmental friendly and they are elimination the

use of chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) refrigerants, and also

reduction in sound pollution due to its vibration free operation [21].

vi. Heat Rejection System

Natural draft cooling tower has selected as heat rejection system in this design concept. This

type of cooling tower is particularly attractive as a cost-saving solution for larger power

stations and industrial plants requiring greater quantities of cooling water. As this type of

cooling tower operates without fans, the substantial amount of electric power otherwise

required for large cooling tower systems is not needed. The required cooling air is conveyed

through the tower by natural draft thus neither fan nor fan power is required [15].

36

3.8.3 Concept sketch (Concept 5: Choong’s)

37

4. CONCEPT EVALUATION

In this section, evaluation for all concepts will be done through the breakdown of each concept’s subsystems. All of the concept’s

subsystems will be evaluated through several primary and design criteria determined from the objective tree made before the subsystem’s

evaluation. Evaluation will be done through Weighted Decision Matrix (WDM).

4.1.1 Fuel Supply & Pre-Treatment System Objective Tree and Decision Matrix

Fuel Supply & Pre-Treatment System

1.0

Cost

Operation (OPEX)

Capital (CAPEX)

0.5

0.6 0.4

Design

Complexity Reliability

0.2

0.5

0.5

Performance

Quality Productivity

0.3

0.6 0.4

38

Table 3: Weighted decision matrix for Fuel Supply & Pre-Treatment System

Primary Criterion

Design Criterion

Weight factor Unit

Concept 1 – Drying of Biomass (Zulfaqqar)

Concept 2 – Pre-Treatment of waste

wood (Adli)

Concept 3 – Drying of Biomass

(Razin)

Concept 4 – Drying of Biomass

(Faez)

Concept 5 – Drying of Biomass (Choong)

Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate

Cost (0.5)

Operation (OPEX)

(0.6) 0.30 Exp Low 9 2.70 Medi

um 6 1.80 Low 9 2.70 Low 9 2.70 Low 9 2.70

Capital (CAPEX)

(0.4) 0.20 Exp Medi

um 7 1.40 High 3 0.60 Medium 7 1.40 Medi

um 7 1.40 Medium 7 1.40

Performance

(0.3)

Quality of fuel (0.6)

0.18 Exp Medium 6 1.08 Very

Good 8 1.44 Medium 6 1.08 Medi

um 6 1.08 Medium 6 1.08

Productivity (0.4)

0.12 kg / hr 2000 8 0.96 1500

0 10 1.20 2000 8 0.96 2000 8 0.96 2000 8 0.96

Design (0.2)

Complexity (0.5)

0.10 Exp Very Good 8 0.80 Good 7 0.70 Very

Good 8 0.80 Very Good 8 0.80 Very

Good 8 0.80

Reliability (0.5)

0.10 Exp High 8 0.80 High 8 0.80 High 8 0.80 High 8 0.80 High 8 0.80

Total 7.74 6.54 7.74 7.74 7.74

39

4.1.2 Justification (Fuel Supply & Pre-Treatment system)

Biomass fuels have varying quality and characteristics which are mainly dependent

of the types of biomass and pre-treatment technologies applied to these fuels. For example

some of the characteristics of biomass fuels include moisture content which is important for

storage durability and combustion effectiveness, net calorific value (NCV) or gross calorific

value (GCV) that determines the fuel utilization as well as the ash content which provides

information on dust emission, ash utilization or disposal and the combustion technology to be

used. The fuel supply of biomass system consists of planting, harvesting, comminution,

drying, storage as well as transport and handling. The fuel quality of biomass is usually an

important considerations for the operation of biomass combustion plant as well as on

realization of costs incurred from combustion to utilization of the fuels.

The criteria which have been assigned for the Fuel Supply and Pre-Treatment system

include cost, performance and design of the overall pre-treatment technologies. The cost of

the system accounts for 0.5 of the initial weightage for the system as the operator must

consider different circumstances on costs which relates to capital expenditure (CAPEX) as

well as operation expenditure (OPEX) while maintaining profits. Whereas the performance of

the system has been evaluated at 0.3 significance as this includes the quality of fuel as well as

productivity. Further, the design of the system has been given at 0.2 as the complexity and

reliability of the equipment in operation will provide a relation in manpower as well as

maintenance costs.

The operational costs (OPEX) for the system have been given a higher significance

which is 0.6 as these costs are borne by the operator every year during operation of the

system. These costs include maintenance, personnel and transportation costs. For the capital

expenditure (CAPEX), a weightage of 0.4 is given to assess on the initial investment for the

technologies. The magnitude of this criteria has been ranked from high to low based on 11-

point scoring system in which a lower cost incurred for the operation of the system is

preferable. The ranking of each subsystem has been assigned where a score of 9 will be given

for the lowest cost, score of 7 for the medium cost while score of 3 for the highest cost. These

scores are given based on review from Processing Cost Analysis for Biomass Feedstock;

Phillip Badger [2] and Report on Biomass Drying Technology; Wade Amos [3].

40

The quality of fuel is one of the important considerations for this pre-treatment system

as this determines the amount of impurities within the fuel composition. It has been given a

weightage of 0.6. The scoring is based on the level of fuel quality from Low, Medium to

Very Good which is given depending on information from the book of Biomass Combustion

& Co-firing [1]. While the productivity is a measure of output the system may attained in

terms of kg per hour of operation and assessed to has 0.4 significance. The magnitude given

which is 2000 kg/h is the rated output derived from Agromech, a company specialized on

drum driers for biomass drying [16] while 15000 kg/h is the nominal capacity for breakers

from Rudnick-Enners GmbH [4].

The complexity of the design is judged based on the equipments involves in each

system and the operability of these equipments. It has been given a rating from Bad, Good to

Very Good in which the information are derived from Biomass Combustion & Co-firing [1].

Drying of biomass can be done at the outside which reduces its moisture content and later

transferred to drum dryers that are heated directly or indirectly. Whereas the pre-treatment of

waste wood involves using magnetic roller, screening basket and wood breakers to obtain

wood waste which has relatively low impurities contents. In terms of reliability, it has been

given the same merit as complexity at 0.5 and rated based on operational duration of the

system before maintenance or breakdown. All systems are given High consideration due to

the operational data retrieved from Biomass Combustion & Co-firing [1].

41

4.2.1 Co-Combustion Objective Tree and Decision Matrix


1

Cost

Operation (OPEX)

Capital (CAPEX)

0.4

0.6 0.4

Environmental Effect

Contaminants Emission

0.2

1

Quality of Service

Plant Efficiency

Versatility

0.4

0.6 0.4

42

Table 4: Weighted decision matrix for Co-Combustion System

Primary Criterion

Design Criterion

Weight factor

Unit Concept 1 – Direct Co-Firing

(Zulfaqqar)

Concept 2 – Indirect Co-Firing

(Adli)

Concept 3 – Direct Co-Firing (Razin)

Concept 4 – Indirect Co-Firing

(Faez)

Concept 5 – Indirect Co-Firing (Choong)

Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate Cost

(0.40) Operation (OPEX)

(0.6)

0.24 USD$/yr

660K 8 1.92 955K 6 1.44 660K 8 1.92 955K 6 1.44 955K 6 1.44

Capital (CAPEX)

(0.4)

0.16 Exp 9610K

8 1.28 19000K

6 0.96 9610K

8 1.28 19000K

6 0.96 19000K

6 0.96

Quality of Service

(0.40)

Plant Overall

Efficiency (0.70)

0.28 Exp med. 6 1.68 high 7 1.96 med. 6 1.68 high 7 1.96 high 7 1.96

Versatility (0.30)

0.12 Exp med. 5 0.60 high 7 0.84 med. 5 0.60 high 7 0.84 med. 7 0.84

Environmental Effect

(0.20)

Contaminants Emission

(1.00)

0.20 Exp med. 5 1.00 low 8 1.60 med 5 1.00 low 8 1.60 low 8 1.60

Total

6.48 6.80 6.48 6.80 6.80

43

4.2.2 Justification (Co-Combustion System)

Co-combustion system plays a vital role in biomass-based GDC plant and responsible

for driving turbine in order to generate electricity. Hence, it is important to select the most

suitable components listed in the morphology chart based on the criteria shown in the

objective tree that had been constructed.

From the objective tree, one of the main criteria of selecting components for co-

combustion system is cost and the weightage is rated as 0.4. There are two costs are taken

into consideration under the criteria of cost and they are operational (including maintenance)

and capital. Both costs have a weightage of 0.6 and 0.4 respectively. The reason why the

weightage of operational cost is higher than the capital cost is that operational cost has long

term effect on the plant, while capital cost is only taken into account during the initial

expenses.

Besides that, quality of service is also considered as one of the criteria in the objective

tree. The weightage for quality of service is similar to the cost which is 0.4. Under the quality

of service, there are two factors are taken into consideration and they are plant overall

efficiency and versatility. Plant overall efficiency has a weightage of 0.7 while versatility has

0.3. This is because efficiency is the most important criteria in designing. Besides, versatility

of the product produced from co-combustion system is important as the product may only

suitable to drive only one turbine’s type or more. Thus, versatility is considered as one of the

criteria.

Furthermore, environmental effect is also one of the criteria of selecting the

components and has a weightage of 0.2 which is lesser compared to cost and quality of

service. In line with the objective of this project, the emission of contaminants from the co-

combustion system is included as criteria in order to optimize the plant to be more

environmental friendly.

From the five concepts generated, only two components from the morphology chart

are chosen and they are direct co-firing and indirect co-firing. By comparison, direct co-firing

has lower operational and capital cost [21]. Hence, the score for direct co-firing is higher than

indirect co-firing under cost criteria in Table 4.

44

However, in term of plant overall efficiency, indirect co-firing is greater than direct

co-firing. Heat from the turbine exhaust can be recovered when fuel gas, also known as

syngas, produced from indirect co-firing is used to power up gas turbine for generating

electricity. With the heat recovery, the system efficiency can improve to 80% [21]. Moreover,

the syngas produced from indirect co-firing can used to heat up boiler and produce steam.

This makes indirect co-firing is more versatile since it can used to drive steam turbine and gas

turbine. Thus, indirect co-firing has higher score under quality of service criteria in Table 4.

In term of contaminants emission, direct co-firing produces by-products such as flying ash

from the combustion of biomass and these by-products is harmful to environment. In

addition, indirect co-firing emits lesser contaminants compared to direct co-firing [21].

Therefore, indirect co-firing is rated as 8 while direct co-firing rated as 5 for the score of

environmental effect criteria in Table 4.

45

4.3.1 Co-Generation System Objective Tree and Decision Matrix

Co-Generation System

Cost

Design

Operation (OPEX)

Capital (CAPEX)

Complexity Compatibility

1

0.4

0.3

0.6 0.4

0.3

0.3

Performance

Efficiency Reliability

0.4

0.5

0.5

Flexibility

Maintenance Control

0.3

0.6

0.4

Size 0.4

46

Table 5: Weighted decision matrix for Co-Generation System

Primary Criterion

Design Criterion

Weight Factor Unit

Concept 1 Steam Turbine

(Zulfaqqar)

Concept 2 Combined_Cycle Gas /

Steam Turbine (Adli)

Concept 3 Steam Turbine

(Razin)

Concept 4 Gas Turbine

(Faez)

Concept 5 Gas Turbine

(Choong)

Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate

Cost (0.40)

Operation (OPEX) (0.60) 0.24

USD$/kW

-yr

15.00 6 1.44 13.20 7 1.68 15.00 6 1.44 7.30 9 2.16 7.30 9 2.16

Capital (CAPEX)

(0.40) 0.16 USD

$/kW 800 9 1.44 900 8 1.28 800 9 1.44 980 7 1.12 980 7 1.12

Performance (0.40)

Efficiency (0.50) 0.20 % 75 7 1.40 80 8 1.60 75 7 1.40 75 7 1.40 75 7 1.40

Reliability (0.50) 0.20 % 94 7 1.40 95 8 1.60 94 7 1.40 97 9 1.80 97 9 1.80

Flexibility (0.30)

Maintenance (0.60) 0.18 Exp High 6 1.08 Med 7 1.26 High 6 1.08 Fair 8 1.44 Fair 8 1.44

Control (0.40) 0.12 Exp High 6 0.72 Med 7 0.84 High 6 0.72 Fair 8 0.96 Fair 8 0.96

Design (0.30)

Complexity (0.30) 0.09 Exp Med 7 0.63 High 6 0.54 Med 7 0.63 Fair 8 0.72 Fair 8 0.72

Size (0.40) 0.12 Exp Med 8 0.96 Big 7 0.84 Med 8 0.96 Med 8 0.96 Med 8 0.96

Compatibility (0.30) 0.09 Exp Med 8 0.72 Med 8 0.72 Med 8 0.72 High 9 0.81 High 9 0.81

Total

9.79 10.36 9.79 11.37 11.37

47

4.3.2 Justification (Co-Generation System)

The co-generation system is important in the gas district cooling system as it

generates electricity and also useful heat simultaneously. Therefore, it is very important to

choose the proper co-generation system to be run in the gas district cooling system. To

determine and choose the best system, some criteria are listed in the objective tree diagram.

Four main criterias are listed in which focused more on the cost, performance, flexibility and

also the design of the system.

The highest weightage in the objective tree diagram is more towards the cost and also

the performance, in which rated as 0.4 as these two factors is the main objectives in the

selection, which is to get an affordable system with a better performance. In the cost factor,

the operational expenditures (OPEX) is weighed higher then capital expenditures (CAPEX)

with the rating on 0.6 against 0.4. This is due to the annual cost that is need to be in higher

considerations in which including the maintenance, parts replacement and also the client cost.

Even so, the CAPEX also should be as low as possible in order to reduce the overall

expenditures throughout the years.

Other than that, the third and fourth factors are shared together; flexibility and its

design which is rated as 0.3. Flexibility in this term means that how the system operates

without too much hassle when the operator or working dealing with the system. This factor

includes the difficulty of handling the system, and also the difficulty of repairing of

inspecting the system when required to ensure its reliability at its best. For the design criteria,

the sub factors are divided into three, which is the complexity, size and also its compatibility.

Complexity and compatibility are sharing the same weightage which is 0.3 while the size

factor is the a little bit in concern in the selection which is 0.4. This is due to the further

consequences of choosing bigger system in which requires bigger area thus inducing higher

cost. While the complexity and compatibility of the design is more referred to the installation

procedures and also the connection between the systems to the other system in the gas district

cooling plant.

48

4.4.1 Heat Recovery System Objective Tree and Decision Matrix


Cost Design

Operation (OPEX)

Capital (CAPEX)

Maintenance Sizing

1

0.4 0.1

0.6 0.4 0.4

0.6

Quality of service

Output

0.5

1

49

Table 6: Weighted decision matrix for Heat Recovery System

Primary criteria

Design Criterion

Weight factor

Unit Concept 1 Not Selected (Zulfaqqar)

Concept 2 Horizontal HRSG

(Adli)

Concept 3 Not Selected

(Razin)

Concept 4 Vertical HRSG

(Faez)

Concept 5 OTSG

(Choong) Mag Score Rate Mag Score Rate Mag Score Rate Mag Score Rate Mag Score Rate

Cost Operation (OPEX)

(0.6)

0.24 Exp Norm. Norm. Norm. Med 6 1.68 Norm. Norm. Norm. Med 7 1.68 Low 8 1.92

Capital (CAPEX)

(0.4)

0.16 USD Norm. Norm. Norm. 5.8M 8 1.28 Norm. Norm. Norm. 5.8M 8 1.28 Low 9 1.44

Quality of service

Output (1)

0.5 Tn/hr Norm. Norm. Norm. High (40)

8 4 Norm. Norm. Norm. High (40)

8 4 Med (32)

7 3.5

Design

Maintenance 0.04 Exp Norm. Norm. Norm. Hard 5 0.2 Norm. Norm. Norm. Easy 9 0.36 Easy 9 0.36

Sizing 0.06 Area Norm. Norm. Norm. Large 5 0.3 Norm. Norm. Norm. Med 8 0.48 Small 9 0.54

Total

7.0 7.22 7.0 7.8 7.76

50

4.4.2 Justification (Heat Recovery System)

The heat recovery system is important in the gas district cooling system. The function

of this system is to recover the exhaust waste heat. Hence, it is important to choose the

suitable candidate in order to implement this system in our gas district cooling plant. In order

to determine the best heat recovery system, several criteria were listed in the objective tree.

There are three criteria listed in the objective tree diagram for choosing the best heat recovery

system, which are cost, quality of service and design.

The highest weightage in the objective tree diagram is given to the quality of service

which is 0.5. As we need to maximize as much as possible output for the system. Cost is

given second highest weightage in the objective tree diagram after quality of service which is

0.4. Cost also need to be taken into serious consideration as the initial expenses (CAPEX)

and annual operational and maintenance cost (OPEX) cannot be too expensive or beyond the

budget limit. Operational cost (OPEX) is set to 0.6 because this will be the cost client need to

bear in order to run and maintain the equipment throughout the year of usage. As higher cost

will lead to higher expenditure in order to keep the equipment running in good condition.

While 0.4 weightage is given to initial expenses (CAPEX). Even the weightage allocation is

slightly lower than (OPEX) the initial expenses should be low as possible.

Lastly, design also is one of the criteria listed in objective tree in choosing the best

component. The weightage is given 0.1 which is the lowest compare to the other criteria.

Under this criterion there is complexity which is given 0.4 weightage and sizing 0.6. As the

complexity of the heat recovery system is almost the same more weightage is allocate to the

sizing category. Sizing refer to the area size of the plant will be build and constructed, bigger

area will promote to higher expense in constructing it. Remaining area are able to use for

other important equipment or usage.

51

4.5.1 Refrigeration System Objective Tree and Decision Matrix

Refrigeration system

Cost Performance Environmental Effect

Operation (OPEX)

Capital (CAPEX)

Efficiency Output Capacity

CO2 Emission

1

0.3

0.5

0.2

1

0.6

0.4

0.4

0.6

52

Table 7: Weighted decision matrix for Refrigeration System

Primary Criterion

Design Criterion

Weight factor

Unit Concept 1 –Absorption Chiller

(Zulfaqqar)

Concept 2 – Vapor Compression Chiller

(Adli)

Concept 3 – Vapor Compression Chiller

(Razin)

Concept 4 – Absorption Chiller

(Faez)

Concept 5 – Absorption Chiller

(Choong) Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate

Cost (0.3)

Operation (OPEX)

(0.6)

0.18 USD$/yr

104K 7 1.26 73K 9 1.62 73K 9 1.62 104K 7 1.26 104K 7 1.26

Capital (CAPEX)

(0.4)

0.12 USD$

571K 6 0.72 540K 7 0.84 540K 7 0.84 571K 6 0.72 571K 6 0.72

Performance (0.5)

Efficiency

(0.4)

0.20 Exp mid 5 1 high 7 1.4 high 7 1.4 mid 5 1 mid 5 1

Output Capacity

(0.6)

0.30 RT 2500 9 2.7 325 4 1.2 325 4 1.2 2500 9 2.7 2500 9 2.7

EnvironmentEffect (0.2)

CO2 Emission

(1)

0.20 kg/GJ

20 8 1.6 30 7 1.4 30 7 1.4 20 8 1.6 20 8 1.6

Total

7.28 6.46 6.46 7.28 7.28

53

4.5.2 Justification (Refrigeration System)

Another subsystem that played an important factor in Gas District Cooling system is

the Refrigeration system. Refrigeration system is the system where the production of the

chilled water for the usage of consumer occurs. The aim for the Refrigeration system need to

achieve is to have a system that is economically feasible (for both initial cost and operating

cost), to have an excellent performance throughout its useful life, and also to be as

environmental friendly as possible. The evaluation will be done by considering several

criteria that are relevant to the above aims. The criteria will be given weightage and will be

rated using the 10-point scoring system. By the end, the concept which gains the highest total

rating will be the winning concept for this particular subsystem.

For this particular subsystem, three primary criteria that are most relevant were

identified. The criteria are; cost, performance and environmental effect. Similar to any

engineering projects, cost played a pivotal role in a project to determine whether it is feasible

or not. Investors will mostly be looking at the cost criteria to decide whether it is worth or not

to invest into a particular project. However, despite of its importance, cost criterion was

assigned with the second highest weightage (0.30) as it is less crucial in comparison to the

performance criterion, at least only for this subsystem. Like any other subsystems, the capital

expenditure (CAPEX) and operational expenditure (OPEX) were taken into consideration

with OPEX has been given with a higher weightage (0.6) compared to CAPEX (0.4) due to

its long term importance.

Meanwhile, the second primary criterion which is the performance has been assigned

with the highest weightage (0.5). The reason for this is because the performance of the

refrigeration system is very important as it will determine the production output of the chilled

water distribution. If there is any performance drop for this subsystem, it will heavily affect

the chilled water production, which is the main product for a GDC plant. Under the

performance criterion, there are two design criterions considered. Both of them are

efficiency, and output capacity. The output capacity has been given the weightage of 0.6,

which is higher than the efficiency (0.4) since the output capacity of chilled water is the

utmost priority for the refrigeration subsystem, particularly for a GDC plant.

54

Finally, the last primary criterion to be evaluated is the environmental effect which

takes up the weightage of 0.2. Environmental concerns are still one of the important part to be

considered in this subsystem and that is the main reason why does the environment effect was

taken as one of the factors in consideration. However, despite of its importance, it does not

outweigh the other two primary criterions – cost and performance. The only design criterion

set under the environmental effect is the CO2 emission from the refrigeration system. Highest

score will be given to the system which adopting the refrigeration system that has the lowest

CO2 emission.

In this subsystem, concepts that are Absorption Chiller as the choice for the

Refrigeration System has the highest overall score (7.28) followed by the Vapor Compression

Chiller (6.46). In terms of Cost, the Absorption chiller has been given the score of 7 for the

OPEX because the cost to run the Absorption chiller in long term is considerably low.

However, the Vapor Compression Chiller has a much lower operational cost and has been

given a higher score (9). For the CAPEX, Absorption chiller had scored 6, which is slightly

lower than the Vapor Compression chiller (7) because the absorption chiller system is a bit

expensive as far as the first cost is concerned for the system.

In term of performance, the Absorption chiller had been given the score of 5 in terms

of overall efficiency for being slightly less efficient compared to the Vapor Compression

Chiller overall. However, in terms of the output capacity, the absorption chiller is far more

superior because it is capable to produce about 8 times more chilled water output than the

Vapor compression chiller. Due to that reason, the absorption chiller had been given the score

of 9. Finally, in terms of the environmental effect, the absorption chiller did slightly better

than the Vapor Compression chiller as the amount of the CO2 emitted by the absorption

chiller is 20kg/GJ which is 10kg/GJ less than the Vapor Compression Chiller and is also

generally low by industry standard. Due to this, the absorption chiller has been given the

score of 8.

55

4.6.1 Heat Rejection System Objective Tree and Decision Matrix


1

Cost

Operation (OPEX)

Capital (CAPEX)

0.5

0.6 0.4

Design

Complexity Adaptability

0.3

0.6

0.4

Performance

Flowrate

0.2

1

56

Table 8: Weighted decision matrix for Heat Rejection System

Primary Criterion

Design Criterion

Weight factor

Unit Concept 1 – Induced Draft Cross Flow Cooling Tower

(Zulfaqqar)

Concept 2 – Induced Draft Cross Flow Cooling Tower

(Adli)

Concept 3 – Forced Draft Counter Flow

Cooling Tower (Razin)

Concept 4 – Induced Draft Cross Flow Cooling Tower

(Faez)

Concept 5 – Natural Draft Cooling Tower

(Choong)

Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate Mag. Score Rate Cost (0.5)

Operation (OPEX)

(0.6)

0.30 Exp med. 6 1.8 med. 6 1.8 high 3 0.9 med. 6 1.8 low 8 2.4

Capital (CAPEX)

(0.4)

0.20 Exp med. 6 1.2 med. 6 1.2 med. 6 1.2 med. 6 1.2 high 3 0.6

Performance (0.2)

Flowrate

(1)

0.20 m3/hr

480 6 1.2 480 6 1.2 768 8 1.6 480 6 1.2 36.5K

3 0.6

Design (0.3)

Complexity

(0.6)

0.18 Exp med. 6 1.08 med. 6 1.08 high 4 0.72 med. 6 1.08 low 8 1.44

Adaptability

(0.4)

0.12 Exp high 8 0.96 high 8 0.96 low 3 0.36 high 8 0.96 low 3 0.36

Total

6.24 6.24 4.78 6.24 5.4

57

4.6.2 Justification (Heat Rejection System)

One of the important subsystems that exist in the Gas District Cooling system is the

heat rejection system. The main role of the Heat Rejection System is to reject waste heat from

the overall system of the Gas District Cooling plant. This waste heat may come from the

auxiliary boilers, gas turbines and several other components that require cooling. The primary

criterions that are being taken into consideration for the selection of the best Heat Rejection

System are; cost, performance, and also design. All of these criterions were given their own

respective weightage according to their level of importance towards the overall subsystem

and also to the whole main system. There are also design criterions, placed under all primary

criteria and will also be given their own respective weightage according to their level of

importance. All of the criterion will be given scores and 10-point scoring system will be

utilized where 0 is the lowest score given, indicating the worst and 10 is the highest,

indicating the best.

The first primary criterion considered for this subsystem is Cost which carries the

weightage of 0.5. Cost has been given the highest weightage compared to the rest of the

criterion is because of its importance in affecting the feasibility of this project in both short

term and long term. Investors will be using cost as their main reference to see whether it is

worth enough for them to invest to this project for both short and long term. Under the Cost

criterion, there are two design criterions being set which is the capital expenditure (CAPEX)

and also the operational expenditure (OPEX). OPEX for this subsystem has been assigned

with the weightage of 0.6 as compared to CAPEX’s 0.4. The main reason for this is because

the main concern of cost for this particular subsystem is the long term cost. The Heat

Rejection System will be used for quite a long time and it is particularly important to make

sure that the cost to maintain it to be as minimal as possible to ensure a high profitability.

Next, the second primary criterion considered for this subsystem is the performance.

The subsystem’s performance in delivering an optimum flowrate of cooled condensate (to

cool the system) has been considered as well. However, the performance is the least concern

for this subsystem because it is not as important as the other criterion. Hence, due to this, the

performance criterion was given with the least weightage which is 0.2. Under the Flowrate,

the only design criterion considered is the flowrate (in m3/hr). As mentioned earlier, this

flowrate refers to the flowrate of cooled condensate produced from this subsystem.

58

On top of that, another vital primary criterion considered for this system is the design.

This criterion has been given the second highest weightage (0.3) due to its importance in

affecting the cost criterion as well as the performance criterion. Under Design, there are

another two criterions considered which are the system complexity and also the system

adaptability. System complexity will affect heavily on the cost, especially the OPEX because

if the Heat Rejection system is too complex, the maintenance work will be a bit complex,

hence causing the operating cost to soar. Meanwhile, the system adaptability refers to the

capability of the system to adapt to various kinds of environmental conditions and at the same

time maintaining its optimum performance. Under this criterion, system complexity has been

given the weightage of 0.6 and the system adaptability has been given the weightage of 0.4.

In this subsystem, concepts that are utilizing Induced Draft Cross Flow Cooling

Tower as the choice for the Heat Rejection System has the highest overall score (6.36)

followed by the Natural Draft Cooling Tower (5.1) and finally the Induced Draft Counter

Flow Cooling Tower (4.72). In terms of Cost, the Induced Draft Cross Flow Cooling Tower

has been given the score of 6 for the OPEX because the operational cost of the Induced Draft

Cross Flow Cooling Tower is comparatively lower than the Forced Draft Counter Flow

Cooling Tower due to its simpler design and a bit higher than the Natural Draft Cooling

Tower since the Induced Draft Cross Flow Cooling Tower uses some electricity to power up

the fan to suck out all the air from the chamber. For the CAPEX, Induced Draft Cross Flow

Cooling Tower had also scored 6, which is the same as the Forced Draft Counter Flow

Cooling Tower as the capital cost for both is comparatively the same and also much less than

the CAPEX of the Natural Draft Cooling Tower.

In term of performance, the Induced Draft Cooling Tower had been given the score of

6 as well as it is able to handle the near-optimum flowrate which is 480 m3/hr. However, the

Forced Draft Counter Flow Cooling Tower had performed better as it is able to handle 768

m3/hr. Meanwhile the Natural Draft Cooling Tower is able to handle about 36500 m3/hr

which is too high for a Gas District Cooling plant. Finally, in terms of design, the Induced

Draft Cross Flow Cooling Tower had scored 6 out of 10 for the system complexity, as its

system is moderately complex compared to Natural Draft Cooling Tower but a little bit

simpler than the Forced Draft Counter Flow Cooling Tower. As far as the system adaptability

goes, the Induced Draft Cross Flow Cooling Tower scored the highest point among the rest as

it is very capable to adapt to changes in working environment/parameters.

59

5. SELECTED CONCEPT

5.1 Winning Concept

The finalized rating for the evaluation concepts are presented in the table below:

Table 9: Concept Selection Subsystem Concept

Fuel Supply &

Pre-Treatment

System

Co-Combustion

System

Co-Generation

System




Total

Concept 1 (Zulfaqqar) 7.74 6.48 9.79 7 7.28 6.36 44.65

Concept 2 (Adli) 6.54 6.80 10.36 7.22 6.46 6.36 43.74

Concept 3 (Razin) 7.74 6.48 9.79 7 6.46 4.72 42.19

Concept 4 (Faez) 7.74 6.80 11.37 7.80 7.28 6.36 47.35

Concept 5 (Choong) 7.74 6.80 11.37 7.76 7.28 5.10 46.05

Based on the table and values calculated above, it can be seen that Concept 4 has the

highest rating in total by using the weighted decision matrix. The criteria chosen are based on

the aspects required for the operation of the gas district cooling system. The scores obtained

are given by the evaluation all indicators in each criterion for every alternative available in

the subsystem.

In this project, the cost has been the major concern for evaluating the alternatives in

the subsystem. This factor is to ensure that the project proposal is capable in minimizing cost

required and at the same time maximize the efficiency of the system for the usage of the

desired customers or buildings. However, Health, Safety and Environment (HSE) in the

industry standards needs to be taken seriously into account to avoid any bad occurrences of

any catastrophic event.

Based on the weightage scores calculated above, the highest score is in the Concept 4

with the score of 47.35. The chosen concept has scored all six subsystems listed which are the

fuel supply and pre-treatment system, co-combustion system, co-generation system, Heart

recovery system (HRS), refrigeration cycle system, and heat rejection system. Unfortunately,

the total score might be unfair as some concepts do not require HRS system due to the usage

of steam turbine in their concepts. However, taking into account of the average score for HRS

60

system is 7, the maximum score that can be compensated is 44.65, which is still lower that

the highest score calculated earlier.

Concept 4 uses drying of biomass system before entering the indirect co-firing

system. The reason behind the selection of this concept is basically to maximize the heat

produced and at the same time to reduce time taken to burn the biomass materials due to the

presence of humidity in the materials. The selection of indirect co-firing is basically to

produce fuel gas in which will be using by the gas turbine. This includes the process of

gasification of the organic materials in the biomass itself.

In the selection of co-generation system, gas turbine is still one of the best turbines

available so far in the market compare to the other turbines. This is due to the high efficiency

produced by the gas turbine to generate electricity, smaller in size and also capable in

producing high power output for large usage from the customers or buildings. The excess

heat produced by the gas turbine can be channelled back to the vertical HRS system in order

to produced useful steam to be channelled to the refrigeration system. The selection of

vertical-based system is basically to use the density differences of hot and cold air so that the

proper steam can be produced.

On the other side, the selection of absorption chiller and also induced-draft cross flow

cooling tower is basically due to its efficiency, availability of its replacement parts and also

the capability of producing cooled water in a short time with the mixture of refrigerant. The

induced-draft cooling tower is selected due to presence of hot air in which will naturally goes

up to the atmosphere. This process also will reduce the recirculation in which the discharged

air enters back into the intake due to low entry and high exits of air velocities. The overall

concept sketch for the selected concept is shown:

61

Winning concept’s selection matrix (Faez’s)













Chiller


(GAX) Heat Pump







62

5.2 Winning concept’s sketch (Faez’s)

63

5.3 Subsystems for winning concept Fuel Supply & Pre-Treatment System:

Drying of Biomass

Co-Combustion System:

Indirect Co-firing

Co-Generation System:

Gas Turbines

64

Heat Recovery System:

Vertical Heat Recovery Steam Generator

(HRSG)

Refrigeration Cycle System:

Absorption Chiller

Heat Rejection System:

Induced Draft Cross Flow Cooling Tower

65

6. DETAILED SELECTED CONCEPT’S WORKING PRINCIPLE 6.1 Overall system’s working principle The new system working principle is based on following subsystem which is:

1- Fuel supply and pre-treatment – Drying of biomass

2- Co Combustion system – Indirect co firing

3- Co-generation system – Gas turbines

4- Heat recovery system – Vertical HRSG

5- Refrigeration cycle system – Absorption Chiller

6- Heat rejection system – Induced draft cross flow cooling tower.

Initially,the process starts with drying the biomass material. Due to the moisture and water

content in the material, it is recommended to reduce it by applying various drying methods which can

improve the efficiency of combustion system. After drying process completed, gasification process

will take place. In this process the biomass solid is converted into the combustible gases. The output

of this process is synthesis gas (syngas) which can be used to produce heat energy by combusting it.

The gas then is used to power up gas turbines. Gas turbines will generate electricity and the excess

exhaust heat will be recovered using heat recovery steam generator. HRSG will mainly absorb heat

from the hot exhaust and produce steam. The steam then enter absorption chiller. Function of

absorption chiller is to reject heat and create low temperature condition for steam by circulate it with

mixture of liquid refrigerant water and absorbent with high pressure. Low temperature steam then is

supplied to the consumer. Lastly, induced draft cross flow cooling tower is used to remove excess

heat from the refrigeration system to outside environment.

66

Selected concept’s process flow

Exhaust Heat

Indirect Co-firing System

(Gasification)

Drying of Biomass

Compressor

Combustion Chamber

Gas Turbine Generator

Electricity

Fuel Gas

Dry Biomas

Vertical HRSG

Steam Steam Absorption

Chiller

Chilled Water

Returned Chilled Water

Steam

Induced Draft Cross Flow

Cooling Tower

Water

Air

67

6.2 Subsystem’s working principle 6.2.1 Working Principles (Drying of Biomass)

Biomass fuels mainly contain a portion of water in the contents which termed as moisture

content. It is recommended to reduce the moisture content by applying various drying

methods which can further improve the efficiency of the combustion system. Besides

utilization of fuel with low moisture content can also lowers the investment cost due to more

complex technology and process control that mainly affect fuel with high moisturization [3].

Drying of biomass fuels can be seen as economical way of saving on total fuel costs due to its

simple process. Basically, the wood logs are piled outdoors with temperature ranging from

35oC above during the summer which naturally reduced the moisture content by 50 to 30

wt% (w.b.) from convection [3]. However, the piling of wood outdoor is only accomplished

in the initial stage as the humidity or uncertain weather conditions may affect the biological

degradation of wood due to micro-organisms. Afterwards, the biomass fuels are passed

through to a continuous drying technologies which may include belt dryers, drum dryers, tube

bundle dryers and superheated steam dryers. Drum dryers in the form of rotating drum is

most commonly used drying technologies in biomass sector [13].

Rotary dryers has several variations for its design but the most-widely used in industry is the

directly heated single-pass rotary dryer. Usually, the biomass material (e.g. wood chip) are

filled into a rotating drum which are fed with hot gas that later react with each other. While

rotating, the solids in the dryer are lifted that causes reaction with the hot gas flowing in the

system while enhancing the heat and mass transfer. Normally, the hot gas can be in the form

of flue gas or heated incoming air from a burner or steam heater. Inside the rotating drum, the

biomass and hot air flow co-currently which leads to the hottest gases to come in contact with

the wettest material [13].

Fine particles which are contained in the exhaust gases leaving the dryer are screened through

a cyclone or multicyclone. Indirectly heated rotary dryer operates based on heat conduction

where heat is transferred from steam or hot air which passes through the outer wall of the

dryer or even inner central shaft of the drum [13]. This design is mainly applied where the hot

flue gases or air may contaminate the material within the dryer thus reducing the system

performance.

68

Inlet gas coming through the rotary dryers may include temperature ranging from 450o -

2,000oF (232o - 1,093oC). Outlet temperature from rotary dryers have ranges from 160o -

230oF (71o - 110oC) and in most cases the outlet temperatures are higher than 104oC to avoid

condensation of acids and resins [13].

Figure 6: Rotary dryers operation flow for biomass drying

69

6.2.2 Working Principles (Indirect Co-firing)

Indirect co-firing system as known as gasification is a process that converts solid

biomass into combustible gases. It is a thermochemical process involving heating the solid

biomass in an oxygen-starved environment, partial oxidation, or indirect heating in the

absence of oxygen to produce fuel gas called synthesis gas (syngas). Syngas produced can

used to produce heat energy by combusting it. The heating value of syngas is within the range

of 10 to 50% that of natural gas, depending on the carbon and hydrogen content of the

biomass and the properties of gasifier [21].

A schematic diagram of a typical gasifier is shown in Figure 7. The gasification

process follows several steps and the first step is pyrolysis. Pyrolysis is a step where thermal

decomposition of solid biomass takes place and vaporizes the volatile components of the

biomass at around 1000°F. The volatile vapours are mainly hydrogen, carbon monoxide,

carbon dioxide, methane, hydrocarbon gases, tar and water vapour. Since biomass feedstock

tend to have more volatile components 70 to 86% on a dry basis, pyrolysis plays vital role in

gasification of biomass [21].

Figure 7: Schematic Diagram of Gasifier

Pyrolysis is followed by further gasification process that converts the leftover tars and

char into carbon monoxide by using provision of addition heat such as steam or partial

combustion. Some of the tars and hydrocarbons in the vapours are thermally cracked to give

smaller molecules, with higher temperatures resulting in fewer remaining tars and

hydrocarbon. The char is converted into gas by various reactions between carbon dioxide and

70

steam through steam gasification to generate carbon monoxide and hydrogen. For the

production of hydrogen, higher temperatures and pressures are prefer, while carbon

monoxide production is prefers higher temperatures and carbon dioxide production is prefers

higher pressures [21].

The gases formed from these processes are further react with the reverse water-gas

shift reaction in order to change the concentration of carbon monoxide, steam, carbon dioxide

and hydrogen within the gasifier. In the end, mixture of the gases is produced from the

gasification process and can be used to produce heat energy to generate steam, drive gas

turbine and so on [21].

71

6.2.3 Working Principles (Gas Turbine)

Co-generation system or know as combined heat and power (CHP) system is basically

a system that produces electricity and heat at the same time. For the same power output, co-

generation system uses less fuel than traditional separate heat and power production, thus

making it useful for distribution of heat and electricity demand at the time.

There are two types of co-generation system, a topping cycle and also a bottoming

cycle. Topping cycle is mainly for the generation of the electricity or mechanical energy first

by using a fuel and then the remaining portion of the waste heat is then used in order to

produce useful thermal energy. The bottoming cycle produces heat first for manufacturing

process by using fuel combustion process. The remaining portion is then use for generation of

electricity. Generally, bottoming cycle is used for process-based industries, such as glass and

steel.

There are various types of co-generation system available, however most of the

popular alternatives is the gas turbine and also steam turbine. Gas turbine operates similar to

jet engines, with additional heat recovery system in order to capture the heat from the exhaust

of the turbine. Gas turbines are highly reliable and also has a wide range of power output

(500kW to 250MW). The working principal of the basic gas turbine is shown below.

Figure 8: Working principle of basic gas turbine

72

6.2.4 Working principles (Heat Recovery Steam Generator)

Heat recovery steam generator (HRSG) is a heat exchanger designed to recover the

exhaust waste heat from power generation plant prime movers, such as gas turbines or large

reciprocating engines, thus improving overall energy efficiencies. HRSGs can be used to

generate steam for district heating or factory processes, or to drive a steam turbine to generate

more electricity.

There are several types of HRSG, but the basic construction techniques are largely similar,

comprising banks of tubes mounted in the exhaust path. Exhaust gases at temperatures of

430º–650ºC heat these tubes, through which water is circulated. HRSGs mainly absorb heat

from the hot exhaust in the flue gases by convection heat transfer, but, in certain sections,

heat is transferred by both radiation and convection. The water is typically held at high

pressure to temperatures of around 200ºC, boiling to produce the steam.

HRSG design and construction

HRSGs typically comprise three sections:

1) Low pressure (LP)

2) Reheat/intermediate pressure (IP)

3) High pressure (HP)

This a triple pressure system, which maximizes plant thermal efficiency. Each section has a

steam drum and an evaporator section where water is converted to steam. The steam then

passes through superheaters to raise the temperature and pressure past the saturation point.

Diverter valves regulate inlet flows, allowing the gas turbine to continue to operate when

there is no steam demand, or if the HRSG needs to be taken offline.

Component in HRSG

Evaporator

This is where the heat from the gas turbine exhaust turns the water in the tubes into steam.

The evaporator is so important that it defines the overall HRSG configuration. Since the inlet

and outlet temperatures are both close to the saturation temperature for the system pressure,

the amount of heat that may be removed from the flue gas is limited.

73

Superheater

This dries the saturated steam from the steam drum perhaps only heated a little above

saturation point, but sometimes to a much higher temperature for extra energy storage. The

superheater is usually positioned in the hot gas stream before the evaporator. The type used

depends on the evaporator type.

Economizer

This preheats the feedwater, and it replaces steam removed via superheater or steam outlet,

and also because of water loss through blowdown. The economizer is conventionally fitted in

the path of the colder gas downstream of the evaporator. The type of economizer also

depends on the evaporator type, with configurations being typically similar to those of

superheaters.

Steam drum

The drum stores the steam generated in the water tubes and acts as a phase-separator for the

steam/water mixture.

Figure 9: Components of HRSG

74

6.2.5 Working Principle (Absorption Chiller)

In the last section, the chosen unit for the Refrigeration System is the Induced

Absorption Chiller. For this section, the overall working principle of the Absorption Chiller

will be explained.

Figure 10: Absorption Chiller

Similar to the compressor in an electric vapor compression cycle, the absorption

system uses its "thermal" compressor (consisting of the generator, absorber, pump and heat

exchanger) to boil water vapor (refrigerant) out of a lithium bromide/water solution and

compress the refrigerant vapor to a higher pressure. As the pressure of the refrigerant

increase, its condensing temperature also does too. In this high temperature and pressure, the

refrigerant vapour condenses into liquid. Since the temperature of refrigerant condensation is

higher than the ambient temperature, the heat flows out from the condenser and released to

the outside environment [7].

Then, the high pressure liquid flows through the throttling valve in which at this stage,

its pressure will be reduce and by reducing the fluid’s pressure, this will also cause the

boiling point of the fluid to drop. The reduced pressure fluid will then be passing through the

evaporator where it will be boiled at reduced temperature and pressure. Since the boiling

temperature is now lower than the conditioned air temperature, the heat will move from the

conditioned air stream to the evaporator hence causing it to boil [7].

75

Next, the vapour produced will pass through the absorber where it will return to liquid

state and then being pulled into the lithium bromide solution (absorption process). The

diluted lithium bromide solution will be pumped back to the generator. Since Lithium

bromide (absorbent agent) would not boil, the water is easily separated by applying a little bit

of heat. The resultant water vapour will pass through the condenser, absorbent solution

returns to the absorber and the cycle repeats [7]. Below is the diagram which describes

pictorially the process inside the absorption chiller.

Figure 11: Absorption Chiller process

76

6.2.6 Working Principle (Induced Draft Cross Flow Cooling Tower)

In the last section, the chosen unit for Heat Rejection System is the Induced Draft

Cross Flow Cooling Tower. For this section, the overall working principle of the Induced

Draft Cross Flow Cooling Tower will be explained.

Induced Draft Cross Flow Cooling Tower falls into the category of mechanical draft-

type cooling tower in which the air is being moved using fans. In Induced Draft Cross Flow

Cooling Tower, the water flows vertically through the fill while the air flows horizontally,

across the flow of the falling water.

Figure 12: Example of fill which being used in the cooling tower

Due to this, the air does not have to pass through the distribution system, allowing the

use of gravity flow hot water distribution basins mounted at the top of the unit above the fill.

These basins are universally applied on all crossflow towers [20]. Below is the example of the

Induced Draft Cross Flow Cooling Tower;

Figure 13: Induced Draft Cross Flow Cooling Tower

77

Typically, the fan setup for the Induced Draft Cross Flow Cooling Tower will be at

the top of the structure which draws air upwards against the downward flow of water passing

around the wooden decking or packing.

Figure 14: Fan being setup on top of the cooling tower

Since the airflow is counter to the water flow, the coolest water at the bottom is in contact

with the driest air while the warmest water at the top is in contact with the moist air, resulting

in increased heat transfer efficiency [12].

78

6.3 Peer evaluation of the selected concept

6.3.1 Zul’s evaluation

Muhammad Zulfaqqar Kasim

Fuel Supply & Pre-

Treatment Statement

Drying of Biomass

Drying of biomass system reduces the humidity in raw

biomass material which reduces the required heat to

combust. Hence, lower time will be needed to achieve

perfect combustion process. It also lowers the need of fuel

supply in co-combustion system.


Indirect Co-Firing

Gasification process in the indirect co-firing system enables

the production of fuel that is suitable for use in a gas turbine.

The produced fuel namely syngas, has high power to heat

ratio and more efficient than the direct combustion process of

the solid biomass since it can be combusted at higher

temperature. Conversion process of solid biomass to syngas

produces less waste emissions compared to direct

combustion of the solid biomass making it more



Gas Turbine

Gas turbines generally produce high power output and also

have higher efficiency and lower start up duration compared

to steam turbine. Additionally, the exhaust heat from the

turbine can be recovered using heat recovery system together

to produce useful thermal energy.


Vertical Heat Recovery

Steam Generator (HRSG)

Vertical HRSG generally has high steam production output

depending on the amount of exhaust heat recovered. Besides

that, vertical HRSG takes up less space which can be

practical in reducing the usage of space in a plant. Simpler

design of vertical HRSG could also mean less maintenance

cost.

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Refrigeration Cycle

System

Absorption Chiller

Useful steam generated from the heat recovery system is

used in absorption chiller to produce chilled water.

Comparing to other components of refrigeration cycle

system, absorption chiller produces less CO2 emission. This

is due to the process of the absorption chiller which used

steam instead of fuel to generate chilled water.


Induced Draft Cross

Flow Cooling Tower

Induced draft cross flow cooling tower takes up less space

and it is suitable for moderate-size plant. It also has a lower

operational and capital costs compared to other types of

cooling tower. Besides that, it has simpler design and highly

adaptable to different environment. It also capable in

reducing the recirculation effect in which will reduce the

efficiency of the heat rejection process.

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6.3.2 Adli’s evaluation

M. Amir Adli Nazarudin

Fuel Supply & Pre-Treatment System Drying of Biomass

• Reduction in total fuel costs by lowering the moisture content in biomass fuels.

• Improvement in combustion efficiency and ash emission.

• Integrating natural heating process and dryer which save in operating cost.

Co-combustion System Indirect Co-Firing

• Availability of fuel resource (e.g. woods) which could replace dependability on fossil fuels.

• Producing low calorific fuel gas that could power the gas turbines.

• No considerable impact on the boiler performance e.g. stability, availability and capacity.

Co-generation (CHP) System Gas Turbines

• Capable of producing large power output rated at >150 kW and great efficiency of > 30%.

• High initial investment for installation and commissioning but relatively low operating or maintenance costs (major overhaul every 3-4 years).

• Suitable for large industrial or commercial applications which require considerable amount of power.

Heat Recovery System Vertical Heat Recovery Steam Generators

• Vertical design requires less floor space in the power plant.

• Has smaller boiler volume and less probability of steam blockage in economizers during start-up.

Refrigeration Cycle System Absorption Chiller

• Saving in operating costs by avoiding peak electric demand charges and rates.

• Eliminate the use of CFC and HCFC refrigerants.

• Very high efficiency at 0.60 COP and 5.86 kW/ton for single effect absorption.

Heat Rejection System Induced-Draft Cross Flow Cooling Tower

• Equipped with axial fans to facilitate the flow of air into the unit.

• Used in smaller capacities, air flow horizontally while the water fall downward.

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6.3.2 Razin’s evaluation

RAZIN AKMAL B RUSLAN Fuel supply & pre treatment system Drying of biomass

This system help to remove the moisture and water content in the biomass material. By removing the mositure content it will improve the efficiency of the combustion system. Moisture will delay the combustion process and more energy needed to fully burnt the biomass. As dry biomass combustion more quicker and less energy neeeded.

Co-combustion system Indirect co-firing

Syngas is produce from the gasification of indirect co-firing. This output can be use to produce heat enerygy by combusting it. The advantage of the system that it has low emission of contaminant to environment.

Co-generation system Gas turbines

Gas turbine is choosen because this system is already establish and been used by many GDC plant. The benefits of gas turbine compare to steam turbine is the output is higher and also more efficient. In term of maintenance cost, the cost of maintenance gas turbines more cheaper. So it is more favourable.

Heat recovery system Vertical Heat recovery steam generator

Vertical HRSG have higher output compare to other system. In term of maintenance , it is easily repaired and the sizing area not consuming large space.

Refrigeration cycle system Absorption chiller

Eventhough the capital cost and operational cost of absorption chiller is high. The output capacity of the system is very high and it is enviromentally friendly.

Heat rejection system Induced draft cross flow cooling tower

Has simpler design. Consume medium space to built thus decrease construction cost. The capital and operational cost also lower compare to other type heat rejection system. Have average performanc and can be consider suitable for the plant system.

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6.3.4 Faez’s evaluation

Ku Muhammad Faez Ku Ariffin

Fuel Supply & Pre-

Treatment Statement

-Drying of Biomass

Drying of biomass system helps to reduce the humidity level

in biomass which eventually reduces the required heat to

combust. Thus, it will require lower time to achieve perfect

combustion process. It also lowers the fuel supply in co-

combustion system.


-Indirect Co-Firing

Gasification process in the indirect co-firing system enables

the production of fuel to be use in the gas turbine, which is

known as syngas. In addition, syngas has high ratio of power

to heat and has more efficient than direct combustion of the

solid biomass because it can be combusted at higher

temperature. Conversion process of solid biomass to syngas

has lesser byproduct of contaminants compared to direct

combustion of the solid biomass thus it has low emission of

contaminants to environment and makes it better than direct

combustion in term of environmental friendly.


-Gas Turbine

Gas turbine has wide range of power output and also higher

efficiency and lower start up duration compared to steam

turbine since it is using air to drive the turbine. Besides, the

exhaust heat from the turbine could be captured and

recovered using heat recovery system together to produce

useful thermal energy.


-Vertical Heat Recovery


Vertical HRSG has high output of steam produced,

depending the amount of exhaust heat enters. Besides that,

vertical HRSG has a medium size which is practical in

reduces the whole system capacity. It also has simple

maintenance compared to other types of HRSG and thus the

cost of maintenance can be minimized.

Refrigeration Cycle

System

-Absorption Chiller

Useful steam produce from the heat recovery system is used

to power up absorption chiller and generate chilled water.

Comparing to other components of refrigeration cycle

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system, absorption chiller is more environmental friendly in

term of CO2 emission. This is due to the process of the

absorption chiller is which using steam instead of fuel to

generate chilled water.


-Induced Draft Cross

Flow Cooling Tower

Induced draft cross flow cooling tower has medium size and

it is suitable for moderate-size plant, and also lower

operational and capital costs compared to other types of

cooling tower. In addition, its design is simpler and has high

adaptability for different environment. It also capable in

reducing the recirculation effect in which will reduce the

efficiency of the heat rejection process.

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6.3.5 Choong’s evaluation

Choong Weng Hong

Fuel Supply & Pre-

Treatment Statement

Drying of Biomass

Applying drying of biomass helps to reduce the moisture

content in biomass which eventually reduces the required

heat to combust. With this pre-treatment, the efficiency of

co-combustion system could be improved. It also lower the

investment cost in fuel supply in co combustion system.


Indirect Co-Firing

Syngas produced from indirect co-firing, which also known

as gasification, can be directly used in generating steam or

gas turbine or engines with heat recovery. Besides that,

syngas has high ratio of power to heat and is potentially more

efficient than direct combustion of the solid biomass because

it can be combusted at higher temperature. Conversion of

solid biomass to syngas using gasification has lesser

byproduct of contaminants such as flying ashes compared to

direct combustion of the solid biomass. Thus, gasification

has low emission of contaminants to environment and this

makes it better than direct combustion in term of



Gas Turbine

Gas turbine has higher efficiency and lower start up duration

compared to steam turbine since it is using air to drive the

turbine. It also has a wide range of power output. Moreover,

the heat exhaust from the turbine could be captured and

recovered using heat recovery system. Thus, the system

efficiency is improved.


Vertical Heat Recovery


Vertical HRSG has high output of steam depending on the

exhaust heat from co-generation system. Besides that,

vertical HRSG has a medium size which reduces the whole

system capacity. It also has simple maintenance compared to

horizontal HRSG and thus lower the cost of maintenance.

Refrigeration Cycle

System

Absorption Chiller

Steam produce from the heat recovery system is used to

power up absorption chiller and generate chilled water. By

comparing to others components of refrigeration cycle

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system in morphology chart, absorption chiller is more

environmental friendly in term of CO2 emission. This is

because absorption chiller is using steam instead of fuel to

generate chilled water.


Induced Draft Cross Flow

Cooling Tower

Induced draft cross flow cooling tower has medium size and

it is suitable for not very large plant such as biomass-based

GDC plant. It also has lower costs in operational and capital

compared to other types of cooling tower. Moreover, its

design is not complex and has high adaptability. Thus, it is

suitable for biomass-based GDC plant.

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7. Governing Equation

7.1 Gasification

If the syngas is used for direct burning, the gasification efficiency is defined as:

ƞ𝑡ℎ =�𝐻𝑔 × ṁ𝑔� + (ṁ𝑔 × 𝜌𝑔 × 𝐶𝑝 × 𝛥𝑇)

𝐻𝑔 × 𝑀𝑠× 100%

In which:

Ƞth = gasification efficiency (%)

Hg = heating value of the gas (kJ/m3)

ṁg = volume flow of gas (m3/s)

ρg = density of the gas (kg/m3)

Cp = specific heat of the gas (kJ/kg.ºC)

𝛥T = temperature difference between the gas at the burner inlet and the fuel entering the gasifier (ºC)

7.2 Closed-Cycle Gas Turbine

Data which refer to the operation of the gas turbine are useful to calculate the power output and total efficiency of the closed gas turbine (utilized in co-generation plant).

Compressor pressure ratio, γ Inlet temperature at each compressor side, oC Inlet temperature turbine, oC Lowest pressure in cycle, bar Isentropic efficiency of compressor, ηc Isentropic efficiency of turbine, ηT Pressure loss in boiler, % Pressure loss in intercooler, regenerator, % Pressure loss after cooler, % Effectiveness of regenerator, % Generator efficiency, ηg Mechanical efficiency, ηm Mass flow rate of gases in the cycle, �̇� *Combustion efficiency, ηcomb

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The temperature increase in the compressor is calculated by the following equation:

Δ𝑇𝑐 = 𝑇2 − 𝑇1 = 𝑇1𝜂𝑐

�𝛾�𝐶𝑝−1𝐶𝑝

��

where cp is the specific heat ratio of the flue gases based on temperature, oC.

The temperature increase in the turbine is given from the relation:

Δ𝑇𝑇 = 𝑇6 − 𝑇7 = 𝜂𝑇 × 𝑇6 �1 − 1

𝛾𝑇�𝐶𝑝−1𝐶𝑝

��

where γT is the turbine pressure ratio in terms of P6 / P7 and cp is the specific heat ratio of the flue gases based on temperature, oC.

The power output from the turbine is calculated from the equation as follows:

𝑃𝑒𝑙 = (𝑃𝑇 × 𝜂𝑚 − 𝑃𝐶)𝜂𝑔

𝑃𝑒𝑙 = ��̇�𝑐𝑝𝑇Δ𝑇𝑇𝜂𝑚 − 2�̇�𝑐𝑝𝑐Δ𝑇𝑐�𝜂𝑔

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The total efficiency of the closed-cycle gas turbine operation is calculated as:

𝜂𝑡𝑜𝑡𝑎𝑙 = 𝑃𝑢𝑠𝑒𝑓𝑢𝑙𝑃𝑓𝑢𝑒𝑙

= 𝑃𝑒𝑙

�̇�𝑐𝑝(𝑇6 − 𝑇5) 1𝜂𝑐𝑜𝑚𝑏

where T5 is calculated based on heat exchanger efficiency, ηHE as follows:

𝜂𝐻𝐸 = 𝑇5 − 𝑇4𝑇7 − 𝑇4

7.3 Absorption Chiller

Cooling capacity of the chiller load:

𝑄𝑐𝑜𝑜𝑙𝑖𝑛𝑔 = �̇�𝐶𝐻𝑊 × 𝐶𝑝 × (𝑇𝐶𝐻𝑊𝑅 − 𝑇𝐶𝐻𝑊𝑆)

where; �̇�𝐶𝐻𝑊 is the flow rate of the chilled water

TCHWR is the temperature of the chilled water entering the chiller

TCHWS is the temperature of the chiller water leaving the chiller

Cp is the specific heat of water

The heat delivered to the chiller by steam condensation is calculated from (the quantity can also be estimated from electrical power consumption in the steam boiler):

𝑄ℎ𝑒𝑎𝑡 = �̇�𝑠𝑡𝑒𝑎𝑛 × (ℎ𝑠𝑡𝑒𝑎𝑚 − ℎ𝑐𝑜𝑛𝑑𝑒𝑛𝑠𝑎𝑡𝑒)

where; �̇�𝑠𝑡𝑒𝑎𝑚 is the flow rate of the steam supply

hstean is the enthalpy of the steam supply (based on temperature)

hcondensate is the enthalpy of the condensate (based on temperature

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8. CONCLUSION

It has been a challenge to produce a cooling system that is excellent in terms of its

maintainability, cost efficiency, and energy efficiency. The existing individual cooling

system is neither that efficient in terms of energy efficiency nor in terms of cost efficiency.

Meanwhile, the current GDC system that utilizes natural gas is becoming too costly to run

due to ever increasing price of petroleum based fuel.

To tackle this issue, several objectives were set for this design project. Firstly, to

produce a Biomass-powered GDC design that has a better or comparable output compared to

conventional GDC. Secondly, to design a cost-efficient Biomass-powered GDC plant

throughout its service in terms of maintenance cost and also in terms of fuel cost. Lastly to

produce a cleaner Biomass-powered GDC by utilizing renewable alternative source of fuel.

The design project starts by selecting a datum to be the system and also performance

reference for the Biomass-GDC plant design. Next, the original system of the selected datum

was dissected (undergo decomposition) both physically and functionally to identify

thoroughly the subsystems in the referred datum, and also according to the requirements set

by the project question (A Biomass system to be included in the GDC system). After having

all the information of the basic system, a morphology chart was produced, in which all the

alternatives/means to obtain the desired output were listed down in a table. After that, several

concepts were generated from the alternatives given and justifications were made for each

and every concepts generated. Each and every member of the team will be having their own

concepts generated.

Later, all of these concepts were evaluated. However, the evaluation was done

through the breakdown of each concept’s subsystems. Objective trees for each subsystem

were created and from there, the weightage for every primary and design criteria were

assigned according to their importance. Then, after having all of the criterions sorted out, it

was then being evaluated using Weighted Decision Matrix (WDM). In this matrix, scores and

rating will be given to every concept’s individual subsystems. Later, the scores/ratings for all

the concept’s subsystems will be totalled up and the concept that yielded the highest sum will

be chosen as the main concept for the project. In the case for this project, the concept chosen

is Faez’s concept where the subsystems for his concepts are; drying of Biomass method for

Fuel Supply & Pre-Treatment system, Indirect co-firing for co-combustion system, Gas

90

turbines for Co-Generation system, Vertical Heat Recovery Steam Generator (HRSG) for

Heat Recovery system, Absorption chiller for Refrigeration Cycle System, and finally

Induced Draft Cross Flow Cooling Tower for the Heat Rejection System.

The entire overall and the chosen subsystems’ working principles, advantages and

strength of the selected concepts were also discussed in the previous part of the reports. Each

and every members of the group had also given their own feedback and comments regarding

the chosen concept. Finally, several related governing equations for subsystems were

identified and had also been included in the report as the preparation for the next stage of the

project. All in all, the current progress of the project is generally on track in achieving all the

objectives set for the project as the concept selected for this project is generally able to

produce output that is comparable to the normal GDC plant, a relatively cost efficient plant in

terms of fuel costs and maintenance and able to utilize biomass as the alternative fuel.

91

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Documents

MSD I - Final Group Report (Biomass-Powered Gas Disctrict Cooling Plant)