PERFORMANCE ASSESSMENT OF BOILERS,STEAM

SYSTEM,INSULATION & REFRACTORIES

What is a Boiler ?

Vessel that heats water to become hot water or steam. At atmospheric pressure water volume increases 1,600

times. Hot water or steam used to transfer heat to a process.

PERFORMANCE ASSESSMENT OF BOILERS

TYPES OF BOILERS

Water Tube Boiler Packaged Boiler Fluidized Bed (FBC) Boiler Fire Tube Boiler Stoker Fired Boiler Pulverized Fuel Boiler Waste Heat Boiler

FIRE TUBE BOILER

Relatively small steam capacities (12,000 kg/hour)

Low to medium steam pressures (18 kg/cm2)

Operates with oil, gas or solid fuels

ASSESSMENT OF A BOILER

Boiler Efficiency :Thermal efficiency: % of (heat) energy input that is

effectively useful in the generated steam.

The energy gain of theworking fluid (water and steam) is compared with the energy content of the boiler fuel

The efficiency is the different between lossesand energy input

BOILER EFFICIENCY : DIRECT METHOD

Boiler efficiency () = Heat Input

Heat Outputx 100 =

Q x (hg – hf)

Q x GCVx 100

hg -the enthalpy of saturated steam in kcal/kg of steam hf -the enthalpy of feed water in kcal/kg of water

Parameters to be monitored: - Quantity of steam generated per hour (Q) in kg/hr - Quantity of fuel used per hour (q) in kg/hr- The working pressure (in kg/cm2(g)) and superheat

temperature (oC), if any - The temperature of feed water (oC) - Type of fuel and gross calorific value of the fuel (GCV)

in kcal/kg of fuel

BOILER EFFICIENCY : INDIRECT METHODEfficiency of boiler () = 100 – (i+ii+iii+iv+v+vi+vii)

Principle losses:

i. Dry flue gas

ii. Evaporation of water formed due to H2 in fuel

iii. Evaporation of moisture in fuel

iv. Moisture present in combustion air

v. Unburnt fuel in fly ash

vi. Unburnt fuel in bottom ash

vii. Radiation and other unaccounted losses

Contd…..Required calculation data

• Ultimate analysis of fuel (H2, O2, S, C, moisture content, ash content)

• % oxygen or CO2 in the flue gas

• Fuel gas temperature in ◦C (Tf)

• Ambient temperature in ◦C (Ta) and humidity of air in kg/kg of dry air

• GCV of fuel in kcal/kg

• % combustible in ash (in case of solid fuels)

• GCV of ash in kcal/kg (in case of solid fuels)

PERFORMANCE ASSESSMENT OF INSULATION

What is Insulation?

Insulation, or more correctly thermal insulation , is a general term used to describe products that reduce heat loss or heat gain by providing a barrier between areas that are significantly different in temperature.

It make your home warmer in winter and also helps keep it cooler in summer.

Air is a poor conductor of heat, so the tiny pockets of air trapped in insulation minimise the amount of heat which can pass between the inside and outside of your house.

HOW INSULATION WORKS?

Building insulation refers broadly to any object in a building used as insulation for any purpose.While the majority of insulation in buildings is for (1)thermal purposes, the term also applies to  (2) acoustic insulation, (3) fire insulation, and (4)impact insulation.

Thermal insulation can refer to material used to reduce the rate of heat transfer or the methods and processes used to reduce heat transfer.

Heat or thermal conduction is the spontaneous transfer of thermal energy through matter to equalize temperature differences. It is also described as heat energy transferred from one material to another by direct contact.

DIFFERENT KINDS OF MATERIAL USED IN INSULATION

The different materials used in the Insulation process are:

Glass mineral wool (glasswool) Rock mineral wool (stone mineral wool) Rigid foam Sheep wool

TYPES OF INSULATION

Structural Insulated Panel Sprayed Foam Concrete Blanket batts and roll Foam board Loose fill-in and blow-in Reflective Fibre Insulation

STRUCTURAL INSULATED PANEL

Structural insulated panels (SIPs), also called stressed-skin walls, use the same concept as in foam-core external doors, but extend the concept to the entire house. They can be used for ceilings, floors, walls, and roofs.

The panels usually consist of plywood, OSB, sandwiched around a core of expanded polystyrene, polyurethane, polyisocyanurate, compressed wheat straw, or epoxy.

Insulated Concrete Forms

ICFs are hollow, light-weight "stay in place" forms made of two Expanded Polystyrene (EPS) panels which are connected by polypropylene webs. During construction, the forms are stacked to the desired height then filled with concrete making stable, durable and sustainable walls. 

Oriented strand board, (OSB) or Sterling board (UK), is an engineered wood product formed by layering strands (flakes) of wood in specific orientations

Loose FillCellulose is 100% natural and 75-85% of it is made from

recycled newsprint.

a. Fibrous Type – from mineral wool rock, glass wool, slag wool or vegetable fiber usually of wood fiber.

b. Granular Insulation from expanded minerals like perlite, vermiculite or ground vegetable matter.

Sound Insulation (Soundproofing)

is any means of reducing the intensity of sound with respect to a specified source and receptor.

Soundproofing affects sound in two different ways: 

noise reduction and noise absorption.

PERFORMANCE ASSESSMENT OF STEAM SYSTEM

What is steam? Molecule: smallest of any compound Water = H2O

◦ two hydrogen atoms (H)◦ one oxygen atom (O)

Three physical states :◦ solid: ice◦ liquid: water◦ vapour: steam

Why do we use steam?

Transport and provision of energy Benefits:

• Efficient and economic to generate• Easy to distribute• Easy to control• Easily transferred to the process• Steam plant easy to manage• Flexible

Steam saturation curve:

Typical steam circuit

MOST IMPORTANT COMPONENTS

1. Pipes2. Drain points3. Branch lines4. Strainers5. Filters6. Separators7. Steam traps8. Air vents9. Condensate recovery

system10. Insulation

Pipe material: carbon steel or copperCorrect pipeline sizing is importantSize calculation: pressure drop or velocity

Ensures that condensate can reach steam trap Consideration must be give to

• Design• Location• Distance between drain points• Diameter of drain pipe

PIPES:

DRAIN POINTS:

BRANCH LINES:Take steam away from steam main

Shorter than steam mains

Pressure drop no problem if branch line < 10 m

STRAINERS:

Y-Type strainers Handles high pressures Lower dirt holding

capacity: more cleaning needed

FILTERS Consists of sintered stainless steel filter element Remove smallest particles

– Direct steam injection – e.g. food industry– Dirty stream may cause product rejection – e.g. paper machines– Minimal particle emission required from steam humidifiers– Reduction of steam water content

SEPARATOR Separators remove suspended water droplets from steam Water in steam causes problemso Water is barrier to heat transfero Erosion of valve seals and fittings and corrosion

STEAM TRAPSSelection depends on steam trap’s ability tooVent air at start-upoRemove condensate but not steamoMaximize plant performance: dry steam

AIR VENTS : Effect of air on heat transfer

CONDENSATE RECOVERY SYSTEM What is condensate

– Distilled water with heat content– Discharged from steam plant and equipment through steam

traps Condensate recovery for

– Reuse in boiler feed tank, desecrator or as hot process water– Heat recovery through heat exchanger

INSULATION Insulator: low thermal conductor that keeps heat confined within or outside a system Benefits:

Reduced fuel consumption Better process control Corrosion prevention Fire protection of equipment

PERFORMANCE ASSESSMENT OF REFRACTORIES

What are the refractories? Any material can be described as a refractory, if it can

withstand the action of abrasive corrosive solids, liquids or gases at high temperature.

A good refractory lining inside a furnace can help life of a blast furnace from 4-5 yrs or 10-15 yr.

Classification

Refractories can be classified-on the basis of chemical composition-method of manufacture-according to their refractoriness.

Acidic refractories

These are used in areas where slag and atmosphere are acidic.

They are stable to acids but attacked by alkalis.

e.g. fire clay, silica, Quartz, Zirconia. Basic refractories

These are used on areas where slags and atmosphere are basic, stable to alkaline materials but reacts with acids.

e.g. Magnesia , Alumina, Dolomite.

On the basis of chemical composition

• Neutral refractoriesThese are used in areas where the atmosphere is either acidic or basic and are chemically stable to both acids and bases.e.g. Chromate, Carbide, Mullite.

Based on refractoriness

Low heat duty refractories

For low temperature environment i.e. 1520 —1630 ºC Medium heat duty refractories

For temperature ranging from 1630—1670 ºC High heat duty refractories

For temperature ranging from 1670—1730 ºC Super duty refractories

For temperature above 1730 ºC

Transportation of Raw material Grinding Pre-Treatment

Calcination

Stabilizer addition Mixing

Bonding material

Wet Mixing (14-20% water)

Semi plastic

Dry Mixing ( < 5% water) Moulding

Hand Moulding (Wet Mixed)

Machine Moulding (Dry and Semi wet Mixed) Drying

Avoids high shrinkage and gives strength.

Make refractories safe for handling. Firing

Removes water of Hydration,

30% Shrinkage in Volume

MANUFACTURING STEPS

SELECTION OF REFRACTORIES Area of application Working temperatures Extent of abrasion and impact Stress due to temperature gradient Heat transfer and fuel conservation Cost considerationAPPLICATIONSRefractories are meant to sustain at high temperature sothe very common applications are Used in furnaces such as blast furnace and coke oven. Used in boilers. Mostly used in cement industry in Preheater Rotary Kiln Burner pipe