Performance Performance management of Boiler, management of Boiler,

Turbine , Cycle Turbine , Cycle Efficiency and other Efficiency and other

performance performance Parameters.Parameters.

Goal: To generate electricity from heat input!!!

Carnot Power CycleCarnot Power Cycle

Carnot Power CycleCarnot Power Cycle

Practical Problems Associated with A Practical Problems Associated with A Carnot Cycle Carnot Cycle

• Maximum temperature limitation for a cycle. • Quality of steam at later stages of expansion

in a turbine or engine.• Feasibility of Compression of wet steam.

The Rankine Cycle: An The Rankine Cycle: An Alternate Ideal Alternate Ideal

Thermodynamic Model Thermodynamic Model

Ideal Rankine CycleIdeal Rankine Cycle

How about a modified cycle - A Rankine How about a modified cycle - A Rankine cyclecycle

• To avoid transporting and compressing two-phase fluid, try to condense all fluid exiting from the turbine into saturated liquid before compressed it by a pump.

• when the saturated vapor enters the turbine, its temperature and pressure decrease and liquid droplets will form by condensation.

• These droplets can produce significant damages to the turbine blades due to corrosion and impact.

• One possible solution: superheating the vapor.

• It can also increase the thermal efficiency of the cycle.

Equivalent Carnot Model of Rankine Model

smin smax

Tm,out

Tm,in

REMARKS ON STEAM RANKINE CYCLEREMARKS ON STEAM RANKINE CYCLE

In fossil -power plants, an increase in thermodynamic In fossil -power plants, an increase in thermodynamic efficiency of 0.1% can be worth crores of rupees per year.efficiency of 0.1% can be worth crores of rupees per year.

There is a continued quest for higher efficiencies in thermal There is a continued quest for higher efficiencies in thermal power plants, which has resulted in some innovative power plants, which has resulted in some innovative modifications to the basic steam-power cycle .modifications to the basic steam-power cycle .

Among these, there is the regenerative cycle, where the Among these, there is the regenerative cycle, where the temperature oftemperature offeedwater is raised from that on leaving the condenser to the feedwater is raised from that on leaving the condenser to the final feedwater temperature using steam extracted from various final feedwater temperature using steam extracted from various stages of the turbines.stages of the turbines.

The determination of the optimal fraction of mass flow rate to The determination of the optimal fraction of mass flow rate to be extracted from each stage of the turbines is a complex be extracted from each stage of the turbines is a complex optimization problem.optimization problem.

In the regenerative cycle, a fraction of the steam that could In the regenerative cycle, a fraction of the steam that could have been used to produce work in the turbine is used to heat have been used to produce work in the turbine is used to heat the feedwater instead. There is a gain of efficiency by one side, the feedwater instead. There is a gain of efficiency by one side, there is loss by the other. there is loss by the other.

Efficiency in Power Efficiency in Power GenerationGeneration

• Efficiency = Output/ Input = (Input – losses)/ Input.

• Types of losses• Exit heat loss• Radiation loss• Condenser loss• Auxiliary power loss.

Efficiency in Power Efficiency in Power GenerationGeneration

How to minimise the losses?• Heat exchanger

• Insulation

• Vacuum

• Efficient auxiliaries and optimization.

Energy ConservationEnergy ConservationWhy?

• Mother earth has limited resources.

• Energy production leads to environmental degradation.

Energy ConservationEnergy ConservationHow?

• Changing attitude and practices.

• Creating awareness.

• Optimisation.

• Using energy efficient devices.

NEED NEED • Almost Rs. 4.00 Crore Per MW• Cost Savings• Resource Saving• Life of Plant

ConceptsConcepts• Cycle Efficiency is the efficiency of whole

cycle and can be improved by particular set of steam condition employed

• Turbine Efficiency is the efficiency of turbo alternator converting the available energy in the cycle into electrical energy.

• Boiler Efficiency is effectiveness of combustion and heat transfer

• Auxiliary Power efficiency depends on the ratio of Electricity sent out to Electricity Produced.

Requirement of BoilerRequirement of Boiler• Should be able to produce at required

parameters over• Compatible with feed water conditions

which changes with turbine loads• Capable of following changes in

demand for steam without excessive pressure swing

• Reliable

BOILER SYSTEMBOILER SYSTEM• Feed Water System

Makeup Water SystemCondensate System

• Steam System• Fuel System

DPNLSHTR

Platen S

HT

R

SCREEn

LTSH

ESPAPH

ID fan

Chimney

Economiser

Bottom Ash

Downcomer

Drum

waterwallFireball

Gooseneck

Reheater

Platen SH.

375C-425C

Final SH.

500-540C

Economizer

240-310C

LTSH

330-375C

Water Wall

310C

210 MW Boiler: Water and Steam Circuit

FOCUS FOCUS

• Assess Boiler Efficiency by Direct and Indirect Method

• Calculate and Optimize Boiler Blow Down

Identify and Implement energy efficiency measures

Direct MethodDirect MethodWhere energy gain of the working fluid

(Water & Steam) is compared with the energy content of the boiler fuel.

Heat OutputBoiler Efficiency= X 100 Heat Input

Q x ( hg – hf )

Boiler Efficiency (ή )= X100 q x GCV

Q : Qty of Stm generated in Kg/Hrq : Qty of Fuel Used in Kg/Hrhg: Enthalpy of Saturated Stm in KCal/Kg of

Stm hf: Enthalpy of Feed Water KCal/Kg of

WaterGCV: Gross calorific Value of Fuel in

Kcal/KG of Fuel

Advantages of Direct Advantages of Direct MethodMethod

• Evaluation is quick• Requires Few parameters for

Computation• Needs Few Instrument for

monitoring

Disadvantages of Direct Disadvantages of Direct MethodMethod

• No Clue to the operator

• Does not calculate various losses accountable for low efficiency

Indirect MethodIndirect Method• The efficiency is the difference

between the losses and the energy input.

• Loss Method• Boiler Efficiency (ή )= 100% - Losses

Types of LossesTypes of Losses• Loss of Heat due to Dry Flue gases• Loss of Heat due to Moisture in Fuel

and combustion air• Loss of Heat due to Combustion of

Hydrogen• Loss of Heat due to Radiation• Loss of Heat due to Unburnt

Data RequiredData Required• Ultimate Analysis of Fuel i.e. H2,

O2, S, C, Moisture & Ash Content• %age of O2 or CO2 in Flue Gas• Flue Gas Temperature• Ambient Temperature• Humidity of Air• GCV of Fuel• Percentage of Combustibles in ash• GCV of ash

Dry Flue gas LossesDry Flue gas Losses• Excess Air• Air Heater gas Outlet temperature

Air Heater gas Outlet Air Heater gas Outlet temperaturetemperature

• Lack of Soot Blowing• Deposits on Boiler Heat Transfer Surface• High Excess Air (Causes less heat

generation in Furnace and more in SH)• Higher Elevation burners in service at

low load• Defective baffles and bypass dampers,

causing gas short circuiting• Improper Combustion• Poor Milling Plant Performance• Air recirculation

Wet Flue Gas LossWet Flue Gas Loss• Moisture in Fuel• Moisture in Combustion• Moisture in Air

Carbon in Ash LossCarbon in Ash Loss• High Carbon in Ash• Low Carbon in Ash

High Carbon in AshHigh Carbon in Ash• Coarse Grinding• Mal adjustment of flame• Unequal loading of different Mills• Incorrect PA air temperature

Low Carbon in AshLow Carbon in Ash• Exhauster speed too low• Mill Adjustment • Rich Fuel / Air Mixture• Separator ( Classifier) speed too high

Boiler Blow DownBoiler Blow Down• Lower Pretreatment Cost• Less make up water consumption• Reduce maintenance downtime• Increased Boiler life• Lower consumption of treatment

chemicals

Feed Water TDS x % Make up waterBlow Down(%)= Max. Permissible TDS in Boiler Water

TDS: Total Dissolved Solids

Blow Down Rate = Boiler Evaporation rate X Blow

Down(%)

BLOW DOWN CALCULATION

Energy Efficiency Energy Efficiency OpportunityOpportunity

• Stack Temperature• Feed Water Preheating using

Economiser• Combustion Air Preheat• Incomplete Combustion• Excess Air Control• Radiation and Convection Heat

Losses

Energy Efficiency Opportunity Energy Efficiency Opportunity

…….Contd.…….Contd.

• Reduction in Scaling and Soot Losses• VFDs for Fans, Blowers and Pumps• Proper Boiler Scheduling• Milling plant performance• ESP performance

SIMPLE RANKINE CYCLE

• LOW INITIAL COST

• LOW CYCLE EFFICIENCY

• HIGH MOISTURE AT TURBINE OUTLET

• LIMITATION ON MAXIMUM PRESSURE

• LIMITATION ON CONDENSER PRESSURE

MODIFIED RANKINE CYCLE

• HIGHER CYCLE EFFICIENCY

• LOW MOISTURE AT TURBINE OUTLET

(LP TURBINE DESIGN EASIER)

• NO LIMITATION ON MAXIMUM PRESSURE

• NO LIMITATION ON CONDENSER PRESSURE

• HIGHER INITIAL COST

HEAT GAIN IN THE BOILER

BFP

FOR 500 MW UNITS (SUB CRITICAL UNITS)

• INITIAL STEAM PR- 170 Kg/Sq. CM (abs.)

• INITIAL STEAM TEMPERATURE - 537 Deg C

• REHEAT STEAM TEMPERATURE - 537 Deg C

FOR 200 MW UNITS

• INITIAL STEAM PR- 150 Kg/Sq. CM (abs.)

• INITIAL STEAM TEMPERATURE - 537 Deg C

• REHEAT STEAM TEMPERATURE - 537 Deg C

FOR 660 MW UNITS (SUPER CRITICAL UNITS)

• INITIAL STEAM PR- 246 Kg/Sq. CM (abs.)

• INITIAL STEAM TEMPERATURE - 537 Deg C

• REHEAT STEAM TEMPERATURE - 565 Deg C

• IMPULSE TURBINES

• REACTION TURBINES

Turbine EfficiencyTurbine Efficiency output KwhEfficiency = = Input Input 1 Kwh = 3600 K J output Efficiency = x 100 % Heat Input

Turbine EfficiencyTurbine Efficiency …… Contd. …… Contd.

Heat rate:210MW LMW Turbine= 2040 K Cal/kWhή = 42.15%500 MW = 7940 K Cal/kWhή = 45.3%

Degree of Reaction (R) Enthalpy Drop in Moving Blade R= Enthalpy Drop in Stages

Factors Affecting Factors Affecting OperationOperation

Effect of LoadThrottle GoverningNozzle GoverningOverload (By Pass) Governing

Terminal ConditionsEffects of VacuumEffects of MS and RH TemperatureEffects of MS and RH PressurePressure Drop through Reheaters

Effect of Heater EfficiencyGland WearFeed Pump Power

Turbine LossesTurbine LossesInternal

Friction in Nozzle, Blades & Disc Diaphragm gland and blade tip

leakage Partial Admission Wetness Exhaust

External Shaft Gland Leakage Journal and Thrust Bearing Governor and Oil Pump

Condenser PerformanceCondenser Performance

• Back Pressure» CW Pumping Power»Leaving Loss»Reduced Condensed

Temperature/ Increased Blade steam

»Wetness of Steam

Energy Saving Opportunities in Energy Saving Opportunities in Steam SystemSteam System

• Monitoring Steam Traps• Avoiding Steam Leakages• Providing Dry Steam for Processes• Utilising Steam at the lowest

Acceptable Pressure for the process• Proper Utilisation of Directly Injected

Steam

Energy Saving Opportunities in Energy Saving Opportunities in Steam SystemSteam System ……. ……. ContdContd

• Minimizing Heat Transfer Barriers• Proper Air Venting• Condensate Recovery

» Financial Reasons» Effluent Restriction» Maximizing Boiler output» Boiler Feed Quality

• Insulation of Steam Pipelines and Hot Process Equipments

• Flash Steam Recovery

Control & InstrumentationControl & Instrumentation• Data Acquisition System

• Distributed Digital Control Monitoring Information System

FunctionsFunctions• Data Acquisitions• Data Monitoring and Status

Reporting• Alarm Monitoring & Status Reporting• SOE Recording• Mimics and Guidance's• Long Term data storage Retrieval

and Statistical Analysis

FunctionsFunctions …….. Contd. …….. Contd.

• Better Human Machine Interface• Online Performance Monitoring• Report Generation• Pre and Post Trip Analysis

Factors for Unit Factors for Unit PerformancePerformance

• Planned maintenance loss• Thermal Efficiency factors• Plant Load Factor• Forced Outages• Plant Availability Factor

• Availability and Efficiency has a direct relationship

• Higher availability leads to higher efficiency

• Efficient Unit leads to better availability due to better combustion control conditions, better fluid dynamic condition and better heat transfer condition

ConclusionConclusion• Performance

Improvement

• Effective Capacity Utilisation

• Investment Cost• Lower Cost of

Generation

• Efficiency Improvement

• Lower Cost of Generation

• Saving in Resources

• Increased Life of Plant

INDIAN POWER SECTORINDIAN POWER SECTORCOAL : 69450GAS : 13582OIL : 1202HYDRO: 34110NUCLEAR: 3900RENEWABLE 6191TOTAL 128435

COST IMPLICATIONCOST IMPLICATION

•69450* 0.73= 50698.5 MW•18751.5 MW•Rs. 75006 Crore

ClassificationClassification

• Impulse

• Impulse – Reaction

• Simple Impulse• Velocity Compounded • Pressure

Compounded• Pressure- Velocity

Compounded

NOZZLENOZZLE• All turbine have nozzles in which the

pressure of the steam is reduced and the velocity increased.

• In Impulse Turbine the nozzles are stationary which is stationary Blade.

• In Impulse-Reaction turbine both the fixed and moving blades are nozzles.