25-Questions & Answers on AFBC Boilers

 

1-What do you mean by AFBC Boiler?

Atmospheric Fluidized Bed Combustion (AFBC) boilers are those, which have the potential to use alternative fuel sources such as coal, wood, or waste or any other low grade fuel, and are able to reduce and control nitrogen oxide (NOx) and sulphur dioxide (SO2) emissions.

2-List down the advantages of FBC boilers over other boilers?

  •          FBC boilers have higher combustion efficiency.
  •          Any low grade fuel can be burnt in FBC Boilers
  •          Boiler size is compact as compared to travelling grate & pulverized boilers.
  •          Different variety of fuels can be burnt
  •          Very high ash content fuel can be burnt
  •          Over & under feed fuel feeding system availability
  •          Higher turn down ratio

3-Briefly explain the process of fluidisation?

When an evenly distributed air or gas is passed upward through a finely divided bed of solid particles such as sand supported on a fine mesh, the particles are undisturbed at low velocity. As air velocity is gradually increased, a stage is reached when the individual particles are suspended in the air stream – the bed is called “fluidized.” With further increase in air velocity, there is bubble formation, vigorous turbulence, rapid mixing and formation of dense defined bed surface. The bed of solid particles exhibits the properties of a boiling liquid and assumes the appearance of a fluid “bubbling fluidized bed” desirable for good heat transfer and intimate contact. If sand particles in a fluidized state is heated to the ignition temperatures of coal, and coal is injected continuously into the bed, the coal will burn rapidly and bed attains a uniform temperature. The fluidized bed combustion (FBC) takes place at about 840 °C to 950 °C.

4-Explain the different types of Fluidization in FBC boilers

Boiler Gauge Glass Line Up Procedure

Fluidization: At low velocity air flows through the porosity of bed. Once the velocity of air increases, the air starts moving in a turbulent state & causes particles of bed to attain turbulence along with the air. Here bed materials move like fluid, so called Fluidization.

Different types of fluidization are:

When gas flow introduced through the bottom of the bed of solid particles, it moves upward through the bed via the empty spaces between the particles.

During low air velocity bed remains under stable fixed state, this condition is called Pseudo Fluidization

Minimum Fluidization:

At higher air velocity, the aerodynamic drag forces begins to counteract the gravitational forces causing the bed to expand in volume as the particles move away from each other. Further increasing the air velocity, it reaches the critical value at which upward drag forces exactly equal to the gravitational forces causing particles to remain in suspended within the fluid, this is called minimum fluidization.

Maximum fluidization or bubbling fluidization:

Further increasing the air velocity, the bulk density of the bed continues to decrease and its fluidization becomes more violent, until the particles no longer form a bed and are conveyed upwards by the gas flow. This is called bubbling fluidization.

Questions & Answers on Boiler Troubleshooting

5-What the bed plate is consisting of?

Bed plate is the partition plate between wind box & furnace. It consists of Bed nozzle, coal feed nozzle & ash drain pipes. Generally bed plates are made up of stainless steel materials.

6-What are the different types of nozzles used in AFBC Boilers

Fluidizing nozzles:

These are the stainless steel or alloy steel nozzles fitted on bed plate. It has 2 to 5mm holes around it, through which FD air enters rom wind box to furnace. It is manufactured by machining a solid SS/alloy steel bars.

Coal feeding Nozzles:

Coal with primary air enters into the furnace through these nozzles.4 to 6 nozzles or depending on Boiler capacity are fitted in each compartments. Coal feeding nozzles are fitted in bed plate to distribute coal uniformly

7-What is the function of Ash drain pipes?

Generally Ash drain pipes are fitted in bed plates & extended outside. These are terminated to bed ash cooler where ash is getting cooled by air before discharges through ash conveying system.

How to convert air /gas flow from M3/hr to Nm3/hr or Sm3/hr??

What do you mean by IBE & IBSH in FBC Boilers?

IBE: In Bed Evaporating Coils

In some FBC Boilers, complete furnace is covered with evaporator coils. Coils are generally fitted in 2 nos inner & outer. To prevent erosion due to fluidizing materials, coils are covered with refractory materials.

IBSH: In bed Super heater coils

One SH coil is placed inside the bed, it is just placed right angle of IB coil & generally installed from last compartment & extended up to second compartment. To get rated main steam temperature at lower loads, sometime these are installed in 1st compartment also.

Why & How these in Boilers??

8-What do you mean by DP test in AFBC Boilers?

It is the test carried out before the light up of Boiler to ensure the healthiness of air nozzle & bed plate.

9-Write down the potential reasons to carryout DP test

To check the condition of air nozzles that is to identify the nozzles are clean, choke free & correct hole size

  • To identify the leakages in bed plate
  • To check the maximum FD air flow for each compartment
  • To identify air leakages in APH
  • To check problems associated with each compartment

10-Briefly explain the procedure of DP test

DP test is done on clean bed

Pre-checks

  • Ensure bed is clean
  • Ensure all maintenance works of air nozzles, bed etc are completed
  • Ensure FD fans are healthy & can be run at its full flow capacity (Air flow is allowed in each compartment from 25% to 100% of its capacity)

Procedure:

  • Start ID fan & then FD fan at minimum RPM initially
  • Take APH in line
  • Increase air flow gradually from 25% to 100%
  • Note down wind box pressure at each stage
  • Repeat this procedure for remaining all compartments
  • The wind box pressure values should match commissioning or design values
  • Now take all the compartments together & increase FD air flow up to 100% & again check wind box pressure & FD fan discharge pressure

Interpretation

  • If the DP test results (wind box pressure) are 10 mmwc more or less than commissioning values, nozzles& bed plates are said to be in good condition
  • If result data shows higher value, then nozzles are blocked
  • If the results show less value, then nozzles or damaged or holes are enlarged
  • Higher pressure drop in APH indicates tubes leakage

11-What is the fluidization air velocity in AFBC Boilers?

It is around to 1.5 to 3.7 m/sec

12-What do you mean by Elutriation in AFBC Boilers?

Process of separation & escaping of fine bed materials with the air during fluidsation is called Elutriation.

13-What do you mean bed level?

It is the height of the bed above the bed plate

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14-How do you calculate the Bed level?

Bed level = wind box pressure-DP across the bed nozzles

What is the function of Over Fire Air (OFA) in AFBC Boilers?

OFA is given at height around 5 to 8 meter above the bed to achieve complete combustion

15-What is the standard size of Bed materials used in AFBC Boilers?

Bed material is Crushed refractory of size around 0.85 to 2.36 mm & having fusion temperature > 1300 Deg Cdf

16-What is the density of refractory material?

It is around 1100 kg/m3

17-What are the standard compositions of Bed materials?

Sl No.

Chemicals Compositions

Limits

1

SiO2

55-60

2

Al2O3 37-40 , Min 30% required

37-40 , Min 30% required

3

FeO

<2.0

4

TiO2

1.67

5

MnO

Small traces

6

CaO

0.54

7

MgO

0.23

8

P2O5

0.08

9

Na2O + K2O

< 3.0

 Questions & Answers on Spent wash fired Boilers

18-What are the startup fuels used for AFBC boiler light up?Write down the procedure for AFBC boiler start up

Charcoal & Light Diesel Oil (LDO) are used as start fuels for AFBC boiler light up

Light up & Start up procedures

  • Before filling bed material into the furnace FD air nozzles must be cleaned by admitting maximum FD air into the furnace by opening FD air compartmental damper (PA air damper remaining closed) for 10–15 minutes.
  • Fill bed material into the furnace so that bed height should be about 250–300 mm above air nozzles or 280–300 above the distribution plate.
  • The bed material below the air nozzles remains static all the time and should be counted as bed height.
  • Spread the bed material uniformly by admitting sufficient fluidized air through the bed and bed height can now be measured physically after putting off air. During fluidizing PA dampers should remain closed.
  • After uniform spreading of bed material and maintaining required bed height start the startup compartment by varying the air flow gradually so that bed material begins to fluidize.
  • Slowly increase the air flow so that small bubble formation takes place over the bed material and incoming air escape the bed as small bubbles. Note down the air flow at the stage known as bubbling stage.
  • Again increase the air flow so that the bed become turbulent and complete mixing of top and bottom layer of bed material take place. Note down the air flow at this stage. This is the amount of air required fir mixing during start up.
  • Now stop the fans and boiler can be taken for startup.
  • Maintain the drum level about 40%.
  • Drum vent, super heater vent, startup vent and main steam line drain should be kept open.
  • Desired quantity of dry charcoal is to be spreaded uniformly over the bed in the start up compartment. Generally 1 to 3% of bed material
  • Desired quality of Diesel mixed charcoal is spreaded over the dry charcoal. Generally Diesel must be 10-15% of total charcoal. Out of total charcoal 70-75% should be dry & spreaded at the bottom & 25-30% should be wet & spreaded over top of dry charcoal
  • Initiate the fire using diesel soaked cotton. Ensure fire is spreaded uniformly
  • After some times start ID, FD & PA fans as per sequence and open their discharge dampers then suction damper. Keep at minimum RPM if there is VFD if not then control the flow by discharge & suction dampers.
  • Maintain PA header pressure up to 500 MMWC initially
  • Now check physically and ensure when the flame is in bluish condition mixing should be done with mixing air flow for 10–15 second
  • Now bed temperature will start rising and after getting bed temperature up to 450 Deg C start the coal feeding by increasing PA header pressure up to 900-1000 mmwc
  • Now slowly increase fuel feeding & FD air
  • Close drum air vent at 2.5 kg/cm2.
  • Close super heater drain at 20 kg/cm2 pressure and open start up vent control valve.
  • Open MSSV (main steam stop valve) after the prior and proper charging through equalizer valve (MS bypass valve).
  • In order to increase the load on Boilers take 2nd, 3rd etc compartments as per requirement

19-What is the size & GCV of Charcoal used for light up

Charcoal size is around 15 to 25mm & GCV is around d 6500 to 7000 Kcal/kg

20-What are the important parameters in AFBC boilers?

  • Fuel size
  • Bed material size and specification
  • Bed height and FD air pressure
  • Bed temperature and furnace temperature

21-What action you will take if bed temperature increases?

  • Increase bed material
  • Reduce load
  • Control the bulk density of fuel

22-What are the reasons for drop in bed temperature?

Poor quality of bed material

Sudden reduction of boiler load

Moisture in fuel

More excess air

23-Why do you add Lime in AFBC boilers?

Lime is added to absorb the moisture from coal

24-Explain the process of sulphur dioxide absorption by lime

Lime stone (CaCo3) on heating gets converted to slaked lime

CaCo3 + Heat = Cao + Co2

Sulphur on heating gets converted into Sulphur di-oxide

S + O2 = SO2

Slaked lime reacts with Sulphur dioxide & converts into Calcium sulphur

Cao + SO2 + ½ O2 = CaSO4

25-How do you decide the quantity of sulphur required for desulphurization of coal?

Around 3.3 kg of lime is required for 1 kg of sulphur in coal or 2 kg of sulphur dioxide

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Procedure for Boiler Gauge glass line up & Flushing

Boiler Gauge glass: is a transparent glass of shape tubular, flat or square blocks fitted to the boiler steam drum to facilitate a visual indication of the water level of a steam drum. These types of glasses are manufactured by borosilicate glass which is robust, temperature & chemical resistant.

 



Line up of Gauge glass:

  • Ensure all tools & required PPEs are taken to operate the valves (Hand gloves, Safety goggles, “F” rods etc)
  • Ensure steam & water side valve of gauge glass are healthy & operating properly
  • Ensure there are no any leakages
  • Ensure steam side & water side valves are closed
  • Ensure gauge glass drain valve is open & drain is connected/extended to safe location
  • Now crack open the steam valve & check for any leakages in gauge glass. Wait for some times until system heats uniformly.
  • Then crack open the water side valve, wait for some time for stabilization
  • Then close the drain valve
  • Open the steam valve & water valve fully
  • Observe water collected in glass & showing the level
  • Cross check the level glass with other side level glass or control room transmitter reading or with Hydra step

Factors considered for Boiler Engineering

Flushing of gauge glass

Ensure all tools & required PPEs are taken to operate the valves (Hand gloves, Safety goggles, “F” rods etc)

Step-I

  • Close the water side valve & open the drain valve for flushing, wait for some time
  • Then close the drain valve & open the water side valve

Note: After opening the water side valve, water level should retain its normal operating level, if not then there might be blockages in valve or line

Step-II

  • Close the steam side valve & open the drain valve for flushing, wait for some time
  • Then close the drain valve & open the steam side valve

Note: After opening the steam side valve, water level should retain its normal operating level, if not then there might be blockages in valve or line

Questions & Answers on AFBC Boiler





10-tips to reduce LOI/unburnt in Boilers

 

 1-Optimization of fuel moisture in the fuel:

Higher moisture in the fuel leads to unbalanced draft in the furnace or combustion chamber. Which ultimately results into poor mixture of air & fuel, higher moisture fuel demands more excess air. So optimization of fuel moisture will help to reduction in LOI.

2-Maintaining balanced draft in furnace:

Unbalanced draft is nothing but more FD air/less ID draft or less FD air /More ID Draft.

More FD & less ID causes back fire & improper mixing of air & fuel.

More ID & less FD causes escape of fuel particles from furnace without proper combustion

3-Maintaining 3Ts of combustion:

3Ts of combustions are: Temperature, Time & Turbulence

Temperature: For proper combustion temperature of the furnace must be sufficient enough to burn the fuel completely.

Time: There must be sufficient time for combustion

Turbulence: There should be proper turbulence in furnace for proper mixing of air & fuel

4-Increasing the secondary air quantity & pressure:

This will help to increase the residence time of fuel in furnace resulting into complete combustion

5-Maintaining the required excess air:

Lesser excess air than required will lead to incomplete combustion that is conversion of carbon into carbon monoxide instead of carbon di-oxide. So sufficient air is required to achieve complete combustion.

6-Using correct or designed GCV of a fuel:

Lesser GCV fuel requires more air for combustion, even may not achieve the designed parameters of Boilers like flow, pressure & temperature.

7-Ultimate & Proximate analysis of fuel:

In order to achieve proper combustion, we must know the contents of fuel properly. Need to operate the Boilers at designed parameters of fuel. For example if FC of the fuel increases, then need to increase air & combustion time and need to reduce turbulence.

So it is very important to know the fuel contents.

8-Operating the Boilers at stable loads:

Stable loaded Boilers will not lead into much LOI, as air & fuel mixture is constant & will not vary frequently. LOI cannot be reduced in variable load boilers.

9-Operating the Boiler at little positive draught:

Operation of Boiler at positive draught will help for complete combustion. If boiler is operated at more negative draught, then there will be more chances of escaping of unburnt fuel particles from the furnace & causing secondary combustion at super heaters & other convective zones.

10-Reusing unburnt or cinder:

Generally unburnt/cinder from Boiler Bank & economiser zones are re-injected into furnace by using “Cinder re-injection” system. This will help in re-burning of cinder & reduction in LOI

 Procedure for Boiler Gauge glass line up

 

Viva Questions & answers for preparation of BOE exam & interview


 

 

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16-Perfect reasons for more fuel consumption of Boilers

Following are the 16-reasons for increase in Boilers fuel consumption

1. Decreased economiser inlet feed water temperature:

On every 6-8 deg C decrease in Economiser inlet feed water temperature causes the rise in Boiler fuel consumption by 1%.

2. Increased Boiler outlet  flue gas  temperature:

On every 22 deg C increase in flue gas temperature causes the reduction in Boiler efficiency by 1% & hence boiler fuel consumption increases for generating same steam.

3. Increased moisture content in the fuel

Boilers fuel consumption increases as the moisture in the fuel increases. As it requires more excess air & reduces combustion efficiency leading to unburnt losses

4. Increased excess air

10-Tips to reduce LOI in Boilers

Increase in excess air causes dry flue gas loss & hence more fuel consumption. And also leads to more auxiliary power consumption.

5. Increased unburnt loss

Unburnt fuel or incomplete combustion of fuel leads to increased consumption of fuel. Unburnt is due to improper air fuel mixture or unbalanced draught or variation in the fuel quality

6. Higher blow down

Blow down water carries saturated water/steam through it, so leads into more fuel consumption. Maximum acceptable blow down rate for normal Boiler operation is 0.5 to 1%.

7. Operating the Boiler at lower or partial loads

Operating the Boilers on partial load requires more excess air & leads to incomplete combustion forming unburnts.

Calculated reasons for for SSC of Turbine

Boiler calculations for Boiler operation engineer (BOE) exam

Viva Questions & answers for preparation of BOE exam & interview

8. Operating the boiler at non-standard operating parameters

Operating the Boilers at non standard parameters like pressure, temperatures, flow etc will lead to the higher fuel consumption

9. Leakage into & out of the Boilers

Air & flue gas leakages into the Boiler & out of the Boiler will reduce the working efficiency there by increasing the boiler fuel consumption

10. Steam leakage

It is a direct cause for higher steam consumption. Generally steam leakage is from vent & drains valves, welding & flange joints

11. Boiler heating surfaces internal scaling

Pressure parts namely water wall tubes, economiser tubes & super heater coils internal & external scaling will result into poor heat transfer, which increases fuel input to produce required amount of steam.

Pressure parts internal scaling can damage the pressure parts by over heating

12. Radiation & Convection losses

Radiation & convection losses in the boiler causes increased fuel consumption. These losses may be due to uninsulated or unlagged surfaces of boiler

13. Lower combustion air temperature

On every 20 Deg C decrease in combustion air temperature leads to Boiler efficiency reduction by 1%

14. More ash content in the fuel

More ash content in the fuel takes away heat associated with it during discharging through hoppers. Especially bed ash is having more temperature. Also higher ash fuel are having lower GCV

Guide for Boilers troubleshooting


Why does Boilers main steam temperature increases more than design?

15. More Volatile matters (VM) in the fuel

Calorific value of the fuel reduces as the VM increases. Boilers using Lower GCV fuel consume more fuel

16. Other potential reasons for increased fuel consumption of a Boiler are;

Boiler design related issuers

Wrong selection of auxiliaries like fans & fuel feeding system

Low quality of Bed materials

Defects in fuel burners & fuel spreaders

Over refractory on internal heating surfaces

Faulty field instruments

Factors considered for Boiler Engineering

Also read Why & How these in Boilers???



Calculated reasons for increase in Turbine specific steam consumption

1. Lower vacuum

Turbine consumes more steam, if vacuum in condenser is maintained on lower side.

Example:  Consider a 20 MW Steam Turbine having Inlet steam parameters 65 kg/cm2 & 490 Deg C & Vacuum maintained in condenser is -0.9 kg/cm2.

Calculate the steam consumption of turbine at vacuum -0.9 kg/cm2 & -0.85 kg/cm2

A-Steam consumption Q at -0.9 kg/cm2 to develop 20 MW power

P =Steam flow X( Enthalpy of inlet steam-Enthalpy of exhaust steam)/ 860

Enthalpy of inlet steam at inlet steam parameters =810 kcal/kg

Exhaust steam enthalpy at -0.9 kg/cm2 vacuum = 619 kcal/kg

Then, 20 = Q X (810-619)/860

Q1 = 90 MT

B- Steam consumption Q at -0.85 kg/cm2 to develop 20 MW power

Exhaust steam enthalpy at -0.85 kg/cm2 vacuum= 623 kcal/kg

Then, 20 = Q X (810-623)/860

Q 2= 90.9 MT

It is clear that, Turbine operating at -0.9 kg/cm2 vacuum consumes lesser steam as compared to turbine operating at vacuum-0.85 kg/cm2

2. Lower inlet main stream pressure& temperature

Turbine operating at higher main steam pressure consumes lesser steam as compared to turbines operating at lower pressure

Example: Consider a 20 MW Steam Turbine having Inlet steam temperature 490 Deg C & Vacuum maintained in condenser is -0.9 kg/cm2.

A-Inlet steam parameters: Pressure: 65 kg/cm2 & temperature 490 deg C , Enthalpy = 810 kcal/kg

Exhaust steam parameters P = 0.9 kg/cm2 & Enthalpy = 619 kcal/kg

Steam consumption of Turbine Q = P X 860 / (Enthalpy of inlet steam-Enthalpy of exhaust steam)

Q = 20 X 860 / (810-619)

Q1 = 90.05 MT

B-Inlet steam parameters: Pressure: 87 kg/cm2 & temperature 515 deg C , , Enthalpy = 818 kcal/kg

 

Steam consumption of Turbine Q = P X 860 / (Enthalpy of inlet steam-Enthalpy of exhaust steam)

Q = 20 X 860 / (818-619)

Q2 = 86.43 MT

It is clear that, Turbine operating at pressure 65 kg/cm2 & temperature 490 deg C consumes more steam as compared to turbine operating at 87 kg/cm2 & temperature 515 deg C

3. Higher extraction/bleed steam flow

Steam turbines consume more steam to develop same power on higher steam extraction as compared to lower extraction.

Example: A condensing & extraction steam turbine having Inlet steam flow 105 TPH at pressure 65 kg/cm2 & 490 Deg C & Vacuum maintained in condenser is -0.9 kg/cm2.

Here we can cross check the power generation by steam turbine by increasing the extraction flow keeping inlet steam constant.

A-Extraction pressure = 2 Kg/cm2 & Temperature = 150 Deg C, flow = 75 TPH, Exhaust steam to condenser = 30 TPH

Enthalpy of inlet steam, H1 = 810 kcal/kg

Main steam flow Q1 = 105 TPH

Enthalpy of extraction steam = H2 =660 kcal/kg

Extraction steam flow Q2 = 75 TPH

Enthalpy of exhaust team = 620 kcal/kg

Exhaust steam flow Q3 = 30 TPH

Power developed by steam Turbine P = (Q2 X (H1-H2) / 860) + (Q3 X (H1-H3) / 860 )

P = (75 X (810-660) / 860) + (30 X (810-620) / 860) = 19.7 MW

B- Extraction pressure = 2 Kg/cm2 & Temperature = 150 Deg C, flow = 65 TPH, Exhaust steam to condenser = 40 TPH

Enthalpy of inlet steam, H1 = 810 kcal/kg

Main steam flow Q1 = 105 TPH

Enthalpy of extraction steam = H2 =660 kcal/kg

Extraction steam flow Q2 = 65 TPH

Enthalpy of exhaust team = 620 kcal/kg

Exhaust steam flow Q3 = 40 TPH

Power developed by steam Turbine P = (Q2 X (H1-H2) / 860) + (Q3 X (H1-H3) / 860 )

P = (65 X (810-660) / 860) + (40 X (810-620) / 860) = 20.16 MW

It is clear that, Turbine power generation at same inlet main steam flow will increase as extraction flow gets decrease & vice versa

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4. Higher pressure/temperature of extraction & bleed steam

Higher pressure/temperature of extraction & bleed steam leads to increased steam consumption to generate same power or power consumption reduces at same inlet flow.

Example: A condensing , extraction & bleed steam turbine having Inlet steam flow 105 TPH at pressure 65 kg/cm2 & 490 Deg C & Vacuum maintained in condenser is -0.9 kg/cm2

 A-Bleed steam 10 kg/cm2 & Temperature 200 Deg C, flow =25 TPH, Extraction pressure = 2 Kg/cm2 & Temperature = 150 Deg C, flow = 60 TPH, Exhaust steam to condenser = 25 TPH

Enthalpy of inlet steam, H1 = 810 kcal/kg

Main steam flow Q1 = 105 TPH

Enthalpy of bleed steam = H2 =674 kcal/kg

Bleed steam flow Q2 = 25 TPH

Enthalpy of extraction steam = H3 =660 kcal/kg

Extraction steam flow Q3 = 60 TPH

Enthalpy of exhaust team H4= 620 kcal/kg

Exhaust steam flow Q4 = 20 TPH

Power developed by steam Turbine P = (Q2 X (H1-H2) / 860) + (Q3 X (H1-H3) / 860 ) +(Q4 X (H1-H4)/860)

P = (25 X (810-674) / 860) + (60 X (810-660)/860) + (20 X (810-620)/860)

P = 18.82 MW

B-Bleed steam 14 kg/cm2 & Temperature 260 Deg C, flow =25 TPH, Extraction pressure = 2.5 Kg/cm2 & Temperature = 170 Deg C, flow = 60 TPH, Exhaust steam to condenser = 25 TPH

Enthalpy of inlet steam, H1 = 810 kcal/kg

Main steam flow Q1 = 105 TPH

Enthalpy of bleed steam = H2 =704 kcal/kg

Bleed steam flow Q2 = 25 TPH

Enthalpy of extraction steam = H3 =669 kcal/kg

Extraction steam flow Q3 = 60 TPH

Enthalpy of exhaust team H4= 620 kcal/kg

Exhaust steam flow Q4 = 20 TPH

Power developed by steam Turbine P = (Q2 X (H1-H2) / 860) + (Q3 X (H1-H3) / 860) + (Q4 X (H1-H4)/860)

P = (25 X (810-704) / 860) + (60 X (810-669)/860) + (25 X (810-620)/860)

P = 18.43 MW

It is clear that, Turbine power generation reduces at higher extraction or bleed steam pressure &temperature

Note: Steam consumption of turbine increases if,

1-Bleed steam & extraction steam pressure increases

2-Bleed steam & extraction steam temperature increases

3-Bleed steam flow & extraction steam flow increases

4. Increase of exhaust steam temperature due to more clearance in labyrinth seals

Turbine steam consumption increases if exhaust steam temperature to condenser increases.


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