How do you carryout performance Guarantee (PG) test of power plant equipments??

 

What do you mean by performance Guarantee (PG) test?

 It is a test carried out to measure the performance of an equipment as guaranteed by the manufacturer.

What are the equipments on which PG test is carried out in power plants?

Generally all the equipments should met manufacturer guarantee performance value, but in Power plant, Boiler, Turbine & Generators are the major & critical equipments where PG tests are carried out.

When & who do carryout PG test?

PG test is carried out after erection & commissioning of the equipments and before hand over of the equipments PG test is carriedout.PG test is carried out. It is carried out by Original Equipment Manufacturer (OEM).

How do you carryout PG test?

For conducting the PG test, some parameters are measured & compared with standard design & operating values. Before conducting PG test, it is mutually agreed between OEM & Owner what parameters to be measured & means of measurement. And also it is mutually agreed that, how much time this test will be conducted. In some cases PG test is conducted for 8 hours, in some cases 24 hours.

And also the frequency of parameters measurement is decided before commence of PG test.

Procedure for PG test.

Testing Methodology: Standard testing methodology is decided

Testing equipment: Type of equipment, its measuring accuracy & calibration reports

Tolerance: The margin of error.

Ambient temperature: It is most important for conducting PG test since all the equipments & systems are designed on the basis of atmospheric temperature.

Parameters Log sheet & List of Operation team to be involved in PG tests are decided before the test.

Once the PG test completes, log sheets are collected & should be signed by owner & OEM for future reference.

What is the significance of carrying out PG test in Boilers?

PG test is carried out to ensure following key performance Indicators (KPIs) of Boiler

• Specific fuel consumption of the Boiler or steam to fuel ratio (SFR)
• Steam Purity
• Steam pressure & temperature at various operating condition
• Boiler efficiency
• Load stability during various load demand
• Stack gas quality
• Minimum & maximum rating

What parameters are measured during Boiler PG test?

• Steam pressure & temperature
• Steam flow & feed water flow
• Fuel consumption
• Attemperator/Desuper heater water flow
• Feed water parameters like pH, conductivity, silica, Hydrazine
• Boiler Water parameters like pH, conductivity, silica, Phosphate
• Steam parameters like pH, conductivity, silica etc
• Feed water temperature at Deaerator outlet
• Feed water temperature at Economiser inlet
• Exhaust flue gas temperature
• Excess air & O2% in flue gas
• Flue gas parameters like SPM, SOx, NOx etc
• ESP & APH inlet & outlet flue gas temperature for air leakage test
• Combustion air temperature after APH
• Unburnt level in ash
• CBD water flow
• Drum level
• Boiler auxiliary power consumption
• Operating % of load Fans& fuel feeding system at various Boiler load.

In this test, a boiler is allowed to generate steam at various load conditions. Its capability to generate steam at required parameters and required efficiency is checked.

Note: While conducting Boiler PG test, input parameters like fuel moisture, GCV etc kept as per design values

What is the significance of carrying out PG test in Turbines?

PG test is carried out to ensure following key performance Indicators (KPIs) of Boiler

• Specific steam consumption (SSC)
• Exhaust steam temperature
• Condenser vacuum
• Heat rate & efficiency
• Turbine bearing vibrations & temperature
• HP valve demand during various load demand
• Turbine Noise level
• Stability during sudden load cut off
• Steam pressure & temperature of extraction & bleed steam
• Turbine auxiliary power consumption

What parameters are measured to conduct PG test of steam Turbine?

• Turbine inlet steam pressure & temperature
• Turbine inlet steam flow
• Auxiliary steam flow
• Condenser inlet & outlet cooling water temperature
• Turbine & Gear box all bearings & vibrations
• Noise level around turbine
• Load on Generator
• Oil cooler inlet & outlet water & oil temperature
• HP & LP valve lift & demand
• Turbine casing thermal expansion
• Wheel chamber pressure
• Pressure, temperature & steam flow of extraction & bleed steam
• Exhaust steam pressure, temperature and flow

What parameters are checked for PG test of Generators?

• Generator output power
• Terminal voltage
• Frequency
• Current
• Power factor
• Winding & air temperature
• Air cooler inlet & outlet water temperature

 

 Read.

Power plant equipments SOP

Power plant & calculations.

 

 

Standard Operation Procedure of Oil filter & oil Cooler change over

 

SOP: Oil Filter Change Over

Follow the below mentioned steps for changeover of filter.

This procedure is valid for duplex filter.

• Ensure Filter DP is high enough to change the running filter to stand by filter.
• Ensure that stand by filter is provided with filter element, which is cleaned or replaced with a new one.
• Open the vent of the standby filter.
• Crack- open the filter equalizer line.
• See that air is coming out of filter, close vent as soon as full bore liquid comes out of it.
• Operate change over mechanism.
• Observe that filter DP has come down to minimum DP position in the indicator.
• Close the equalizer line.
• Clean the choked filter & keep ready for immediate use.

SOP: Cleaning of Choked oil Filter Element

Follow below steps to clean or replace filter element.

• Open drain and vent of choked filter.
• Ensure complete draining of filter body.
• Open the filter flange and remove the filter element(s).
• Clean the filter body from inside.
• Clean the filter element with fresh water/ petrol and dry it with dry air, if it is a reusable filter or use new cartridge if it is a non-reusable one.
• Close the filter flange.

Oil Cooler Change Over

This procedure is valid where duplex type oil cooler is provided. When running cooler is required to do maintenance due to leakage, non-performing etc., it needs to change over to standby one. Proceed as per below mentioned steps for cooler change operation.

• Ensure stand-by one ready for operation.
• Ensure stand-by oil cooler vents on both tube and shell side of the cooler is open.
• Ensure the cooler drains are closed.
• Charge Cooling water in the cooler and close waterside vents after removing entrapped air.
• Open cooler oil equalizer line. It takes some times to fill a cooler.
• Close oil vent once entrapped air is completely removed.
• Operate change over mechanism.

Check all the parameters of oil and cooling water.

Control oil temperature by operating CW valve.

Power plant equipments standard operating procedures (SOP)

 

SOP: Standard Operating Procedures

SOP is to provide a harmonized organizational framework for the operation of equipments and system.

Objectives of SOP

SOPs are detail-oriented documents and provide step-by-step instructions as to how employees within an organization must go about completing certain tasks and processes.

SOP of Centrifugal Pumps:

START:

For starting of a centrifugal pump proceed as stated below. However, when a pump is put on remote & auto, its suction and discharge valves are normally kept open unless specific logic and protection is implemented.

• Ensure there are no work permits on equipment & equipment is in normalized condition.
• Ensure tank level is normal.
• Ensure suction valve is open & suction pressure is normal.
• Ensure field all instruments are in service.
• Ensure proper lubrication for pump bearing
• Ensure cooling water flow & pressure to bearings & mechanical seal (If provided)
•  Ensure Discharge valve is closed.

Note: For high discharge head pumps, normally discharge valve is in closed condition and there will be minimum recirculation valve. And low discharge head pumps discharge valve is in open condition

• Ensure that all the protection and interlocks are in service.
• Prime the pump by opening air vent from pump body or discharge vent.
• Give start- command by operating LPB or from DCS.
• Once pump achieves normal speed, open discharge valve slowly.
• Check current, vibration, bearing temperature, any noise etc. and record.

SOP STOP:

• To stop a centrifugal pump follow below mentioned steps.
• Keep integral by pass open & close discharge valve, .
• Issue stop command either from local push button or from DCS.
• Keeps cooling water flow some more time to gland cooling etc.
• If the pump is kept as stand by, don’t close CW line valve
• If the pump is stopped for maintenance, isolate suction valve, discharge integral bypass, minimum re-circulation line valve and balancing leak off line valve.
• Stop cooling water flow to pump gland.

SOP of positive displacement pumps:

Plunger pump, reciprocating pump, screw pump& gear pump are such pumps in this category. MOP, LDO pump are gear pumps, lime dosing pump etc. are of screw pumps.

Pumps like HP/LP dosing pumps are plunger pump which are normally used in power plant.

START:

• Follow the steps below for startup of such pump.
• Ensure there are no work permits on equipment & equipment is in normalized condition.
• Ensure normal tank level.
• All field instruments are in service.
• Ensure proper lubrication for pump bearing.
• Ensure suction & discharge valves are open.

Note: Positive displacement pumps should be always started with discharge valve open

• Ensure that integral pump relief valve & that of on discharge line are not gagged.
• Ensure that all the protection and interlocks are in service.
• Prime the pump by opening air vent from pump body or discharge vent.
• Give start- command by operating LPB or from DCS.
• Check current, vibration, bearing temperature, any noise etc.. and record the data.

SOP STOP:

 Switch off keeping all the valves on.

Reference books for power plant O&M

Cooling Water Pump/Tower

• To take cooling tower in service, proceed as stated below.
• Ensure that Cooling Tower sump is filled with makeup water up to operating level.
• Tower distribution header valves are opened.
• CW return water line valves are open.
• CW pumps are available for operation and free to rotate.
• CT fans are available for operation.
• CT fan gearboxes are filled with requisite lube oil (LO) and up to operating level.
• Protections for CWP and CT fan are in service.
• Ensure field instruments are in service.
• Open suction valve for selected pump, keep discharge valve close.
• Prime pump by opening air release valve on pump.
• Start CW pumps and gradually open the discharge valve.
• Charge cooling water in condenser, lubricant oil (LO) cooler, and generator cooler.
• Check discharge pressure, vibration, bearing temperature and motor current.
• Check distribution of cooling water in tower and adjust deck valve to make it uniform.
• Maintain sump level. Put other cooling water pump on auto.

Note:

 Before putting any pump on auto, ensure that pump’s suction and discharge valves are open and priming of the pump is done.)

SOP Lube Oil cooler & Oil filter change over

SOP Boiler Feed Water Pump start up

Follow the steps given below to start a BFP

• Ensure there are no work permits on equipment & equipment is in normalized condition.
• Ensure Deaerator level is normal
• Ensure pump suction pressure is normal
• Pump and Motor bearings are properly lubricated and oil cups contain oil.
• Ensure suction strainer differential pressure is normal
• All protection and interlock are in service.
• All field instruments are in service.
• CW line for bearing cooling & gland water cooling is open.
• Open suction valve, keep discharge valve close.
• Ensure minimum re circulation and balancing leak off line valves are open.
• Start pump by operating Local start Push Button or from DCS.
• Ensure pump has reached 50% RPM in just 10 seconds to avoid bearing failure & rubbing of balance & counter balance discs.
• Gradually open discharge valve. If integral by pass valve is provided, open by pass valve first. Once Feed line is pressurized, main discharge valve can be opened fully.
• Check all parameters, bearing temperature, vibrations, suction / discharge pressure, balance leak off pressure, motor winding temperature etc.
• Put other pump(s) on auto.

SOP Instrument Air Compressor (Reciprocating)

Follow the steps given bellow to start a compressor

• Ensure there are no work permits on equipment & equipment is in normalized condition.
• All protection and interlock are in service.
• All field instruments are in service.
• Sufficient lubricant oil (LO) is present in crank sump.
• CW is charged in compressor and after cooler and flow switch is reset.
• Moisture Traps are in service.
• Suction air filter is cleaned.
• Discharge valve is open.
• Start compressor.
• Check loading and unloading of compressor.
• Record loading unloading current and pressure.
• Check discharge temperature.

Pump Change Over SOP:

• Ensure that stand by pump is available for operation.
• Prime the pump after opening its suction valve. (Where minimum re circulation line is provided, open re circulation line valve).
• Start pump either from local or from remote.
• Open discharge valve and close minimum re circulation line valve.
• Gradually close discharge valve of previous pump. (where minimum re circulation line is provided , open re circulation line valve before closing discharge valve)
• Ensure that incoming pump is maintaining all parameters like discharge pressure, bearing temperature & vibrations.
• Switch off the previous pump.

Boiler Gauge Glass Operation

Initial line up SOP

• Crack open the steam cock. Wait for some time till the gauge glass is heated slowly.
• Crack open the water cock.
• Close the drain cock & vent valve.
• Open the steam cock and water cock fully.

SOP for Gauge glass flushing

• Close the water cock and open the drain cock for some time.
• Close the drain cock and open the water cock.

Note: Water should return to its normal working level quickly. If this does not happen, then there is a blockage in the waterside

• Then Close the steam cock and open the drain cock for some time.
• Close the drain cock and open the steam cock.

Note: If the water does not return to its normal working level quickly, then there is blockage in the steam side.

Charging of Main Steam Line

This procedure is applicable when main steam line is depressurized and first boiler is coming into service. Proceed as follows for charging main steam line.

• Ensure that boiler has achieved at least 60% of its rated pressure
• (for detail operations of boiler refer boiler operation from OEM manual).
• Ensure that that all the drain line valves are open along with stream trap by pass.
• Open MSSV by pass partially so that line steam pressure is at 5 kg/ cm2.
• Heat up line at least for 10 min.
• Increase pressure up to 10 kg/ cm2 for another 10 min. To control main steam pressure line, warm-up vent can be opened and regulated.
• Once dry steam is observed  coming out from all the drains, close the steam trap by pass and keep all the traps in service.
• Increase pressure of the steam line near about the boiler pressure and open MSSV. Before operating MSSV, care to taken that steam pressure before and after MSSV is more or less same. To match the steam pressure warm up vent can be throttled.
• Increase pressure and temperature as required for turbine start up.
• It is to be noted that increase of temperature up to 300 deg C should be 3-5 deg C per minute. Above 300 degC the increase of main steam line should be 5-7 degC per minute.

SOP Ejector System

Normally ejector system consists of one set of Hogger and 2 main ejectors. For ACC ejector system there is

One set of Hogger system and 2 set of service ejector. Each service ejector set consists of 2 nos of ejectors, 1 in 1st stage and 1no ejector in 2nd stage.

To take Hogger ejector in service follow following guidelines

• Ensure auxiliary steam is available at desired pressure and temperature
• Ensure vacuum breaker valve fitted on steam condenser is closed
• Ensure cooling water is circulating in the condenser and the turbine gland is charged fully at 0.1 kg/cm2
• Note: During cold start up gland sealing is charged after taking hogger into line (after vacuum pulling) i.e say at vacuum -0.2 to -0.5 kg/cm2 & During hot start up gland sealing is charged before taking hogger into line (before vacuum pulling).
• Ensure live steam line to ejector steam lines drain are kept open.
• Charge the main steam line to ejector steam & temperature control valve.
• Ensure the rated pressure (10 kg/cm2 or as specified by OEM) and temperature.
• Once the rated parameters are reached open the steam valve of starting or hogger ejector.
• Observe the steam is vented to the atmosphere.
• Then open the ejector airline valve.
• Observe vacuum inside the condenser increasing slowly and will reach 60 to 70% of rated vacuum within 20 minutes

 Read More SOPs.

Emergency operation guide in power plants

Slop fired Boiler SOP

Turbine oil flushing SOP

Coal handling plant SOP

Boiler refractory dry out SOP

Boiler feed pump start/stop SOP

Steam turbine cold, warm & hot start up SOPS

Boiler Alkali Boil out SOPs

Boiler Hydraulic test SOP

15-Emergencies in power plant operation

 

Emergencies in power plant operation: Following are some of the emergencies that are normally faced during operation of power plant.

1.Tripping of boiler: Following are the main cause of tripping of boiler

• Low drum level
• High furnace pressure
• High/ low bed temperature
• Tripping of boiler due to failure of FD, PA, SA  and ID fan
• Electrical fault in Boiler MCC

2.Tripping of Boiler; Case: 2 Boilers & 2 Turbines

Actions to be taken:

• Reduce load at turbines so that inlet pressure to turbine maintains at operating value.
• Share load equally on both the turbines.
• Close main steam stop valve of the tripped boiler.
• Ensure that all coal feeders (fuel feeding system) and fans are stopped on tripping of boiler.
• Maintain drum level.
• If required stop one boiler feed pump (BFP).
• Check the cause of tripping of boiler and try to rectify the fault.
• If boiler fault is rectified, start the boiler with startup compartment and gradually increase boiler pressure and temperature (Follow hot/warm start up curve)
• Synchronize the boiler with the running boiler.
• Start one more BFP
• Take compartment one by one into line and increase the load
• Maintain the equal load on both turbines as per requirement
• Finally stabilize the power plant operation.
• If the boiler fault cannot be rectified immediately, decision of stopping of one boiler can be taken after due consultation with station manager.

3.Tripping of Turbine

Followings are some of the causes of tripping of turbine

• Any one of the protections or interlocks of turbine or generator generally initiates tripping of turbine.
• In some of the cases spurious tripping is caused due to mal functioning of instruments.
• Due to mal operation of the operating staff.

4.Non-availability of Fuel (Normal Shut Down): (Case: 2 Boilers & 2 Turbines)

Take planned shutdown of power plant in following ways.

• Reduce station load by switching off export feeders.
• Stop one turbine and put it on turning gear once turbine speed comes to zero.
• Stop one boiler by slumping the compartments one by one. Slumping of compartment is done in the reverse direction i.e. 5th compartment is slumped first and so on.
• Reduce further load by switching off the auxiliaries.
• Finally, one turbine runs on auxiliary power load. If STG running on synchronized condition, generator breaker can be opened on auxiliary load. If STG runs on islanding mode, synchronize STG with DG or grid and transfer auxiliary load to DG or grid before opening Generator breaker at minimum STG load.
• Stop the turbine and put on turning gear in due time.
• Stop ACC fans or CT fans, CEP etc. in due time.
• Keep open main steam line & other process steam line drains.
• Once fuel is made available, restart power plant as per cold start up procedure

5.Non-availability of DM Water

• Plan for normal shut down.
• Build up DM water in DM storage tank and restart Power plant as per start up procedure

6.Fuel handling / Fuel feeding system Break down

• Causes of Fuel handling & fuel feeding system failure
• Belt cut
• Mechanical equipments like gear box, coupling & pulley failure
• Electrical equipments like motor & feeders failure

Take following actions

• Inform the station Manager & reduce the steam demand
• Switch off the export feeder
• Trip the Turbine & put it on turning gear as per SOP
• Stop the other fuel feeding & fuel handling system
• Stop the fans sequentially
• Hot box up the Boiler as per SOP
• Attend the breakdown
• Re-start the plant as per SOP

7.Boiler feed pump incomer supply failure

• Causes of incomer supplier failure,
• Breaker trip
• Relay malfunction

Take following actions

• Reduce the steam demand, trip the export feeders
• If supply is not restored within minute,trip the Boiler & Turbine manually
• Hot box up the Boiler
• Put STG on turning gear as per SOP
• Stop the fuel handling system
• Identify & troubleshoot supply failure
• After restoring the BFP incomer power supply, stat the Boiler feed pump & maintain drum water level
• Start the Boiler as per SOP (Hot or Warm)

8.Main steam line leakage

• Probable Causes of main steam line leakage,
• Leakage in welding joint due to corrosion & rusting
• Uneven expansion
• Water hammering

Take following actions

• If leakage is heavy inform the station Manager & reduce the steam demand
• Switch off the export feeder
• Trip the Turbine & put it on turning gear as per SOP
• Stop the fuel feeding & fuel handling system
• Stop the fans sequentially
• Hot box up the Boiler
• Identify & arrest the leakage
• Analyze the causes of leakage
• Start the Boiler & STG as per SOP

9.Turbine HP valve gland leakage

Probable Causes of HP valve gland leakage,

• Turbine Load hunting
• Ageing
• Poor fitment of gland packings during overhauling

Take following actions

• If leakage is heavy inform the station Manager & reduce the steam demand
• Switch off the export feeder
• Trip the Turbine & put it on turning gear as per SOP
• Stop the Boiler as per SOP
• After cooling, attend the gland leakage
• Start the Boiler & Turbine as per SOP

10.Tripping of Auxiliary Transformer

• Following are the probable cause of tripping of auxiliary transformer.
• Heavy earth fault in any of the LT drives.
• Tripping on transformer protection like low oil level, high oil/winding temperature, Buchholz relay operation etc.

On tripping of auxiliary transformer, total power plant will trip. Proceed as follows to tackle the emergency.

• Resume auxiliary power immediately.
• Ensure STG have got tripped and shutdown safely
• Ensure boilers are tripped.
• Close MSSV.
• The drives, which were put on auto, take all of them on manual.
• Close all the control valves.
• Once auxiliary power is available, start one BFP and take water into boilers.
• To resume auxiliary power stand by Auxiliary transformer can be taken to service if HT voltage available in bus or by closing PCC bus coupler.
• Put STG on turning gears after starting AOPs.
• Start the power plant as per hot start up procedure.

11.Tripping of Export Transformer

• Following are the probable causes of tripping of export transformer.
• Heavy earth fault in any of the LT drives.
• Tripping on transformer protection like low oil level, high oil/winding temperature, Buchholz relay operation etc.

On tripping of export transformer,power plant will come to Island mode operation. Proceed as follows to tackle the emergency

• Ensure Turbine has not tripped on high pressure
• Maintain Boiler operating pressure by controlling start up vent control valve
• Operate Boiler & STG on home load
• If process needs steam, charge the steam from PRDSH as per SOP
• Maintain Boiler load as per steam process demand
• After troubleshooting the transformer, synchronize the Turbine with grid & start to export the power
• Slowly cut off the PRDSH steam to process & charge the process steam line through Turbine extraction steam.

Reference books for power plant O&M

 12.Tripping of Export Feeder

Probable cause of tripping of feeders are,

• Over load
• Earth fault
• Maintain main steam header pressure

Take following actions

• Ensure that dumping system has acted to cope up increase in pressure. If dumping system is not available, maintain Boiler pressure by operating start up vent CV & also take combustion system in manual mode to reduce firing as per requirement
• Reduce load on boiler, if required slump one compartment of a boiler or both the boilers.
• Ensure that dumping system ceases to operate and system is stabilized at reduced load.
• Analyze the cause of tripping of feeder and rectify.
• Once problem is sorted out and rectified, take export feeder in service after due consultation with consumer.
• Gradually increase load on power plant and stabilize.

13.Turbine Oil Leakage

• Causes of oil leakage in turbine area,
• Leakage in oil line caused by failure of joints or flanges or due to vibration in oil line.
• Spillage through centrifuge due to seal break.

Take following actions

• If it is in Lube oil (LO) oil or hydraulic oil line, plan for safe shut down.
• Try to attend leakage under emergency plan.
• Analyze the cause for oil leakage to avoid future leakages
• Do leak testing and restart the turbine
• If it is in other area like in Centrifuge, isolate centrifuge.
• Top up oil in MOT, if required.

 14.DCS failure

• Probable Causes of DCS failure,
• DCS power supply failure
• DCS controllers failure
• DCS other accessories like card, switch & SMPs etc failure

Take following actions

• During DCS failure, DCS operators cannot judge the plant operating condition so need to take following actions.
• If Turbine not tripped automatically, trip it manually through emergency push button provided in Governor panel.
• Trip the Boiler manually (Stop Fuel feeding system, Boiler fans & fuel handling system) & close MSSV manually
• Start Turbine Lube oil pump manually & put STG on barring gear.
• Start BFP manually & operate the control valves manually in field.
• Observe drum level from local level gauge glass
• Analyze the cause of DCS failure.
• After troubleshooting start the DCS as per SOP
• Then start the plant as per SOP (Hot or warm)

15.UPS  failure

• Probable Causes of UPS failure,
• UPS battery failure
• UPS cards failure

Take following actions

• After UPS failure, DCS also gets fail & DCS operators cannot judge the plant operating condition so need to take following actions.
• If Turbine not tripped automatically, trip it manually through emergency push button provided in Governor panel.
• Trip the Boiler manually (Stop Fuel feeding system, Boiler fans & fuel handling system) & close MSSV manually
• Start Turbine Lube oil pump manually & put STG on barring gear.
• Start BFP manually & operate the control valves manually in field.
• Observe drum level from local level gauge glass
• Analyze the cause of UPS failure.
• After troubleshooting of UPS start the DCS as per SOP
• Then start the plant as per SOP (Hot or warm)

 

 Read: POWER PLANT && CALCULATIONS

 

 

 

 

What do you mean by Regenerative system in power plants???

 

Thermal power plants efficiency is in the range of 30 to 40%, the improvement of thermal cycle efficiency can be done either by increasing the inlet steam pressure & temperature or decreasing the turbine exhaust pressure. But improvement of Boiler parameters & decreasing exhaust pressure lead to increase in cost & also have limitations related to metallurgy & risk.

Another way is to increase the thermal efficiency is by using regenerative cycle. This cycle is more efficient than Rankine cycle.

What do you mean by Regenerative process or cycle???

In this process, steam is extracted from turbine at one or more points during steam expansion. This pressure is high, medium & low. Steam after some expansion cycle gets feed water heating ability. Such extracted steam is utilized to heat the feed water going to the Boilers nearer to its saturation temperature. Heating the Boiler feed water temperature ultimately increases the overall thermal efficiency.

How does the increase in feed water temperature increase the overall thermal efficiency??

Increase in feed water temperature at economizer inlet reduces the work done by boiler to generate the steam & hence consumes less fuel. As a thumb rule, on every 6-7 degree C rise in feed water temperature reduces Boiler fuel consumption by 1%.

What are the advantages of Regenerative cycle???

Regenerative cycle helps to increase in power plant thermal efficiency

Amount of steam condensed in steam condenser per KW decreases

Cooling water consumption decreases

Condenser size reduces

Auxiliary power consumption of cooling system reduces

Heat rate of the plant drastically reduces

Due to less fuel consumption load on fuel handling, fuel feeding & Boiler fans decreases & hence saving in plant auxiliary power consumption.

What are the major disadvantages of Regenerative cycle or process?

There are no much disadvantages except the requirement of HP, LP heaters, relating piping & controlling equipments.

What are the major parts of Regenerative cycle?

HP heaters, LP heaters & Deaerator.

What are the HP heaters?

HP heaters are the shell & tube type of heat exchangers situated between Boiler feed pumps & economizer.

The main design purpose of the HP heater is to heat the feed water coming from Boiler feed pump.

 

Why the name HP heater?

Because it I situated in high pressure zone that is at Boiler feed pump discharge feed water circuit

What are the heat transfer areas present in HP heaters?

Main heat transfer zones are

De-super heating zone

Condensing zone

Sub-cooling zone

What is the function of de-super heating zone in HP heaters?

It is separate heat exchanger placed within the shell, its main function is to remove the super heat from extracted steam

What is the function of sub-cooling zone in HP heaters?

It is another separate counter flow heat exchanger placed within the HP heater shell, its main function is to sub cool the condensate formed in condensing zone

What are LP heaters & where they are placed?

The condensate formed in the surface condenser is pre heated to elevated temperature before it goes to deaerator are called LP heaters.

LP heaters are placed between deaerator & ejector or CEP

LP heaters are also having 3 zones as like HP heaters

Why the name LP heater?

LP heaters are placed at low pressure zone from CEP to deaerator hence called LP heaters

Schematic diagram of power plant regenerative system

 

How do you prove that, regenerative cycle will increase the thermal power plant efficiency?

This can be explained by taking an example

Sl No.	Particular	UOM	Boiler-1	Boiler-2
1	Boiler steam generation	TPH	100	100
2	Steam pressure	Kg/cm2	87	87
3	Steam temperature	Deg C	515	515
4	Boiler efficiency	%	69	69
5	Fuel GCV	Kcal/kg	4300	4300
6	HP heater available	YES/NO	Yes	No
7	Feed water temperature at economizer inlet	Deg C	160	110

 

Looking at the above example, both boilers seem to be safe, except Boiler-1 has HP heater that is feed water heater & Boiler-2 has no HP heater.

Based on this we shall calculate fuel consumption of both the Boilers.

Enthalpy of steam at above parameters Hg = 818 kcal/kg

Enthalpy of feed water at temperature 110 deg C, Hf1 = 111kcal/kg

Enthalpy of feed water at temperature 160 deg C, Hf2 = 162kcal/kg

Now we shall calculate the fuel consumption of Boiler-1

Boiler1 = Steam flow X (Steam enthalpy-Feed water enthalpy) / (Fuel GCV X Boiler efficiency)

Boiler 1 =100 X (818-160) / (4300 X 0.69)

Boiler 1 fuel consumption = 22.17 TPH

Boiler2 = Steam flow X (Steam enthalpy-Feed water enthalpy) / (Fuel GCV X Boiler efficiency)

Boiler 2=100 X (818-110) / (4300 X 0.69)

Boiler 2 fuel consumption = 23.86 TPH

Looking at the fuel consumption of both the Boilers, Boiler 1 consumes less fuel as it has HP heater & hence more feed water temperature than Boiler-2

 Less fuel consumption in the sense less heat rate & less heat rate is nothing but more efficiency of the plant

 

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