CONDENSER VACUUM IMPROVEMENT STAGE-I PRANAY KUMAR EMP. NO.-100840 ENGR (GROUP-C)

PRESENTATION HIGHLIGHTS

SIMPLE RANKINE CYCLE (Condensing Turbine Type)

NECESSITY OF VACUUM

FACTORS AFFECTING VACUUM (Causes Of Low Vacuum)

VACUUM IMPROVEMENT METHODS

IMPACT OF VACUUM IMPROVEMENT ON PLANT PERFORMANCE

As specific volume of steam is more than water, so when steam condenses after doing work in turbine, vacuum is created with some non-condensable gases.

As we know Enthalpy or Heat drop which is converted into mechanical work in turbine, is more at lower pressure (In case of HP,LP & LP turbines in a system,HP-23%,IP-34%,LP-43%).We get more work at lower pressure.

i.e. we need to create & maintain vacuum in order to have higher cycle efficiency which ultimately leads to less fuel consumption.

Adiabatic Expansion in TurbineConstant Pressure Heat Rejection in CondenserPump WorkSensible heat Addition in Economizer+Regenerative FeedWater HeatersENTROPYTEMPERATURELatent Heat Addition in Evaporator (constt. Pressure)Super Heating L + VBASIC RANKINE CYCLE (SUB-CRITICAL)

The heat rate of a power plant is the amount of chemical energy, in the fuel, that must be supplied to produce one unit of electrical energy(1 KWHr)

Heat rate is expressed in kcal/kWhr

HR = (input in kcal) / (output in kWhr)= (input in kcal) / (output in kcal/ 860)= 860 X (input / output)= 860 / efficiency Efficiency (%) = (860 / heat rate) X 100

UNIT = TURBINE X BOILER

860/UNIT HR = 860/TURBINE HR X BOILER 1/UNIT HR = 1/TURBINE HR X BOILER UNIT HEAT RATE = TURBINE HR/BOILER EFFICIENCY

EFFECT OF SUPERHEAT

Superheating the steam to higher temperature without increasing the boiler pressure increases thermal efficiency.It also decreases the moisture content of the steam at the turbine exit.

LIMITATION: Highest temperature of superheated steam is limited by the metallurgical constraint.

EFFECT OF INCREASING THE INLET PRESSUREIncreasing the inlet pressure raises the mean temperature at which heat is added in the boiler thereby increasing the efficiency.

Side Effects:Increases moisture content at the final stages of the turbine that decreases the turbine efficiency and erodes turbine blades.

EFFECTS OF LOWERING THE CONDENSER PRESSURECondenser accounts for 40-45% heat loss in Turbine cycle. So its performance Improvement plays a vital role in overall efficiency improvement(Heat-Rate Reduction)

Lowering condenser pressure lowers the temperature at which condensation takes place thereby increasing the cycle efficiency.

LIMITATION AND SIDE EFFECTS : Lower limit is the saturation pressure corresponding to the temperature of cooling media. Creates possibility of Air Leakage into the condenser Increases moisture content of the steam at the final stages of turbine that decreases the turbine efficiency and causes erosion in turbine blades.

EFFICIENCY LOSS(INCREASE IN HEAT-RATE) DUE TO PARAMETERS DEVIATION

Parameters Deviations Loss of Heat Rate in Kcal/Kwh Additional Coal Per month (MT) Additional Coal Cost per month (Lakhs) Vacuum 5 mmHg 104052.46Partial Load 5% reduction 9.98404.22.46Low FW Temperature One HP Heater out for 24 Hrs. 249725.91FW Temp. at ECO. inlet 1 C 0.8 32.400.20Increase in MU Water consumption 1%( 6.71 T/Hr.) 15.19615.203.74Drop in MS Temp. 1 C 0.9237.260.23Drop in HRH Temp. 1 C 0.6927.950.17Increase in RH Spray 5 T/Hr. 3.21130.010.79Rise in CW Temperature 1 C 7.51304.161.85Drop in MS Pressure 1 Ksc. 1.3655.080.33Rise in Flue gas exit temp. 1 C 1.5462.370.38

CAUSES OF POOR VACUUMCW inlet temperature CW flowImproper Venting During CW Line Charging to CondenserCooling Tower Performance,Location Poor Ejector PerformanceDirty tubes (Scale inside Tube-Hard Scales of Ca,Mg)Air Ingress into CondenserInsufficient Seal-Steam PressureLeakages in Low Pressure Drain Lines From LP Heaters Connected to Condenser. Passing in Vent Lines Connected from LP Heaters to condensers.Improper Hotwell Level.

VACUUM IMPROVEMENT METHODSAir-Ingress Test & Defects RectificationMaintaining Proper Seal Steam Pressure specially during low load operation(Ex. 1 Mill Unloading Problem)Proper Venting of CW lines while charging condenserCleaning of CT fills during O/H,Repairing.Check if proper distribution of water inside the cooling tower from above.Maintain Proper flow in CW line for achieving proper vacuum.Proper selection of CW pump,regular maintenance.(Ex CW 6 taking high current with same flow)Condenser water tubes off-line JET/BULLET cleanings.Bullet cleaning is less effective,suitable for soft scales,effect for shorter duration.JET cleaning is done at around 300-400 ksc of water jet pressure.Suitable for hard Ca,Mg scales.More effective than bullet cleaning.Flame test is recommended after this.Flood test during O/H for neck joints & other points leakage detection.DM water filled upto neck joint level. Steam pressurizations test is done by pressurizations of condenser by steam leakage is checked ( if any)A new concept of On-Line-Tube-Cleaning System))OLTCS is also in practice in many plants.Spongy Balls size less than water tube diameters are used with proper control & instrumentation.

Ejector performance detoriorates due to its nozzle problem,its tube leakage,These can be checked during O/H.CW CHEMICAL DOZINGChlorination Controlling Microbiological fouling Filtration Prevention of fouling of heat transfer surface. Sulfuric acid Regulation of pH Inhibitors Protection of Metal from Steel/Copper corrosion. Antiscalent Precipitation of Alkaline earth salts Antifoulant Retarding deposition of corrosion products.

MICRO ORGANISMSBacteria, algae & fungi present in cooling water circuit decreases the efficiency of heat transfer in cooling tower and condensers. Chlorine is the most widely used chemical in industry as oxidizing agent for destruction and dissolution of micro-organisms. Chlorination is effective when cooling water pH is between 6 and 7When COC increases above recommended value,blow-down is to be done in the CW return line header(Hot Duct) as per chemistry guidance.Blow-down helps in maintaining the concentrations of alkaline salts like Ca,Mg in CW waters,which are responsible for scaling of condenser water tubes.

IDENTIFICATION OF AIR INGRESSAIR INGRESS IDENTIFICATIONHELIUM LEAK DETECTION TEST(M/C On Load)CONDENSER FLOOD TEST(M/C Off-Load)STEAM PRESSURISATION TEST(M/C Off-Load)

IDENTIFICATION OF AIR INGRESS WORKING PRINCIPLE:

The Helium Leak Detection Test is new method based on helium acting as tracer gas that allows an easy and quick location of leaks. The use of helium is advantageous because it is a nontoxic, nonflammable, relatively inexpensive and quickly diffuses through small leaks.

Helium is sprayed at the point where leak is to be checked by means of portable unit which has facility of helium spray. If there is any ingress inside condenser, Helium will also enter with air which is displayed in Helium Test Gen.

IDENTIFICATION OF AIR INGRESS

IDENTIFICATION OF AIR INGRESS

IDENTIFICATION OF AIR INGRESS

FLOOD-TEST & STEAM PRESSURISATION TESTCONDENSER FLOOD TEST & STEAM PRESSURISATIONTEST Condenser flood test is done by filling DM water in condenser shell side upto neck-joint and water leakage is checked ( if any). Standard procedure should be followed for Condenser flood testSteam pressurizations test is done by pressurizations of condenser by steam leakage is checked ( if any)Standard procedure should flow for Condenser steam pressurizations test

EFFECT OF VACUUM IMPROVEMENT Reduction in heat rate results in several benefits:

The amount of money spent for fuel will be reduced. This lowers the cost of generation of electricity.

The amount of emissions to the environment will be reduced. Reduces the amount of greenhouse gas that is produced.Less Sox,Nox Emission.

Less fuel burned means less ash to be disposed of, and less particulate matter go out of the stack.

Less wear and tear on equipment such as pulverizers, coalpipes and nozzles, CHP equipments.

Also, along with reduced fuel flows, the airflow is reduced, thereby reducing velocities through the boiler, which in turn causes less erosion and reduced fan power consumptionTurbine Later Stage Blade erosion will be avoided.

REFERENCE :-1- Group-C Members2-TMD,O&E3-60 MW TG MANUALS

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