Download - fw heater
Feed water Heating
DMR Panda
UNIT : I 6th July 05
S.No DESCRIPTION UNITS DESIGN TEST DESIGN TEST READINGS:
1 UNIT LOAD MW 200 203 200 2032 FW PRESSURE KSC 190 177.3 190 177.33 FW INLET TEMPERATURE Deg. C 189.33 190.7 212.23 213.94 FW OUTLET TEMPERATURE Deg. C 212.23 213.9 240.08 247.75 SHELL PRESSURE KSC 19.94 20.00 33.88 38.106 EXT STEAM TEMPERATURE Deg. C 473.3 355.87 DRAIN OUTLET TEMP. Deg. C 194.33 195.9 217.23 215.88 DRIP LEVEL mm 218 2669 FW FLOW T/Hr 584 558 584 558
CALCULATIONS:10 SATN. TEMP.OF STEAM Deg. C 211.2 213.9 239.6 247.911 FW I/L ENTHALPY Kcal/kg 194.23 195.51 218.36 220.0312 FW O/L ENTHALPY Kcal/kg 218.36 220.03 248.53 256.9513 EXT ENTHALPY Kcal/kg 813.40 814.15 731.72 743.7114 DRIP O/L ENTHALPY Kcal/kg 197.61 199.28 222.47 220.9315 DRIP I/L ENTHALPY Kcal/kg 222.47 220.93 - -16 DRIP I/L FLOW T/hr 39.41 - -17 TTD (10-4) Deg. C -1.00 -0.02 -0.50 0.1518 DRAIN APPROACH (7-3) Deg. C 5.0 5.2 5.0 1.910 NET HEAT LOAD 10̂ 6 KCAL 14.09 13.68 17.62 20.6111 SUB COOLING (10-7) Deg. C 16.9 17.98 22.3 32.0512 EXtn STEAM FLOW T/hr 22.89 22.25 34.60 39.4113 FW `DT' (4-3) Deg. C 22.9 23.2 27.9 33.8
OBSERVATIONS AND RECOMMENDATIONS:1. HPH-5 & 6 performance is satisfactory.
ENERGY AND EFFICIENCY MANAGEMENT GROUPHP HEATERS PERFORMANCE TEST
HPH 5 HPH 6
Structure
• Physical arrangements
• Construction
• Thermodynamics and other theories
• Performance
Physical Arrangements
General James M. Gavin Plant's units 1 and 2 are 1300 MW capacity each. (1974). With a total generating capacity of 2,600 MW, Gavin Plant ranks as the largest generating station in the state of Ohio. It is located along the Ohio River at Cheshire, Ohio, and has an average daily coal consumption of 25,000 tons at full capacity
UNIT SIZE (MW) Number of Heaters
0 – 50 3 – 550-100 5 or 6100-200 5 - 7Over 200 6 - 8
Typical number of feed water Heaters
No of extraction
Steam extraction stages
Connection to
Extraction steam pr, kg/cm2
Extraction steam temp, 0C
Steam flow T/hr
Ist -HPT 9 HPH-7 30 337 88
2nd -CRH 12 / CRH HPH-6 / Deaerator
26.2 314 77
3rd -IPT 15 HPH-5 / Deaerator
11.96 433 16.2
4th - IPT 18 LPH-4 6.47 368 26
5th – IPT 21 LPH-3 2.78 252 23
6th - IPH 23 LPH-2 1.28 172 28
7th - LPT 25 LPH-1 0.28 40-50 12.6
200 MW LMZ Unit [NTPC- Vindhyachal]
HP Turbine: 12 stages, IP Turbine: 11 stagesLP Turbine: 2 * 3 stages
200 MW LMZ Unit [NTPC- Vindhyachal]
0.91 bar , 45 0C
21 bar Main
Ejector
47.5 0C GSC-I
690CLPH-I GSC--2
1020CLPH-2
1260CLPH-3 LPH-4
FRS HPH 7 HPH-6 HPH-51830C2470C
ECO
2760C
Boiler drum
No of extraction
Steam extraction stages
Connection to
Extraction steam pr, kg/cm2
Extraction steam temp, 0C
Steam flow T/hr
Ist -CRH CRH HPH-6 40 340
2nd -IPH 5 HPH-5 28 390
3rd -IPT 13 Deaerator / TDBFP
22 385
4th – LPT 1 LPH-3 4-5 270
5th - LPH 3 LPH-2 1.3 180
6th - LPT 4 LPH-1 0.2- 0.3 < 120
500 MW LMZ Unit [NTPC- TALCHER-K]
HP Turbine: 12 stages, IP Turbine: 2*16 stagesLP Turbine: 2 * 5 stages
500 MW KWU Unit [NTPC- Talcher-K]
0.91 bar , 45 0C
35 bar GSC
46 0CDC
670CLPH-I
870CLPH-2
1200CLPH-3 LPH-4
FRS HPH-6 HPH-5
210 bar, 2560C
ECO-2
, 206 bar, 3070C
Boiler drum
47 0C
220 bar, 1800C
ECO-1
2950C
Closed feed water heaters with backward cascading
Heater drain cycle with drain injected down stream of heater (forward cascading)
Steam power plant with one open and three closed feedwater heaters
•Which type of arrangements are (a) and (b)?
•What are the merits and limitations of each?
Open type
Feed-water
heaters
Open type Feedwater heaters
Open type Feedwater heaters
Drain System
Normal drain system Emergency drain system
LPH 4 LPH 3 LPH 2
Drip Pump
CEP
DRIP SYSTEM
HPH 5 HPH 6 HPH 7
ECO
HPH > 4 Mpa > LPH
Heater Drains
Construction of Feedwater Heaters
Single tube feedwater heater with floating reverse channel
Low-Pressure, Single-Zone Horizontal Feedwater Heater
Typical straight condensing U tube feedwater heater
Typical two zone [ Condensing, Drain cooler] feed water heater
Typical two zone [ Condensing, Drain cooler] feed water heater
Details of Drain Cooler design
Typical three zone feed water heater
Drain inletExtraction steam inlet
FW outlet
FW inletDrain outlet
H P Heater
Low pressure feedwater heater© Alstom
Typical arrangements of
HP Heater
Desuperheating zone
Condensing zone
Drain cooling zone
HP Feedwater Heater with Tubular Header[660 MW, CEGB]
Desuperheating zone
Condensing zone
Drain cooling zone
Feed water inlet
Feed water outlet
STEAM
Desuperheating zone
Condensing zone
Drain cooling zone
In Plan View of Spirals of Tubes
HP Heater in Vindhyachal 200
MW LMZ Unit
Overall Size Tube Sheet OD 1560 mm , Total Length = 3350 mm
Tube Size 16 Dia. mm x 1.0 mm Thk x 2850 mm Leg Length
Nos. of Tubes 1150 Nos.Weight 5.0 M.Ton (Approx.)
Tube Ad. Brass to BS -2871 Pt.-3 CZ-111
Tubes Sheets SA-516 Gr. 70
HP, LP Feed water Heater
working on the main piping connection welds, trim piping and level control instrumentation on the feed-water heaters.
Level Control Instrumentation
Trim Piping and Insulation
North-dakota – Fixing the Feed water heater
A large tubesheet after drilling and overlay being moved to assembly area
A large tubesheet after drilling and overlay being moved to assembly area
LP Fedwater-1 heater in the condenser Neck
Overall Size Tube Sheet OD 1560 mm , Total Length = 3350 mm
Tube Size 16 Dia. mm x 1.0 mm Thk x 2850 mm Leg Length
Nos. of Tubes 1150 Nos.Weight 5.0 M.Ton (Approx.)
Tube Ad. Brass to BS -2871 Pt.-3 CZ-111
Tubes Sheets SA-516 Gr. 70
For 210 MW, low pressure heater, at Satpura T.P.S. Sarni Project,.
Other Merits of Feedwater Heating?
• A smaller condenser and boiler
• Less steam to pass in the last stages of the turbine, eliminating the difficulties caused by passing large amount of steam
• Better turbine drainage
• Shorter blades at the low pressure part of the turbine?
Thermodynamic Analysis
Effect of no. of feed-water heaters on thermal efficiency of the cycle
Example 4 - SuperheatAn internally reversible Rankine cycle is determined by specifyingAn internally reversible Rankine cycle is determined by specifyinga maximum temperature of 427a maximum temperature of 427o o C, a quality at the turbineC, a quality at the turbinedischarge of 0.9, and a minimum condensing temperature of 21.1discharge of 0.9, and a minimum condensing temperature of 21.1ooC.C.Compare the Compare the thermal efficiencythermal efficiency with that of a with that of a Carnot cycleCarnot cycleoperating between the same temperature limits.operating between the same temperature limits.
ss
bb
aa
ccdd
pd
paTT
Example 4 - Given and computed data
Process HBTU/lbm
WBTU/lbm
QBTU/lbm
a-b 1391 0 1391b-c -441.5 441.5 0c-d -950 0 -950d-a 0.5 -0.5 0Net 0 441
Example 4 - Thermal efficiency
Rankine Thermal efficiencyRankine Thermal efficiency
The Carnot efficiency
316.01391
441
579.081.699
26.29411
H
CC T
T
Key Performance Indicator
• TTD• DCA• TR• PRESSURE DROP
Terminal Temperature Difference
• TTD = TS - FW OUTLET TEMP
TS saturation temperature corresponding to shell pressure
Sensible heat transfer
Latent
heat transfer
Sensible heat transfer
Drain Cooling Zone
Condensing
Zone
Desuper heating Zone
TTD
DC A
Ts
Extn
FW
FW
Drain
Thermal profile in different zones of H P HEATER
High TTD Causes Effects
• Tube fouling/Plugging• Non condensable gases
(Air) blanketing• Flooding
– Tube leakage– Level control
• Low shell pressure• Excessive venting
• Bled steam flow• Heater concerned• Subsequent heater• Turbine steam flow
TTD and Feed Water temp
Feedwater outlet temperature [0C]
Terminal difference [0C]
30-110 2.8110 -148.9 5.6148.9 – 204.4 8.3204.4 – 273.9 11.1
Drain Cooling Approach
• DCA = Drain out let temp - FW inlet temp
Sensible heat transfer
Latent
heat transfer
Sensible heat transfer
Drain Cooling Zone
Condensing
Zone
Desuper heating Zone
TTD
DC A
Ts
Extn
FW
FW
Drain
Thermal profile in different zones of H P HEATER
High DCA Causes Effects
• Tube fouling/Plugging• Low water level
– LCV malfunction
• Drain cooler inlet not submerged
• Bled steam flow• Heater concerned• Subsequent heater• Turbine steam flow
NTHR : Net Turbine Heat Rate
Temperature Rise
• TR= FW outlet temp - FW inlet temp
Low TR Causes Effects
• TTD high • DCA high
• Bled steam flow• Heater concerned• Subsequent heater• Turbine steam flow
Sample Calculation for Feedwater Heater
Plot the points and calculate TTD DCA, TR, Extraction flow
Terminal Temperature (TTD)TTD = t sat – t fw out = 252.8- 251.1 =1.7 0C.
Drain Cooler Apporach Temperature (DCA)DCA = t drains - t fw in = 202.8- 194.3 = 8.5 0C..
Temperature Rise (TR)TR = t fw out – t fw in = 251.1-194.3 = 56.8 0C
Extraction Steam Flow = (Qe) = [Qf (hfw out – hfw in) + Qdrain in (hdrains out- hdrains in)] / (hext – hdrains out )Where:Qf = Feed Flow; Qdrain in = Drain Inlet flow; h fw out = Feed Water Enthalpy at HPH Out.; hfw in = Feed Water Enthalpy at HPH in hdrains out = Enthalpy of Drain Out; hdrains in = Enthalpy of Drain Inhext = Enthalpy of Extraction Steam
751.2* (259.7 – 196.8)+0Qe = ------------------------------------- = 90.2 t/hr (729.4 – 205.95)
Why Performance Testing?
• Prior to outage - Plan maintenance• Post outage - Evaluate effect of work
done• Normal operation
– Trending– HR deviation accounting– Optimize operation
• FW temp 1ºC results in 2.2 kcal/kwhr ( 200 MW) > 3336 Rs/day
1.34 kcal/kwhr (500 MW) > 4299 Rs/day
How Performance Deviates?
• Input parameters / process variables– FW inlet temp/ Extrn Steam inlet Pre & temp
• Deterioration of equipment or system itself– Tube failure, exfoliation, blocking of tubes
• Generic problems– Malfunction of one of its components like DCV
• Design problems– System resistance, size or capacity
HEATER PERFORMANCE DETERIORATION
• Air accumulation• Steam side fouling• Water side fouling• Drainage defects• Parting plane leakage
Air accumulation
• Increased TTD• Possible elevation of steam-to-heater
temperature• Reduced temperature rise of feed water or
condensate.• 0.5 % steam is venting inevitable for good
venting
Steam side fouling
• Progressive increase of TTD• Drain temperature unaffected• Reduced feed water temperature rise• Eventual tube failure due to mechanical
weakening• Accumulation of debris in the heater shell.
Water side fouling
• Gradual increase of TTD.• Oil
– LPT bearing oil through seals– Deposition occurs in HP heaters, worst hit at
highest pressure heater.
Drainage defects
• Damaged flsahbox internals• Reduced orifice opening• Enlarged orifice opening• Heater drain CV/ bypass valve malfunction.
Parting plane leakage
• Short circuiting of FW• TTD high• DCA high• TR less
Feedwater Heater Impact on Thermal Performance
UNIT : I 6th July 05
S.No DESCRIPTION UNITS DESIGN TEST DESIGN TEST READINGS:
1 UNIT LOAD MW 200 203 200 2032 FW PRESSURE KSC 190 177.3 190 177.33 FW INLET TEMPERATURE Deg. C 189.33 190.7 212.23 213.94 FW OUTLET TEMPERATURE Deg. C 212.23 213.9 240.08 247.75 SHELL PRESSURE KSC 19.94 20.00 33.88 38.106 EXT STEAM TEMPERATURE Deg. C 473.3 355.87 DRAIN OUTLET TEMP. Deg. C 194.33 195.9 217.23 215.88 DRIP LEVEL mm 218 2669 FW FLOW T/Hr 584 558 584 558
CALCULATIONS:10 SATN. TEMP.OF STEAM Deg. C 211.2 213.9 239.6 247.911 FW I/L ENTHALPY Kcal/kg 194.23 195.51 218.36 220.0312 FW O/L ENTHALPY Kcal/kg 218.36 220.03 248.53 256.9513 EXT ENTHALPY Kcal/kg 813.40 814.15 731.72 743.7114 DRIP O/L ENTHALPY Kcal/kg 197.61 199.28 222.47 220.9315 DRIP I/L ENTHALPY Kcal/kg 222.47 220.93 - -16 DRIP I/L FLOW T/hr 39.41 - -17 TTD (10-4) Deg. C -1.00 -0.02 -0.50 0.1518 DRAIN APPROACH (7-3) Deg. C 5.0 5.2 5.0 1.910 NET HEAT LOAD 10̂ 6 KCAL 14.09 13.68 17.62 20.6111 SUB COOLING (10-7) Deg. C 16.9 17.98 22.3 32.0512 EXtn STEAM FLOW T/hr 22.89 22.25 34.60 39.4113 FW `DT' (4-3) Deg. C 22.9 23.2 27.9 33.8
OBSERVATIONS AND RECOMMENDATIONS:1. HPH-5 & 6 performance is satisfactory.
ENERGY AND EFFICIENCY MANAGEMENT GROUPHP HEATERS PERFORMANCE TEST
HPH 5 HPH 6
EEMG HPH PERFORMANCE TEST REPORT RAMAGUNDAMUNIT IV DATE: 9-Jul-05S.No DESCRIPTION UNITS DESIGN HPH 5 HPH 5A HPH 5B DESIGN HPH 6 HPH 6A HPH 6B
1 UNIT LOAD MW 500 5002 FW PRESSURE KSC 218 203.4 203.4 218.0 202.8 202.83 FW INLET TEMPERATURE Deg. C 166.7 173.5 173.6 208.1 216.2 212.74 FW OUTLET TEMPERATURE Deg. C 208.1 216.2 212.7 253.7 257.1 256.95 DRIP O/L FLOW (INDICATION) T/Hr 122.35 148 135 45.27 134.9 126.06 EXT STEAM PRESSURE KSC 18.63 21.00 19.89 43.00 45.1 45.07 EXT STEAM TEMPERATURE Deg. C 429 411.5 411.5 342.6 350.6 350.68 DRAIN OUTLET TEMP. Deg. C 171.5 183.4 181.4 212.9 219.8 219.59 DRIP LEVEL mm -10 -6 -1 510 FW FLOW T/Hr 770 771.0 771.0 770.0 771.0 771.0
1 SATN. TEMP.OF STEAM Deg. C 207.8 216.3 213.6 253.4 257.7 257.62 FW I/L ENTHALPY Kcal/kg 171.2 178.0 178.1 214.2 222.7 219.03 FW O/L ENTHALPY Kcal/kg 214.2 222.7 219.0 263.8 267.6 267.44 EXT ENTHALPY Kcal/kg 791.3 781.5 781.9 733.5 736.8 736.95 DRIP O/L ENTHALPY Kcal/kg 173.5 186.0 183.9 217.8 225.4 225.06 DRIP I/L ENTHALPY Kcal/kg 217.8 225.4 225.0 - - -7 DRIP I/L FLOW T/hr 67.7 72.9 - - -8 TTD Deg. C -0.3 0.1 0.9 -0.3 0.6 0.79 DRAIN APPROACH Deg. C 4.8 9.9 7.8 4.8 3.6 6.810 NET HEAT LOAD 10̂ 6 KCAL 33.146 34.49 31.53 38.17 34.61 37.3111 SUB COOLING Deg. C 32.9 32.2 37.91 38.0712 EXtn STEAM FLOW T/hr 48.3 57.91 52.72 74.05 67.66 72.8913 FW `DT' Deg. C 41.4 42.7 39.1 45.6 40.9 44.2
PREVIOUS TEST RESULTS 9/5/051 TTD Deg. C -0.3 0.2 1.2 -0.3 0.3 0.42 DRAIN APPROACH Deg. C 4.8 7.6 8.3 4.8 6.3 7.83 NET HEAT LOAD 10̂ 6 KCAL 33.1 31.8 31.2 38.2 36.3 37.44 SUB COOLING Deg. C 33.1 32.7 38.2 38.15 EXtn STEAM FLOW T/hr 48.3 52.8 52.1 74.1 71.9 74.06 FW `DT' Deg. C 41.4 40.5 39.8 45.6 44.2 45.5
OBSERVATIONS AND RECOMMENDATIONS:1. HPH-5B FW DT is less and DCA is more.Its performance is to be observed.
CALCULATIONS:
513513
Heat transferred
• Q= U* A* LMTD• LMTD = (ITD-TTD) / Loge (ITD/TTD)
• Heat Balance Extrn steam flow*( h ext – h drainout) = Qfw *( h fwout- h fwin) - Qdrainin *(h drainout- h drainin)
Determine the condition at Pt 6 and on T-S diagramme, show all the points? The pump has isentropic efficiency of 80%.
Why NRVs are provided in Steam extraction lines ?
• When the turbine trips, the reheat stop and intercept valves close rapidly. The closing of the turbine valves causes a momentary vacuum that moves through the turbine stages. This vacuum tends to pull the extraction steam back into the turbine and decrease the extraction stage pressure. As a result, the heater shell pressure drops, causing a rapid decrease in the saturation temperature in the heater shell. With a supply of hot water in the heater shell, the water flashes to steam and attempts to flow back to the turbine extraction. This influx of energy back into the turbine causes a rapid overspeed condition.
• As a result, a non-return valve is installed in each extraction line that automatically closes the line to prevent steam from re-entering the turbine. In some cases, two non-return valves are installed in series. The non-return valve is a check-type valve because a gate valve could not close fast enough.
• When heaters are installed in the upper part of the condenser, there is no room for a non-return valve. As a result, the quantity of water held in the shell is limited, and an anti-flash baffle may be installed above the water level to restrict the flow of any flashing steam.
Drain System- Alarm & Interlocks
• High heater water level - alarm
• High-high heater water level – •actuation of check valves, • closing of extraction line isolation valve,•actuation of bypass
• Automatic switch to emergency drain system when the heater that the condensate is flowing into, is shut off or is at too low a pressure at low load operation
• Automatic limitation of load when strings or feedwater heaters are shut off and the feedwater heater is not designed for the corresponding operation
Automatic Extraction
100 00C 75 00C 50 00C
TTD
Heat Capacity in %
15
5
100 %%200 %% 300 %%