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INCREASE OF CYCLE EFFICIENCY DUE TO
STEAM PARAMETERS
300
241
175 538 / 538
538 / 566
566 / 566
580 / 600
600 / 620
6,77
5,79
3,74
5,74
4,81
2,76
4,26
3,44
1,47
3,37
2,64
0,75
2,42
1,78
0
0
1
2
3
4
5
6
7
8
9
10
HP / RH outlet temperature [deg. C]Pressure [bar]
Increase of efficiency [%]](https://image.slidesharecdn.com/super-criticalboiler-160309140412/85/Super-critical-boiler-29-320.jpg)
Uploaded byAshvani Shukla
Super critical boiler
The document discusses the principles and advantages of supercritical boiler technology, highlighting its operational efficiency, lower fuel consumption, and reduced emissions compared to subcritical systems. Key differences between supercritical and subcritical cycles, such as water circulation, material requirements, and heat transfer mechanisms are outlined. Additionally, it addresses challenges in supercritical technology, such as stringent water chemistry control and maintenance difficulties.
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Super critical boiler
- 1.
- 2. 2 INTRODUCTION TO SUPERCRITICAL TECHNOLOGY Whatis Supercritical Pressure ? Critical point in water vapour cycle is a thermodynamic state where there is no clear distinction between liquid and gaseous state of water. Water reaches to this state at a critical pressure above 22.1 MPa and 374 o C.
- 3. RANKIN CYCLE SUBCRITICAL UNIT 1 - 2 > CEP work 2 - 3 > LP Heating 3 - 4 > BFP work 4 - 5 > HP Heating 5 – 6 > Eco, WW 6 – 7 > Superheating 7 – 8 > HPT Work 8 – 9 > Reheating 9 – 10 > IPT Work 10–11 > LPT Work 11 – 1 > Condensing3
- 4. RANKINE CYCLE SUPERCRITICALUNIT 1 - 2 > CEP work 2 – 2s > Regeneration 2s - 3 > Boiler Superheating 3 – 4 > HPT expansion 4 – 5 > Reheating 5 – 6 > IPT & LPT Expansion 6 – 1 > Condenser Heat rejection 4
- 5. 5 AbsoluteAbsolute PressurePressure (Bar)(Bar) SaturationSaturation TemperatureTemperature ((oo C)C) Latent HeatLatent Heat (KJ/Kg.)(K J/Kg.) 5050 150150 200200 221221 264264 342342 366366 374374 16401640 10041004 592592 00 VARIATION OF LATENT HEAT WITH PRESSURE
- 6. NUCLEATE BOILING ISA TYPE OF BOILING THAT TAKES PLACE WHEN THE SURFACE TEMP IS HOTTER THAN THE SATURATED FLUID TEMP BY A CERTAIN AMOUNT BUT WHERE HEAT FLUX IS BELOW THE CRITICAL HEAT FLUX. NUCLEATE BOILING OCCURS WHEN THE SURFACE TEMPERATURE IS HIGHER THAN THE SATURATION TEMPERATURE BY BETWEEN 40 C TO 300 C. 6 Departure from Nucleate Boiling DENSITY WATER STEAM 175 224
- 7. 7 Supercritical Boiler WaterWall Rifle Tube And Smooth Tube
- 8. NATURAL CIRCULATION VS.ONCE THROUGH SYSTEM 8
- 9. From CRH Line FromFRS Line Boiler Recirculation Pump Economizer Phase 1 Economizer Phase 2 LTRH LTSH 4430 C FRH Platen Heater Mixer Header FSH To HP Turbine To IP Turbine Separator Bottom Ring Header 2830 C 3260 C 4230 C 4730 C 4620 C 5340 C 5260 C 5710 C 5690 C 3240 C 2800 C NRV
- 10. 10 FEED WATER CONTROL In Drum type Boiler Feed water flow control by Three element controller 1.Drum level 2.Ms flow 3.Feed water flow. Drum less Boiler Feed water control by 1.Load demand 2.Water/Fuel ratio(7:1) 3.OHD(Over heat degree)
- 11. 11 DIFFERENCE OF SUBCRITICAL(500MW) ANDSUPERCRITICAL(660MW)
- 12. COMPARISION OF SUPERCRITICAL & SUB CRITICAL DESCRIPTION SUPERCRITICAL (660MW) SUB-CRITICAL (500MW) Circulation Ratio 1 Once-thru=1 Assisted Circulation=3-4 Natural circulation= 7-8 Feed Water Flow Control -Water to Fuel Ratio (7:1) -OHDR(22-35 O C) -Load Demand Three Element Control -Feed Water Flow -MS Flow -Drum Level Latent Heat Addition Nil Heat addition more Sp. Enthalpy Low More Sp. Coal consumption Low High Air flow, Dry flu gas loss Low High
- 13. CONTINUE.. 13 DESCRIPTION SUPERCRITICAL (660MW) SUB-CRITICAL (500MW) Coal &Ash handling Low High Pollution Low High Aux. Power Consumption Low More Overall Efficiency High (40-42%) Low (36-37%) Total heating surface area Reqd Low (84439m2 ) High (71582m2 ) Tube diameter Low High
- 14. CONTINUE.. DESCRIPTION SUPERCRITICAL (660MW) SUB-CRITICAL (500MW) Material /Infrastructure (Tonnage) Low 7502 MT High 9200 MT Start up Time Less More Blow down loss Nil More Water Consumption Less More 14
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- 16. WATER WALL ARRANGEMENT Bottom spiral & top vertical tube furnace arrangement Once through design feature is used for boiler water wall design The supercritical water wall is exposed to the higher heat flux Spiral tube wall design (wrapped around the unit) with high mass flow & velocity of steam/water mixture through each spiral Higher mass flow improves heat transfer between the WW tube and the fluid at high heat flux. 16
- 17. 17 SPIRAL VS VERTICALWALL VERTICAL WALL Less ash deposition on wall Less mass flow More number of tubes More boiler height for same capacity No uniform heating of tubes and heat transfer in all tubes of WW SPIRAL WALL More ash deposition More fluid mass flow Less number of tubes Less boiler height Uniform heat transfer and uniform heating of WW tubes
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- 19. 19 Supercritical Sliding Pressure BoilerWater Wall Design Comparison of Vertical Wall and Spiral Wall
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- 21. 21 Ash accumulation onwalls Vertical water walls Spiral water walls
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- 23. 23 Advanced Supercritical TubeMaterials (300 bar/6000 c/6200 c)
- 24. 24 MATERIAL COMPARISON DescriptionDescription 660MW660 MW 500 MW500 MW Structural SteelStructural Steel Alloy SteelAlloy Steel Carbon SteelCarbon Steel Water wallWater wall T22T22 Carbon SteelCarbon Steel SH CoilSH Coil T23, T91T23, T91 T11, T22T11, T22 RH CoilRH Coil T91,Super 304T91,Super 304 HH T22, T91,T11T22, T91,T11 LTSHLTSH T12T12 T11T11 EconomizerEconomizer SA106-CSA106-C Carbon SteelCarbon Steel Welding Joints (Pressure Parts)Welding Joints (Pressure Parts) 42,000 Nos42,000 Nos 24,000 Nos24,000 Nos
- 25. 25 Steam Water Cycle ChemistryControls
- 26. 26 S.S. No.No. ParameterParameter Sub CriticalSubCritical Super CriticalSuper Critical 11 Type of BoilerType of Boiler waterwater treatmenttreatment LP and HP dosing. OrLP and HP dosing. Or All Volatile TreatmentAll Volatile Treatment (Hydrazine + Ammonia)(Hydrazine + Ammonia) No HP dosingNo HP dosing Combined water treatment (CWT).Combined water treatment (CWT). 22 SilicaSilica < 20 ppb in feed water and steam,< 20 ppb in feed water and steam, < 250 ppb in boiler drum< 250 ppb in boiler drum Standard value <15 ppb in the cycleStandard value <15 ppb in the cycle Expected value <10 ppb in the cycleExpected value <10 ppb in the cycle 33 pHpH 9.0 - 9.5 for feed, steam &9.0 - 9.5 for feed, steam & condensate,condensate, 9.09.0 –– 10.0 for Boiler drum10.0 for Boiler drum 9.09.0 –– 9.6 for AVT(All volatile treatment)9.6 for AVT(All volatile treatment) 8.08.0 –– 9.0 for CWT(Combine water9.0 for CWT(Combine water treatment)treatment) 44 DissolvedDissolved Oxygen (DO)Oxygen (DO) < 7 ppb for feed.< 7 ppb for feed. < 7 ppb for feed in case of AVT< 7 ppb for feed in case of AVT 3030 –– 150 ppb for feed in case of CWT150 ppb for feed in case of CWT 55 Cation (HCation (H++ )) ConductivityConductivity <0.20<0.20 µµS/cm in the feed & steamS/cm in the feed & steam cyclecycle Standard value <0.15Standard value <0.15 µµS /cm in the cycleS /cm in the cycle Expected value- <0.10Expected value- <0.10 µµS /cm in the cycleS /cm in the cycle 66 (CPU)(CPU) CPU is optionalCPU is optional CPU is essential for 100% flow.CPU is essential for 100% flow. 77 Silica and TDSSilica and TDS controlcontrol By maintaining feed water qualityBy maintaining feed water quality andand By operating CBDBy operating CBD Blow down possible till separators areBlow down possible till separators are functioning (upto 30% load).functioning (upto 30% load).
- 27. 27 ADVANTAGES OF SCTECHNOLOGY I ) Higher cycle efficiency means Primarily – less fuel consumption – less per MW infrastructure investments – less emission – less auxiliary power consumption – less water consumption II ) Operational flexibility – Better temp. control and load change flexibility – Shorter start-up time – More suitable for widely variable pressure operation
- 28. 28 ECONOMY Higher Efficiency (η%) •Lessfuel input. •Low capacity fuel handling system. •Low capacity ash handling system. •Less Emissions. Approximate improvement in Cycle Efficiency Pressure increase : 0.005 % per bar Temp increase : 0.011 % per deg K
- 29. 29 INCREASE OF CYCLEEFFICIENCY DUE TO STEAM PARAMETERS 300 241 175 538 / 538 538 / 566 566 / 566 580 / 600 600 / 620 6,77 5,79 3,74 5,74 4,81 2,76 4,26 3,44 1,47 3,37 2,64 0,75 2,42 1,78 0 0 1 2 3 4 5 6 7 8 9 10 HP / RH outlet temperature [deg. C]Pressure [bar] Increase of efficiency [%]
- 30. 30 Sub. vs. SupercriticalCycle Impact on Emissions Plant Efficiency, %* Plant Efficiency, % Fuel Consumption/Total Emissions including CO2 Subcritical Supercritical 34 - 37 37 - 41 Plant Efficiency, Btu / kw-hr 10,000 - 9,200 9,200 - 8,300 34% Base 37% Base-8% 41% Base-17% * HHV Basis
- 31. 31 CHALLENGES OF SUPERCRITICAL TECHNOLOGY Water chemistry is more stringent in super critical once through boiler. Metallurgical Challenges More complex in erection due to spiral water wall. More feed pump power is required due to more friction losses in spiral water wall. Maintenance of tube leakage is difficult due to complex design of water wall. Ash sticking tendency is more in spiral water wall in comparison of vertical wall.
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