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Supercritical Boiler: Introduction, Operation, and Advantages

This presentation provides an overview of supercritical boiler technology, including its operation, key components, and advantages. It covers topics such as the rankine cycle, nucleate boiling, water density, water wall design, materials, steam-water cycle chemistry, and the impact on efficiency and emissions. The challenges of supercritical technology are also discussed.

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Supercritical Boiler: Introduction, Operation, and Advantages

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  1. WELCOME TO PRESENTATION ON SUPERCRITICAL BOILER By OPERATION TEAM APML,TIRODA

  2. Introduction to Supercritical Technology What is 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 oC.

  3. Rankine 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 > Condensing

  4. Rankine Cycle Supercritical Unit • 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

  5. VARIATION OF LATENT HEAT WITH PRESSURE

  6. Departure from Nucleate Boiling Nucleate boiling is a 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 40C to 300C. WATER DENSITY STEAM 175 224 PRESSURE(ksc)

  7. Supercritical Boiler Water Wall Rifle Tube And Smooth Tube

  8. Natural Circulation Vs. Once Through System

  9. To HP Turbine 5710C To IP Turbine 5690C Mixer Header 5340C 4230C 5260C 4620C Separator FRH 4730C FSH Platen Heater LTSH 4430C From CRH Line 3260C LTRH 3240C NRV 2830C From FRS Line 2800C Economizer Phase 1 Economizer Phase 2 Boiler Recirculation Pump Bottom Ring Header

  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. Difference of Subcritical(500MW) and Supercritical(660MW)

  12. COMPARISION OF SUPER CRITICAL & SUB CRITICAL

  13. Continue..

  14. Continue..

  15. Water Wall Design

  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.

  17. SPIRAL VS VERTICAL WALL VERTICAL WALL 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 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

  18. Furnace Arrangement SPIRAL TYPE VERTICAL TYPE

  19. Supercritical Sliding Pressure Boiler Water Wall Design Comparison of Vertical Wall and Spiral Wall

  20. Vertical water walls Spiral water walls Ash accumulation on walls

  21. Super Critical Boiler Materials

  22. Advanced Supercritical Tube Materials (300 bar/6000c/6200c)

  23. Material Comparison

  24. Steam Water Cycle Chemistry Controls

  25. Advantages of SC Technology 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

  26. ECONOMY Higher Efficiency (η%) • Less fuel 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

  27. Increase of Cycle Efficiency due to Steam Parameters

  28. Subcritical Supercritical Plant Efficiency, %* Plant Efficiency, % Fuel Consumption/Total Emissions including CO2 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 Sub. vs. Supercritical Cycle Impact on Emissions

  29. 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.

  30. THANK YOU

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