A Verification on Design Performance of 300MW Class CFB Boiler

Transcription

1 A Verification on Design Performance of 300MW Class CFB Boiler Jae-Sung Kim, Jong-Min Lee, Dong-Won Kim October 29, 2010 Korea Electric Power Research Institute 1

2 Contents 1. Introduction of the 300MW class CFB boiler design 2. Steam & design coal conditions 3. Heat and mass balance calculations 4. Calculation results 5. Summary 2

3 Motivation and Objectives 1. First construction of 340MW Yeosu CFB boiler in Korea 2. Necessity of a verification on the boiler design & performance 3. Evaluation of design & performance characteristics of the CFB boiler 4. Development of heat & mass balance calculation modules As a reverse engineering 3

4 Introduction of the 300MW class CFB Boiler design 4

5 Boiler outline SCR AH EP 5

6 Furnace Side view Height : 41,500 Width : 34,010 Depth : 8,138 Bed Depth : 4,069 Cyclone Height( 長 ) : 26,031 Cyclone Height( 短 ): 16,055 Cyclone Diameter : 6,854 Return leg : Plane view Evap. Division wall : 2 Total Wing Wall : 31 Evap. WW : 4 SH WW : 27 Rear view Cyclone: 4 Return leg: 4 6

7 Furnace, Division Wall, Wing Wall 34m 8.1m 8.1m 2.5m 2.7m 3.5m Furnace Height : 42m Width : 34m Depth : 8.1m Bed Depth : 4.1m Division Wall Evaporator Height : 35m Depth : 3.5m Number : 2 42m 21 m 23m 35m Wing Wall Superheater Height : 21m Depth : 2.5m Pitch : 1.1m Number : 27 Wing Wall Evaporator Height : 23m Depth : 2.7m Pitch : 1.1m Number : 4 6m 4.1m 7

8 Cyclone arrangement 34m 8.13m 8.06m 1.37m 1.43m 7.45m 7.45m 8

9 Cyclone specification R

10 Distributor Fluidized bed 34m 4.1m Ash Drain Grid Nozzle Arrangement Grid Nozzle 124.8mm 180mm Φ42.2mm 124.8mm 100mm ⅹ95 ⅹ95 ⅹ32 176mm ⅹ31 10

11 Return Leg

12 Furnace model 12

13 Steam & design coal conditions 13

14 Water/steam circuitry In Furnace T( ) P(kg/cm 2 g) Drum Cyclone Crossover duct Convection cage SH Ⅰ WW SHⅡ WW SHⅢ RH Ⅰ Furnace Walls (Division Wall Evaporator) Economizer Ⅱ RHⅡ Economizer Ⅰ HP-Heaters Feed Water Pump Feed tank 14

15 Steam conditions Steam condition BMCR MGR NR 75%MGR 50%MGR 30%MGR SH outlet steam flow 1,000kg/hr SH outlet steam temperature, SH outlet steam pressure, kg/cm 2 g RH outlet steam flow 1,000kg/hr RH outlet steam Temperature, RH steam pressure kg/cm 2 g Final Feedwater temperature, 1,025 1,025 1,

16 Design coal analysis Ultimate Analysis (Air Dry Basis) Design Coal Carbon(%,wt) 69.8 Hydrogen(%,wt) 4.9 Nitrogen(%,wt) 1.0 Sulfur(%,wt) 0.3 Oxygen(%,wt) 21.0 Ash(%,wt) TGA Subbituminous Bituminous Anthracite Design Coal Proximate Analysis (Air dry Basis) Design Coal Range Coal Moisture(%,wt) Volatile matter(%,wt) Fixed Carbon(%,wt) Ash(%,wt) ~18.7 M/M o Temperature( o C) 16

17 Schematic diagram of supplied fuel & air Limestone silo Fluidizing Air Blowers Primary Air Fans Coal silo A Coal silo B Upper lever SA 22 nozzles Bed Material Make up Lower level SA 26 nozzles Secondary Air Fans 17

18 Conditions of supplied fuel & air BMCR MGR 75%MGR 50%MGR 30%MGR Coal (t/h) Limestone (t/h) Excess air Primary air (t/h) Secondary air (t/h) 2ndary air ratio

19 Heat and mass balance calculations 19

20 Methods of heat and mass balance calculation Combustion calculations Selection of calculations conditions Basic equation of heat balance Calculation of enthalpy of gas phase Input and Output in a furnace Heat balance equations in a furnace Calculation of flue gas temperature 20

21 Flue gas composition BMCR NR MGR 75%MGR 50%MGR 30%MGR Excess air(%) CO 2 (volume %) O 2 (volume %) N 2 (volume %) SO 2 (volume %) H 2 O(volume %)

22 Selections of calculation conditions Item unit Symbol On literature Selection Excess air - α fu 1.1~ Primary air ratio % x 50~75 56 Dense zone combustion rate - δ 0.75~ Chemical incomplete combustion loss % q 3 0~1 0.5 Unburned carbon loss % q 4 2~6 6 Carbon contents of fly ash % C f,a <10 8 王敦恩 et al., 工业锅炉设计计算方法, 中国标准出版社,

23 Basic equation of heat balance Simple heat balance equation Q Q Q abs in out Determination of control volume Every heat exchanger had a control volume except of a furnace Furnace was divided into a dense zone and a dilute zone Q abs (Total heat absorbed in a control volume) Q in (Total heat input) Control Volume Q out (Enthalpy of flue gases leaving the control volume) Prabir Basu, Cen Kefa, Louis Jestin, Boiler and Burners, Springer-Verlag New York,

24 Calculation of enthalpy of gas phase Enthalpy calculation of gas phase Enthalpy of flue gas or supplied air N T i I gas C T p, idt 0 i 1 m total Polynomial expression of Specific heat m C a bt ct dt p 2 3 Gas species a b c d (1) CO E-09 (2) H2O E-09 (3) SO E-09 (4) O E-09 (5) Ar E-09 (6) N E-09 (7) CO E-09 (8) Air E-09 Yunus A. Cengel and Michael A. Boles, Thermodynamics - An Engineering Approach, Fifth Edition in SI Unit, McGraw-Hill,

25 Input and Output in a furnace Recycled solid, Flue gas Dilute zone Heat absorbed in dilute zone(q w ) Enthalpy of flue gas and solid(i fe ) 2ndary air Sensible heat of 2ndary air(1-x)αi ai Recycled solid, Flue gas of Dense phase Enthalpy of gas & solid leaving the dense zone(i do ) Heat absorbed in dense zone(q m ) Fuel, Recycled solid,primary air Dense zone Total heat input(qi) Sensible heat of primary air(xαi ai ) Enthalpy of recycled solid(i rs ) 程乐鸣, 岑可法, 倪明江, 骆仲泱, 循环流化床锅炉炉膛热力计算, 中国电机工程学报, Vol.22 No.12 Dec

26 Heat balance equations in a furnace Dilute zone Heat absorbed in dilute zone(q w ) Enthalpy of flue gas and solid(i fe ) Q Q I w dilute fe Sensible heat of 2ndary air(1-x)α fu I ai Heat input into Dilute zone(q dilute ) Q I Q (1 ) (1 x) I dilute do i fu air Enthalpy of gas & solid leaving the dense zone(i do ) Heat absorbed in dense zone(q m ) Q Q I m dense do Dense zone Total heat input(qi) Sensible heat of primary air(xαi ai ) Enthalpy of recycled solid(i rs ) Heat input into Dense zone(q dense ) Q Q x I I dense i fu air rs 程乐鸣, 岑可法, 倪明江, 骆仲泱, 循环流化床锅炉炉膛热力计算, 中国电机工程学报, Vol.22 No.12 Dec

27 Calculation of exit gas temperature Assumption of exit gas temperature Heat transfer calculation Difference between heat input and output Calculation of temperature with polynomial expression of specific heat Iteration until the same of previous exit gas temperature 27

28 Results Furnace Wing Wall Superheater Cyclone, Cross over duct, Convection cage Backpass Reheater, Primary Superheater Backpass Economizer 28

29 Furnace heat & mass balance Separation between Dense zone and Dilute zone Assumption of combustion rate, unburned carbon, heat transfer Dilute Zone INPUT Dense Zone Heating value of coal [kw] Sensible heat of coal [kw] 1728 Sensible heat of primary air [kw] OUTPUT Total heat input [kw] Unburned carbon loss [kw] 1206 Sensible heat of ash [kw] 533 Moisture heat loss [kw] 5054 Sensible heat of dense zone exit gas [kw] Total heat output [kw] INPUT Sensible heat of dense zone exit gas [kw] Heating value of coal [kw] Sensible heat of 2ndary air [kw] Total heat input [kw] OUTPUT Moisture heat loss in 2ndary air [kw] 3961 Chemical incomplete combustion loss [kw] 2280 Heat transfer [kw] Sensible heat of flue gas [kw] Total heat output [kw] Furnace exit gas temperature [ ]

30 Wing wall superheater Furnace(Wing Wall) Secondary Superheater Inlet gas temperature 871 Operation condition Out gas temperature 871 Operation condition Flue gas flow rate Nm3/h 2,494 Imported(Proximate) Inlet steam temperature 386 Operation condition Enthalpy of inlet steam kj/kg 2,851 Steam Table Outlet steam temperature 471 Operation condition Enthalpy of outlet steam kj/kg 3,193 Steam Table Steam flow rate kg/h 1,025,000 Operation condition Heat duty in secondary superheater kj/h 350,750,366 Furnace(Wing Wall) Final Superheater Inlet gas temperature 871 Operation condition Out gas temperature 871 Operation condition Flue gas flow rate Nm3/h 1,127,870 Imported(Proximate) Inlet steam temperature 453 Operation condition Enthalpy of inlet steam kj/kg 3,133 Steam Table Outlet steam temperature 541 Operation condition Enthalpy of outlet steam kj/kg 3,403 Steam Table Steam flow rate kg/h 1,025,000 Operation condition Heat duty in final superheater kj/h 277,178,818 30

31 Cyclone, Cross Over Duct, Convection Cage Cyclone Inlet gas temperature 871 Operation condition Out gas temperature 853 Operation condition Flue gas flow rate Nm3/h 1,244,868 Imported(Proximate) Inlet steam temperature 358 Operation condition Enthalpy of inlet steam kj/kg 2,642 Steam Table Outlet steam temperature 366 Operation condition Enthalpy of outlet steam kj/kg 2,718 Steam Table Steam flow rate kg/h 1,025,000 Operation condition Heat duty in cyclone kj/h 77,914,450 Cross over duct Inlet gas temperature 853 Operation condition Out gas temperautre 825 Operation condition Flue gas flow rate Nm3/h 1,244,868 Imported(Proximate) Inlet steam temperature 366 Operation condition Enthalpy of inlet steam kj/kg 2,718 Steam Table Outlet steam temperature 369 Operation condition Enthalpy of outlet steam kj/kg 2,741 Steam Table Steam flow rate kg/h 1,025,000 Operation condition Heat duty in COD superheater kj/h 22,847,510 Convection cage Inlet gas temperature 825 Operation condition Out gas temperautre 777 Operation condition Flue gas flow rate Nm3/h 1,244,868 Imported(Proximate) Inlet steam temperature 369 Operation condition Enthalpy of inlet steam kj/kg 2,741 Steam Table Outlet steam temperature 376 Operation condition Enthalpy of outlet steam kj/kg 2,794 Steam Table Steam flow rate kg/h 1,025,000 Operation condition Heat duty in CC kj/h 54,876,047 31

32 Backpass - RH, SH Final Reheater Inlet gas temperature 777 Operation condition Out gas temperature 642 Operation condition Flue gas flow rate Nm3/h 1,244,868 Imported(Proximate) Inlet steam temperature 420 Operation condition Enthalpy of inlet steam kj/kg 3,010 Steam Table Outlet steam temperature 541 Operation condition Enthalpy of outlet steam kj/kg 3,403 Steam Table Steam flow rate kg/h 821,500 Operation condition Heat duty in final Reheater kj/h 322,858,983 Primary Reheater Inlet gas temperature 642 Operation condition Out gas temperature 513 Operation condition Flue gas flow rate Nm3/h 1,244,868 Imported(Proximate) Inlet steam temperature 309 Operation condition Enthalpy of inlet steam kj/kg 3,016 Steam Table Outlet steam temperature 481 Operation condition Enthalpy of outlet steam kj/kg 3,413 Steam Table Steam flow rate kg/h 821,500 Heat duty in primary reheater kj/h 326,281,726 Primary Superheater Inlet gas temperature 513 Operation condition Out gas temperautre 450 Operation condition Flue gas flow rate Nm3/h 3,016 Imported(Proximate) Inlet steam temperature 376 Operation condition Enthalpy of inlet steam kj/kg 3,177 Steam Table Outlet steam temperature 392 Operation condition Enthalpy of outlet steam kj/kg 3,212 Steam Table Steam flow rate kg/h 1,025,000 Heat duty in primary superheater kj/h 35,971,046 32

33 Backpass - Economizer Secondary Economizer Inlet gas temperature 450 Operation condition Out gas temperautre 344 Operation condition Flue gas flow rate Nm3/h 1,244,868 Imported(Proximate) Inlet water temperature 256 Operation condition Enthalpy of inlet steam kj/kg 1,116 Steam Table Outlet water temperature 304 Operation condition Enthalpy of outlet steam kj/kg 1,354 Steam Table Steam flow rate kg/h 1,076,250 Heat duty in Secondary Eco kj/h 255,875,764 Primary Economizer Inlet gas temperature 344 Operation condition Out gas temperautre 269 Operation condition Flue gas flow rate Nm3/h 1,244,868 Imported(Proximate) Inlet water temperature 229 Operation condition Enthalpy of inlet steam kj/kg 989 Steam Table Outlet water temperature 256 Operation condition Enthalpy of outlet steam kj/kg 1,115 Steam Table Steam flow rate kg/h 1,076,250 Heat duty in Primary Economizer kj/h 135,505,607 33

34 Heat calculation results Heat duty Heat transfer Comparison of temperature between design value and calculation 34

35 Heat duty and Heat transfer calculations Heat duty calculation from steam condition Using an overall heat transfer coefficient(u) with Log Mean Temperature Difference( LMTD) Q=UA LMTD Unit furnace 2ry SH Final SH cyclone Cross over duct Convectio n cage Final RH Primary RH Primary SH 2ry Eco Primary Eco Inlet gas temperature Outlet gas temperature Inlet water/steam temp Enthalpy kj/kg Outlet water/steam temp Enthalpy kj/kg LMTD Heat duty kw Heat absorbtion GJ/h Heat absorbtion Gcal/h Heat absorbtion rate kcal/m 2 h Calculated area m Heat transfer coefficient W/m 2 K

36 Heat duty and Heat transfer 400 Heat Duty(MW) Heat transfer coefficient(w/m 2 K)

37 Comparison of temperature Furnace Furnace Cyclone Convection cage Final RH Primary RH Primary SH 2ndary Eco. Primary Eco. AH Calculation Design value Δt Calculation Design value C 0 Furnace Cyclone Convection cage Final RH Primary RH Primary SH 2ndary Eco. Primary Eco. AH 37

38 Summary 1. Get the Input conditions from Technical Specification (Performance & Technical Data) and drawing 2. Establishing Heat balance equation of each control volume 3. Calculating heat and mass balance 4. Acquiring results of heat transfer coefficients, heat duty, exit gas temperature and so on 38

39 39