Design and commissioning of a 1MW th pilot-scale oxy-fuel circulating fluidized bed with high oxygen concentration

Transcription

1 Design and commissioning of a 1MW th pilot-scale oxy-fuel circulating fluidized bed with high oxygen concentration LI Haoyu, LI Shiyuan*, REN Qiangqiang,Li Wei, LIU Jingzhang Institute of Engineering Thermophysics (IET) Chinese Academy of Sciences (CAS) 11 Beisihuanxi Road, Beijing, China

2 Content Oxy-fuel CFB activities at IET-CAS Introduction of 1MW th pilot scale oxy-cfbc facility Experimental results and discussion Conclusion/Future work 2

3 Background Oxy-fuel CFB is a promising CCS technology in China. The total power capacity of CFB boiler is more than 10% of total Chinese coal fire power installation. IET-CAS has researched CFB combustion for nearly 30 years. Main advantages of oxy-fuel CFB combustion Efficient heat transfer and uniform heat flux. The established CFB advantages also exist in oxy-fuel CFB combustion: low furnace temperatures, hot circulating solids, long solid residence time, etc. Reduce boiler size (~50%) using high O 2 concentration. Multi-fuel capability (coal, petroleum coke, biomass). NOx and SOx reduction without back-end cleaning. Good fuel burnout and sorbent utilization. The same boiler can be operated in air combustion or oxygen combustion mode with CCS. 3

4 Oxy-fuel CFB activities at IET-CAS Work on oxy-fuel CFB combustion at high oxygen concentrations within the frame of the CAS "Strategic Priority Research Program Demonstration of Key Technologies for Clean and Efficient Utilization of Low-rank Coal (funded by Chinese Academy of Science, ) Project: Oxy-fuel circulating fluidized bed combustion technology Research on 1MWth pilot plant facility Main research of IET-CAS Build the test facilities for different scale: from bench scale to pilot plant (~MW th full chain) Study of combustion characteristics, operational strategies, heat transfer, hydrodynamics of solid circulation, pollutant formation and control, ash characteristics at high oxygen concentration (up to 55%) 4

5 Oxy-fuel CFB test facilities at IET-CAS Bench-scale Bench-scale Pilot Plant Bench-scale BFBC 100mm CFBC 100mm 30-50kW O 2 : 21-50% CFBC 140mm 0.1MW O 2 : 35-55% CFBC 420mm 1MW O 2 : 21-50% Scale-up 5

6 1 MWth pilot scale oxy-cfbc facility Exterior view of 1 MWth pilot plant Oxy-CFBC facility Construction period: Commissioning: Starting experiments: 2015 Technical data: Total Height: 21 m Furnace Net Height: 15 m Furnace diameter: 420mm Temperature: up to 950 o C Total O 2 concentration: 21%-50% Combustion atmosphere: Air; O 2 /N 2 ;O 2 /RFG External Heat Exchanger (EHE) and bayonet exchanger along the furnace Oxygen/flue gas staging: primary, secondary 6

7 1 MWth pilot scale oxy-cfbc facility- Combustion System CFB combustion system flue gas cooling and cleaning system dry flue gas recycle system gas mixing and supplying system measurement and control system Schematic diagram of 1 MWth pilot plant Oxy-CFBC facility 7

8 1 MWth pilot scale oxy-cfbc facility- Combustion System Technical data: Refractory furnace and cyclone Furnace net height: 15 m Furnace diameter: 280mm(bottom),420mm (top) Temperature: up to 950 o C Water Cooling Bayonet (Vertical: one, 8m; declining: 4 groups, reach the axis) Dual-exit ash distributor Loop seal External Heat Exchanger (EHE) Schematic diagram of 1 MWth pilot plant Oxy-CFBC facility Oxygen/flue gas staging: primary, secondary(four layers) 8

9 Second gas tubes Dual-exit ash distributor Water-Cooled tubes Riser Oil burner for start-up External heat exchanger 9

10 1 MWth pilot scale oxy-cfbc facility- Combustion System Flue gas cooling and cleaning system Flue gas recycle system Recycled flue gas: after bag filter, condenser, condensate knockout, recycle gas blower, and preheater dry; < 40 ; no desulfurization Preheater for recycled flue gas: 180 Gas mixing and supplying system Three mixing tanks for Primary gas, Secondary gas and other gas O 2 /Air, O 2 /CO 2 or O 2 /RFG with varying oxygen concentration The pressures at gas entries are very important. Schematic diagram of 1 MWth pilot plant Oxy-CFBC facility 10

11 1 MWth pilot scale oxy-cfbc facility- Combustion System O 2,CO 2 concentration measurement Flue gas cooling and cleaning system Flue gas recycle system Recycled flue gas: after bag filter, condenser, condensate knockout, recycle gas blower, and preheater dry; < 40 ; no desulfurization Preheater for recycled flue gas: 180 Schematic diagram of 1 MWth pilot plant Oxy-CFBC facility Gas mixing and supplying system Three mixing tanks for Primary gas, Secondary gas and other gas O 2 /Air, O 2 /CO 2 or O 2 /RFG with varying oxygen concentration The pressures at gas entries are very important. 11

12 1 MWth pilot scale oxy-cfbc facility- Combustion System Gas on-line analysis: Flue Gas: FTIR analyzer GASMET DX4000 CO 2, CO, SO 2, NO, NO 2, NH 3, HCN and N 2 O The Primary and Secondary Gas: SIEMENS O 2 : OXYMAT 61 CO 2 : ULTRAMAT23 Fly Ash sampling: Before the bag filter Automatic Control and Data Acquisition: PLC 12

13 Recirculation fan Gas mixing tanks Bag filter Gas flow meter Oxygen and CO 2 on-line analysis Liquid oxygen tank 13

14 1 MWth pilot scale oxy-cfbc facility- Combustion System 14

15 Experiment results in 1MW th pilot-scale oxy-fuel CFBC research facility Start-up stage Oxy-transition behavior 1000 Coal feeding 1000 Air Oxy-transition process Oxy Temprature/ C :00 13:00 16:00 19:00 22:00 01:00 T1 (1.55m) T2 (4.0m) T3 (8.0m) T4 (12.0m) 04:00 07:00 10:00 Temperature/ C :00 18:00 22:00 T1 (1.55m) T2 (4.0m) T3 (8.0m) T4 (12.0m) Coal feed rate 02: :00 Coal feed rate/(kg/h) Fuel analysis for Datong coal LHV/MJ kg -1 ultimate analysis/ wt.% proximate analysis/ wt.% Q net,ar FC ar M ar A ar V ar C ar H ar O ar S ar N ar

16 Experiment results in 1MW th pilot-scale oxy-fuel CFBC research facility Experimental conditions Parameter unit Datong coal Air 30%O 2 /RFG 40% O 2 /RFG 50% O 2 /RFG average bed temperature average cyclone temperature average loop seal temperature average external heat exchanger temperature fuel feeding rate kg/h thermal power MW O 2 in primary gas % vol O 2 in secondary gas % vol overall O 2 concentration % vol primary gas flow m 3 /h secondary gas flow m 3 /h

17 Experiment results in 1MW th pilot-scale oxy-fuel CFBC research facility Temperature profile Temperature/ 0 C T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 Temperature/ 0 C T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T :30 08:36 08:42 08:48 08:54 09:00 Time 09:06 09:12 09:18 09:24 09: :00 03:20 03:40 04:00 04:20 04:40 05:00 Time 05:20 05:40 06:00 06:20 06:40 07:00 Air combustion mode O 2 /RFG combustion mode (O 2 : 50%) 17

18 Experiment results in 1MW th pilot-scale oxy-fuel CFBC research facility Oxy-fuel combustion mode CO 2 concentration in flue gas / % :00 03:30 04:00 04:30 Time 05:00 05:30 06:30 06:00 Height, m air combustion oxy-fuel combustion O 2 concentration in flue gas /% SG temperature, 0 C 03:00 03:20 03:40 04:00 04:20 04:40 05:00 Time 05:20 05:40 06:00 06:20 06:40 07:00 18

19 Experiment results in 1MW th pilot-scale oxy-fuel CFBC research facility Emission 19

20 Conclusion and Future Work Oxy-fuel combustion experiments employing high oxygen concentrations with dry flue gas recirculation were successfully carried out in a 1MW th pilot-scale oxy-fuel CFBC unit at the IET/CAS. This test facility can be operated at air and total oxygen concentrations in the range of 21 50% with different oxygen level in primary and secondary gas. The results show that the operation of oxy-fuel CFBC at high overall O 2 concentration was stable and reliable, and is able to produce flue gas highly concentrated in CO 2. The transition from air combustion to oxy-fuel combustion occurs easily and smoothly. Under 50% O 2 /RFG combustion mode, with external heat exchanger and water cooling tubes to cool the return solids, the recirculation flue gas ratio is much lower compared to pulverized coal oxy-fuel units. 20

21 Conclusion and Future Work Under 50% O 2 /RFG combustion mode, gaseous pollutant emissions for CO and NO are lower than those in air combustion. SO 2 concentration significantly increases with levels up to three times higher compared to air combustion mode, which may produce considerably higher corrosion concerns. Future work Adding CPU unit to 1MWth pilot-scale oxy-fuel CFBC in 2015 Research of the effect of operation parameters under O 2 /RFG with high oxygen concentration (~50%) on combustion characteristic and emission Oxygen concentration level Oxygen staging Combustion temperature Ca/S Fuel Biomass Oxy-fuel CFB combustion 21

22 Corresponding author: address: (S.Y.Li) 22