First Results of an Oxyfuel Combustion Fluidized Bed Luis M Romeo (luismi@unizar.es), Isabel Guedea, Irene Bolea, Ana Gonzalez, Carlos Lupiañez, Javier Pallares, Enrique Teruel, Luis I. Diez 1st OXYFUEL COMBUSTION CONFERENCE, Cottbus, Germany, September 2009
CIRCE description. Team: Laboratories: Biomass/coal combustion Oxyfuel combustion CFB looping
CIRCE description non-profit private organisation, sponsored by Utility Mining Educational Government R&D in energy and thermal and electrical engineering experience in coal & biomass combustion, plant tests & monitoring, laboratory work, simulation, CFD, conventional (PF) and advanced (FBC, IGCC, co-firing) concepts, CO 2 capture
INDEX CIRCE description Background and objectives Test facility description Test results Conclusions and future work
Background and objectives 2006 Spanish Science Ministry R+D Call (Energy) (2006-2008) Analyse the technical feasibility of the OXYCO-FIRING technology Co-firing of coal and biomass. Design, construction and start-up a pilot-scale rig (around 100 kwt) Searching an adequate compatibility among traditional fossil fuels and renewable resources (biomass). Blends of coal and biomass 2009, 2010 Spanish Science Ministry R+D Call (Energy) Technical feasibility of high sulphur/low rank coal oxyfuel combustion CIUDEN (2009-2011) Perform tests in fluidized bed oxyfuel combustion Process simulation Other projects under evaluation
Test facility description 90 kwt O 2 /CO 2 bubbling fluidized bed 2.7 m height, 20 cm i.d. FB water-cooled 2 x 200 litres hoppers for fuel feeding (coal, sorbent, biomass) CO 2 /O 2 mixer and flue gas recirculation Preheating of fluidising gas Gas cleaning: cyclone and fabric filter Recycling ratio: from 0% to 80% O 2 in the mixture: from 20% to 60% CO 2 recirculation Coal + Biomass O 2 Air Separation Unit (ASU) Electric Power Flue gases CO 2, H 2 O,... CO 2 Compression and dehydration CO 2 transport and storage Air
Test facility description Lecho fluido burbujeante Fluidized bed Ciclón Cyclone Heat exchanger Intercambiador de calor Start-up Quemador de burner gas Chimenea Stack Sistema de Fuel feeding alimentación de combustible system Fabric Filter Filtro de mangas Ventiladores Fans Sistema de alimentacion del comburente system CO 2 /O 2 feeding Aero refrigerador Cooling system
Test facility description 90 kwt O 2 /CO 2 bubbling fluidized bed
Test facility description Center of research on energy
Test facility description Test plan Coal types Anthracite, Spanish lignite, Bed temperature 750ºC-825ºC-900ºC CO 2 /O 2 concentration at inlet 80-40 % / 20-60% Recirculation ratio 0-80 % Ca/S molar ratio 1.5-2.1 Coal particle diameter 700/1200 μm Limestone particle diameter 500/1000 μm Oxygen in flue gases 3-6 % Fluidization velocity 0.7-1.0 m/s
Test Results First tests Air: Low volatile anthracite (57% C; 35% ash; 6% volatile; 2 % moisture; LHV 21400 kj/kg). Particle diameter coal and limestone around 500 μm. 14 test: 9 air test y 5 oxyfuel test Typical values of 10% CO 2 in flue gases (up to 18%). High CO (1200 ppm) and O 2 concentrations Bed temperatures: 800-850ºC; Bed height: 0.5-0.6 m; Fluidization velocity: 0.4-0.7 m/s Poor fluidization and low combustion efficiency: Coal type Increase air mass flow (fluidization velocity). Change coal type
Test Results Oxyfuel: Similar problems with low combustion efficiency and fluidization Increasing O 2 concentration at inlet (40%) Reduction of CO concentration in flue gases (800 ppm) Increase of combustion efficiency and CO 2 concentration in flue gases 80,00 70,00 60,00 50,00 40,00 30,00 20,00 10,00 0,00 Change air-oxyfuel FLUE GAS CONCENTRATIONS Change in flue gas analizer channel. 40% O2 at inlet 11:44 CO2 concentrations higher than 75% Change oxyfuel-air 12:04 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 3000 CO2 O2 900 880 860 840 820 800 780 760 740 720 700 680 660 640 620 600 BED TEMPERATURES 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 300
Test Results (last tests) Even combustion behaviour 20% CO 2 and 4-8% O 2 concentration with air 87% CO 2 and 5-10% O 2 concentration with oxyfuel 70-30% CO 2 -O 2 concentration an inlet 760-870ºC bed temperatures 950 900 850 <- BED TEMPERATURE, ºC 100 90 80 800 750 700 650 600 550 500 CO2 in flue gas, % -> OXYGEN in flue gas, % -> 70 60 50 40 30 20 10 450 0 2210 0 2270 5 2330 10 2390 15 245020 251025 257030 minutes
Test Results Main oxyfuel problems: Fluidization problems and control (pressure) of flue gas recirculation SINTERING Only in oxyfuel tests (3/5), maximum temperatures around 870ºC Bed agglomeration. Broken in small pieces Bed sintering. Harder and larger than agglomerate.
Test Results Sintering
Test Results Sintering
Test Results SEM3 1 18 16 14 12 10 8 6 4 2 0 O Na Mg Al Si S K Ca Ti Fe 2 mm SEM3 2 O (13.8%) Si (21.2%) 16 14 12 10 8 6 4 2 0 O Na Mg Al Si S K Ca Ti Fe O (15.5%) Al (7.5%) Si (9.1%) Ca (9.4%) CaSO 4 Layer O (15.2%) Ca (11.0%) Si (9.6%) K (3.0%) Al (4.5%) Fe (2.6%)
Conclusions and future work First tests of fluidized bed oxyfuel combustion Start-up problems solved Sintering and low combustion efficiency (coal and fluidization) Last tests show better fluidization and combustion Future Test different coal types Avoid sintering and increase combustion efficiency Reduce fluidization problems Analyse the influence of: Bed temperature Coal type. Biomass cofiring CO 2 /O 2 ratio and air combustion. Flue gas recirculation