First Results of an Oxyfuel Combustion Fluidized Bed

Transcription

1 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

2 CIRCE description. Team: Laboratories: Biomass/coal combustion Oxyfuel combustion CFB looping

3 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

4 INDEX CIRCE description Background and objectives Test facility description Test results Conclusions and future work

5 Background and objectives 2006 Spanish Science Ministry R+D Call (Energy) ( ) 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 ( ) Perform tests in fluidized bed oxyfuel combustion Process simulation Other projects under evaluation

6 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

7 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

8 Test facility description 90 kwt O 2 /CO 2 bubbling fluidized bed

9 Test facility description Center of research on energy

10 Test facility description Test plan Coal types Anthracite, Spanish lignite, Bed temperature 750ºC-825ºC-900ºC CO 2 /O 2 concentration at inlet % / 20-60% Recirculation ratio 0-80 % Ca/S molar ratio Coal particle diameter 700/1200 μm Limestone particle diameter 500/1000 μm Oxygen in flue gases 3-6 % Fluidization velocity m/s

11 Test Results First tests Air: Low volatile anthracite (57% C; 35% ash; 6% volatile; 2 % moisture; LHV 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: ºC; Bed height: m; Fluidization velocity: m/s Poor fluidization and low combustion efficiency: Coal type Increase air mass flow (fluidization velocity). Change coal type

12 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: CO2 O BED TEMPERATURES

13 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 ºC bed temperatures <- BED TEMPERATURE, ºC CO2 in flue gas, % -> OXYGEN in flue gas, % -> minutes

14 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.

15 Test Results Sintering

16 Test Results Sintering

17 Test Results SEM O Na Mg Al Si S K Ca Ti Fe 2 mm SEM3 2 O (13.8%) Si (21.2%) 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%)

18 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