Gasification Research at OSU Ajay Kumar, Assistant Professor Biobased Products and Energy Center (BioPEC), Biosystems and Agricultural Engineering, Oklahoma State University OK EPSCoR Annual State Conference
Energy conversion pathways Source Conversion techniques Products or intermediate products Biochemical conversion Ethanol Biomass (38-50% cellulose, 25-32% hemicellulose, 15-25% lignin) lignin & hemicellulose Synthesis gas (syngas) agricultural residues, perennial crops, forestry residue, animal waste, municipal wastes, etc. Thermochemical conversion Bio-oil 2
Thermochemical Conversions Biomass Pyrolysis Char Bio-oil Air Steam Gasification Ash Tar Gas Combustion Heat Byproduct
Gasification process Sorghum Switchgrass Biomass Air Steam Gas Tar Char Ash Required: high temperature & oxidizing agent biomass + air + H 2 O C (char)+ CH 4 + CO + H 2 + + CO 2 + N 2 + H 2 O (unreacted steam) + ash + tar 4
Gasification operations Involved Preprocessing of biomass Gasification Gas clean-up & reforming Gas utilization Size reduction, Drying, Preparation of gasifying agents Heating, Chemical reactions, catalysis Removal of impurities, e.g.. Char, tar, & ammonia, Reforming of the syngas, catalysis CHP, Chemicals, Liquid fuels such as ethanol, green diesel and gasoline Upstream processing Gasification Downstream processing
Gasification process - factors Gasification Heating, Chemical reactions, catalysis Biomass properties Particle size Bulk density Proximate analysis Elemental analysis Energy content Cellulose, hemicelluloses & Lignin contents Product properties Syngas composition Syngas energy Carbon conversion efficiency Energy conversion efficiency Overall energy efficiency Amount of tar Amount of char Operating conditions Biomass flow rate Temperature profile Flow rates of oxidizing agents (equivalence ratio (ER), steam to biomass ratio, (SBR)) Amount and type of catalyst
Gasification: technical challenges Experimental challenge Understand and predict the effects of gasification conditions and biomass properties Reduce level of tar and impurities in the producer gas Optimize gasification operating conditions & gasifier design Improve cold gas cleaning technique Improve hot gas cleaning technique Increase percentage compositions of CO and H 2 Increase net process energy efficiency Obtain data for developing gasification reaction kinetics for a wide variety of feedstock Computational challenge Develop gasification reaction kinetics Incorporate reaction kinetics to develop gasification model to reliably predict gas composition, flowrate and contaminants
Ongoing Projects Study of fluidized-bed biomass gasification at near pilot-scale level. Study of downdraft biomass gasification at near pilot-scale level. Design and performance evaluation of a new lab-scale fluidizedbed gasifier. Evaluation of commercially-available catalysts for cracking tar and improving gas composition with toluene as a model tar compound. Design and development of catalytic reactor for cracking real tar and improving gas composition. Characterization of biomass for thermochemical conversion, and Development of reaction kinetics and mathematical model for predicting products of gasification
Study of FBG system at near pilot-scale Gas scrubbing system Fluidized-bed Gasifier (FBG) Biomass feedrate 15-30 kg/h
Design and performance evaluation of new lab-scale FBG to catalytic rector Cyclone Biomass sand Air and/or steam Ash + Char Objectives Design a new lab-scale FBG with many instrumentation and control Supply producer gas with tar to tar cracking catalytic reactor Utilize this FBG reactor serve as a platform for studying catalytic degradation of tar and effects of numerous variables
New lab-scale fluidized-bed gasifier (FBG) Biomass feedrate 3-5 kg/h
Evaluation of catalysts with toluene as a model tar compound Toluene is used as a model tar compound Tests are being conducted on selected steam reforming catalysts which are commercially available for cracking tar
Study of catalysts in a secondary reactor air & steam Cyclone Catalytic cracker Furnace Biomass catalyst Air and/or steam Ash + Char Objectives Study effects of operating condition of catalytic cracker (air and steam flowrate, temperature, residence time) and selected steam reforming catalysts for cracking tar and improving gas composition from gasifier. Field-test commercially-available catalysts
New catalytic Reactor for hot gas cleaning To Flare Air H2O (HPLC) Syngas w/ tar TI TI Gas sampling Tar sampling TI Guard Bed TI D TI Heated gas line Catalytic Bed DPI Stop valve Mass flow controller TI To Flare Gas sampling TI Tar sampling Objectives Study effects of operating condition of catalytic cracker (air and steam flowrate, temperature, residence time) and various steam reforming catalysts on tar level and gas composition Catalysts: commercial Ni-based steam reforming catalysts
Biomass characterization for thermochemical conversion Coupled TGA-FTIR set-up Studying reaction kinetics of gasification Identifying compounds at various reaction conditions Mass Spec with precision sampling system Online measurement of gas composition
Residual weight (%) (TGA) DTG (%/ C) Reaction kinetics of gasification Nitrogen or air Biomass TGA Ash and partial char Evolved gas GC GC-MS FTIR 120 100 80 60 40 20 0 Stage I Dehydration zone TGA (%) Stage II Active pyrolysis DTG (%/ C) 0 100 200 300 400 500 600 700 800 900 Temperature ( C) Stage III Passive pyrolysis volatiles ash + fixed carbon Kumar et al., 2008. Biomass and Bioenergy. 0.1 0-0.1-0.2-0.3-0.4-0.5-0.6-0.7-0.8 Objectives Investigate the effects of oxidizing atmosphere, temperature and heating rate on gas and tar composition Derive volatization kinetics of various feedstocks Develop gasification model to predict producer gas composition
Cyclone gasifier Equivalence ratio 0.12 0.15 0.15 0.15 0.22 Dry gas composition, % volume CO 17.5 15.7 19.7 19.9 20.2 H 2 4.2 5.0 5.5 5.8 6.5 CH 4 3.2 3.7 4.1 3.3 3.2 CO 2 16.2 17.8 18.5 14.8 13.4 N 2 57.9 55.3 49.5 53.7 55.0 C 2 H 2 Not detected 0.9 0.9 0.8 0.7 C 2 H 4 1.0 1.4 1.72 1.3 0.9 C 2 H 6 Lower heating value of dry gas (kcal. m -3 ) Dry gas yield ( m 3. kg -1 dry biomass) Char generation, % of fuel input Not detected 0.2 0.2 0.4 0.2 1052 1273 1471 1395 1294 0.9 1.1 1.2 1.1 1.6 20 19 16 16 NA
Study on downdraft gasifier Biomass To gas cleanup system Burner Biomass hopper Air lock Tar & particulate measurement system Propane Air Ash
Temperature, C Temperature profile for switchgrass gasification 1200 1000 Tar Cracking, CG1 800 600 Below Grate 400 200 Flame 0 0 50 100 150 200 Time from start, minutes
% Volume Gas composition Switchgrass gasification 60 50 CO H2 40 30 20 10 0 0 50 100 150 200 250 300 350 CH4 CO2 N2 C2H2 C2H4 C2H6 Time from start, min
Cold gas efficiency, % Hot gas efficiency, % Energy Efficiency 90 80 70 60 50 40 30 20 10 0 450 500 550 600 650 700 Specific air input rate. kg/h-sq. m Wood Pellets Switchgrass Sweet Sorghum Forage Sorghum W2 Wood Shavings Corn fermentation waste 80 70 60 50 40 30 20 10 0 450 500 550 600 650 700 Specific air input rate. kg/h-sq. m Wood Pellets Switchgrass Sweet Sorghum Forage Sorghum W2 Wood Shavings Corn fermentation waste
Air and air-steam gasification of chopped forage sorghum 20.0 18.0 16.0 14.0 12.0 10.0 8.0 AIR AIR-STEAM 6.0 4.0 2.0 0.0 CO H2 CH4 CO2
Personnel and Financial Support PIs: Ajay Kumar Krushna Patil Danielle Bellmer Raymond Huhnke Graduate Students/Research engineer: Ashokkumar Sharma Design and study of lab-scale fluidized-bed gasification Prakash Bhoi Study of downdraft gasification Vamsee Pasangulapati Thermochemical characterization of biomass Sabre Arrowood Design and study of new catalytic tar cracker Akshata Modinoor Study on effects of catalytic reactor condition on tar cracking Luz Martin - Evaluation of the selected catalysts for tar cracking Financial Support provided by: Oklahoma State Regents for Higher Education NSF OK-EPSCoR Oklahoma Bioenergy Center USDA Special Grant Director of the Oklahoma Agricultural Experiment Station
Thank you, Questions?