Fluidized bed gasification of high tonnage sorghum, cotton gin trash and beef cattle manure: Evaluation of synthesis gas production

Fluidized bed gasification using high-tonnage sorghum, cotton gin trash and beef cattle manure was performed in a pilot scale bubbling fluidized bed reactor equipped with the necessary feedback control system. Characterization of biomass showed that the high-tonnage sorghum had the highest energy and carbon content of 19.58 MJ kg^-1 and 42.29%_wt, respectively among the three feed stocks. At 730 °C reaction temperature and equivalence ratio of 0.35, comparable yields of methane, nitrogen and carbon dioxide (within ± 1.4%_vol) were observed in all three feed stocks. The gasification system produced synthesis gas with an average heating value of 4.19 ± 0.09 MJ Nm^-3 and an average yield of 1.98 ± 0.1 Nm³ kg^-1 of biomass. Carbon conversion and gasification efficiencies indicated that most of the carbon was converted to gaseous products (85%_average) while 48%_average of the energy from the biomass was converted into combustible gas. The production of hydrogen was significantly affected by the biomass used during gasification. The synthesis gas heating value and yield were relatively constant at reaction temperatures from 730 °C to 800 °C. Utilizing high-tonnage sorghum, the optimum hydrogen production during gasification was achieved at a reaction temperature of 780 °C and an equivalence ratio of 0.40.