Hydrogen generation through thermochemical gasification of potato waste and modelling

The aim of this study was to determine the suitable gasification reaction conditions of potato waste (biomass), supplied from a chips factory, in order to enhance the hydrogen yield in a gas product. In addition kinetics of water gas shift reaction which is one of the basic reactions in biomass gasification was investigated. The effect of various reaction parameters such as promoter/catalyst type (Ca(OH)2, Ru/C, Ru/C:Ca(OH)2, CaCO3), temperature (400, 450, 500, 550, 600oC), pressure (220, 270, 290 bar), time (20, 30, 60 min), Ca(OH)2 ratio (0, 10, 20,30, 50, 70 (wt/wt promoter/biomass)) and biomass concentration (1.00, 1.75, 2.50, 5.00 (wt/wt biomass/water)) on H2 yield were investigated. Suitable reaction conditions were determined as 600oC, 270 bar, 30 min and 1.75% biomass concentration in the presence of 20% Ca(OH)2 with the H2 yield of 34.88 mol/kg biomass and gasification efficiency of 98.93%. While hydrogen yield was 41.77 mol/kg biomass in the presence of Ru/C, it increased to 44.02 mol/kg biomass by adding Ca(OH)2 into the reaction media at the same reaction conditions. Plackett-Burman design was applied to evaluate the effect of reaction parameters such as temperature (400, 500, 600oC), time (10, 20, 30 min) and CaCO3 ratio (10, 20, 30 %) at a constant biomass concentration of 1.75 %. Optimum condition is defined as 600oC, 30% CaCO3 and 30 min. While the experimental yield of 32.16 mol H2/kg biomass was achieved, theoretical yield of 29.79 mol H2/kg biomass was determined using Minitab 14 package. Kinetics of water gas shift reaction which is directly affects the yield of H2 was investigated at the temperature from 350 to 400oC and 3:1 H2O:CO molar ratio. The activation energies of non-catalytic and catalytic (Ru/C) reactions were determined as 158.42 and 69.45 kJ/mol, respectively.