Gasification of waste biomass for hydrogen production: Effects of pyrolysis parameters

Understanding the behaviour of pyrolysis is crucial in gasification of high volatile content lignocellulosic material. In this study, parameters affecting the properties of volatiles and char that are feedstock for the gasification step were studied to determine and optimize operating conditions in pyrolysis for high quality syngas/hydrogen production. A uniform temperature profile was obtained at particle sizes up to 0.5 cm3. Pyrolysis temperatures in the range 600–900 °C significantly influence the char properties, i.e. increasing surface area and total pore size up to 2.5–3 times when increasing temperature, which in turn enhances the gas-solid reactions occurring in the gasification process. Increasing pyrolysis temperatures, i.e. above 700 °C fully decomposed unstable compounds, i.e. levoglucosan and their derivatives, but promoted the formation of phenolic compounds. Around 41% reduction in surface area and total pore volume of the char was observed when increasing particle size from 0.5 to 2 cm3. At pyrolysis temperatures above 800 °C and particle size of 0.5–1 cm3 with a controlled amount of steam, i.e. 5.7 steam to carbon in biomass (S/C) molar ratio, the H2 content in the gas phase increased to 67 mol% from 49 mol% and the aromatic compounds in the gas stream decreased up to 50.6%.