Chapter 12 - Biomass gasification: Thermochemical route to energetic bio-chemicals

Abstract

The chapter provides insight into various processes for converting biomass to bio-derived fuels. The thermochemical conversion processes like pyrolysis, hydrothermal cracking, gasification, and similar processes using catalytic or non-catalytic methods developed in various research organizations are summarized. The technology packages developed are at various stages of scale-up and implementation. Based on the different approaches, the overall efficiency of conversion of biomass to fuels vary. Research at the Indian Institute of Science, Bangalore, on the thermochemical conversion of biomass provides an opportunity to synthesize energetic chemicals of desired carbon to hydrogen ratio and functional structure using CO and H2 as the principal building blocks. A novel fixed-bed reactor can accept a range of biomass with oxy-steam as reactants and efficiently convert the biomass to bio-syngas, a hydrogen-rich mixture containing H2/CO/CH4/CO2/N2 components along with other trace compounds. Gaseous mixture with hydrogen volume fraction between 20% and 50% and H2/CO ratio from 1.0 to over 4.0 can be realized under appropriate conditions using Air/Oxygen/Steam as the gasifying media. Further, using downstream separation techniques results in yields of ~100g of H2/kg of biomass and ~500g of H2-CO mixture (2:1 ratio—methanol synthesis) at over 75% efficiency. Analysis for the downstream process from syngas to the product gas suggests that the generated gas is of quality as required for end-product needs as per the existing processes. Beyond H2, the ratio-controlled syngas can be used for the synthesis of methanol, Ethanol, high hydrocarbons, etc., using established synthesis techniques. The multi-fuel-based technology can be feed agnostic and can handle a range of agro-residues.