Chapter 9 - Thermal Conversion: Gasification

Abstract

This chapter discusses the subject of thermal conversion, particularly biomass gasification. Biomass gasification processes are generally designed to produce low- to medium-energy fuel gases, synthesis gases for the manufacture of chemicals, or hydrogen. More than one million small-scale, air blown gasifiers for wood and biomass-derived charcoal feedstocks were built during World War II to manufacture low-energy gas to power vehicles and to generate steam and electric power. Units were available in many designs. Thousands were mounted on vehicles and many were retrofitted to gas-fired furnaces. The pyrolytic gasification of biomass has been interpreted to involve the decomposition of carbohydrates by depolymerization and dehydration followed by steam-carbon and steam-carbon fragment reactions. Basically, there are three types of biomass gasification processes—pyrolysis, partial oxidation, and reforming. Under idealized conditions, the primary products of biomass gasification by pyrolysis, partial oxidation, or reforming are essentially the same—carbon oxides and hydrogen; methane and light hydrocarbon gases are also formed under certain conditions.