Biomass and black liquor gasification

Klas Engvall, Truls Liliedahl & Erik Dahlquist


Modern society is profoundly dependent on fossil feed stocks to produce multiple products, such as transportation fuels, fine chemicals, pharmaceuticals, detergents, synthetic fibers, plastics, fertilizers, lubricants, solvents, waxes, etc., as well as heat and power (Demirbas, 2006). The fossil resources are not endless. Their price is increasing continuously due to increasing scarcity, and not regarded as sustainable from an environmental point of view (Kamm, 2006). A versatile resource, especially in terms of producing carbon-based products, to replace fossil feedstocks is biomass (Vlachos, 2010) or other sources originating form biomass, such as black liquor (BL). Conversion of biomass to other products can be performed either by biochemical or thermo­chemical processes. In the case of large-scale production of, for example, carbon-based products, thermo-chemical conversion is considered more efficient compared to biochemical processes (Zhang, 2010). Techniques for thermo-chemical conversion can be divided into pyrolysis, gasifi­cation, combustion and liquefaction. Among these techniques, gasification is a versatile platform for production of multiple products, as illustrated in Figure 6.1.

Gasification has a long history starting with Thomas Shirley who experimented with “carbu­reted hydrogen”, today called methane, in 1659 (Basu, 2010). In the beginning of the 17th century and onwards to the early 19th, gas from gasification of coal was mainly used for lightening of homes and streets and for heating. New inventions in other fields expanded the utilization of the gas in diverse applications, such as fuel for steam engines, feedstock in chemical production


Figure 6.1. Examples of products obtained from gasification processes (modified from Demirbas, 2009).

of chemicals and motor fuels. During this time the major commercial gasification technologies, Winkler’s fluidized bed gasifier in 1926, Lurgis pressurized moving bed gasifier in 1931 and Koppers-Totzek’s entrained flow gasifier were developed before the Second World War. After the Second World War the availability of abundant oil eliminated the need for gasification as a basis for production of chemicals and motor fuels. Today, the driving force for the renewed interest is the concerns about global warming and about the accessibility to fossil resources.