Types of Biomass Gasifiers

Two major types of gasifiers currently in development are direct-fired gasifiers, using air, and the indirect-fired method, where heated sand surrounds biomass and gasifies it. These design schemes are described in Chapter 3. 

The indirect-fired process gasifies biomass at low pressure, using indirect gasification to produce gases with medium 

In the Battelle/Columbus gasification system biomass particles are surrounded with extremely hot sand, which converts it into gaseous form. The solid biomass is surrounded by sand heated from 1800 to 1900°F, which converts the biomass into gas and residual char in a fluidized-bed reactor at 1500 to 1600°F. Sand is used to carry the biomass and the char and to distribute the heat. Using sand as a heat carrier keeps out the air. This results in a better quality fuel gas. A second reactor combusts the char to heat the sand. Remaining traces of condensable matter formed during gasification are removed in a chamber where a catalyst cracks and converts them into fuel gas. The clean biogas is then pressurized before it reaches the gas turbine. 

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