HIGH-TEMPERATURE BIOMASS GASIFICATION IN AN ENTRAINED FLOW REACTOR - DESIGN AND ENGINEERING OF A TEST FACILITY

For several applications like catalytical conversion or a piston-engine a tar free gas should be available. The state of the art technology for the gasification of biomass is the fluidised bed (FB) gasification. Although this technology is realized in small and medium-scale plants, there is one main disadvantage in comparison to an entrained flow (EF) reactor: Due to the operation temperature < 950 degrees C the product gas contains a high amount of tars and an aftertreatment to reduce the concentration of tars is necessary. The aim of this work is to design a high-temperature gasifier to avoid tar in the product gas and to use biomasses which are not used energetically until now. Also they should not compete with the agricultural cultivation of food. Therefor grass-cut, agricultural residuals and straw are of interest. The process is divided into a biomass pretreatment (hydrothermal carbonization or torrefaction) and the EF gasification. The EF gasification is state of the art in industrial coal gasifiers and even can be easier in setup and handling than a FB gasifier. A lab-scale EF gasifier (100 kW, pneumatical fuel feeding 10-25 kg/h) was designed and constructed to be operated either with ambient air at 1000-1200 degrees C or with O-2, CO2 and/or steam up to 1500 degrees C and 6 bar a. In order to facilitate a future up-scale and to learn about the conditions and problems of a real process the gasifier is engineered as close as possible to an industrial process. For this reason the gasifier operates autothermal and has a burner system. The reaction tube consists of several layers of refractory. The dimensions of the reaction chamber were defined after kinetic calculations for optimal char conversion.