Impact of gasification conditions on the tar yield of stratified downdraft gasifiers

The research on thermochemical gasification in stratified downdraft reactors targets minimum tar production, low formation of residual char and the stabilization of the oxidation zone. Although the stratified downdraft reactor has many advantages due to its simple design the control of the process and its quality is still a challenge. The aim of the experimental study is to identify the impact of gasification parameters on the tar yield. Correlations between parameters, parameter interactions und correlating process output is determined using statistical methods. Moreover an overview on the state of the art in tar sampling and analysis is given. Several methods for tar sampling are examined and compared among each other: SPA analysis (solid phase adsorption) with different methods, tar sampling and analysis according to DIN CEN/TS 15439 and wet-chemical analysis based on dry condensation and subsequent SPA.