Residual gasification char applied to tar reforming in a pilot-scale gasifier: Performance and evolution of char properties for perspective cascade uses

The solid residue of gasification, or gasification char, is in many cases considered as a waste material inevitably generated during the operation of gasifiers. However, it is a good candidate to substitute synthetic catalysts for tar reforming and it is a carbon-rich material with a good potential for carbon negative applications as biochar. In this work, a wood-derived gasification char was tested for the upgrading of producer gas generated from pilotscale gasification of wheat straw. The effect of a char bed in combination with partial oxidation was assessed under different conditions. The presence of the char bed markedly reduced the total tar concentration, but the bed material suffered deactivation. Partial oxidation prolonged the activity of the char bed by promoting reforming reactions at the surface of char particles and further reduced the tar content below 1 g/Nm(3). Postexperimental characterization of the spent chars revealed a decreased surface area, a more ordered carbon phase and an increased resistance to thermal degradation. The results show that under optimized conditions, gasification char is a promising substrate for tar reforming and the upgrading of producer gas to syngas. Moreover, the changes in the char suggested possible cascade uses of the spent material for carbon sequestration.