Performance of CaO and MgO for the hot gas clean up in gasification of a chlorine-containing (RDF) feedstock

Calcined limestone (CaO) and calcined dolomite (CaO · MgO) were tested at bench scale to study their usefulness in cleaning hot raw gas from a fluidized bed gasifier of a synthetic or simulated refuse-derived fuel (RDF) with a high (3 wt%) content in chlorine. In the gas cleaning reactor two main reactions occurred simultaneously: the elimination of HCl and the elimination of tar by steam reforming. The elimination of HCl formed CaCl2 and MgCl2 with melting points below the high (above 800 °C) temperatures required for the simultaneous tar elimination reaction. So, the CaO-based particles progressively melted and the catalytic gas cleaning reactor became a compact, agglomerated or glued, cake. Therefore, the life and usefulness of the CaO-based solids used was very low. Nevertheless, and to further avoid these problems, some positive guidelines for future research are proposed here.