REUSE OF LANDFILLED FBC RESIDUES

Two aspects of the possible reactivation of fluidized bed combustion ( FBC) residues are considered. One is the behaviour of aluminosulfates such as ettringite, which may form when excess water is used in hydrat ion methods designed to reactivate the lime in the FBC residues. The s econd is the behaviour of compounds such as calcium aluminates, silica tes or ferrites ('other calcium compounds' or OCC) that are produced b y reactions in the fluidized bed. In both cases, the possibility of re covering the CaO contained in these materials for retention of SO2 whe n they are reintroduced into a combustor is assessed. It was found tha t ettringite is an excellent sulfur sorbent under FBC conditions, with reactivity superior to normal limestones. The CaO moiety in the OCC i s not easily reactivated by hydration. Unhydrated, they do react in a sulfating atmosphere like that of the combustor, but their performance as sorbents is much poorer than limestone and varies with the nature of the compound. (C) 1997 Elsevier Science Ltd.