Calcining of phosphate ores - where preheated and calcined ore is fluidised in air to complete combustion and oxidn. of constituents in ore prior to cooling

摘要

The ore is preheated, and is then rapidly calcined as a suspension in a static calcining chamber. The calcined ore is then kept at a high temp. for 5-10 minutes, pref. in a fluidised state, before being cooled. The calcined ore is pref. fluidised by air, the rate of flow of the air being adjusted so the temp. of the ore does not drop by more than 100 deg.C in the fluidised bed prior to cooling. The pref. plant includes two preheating cyclones receiving hot gases leaving a static calcining cyclone. After leaving the calcining cyclone, the ore flows into a fluidised bed with an overflow leading to three cooling cyclones. Used for efficient calcining, where organic matter is removed, and the air in the fluidised bed converts sulphides into sulphates.