Fluidized-bed thermal treatment of phosphate rock: Effect of operating variables

Abstract

The presence of huge amounts of low- and intermediate-grade phosphate ore and the need for high-grade ore for industry, necessitates the availability of economic and efficient upgrading techniques. The fluidized-bed technique is most suitable for upgrading, by thermal treatment, of ores having high percentages of organic matter, carbonates, and moisture. In this work, studies were carried out on the process of thermal upgrading of phosphate rock in a fluidized-bed furnace of 10-cm diameter. The studies involve the effect of the important operating variables such as process temperature, air-flow rate, calcine quenching temperature, and the attrition of phosphate particles. A run-of-mine intermediate-grade phosphate ore was used. Batch and continuous runs were carried out and the ore was calcined and washed. It was found that the increase in process temperature favourably affects the % upgrading of the ore, but this should be studied in close connection with the economic aspects, especially in the case of ores with low carbonaceous matter contents. The fluidizing air-flow rate, and thus, the hydrodynamic condition of the bed, slightly affects the upgrading process. The use of high air-flow rates increases the extent of attrition of phosphate particles. The quenching temperature of the calcine was found to have no effect on the process product, within the range investigated.