Abstract
AbstractThe dihydrate process for the production of phosphoric acid is increasingly important as the basis for phosphate fertilizer plants. The process involves dissolution of phosphate rock in an aqueous mixture of phosphoric and sulfuric acid and subsequent crystallization of calcium sulfate dihydrate from the product phosphoric acid solution. In this study the mechanisms of dissolution of phosphate rock are studied using reagent grade and plant acids. The effects of various operating parameters such as temperature, particle size and excess sulfuric acid concentration on the rate of dissolution of rock are investigated. The results show that the dissolution of the rock occurs in two stages of different rates. Initially, the dissolution process is fast and is controlled by chemical reaction between rock and acid. In the second stage, when the particles are coated by calcium sulfate dihydrate the dissolution process is slow and controlled by mass transfer of acid through the coating layer.
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