METHOD OF OBTAINING PHOSPHORIC ACID

摘要

The invention in essence is a method of obtaining wet-process phosphoric acid from a variety of raw phosphate materials in a single-step process. The claimed process involves the break-down of raw phosphate material with the aid of sulphuric acid and re-used phosphoric acid; crystallization of the calcium sulphate precipitate in the presence of seed particles; and subsequent separation of the output filtration sludge and washing of the calcium sulphate precipitate. The seed particles are obtained by the crushing of a portion of the calcium sulphate precipitate and are introduced in quantities of 0.5-120 seed particles of 1-1000 mu m in size for every 100 particles of output filtration sludge of the same size range, the mean particle size being smaller than the mean particle size in the filtration sludge by a factor of at least 1.2. The crushing process is carried out either directly on the sludge or after the decomposition thereof. With the claimed process it is possible to increase the conversion of P2O5 to finished product, to increase the specific filter yield and to reduce the moisture content of the precipitate.