TWO-STEP DECOMPOSITION OF AN APATITE CONCENTRATE BY NITRIC ACID.

One of the urgent problems of nitric acid technology in the manufacture of complex fertilizers is intensification of the decomposition of the apatite concentrate by nitric acid and increasing the degree of utilization of the starting reagents. According to the results of theoretical studies and practical data, the following parameters should be maintained to ensure 99-99. 5% decomposition of apatite under industrial conditions: a temperature of 45-60 degree C, a process time of 1. 5 h, and a nitric acid norm that is 110-115% of the stoichiometric value. Of the indicated parameters, only the temperature range can be regarded as acceptable, since it makes it possible to carry out the process under adiabatic conditions. In view of this, the authors have developed a method for the two-step decomposition of an apatite concentrate by nitric acid which was substantiated and experimentally confirmed. The method makes it possible to substantially reduce the process time and decrease the nitric acid consumption. refs.