アンモニア加圧浸出法による含Niラテライト鉱石からのNi回収に関する研究

Abstract

Some experiments on the recovery of nickel from laterite ore by the ammonia pressure leaching have been carried out in the current investigation. Hydrogen was used as the reducing gas, and ammonia solution containing ammonium sulphate was used as the leaching solution for the recovery of nickel from the reduced ores. The experimental results obtained are summarized as follows;(1) It is required for the efficient extraction of nickel that laterite ores are reduced with H2 gas at the rate beyond the critical flow rate during the reducing roasting, because the amounts of nickel oxides contained in laterite ores are very small.(2) The leaching rate of nickel by the ammonia pressure leaching is about sixteen times greater than that by of the atmospheric ammonia leaching.(3) The ammonia solution containing ammonium sulphate is more effective than that containing ammonium carbonate to obtain the leached solution without ferric ions.(4) The extraction of nickel exceeds 90 percent when the experiment on the recovery of nickel from laterite ore was carried out under the following reduction and extraction conditions: reduction temnerature 900°C, the flow rate of H2 gas 200cc/min, reduction time 90 min, leaching temperature100°C, oxygen pressure 2kg/cm2, stirring rate 500rpm and the concentration of ammonia and ammonium sulphate 3mol/l and 1mol/l, respectively.(5) More satisfactory pretreatment of laterite ore for the pressure leaching is attained by the reduction with H2 gas than by that with CO gas, which was descrided in our previous paper, because the extraction of nickel by the ammonia pressure leaching is not affected by the metallic iron formed during the reducing roasting.