| 摘要 |
<p>In the disintegration of a chromite or chromium-containing residue, wherein the chromium-containing material is disintegrated with an alkaline compound in the presence of oxygen and a diluent at a temperature above about 800 DEG C. and thereafter leached, the improvement which comprises pre-roasting the chromium-containing material prior to addition of the alkaline compound. Pre-roasting can be effected at 400 DEG to 1200 DEG C. with addition of certain amounts of silica dioxide and/or aluminum oxide and such additives, depending on the chromium containing material, if still required, are added-prior to disintegration and leaching-in such a quantity to establish a ratio of SiO2: AL2O3 of about 2:1 and further a ratio, calculated on the basis of NaOH as the alkaline compound, of SiO2: Na2O of about 1:0.5 plus a Cr2O3: Na2O ratio of about 1:2 to 1:4. Residues from previous leaching cycles can be present during disintegration as solid diluents but their contents of SiO2 and/or Al2O3 are not taken into account in calculating the SiO2:AL2O3 ratios. The process gives excellent results even with starting materials relatively high in SiO2 which are difficult to disintegrate to materials of desirable properties by other methods.</p> |
