| 摘要 |
1. A method for producing of sodium monochromate by oxidizing roasting with a charge being mixed, said charge comprising chromite, soda and dried residue after the cake leaching and further aqueous leaching of cake and the pulp filtration, characterized in that after the leaching the residue comprises water-soluble salts of sodium monochromate and soda in total amount not more than 8% by weight and 7-12% by weight total chromium on conversion to Cr2O3. 2. The method of claim 1, characterized in that said oxidizing roasting is carried out in an air flow providing a direct contact of technological gases with fuel burning products maintaining oxygen content at the outlet of the roasting zone at 11-13% by weight of total volume. 3. The method of claim 1, characterized in that the temperature in the roasting zone is being raised at a rate of 32-33 degrees/min to the maximum value not more than 1300 degree C in the roasting zone. 4. The method of claim 1, characterized in that the leaching is carried out by water or sodium monochromate and soda solution having a pH not less than 10 at a temperature not more than 80 degree C with a solid residue content in the pulp not more than 700 g/l. 5. The method of claim 1, characterized in that after the aqueous leaching of cake the dried residue is used as 0.1-1.0 mm size fraction. 6. The method of claim 1, characterized in that if admixtures of silicon and aluminum compounds are to be removed, sulfuric acid with a pH between 9.0 to 11.5 is then added to a sodium monochromate solution after the pulp filtration and maintain the mixture during 0.5 to 2 hours at a temperature of 70 to 80 degree C and the mixture is neutralized to a pH 8.0-8.9 after which the precipitated admixture are filtered. 7. The method of claim 6, characterized in that the mass ratio Al2O3:SiO2 in the sodium monochromate solution is maintained in the range of at least 1.3:1 before neutralization by sulfuric acid by introducing, if necessary, water soluble aluminum salts. |
