Chinese Academy of Sciences

Zuohu Li

Yi Zhang

Tao Qi

Huiquan Li

Hongzhang Chen

Shili Zheng

Hongbin Xu

Zhikuan Wang

This invention relates to a method for producing chromates, especially for producing alkali metal chromates. The method comprises following steps: the obtaining of a mixture of alkali metal hydroxide, alkali metal chromate, and ferrous residue after the reaction of chromite ore with an oxidant in the reactor in the presence of molten salt or in aqueous solution of alkali metal hydroxide, the obtaining of a leaching slurry by leaching the reaction products with aqueous solution of alkali metal hydroxide, the separating of the primary chromate product from the leaching slurry, the obtaining of pure chromate crystal by purifying the primary chromate product. Both the primary chromate product and the pure chromate crystal can be used as the raw materials to manufacture other chromium compounds. Compared with the currently-used roasting method, the method has the advantages of decreasing the reaction temperature by about 700&#xb0; C., of improving the chromium recovery rate up to nearly 100%, of minimizing the amount of the ferrous residue by not adding calcium-containing auxiliaries, and of completely eliminating the disposal problem of the chromium-containing residue and the environmental pollution due to the addition of calcium-containing auxiliaries, by using ferrous residue as the raw materials for other industries after extraction of magnesium.

Method for production of alkali metal chromates

The gas dual-dynamic solid state fermentation technique consists of placing the solid materials to be fermented in an air environment with pulsating pressure and cyclic flow to carry out fermentation, the fermentation apparatus comprises a horizontal cylindrical tank with a quick door mechanism, in the tank are axially disposed rectangular spacer barrels of square cross-section constructed by four baffles, in the space between baffles and the tank wall are provided cooler tubes in parallel with the baffles, in the middle of the spacer barrels are provided vertically many sets of cooler tubes, on the lower baffles in the tank is provided axially an fixed track, on which are movable tray racks that can roll on the track, the tray racks having thereon a plurality of layers of trays, at the rear of the tank is provided a centrifugal blowers for forcing gas cycling in the tank. The inventive technique and apparatus allows microbial pure cultivation, is easy for scaling up and high in fermentation virulence titre and produce no pollution. It is useful for fermentation production of biological pesticides, enzyme preparations, agricultural antibiotics and unicell albumen.

Gas dual-dynamic solid state fermentation technique and apparatus

Growing community of inventors

Beijing, China

Zuohu Li