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As one of the important strategic materials, chromium has been widely used in metallurgical, refractory, and chemical industry. Ferrochrome is an important additive in the production of alloy steel. According to the carbon content, it is classified as high-carbon ferrochrome (carbon 4–8%), medium-carbon ferrochrome (0.5–4%), low-carbon ferrochrome (0.15–0.50%), micro-carbon ferrochrome (carbon 0.06%), and ultra-micro-carbon ferrochrome (less than 0.03%). But the most widely used one in metallurgical is the first three. This article mainly summarizes the current development of domestic and international medium-low-carbon ferrochrome and summarizes the preparation methods and the influence factors in the smelting process including reduction temperature, reduction time, the reduction agent, and alkalinity.

Both chromite powder and ferrosilicon have good wave absorbing property in microwave field, the effects of reduction temperature, reduction time, microwave power, raw particle size and material height were investigated. The results from laboratorial experiments have shown that the particle size, microwave power and material layer height have obvious influence on the heating rate of the material. When the particle size is less than 74 μm, the material heating rate increased obviously and the conversion rate of chromium increased. With the particle size is less than 48 μm, chromium conversion rate is highest reaching 72.13%; when the microwave power from 1300 W, the heating rate increased remarkable, the conversion rate of chromium is also increasing and also reduce the heating time and save energy, but the impact on the chromium conversion rate is not obvious; the reduction time and reduction temperature on conversion ratio of chromium effect is very obvious, with the temperature is higher than 1200 °C and the reduction time reduction of chromium is more favorable.

The ferrous removal process after carbothermic reduction of chromite fines with microwave heating combined with leaching was investigated. Under the following conditions: Reaction temperature: 1150°C , Reaction time : 40min, Semi coke ratio: 12% , the iron content of the reduction product : 13.05% . Metallization achieved was 52.7%. Reduced chromite was leached with 8% of H2SO4 and FeCl3 aqueous solution. The results show that: the recovery rate of chromium can reach 88.06%, the mass ratio of chromium to iron is 3.5:1 for leaching 30 minutes with 8% of H2SO4; the recovery rate of chromium can reach 88.91%, the mass ratio of chromium and iron is 2.56:1 for leaching 4h at room temperature with FeCl3 aqueous solution (100g/L). The leaching time of latter is longer but can realize the circulation effectively and reduce the waste liquid processing problem.1

In the present investigation, the oxidizing roasting process of chromite with sodium carbonate to prepare potassium dichromate crystals was studied in the microwave field with air, by heating the chromite and sodium carbonate. The chromite and sodium carbonate heated separately at 1000 °C in the microwave oven (frequency: 2.45 GHz; power 1.5 kW) in order to study the microwave absorption properties. The dielectric constant and dielectric loss factor of the chromite and sodium carbonate examined. Then, chromite with sodium carbonate taken in (1:2) ratio and heated at 750 °C. Thus obtained samples were characterized using various techniques includes Powder-XRD (XRD), Scanning Electron Microscopy (SEM), and X-ray fluorescence (XRF). The XRD pattern reveals the existence of Fe3O4, Fe2O3, NaAlO2, and Na2CrO4. The iron and aluminum were leached out as Fe2O3 and Al(OH)3 respectively. The resulting sample treated with the KCl to prepare potassium dichromate crystals. Finally, potassium dichromate crystals formed.