Introduction to the process of smelting metallic silicon in DC submerged arc furnace
March 09, 2024
Ingredients. The ratio of furnace materials should be determined based on chemical composition, particle size, water content, and furnace conditions through calculation and experience. Various reducing agents should be mixed in a certain proportion, and the amount of charcoal should be controlled at no less than 1/4 of the pure carbon content. The amount of bituminous coal and lignite should not exceed 1/4. When adding ingredients, attention should be paid to adjusting them in a timely manner according to changes in raw materials. Pay attention to the cleanliness of the raw materials, remove foreign objects, and prevent impurities from mixing into the materials. Weighing must be accurate.
Smelting operations. Prepare the materials according to the ingredient requirements, transport them to the front of the DC submerged arc furnace, and stack the wooden blocks separately. The order of ingredient weighing is: charcoal, petroleum coke, and silica. Adopting the operation of stewing, periodic centralized feeding, and thorough sinking. After the furnace material is simmered for a certain period of time, a ramming machine should be used to ramme the sintered material to sink. After the ramming is completed, new materials should be added in a concentrated manner. When adding materials, wooden blocks can be added first, and then the mixed furnace material can be quickly added around the electrodes and the furnace core area. The material surface should be added as a flat top cone, and after adding new materials, it should be simmered. Each shift sinks the material about 5-6 times, about once every hour, and the amount of new material added each time is about 1 hour.
Discharge and pouring. Before leaving the furnace, clean the flow channel thoroughly, place a carbon brick at the bottom of the ingot mold, brush lime or graphite powder inside the ingot mold, and place some crushed industrial silicon blocks on top to protect the ingot mold. The discharge time is determined based on the capacity, production conditions, management level, etc. of the ore heating furnace. Generally, a large furnace is discharged every 2 hours. Use a graphite rod to burn through the furnace, and the process takes about 15 minutes. After each furnace is produced, the furnace should be rammed with a ramming machine or manually.
Shutdown operation. Before stopping the furnace, all alloys should be discharged and the amount of wood blocks added to the batch should be appropriately increased. If the furnace is stopped for more than 8 hours, the material level should be appropriately reduced before stopping the furnace. To maintain the temperature of the furnace, first loosen the material surface and add wooden blocks before stopping the furnace. The amount of wood blocks added depends on the length of the stopping time, usually adding 50-100kg. If the stopping time is long, a certain amount of charcoal or petroleum coke can also be added for insulation.
Furnace condition judgment and adjustment. In actual production, the most important factor affecting furnace conditions is the amount of reducing agent used. The changes in furnace conditions are usually reflected in factors such as electrode insertion depth, current stability, surface fire on the furnace, and fluctuations in product quality.
Signs of normal furnace conditions: electrodes inserted deeply and steadily into the furnace material, stable current and voltage, low and stable arc sound inside the furnace; The firing area of the material surface is wide and uniform, the furnace material has good breathability, the material surface is soft and has a certain degree of sintering, and the degree of burning out of the furnace material is not significantly different. The soaking time is stable, and there is basically no "burning" or collapse phenomenon; When coming out of the furnace, the furnace is easy to open, the flow rate starts to increase, and then decreases uniformly, resulting in stable product output and quality.
