A method for producing high-carbon ferrochrome is provided to solve the problems of high requirements on raw materials and fuels, the low utilization rate of ore powder, and high energy consumption in the current ferroalloy smelting process.
The production of high carbon ferrochrome includes the following steps:
(1) High-carbon ferrochrome raw materials include chromite powder, coke powder and bentonite. The ratio of chromite powder to coke powder is 0.8-2.4 according to the carbon-oxygen ratio. The quality of bentonite is 1~5% of the mass of mineral powder. The raw materials are dried, finely ground and mixed, and made into green balls on the disc granulator, and the raw balls are preheated on the disc granulator to dry the chain grate;
(2) The rotary hearth furnace direct pre-reduction system pre-reduces the preheated and dried green pellets to obtain high-temperature high-carbon ferrochrome direct reduction pellets;
(3) The hot delivery system adds the high-temperature high-carbon ferrochromium direct reduction pellets to the submerged arc furnace silo, and then feeds the submerged arc furnace;
(4) The submerged arc furnace smelting system conducts deep reduction of high-temperature high-carbon ferrochromium direct reduction pellets and separates slag and iron to obtain finished products.
Beneficial effects: Compared with the existing technology, it has stronger adaptability to raw materials and lower requirements on fuel, and can use low calorific value and cheap gas (>800kcal/Nm3) to produce pre-reduced chromium ore pellets in rotary hearth furnace ore, the preheated and dried pellets are pre-reduced into high-carbon ferrochrome pellets in a rotary hearth furnace (the reduction rate can reach 70%), and the high-temperature high-carbon ferrochrome pellets are directly reduced (750-850 ℃)) to the submerged arc furnace for deep reduction and slag-iron separation smelting, effectively reducing the power consumption (2000~2200kwh/t high-carbon ferrochromium) and the amount of reducing agent (coke powder) in submerged arc furnace smelting, making full use of the production process waste heat of flue gas and sensible heat of pellets. The use of rotary hearth furnace pre-reduction can avoid problems such as ringing and pulverization of the rotary kiln, and effectively improve the quality and productivity of pellets. The use of regenerative combustion technology can increase the temperature in the furnace and reduce energy consumption and costs. Effectively improve the reduction rate of carbon ferrochrome.
The method for producing high-carbon ferrochrome comprises the following steps:
(1) Processing and preparation of high-carbon ferrochrome raw materials: chromite powder, coke powder, bentonite and other raw materials are batched, dried once, finely ground, mixed, and granulated on a disc granulator. Preheat and dry on the grating machine; the moisture of the raw materials after one drying is 1%~2%; the particle size of the raw materials after fine grinding is 0~0.074mm, and the content is 85%~100%; the moisture content of the mixed materials is 6%~8%, which is beneficial to the subsequent granulation process; after granulation, the content of green pellets with a particle size of 9~16mm reaches 95%, and the moisture content of green pellets is controlled at 12%~14%. The moisture content of the pellets is 0%~2%.
(2) Direct pre-reduction in the rotary hearth furnace: the pellets preheated and dried by the grate are sent to the rotary hearth furnace through the feeder, and the material flow is automatically controlled according to the bottom speed of the furnace to meet the requirements of continuous and uniform distribution in the furnace. Spread 1-2 layers of dry balls on the bottom. The bottom of the rotary hearth furnace rotates at a constant speed, and the dry balls placed on the bottom of the furnace pass through each section in turn. By adjusting the rotation speed of the furnace bottom, the time for the dry balls to stay in the furnace for reduction can be changed. The reduction time of blocks in the furnace is generally 20~45min. The round hearth of the rotary hearth furnace is divided into a charging area, a smoke exhaust area, a preheating area (500~600°C), a medium temperature reduction area (1000~1200°C), a high carbon ferrochrome high-temperature reduction area (1350~1450°C) and a discharge area. zone (800~900°C). The dry balls rotate with the bottom of the furnace, complete the reduction process after passing through the above-mentioned zones, and become high-carbon ferrochrome direct reduction pellets. The metallization rate of high-carbon ferrochromium direct reduction pellet iron produced by rotary hearth furnace is 92%, and the metallization rate of chromium is 70%. This step requires very little fuel, and the rotary hearth furnace can use low calorific value and cheap gas (>800kcal/Nm3) to produce pre-reduced chrome ore pellets. Realized in the furnace.