Ferroalloy Submerged Arc Furnace Smelting Process Flow

Ferroalloy Submerged Arc Furnace Smelting Process Flow

Ferroalloy submerged arc furnace smelting is a key technology in the metallurgical industry for producing ferro-silicon, ferromanganese, ferrochromium, and other alloys. The reaction converts metal oxides in ores into alloys. The core lies in the utilization of high-temperature reduction processes, which appear standardized but in actual production, there are numerous hidden contradictions in details and technical bottlenecks. It requires deep deconstruction from three dimensions: raw materials, equipment, and operation.

The selection of raw materials directly determines smelting efficiency and cost. Taking ferrosilicon as an example, the purity of silica needs to be higher than 98%. However, in actual procurement, high-grade ores are expensive, and enterprises often mix in low-grade ores to reduce costs, leading to incomplete reactions in the furnace and difficulties in separating slag from iron. Coke, as a reducing agent, should have a fixed carbon content greater than 84%. However, due to frequent fluctuations in coke quality in the market, workers often compensate for insufficient activity by increasing the proportion, which in turn exacerbates electrode consumption and power consumption. A more subtle issue is the control of raw material particle size. Theoretically, silica should be 20-80mm and coke 5-25mm. However, when the crushing system is inefficient, fine powder entering the furnace can cause sintering of the material surface, hindering gas escape and leading to spraying accidents.

The design of the furnace body involves conflicts between thermodynamics and engineering. The squat and sturdy structure of the Ferroalloy Submerged Arc Furnace (SAF) can enhance heat exchange, but it leads to insufficient depth of the molten pool and inadequate metal settling time. A certain factory once increased the height of the furnace chamber from 2.8m to 3.2m, resulting in a 15% decrease in electrode current. However, the reduced temperature at the furnace bottom increased the viscosity of slag and iron, doubling the difficulty of tapping. The erosion mechanism of the furnace lining's magnesia brick deserves more attention. The slag line area experiences an erosion rate of 5-8cm per month, and traditional temperature measurement methods struggle to detect local burn-through risks in a timely manner. After a sudden furnace leakage accident in a certain enterprise, analysis revealed that a 30cm cavity had formed beneath the refractory material of electrode No. 3, which went undetected.

The control of operational parameters is fraught with challenges. Theoretically, the secondary voltage should be stabilized within the range of 180-220V. However, in actual production, operators often push the voltage to its upper limit in pursuit of higher output, leading to insufficient electrode insertion depth and an upward shift in the high-temperature zone. When a 12500kVA electric furnace increases the secondary voltage from 198V to 215V, daily output increases by 8 tons, but electrode paste consumption skyrockets by 25%. Three months later, cracks were discovered on the conductive jaw plate. Even more challenging is the control of moisture content in batching. During the rainy season, fluctuations in raw material moisture content can exceed 2%. If workers fail to adjust the batch in a timely manner, it can lead to current fluctuations at best and blockage of the material tube at worst. A southern factory once neglected changes in humidity, resulting in a large amount of CO being generated inside the furnace and not being discharged in time, which triggered an explosion on the material surface, causing a ten-hour production halt.

Environmental protection requirements are forcing technological innovation. Traditional flue gas treatment employs gravity dust removal combined with bag dust removal, which barely meets emission standards, but organic pollutants such as dioxins cannot be removed. After introducing an activated carbon injection system, a certain enterprise saw its operating costs increase by 300,000 yuan per month, forcing it to reduce the proportion of reducing agents, resulting in a 200-kWh increase in electricity consumption per ton of product. Wastewater treatment presents even more contradictions. The closed-loop system theoretically achieves zero emissions, but in actual operation, due to the efficiency decline of the cooling tower, 200 tons of high-salt wastewater still need to be discharged monthly. Balancing environmental supervision with corporate benefits has become a management challenge.

There is a physical limit to energy efficiency improvement. Theoretically, the power consumption for ferrosilicon smelting should be controlled at 8200kWh/t, but the actual average level hovers between 8500-8800kWh. An enterprise attempted to increase the proportion of pellets to improve reduction efficiency, reducing power consumption to 8350kWh, but due to the increased energy consumption for pellet preparation, the overall energy consumption increased by 2%. Preheating technology seems promising, as preheating ore to 600℃ can reduce consumption by 8%, but the investment recovery period for the rotary kiln exhaust heat utilization system is as long as 5 years, which is a barrier for many small and medium-sized enterprises. The more fundamental contradiction lies in the fact that the theoretical upper limit of thermal efficiency for a Submerged Arc Furnace is only 45%, with the remaining energy dissipated in the form of radiation and flue gas. Breaking through this bottleneck requires redesigning the entire energy transfer path.

The potential breakthrough direction in the future may lie in the integration of refined raw material control with intelligent operating systems. Establishing a raw material database to dynamically adjust the batching model, developing an intelligent electrode pressing and releasing system to optimize the molten pool shape, and utilizing microwave heating technology to improve the reduction kinetics conditions are all potential avenues. However, each innovation faces challenges related to cost and technological maturity. Industrial upgrading is destined to be a gradual improvement rather than a revolutionary breakthrough. A cutting-edge project attempts to install a plasma generator inside the ferroalloy submerged arc furnace to assist in reduction. Laboratory tests have shown a 12% reduction in power consumption, but the equipment maintenance cost is three times that of traditional electric furnaces, and it still requires ten years of accumulation before industrial application.