Environmental Protection in The Calcium Silicon Production

Calcium Silicon Production Process

Calcium silicon is smelting in the submerged arc furnace which take the silica, lime, and reducing agent (semi-coke,  coal, etc).

ferro silicon calcium

CaO+SiO₂+3C=CaSi+3CO

The Calcium silicon production process is to unblock the outlet, feed and pound the furnace, control the power of the electric furnace for melting, control the rotation of the furnace body for melting and pouring, etc.

  1. After the raw materials are mixed, they are fed into the furnace through the top hopper and the material pipe. During the melting period, the materials can be pushed into the high temperature zone of the furnace through the furnace door in good time, and the materials can be pushed into the furnace to accelerate the melting.
  2. The composition of the alloy is judged by sampling at regular intervals, and the condition of the furnace is controlled. According to the power of the electric furnace, the furnace is timely released, and the alloy and slag flow into the ladle at the same time.
  3. The molten iron ladle is pulled to the pouring room, and the molten liquid alloy is poured into silicon-calcium alloy ingots by using the slag casting process, which is cooled, broken, packaged, and weighed, and put into the finished product warehouse.
  4. After the slag is cooled, it is crushed and returned to the furnace for smelting.

Exhaust gas mainly comes from dust in the material preparation system, exhaust gas at the material outlet, high-temperature flue gas from submerged arc furnaces and low-temperature flue gas from waste heat boilers. Wastewater mainly includes production cooling water, laboratory wastewater, floor flushing water and domestic sewage.

Solid waste mainly comes from dust collection by dust collectors, smelting slag, waste refractory materials, and domestic garbage. The noise mainly comes from crushers, fans, water pumps, elevators, conveyors, and other power equipment.

Calcium Silicon Pollutant Control Measures

ferro silicon calcium production

Waste Gas Pollution Prevention and Control Measures

The dust in the material preparation system is collected by the bag filter and returned to the batching bin, and the exhaust gas is emptied through the 18m high exhaust pipe.

The 33MVA submerged arc furnace of the main equipment adopts a semi-closed rotary type. There are 3 flue outlets on the top of the fume hood, and an electric lifting curtain is installed on the side wall to reduce the heat radiation of the furnace mouth. soot.

All the high-temperature flue gas from submerged arc furnace smelting enters the waste heat boiler to generate electricity through steam. The low-temperature flue gas of the waste heat boiler is purified by a bag filter and discharged through a 22m high exhaust stack. The submerged arc furnace has 6 outlets, which are used alternately. The 6 outlet smoke hoods are connected to form an annular flue, and at the same time, a smoke exhaust pipe is installed above each outlet, and each has an electric butterfly valve. The flue pipe is integrated into the electric furnace flue gas dust removal system.

On the top of the casting ingot mold, there is a fume exhaust hood with three side enclosures, and a large amount of smoke generated during the casting process is incorporated into the electric furnace flue gas dust removal system through the smoke exhaust pipe.

Water Pollution Prevention and Control Measures

In order to protect the normal operation of the electric furnace body, fume hood, electric furnace handle, electric furnace short network, transformer and dust removal fan, etc. working at high temperature, circulating cooling is required during the production process. It is indirectly cooled through the internal serpentine tube, and the cooling

The water is recycled after being cooled by the water purification circulation pool, and is not discharged outside.

The waste water for washing silica is recycled after sedimentation treatment and is not discharged outside.

After the floor washing water, laboratory wastewater and domestic sewage are treated by the secondary biochemical treatment device, they meet the emission concentration limit of the “Discharge Standard of Pollutants for Ferroalloy Industry” (GB28666-2012). They are used for green irrigation in the factory area in summer and stored in winter. Up to the standard discharge into the park drainage pipe network.

Solid Waste Prevention and Control Measures

During the smelting process, most of the materials in the raw materials are reduced to silicon-calcium alloy products, and only a small amount of oxidized substances become solid wastes in the form of slag phase. These oxidized substances are general wastes. Since the slag of silicon-calcium alloy smelting is an intermediate product, that is, calcium silicate and silicon carbide,

Calcium carbide and other substances can all be returned to the furnace for use in production and will not be discharged outside.

The dust collected by the dust collector at the batching station and the smelting slag are all returned to the submerged arc furnace for reuse; the dust collected by the dust collector of the waste heat boiler is pressed into balls and then exported as high-quality raw materials for the cement plant.

The waste refractory materials shall be handed over to the refractory material factory for recycling and reuse; the domestic waste shall be uniformly disposed of by the sanitation department of the park after collection.

Noise Control Measures

The selection of low-noise equipment is an essential requirement, and the purpose of controlling noise can be achieved from the source. For equipment with strong noise, install a soundproof cover or muffler; for vibrating equipment, install a shock absorber or damping device.

Pay attention to anti-vibration and anti-shock in pipeline design, thereby reducing material drop and vibration noise; at the same time, improve the smooth condition of air duct and fluid transmission, and reduce aerodynamic noise.

Measures such as sanitation protection forest belts and sound insulation forest belts are set up between the factory area and the office area, workshops or departments, and around the workshops where smoke and dust are generated. Through the layout of the general plan and reasonable layout, noise superposition and interference can be effectively prevented.

Environmental Management Measures

Construction of sewage standardization

In accordance with the regulations, put signs on each waste gas, waste water, and noise discharge outlets (sources), so that the environmental protection signs are obvious, and it is convenient for monitoring and inspection and public supervision.

Emergency management of environmental incidents

Combining the status of pollution sources, analysis of major pollutant factors, characteristics of pollutant hazards and possible types of environmental pollution incidents, etc., prepare emergency plans for environmental emergencies and strengthen emergency drills. According to the preventive measures proposed in the risk accident and disaster assessment in the environmental impact assessment, build a water storage pool and an accident pool for emergency response to environmental safety accidents, so as to be prepared. Construction of Environmental Protection System

In accordance with national standards and the requirements of superior management units, give priority to the adoption of local environmental protection standards, establish corporate environmental protection responsibility systems, publicity systems, management systems for pollution prevention facilities, statistical reporting systems for industrial pollutant emissions and emission reductions, and environmental protection file management systems, etc. Strengthen enterprise management, strengthen the responsibility of the main body, and implement accountability.

Environmental Impact

Surface Water Environment

The production process of smelting silicon-calcium alloy in submerged arc furnaces does not generate wastewater, only uses cooling water, and the cooling water is completely recycled after being cooled by the circulating water pool. A small amount of domestic sewage in the plant area is treated by biochemical treatment equipment and used for green irrigation or discharged up to standard, which has almost no impact on the surface water environment.

Ambient Air Quality

The high-temperature flue gas from submerged arc furnace smelting is all utilized by the waste heat boiler for steam power generation, and the low-temperature flue dust from the waste heat boiler is treated by the bag filter and discharged through the exhaust stack to meet the standard. A fixed collection hood is set above the outlet, and the exhaust fan sends the flue gas from the outlet into the exhaust pipe and enters the electric furnace flue gas dust removal system.

Conclusion

The commissioning of the 33MVA calcium silicon alloy submerged arc furnace smelting project marks a breakthrough in the production technology of large-scale silicon-calcium alloy electric furnaces in my country and is a new milestone in the development of silicon-calcium alloy electric furnaces. It is of great significance to promote the upgrading and sustainable development of the ferroalloy industry.

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