Ferrosilicon is a high-energy and high-emission ferroalloy product, and its production and use face serious environmental problems. The following are the main environmental issues and measures in the ferrosilicon industry:
1. High energy consumption and carbon emissions
problem:
Each tonne of ferrosilicon produced consumes between 8,000 and 9,000 kWh of electricity, which is equivalent to 8-10 tonnes of CO₂ emissions (mainly from coal-fired power).
The annual global production of ferrosilicon is about 12 million tons, which accounts for more than 40% of carbon emissions from the ferroalloy industry.
Trouble
Dependence on fossil fuels (e.g., coal power in northwest China), which runs counter to the goal of "dual carbon."
The EU's Carbon Border Adjustment Mechanism (CBAM) could increase export spending.
Response
Transition to clean energy: Production is located in areas rich in hydropower resources, such as Norway and Russia.
Generation of thermal energy from waste: Recovery of waste gases (including CO) from the furnace and use them to generate electricity, which reduces dependence on the power grid.
2. Pollutant emissions
The main pollutants are:
Gases: carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen oxides (NOx).
Particles: silica dust (containing SiO₂) and coke ash, which can cause respiratory diseases.
Waste: 200-300 kg of slag is accounted for per ton of ferrosilicon, which is traditionally disposed of in landfills.
Problem
Small, obsolete furnaces (<25,000 kVA) do not have proper environmental protections and directly emit pollutants.
Decision
Closed electric furnace + dust removal system: the dust collection efficiency is 99%, and the recovered silicon powder is used in the production of building materials.
Slag processing: used as an alternative to gravel in road construction or as an additive to cement.
3. Water consumption and environmental pollution
Problems:
Water quenching process: Ferrosilicon granulation requires a large amount of cooling water, and the wastewater contains silicon powder and heavy metals.
Acid Wash Wastewater: Some companies produce acidic wastewater (pH<3) from purification equipment.
Answer
Dry granulation technology: air cooling instead of water quenching, saving more than 90% water.
Sewage Recycling System: After neutralization, the water is reused for cooling or dust removal.
4. Environmental impact of raw material
extraction Issues:
Silica mining: Destruction of vegetation and soil erosion (e.g., desertification in the silica mining area of Ningxia, China).
Coke production: The coking process releases carcinogens such as benzenes and polycyclic aromatic hydrocarbons.
Responses
Sustainable mining: Reclamation of mined-out areas and promotion of low-grade silica utilization technology.
Biomass Reducing Agent: Experiment to replace coke with charcoal and coconut shell coal to reduce carbon emissions.
5. Politics and pressure on the market
Modernization of the regulatory framework:
China: Elimination of submerged arc furnaces with a capacity of less than 25,000 kVA and complete modernization of ultra-low emission furnaces by 2025.
EU: REACH regulations limit emissions of heavy metals (lead, cadmium) and dust.
Green Trade Barriers:
Process industries (e.g., automotive and wind energy) require certification (e.g., EPD labeling) for "low-carbon ferrosilicon."
6. Technological Innovation and Industry Upgrading
(1) Low-carbon smelting technology
Hydrogen metallurgy test: replacement of part of the coke with hydrogen to reduce CO₂ emissions (pilot stage).
Plasma reduction: reduction of reaction temperature and increase of energy efficiency (reduction of energy consumption by 15-20%).
(2) Intelligence and the Circular Economy
Optimized control with artificial intelligence: real-time adjustment of the oven ratio and temperature to reduce energy losses (energy savings of 5 to 10%).
Ferrosilicon and photovoltaics connection: Some enterprises in Ningxia (China) use photovoltaics to directly supply ferrosilicon production.
(3) Greening of products
Low-impurity ferrosilicon: reduces secondary contamination in downstream steel production (e.g., low-aluminum FeSi75).
Recycled ferrosilicon: recycled by recycling steel scrap and silicon slag, which reduces the consumption of primary resources.
Comparison of global examples
Region Environmental Benefits Challenges
Norway 100% hydropower, very low carbon emissions High production costs, dependence on export markets
China Large-scale production, rapid technological iteration Dependence on coal-fired power, forced phase-out of small production capacity
India Low labor costs Weak compliance with environmental regulations, serious pollution problems
