The iron and steel industry is one of the largest emitters of carbon dioxide (CO2). CO2 emissions from steel production, which range between 5% and 15% of total country emissions in key developing countries (e.g. Brazil, China, India, Mexico, and South Africa), will continue to grow as these countries develop and as demand for steel products, automobiles, and appliances increases. CO2 is emitted during the reduction of iron oxide ores to produce pig iron in a blast furnace. This is achieved using the carbon in coke (sometimes coal or natural gas) as both the fuel and the reducing agent. Emissions also occur during steel production in electric arc furnaces (EAFs) from iron and steel scrap.
Note that, since steel contains carbon, some of the carbon in the reducing agent (coke or charcoal) is in fact sequestered in the finished product. During both iron and steel production processes, carbon dioxide is emitted during semi-finished steel preparation, finished product preparation, heat and electricity supply, and the handling and transport of intermediate and waste materials.
How can CO2 emissions in the steel industry be reduced?
- Switching from high carbon intensity fuel (heavy fuel and diesel or fuel oil No. 6 and No. 2) to natural gas and/or biomass: Reduces CO2 emissions per unit of energy consumed by approximately 30%.
- Cogeneration: Use of furnace exhaust gas (usually lost) to generate power.
- Use of charcoal instead of coal: Since charcoal can be a renewable resource with little net greenhouse gas (GHG) emissions, CO2 emissions from coal combustion are avoided.
- Direct fuel injection into the blast furnace: Pulverized coal injection or natural gas injection replaces the use of coke in the blast furnace, reducing coke production and saving energy consumed in coke making.
- Top pressure recovery turbines in the blast furnace: Use the pressure difference for the blast furnaces to produce electricity.
- Scrap preheating in the EAF: Reduces the power consumption of EAFs through using the waste heat of the furnace to preheat the scrap charge. The energy savings depend on the preheat temperature of the scrap.
- The use of an energy-monitoring and control system to regulate energy use: Site energy management systems for optimal energy recovery and distribution between various processes and plants/variable speed drives for flue gas control, pumps, fans or programmed heating of the coke ovens in order to reduce fuel consumption.
- Installing Consteel process: Controls raw materials and scrap feeding, as well as installing fine carbon/oxygen injection which will achieve 40% decrease in power consumption.
- Oxy-fuel burners/lancing: These can be installed in EAFs to reduce electricity consumption by substituting electricity with fuels, increase heat transfer and reduce heat losses.
- Thin slab casting: A new technology integrating casting and hot rolling in one process, which results in energy savings.
- Hot charging: Used to charge slabs at an elevated temperature into the reheating furnace of the hot rolling mill, which results in energy savings.
- Direct rolling: This is a variation of hot charging and thin slab casting. The standard slab is rolled directly in the hot strip mill, saving handling and energy costs. The energy savings are estimated to be roughly 50% of the energy costs of standard cold charging.
- Insulation of furnaces: Using ceramic low-thermal mass (LTM) insulation materials can reduce the heat losses through the walls more than conventional insulation materials.
- Coke dry quenching: Changing the traditional wet quenching of the coke with dry quenching with an inert gas (nitrogen) in order to recover the sensible heat of the coke for production of steam.