Brief manufacturing process consists of following:
Steel is manufactured by the chemical reduction of iron ore, using an integrated steel manufacturing process or a direct reduction process. In the conventional integrated steel manufacturing process, the iron from the blast furnace is converted to steel in a basic oxygen furnace (BOF). Steel can also be made in an electric arc furnace (EAF) from scrap steel and, in some cases, from direct reduced iron. In the BOF process, coke making and iron making precede steel making; these steps are not necessary with an EAF. Pig iron is manufactured from sintered, pelletized, or lump iron ores using coke and limestone in a blast furnace. It is then fed to a BOF in molten form along with scrap metal, fluxes, alloys, and high-purity oxygen to manufacture steel
Broadly there are two steps in the manufacturing of steel
- Pig iron making
- Steel making
Potential pollutants from steel industries briefly are as follows
Air pollution
Pig iron manufacturing
Sintering operations can emit significant dust levels of about 20 kilograms per metric ton (kg/t) of steel. Pelletizing operations can emit dust levels of about 15 kg/t of steel. Air emissions from pig iron manufacturing in a blast furnace include particulate matter (PM), ranging from less than 10 kg/t of steel manufactured to 40 kg/t; sulfur oxides (SOx), mostly from sintering or pelletizing operations (1.5 kg/t of steel); nitrogen oxides (NOx), mainly from sintering and heating (1.2 kg/t of steel); hydrocarbons; carbon monoxide; in some cases dioxins (mostly from sintering operations); and hydrogen fluoride.
Steel manufacturing
Air emissions from steel manufacturing using the BOF may include PM (ranging from less than 15 kg/t to 30 kg/t of steel).
Water pollution
Pig iron manufacturing
In the conventional process without recirculation, wastewaters, including those from cooling operations, are generated at an average rate of 80 cubic meters per metric ton (m3/t) of steel manufactured. Major pollutants present in untreated wastewaters generated from the pig iron manufacture include total organic carbon typically 100–200 milligrams per liter, mg/l); total suspended solids (7,000 mg/l, 137 kg/t); dissolved solids; cyanide (15 mg/l); fluoride (1,000 mg/l); chemical oxygen demand, or COD (500 mg/l); and zinc (35 mg/l).
Steel manufacturing
Major pollutants in wastewaters generated from steel manufacturing using the BOF include total suspended solids (up to 4,000 mg/l, 1030 kg/t), lead (8 mg/l), chromium (5 mg/l), cadmium (0.4 mg/l), zinc (14 mg/l), fluoride (20 mg/l), and oil and grease.
The process generates effluents with high temperatures.
Solid waste
Process solid waste from the conventional process, including furnace slag and collected dust, is generated at an average rate ranging from 300 kg/t of steel manufactured to 500 kg/t, of which 30 kg may be considered hazardous depending on the concentration of heavy metals present. Approximately, 65% of BOF slag from steel manufacturing can be recycled in various industries such as building materials and, in some cases, mineral wool.
As reported by the Central Pollution Control Board, two of the twelve major integrated Iron and Steel Plants were found to be non-compliant. Directions under Section 5 of the Environment (Protection) Act, 1986 were issued to Bokaro Steel Plant, Bokaro and Directions under Section 18 (1) (b) of the Air (Prevention and Control of Pollution) Act, 1981 were issued to Jharkhand State Pollution Control Board for Indian Iron & Steel Company (IISCO) Steel Plant, Burnpur. In addition, Directions were also issued under Section 5 of the Environment (Protection) Act, 1986 to seven sponge iron plants and under Section 18(1) (b) of the Air (Prevention and Control of Pollution) Act, 1981 to the State Boards of Jharkhand, Chattisgarh, Odisha, West Bengal, Maharashtra and Andhra Pradesh to ensure compliance from sixteen sponge iron plants. The standards for iron and steel sector have been harmonized in 2012 with development / revision of standards for Blast Furnace and Basic Oxygen Furnace.
It depends on how the steel is made. When steel is made from iron ore, carbon dioxide is released from the blast furnace and during the basic oxygen process. Separation of oxygen from the air also requires energy.
Recycled steel goes to an electric furnace. The impact of producing the electricity for the electric furnace and for the production of oxygen depends on how the electricity is produced. If the electricity is produced in a hydro dam or in a nuclear power plant, the environmental impact is very small. But when coal is burned to make electricity, a large amount of carbon dioxide is released.
Very good, Nikhilesh. I use to work at an EAF facility and you leave out another pollutant. We would blow oxygen into the molten steel to reduce the carbon content of the steel. This would give off CO2 in the process. You would also get a lot of steel dust as well but this settles out of the air very quickly and does not carry far.
BOF facility, Gary Works in Gary, Indiana during its peak production years - http://www.constructionphotography.com/I...
EAF type facility
Tapping an electric furnace - http://sr.comps.fotosearch.com/comp/CSP/...
A ladle pulling away from a just tapped electric furnace - http://www.google.com/url?sa=i&rct=j&q=&...
An electric furnace melting in scrap steel - http://www.google.com/url?sa=i&rct=j&q=&...
cost of development
I which country?
In Pittsburgh there is none. They have all moved overseas. Thank you greenies.
