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Blast furnace gas
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<p>Blast furnace gas (BFG) is a by-product of <a href="/facts/Blast_furnaces/DJzUB2EG">blast furnaces</a> that is generated when the <a href="/facts/Iron_ore/rQMEvgMh">iron ore</a> is <a href="/facts/Redox/Pyd5RVcj">reduced</a> with <a href="/facts/Coke_(fuel)/vD8xjd0m">coke</a> to metallic <a href="/facts/Iron/QK1JYy8E">iron</a>. It has a very low <a href="/facts/Heating_value/HdQX0mPP">heating value</a>, about 3.5 MJ/m3 (93 <a href="/facts/BTU/GwIjRAPz">BTU</a>/cu.ft), because it consists of about 51 vol% <a href="/facts/Nitrogen/Nf1QpGDz">nitrogen</a> and 22 vol% <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a>, which are not flammable. The rest amounts to around 22 vol% <a href="/facts/Carbon_monoxide/CKuLtEMJ">carbon monoxide</a>, which has a fairly low heating value already and 5 vol% <a href="/facts/Hydrogen/BoYHjl0J">hydrogen</a>. Per ton of steel produced via the blast furnace route, 2.5 to 3.5 tons of blast furnace gas is produced. It is commonly used as a fuel within the <a href="/facts/Steel/aN6qWo4H">steel</a> works, but it can be used in <a href="/facts/Boiler/uPqTq0I6">boilers</a> and <a href="/facts/Power_plant/vYeVY1fD">power plants</a> equipped to burn it. It may be combined with <a href="/facts/Natural_gas/9MYQ7NAP">natural gas</a> or coke oven gas before combustion or a flame support with richer gas or oil is provided to sustain combustion. <a href="/facts/Atmospheric_particulate_matter/RleGr5E6">Particulate matter</a> is removed so that it can be burned more cleanly. Blast furnace gas is sometimes <a href="/facts/Gas_flare/8fILYdxp">flared</a> without generating <a href="/facts/Heat/FjDGssCs">heat</a> or <a href="/facts/Electricity/hNC8D65W">electricity</a>. </p><p>Blast furnace gas is generated at higher pressure and at about 100–150 °C (212–302 °F) in a modern blast furnace. This pressure is utilized to operate a generator (a top-gas-pressure recovery turbine (TRT)), which can generate electrical energy up to 35 kWh/t of <a href="/facts/Pig_iron/bxLL2NaR">pig iron</a> without burning any fuel. Dry type TRTs can generate more power than wet type TRTs. </p><p>The auto ignition point of blast furnace gas is approximate 630–650 °C (1,166–1,202 °F) and it has a lower explosive limit (LEL) of 27% and an upper explosive limit (UEL) of 75% in an air-gas mixture at normal temperature and pressure. </p><p>The high concentration of carbon monoxide makes the gas hazardous. </p>