Converter Gas, its Characteristics and Safety Requirements...

Converter Gas, its Characteristics and Safety Requirements During the process of steel making in the basic oxygen furnace (BOF), significant amount of gases, rich in carbon monoxide content, are generated during the blow time at a temperature of 950 deg C. This gas is termed as converter gas or BOF gas. Converter gas is also known as LD gas. It is a byproduct gas produced during the production of liquid steel in a basic oxygen furnace (converter), where impurities of hot metal are oxidized with oxygen gas. The main constituents of converter gas are carbon mono oxide (CO), carbon di oxide (CO2), oxygen (O2) and nitrogen (N2).  Composition wise it is similar to blast furnace gas but with lesser percentage of nitrogen in it. Converter gas is dust laden at the converter mouth. The dust content is around 100 to 120 g/N cum. The recovered converter gas is cleaned in a venturi scrubber using water, followed by processing in the mist eliminators. The gas is then stored in gas holder for steady supply and cleaned further in the electrostatic precipitators (ESP) and finally fed to the gas distribution system. Wet type of gas cleaning plants have capabilities to reduce the dust content of the gas to a level of 5 mg/N cum. The composition of the gas varies from start to the end of the blow and this is a function of the blow time. In the oxygen rich phase (air ratio= 1) at the beginning and at the end of the blowing period the primary gas is burned completely and no gas is recovered during this period. During CO rich phase (air ratio less than 1) only partial oxidation takes place and a combustible waste gas is formed containing CO, H2, CO2 and...

Understanding Steel Making Operations  in Basic Oxygen Furnace Mar02

Understanding Steel Making Operations in Basic Oxygen Furnace...

Understanding Steel Making Operations  in Basic Oxygen Furnace  Steel making operation in the basic oxygen furnace (BOF) is also sometimes called basic oxygen steel making (BOS). This is the most powerful and effective steel making technology in the world. Around 71 % of the crude steel is made by this process. BOF process was developed in Austria in the early 1950s at the two Austrian steelworks at Linz and Donawitz and hence the BOF process is also called LD (first letters of the two cities) steel making. There exist several variations on the BOF process. The main are top blowing, bottom blowing, and a combination of the two which is known as combined blowing. The BOF process is autogenous, or self sufficient in energy, converts liquid iron (hot metal) into steel using gaseous oxygen (O2) to oxidize the unwanted impurities in hot metal (HM). The O2 used must be of high purity, usually 99.5% minimum, otherwise the steel may absorb harmful nitrogen (N2). The primary raw materials for the BOF are generally HM (around 80 % or more) from the blast furnace and the remaining steel scrap. These are charged into the BOF vessel. O2 is blown into the BOF at supersonic velocities. It oxidizes the carbon (C) and silicon (Si) contained in the HM liberating great quantities of heat which melts the scrap. There are lesser energy contributions from the oxidation of iron(Fe), manganese (Mn), and phosphorus (P). The flux used in this process is primarily calcined lime ( with CaO content of more than 92 %). This lime is produced by the calcining of limestone with low silica (SiO2) content. The post combustion of carbon monoxide (CO) as it exits the converter also transmits heat back to the bath. The product of...

Fuel gases used in steel industry...

Fuel gases used in steel industry Fuel gas is a fuel which under ordinary conditions is in the form of gas. Fuel gases are used in steel plants for different applications which include (i) a source of heat (ii) as a reductant and (iii) cutting and welding application. Fuel gases usually used in steel industry are natural gas (NG), liquefied petroleum gas (LPG), acetylene, by product gases (blast furnace gas, coke oven gas and converter gas). Natural gas Natural gas is a gaseous fossil fuel which is extracted from deposits in the earth. It is a mixture of hydro carbons consisting primarily of methane (generally greater than 80 %) but includes varying amounts of other higher alkanes such as ethane, propane and butane etc. It may even contain some small percentage of nitrogen, carbon dioxide and hydrogen sulphide. It is an odorless, colourless, tasteless and non toxic gas. Natural gas is lighter than air and it burns with a clean blue flame when mixed with the requisite amount of air and ignited. It is considered one of the cleanest burning fuels. On burning it produces primarily heat, carbon dioxide and water. Quantities of natural gas are measured in normal cubic meters (corresponding to 0 deg C and I Kg/Sq cm pressure) or standard cubic feet (corresponding to 16 deg C and 14.73 psia pressures). The higher heat value of one cubic meter of natural gas varies from around 9500 Kcal to 10,000 Kcal. Its density is around 0.85 Kg/Cum. The main usage of natural gas in the steel industry is in iron making. For production of direct reduced iron it is reformed to produce reducing gases which are then used for the reduction of iron ore. The main reforming reactions are as follows. 2CH4...