Corex gas , Corex process , Dome , DRI , export gas , Hot metal , Iron ore lump , Melter-Gasifier , non coking coal , pellets , Reduction furnace , Corex Process for Production of Iron During the late twentieth century, several new initiatives have been taken for the development of the smelting reduction technology which can become alternative route for the production of liquid iron hot metal since the conventional blast furnace BF ironmaking depends on metallurgical coal, which is required for producing BF coke needed for the production of hot metal in the blast furnace. Metallurgical coal is not only costly but is associated with environmental issues during its conversion to BF coke in the coke oven batteries. Smelting reduction process is that process which is based on smelting reduction technology and hence in this process the production of hot metal is carried out without the use of metallurgical coke. Corex process is one of these initiatives.
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The reason for such interest stems from the fact that the conventional blast furnace ironmaking depends on metallurgical coal, which is required for producing BF grade coke. Continued supply of metallurgical coal at a competitive price is becoming increasingly difficult with the depletion of coking coal reserves. Besides, the coke oven batteries are among the most environmentally hazardous reactors so far. COREX is the first and the only commercially established smelting-reduction process, as an alternative route to blast furnace, based on non-coking coal.
The COREX process offers high smelting intensity and hence higher productivity, ability to use various types of non-coking coals, use of iron ore fines to an extent, low net operating cost, possible generation of power or other alternative use of export gas generated from the ironmaking unit, besides being eco-friendly.
The world class performance of COREX plant so far has justified the vision and concept of such large investment in a cluster of industries co-existing. This conglomerate concept is the most adaptable in developing countries where there exists significant growing market for steel, power, cement, industrial gases, mining and mineral processing.
The reduction shaft is placed above the melter-gasifier and reduced iron bearing material descends by gravity. The volume of the reduction shaft and the melter-gasifier is about m3 and m3 respectively. Schematic diagram of a COREX plant Reduction Shaft: Iron ore, pellets and additives limestone and dolomite are continuously charged into the reduction shaft via lock hopper system located on the top of the shaft. Subsequently, six screws discharge the DRI from the reduction shaft into the melter-gasifier.
The DRI down pipes are uniformly distributed along the circumference near the top of the melter-gasifier so as to ensure uniform distribution of material over the char bed. Additionally non-coking coal, quartzite and required quantity of coke are continuously charged by means of lock hopper system. The operating pressure, in the melter-gasifier is in excess of 3 bars.
It is injected through the tuyeres, which gasifies the coal char generates CO. The hot gases ascend upward through the char bed. The sensible heat of the gases is transferred to the char bed, which is utilized for melting iron and slag and other metallurgical reactions.
The hot metal and slag are collected in the hearth. The efficiency of the furnace depends largely on the distribution of this gas in the char bed and utilization of the sensible heat of the gas.
The gas generated inside the melter-gasifier contains fine dust particles, which are separated in hot gas cyclones. The dust collected in the cyclones is recycled back to the melter-gasifier through the dust burners, where the dust is combusted with additional oxygen injected through the burners. There are four such dust burners located around the circumference of the melter-gasifier above the char bed.
A major part of this gas is subsequently fed to the reduction shaft. The excess gas is used to control the plant pressure. This excess gas and the reduction shaft top gas are mixed prior to the take over point and is termed as COREX export gas.
This gas is suitable for use for a wide range of applications like power generation etc. The production of export gas is around On the basis of these data, the Specific energy consumption SEC of the C plant can be calculated to be The blast furnace concept has been used, virtually splitting it into two at the cohesive zone interface. Accordingly a Corex plant has shaft unit, where iron ore pellets with or without some closely sized lump ore is reduced by gases emanating from the second unit to make hot sponge iron first stage.
This is mechanically transferred to the second unit or Melter-Gasifier where it is melted and carburised second stage by injection of both coal and oxygen. Since there is practically no CO2 or H2O in the gas leaving the Melter-Gasifier, we say that the degree of post combustion of Corex gas is zero, resulting in a gas rich in chemical energy. On the other hand, reduction of iron oxide by CO gas and carbon deposition reactions are exothermic in nature.
Maintaining dome temperature between oC to oC ensures the same. Burning of the coal char takes place near the tuyeres. The maximum temperature inside the melter-gasifier exists in front of the tuyeres. The following carbon gasification reactions takes place in the tuyeres area. Limitations include: i It has the limitation in distributing the coal and DRI in the optimised manner in the melter-gasifier.
This results in more peripheral flow of hot gases. There are three gas cleaning streams for cleaning the total gas generated in the process. This results in jamming of dust recycling systems as well as gas cleaning systems thereby resulting in more downtime of the plant.
Inferior quality of inputs result in frequent jamming of screws, DRI downpipes and DRS lines, affecting furnace availability.
The plant had various problems due to inexperience after the start-up in December After reconstruction and de-bugging, the plant has been successfully in operation since and was given over to ISCOR capacity , ktpa. Reconstruction of some parts and new operation conditions improved the performance greatly, leading to production of high quality iron, and high productivity and availability.
The clean excess fuel gas is used on site in furnaces and coke ovens. The COREX process proved to be very flexible with respect to the fuel rate, and additives addition , insensitive to high alkali content of the ore and burden , and easy to operate. This decision also seems to be based on the environmental performance of the COREX process, as the site is located near a nature preserve.
This plant, which includes a thin slab caster, began operation in January For Short Pudong steel at Luojing, near Shanghai started up a Corex C plant in early November , with a nominal production capacity of 1. The project was completed under the management of Siemens Metals Technologies within a period of 29 months.
It can replace the blast furnace, or can be used as a source of virgin iron for minimills. The economics of the Corex plant already provide an answer to future scrap and coke shortages, and the continually increasing demands placed on steel quality. The JVSL project is conceived as the one of the most modern, technologically efficient Greenfield plant with a capacity of 1. It is planned that the COREX export gas will be used for electrical power generation and for heating purposes within the steel complex.
The slag produced by the COREX plant is processed in the granulation plant and will be sold to cement industry. The quality slab produced will be suitable for hot strip mill which has been engineered by Daniel United of USA, incorporating the latest technology of coil box and a T walking beam furnace from Stein Heurty. A third generation mill is equipped with state of art electrical automation from Cegelac, USA and has all modern control features and equipment, to produce internationally competitive quality strips of 1.
The JVSL project is visualised on co-generation concept and the unique feature of the project is its technology-cum-management model. Environment friendly process.
Gojic and S.
The reason for such interest stems from the fact that the conventional blast furnace ironmaking depends on metallurgical coal, which is required for producing BF grade coke. Continued supply of metallurgical coal at a competitive price is becoming increasingly difficult with the depletion of coking coal reserves. Besides, the coke oven batteries are among the most environmentally hazardous reactors so far. COREX is the first and the only commercially established smelting-reduction process, as an alternative route to blast furnace, based on non-coking coal. The COREX process offers high smelting intensity and hence higher productivity, ability to use various types of non-coking coals, use of iron ore fines to an extent, low net operating cost, possible generation of power or other alternative use of export gas generated from the ironmaking unit, besides being eco-friendly.
The main reagents for the Corex process are iron ore , noncoking coal , and oxygen. The Melter gasifier has three main sections, the gaseous free board zone, the Char bed, and the hearth zone, and it has an effect on several stages in the process. First it serves to create the reduction gas by gasifying the coal with oxygen and then cooling it. After being reduced, the DRI is redirected to the char bed where the iron and slag are melted and then directed to the hearth zone.
Zolodal Corex Process for Production of Iron Advantages of the Corex process include i reduction in the specific investment cost compared with conventional blast furnace route of production, ii lower production cost, iii better environmental performance because of lower irpn and discharges, iv higher calorific value of export gas makes it suitable for use in a wide range of applications, v flexible with regards to the raw material uses since a wide variety of iron ores and coals can be used, vi good operational flexibility with respect to production capacity, production stops and raw material changes. Retrieved October 27, Nevertheless, it helped to overcome the critical demonstration stage for this smelting reduction technology. Compared with the traditional iron making process via the blast furnace route, the COREX process differs since non coking coal can be directly used for ore reduction and melting work, eliminating the need for coking plants. Views Read Edit View history. In the two-stage operation of the process DRI produced from prrocess shaft furnace is charged into a melter-gasifier for smelting. Because of many peripheral requirements, the total cost of a Corex project can be relatively high. Iron ore lump ore, pellets, or a mixture thereof is charged into the reduction shaft, where it is reduced to direct reduced iron DRI by the reduction gas in counter flow.