Coal based Direct Reduction Rotary Kiln Process Feb14

Coal based Direct Reduction Rotary Kiln Process...

Coal based Direct Reduction Rotary Kiln Process The coal based direct reduction rotary kiln process was developed for converting iron ore directly into metallic iron without the melting of the materials. The process has the advantage of low capital expenditure and no requirement of coking coal. The metallic iron in this process is produced by the reduction of iron oxide below the fusion temperature of iron ore (1535 deg C) by utilizing carbonaceous material present in the non-coking coal. As the iron ore is in direct contact with the reducing agent throughout the reduction process, it is often termed as direct reduced iron (DRI). The reduced product having high degree of metallization shows a ‘honeycomb structure’, due to which it is often called sponge iron. Coal based DRI plants are flexible with respect to plant location since non-coking coal is widely distributed in large deposits and is easy to transport. Most plants employ reduction process which is carried out in rotary kilns. These plants use wide variety of raw materials and non-coking coal. The quality of these materials has direct bearing on the process as well as the product. Some plants do not use iron ore directly. These plants use iron ore pellets in the rotary kiln. Raw material mix consisting of iron ore, dolomite and non-coking coal is fed at the one end of the rotary kiln and is heated by coal burners to produce DRI. The product DRI along with char (sometimes called dolo char) is taken out from the other end of the kiln. Apart from this, primary air and secondary air are supplied to the kiln to initiate the combustion and sustain the reaction process in the kiln. Raw materials The main raw materials for the production of DRI by...

Use of Direct Reduced Iron in Electric Arc Furnace May08

Use of Direct Reduced Iron in Electric Arc Furnace...

Use of Direct Reduced Iron in Electric Arc Furnace Electric arc furnace (EAF) operations have improved significantly over the past 30 – 40 years. Future significant improvements will need either new melting technologies or faster power input capabilities. In the meantime steel making in EAFs can benefit significantly from optimizing practices, increasing further the use of chemical energy and correctly using the direct reduced iron (DRI). Historically use of DRI in EAF was for the production of high quality low residuals steels with the anticipated expense of specific energy (kWh/ton), tap to tap time and loss of yield. Current educated use of DRI has developed practices which have demonstrated that DRI use can improve energy consumption, yields, productivity and above all operating costs. Factors related to the Specification of DRI During the production of DRI, oxygen is removed from iron ore reducing it to metallic iron and the more stable oxides such as silica (SiO2), alumina (Al2O3), lime (CaO) and magnesia (MgO) etc. As the oxygen is removed the concentration of these stable oxides increases when compared with their concentration in the feed material for the DRI. Hence the significant issues during steel making by the electric arc furnace (EAF) are as follows. Metallization Carbon content Gangue Non metallics coming with DRI (generally in case of DRI produced by rotary kiln) The chemical composition of the DRI determines such important factors as yield, slag weight, energy consumption, carbon and raw material feeding rates and oxygen usage. Analysis of DRI can vary based on the source and composition of iron ore used for making DRI, the process of making DRI and the process control practiced at the time of making DRI. DRI is available in the composition ranges as given below. Total Fe – 84.5...