Effect of size of iron ore pellets on its reduction kinetics

A large number of industries in this world are now producing iron, either by the root of directly or indirectly. India is now not only producing iron ore pellets but also exporting it to other countries. Use of iron ore pellets not only increase the productivity of the plant but also produce good quality iron. So it is essential to know about the various factors which affect the reducibility of the iron ore pellet. In our project we aim at studying the effect of size of iron ore pellet on its reduction kinetics and in the course of our experimentation we aim at arriving at particular pellet size that gives both increases in productivity and decrease coke rate. Pellets are approximately spherical lumps formed by agglomeration of the crushed iron ore fines in presence of moisture and binder, on subsequent induration at 1300°C. In these times with the areas of iron ore use increasing, it is very important to use raw materials that not only increase the productivity of plant but also produce a better quality iron. Blast furnace raw materials have changed in character greatly in the last 2 or 3 decades. Formerly, they used to be raw iron ores, raw lime stone and coke. There are now being increasingly being replaced by pre fluxed sinter and pellets and liquid and gaseous fuels. Few examples of revolutionary changes brought to the present day iron making industries by use of pellets are Essar steel, TATA steel, Jindal Steel etc. Reduction of various sizes of iron ore pellets were carried out with non coking coal in a stainless steel reactor of size 10*5 cm. The stainless steel reactor was half filled with non coking coal powder of size -72# and the weighed oven dried pellet was placed centrally on this non coking coal powder bed and then the remaining portion of the reactor was filled with coal powder then it was covered with an air tight cover having a hole for escape of gases. The reactor was introduced into a muffle furnace and soaked there for 1 hour. The reactor was then cool inside the muffle furnace up to 1500C and then taken out and cooled in air and weight loss was calculated by electronic balance and hence % of reduction was calculated as [(Weight loss in iron ore pellet X 100)/ (Total initial O2 present in iron ore pellet with iron)] We can conclude that as we increase the size of iron ore pellet, this results in decrease in the reducibility of iron ore pellets. The most optimal size range for reducibility to be effective in industrial application is 10 mm to 20 mm

Modelling the Reduction of an Iron Ore-Coal Composite Pellet with Conduction and Convection in an Axisymmetric Temperature Field

A mathematical model of the coal-based direct reduction process of iron ore in a pellet composed of coal and iron ore mixture is investigated using a finite-control volume method. Heat transfer by conduction in the solid, convection by gaseous media inside, and radiation from the surroundings of the pellet are included in the model. The pellet is assumed to be spherical initially and the temperature around the pellet is taken to be symmetric about an axis passing through the centre. The parameters of the process, such as thermal conductivity, specific heats, and heats of the reaction, are all temperature dependent. The shrinkage/swelling of the pellet is also considered. We find that the effect of convection on the temperature and on the overall average reduction is small. However, the effect on the local concentration of the reaction components is significant. We predict that a uniform surrounding temperature field around the pellet yields a better average reduction