Theory and Practice of Sintering of Iron ore Nov25

Theory and Practice of Sintering of Iron ore...

Theory and Practice of Sintering of Iron ore Sintering of iron ore is a generic term which is used to describe the process whereby a sinter mix (raw mix or green mix) of iron ore fines, fluxes, fuel (coke breeze) and plant return fines (e.g. mill scale, blast furnace dust, and returned sinter fines etc.) are converted into a particular form of agglomerate. It consists of heating the sinter mix with a particle size of less than 10 mm to such a temperature that surface of each grain of the charge mix starts to melt and the formed melt creates liquid bridges between grains, which, after solidification, ensure formation of a solid porous material called sinter having a screened size normally of 5 mm to 30 mm (upper size can go upto 50 mm to suits local requirements), and which can withstand operating pressure and temperature environment inside the blast furnace (BF). The process of sintering is a thermal operation involving melting and assimilation reactions. The first stage of the sintering process is the formation of the melt which involves the reaction between fine iron ore particles and fluxes. The initial melt is generated from adhering fines during heating via reaction between iron ore and fluxes. Then, nucleus particles are partially assimilated or dissolved into the primary melt to form more melt. Before complete melting is achieved, the sintering temperature drops due to the short residence time at the maximum temperature and then the melt solidifies and mineral phases precipitate, resulting in the formation of the bonding phases. During the sintering process, the chemical reactions are taking place at high temperature and the iron ore and fluxes are combined together and form a sinter cake composed of iron ore, silico-ferrites of calcium and aluminum...

Iron Ore Sinter

Iron Ore Sinter  Iron ore sinter or simply called sinter is usually the major component of a blast furnace iron bearing burden material. Sinter normally consists of various mineral phases produced by sintering of iron ore fines with fluxes, metallurgical wastes and a solid fuel. Coke breeze is normally used as fuel in the sinter mix since it supplies necessary heat energy for sintering of sinter mix. Fig 1 shows a piece of sinter. Fig 1 A piece of sinter  In sintering, a shallow bed of fine particles is agglomerated by heat exchange and partial fusion of the still mass. Heat is generated by combustion of coke breeze admixed with the bed of iron ore fines, fluxes, and metallurgical wastes (sinter mix) being agglomerated. The combustion is initiated by igniting the fuel exposed at the surface of the bed, after which a narrow, high temperature zone is caused to move through the bed by an induced draft applied at the bottom of the bed. Within this narrow zone, the surfaces of adjacent particles reach fusion temperature, and gangue constituents form a semi liquid slag. The bonding is affected by a combination of fusion, grain growth and slag liquidation. The generation of volatiles from the fuel and flux materials creates a frothy condition and the incoming air quenches and solidifies the rear edge of the advancing fusion zone. The product sinter consists of a cellular mass of sinter mix materials bonded in a slag matrix. Important factors that affect the granulation efficiency and permeability of the sinter mix are water addition, particle size distribution, ore porosity, surface properties of the iron ore and the wettability of the iron ore. During sintering process, coke breeze increases the temperature of the sinter mix within the sinter bed...