What are the factors that affect the rate of reduction of iron ore?
Under a certain reduction condition, the reduction speed of small particle size is fast. Because of the small particle size and large specific surface area, the reduction rate is proportional to the specific surface area of the ore.. Practice has proved that the reduction of small ore is faster than the bulk ore, and the indirect reduction ratio is higher in the blast furnace, thus saving the coke consumption. But the particle size of the ore is too small, which will lead to poor permeability of the column. Porosity: the porosity of natural ore is different because of its genesis.
There are many factors that affect the reducibility of iron ore, such as grain size, porosity, mineral composition and structure, gangue composition and so on. We should make a comprehensive consideration according to the actual production situation.
Magnetite is relatively compact with low porosity and poor reducibility. When roasting, Fe3O4 is oxidized to Fe2O3, which leads to a certain degree of porosity of the ore block, increases porosity, and improves reducibility. Limonite is weathered by hematite and has loose tissue, high porosity and good reducibility. Pores in the ore have size, open or closed, thick wall or thin wall, but only when the openings in the ore for a long time, in order to obtain higher reducibility.
Mineral composition and structure: when hematite is reduced, the phase transition of Fe2O3 occurs, the lattice changes, the volume expands, and the sample cracks and increases the reducibility. When the magnetite is reduced, there is no such phenomenon of volume expansion. The oolitic structure of the natural ore has no obvious crystal, and the reduction reaction is carried out by layer by layer. If the ore is a belt structure, the reduction reaction is carried out at the same time at each layer, and the reduction rate is faster than the former. High grade pellets as a result of growing up in the sintering process of iron mineral grains, linked to the formation of a solid diffusion bonding structure, opening micro pores and uniform distribution, have very high reducibility. Acid sinter is a kind of bonded phase structure, which is difficult to restore and has low melting point. The cohesive phase closely surrounds iron minerals, which greatly hinders its reduction reaction and influences its reducibility.
