Sintering is a modern ventilation sintering process, the mixed material (iron ore, fuel, and flux return fines) together with a suitable amount of water, laid on the grate of the sintering machine, with a certain negative pressure ventilation after the ignition, The sintering process is carried out from top to bottom. The trolley in the sintering process was dissected and found to have four strips along the height of the layer as shown.
(1) Sinter belt. That is, the metallogenic belt, the main reaction is liquid phase condensation, mineral crystallization, preheating the air, the surface strength of this belt is poor, the reasons are:
1) The sintering temperature is low.
2) Due to the cold effect of air, the surface minerals are too late to devitrify, the glass is more porous, and the internal stress is very large, so the brittleness is crushed and crushed at the unloading end of the sintering machine to enter the ore. The thickness of the surface layer is generally 40 to 50 mm, and the surface strength can be improved only by the insulation measures of the igniter of the sintering machine. In recent years, due to the sintering operation using the high layers, the surface layer reduces the proportion of relatively less influence its overall strength of the sinter, in order to save coal gas, has not the insulation.
(2) Burning belt. That is, the sintering belt, the belt is a fuel burning belt, the temperature can reach 1100 ~ 1500 ° C. Here the mixture softens, melts and liquid phase formation. The layer has a thickness of 15 to 50 mm. This belt has a great influence on the yield and quality of the sintering process. The excessively wide band will affect the gas permeability of the layer, resulting in low yield; too narrow sintering temperature, insufficient liquid phase, poor bonding of sintered ore, and low strength. The width and width of this layer are affected by the particle size of the fuel and the amount of exhaust air.
(3) Preheat the drying belt. The main process is drying and preheating. The belt is characterized by rapid heat exchange, intense heat exchange by preheating, and the temperature of the exhaust gas quickly drops from 1500 ° C to 60-70 ° C. The main reaction in this zone is evaporation of water, decomposition of crystal water and limestone , redox of ore and reaction of paulownia Etc., the width of the belt is generally 20 to 40 mm.
(4) Moisture condensation zone. That is, the wet belt is used because the upper layer of high-temperature exhaust gas carries more water and gas, and when it enters the lower layer of cold material, the water is analyzed to form a moisture condensation zone. The belt affects the sintering gas permeability and destroys the prepared mixture pellets. The solution is to preheat the mixture.
The basic theory of the sintering process is:
1) The basic theory of chemical reaction kinetics is used to study the combustion of solid fuels during sintering.
2) The basic theory of heat transfer is used to study the temperature distribution and heat storage of the sintering process.
3) Analyze the relationship between the gas permeability of the material layer and the process parameters by the theory of gas mechanics.
4) with the basic theory of metallurgical engineering thermodynamics and minerals to study solid phase reaction sintering process, the liquid phase is formed and sintered ore mineralization mechanism like.
These research results make the sintering process more scientific and formulaic, and it is easy to establish a mathematical model of the sintering process, and also to indicate the direction of improving the yield and quality of sintering.
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