水分对富矿粉烧结制粒的影响机制

Influence mechanism of moisture on sintering granulation of ore-rich powder

富矿粉铁有品位高、杂质少的优点,但粒度较大,制粒效果较差。水分是影响烧结制粒的关键因素,研究了水分对富矿粉烧结制粒过程及料层透气性的影响,并提出了制粒小球破损机制的表征方法。通过对比分析制粒小球的湿强度、干强度和抗脱粉性能,获得了不同混合料水分条件下制粒小球长大模式及破损机制。研究结果表明:随混合料水分含量的增加,混合料制粒效果明显得到改善,颗粒长大指数GI增加,制粒小球粒度增大,粒度大于3 mm占比均明显增多,粒度小于1 mm占比降低,料层透气性也得到改善。不同粒级制粒小球内水的存在状态不同,粒度在3~8 mm制粒小球中液桥主要呈毛细管状分布,颗粒之间粘结力较大,制粒小球呈滚雪球模式长大,粘附层联结紧密,而粒度大于8 mm制粒小球主要以随机或非随机粘合模式长大,水在颗粒间的液桥多以液滴状存在,颗粒间粘结力较弱,易发生破损,因此在水分含量较高时制粒小球干强度KI降低。并通过对比分析运输和干燥过程制粒小球抗脱粉性能B1和B2,获得当混合料水分质量分数超过7.5%时,制粒小球破损主要受烧结料层的热气流冲击作用。综合考虑制粒效果和料层的透气性,富矿粉烧结混合料水分质量分数应在7.50%~8.05%之间。

Rich ore powder iron has the advantages of high grade and less impurities,but its particle size is large and its granulation effect is poor.Water is the key factors influencing the sintering granulating.The effects of moisture of sintering mixture on granulation process of ore-rich powder and permeability of material layer were studied.And the characterization method of pellet breakage mechanism was put forward.By comparing and analyzing the wet strength,dry strength and anti-depowder performance of pellet,the damage mechanism and grow mode of pellet under different moisture conditions was obtained.The results show that with the increase of water content in the mixture,the granulation effect of the mixture is significantly improved,the particle growth index GI increases,and the particle size of the granulation pellets increases.The proportion of pellets with a particle size greater than 3 mm increases significantly,while the proportion of pellets with a particle size less than 1 mm decreases.The permeability of the material layer is also improved.The permeability of the material layer is also improved.The presence of water in different particle sizes of pelletizing balls varies.In pelletizing balls with a particle size of 3 to 8 mm,the liquid bridges are mainly distributed in the form of capillaries,and the adhesive force among the particles is large.The pelletizing balls grow in a snowball mode,and the adhesive layer is tightly connected.However,pelletizing balls with particle size greater than 8 mm mainly grow in a random or non random adhesive mode.The liquid bridges of water between the particles mostly exist in the form of droplets,with weak adhesive force between the particles,which is prone to damage.Therefore,when the water content is high,the dry strength KI of the pelletizing pellets decreases.By comparing and analyzing the anti desulverization properties B1 and B2 of pelletizing pellets during transportation and drying,it was found that when the moisture content of the mixture exceeds 7.5 mass%,the breakage of pelletizing pellets is mainly affected by the impact of hot gas flow from the sintered material layer.Considering the granulation effect and the permeability of the material layer,the moisture content of the rich ore powder sintering mixture should be between 7.50% and 8.05%.