Study On The Influence Of CMC Composite Binder On The Strength Of Limonite Pellet

In recent years,the iron and steel industry has been in a state of steady development,and China’s iron ore resources are characterized by a large number of lean ore,various types,and difficulties in ore processing.This situation has led to our country’s dependence on importing high-grade iron ore resources from abroad.However,the progress of society is also accompanied by the consumption of resources.As a non-renewable resource,high-grade iron ore is increasingly depleted,and the efficient development and utilization of low-grade iron ore is imminent.Limonite is a typical low-grade ore with huge reserves.Because of its poor strength,it cannot meet the requirements of blast furnace charge after sintering or pellet roasting,so it has not been widely put into production.In this study,aiming at the problems of low iron grade and poor pellet strength of limonite,the binder was used as a breakthrough point to compare the effects of bentonite and CMC composite binders on the strength of limonite pellets.The research results are as follows.（1）Single factor experiments were used to investigate the factors influencing the compressive strength,drop strength,and bursting temperature of limonite green pellets,the performance of green pellets was optimized from the three aspects of choosing a reasonable binder ratio,suitable pelletizing parameters and suitable raw material particle size.It is determined that the bentonite content is 1.2 wt%,the water content of the green pellets is controlled at 9 wt%,the pelletizing time is 13 min,and the particle size of the ore powder<0.074mm accounts for 80%of the pure limonite pellets.（2）The roasting process of pure limonite pellets was optimized using a response method.Within the set factor range（roasting temperature 1250-1350℃,bentonite content 0.5-1.5%,pellet diameter 11-15 mm）,the optimized experimental conditions obtained are:The bentonite content is 1.3%,the calcination temperature is 1290℃,and the particle diameter is 13 mm.The predicted value of compressive strength of pellets is2130 N,and the experimental verification value of compressive strength of pellets is2034 N.Meet the performance requirements of pellets produced by the iron and steel industry.（3）The effect of different proportions of CMC in the CMC composite binder on the compressive strength of the pellets was studied at different calcination temperatures,and it was found that when the calcination temperature reached 1300℃,the composite binder with a CMC proportion of 0.075 wt%had a greater impact on the compressive strength of the pellets.The improvement is the most obvious,and the pellet strength reaches 2093N.The crystallization process of the composite binder limonite pellets with a CMC content of 0.075 wt%was analyzed by a mineral microscope.The results show that the crystallization effect of Fe₂O₃ in the pellets is better than that of the bentonite pellets with the increase of the CMC content.