The New Composite Binder Strengthens The Properties Of Pellets And The Mechanism Of Action

High quality binder is an important condition to ensure the quality of pellets.As the main binder of pellet,the annual consumption of bentonite is more than 3 million t,and the average consumption of ton pellet is nearly 20 kg·t^-1.Using new composite materials to reduce the consumption of bentonite is an effective way to improve the quality and reduce the consumption of pellet.In this study,high-efficiency cohesive materials are selected to develop a new bentonite based composite binder.The influence law of the binder on pellet quality and hot metal production cost of blast furnace is studied,and the action mechanism of the composite binder to strengthen pellet performance is clarified,as to provide theoretical basis and data support for the application of the composite binder.A new type of high-efficiency composite binder was developed through the study on the compound ratio of bentonite and viscous material P.The results show that adding0.16-0.28‰viscous material P can replace 30-40%of bentonite,and the green pellet performance is the same;The structure-activity relationship between compound components and green pellet properties was studied by the combination of multiple linear regression and numerical analysis.Although the addition amount of P was only1/70-1/60 of bentonite,the standardized regression coefficient with drop number and shock temperature was higher than bentonite,which had a more significant impact on the two properties;Combined with the analysis of green pellet failure mechanism and mechanical properties,the multi-functional chain structure of P can be"embedded"to the surface of ore particles to strengthen the capillary force and viscosity in the pellet.During drying,a capillary is formed to facilitate the discharge of water vapor,but it is not conducive to the dry pellet strength.Therefore,the influence on the dry pellet strength is multifaceted.Aiming at the problem that the reduction of bentonite content is not conducive to the high-temperature consolidation of pellets,the effect of viscous material P on the preheating and roasting performance of pellets is studied.The results show that the addition of P can reduce the porosity of pellets and improve the strength of preheated and roasted pellets;The results show that P has a dual effect on the diffusion of oxidizing gas.On the one hand,P oxidizes and volatilizes at high temperature to form an appropriate amount of pores,which is conducive to the oxidation of O₂ and unreacted nuclei in the inner layer;On the other hand,it reduces the thermal conductivity of the pellet,delays the radial heat transfer rate of the pellet,avoids the formation of too thick dense oxide shell in the outer layer and reduces the oxidation degree of the inner layer of the pellet.The results of metallurgical properties of composite binder pellets show that the addition of viscous material P has little effect on the reducibility of pellets,and the reduction expansion index increases slightly,but it still belongs to the normal expansion category;A significant reduction in the amount of bentonite has a great impact on the softening droplet performance of the pellets,the droplet range widens and the eigenvalue s increases significantly.Considering the low proportion of pellets into the furnace,the impact on the comprehensive charge is limited.Using the independently developed hot metal cost accounting model,the influence law of bentonite dosage on pellet grade and hot metal comprehensive cost is studied.The results show that when the bentonite dosage is reduced from 2.0%to 1.0%,the pellet grade is increased by0.57%and the comprehensive charge iron grade is increased by 0.08%.Considering the production of 1t hot metal,the comprehensive cost of hot metal is reduced by 2.44yuan/t,and the amount of blast furnace raw materials is unchanged,The comprehensive cost of molten iron is reduced by 5.10 yuan/t,which has broad economic benefits.