Affection Of Unburned Pulverized Coal On Characteristics Of Coke And Slag In Blast Furnace

In recent years,the economy of China continues to bear downward pressure and The steel industry is facing a series of difficulties,such as market oversupply,de-capacity requirements,industry competitive pressures increase,further increase the pressure on environmental protection.Iron and steel enterprises can continue to survive in the new period,increasing coal ratio is an effective way to reduce production cost of iron and steel enterprises.However,the increase of coal ratio will lead to the increase of unburned pulverized coal in the blast furnace,which will bring some influence on the blast furnace operation.This paper studied the pyrolysis process of pulverized coal including Shenhua bituminous coal,Yongcheng,Baishan,Jiaozuo three anthracite and the unburned pulverized coal were made by the same pulverized coal under the condition of oxygen.We also studied the reactivity of unburned pulverized coal with carbon dioxide and its effect on coke strength and blast furnace slag viscosity,getting the following results.(1)In oxygen conditions,thermogravimetric analysis results show that the bituminous coal has lower ignition temperature,burnout temperature,maximum weight loss rate temperature,better combustion characteristics and reactivity compared with the anthracite coal.Four kinds of unburned pulverized coal in comparison,Shenhua unburned pulverized coal has the lowest ignition temperature and burnout temperature,the highest combustion characteristic index and reactivity,but the temperature of maximum weight loss rate is high.Compared with the corresponding raw coal powder,the unburned pulverized coal has a high ignition temperature,maximum weight loss rate temperature and combustion characteristic index,and a low burnout temperature.(2)Shenhua unburned pulverized coal has the best reactivity for the reactivity of four unburned pulverized coal with carbon dioxide at 1000?,1050? and 1100? and the reactivity of four unburned pulverized coal with carbon dioxide increases with the increase of temperature.In addition,the reactivity of mixed unburnt pulverized coal with carbon dioxide is not a simple additive relation.(3)The interfacial chemical reaction is the main limiting step of the reaction between the unburned pulverized coal with carbon dioxide because of the reaction temperature is low,and the gas flow rate is faste,the resistance of the gas boundary layer and the product layer is small.Unburnt pulverized coal attached to the surface of coke will reacts with carbon dioxide prior to coke,which plays an important role in protecting coke in a certain extent.With the increase of unburned coal powder,the erosion of the edge of the coke has been improved,the hole becomes shallow,and the number of holes decreases gradually.(4)The viscosity and free running temperature of blast furnace slag can be decreased when blast furnace slag contains a small amount of unburned pulverized coal.But on the whole,The viscosity and free running temperature of blast furnace slag will increase with the increase of unburned pulverized coal,which is mainly because the addition of unburned pulverized coal has changed the concentration of complex anions in the slag,another is that unburned pulverized coal as suspended solid particles and heterogeneous phase will be formed in the cooling process in the blast furnace slag.