Experimental Study On Desiliconization Of Hot Metal With Carbon Dioxide Injection

With the continuous development of iron and steel industry in China,steel is on the increasingly stringent requirement of hot metal cleanliness.In order to meet the needs of some special steel smelting,requirements of silicon content is less than0.15%in hot metal.Due to the difficulty low silicon smelting in blast furnace, production of low silicon hot metal is produced by hot metal desiliconization pretreatment.Temperature drop of hot metal becomes large and impurity elements are taken into the hot metal easily when solid oxidant desilication is used.Based on this, this paper examines the use of CO2as an oxidant for removing silicon thermodynamic law, discusses the use of CO2as a hot metal desiliconization agents feasibility,in order to develop desiliconisation new technology to provide theoretical reference.This paper analysis the related reaction trend of CO2injected into hot metal from the point of view of thermodynamics and through high temperature test the effect of hot metal desiliconization were investigated at different temperature and CO2gas flow. According to the test results,the injection of CO2desilication reaction kinetics are discussed. Finally, the law of the outer furnace blowing CO2hot metal desiliconization and lower part of blast furnace blowing CO2heat balance are preliminary analysised through theoretical calculation.The main conclusions obtained in this paper are as follows:(1)According to the CO2and various substances in hot metal thermodynamic analysis of reaction obtained, low temperature is favorable for desiliconization but high temperature is helpful to decarburization.Theory of CO2reacting with silicon and carbon reaction equilibrium concentration is very low.The results of thermodynamics show that the CO2desilication is completely feasible in theory.(2)By studying on CO2desalination effect of different hot metal temperatures and different gas flows,the conclusions are as follows:gas side mass transfer is the restrictive step of CO2desiliconization reaction; hot metal temperature is higher, the smaller rate of silicon reduction when gas flow remains unchange. And at the same temperature, gas flow rate is greater, the greater the rate of silicon reduction.(3) Under the experimental conditions,due to the use of graphite crucible, carbon content appears first decreased and then increased regularity,because carburizing occurs at high temperature.The content of manganese, phosphorus and sulfur changes little at different temperatures and gas flow rates.(4)There are a lot of factors on CO2injection for hot metal temperature effects including the injected gas volume,gas utilization rate and allocation proportion of CO2reacting with carbon and silicon in hot metal.The change temperature regularity is obtained by changing the various factors in this paper.The results draw:temperature drop of hot metal increases when the injected gas volume increase and coefficient of gas utilization rise and the allocation proportion of CO2reacting with carbon.Gas volume per2L/kg increasing, temperature drop increases46℃when the gas is used completely and the gas fully reacting with carbon. Gas utilization rate reduced by25%each time, temperature drop increases72℃when gas volume is lOL/kg and the gas is used completely and the gas fully reacting with silicon.Carbon reaction with CO2proportion increased in20%,temperature drop increases52℃when gas volume is lOL/kg and the gas is used completely. According to the different factor to the effect of temperature drop, the results show that temperature drop is least when gas utilization rate is high and the carbon reaction ratio of CO2is low.(5)Based on the known blast furnace for the injection of CO2calculation,conclusion can be obtained:coke ratio increases12kg as the benchmark is380kg when gas volume gradually increase to7m3/tHM under the condition of keeping the heat loss of practical blast furnace constant because the reaction of CO2with carbon is endothermic and coke is consumed when CO2injected to blast furnace;tons of iron CO2injection volume increasing to7m3/tHM, the heat utilization factor KT increases from87.55%to88.74%, but percentage of high temperature zone heat loss which display the distribution of blast furnace heat to total heat loss decreases from56.25%to50.68%.