Fundamental Investigation Of The New Process Application Of Injecting Lime Kiln Exhaust Gas Into The Blast Furnace

Nowadays,the great amount of injection of blast furnace?BF?is mainly dependent on the pulverized coal,but this method results in the worse permeability of the actual BF gas due to the great amount of ash content in the pulverized coal.This paper aims at investigating the relationships of injecting amount of lime kiln exhaust gas,the mixed gas?converter gas+lime kiln exhaust gas?and theoretical combustion temperature.And formulae are established between theoretical combustion temperatures and various injecting systems of exhaust gas,and then the limited injecting amount is obtained.It is theoretically demonstrated that its injecting can achieve reduced carbon consumption for a blast furnace with a higher theoretical combustion temperature,which provides a new idea for the reutilization of exhaust gas and it is also theoretically proved that injecting lime kiln exhaust gas into the blast furnace can achieve reduced coke ratios and the minimum coke ratios of this process are calculated.By working out the limited coke ratios of theoretical calculated formulae and rist operated curve,the limited coke ratios of injecting processes are obtained and its results seem to be quite same.Thus,those new-type established formulae are theoretically recognized as reasonable calculated methods for various novelty processes of injecting exhaust gas.The conclusions are made as follows:?1?It is indicated that when the exhaust gas is injected,CO₂ can be completely converted into CO under the high temperatures of tuyere and raceway after conducting the tests and establishing the software computing models?FactSage?,and the conversed effects of the pulverized coal are better than the coke char.?2?The equations of thermal balance inside the tuyere raceway and carbon-oxygen balance in the region with high temperature are analyzed under various injecting systems of new process,and the equation of the theoretical coke ratio is established.What is most important thing is that this new-type transformed equation of the theoretical coke ratio lays the new theoretical foundation of establishing modeling for the processes of other types of gas injection.?3?By calculating the heat balance on the basis of reducing 200?of the theoretical combustion temperature,the maximum carbon consumption can be reduced by 8.5 kg/tFe under injecting the unmixed exhaust gas conditions,while the limited coke ratio can be reduced by 9.5 kg/tFe obtained from the rist curve.?4?By injecting the mixed exhaust gas into the BF,the maximum coke ratio can be reduced by 50.63 kg/tFe when the carbon consumption of direct reduction is 0 kg/tFe compared with the non-injection of the mixed exhaust gas and its maximum injecting amount is 445.27 m³ per ton Fe.?5?Compared with the traditional blast furnace,the new process has advantages in many aspects such as,reduce the coke ratios,reuse the waste resources,reduce the emissions of pollutants and increase the combined profits which have a better effect on the present production.The results show that,under the reduced 200?of the theoretical combustion temperature and the normal working conditions of the BF,the maximum carbon consumption can be reduced by 8.6 kg/tFe after exhaust gas injection upon a 3000m³ blast furnace.In contrast to the non-injection,this new process can reduce carbon consumptions,reuse the abandoned resources and increase the combined profits.Thus,it turns out to be a greater possibility of injecting the mixed exhaust gas into the BF based on the valuable results mentioned above.Based on the present depressions and the increasing environmental pressures of steel plants,injecting the exhaust gas can reduce the coke ratios,the costs,and relief the pressures,and it has important significance for the steel entrepreneurs.Under the increasing environmental and economic pressures,this new method has a bright prospect for reducing the coke ratios of the BF and can contribute to great profits to be reaped by steel plants in the future.