Research On Gasification Of Coke With H₂O Under Alkali Condition

Blast furnace process is responsible for energy consumption and CO₂ emission in a steel enterprise,meanwhile,CO₂ is harmful to the environment.In order to reduce the emission of CO₂,new blast furnace technology of injecting fuel containing hydrogen such as coke oven gas,plastics and natural gas has been studied.But large amount of hydrogen have produced from fast pyrolysis of hydrogen containing fuel in the blast furnace.Iron ore reduction by hydrogen generates a large amount of H₂O,which accelerates coke solution reaction.Besides,the circulation and accumulation of alkali metals further accelerate the solution loss of coke in blast furnace.Coke quality is facing a great challenge.In order to understand the effect of alkali metals on the reaction of coke with H₂O and the deterioration law of coke reacted with H₂O.In this study,the self-made gas-solid reaction device was used to study the solution reaction and deep reaction of coke after treatment with different concentrations of K₂CO₃ solution and Na₂CO₃solution.The controlling step of reaction process was analyzed.The volume density change of coke in different radial directions was measured.The changes of microstructure of coke were observed by scanning electron microscopy?SEM?,and the results were compared with those of CO₂.The following conclusions are obtained:?1?K₂CO₃,Na₂CO₃ accelerate the gasification rate of coke with H₂O and CO₂,and improve the reactivity,which aggravates the coke degradation degree.When the concentration of K₂CO₃ solution is 2%,4%and 6%,the CRI of coke with H₂O increases by 5.86%,14.52%and 19.59%respectively compared with the original coke,and CRI with CO₂ increases by 13.13%,23.05%and 27.94%respectively compared with the original coke.When concentration of Na₂CO₃ solution is 2%,4%and 6%,the CRI of coke with H₂O increases by 8.70%?14.35%and 17.20%respectively compared with original coke,and CRI with CO₂ respectively increases by12.15%,23.17%and 30.15%compared with original coke.The higher the concentration of K₂CO₃ and Na₂CO₃,the more powder with particle size less than 5mm after coke reaction,,and the CSR decreases.When concentration is the same,the catalytic effect of K₂CO₃,Na₂CO₃ on coke with H₂O is lower than that of CO₂.?2?The controlling step of coke reaction process on absorbed in the different concentrations of alkali metals is researched.Under the experimental conditions,the reaction process of coke with H₂O and CO₂ is controlled by interfacial chemical reaction.K₂CO₃,Na₂CO₃ decreases the activation energy of reaction.When the solution concentration is 2%,the activation energy Ea of coke adsorbed K₂CO₃,Na₂CO₃ with H₂O are decreased by 12.7 k J/mol and 9.26 k J/mol.?3?K₂CO₃,Na₂CO₃ accelerate the reaction of coke on the surface,the surface structure of coke is damaged seriously,the pore wall becomes loose and porous,coke pulverizes more seriously,pore collapses seriously,and the internal reaction of coke is reduced.When K₂CO₃,Na₂CO₃ concentration is the same,the coke reacted with H₂O in the internal reaction is lower than that with CO₂,small pores and medium pore are increased,large pores and connected pores are none.