Progress and prospect on process and performance of direct reduction in gas-based shaft furnace
The direct reduction of gas based on shaft furnace has the characteristics of high hydrogen enrichment rate,short process and small environmental pollution,which is an important way to reduce carbon emission of iron and steel metallurgy by"replacing carbon with hydrogen".With the reduction gas source changing from natural gas to coke oven gas,coal to gas,chemical by-product H2,etc.,more gray hydrogen,blue hydrogen,green hydrogen preparation technology has laid the foundation for the global development of gas-based direct reduction.Based on the current situation of resources in China,the reduction process of iron oxide in hydrogen metallurgy technology of coke oven gas zero reforming shaft furnace is analyzed,and the change of pellet performance in the reduction process of gas-based shaft furnace is summarized in combination with the research status at home and abroad.The operating state of shaft furnace is analyzed,and the influence of different reducing gas composition on the reduction thermody-namics,dynamics,reduction performance and operating state of shaft furnace are grasped.It is found that lower gas pressure and higher temperature are beneficial to the reduction of iron oxide under zero reforming process of coke ov-en gas.Appropriately increasing the φ(H2)/φ(CO)in the reduction gas is helpful to reduce the reduction expansion of pellets rate and improve the compression resistance and high temperature thermal bonding performance of pellets during the reduction process.However,the reduction process is affected by many factors,and the reduction rate is not simply proportional to the H2 content in the reduction gas.Combined with the influence of reduction gas compo-sition on the flow distribution,temperature distribution,pressure distribution and other operating states of the shaft furnace,it is found that the temperature system and operating pressure need to be adjusted while regulating the gas composition.Reasonable gas composition not only needs to consider the reduction rate of iron oxides,but also needs to consider the reduction performance of pellets and the operation state of shaft furnace.The summarized results provide a theoretical basis for the implementation of gas-based shaft furnaces in China.
gas-based shaft furnacereduction processmetallurgical propertygas reformingrunning state
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