The Research On Relationship Of Furnace Profile And Behavior In Gas-based Direct Reduction Shaft

As with the economic development, the country has become a steel superpower, butnot a fine steel power. In China, restructuring structures of steel products need to be doneurgently as well as the pressure reduction of coking coal, and coal gas-based directreduction shaft furnace (DRI) technology has developed into one effective solution for thisproblem. During the DRI production process, complex physical and chemical reactionsoccur in the furnace, and DRI quality is affected by technological and device parameters,including heat exchange between reducing gas and materials, reducing gas flow, materialmovement, etc. To solve the above problems, some study works have been done asfollows:Gas consumption for reduction reaction is compared with that for heat balance to getthe minimum one. Then finite element model is established on the basis of domestic BLpilot testing equipment and process parameters. Fluid dynamics software is applied toanalyze gas-solid heat transfer process in the shaft furnace with the consideration ofchemical reaction heat. Temperature distribution and heating up curves in shaft furnace areobtained in the case of different gas flows. The relationship of reduction temperaturedistribution with reducing gas components and temperature is also analyzed, whichprovides a reference for subsequent analyses.The discussion on the coupling problem of fluid and solid is made here as well asreduction gas flow distribution, and the fluid dynamics software is chosen here. Pellets aresimplified as porous media in this simulation, and inertial resistance coefficient and theviscous drag coefficient obtained through the test are served as inputted parameters. Theeffects of process parameters on furnace pressure and turbulent flow in transition sectionare studied by calculating neural network mappings. Establishing optimization objectivefunction, factors of ideal flow distribution in shaft furnace are found out through geneticalgorithm optimization, which provides a numerical reference for parameters selectionduring the furnace design.Jostling discrete element model is established to simulate the mutual extrusion and collision during pellets movements in the shaft furnace after the determination of materialphysical parameters. Bed shape at different discharge speeds are analyzed through discreteelement software. Velocity distribution diagrams are obtained under different dischargerates, and visualization of material movement in the furnace is achieved. It is useful todetermine the exact height of the vertical shaft furnace and provides theoretical support forthe shaft furnace design.According to experiment requirements, a pellets reduction performance test bed isestablished. Direct reduction reaction speed controlling process is analyzed dynamically,metallurgical performance tests of pellets at Shouqinlonghui are conducted under differenttemperature conditions and reducing atmosphere to measure the reduction property andexpansion coefficient during reduction process. The reduction and expansion process arestudied, which could provide supports for the furnace profile research theoretically andexperimentally. Then a method for determining the height and inner profile of reductionsection is formed by combining with theoretical analysis and experimental results.