Research On The Furnace Profile Of Gas-based Direct Reduction Shaft Furnace

The current development situation of the iron and steel industry in our country showsthat the gas-based direct reduction ironmaking technology is the developing direction,especially the propose of coal-to-gas-shaft furnace ironmaking process, which is a suitableapproach for the ironmaking industry for our country. The gas-based direct reductionprocess have many advantages, such as high production efficiency, good product quality,less environmental pollution, without dependence on coking coal resources and so on,however, there is no one case of industrialized application in our country at present.Thanks to the coal-to-gas-shaft furnace ironmaking process which makes it possible forthe development of gas-based direct reduction ironmaking technology in our countrywhere little natural gas resources in turn hinders its development. The gas-based shaftfurnace is the core equipment where the direct reduction reaction occurs between iron oreand reduction gas. Therefore, it is of great significance to do research on this equipment topromote the development of the direct reduction ironmaking process in our county.In this paper, the basic parameters of the gas-based shaft furnace were put forwardreferring to the foreign gas-based direct reduction shaft furnace for Midrex and HYLironmaking process. Through the analysis of these parameters, the influence factors ofthem were found. Furthurmore, according to the studies on these factors, the expressionsof some of these parameters were achieved based on a design case,which make up a set ofdesign methods of a gas-based direct reduction shaft furnace. The analysis results showthat it is important to do research on reducibility and reduction swelling behavior of ironore pellets as the two play a key role in the design of the hight and the shaft angle ofreduction segment. In addition, the transfer regular of burden descent also should beconsidered.Experiment was conducted in simulated condition to study the swelling behavior ofiron ore pellets in gas-based direct reduction process. The results showed that the averagereduction degree rose to97%after about3hours and the reduction swelling index(RSI)increase first then decrease during the reduction process. The discrete element simulation analysis software EDEM was used to simulate thetransfer process of iron ore pellets to study the burden descent regular in shalt furnace. Thesimulated results showed that the speed of burden descent graduallt decreased from thecenter to the edge along the radial direction and different discharge rates and shaft anglehad little effect on this regular. Based on the experimental and simulation results, thefurnace profile was fitted to be a curve which was composed of three line segments fromtop to bottom in the design case.A one-dimensional gas-solid heat transfer model was established based on theextreme simplified assumptions to study the temperature field and the necessary hight ofthe cooling segment. At the same time, the3D physical models of the cooling part ofgas-based direct reduction shaft furnace were established to simulate the gas-solid heattransfer process. The sponge iron ore pellets were taken as porous media,the thermalnon-equilibrium model and the CFD software ANSYS FLUENT were used to calculate.During the simulating process, the research method of the shaft angle of cooling segmentwas obtained by optimizing the structure parameter. The gas flow field was also analyzedin both initial models and optimized models. The results show that the reasonable shaftangle of cooling segment is necessary to meet the cooling requirement and the reasonablegas distribution in cooling segment is that the gas velocity in the center should be a littlefaster than that on the edge of the shaft furnace.