| Abstract:Brazilian hematite has gained world-wide recognition as an indispensable charge to replace magnetite due to its high grade iron,low price and abundant. Consequently, using imported Brazilian hematite with high quality to produce DRI plays great practical significance in China’s iron and steel enterprises development.Brazilian hematite concentrate has hige grade iron, less harmful impurities, but the granularity coarse, specific surface area only875cm2/g, it is made before the ball after the first milling high-pressure roller mill pretreatment, than the specific surface area of is up to1660cm2/g. The preheated pellets process parameters (0.15basicity):preheating at1150℃for4min, the compressive strength is1111N/pellet. Oxide pellets (0.15basicity) process parameters:preheating at1000℃for4min, roasting at1300℃for12min, the compressive strength is2649N/pellet.Preheated pellets(0.15basicity)direct reduction prosess was used,and compared with fire pellets direct reduction. Two types pellets which were restored at1050℃,C/Fe0.75and90min were achieved as follows:the total Fe, metallization degree, compressive strength of preheated pellets and oxidized pellets were94.17%,93.79%,1973N,94.32%,94.80%,869N/per, respectively.Using Brazilian hematite concentrate as raw material, preheated pellets coal-based direct reduction process was developed.Two types pellets have been used to do isothermal kinetics research. The results showed that:reduction rate of two types pellets is controlled by a mix mechanism of chemical reaction and diffusion when the reduction temperature ranges from800to1050℃. Coal-based isothermal reduction kinetics study shows that the roasting temperature of preheated pellets follows the chemical reaction control (n=1/4) mechanism. Activation energy reduces dramatically as a function of basicity. Adjusting pellet basicity, preheat consolidation performance of pellets can be improved and reduction performance be promoted, thus decreasing chemical reaction resistance. |
PDF Full Text Request