Solid-state Decarburization Of High-carbon Ferrochrome Powders Mixed With Calcium Carbonate By Microwave Heating And Its Kinetic Research

Medium and low carbon ferrochrome is indispensable raw material to produce Medium and low carbon alloy structural steel, gear, high pressure blower blades and valve plate, but metallurgical chromium slag produced in the preparation process is a kind of solid waste with serious pollution to the environment, so making liquid phase decarburization process of high-carbon ferrochrome is limited by environmental protection. The non-slag decarburization process of high-carbon ferrochrome can avoid the emissions of toxic chromium slag, using the characteristics of the powders material can rapid heating in microwave field, combining this characteristics of high-carbon ferrochrome powders by microwave and carbon dioxide produced by calcium carbonate powders decomposition in a closed system can achieve the rapid decarburization of high-carbon ferrochrome. The advantages of Solid-state decarburization of high-carbon ferrochrome powders by microwave heating are fast decarburization, high efficiency, simple process and no toxic chromium slag. Due to the production of medium and low carbon ferrochrome contain pure CaO, which has good effect of desulfurization and purification of molten steel. As a result, the research on solid-state decarburization kinetics of high-carbon ferrochrome powders by microwave heating has very good application foundation.In this experiment, choosing the calcium carbonate powders as solid decarburization reagent and the decarburization mole ratios were1:1and1:1.4, high-carbon ferrochrome with addition of calcium carbonates were heated to900℃,1000℃,1100℃,1200℃and held some certain times in the microwave heating field. Then, determinate carbon content of ferrochrome powders in different decarburization mixed materials, calculate the apparent activation energy of the solid-state decarburization reaction, as well as the heating characteristic in the microwave field. Explore the effect of various process parameters, and verify the presence of the non-thermal effects through the activation energy. Main research results were as follows:(1) The temperature curve of high-carbon ferrochrome had no change by addition a certain proportion of calcium carbonate powders. By adding calcium carbonate, improving the dispersion of high-carbon ferrochrome powders, increasing the volume, improving high-carbon ferrochrome powders absorption of microwave range. For two mixed materials of decarburization molar ratios were (nC:nCO2)1-1and1:1.4,the heating process can be divided into three stages in microwave heating field: Temperature basically was increased linearly in first stage of0℃to890℃, and the average heating rate was25℃·min-1; The heating curve was relatively flat in the second stage from890℃to950℃. That was because the decomposition of calcium carbonate absorbed a lot of heat, the heating rate of material was restricted and the average heating rate was only about5℃; The heating rate of material in microwave field increased in the stage of above950℃, because CaO had a relatively good absorbent of microwave than CaCO3.(2) For solid-state decarburization of high-carbon ferrochrome powders with calcium carbonate powders by microwave heating, improving decarburization molar ratio, the temperature in the microwave field and decarburization holding time were conducive to solid-state. decarburization of high-carbon ferrochrome powders, but the degree of oxidation of the decarburization material would be deepened at the same time. The solid-phase decarburization molar ratio (nc:nCO2) was1:1.0to1:1.4, the microwave heating temperature was1100℃and holding for60min were the best decarburization conditions, and the carbon content of ferrochromium powders in decarburization material could be achieved3.91%to1.71%, the decarbonization percent will reach up52.08%to79.04%.(3) Unreduced core model was applied to research the solid-state decarburization kinetics of high-carbon ferrochrome mixed calcium carbonate by microwave heating, Through the calculation and analysis, it was known that the decarburization reactions of solid-state decarburization of high-carbon ferrochrome mixed calcium carbonate by microwave heating match the first-order reaction equation well and the apparent activation energy was68.43KJ·mol-1.The effect of pre exponential factor is larger by improving decarburization molar ratio, For two mixed materials of decarburization molar ratios were (nc:nCO2)1:1and1:1.4, their pre-exponential factors of decarburization reaction were0.04s-1and0.14s-1.(4) The apparent activation energy of the solid-state decarburization reaction of high-carbon ferrochrome mixed calcium carbonate by microwave heating is significantly lower than the normal high temperature rapid carbon gasification reaction, so the microwave heating field not only has the microwave thermal effects, but also has the microwave non-thermal effects.