Comparative Research On Solid State Decarburization Kinetics Of High-carbon Ferrochrome Powder Containing Calcium Carbonate Between Microwave Heating And Conventional Heating

Medium and low carbon ferrochrome is mainly used in the production of low carbon structural steel, chrome steel, alloy structural steel. In recent years, with the kind of steel products refinement on species, demand for Medium and low carbon ferrochrome is also growing. Use the solid phase reaction makes carbon ferrochrome decarbonization, the requirements of reaction temperature is relatively low, the process is simple and convenient, the recovery rate of chrome is high and little impact on the environment. So the solid phase decarbonization of High-carbon ferrochrome powder increasing attention.The heating mechanism of microwave heating is different from that of conventional heating, and it affects the kinetics condition and activation energy of chemical reaction to some extent. Taking the high-carbon ferrochrome powder containing calcium carbonate as the research object, the kinetics behavior and activation energy of solid phase decarburization under different heating methods are compared in this paper. Use microwave oven and muffle furnace respectively to heat high-carbon ferrochrome powder containing calcium carbonate to900℃,1000℃,1100℃,1200℃, preserve heat and keep decarburization for0min,20min,40min and60min. During heating, record the change in temperature of the material per minute to grasp its temperature characteristics. After heating, when the Material cool to room temperature, Remove the material, observe its outward, and take a small part of the material for Measure the carbon content. Analyse the changes during heating and the decarbonization. The main conclusions of the test were as follows:(1) The high-carbon ferrochrome powder containing calcium carbonate is heated to1200℃, the curve of microwave heating field shows three phases: between room temperature to880℃, the heating rate is almost not change with steady increasing pace; Between880℃～950℃, since the thermal decomposition of calcium carbonate powder absorbs the heat, the heating rate of the material gradually decreases, as the decompose of calcium carbonate powder tends to completely, the heat absorption is reduce, the heating rate is increase; Between950℃-1200℃the microwave absorption rate of calcium oxide that generated from decomposition of calcium carbonate is better than the absorption rate of calcium carbonate powder. So the heating rate of the material is slightly increased compared to the first phase. The temperature rise characteristic curve of material in the conventional heating field presents two phases:From the room temperature to1000℃, the heating rate of material is kept constant, the temperature rises linearly. When the temperature exceed1000℃, the heating rate gradually decrease, Under the conditions of same power, the heating rate of microwave heating is significantly faster than conventional heating.(2) When the molar ratio of decarbonization, the heating temperature and holding time are same, the decarburization percentage of microwave heating field is significantly higher than that of conventional heating field. Under the same heating mechanism, the decarburization percentage of the molar ratio1:1.4is higher than that molar ratio1:1, the reaction rate of microwave heating is faster than conventional heating field, with the rising of heating temperature and holding time, the decarburization percentage of microwave heating field and conventional heating field all increase. Preserve heat and decarburize for60min at1200℃, in microwave heating, the decarburization percentage of molar ratio1:1is65.56%, the decarburization percentage of molar ratio1:1.4is82.97%; in conventional heating, the decarburization percentage of molar ratio1:1is58.21%, the decarburization percentage of molar ratio1:1.4is71.32%.(3) In microwave heating, for decarbonization materials of different molar ratio, the speed-control link of reaction is internal diffusion of CO2, the apparent activation energy of molar ratio1:1is106.31kJ·mol-1, the apparent activation energy of molar ratio1:1.4is109.76kJ·mol-1. In conventional heating, for decarbonization materials of different molar ratio, the speed-control link of reaction is interface chemical reaction, the apparent activation energy of molar ratio1:1is159.06kJ·mol-1, the apparent activation energy of molar ratio1:1.4is169.65kJ·mol-1. (4) Microwave heating field can improve the kinetics condition of solid phase decarburization, increase the reaction rate of solid phase decarburization of high-carbon ferrochrome powder containing calcium carbonate, promote the diffusion of carbon in high-carbon ferrochrome powder, and reduce the activation energy of decarburization reaction.