Experimental Study On Boiling Chlorination Kinetics Of TiO₂ With Carbon

Boiling chlorination is recognized as the world’s advanced chlorination technology due to its high efficiency and environmental protection,which has been monopolized by a few foreign companies.China is a country with large titanium resources,but the proportion of boiling chlorination production process is very small,and most of the production technologies are introduced from abroad.So far,the systematic research on boiling chlorination in China is not mature,and there is still a large gap in the research on the reaction mechanism of chlorination with carbon.In this paper,TiO₂was taken as the research object,the thermodynamic calculation of TiO₂chlorination reaction was carried out,and the orthogonal experiment was designed with gas velocity,temperature,carbon ratio,particle size composition and other factors.Through the weight detection of chlorination reaction process and the XRD and EDS detection of slag samples,the optimal process conditions of carbon chlorination reaction were explored.The effect of gas velocity,temperature,carbon ratio,particle size composition,chlorine concentration,calcium and magnesium content on chlorination reaction and the kinetics of chlorination process were explored.The main conclusions are as follows:1 According to the thermodynamic calculation,only the low-valence oxides Ti₃O₅,Ti₂O₃,TiO and other titanium oxides can react directly with chlorine,while TiO₂needs to add the reducing agent C to carry out the chlorination reaction,and the chlorination priority order is from the low-valence oxides of titanium to the high-valence oxides.When impurity oxides participate in chlorination reaction,the chlorination priority order is CaO>MgO>Fe₂O₃>FeO>TiO₂>Al₂O₃>SiO₂.At the reaction temperature（800℃～1100℃）,CO and TiCl₄were preferentially generated by the chlorination of TiO₂with carbon,and the partial pressure of CO was higher than that of CO₂.The gas phase equilibrium calculation showed that excessive C and Cl₂had no effect on the reaction system.2 Through the orthogonal experiment results,it was found that the order of influencing factors determining the chlorination rate of TiO₂and the average reaction rate was as follows:gas velocity>petroleum coke ratio>particle size composition>temperature.The optimized combination obtained by comprehensive analysis was as follows:temperature 900℃,gas velocity 0.20m/s,petroleum coke ratio TiO₂:C=70:30,and particle size composition of TiO₂and petroleum coke 60-160 mesh:40-140 mesh.The chlorination rate of the optimized combination was 95.44%after experimental verification.3 The experimental results of single factor on the chlorination rate of TiO₂showed that the chlorination rate could be increased to 98%by using 100%chlorine concentration on the basis of the optimal combination,while the chlorination reaction rate could be accelerated by carrying TiCl₄with fluidized gas,but the weight loss rate and chlorination rate would decrease.There are two forms of calcium magnesium bonded materials,and the chlorination rate decreases with the increase of calcium magnesium content.4 Kinetic studies on the chlorination of TiO₂showed that the chlorination of TiO2 followed the shrinking unreacted core model without solid product layer;In the range of 800℃～1000℃,the activation energy of TiO₂chlorination reaction was 45.28k J/（mol·K）,the pre-exponential factor A was-0.73,and the reaction rate constant k_s=0.2×10（-19663/RT）.