Study On The New Technology Of Aluminum Extraction From K-feldspar

As a large country of alumina production in China,alumina production capacity accounts for about 53% of the word,and the proportion is constantly expanding.However,because of the shortage of bauxite resources in China,a large number of bauxite ores need to be imported from abroad every year to meet the production demand of alumina industry.At present,the degree of external dependence is as high as 50%,which has influenced the sustainable development of China's alumina industry to some extent.Therefore,the comprehensive utilization of non-bauxite resources to extract alumina has become one of the hot topics.The K-feldspar in China has a large amount of reserves and is widely distributed.A large number of potassium extraction processes have been carried out,mainly in the field of potash fertilizer and building materials,and the high value utilization of aluminum and silicon elements in K-feldspar has been neglected.If the aluminum-silicon resources can be recovered on the basis of potassium extraction,the shortage of potash supply in China can be alleviated and a new way can be opened up for the raw materials of alumina production,which has good potential economic value and remarkable social benefit.Based on the characteristics of K-feldspar,a new technology for extracting alumina from K-feldspar by using potassium hydroxide activated K-feldspar and inorganic acid leaching is proposed in this thesis.Taking the extraction rate of alumina as a reference target,the thermodynamic characteristics of K-feldspar decomposition were analyzed.The effects of activation temperature,activation time,concentration of potassium hydroxide and excess rate on the leaching process of K-feldspar were investigated.The kinetic function of the dissolution of K-feldspar in the reaction system was obtained by using the principle of least square method.The mechanism of K-feldspar activation by potassium hydroxide was analyzed.The complex design of response surface method was used to optimize the process conditions.The results show that increasing the temperature of the reaction system is conducive to the activation of the reaction,the acid leaching process has a strong driving force.Aluminum and potassium enter the liquid phase in the form of ions,and the solid product is silicon dioxide.Increasing the activation temperature,concentration,time and excess rate can significantly improve the extraction rate of alumina.The integral mechanism of the kineticequation of the reaction system can be described by the model of shrinkage unreacted core.The apparent activation energy is determined to be 65.97 KJ / mol,and the controlled rate step of the leaching process is chemical reaction.The main factors affecting the activation of K-feldspar by potassium hydroxide are activation temperature,activation time,concentration and excess rate.The optimum process conditions are as follows: activation temperature is279.3 ?,the activation time is 143.1 min,the concentration is 45%,and the excess rate is90%.Under this condition,the extraction rate of alumina can reach 99.28%.