Study On Purification Process Of Silicon Tetrachloride For Optical Fiber Manufacture

With the rapid development of Polysilicon industry, a large amount of silicon tetrachloride as by-product is also manufactured which has serious pollution to the environment. So how to deal with these by-products has become an urgency to be solved. In this paper, high purity silicon tetrachloride refining process, which can be used for manufacturing optical fiber, is established. By the methods of simulation, optimization and improvement using Aspen Plus software, good product is obtained. The main research work and results are as follows:(1)For the quality requirement of high purity optical fiber, high purity silicon tetrachloride refining process is designed and simulated. the optimal operating parameters, including stage number, feed stage number, reflux ratio and so on, is discussed. the purity of tetrachloride can reach as high as 99.99999%.(2) The high purity silicon tetrachloride refining process is improved by applying the different pressure thermally coupled distillation. By the comparison of both process, the improved process can both save energy over 40% and reduce equipment investment. Therefore, different pressure thermally coupled distillation is an energy saving and equipment saving process.(3)The divided wall column is innovatively proposed for refining high purity silicon tetrachloride. Multifrac module of ASPEN PLUS software is used to simulate this process and optimize the operating parameters. The most optimal results are as follows: plate number of main column is 150 and that of pre-fractionator is 119,connection stage is 20 th and 139 th, feed stage is 69,side stage is 80, the ratio of reflux to feed is 6, the liquid distribution ratio is 1.8, the vapor distribution ratio is 0.7. Results shows that the purity of tetrachloride is better than the original process, energy consumption is reduced over 20% and equipment investment is also reduced. So divided wall column for refining high purity silicon tetrachloride is an energy-saving and efficient separation technology.(4)the adsorption refining method for high purity silicon tetrachloride is exploratory studied. the boron impurities adsorb methods is researched. The factors,including types of absorbents, dosage of absorbents, moisture content of absorbents, absorption temperature and absorption time, are discussed. The results show that A21 resin is the best absorbent, adsorption process is an exothermic process, adsorption equilibrium can be reached fast and the moisture in absorbent will rapid react with silicon tetrachloride which has an bad effect on absorption process. For the more, absorption kinetics is also discussed in this paper. According to the data fitting result, the Lagergren second-order absorption kinetics is well fitting the absorption process...