Thermal Characteristic Analysis Of Vertical CVD Process To Produce Silica Glass

Chemical Vapor Deposition (CVD) is an important process to the production ofquartz glass. Produced by hydrolysis of silicon tetrachloride in hydrogen-oxygenflame of high temperature, quartz glass deposited is of great quality with theadvantage of great size, good performance, high purity and low cost. However, therewill be some types of defects in the glass due to the limitation of this very producingtechnology. The main content of this dissertation is about how to minimize defects,optimize performance, further reduce operating costs, and increase the depositionrate of quartz glass. Recurring to the software of Fluent, simulation and analysis areapplied to vertical CVD glass production. Multi-step chemical reactions, turbulence,mass transfer, and heat transfer including thermal conduction, convection, radiationand condensing are considered. A number of schemes of improvements are putforward and discussed in the dissertation to eliminate defects and ameliorate thewhole process.In quartz glass deposition, deposition surface temperature distribution is animportant factor affecting the efficiency of sedimentation. The higher is thedeposition surface temperature, the larger the quartz glass cylinder will be. On theother hand, the more uniform is the temperature, the better performance will beobtained. Meanwhile, the flow field and temperature field within the computationaldomain are paid attention to as well. In order to reduce the heat load of wastedischarge pipes, a study on waste discharge parameters is done. On the basis ofexisting production process, optimization by means of altering the parameters ofinlets and outlet has been referred to and a new combustor structure is utilized in theprocess afterwards. Annular combustors of8rings and10rings are studied, andfurther exploration has been conducted as to the influence the parameters of inlets,headlight distance and furnace structure have on the efficiency of deposition with10-ring-annular combustor. Quite a lot of calculation done, a qualitative analysis is given in the dissertationfor the reference of practical producing design.