Numerical Simulation For High Purity Large Silica Glass Deposition Process

The industrial technology of quartz glass production includes fused process, Gasrefining process, synthetic quartz glass techniques, high frequency plasma flame fusionprocess. And the synthetic quartz glass techniques include chemical vapor deposition(CVD) process, vapor axial deposition (VAD) process, and plasma chemical vapordeposition (PCVD). Compared with other techniques, CVD process has a largeadvantage in the production of large-size high-purity quartz glass.To improve the homogeneity of the high purity large size silica glass produced byChemical Vapor Deposition (CVD) method, the Fluent commercial software was usedto simulate the temperature field and flow field in the deposition boiler. The originalmodel used was modified further more. To be specific, the arrangement form of theburner was adjusted and the rotation of the silica glass sedimentary body was takinginto account. A lot details in of the boiler’s structure were modified, such as, betweenthe roof and the burner there was asuumed to be a narrow gap, the bottom was notsealed and the hight of the exhaust port was rearranged. On this basis, the influence ofthe gas velocity in every gas channel of the burner on the sedimentary body’stemperature distribution were investigated. And moreover, three schemes were putforward in which the gas velocity of every channel adjust wes adjusted. The resultswere shown as follows.The deviation of the burner can lead the low-temperature zone away from the roofof the sedimentary body. So the reletive low temperature zone in the roof before can beminimized or removed eventually. On one hand the deviation of the sedimentary bodycan improved the flow field arround, on the other hand it can enhance the heat transferbetweent the sedimentary body and the high temperature fluid, which can increase thetemperature of the sedimentary body. Also, the temperature distribution can be moreeven.Through changing the gas velocity of each gas channel, the influence of eachchannel on the temperature distribution, the flow field and temperature field wasobtained. On this basis, the prioritization scheme of the burner was proposed. Thereaction process of the SiCl4, hydrogen and oxygen was deeper understood according tothe analysis of the concentration distribution of some components in the reactor. Threeprioritization schemes in which the velocity of each channel was adjusted wereproposed. In Case1, the hydrogen and oxygen is in a proper stoichiometric ratio. Case2and case3are hydrogen enrichment, which means the velocity in the middle isrelatively larger, and oxygen enrichment, which means the velocity around is relativelylarger, respectively. Through varying the offset distance of the burner, the revolving speed of thesedimentary body, the distance from the burner to the sedimentary body, the narrow gapbetween the burner and the roof, the size of the opening at the bottom of the reactor andthe position of the exhaust port, a lot of simulations were taken and the results werediscussed throughly.