Numerical Simulation Of Radiation Heat Transfer In Modified Siemens Process

The modified Siemens process is the main technology in manufacturing polysilicon. The chemical vapor deposition (CVD) of the trichlorosilane and hydrogen is not only the key process of the modified Siemens process but also the main energy consumption section, which usually consumes more than60%of the total energy consumption. In order to reduce the energy consumption and save the production cost, hydrogen reduction process of SiHCl3has become the subject of intense attention. Especially in recent years, with the rapid expansion in world production capacity and the change of international and domestic situation, the price of polysilicon has fallen below the cost of production. Under the current economic crisis’s situation, every proposal for reducing energy consumption and saving production cost becomes the urgent needs of polysilicon enterprise. Therefore, the object of this paper is to investigate the heat transfer in the Siemens reactor, and alternatives are presented regarding the reduction of the radiant energy loss during the polysilicon deposition, which will provide the theoretical guidance for saving energy of polysilicon scale production.The computer numerical simulation technology was widely adopted to solve the problem in engineering, which could easily simulate conditions that hard to take experiment. The simulation of heat transfer in the silicon deposition process has been investigated by ANSYS FLUENT software in the paper, in which the standard k-ε turbulence model, Discrete Ordinates (DO) radiation model were considered.The flow field and temperature field of24rods and48rods CVD reactor were obtained from the numerical simulation. Based on CVD reactor radiation model, an analysis is presented, which studies the radiation exchange between the hot polysilicon rods and the reactor wall of24rods CVD furnace in detail, especially the power radiated by the characteristic rod of every ring to the wall and influence of the wall emissivity. The results show that the radiation heat exchange is the main power consumed in the CVD reactor. The power radiated by the characteristic rod of outer ring is larger than that of inner ring, which increases with the diameter of silicon rod. However, the power radiated by the characteristic rod of inner ring increased to the maximum and then decreased with the diameter, the reason can be explained by the block effect of outer ring rods.The emissivity of reactor wall has a great effect on the power radiated by silicon rods in the deposition process, when the emissivity increased, the power reflected by the wall decreased, and thereby need to supply the electrode with more energy. Meanwhile, the variation of the energy radiated by silicon rods for four configurations(24,36,48, and60rods) under various conditions of different diameter and wall emissivity are presented. Based on the analysis, it is concluded that the large reactor, such as (48rods and60rods) has obvious advantages in view of energy saving.At last, considering the average growth rate of10μm/min, and combined the heat flux at the surface of silicon rods in the reactor of24rods and48rods, the unit energy comsumption for different wall emissivity are calculated, the results shows, when the wall emissivity is0.3,0.5and0.7, the unit energy comsumption of24rods reactor is68,82and91kWh/kg respectively, what is60,72and80kWh/kg respectively of48rods reactor。...