高温电加热碳化硅合成过程的数值模拟

Simulation of Silicon Carbide Synthesis by High-Temperature Electric Heating

建立电加热碳化硅合成炉的三维模型,利用FLUENT软件对合成炉内气体流动、传热、化学反应过程进行数值模拟,并分析了配合料孔隙率对碳化硅成品的影响。研究表明随着合成时间的延长,炉内热量呈辐射状向外扩散,气体呈现三维多向流动特性,反应进行到24 h时CO气体流量达到最大,随着反应配合料孔隙率的增加合成时间随之缩短,但由于升温过快使得热源周围部位碳化硅分解加剧且炉内压力明显增加。生产时可在炉底加入少许木屑增加透气性以降低炉内压力,同时控制配合料孔隙率在28%~33%之间从而保证成品质量的同时可以防止由于升温过快压力过高所造成的喷炉事故。

The temperature / pressure profiles,heat / gases flow-fields and reactions,in growth of SiC with the proposed vacuum furnace,were modeled,analyzed and simulated with software Fluent. The impact of the porosity of graphite and quartz,on the SiC growth was investigated. The simulated results show that the porosity significantly affects the SiC quality and growth environment. For example,as the porosity increased,the temperature and pressure rapidly increased,accompanied by an increasing risk of spouting accident and deterioration of SiC crystal,though the energy consumption decreased. While the reaction time increased,a SiC tube grew around the heater with complicated phase-structures and defects because of the temperature gradient. High pressure at the bottom,because of rapid generation and poor permeability of the resultant gases,leads to furnace-spouting accident. We suggest that the porosity in 28% ～ 33% range and some sawdust at the bottom improve SiC quality and eliminate furnace spouting.