Recently, the need of renewable energy is significantly increasing by carbon neutral, the demand of silicon wafers is also increasing as a result of growth of the solar energy industry. However, the recycling technology of silicon sludge is needed because a large amount of waste silicon sludge is generated from the silicon wafer manufacturing process. Many researches have been studied to convert the silicon component contained in the silicon sludge to silicon carbide (SiC). SiC powder can be synthesized using silicon sludge by heat treatment with carbon addition. Therefore, the removal process of residual carbon is required because the excess carbon is generally used to maximize the SiC conversion rate. In this work, computational fluid dynamic (CFD) analysis of the removal process of residual carbon has been studied by using the commercial CFD code ANSYS FLUENT.