CFD simulations on the gas profile in the tubular furnace were performed using a COMSOL MultiphysicsⓇ6.1 package. The model geometry was created in the software as shown in Figure . O2 was selected as the fluid material. A laminar flow study was applied to the model, with a gas inlet and outlet specified on the left and right ends of the reactor. Other domains of the model were all defined as wall boundaries. The boundary condition for the inlet was set as a fully developed flow with a flow rate of 2 l min -1 , and that for the outlet was set as a static pressure of 0 Pa. The results were analyzed by COMSOL.