Numerical study on the heat recovery and cooling effect by built-in pipes in a graphitization furnace

Abstract As one of the basic equipments in carbon industrial manufacturing, a graphitization furnace usually heats raw materials to over 2800 °C, and consumes a large amount of energy. After the heating and thermal insulation period, it usually takes 8–10 days to cool down naturally and the thermal energy in it is not utilized at all. In order to decrease the cooling period and recover the heat in the graphitization furnace, cooling pipes are arranged in the insulation layer of the furnace and the circulated gas is ventilated in the pipes to protect the pipes against high temperatures in the heating period and to recover energy in the cooling period. A numerical model of the conjugated heat transfer in both the furnace and the pipes has been built and verified, and is used to simulate the heating, insulation and cooling period of the improved furnace and the primary one. By comparative analysis, the control strategy and operating performance of the improved furnace are obtained, and indicate that 30.6% of the heating energy can be recovered and nearly half of the cooling period is reduced, while the heat recovery has no negative effects on the original production process. Thus the proposed method benefits both the productivity of graphitization manufacturing and the energy-saving of the graphitization furnace, and may have great application potential in graphitization furnaces.