Study On Heat Transfer Process Of Cylindrical Furnace

Furnace is an important equipment in petroleum and petrochemical plant.Its heat transfer performance will significantly affect the operation efficiency and equipment safety.Among the furnace,stand-pipe cylinder furnace is widely used in petrochemical plant.Its furnace tubes are vertical arranged in radiation chamber,and the burner is located at the bottom of radiation chamber.When the heat load of the furnace is too high,it is easily to result in uneven distribution of axial heat intensity of the furnace tubes and cause local overheating of furnace tubes,which may cause deformation or even rupture of furnace tube,and affect the operation safety and stability of the device.In order to optimize the distribution of the thermal intensity of a cylindrical furnace,a numerical simulation method was used to study the scheme of double grate furnace tube with radiant outlet and central reflecting wall,the the scheme of central furnace wall is verified by thermal test.The numerical simulation results show that the average heat intensity of the double-row tube scheme is 31.27 k W·m^-2.Along the height of furnace,the heat intensity of the tube first increases and then decreases.The maximum heat intensity of the inlet pipe is 87.42 k W·m^-2,and the peak value is between 4 and 6 m.The variation of oil film temperature is consistent with that of heat intensity of furnace tube.The maximum oil film temperature of outlet tube is405?.Increasing the number of radiation tubes in the inner row can not only significantly reduce the average heat intensity of the furnace tubes,but also at the same time reduce the peak heat intensity,and improve the uneven distribution of the heat intensity of the furnace tube in the height direction.The effect of adding reflective wall in the center of radiation chamber was simulated and studied.The results show that the average heat intensity of the tube of the reflecting wall blocking scheme is 17.64 k W·m^-2,and that of the tube of the reflective wall opening scheme is18.69 k W·m^-2,which is close to that of the conventional cylinder furnace.The maximum thermal intensity of the intake tube of the cylindrical furnace with reflective wall blocking hole is 47.06 k W·m^-2,and the distribution of the heat intensity of the tube is not uniform.The opening of the reflective wall can effectively improve the non-uniform distribution of the heat intensity of the tube,the peak thermal intensity of the inlet tubes decrease to 37.28 k W·m^-2.The maximum oil film temperature of the inlet tube of the cylindrical furnace with reflecting wall is about 5-10?lower than that of the conventional cylindrical furnace,and the maximum oil film temperature of the outlet tubes are close to that of the conventional cylindrical furnace.The effect of reflecting wall on heat transfer and NO_x content in flue gas was investigated by thermal test.The results show that the flame height increases behind reflecting wall,the heat absorption in radiation chamber and the average heat intensity of radiation furnace tube decrease slightly,but the NO_x content in flue gas increases.