Based on the actual situation of the site, the preheating furnace is reconstructed according to the defects in the original design and manufacturing. The specific modifications are as follows. (1) The medium in the furnace tube in the convection section is changed from “oxygen-steam” to “steam”; in order to avoid the adverse effects on the furnace tube caused by abnormal working conditions during startup and shutdown, and to ensure the safe and stable operation of the device, the furnace tube in the convection section is operated. The temperature is designed and selected according to the operating condition of 500 ℃, 340H is selected, and the furnace tube of the convection section is overall updated with new materials. (2) The 4 burners of the preheating furnace were replaced, and the combustion-supporting air was changed from the original forced air supply to the mode of interlocking and automatic switching of self-priming and forced induction air; Heater, recover the waste heat of the flue gas of the preheating furnace, increase the temperature of the combustion air, and reduce the consumption of the fuel gas of the preheating furnace. (3) Change the oxygen process, that is, the preheating furnace does not preheat oxygen. The improved system flow is as follows: after the steam is preheated in the convection section of the preheating furnace, it is mixed with oxygen at the entrance of the reformer burner and then enters the reformer. (4) Since the leakage of the boiler water heat exchange tube in the convection section is difficult to repair, the preheating furnace short-circuits the boiler feed water pipe from outside the furnace, and blocks the boiler feed water inlet and outlet headers. In this transformation, the boiler feed water heating section of the original preheating furnace convection section was cancelled. (5) In order to increase the safety factor of the preheating furnace operation, the burner is equipped with a permanent light, which eliminates the potential safety hazard that the fuel gas will accumulate in the furnace chamber and mix with air to form explosive gas after the instantaneous flameout in the furnace chamber.