(1) Design technical data errors. In the design of the preheating furnace, in the process flow and equipment list, it is clear that the medium in the furnace tube of the convection section of the preheating furnace is "oxygen-steam". The medium in the section furnace tube is "steam", the process drawing of the preheating furnace does not match the content of the medium in the equipment drawing, and the technical data of the preheating furnace equipment is wrong. (2) The use level of equipment materials is low. According to the inspection results, one of the three "oxygen-steam" pipes in the preheating furnace has leaks in many places. After analysis, it is found that the material used for the "oxygen-steam" coil is 304. Compared with OCr18Ni10Ti and 316, 310 and other materials, the tendency of intergranular corrosion is stronger at temperatures above 425 ℃, and 600 to 700 ℃ belongs to the intergranular corrosion of 304. In the area, the corrosion rate Z is fast, and steam + oxygen belongs to the state of wet oxygen, which can damage the Cr2O3 anti-oxidation film at high temperature and has a strong oxidizing effect on 304. After communicating with many design units, it is confirmed that 304 material is not suitable for long-term use in high temperature and high oxygen environment, that is, for the operating conditions of the preheating furnace, the material selection level of the "oxygen-steam" coil is low, which cannot meet the requirements for use. Require. (3) The equipment structure design is unreasonable. The preheating furnace is a vertical cylindrical tube furnace, all of which are designed with a coil structure. From the perspective of operation, its thermal efficiency is not high, only 75%, and the furnace tube must be inspected and overhauled when it breaks down. The furnace is disassembled, the repairability is poor, and the maintenance is very difficult.