Key Technologies And Quality Controls For The Field-Assembly Of A Large-Sized Gasifier

Gasifier is a key equipment in 500kt/y synthetic ammonia production system. The field-assembly of the gasifier, as a challenge task, involves many practical and technological difficulties. The purpose of the thesis is to investigate and establish efficient technological measures and quality-control procedures, so that the task can be completed with high qualities.In the thesis, the structural specialties of the gasifier were introduced first. Then strength check for the shell was conducted. The whole gasifier was divided into 20 sections in the plant and delivered to the site separately due to overweight, overlength and overwidth, where the individual sections need to be welded together one by one. The paper analyzed and stated some technical difficulties encountered in the beginning preparation, such as designing of the assembly field, configuring of the assembly machinery, and other problems confronted in assembling and erecting equipment, for example, the operation of the quality control system, erection, fitting-up, welding, heat treatment, NDT and hydro-test.Considering these problems and difficulties, and the special requirement of fabricating that the gasifier shell must be adhered to, the thesis put forward its own reasonable and feasible processes and technical plans individually, and also clarified quality control measures of fitting-up, welding, heat treatment, NDT, hydro-test of shell rings. These technical measures and control procedures ensure the good quality of each important procedure and the whole quality of the site assembly of the gasifier. Especially the preheating and post heating methods used in heat treatment, and the self-design LPG compulsive vaporized plan were successfully applied to solve reverse liquefaction after LPG compulsive vaporization. This guarantees job requirement of preheating and post heating in welding and lays a solid foundation for equipment quality. And this not only proposes a feasible solution to the preheating and post heating in large-scale equipment's site assembly and welding, but also guides well for solving technical problems in the plant, such as preheating and post heating. Designing of the assembly field, lectotype and disposition of the assembly machinery and local post welding heat treatment plan proposed in the thesis completely meet the technical requirements of erection, welding, heat treatment process, and therefore can be used as the reference for the site assembly, welding, and local post welding heat treatment of the similar large-scale equipment.