Research On Stress Analysis Of Cracked Gas Dryer

Ethylene productivity is an important indicator of weighing national petroleum and chemical industry level of development. Whereas, the research and develepment on large-scale core equipment restricts the large scale of the ethylene unit. The extra large type cracked gas dryer which this article studies is one of the megaton-class ethylene unit core equipments. The working environment is complex and bad, which sets a higher request on the structure and intensity security of the cracked gas dryer.By the analysis of design method on the extra large type cracked gas dryer which has a series of design parameter as follows:the diameter of the cylindrical shell is 5200mm,the height of the cracked gas dryer is 18830mm,working temperature is 16℃～232℃, working pressure is 0.76MPa-4.5MPa.Caculated by method of the Design by Analysis, it gets a safety and economic shell size, the thickness of the shell cylinder is 80mm, and the thickness of the head is 50mm.Based on the finite element method to the analysis and calculation of the cracked gas dryer, it researches the openings on the upper and lower head, the manhole, flat cover, pipeline interface and others which with higher stress concentration, it determines the finite element research model and mesh mode, analyzes and sets the boundary conditions. Calculation results show that the openings on the upper head with a larger stress, maximum stress occurring at the openings of the cylindrical shell, openings on the lower head and the flange are also with a larger stress. It has carried on the linearized processing to the finite element calculation results of these dangerous parts, made strength assessment, and finally checked the fatigue strength of these parts.To the skirt part of the dryer which the structural changes and stress distribution are the most complex, it carries on the mechanical stress analysis and fatigue analysis by the finite element method. Complete the thermal stress analysis to the skirt of the dryer by the finite element method, it researches the relations between the hot-box height and thermal stress, then it is found that a high degree affects between the height of the skirt and the thermal stress lies on the skirt. The analysis result revealed that the thermal stress gradually decrease with the hot-box height from 200mm, while the thermal stress gradually increase with the hot-box height from 380mm. Finally it determines a reasonable hot-box height according to the analysis result. It uses the finite element software to the simulation calculate on the complex working conditions of the cracked gas dryer, then gets the combination stress analysis result in the condition that both pressure load and thermal load apply on the dryer. It calculates the equipment construction stress distribution in extreme conditions that the temperature is 232℃, and the pressure is 3.9MPa,then finds that owing to superposition of the stress produced by pressure load and thermal load, it causes the equipment structure local stress to increase obviously then affects the equipment structure security. In order to guarantee the equipment structure security, it sets request to the production operations of the cracked gas through calculation the stress distribution of the dryer in the actual working conditions.