Fracture Failure Analysis And Prevention Of The Flue Gas Turbine Expander Blade At FCC

Expander is an important installation in petrochemical enterprise catalytic device that used for the recycling of flue gas energy. Its normal operation has a very important influence on safety and efficiency of the catalytic device. This paper analyzed the cause of the blade fracture and put forward the improvement measures to prevent fracture occurrence. This research is of great significance for long period safe operation of devices.Sinopec Shanghai Gaoqiao branch 3#Fcc device expander was put into use in 1998 July and shut down suddenly in April 2013. The unit disassembly inspection found a blade of the expander fractured,it leads to stoping due to severe dynamic unbalance vibration exceeds the standard interlocking shutdown. The fractured blade was analyzed by means of macroscopic examination, physical and chemical inspection, mechanical properties test and fracture and corrosion products, and the stress and fatigue life of moving blades were calculated,so that the reason of the blade fracture was drawed. The corresponding improvement measures are proposed from aspects of improving operating environment and its performance, and achieved good results in practical application. The main conclusions are as follows:The fracture of blade model belongs to fatigue fracture,and the blade surface pits in high stress area is the origin of fatigue crack initiation. High temperature sulfur corrosion and erosion of catalyst particles contribute to the stress concentration of the corrosion pit, and that the long-term operation under high temperature caused grain boundary weakening had played a role in the promotion of blade fracture. Compared to the fractureddomestic blade and imported,lower hardness, poor control of chemical composition of material is relatively strict, the poor mechanical properties at high temperature.All these factors make it easier for domestic blade fracture accident.The catalyst burning to produce high concentration SOx sometimes in regenerator caused low temperature hot corrosion of GH864 alloy blade,and the erosion of more than 5 μm catalyst particles produced in high temperature flue gas, these are the external factor of blade fatigue crack source.In the research on improving measures of prevent sudden fracture of blades, by setting the pre lift section and using new efficient atomization nozzle and other measures to reduce the coke rate,in order to improve the catalytic material of desulfurization and denitrification rate improved the effect of refining Wax oil hdrotreating unit, all these have decreased the content of SOx in fluegas eventually. Impurity content of raw material has been controlled in the operation management, and erosion caused by the catalyst particles has been reduced by strengthening the use of management.Finally the last barrier about the blade guard has been builded by spraying Cr3C2/NiCr ceramet.The effects of improvement measures in practical applications showed that the analysis of causes of fracture on expander vane was correct. The improvement measures were effective and had expected effects.