Study On The Factors Affecting Long-running Of FCC Unit And Measures

Fluidized catalytic cracking(FCC)is the most important secondary processing in-refineries.A long-term running of FCC plant is of great significance to the full-scale process and reduction of energy consumptions for the refinery.This work analyzed the factors that affect the long-term operation of the No.2 FCC units of Jinzhou Petrochemical Plant and proposed solutions based on the work experience in PetroChina and Sinopec catalytic cracking units.1.This paper analyzed the reasons of coking occurred on No.2 FCC units of Jinzhou Petrochemical Plant,and proposed corresponding solutions.The mechanism of coking occurred on the top of the atomizing nozzles,settlers,oil and gas pipelines,etc.were studied in detail,based on which the coking had been solved by optimizing the operating conditions of process,upgrading key equipment,and using coke-proof steam reforming.Hence,no unplanned shutdown of plant caused by coking has occurred during three operation cycles.2.Considering that the scale formation leads to the hood vibration,the long-term operation of the hood had been achieved by decreasing the concentration of catalyst fines in the flue gas.The analysis showed that the scale formation on the hood are mainly caused by the deposition of catalyst fines.The ways that can reduce the concentration of catalyst fines in the flue gas,e.g.,renovating the regenerator,effectively inhibited the scale formation on the hood and ensured the long-term operation of the hood.3.The main reason for the leakage of the external heat extractor tube bundle was found by analyzing the process and structure of external heat extractor.The problem was solved by upgrading the thermal system,remodeling the structure of the external heating system,and optimizing the operating conditions,which makes no leakage of the external heat extractor occurring over the past six years.The fatigue life of the device's external heat extractor,which obtained by finite element analysis performed by ANSYS software yields provided a basis for predictive maintenance.4.A high solids content of the slurry will accelerate the wear of the slurry system and directly threaten the safety of the device.Operating conditions of cyclones that are used for separation of oil and gas and catalyst directly affect the solids content of the slurry.Calculations showed that the unconventionality of cyclone operating conditions can cause the reduction of separation efficiency between oil gas and catalyst,leading to the increase of solid content of oil slurry and the wear owing to the catalyst directly,which finally affects the long-period operation of the oil slurry system.The optimized cyclone operation conditions and the thickness measurement periodically achieve pre-inspection maintenance,which reduces the possibility of unplanned shutdown of the device due to leakage of the oil slurry system and provides guarantee for the long-term operation.