Study On Erosion-Corrosion Of Multiphase Flow In Hydrogenation Air Cooler

With the development of the world petrochemical industry,the processing scale of high sulfur,high nitrogen and high chlorine crude oil continues to increase,which puts forward higher requirements for chemical production process and equipment.The development of hydrogenation technology has solved this problem well,but at the same time,corrosive media such as hydrogen sulfide,hydrogen chloride and ammonia generated by the reaction of hydrogen with sulfur,chlorine,nitrogen and other impurities in the oil have caused serious corrosion to the hydrogenation unit,making the in-service time of the unit much lower than the design life,bringing serious economic losses and safety problems.Air cooler is an important heat exchange equipment in the hydrogenation process,but it often leaks due to erosion corrosion.In this paper,a physical model is established for the air cooler with corrosion leakage at the top of the fractionator in a petrochemical plant,and the multiphase flow numerical simulation is carried out by FLUENT software.The multiphase flow structure and its erosion corrosion problem are studied.The results show that there is a complex multiphase flow structure in the air cooler tube bundle and its distribution is significantly different.The complex flow field structure is mainly reflected in the uneven distribution of the fluid in the tube bundle and the large impact angle between the fluid and the wall surface.The velocity is distributed in a ’ double W ’ shape,and the impact angle is within the maximum erosion corrosion range.These lead to a significant uneven distribution of the condensation phase transition process,and also cause the boundary layer separation of the tube bundle with a large radial velocity at the inlet,forming a variety of vortex structures.A variety of factors work together to cause erosion corrosion leakage of the tube bundle.The maximum wall shear force of the leaked No.15 pipe is 46.5 Pa,and the maximum erosion corrosion rate is 3.88 mm / y.The electrochemical corrosion rate can be ignored,and the total erosion corrosion rate is basically consistent with the actual corrosion rate of the factory.On this basis,the air cooler model was improved,and the fluid redistributor was arranged in the tube box.The maximum wall shear force was 17.0 Pa and the maximum erosion corrosion rate was 0.00199 mm / y,which significantly improved the erosion corrosion resistance of the air cooler.