| The atmospheric distillation unit acting as the leading facility has a great impact on the safe and stable operation of the subsequent process in the petroleum refining industry.The corrosion failure accident of the atmospheric distillation unit caused by the intrinsic inferiority of the crude oil is detrimental to the economical benefit and life safety of corresponding operating personnel.Corrosion mechanisms of ammonium salt under-deposited corrosion and dew point corrosion have been studied at the low temperature status of the atmospheric tower.However,the interface between the two types of corrosion remains unclear.The transformation process lacks corresponding research and analysis.Single corrosion prevention and control are difficult to tackle with the corrosion of multi-components.Therefore,in this work,several studies were conducted to theoretically support corrosion control of the top of atmospheric tower.The atmospheric tower of a petrochemical enterprise is used as the research object,and the gas-liquid balance equation is used to simulate the process flow of the atmospheric tower from the raw material end as the cut-in stage,using the thermodynamic BK10 model and the Peng-Robinson cubic equation of state.The ammonium salt crystallization temperature model and crystallization rate model model of the atmospheric tower with the corrosive medium H2S,HCl and NH3 partial pressure as the main body are established.The conversion interval of ammonium salt-dew point corrosion characteristics is predicted by the established ammonium salt particle flow model and Euler wall film model(EWF).The main research content and conclusions of this article are as follows:(1)The gas-liquid balance equation is used to simulate the process flow of the atmospheric tower from the raw material end as the cut-in stage,which specifies that the ammonium salt crystallization temperature and the dew point temperature is 188? and 97.8? respectively.The overlapping area of the salt crystallization interval and the dew point interval is the area above the top of the tower.(2)The complex conversion mechanism of ammonium salt-dew point is studied,and the corrosion conversion process is explained,using ammonium salt crystallization,dew point temperature,and spatial distribution analysis.It is demonstrated that the parameters of temperature,raw material loading,the amount of corrosion medium,the content of stripping water,and so on will affect the ammonium salt-dew point conversion,revealing the ammonium salt-dew point corrosion mechanism.(3)Based on the multi-component system in the atmospheric tower,the multi-phase flow model and the Euler wall film model(EWF)are used to analyze the fluid dynamics in the prediction interval of the ammonium salt-dew point conversion to determine the oil,gas,and water.The partial reduction of the gas-phase water volume fraction dominated the ammonium salt-dew-point corrosion conversion zone in the component fluid system.It is expected that high-risk areas will exist where ammonium salt particles will remain for a long time and the volume fraction of gas phase water will be limited.The innovations of this paper are as follows:(1)Based on the multi-phase fluid composition model,the transformation connection point between ammonium salt corrosion and dew point corrosion is established from the temperature level and corrosion characteristic parameter group,and the influence of atmospheric tower ammonium salt-dew point corrosion conversion is analyzed;(2)Based on the multi-component gas-liquid two-phase equilibrium model in the atmospheric tower,a model for the crystallization rate of gas-phase multi-component ammonium salt in the atmospheric tower is constructed,and the ammonium salt-dew point corrosion conversion interval is predicted. |
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