Research On Thickness Reduction Of Delayed Coking Unit And Numerical Simulation Of Mechanical Erosion

As delayed coking unit operates for many years in high temperature-high pressure and corrosive environments, it’s equipments are generally affected by corrosion, which causes thickness reduction and perforation phenomenon. The condition is even getting worse when the crude oil becoming heavier and poorer. Mean while,in some parts of the unit, erosion-corrosion by high-speed fluid accelerates the thinning of equipments. Thickness reduction caused by erosion-corrosion is so unpredictable that it becomes a significant cause of accidents.To study the reason of thinning phenomenon, we did an overall research on corrosion and erosion-corrosion in delayed coking unit,mainly through data processing and theoretical analysis. In this way,safeguards are taken and improvements are offered based on the mechanism of corrosion and erosion-corrosion.Mechanical-erosion is an effect factor of erosion-corrosion. To study the effect of erosion-corrosion on thinning phenomenon in coke drum’s pipeline, a discrete particle model of gas-solid two-phase is developed and numerical simulations of the steam cooling stage are carried out by CFD soft. Transient analyses indicate that branch pipe is the most seriously affected by mechanical-erosion with time, which conforms to the actual conditions. This indicates that erosion-corrosion intensity increases by increase of mechanical-erosion intensity, which must have an affect on thickness reduction and perforation phenomenon. Then an optimized structure of oil vapor pipelines is proposed by decreasing the intensity of mechanical-erosion.This simulation showed it is reliable and possible to predict the areas affected seriously by erosion-corrosion in delayed coking unit by means of numerical simulation. Combining numerical simulation and positioned thickness measurement is an effective approach to reduce accidents.