Study On Contamination In Batch Transportation Of Crude Oil And Product Oil By Numerical Simulation

A large amount of contamination generates in the interface in the batch transportation of different types of oil,resulting in economic losses.However,the mixing process of adjacent oil products is very complex and affected by many factors,such as physical properties of oil products,transportation sequence,flow rate,topography and pipeline parameters.At present,the scheme of batch transportation of crude oil and refined oil has been actively investigated with the decrease of the production of crude oil and refined oil in Xinjiang province,and the related technical support is urgently needed.Therefore,the numerical simulation is conducted to study the mixing characteristics of different oil products in this paper.The first problem in the numerical simulation of contamination is the large amount of calculation for the long-distance pipeline.Therefore,the simulation efficiency is improved from two aspects: the solver and the computation domain.Firstly,based on the two-dimensional convection-diffusion model of contamination concentration,a more efficient solver of preconditioned conjugate gradient method is selected by comparing the efficiency among Gauss-Seidel iteration method,multi-grid method and preconditioned conjugate gradient method.Then the contamination domain is tracked by dynamic mesh in the simulation process,and the concentration distribution of the contamination domain rather than pure oil domain is calculated.As a result,the scale of the computation domain is greatly reduced and the simulation efficiency is greatly enhanced.Moreover,the scale of computation domain only depends on the length of the contamination domain and is not affected by the total length of the pipeline.In addition,these efficient simulation strategies are applied to one-dimensional contamination simulation under normal and transient conditions,and the simulation efficiency is greatly improved as well.The ground temperature along the exported pipeline from Xinjiang province varies greatly,leading to the severe change of oil temperature,oil viscosity and the development of contamination.The heat transfer between the oil and the surrounding soil during the flow process must be considered.Therefore,the contamination model coupled with temperature field between the soil and the oil is established to carry out the numerical simulation of contamination in long-distance batch transportation of crude oil and refined oil.In addition,the idea of micro-element method is used to achieve the efficient calculation of the soil temperature field in the long-distance pipeline by taking a computation cross-section at an interval of 1km.Based on the above contamination computation model and efficient solution methods,the development of contamination in batch transportation of crude oil and refined oil in different seasons(oil temperature and soil temperature are different)is studied.The results show that the amount of contamination is less in summer due to the higher temperature of oil and soil.While the temperatures of oil and soil are lower in winter,which leads to great increase of contamination.Therefore,the transportation scheme of local heating the head and tail domain of oil is proposed to reduce contamination in winter.The development law of contamination is studied by controlling the heating length and temperature of the head and tail domain of each batch.The safe,economical and reasonable transportation scheme is optimized.Finally,the study in this paper could provide references for the batch transportation of crude oil and refined oil in the pipelines from Xinjiang province.