Simulation Of Hot Wax Removal At Typical Locations Of Pipeline Cross Section Based On Lattice Boltzmann Method

Most of China’s crude oil is’three high’crude oil with high pour point,high viscosity and high wax content.In the process of gathering and transporting crude oil,with the loss of heat,the temperature of crude oil will drop below the wax precipitation point,and the paraffin in crude oil will continue to accumulate and attach to the inner wall of the pipeline.The hot washing effect of hot washing water on the wax layer at each position on the inner wall of the pipeline is not the same.In order to investigate the effect of dimensionless factors on heat transfer process of hot washing and wax removal at each typical position of the pipeline,and to adjust the wax removal time at the corresponding position,based on the lattice Boltzmann method,the paper programmed and simulated the phase change heat transfer law of the paraffin layer at each typical position of the pipeline.The sensitivity analysis and sorting of the factors affecting the effect of hot washing and wax removal at each position of the pipeline are carried out by orthogonal experimental method,and the guiding suggestions for engineering practice are given.The main work and conclusions are as follows:(1)The physical model and mathematical model of the phase change heat transfer process of hot washing wax removal at each typical position of the pipeline under the third boundary condition are established.The mathematical model of hot washing wax removal is solved by using the double distribution enthalpy function model based on the lattice Boltzmann method.The density distribution function is used to describe the velocity field of the wax layer melting process,and the temperature distribution function is used to describe the temperature field of the wax layer melting process.(2)The phase change region of wax layer is regarded as multiphase flow region.The paraffin melting process at the side of the pipeline was selected.The visualization experiment of paraffin phase transition in a square cavity was carried out,and the accuracy of the lattice double distribution enthalpy Boltzmann model was verified.(3)The lattice Boltzmann method is used to simulate the hot wax removal process at different typical locations of the pipeline under different Ra,Pr and Ste numbers.The simulation analysis shows that when Ra increases from 1.0×10~4to 1.0×10~6,the wax removal time at the top of the pipe is shortened by 88.09%,the wax removal time at the side of the pipe is shortened by 29.71%,and the wax removal time at the bottom of the pipe does not change.Therefore,the Ra number has the greatest influence on the wax removal rate at the top of the pipeline.The wax removal time at the top of the pipe is shortened by 26.08%,the wax removal time at the side of the pipe is shortened by 25.31%,and the wax removal time at the bottom of the pipe is shortened by 25%when the Pr number is reduced from 67.5 to 47.5.Reducing the Pr number helps to improve the wax removal efficiency at the top,side and bottom of the pipeline.The wax removal time at the top of the pipeline is shortened by57.14%,the wax removal time at the side of the pipeline is shortened by 65.17%,and the side of the pipeline is cleaned when the Ste number increases from 0.805 to 10.(4)Orthogonal experimental design was carried out for the hot washing and wax removal process at each typical position of the pipeline,and sensitivity analysis was carried out.The influence weight of each factor is evaluated by range and variance analysis,and then the practical guidance suggestions are given.It can be seen that when the paraffin layer at the top of the pipeline is hot washed,the weight of each factor is ranked as Ra>Ste>Pr.The influence weight of each factor is ranked as Ste>Ra>Pr when the paraffin layer at the side of the pipeline is hot washed.The influence weight of each factor is ranked as Ste>Pr>Ra when the paraffin layer at the bottom of the pipeline is hot washed.In practical engineering,the wax removal rate can be improved by increasing the temperature of hot washing water or reducing the kinematic viscosity of paraffin by chemical method.