The Research On Operationg And Shutdown And Restart-up Of Buried Waxy Crude Oil Pipeline

For safety of oil pipeline, The work focuses on Operationg and Shutdown and Restart-up of Buried Waxy Crude Oil Pipeline. The Operating math model is built according waxy crude oil characteristic,solidification will preferentially occur on the wall,leading to deposition.This causes undesirable effects,such as an decrease in pipe diameter and an increase in pressure losses. According to deposition mechanisms, This work take into account deposit thickness ,The temperature of thin boundary layer near the wall and the bulk is given; The control equation of crude oil in the Buried Waxy Crude Oil Pipeline during the process of shutdown was established And the approach to calculate the equation by finite element method was given and the max safe shutdown time was calculated;The coupled model of restart-up of waxy crude oil pipeline is studied about continuity equation,motion equation and theology equation. The restart model takes into account the compressibility and longitudinal variations. The theology of the gelled oil is modeled based on Bingham model, yield stress varies with time. Both laminar and turbulent flows are considered in the model According to the result of numerical simulation,analysed the effects of flow rate,pipe size,pipeline length,burial depth,insulation thickness,start date,inlet temperature,preheat time,ground conductivity on operating process; analysed the effects of shutdown date,shutdown length on shutdown process; analysed the effects of start-up pressure,initial compression time,liquid hold-up,compressibity,initial compression time on mass flow rate,pressure,time to clear the gelled oil.