Research On Safe And Economic Optimized Operation Technology For Oil Pipelines In Cold Areas

The optimization of production and operation schemes is an important step towards energy saving and emission reduction in oil pipelines.The current oil pipeline optimization model is mainly based on the objective function of minimising energy consumption or production costs,with temperature and pressure as constraints to optimize the opening programme and operating parameters of the heating furnace and oil transfer pumps.Under stable pipeline operating conditions,the model can play a good role in energy saving and consumption reduction.When abnormal operating conditions such as leaks require a shutdown,the original production and operation optimization model has difficulty in ensuring an effective and safe shutdown time,which can easily lead to malicious accidents caused by freezing and blocking.In response to this situation,a pipeline in a cold region was used as an example to carry out research on the safe and economic optimization of oil pipeline operation,with the following main results:Firstly,the density,freezing point,specific heat capacity,viscosity-temperature curve,wax precipitation point and yield stress of the oil transported by the pipeline were tested and analysed,and the model for calculating the total thermal heat transfer coefficient and the hydraulic friction coefficient of the oil transmission pipeline was established by applying the most optimal fitting technique.Secondly,with the opening scheme of the heating furnace and oil transfer pump,the heating temperature of the heating furnace and the head of the oil transfer pump as variables and the lowest total energy consumption cost of production operation as the objective function,a dynamic optimization model for the production and operation process scheme of the oil transfer pipeline is established and transformed into a series of static optimization models using numerical methods,which are efficiently solved using an improved sparrow search algorithm.The model was used to optimize the plant start-up scenarios for each month of the year at the pipeline’s 15,000t/d and 21,000t/d capacity,and the optimized average operating costs were reduced by 52.2% and 18.2% respectively compared to the actual operating scenarios.Again,the pipeline stopping and restarting calculation model is established to give the calculation method of the minimum starting transmission volume and safe stopping time of the pipeline,and to determine the change of pipeline stopping temperature and the influence on the safe stopping time under different seasons,different transmission temperatures and different transmission volumes of the pipeline.On this basis,the pipeline needs to be repaired due to leakage and other problems,and on the basis of the original production and operation plan optimization model,the pipeline safety stopping time is greater than the pipeline repair time constraints,forming a safe and economic operation optimization model for oil pipelines.The optimization results of typical working conditions under four seasons,spring,summer,autumn and winter,show that the safety and economic optimization model,compared with the traditional optimization model,increased the energy cost of production and operation by77.2%,19.4%,5.6% and 70.4% respectively,and extended the safety stoppage time by 70%,15%,26.7% and 96% respectively,contributing to the safe maintenance and repair of the pipeline.Finally,a software engineering approach is used to develop an "auxiliary decisionmaking system for the optimization of oil pipeline operation".The software system contains modules for basic data management,pipeline process characteristics,equipment process characteristics,energy-consuming equipment efficiency calculation,process simulation and optimization of operation,which can realize the functions of simulation calculation and optimization of safe and economic operation of oil pipelines.