结蜡厚度对输油成本的影响

含蜡原油管道 ,尤其是北方的含蜡原油管道 ,普遍存在结蜡现象 ,必须及时进行清蜡才能实现管道的经济运行。当输量高于或等于设计输量时 ,保证完成输送任务是生产中优先考虑的问题 ,因此清蜡后的残余蜡层应尽可能小。当输量低于设计输量时 ,管道运行的经济性上升为主要问题 ,清蜡后的残余蜡层是否还应尽可能小值得研究。在输量一定的情况下 ,随着结蜡层的增厚 ,管道的总传热系数减小 ,热力费用下降 ;同时 ,管道的有效内径减小 ,摩阻变大 ,动力费用增加。为此 ,建立了以输油成本为目标函数 ,以结蜡厚度为决策变量的数学模型 ,从结蜡厚度的角度研究管道的经济运行。采用黄金分割法对模型进行了求解。结果表明 ,对于给定输量 ,存在一个结蜡厚度 ,使得输油成本最小 ;当输量低于设计输量时 ,允许存在一定量结蜡厚度在经济上是合理的

The Effect of Wax Deposition Thickness on Oil Transportation Cost

For waxy oil pipelines, especially for the northern ones, wax deposition is a common phenomenon. To make the pipeline operation economic, the wax must be removed in time. When the flow rate is not less than the designed flow rate, assuring the transportation amount is the problem to be considered first, thus the remained wax thickness shall be as small as possible after wax scraping. When the flow rate is less than the designed one, to operate the pipeline economically becomes one of key problems, and whether remained wax thickness shall still be as small as possible is worth studying. Under the circumstance that the flow rate is a constant, with wax deposition growing thick, the total heat transfer coefficient of the pipeline decreases, and heating power cost reduces; at the same time, the effective inner diameter of the pipeline becomes smaller, so the friction loss and power cost increase. A mathematical model was established, in which oil transportation cost was taken as object function and wax deposition thickness was taken as decision variable. This model was resolved by golden section method. The results show that for a given flow rate, there is a certain wax deposition thickness whose oil transportation cost is minimal, and that when the flow rate is less than the designed one, allowing of a certain amount of wax deposition on pipe wall is economic.