Research On Technology Of The Batching Transportation Of Cold And Hot Crude Oils

With the rapid development of China's national economy, domestic oil demand continuesto grow rapidly in China in contradiction with them are less energy per capita, more coal andless oil and gas and high-quality energy shortage in the developing country. China has beenchanged from an oil exporting country to a net importing oil country since 1993, oil resourcesdependence on foreign supplies increasing. There is a considerable difference in the naturebetween the most domestic crude oil and imported. Imports of crude oil generally have goodmobility and can be transported at room temperature, the pipeline operating temperature closeto the ground temperature along the pipeline. High-viscous and congealable crude oilproduced in most domestic crude oil, usually using heat transfer process and the pipes haverelatively high operating temperatures. Therefore, domestic crude oil and imported crude oiltransportation is an order of hot and cold in the process of alternative transportation, willbring a series of problems, such as alternate fields of temperature, mixed oil, pipe fatigue lifeand other issues. In order to achieve the safe operation for hot and cold oil transportation inpipelines, it is necessary to conduct special studies of these issues. In this paper, the order ofpipes for hot and cold temperature fields of crude oil, heating scheme selection, stress analysis,and mixed oil analysis and calculation are detailed study. In order to achieve the hot and coldbatch transportation at safe operation of pipelines provides a foundation and help.Under certain assumptions established hot and cold batch transportation mathematicalmodel of temperature field and finite element Method and difference method for solving themathematical model. By calculating the temperature field obtained the results of the law ofthe temperature field for hot and cold batch transportation oil pipeline: A Tube oil and the soiltemperature field around the pipeline showing a cyclical variation with crude oil pipelinetransportation type's changes cyclical. B Pipe inlet temperature with the advance of runningtime shows a cyclical trend. C Hot oily head temperature with the running distance increasedgradually decreased, the hot oil inlet temperature is the lowest inlet temperature, with the hotoil transport time, the temperature of hot oil gradually increased after the oil head, inlettemperature is also increased accordingly. As the temperature of hot oil tail gradually decreased with the increasing of the transport distance, but compared with the hot oil head, oiltail temperature decreased lower in the range reduced.According to the simulation result, detailed analysis and summary of influencing factorson the thermal characteristics of the batch transportation pipelines of the cold and hot crudeoil are made. It was found that increased cycle number is beneficial to the safe operation ofthe pipelines. While trying to increase the transportation amount to improve crude oil flowperformance not always obtains the expected effect. It has obvious effect under the lowthroughput and brin gs little effect under the high throughput. Properly increasing theout-station temperature of the cold oil is an effective measure to enhance flow performance ofthe crude oil. And it brings little effect with the hot oil. Based on the optimized heatingscheme of the cold and hot crude oil batch transportation, a mathematical model, which is ofthe optimum objective of minimum total operation cost, is established by comprehensiveconsideration of the thermal cost and the power charge. And then a case is studied accordingto the model. The results shows that heating the cold oil tail in proper proportion cansignificantly decrease the fuel cost. If the heating ratio of the cold oil is under 10%, the fuelcost decreases with the increase of the heating ratio and the decrease amplitude graduallyslowdown. If the heating ratio of the cold oil is above 10%, the fuel cost increase with theincrease of the heating ratio. So 10% is the optimal economy heating ratio. The operation costof the pipeline shows a decrease first and then an increase with the increase of the heatingratio. The lowest operation cost is 1% according the results of the example. If the heatingscheme were optimized, the thermal cost and the power charge should both be consideredunder the premise of safety. The decreasing of the total energy consumption was ensured toefficiently implement economic operation.Hot and cold batch transportation on the buried crude oil pipeline stress was analyzed indetail, focusing on the stress of buried elbow computation, analysis and affecting factors.Corresponding measures was proposed to reducing the thermal stress for buried elbow. Finiteelement method numerical simulation was used for elbow stress, the results show that: thehigher the oil temperature, the greater the elbow of the heat stress, and stress concentration atthe inner elbow radius. Finally, the hot and cold crude oil alternative transportation affectionon fatigue life of the pipeline was analyzed.Elaborated the mechanism of mixed oil in the order pipeline, contaminated concentrationwas analyzed based on one-dimensional diffusion theory and two-dimensional diffusiontheory, the method of contaminated concentration and given in the papers and compared thevarious formulas of the mixed oil quantity. An example and comparative analysis showed that the contaminated concentration of the new calculation method have high precision, simple tocalculate and the mixed oil quantity modified theoretical formula calculated results withexperimental results closer. Based on existing research-based CFD software to establish a hotand cold order pipeline contaminated concentration of crude oil mathematical model and thenumerical of conditions of the contaminated properties was studied on horizontal pipe, elbowand tapered pipe, to further improve the contaminated theory lays a foundation.