Research On Waxing Properties Of Waxy Crude Oil And Its Influence On Heat Transfer

In recent years,China’s energy consumption has grown strongly,and carbon emissions have increased year by year.With the national energy saving and emission reduction requirements,the proportion of environmentally friendly energy consumption has increased,and some cities have begun to use fuel gas heating furnace heating systems.Most of the oil-fired heating systems use crude oil as fuel,but since the crude oil produced in my country is "three high" crude oil,it is generally heated by means of storage and transportation to improve its fluidity.The hot oil is continuously radiated outward in the oil pipeline and storage tank,and the precipitated wax crystals undergo a phase change,accompanied by changes in rheological properties,thermal properties,and microscopic wax precipitation properties.Therefore,an experimental study on the characteristics of crude oil wax precipitation was carried out to clarify the changing process of crude oil rheological characteristics,thermal characteristics and microscopic characteristics during the phase transition process,and then to analyze its influence on the heat transfer of crude oil phase transition through numerical simulation.It is of great significance to the supply and distribution of fuel oil in heating systems.In this paper,through the crude oil component analysis,rheological test,DSC test and gas chromatography analysis and other experimental methods,the characteristics of the wax precipitation of different oil samples were clarified,and the changing rules of the wax deposition process and the mechanism of influencing factors were summarized.The results show that the carbon number distribution of the wax component is the main factor affecting the wax precipitation point,and the gelatin content of the crude oil has a greater influence on the freezing point.Using polarized light microscopy test technology and corresponding particle analysis software,the microscopic waxing characteristics of crude oil were studied to clarify the changing rules of microscopic waxing characteristics of crude oil.A method for determining the coalescence point temperature corresponding to the formation of porous media in the process of crude oil wax precipitation was given.The box dimension was used to characterize the coalescence point,the correspondence between the coalescence point and the box dimension was clarified,and the box dimension corresponding to the Daqing crude oil coalescence point is finally determined to be about 1.3.Based on the experimental research and analysis of the wax precipitation characteristics of crude oil added with pour pointdepressant,it is clarified that the optimal concentration of EVA pour point depressant is300 ppm.At this concentration,the freezing point drops by 9℃,the coalescence point temperature drops by 1.4℃,and the pour point depressant The addition effectively suppressed the precipitation of wax.Using the waxy crude oil wide phase change zoning model to simulate the phase change heat transfer process of crude oil in the oil storage tank,the changing characteristics of the flow field and temperature field in the oil tank were clarified.The results show that during the phase transition,there are vortexes in the upper part of the tank and higher temperatures,lower temperatures in the lower part and thicker condensate layer.The comparative analysis of the effects of different phase transition characteristics on the solidification process of crude oil shows that the effects of equivalent specific heat capacity and coalescence point temperature on the phase transition heat transfer are more significant.