关键词: 石蜡基原油, 降凝剂, 剪切效应, 凝点, 熵产, 数学模型

Abstract: Shear is one of the major factors influencing flow properties of waxy crude beneficiated with the pour-point depressants(PPD). The data obtained from pipelines in operation and laboratory experiments reveal that there exists a good relationship between the gel-point increment due to shear and the gel-point reduction of the non-sheared beneficiated crude,which is defined as the gel-point difference between the virgin crude and the crude beneficiated with PPD before shear.On the basis of the general rules of shear effect,a mathematical model for correlating the gel-point of the sheared-PPD-beneficiated crude oil and the entropy generation due to viscous flow in the shear process and being applicable to other crude oils was developed.By using this model,the gel point of the PPD-beneficiated crude oil sheared at any entropy generation can be predicted,provided that the gel points of the virgin crude and the PPD-beneficiated crude before shear are known. Among a total of 294 data of gel points obtained from the PPD-beneficiated Daqing crude,PPD-beneficiated Xinjiang blended crude and PPD-beneficiated Zhongyuan crude,compared with predicted values,one half has a deviation within 1℃,and 86.8 percent of the data has a deviation within 2℃.The average absolute deviation of gel points predicted by the presented model is 1.12℃.This model provides a basis for numerical simulation of flow behaviors of PPD-beneficiated crude in pipeline transportation.

Key words: paraffin-based crude, pour-point depressant, shear effect, gel point, entropy generation, mathematical model