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Precipitation and Fouling in Heavy Oil-Diluent Blends

机译:重油稀释剂混合物中的沉淀和结垢

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Heavy oil fractions rich in asphaltenes were mixed with diluents containing from 0.6 to 25% aromatics, and the resulting blends subjected to batch precipitation experiments at 85℃, and thermal fouling tests at surface temperatures in the range 230-310℃. Deposit compositions were determined, and are compared with suspended asphaltene composition. When the heavy oils were blended with the most aromatic diluents, precipitation and fouling were negligible. As the aromaticity of the diluents was decreased, the extent of asphaltene precipitation and the fouling rates increased. The solubility parameter of the blends, δ_(mix), and the flocculation solubility parameter for asphahenes, δ_f, were determined from measurements of the asphaltene flocculation onset by titration with heptane at temperatures from 25 to 50℃. Literature models predict no asphaltene precipitation (and presumably little fouling) will occur when [δ_(mix)- δ_f] > 0 . Both the amount of asphaltene precipitated in the batch experiments and the rate of thermal fouling decreased as the solubility parameter difference [δ_(mix)- δ_f] increased from negative to positive values. However, some precipitation and fouling were observed at the expected condition for mixture stability δ_(mix)≥ δ_f. As the temperature of the flocculation titration was raised toward the bulk temperatures of the experiments, values of [δ_(mix)- δ_f] decreased, and the agreement of the data with prediction of the point for zero precipitation and fouling improved. For unstable oil blends, the solubility parameter provides a good predictive measure of the tendency for asphaltene precipitation and for heat exchanger fouling.
机译:将富含沥青质的重油馏分与含0.6至25%芳烃的稀释剂混合,然后将所得混合物在85℃下进行间歇沉淀实验,并在230-310℃的表面温度下进行热结垢测试。确定沉积物组成,并将其与悬浮的沥青质组成进行比较。当重油与大多数芳香族稀释剂混合时,沉淀和结垢可以忽略不计。随着稀释剂芳香性的降低,沥青质沉淀的程度和结垢率增加。共混物的溶解度参数δ_(mix)和沥青质的絮凝溶解度参数δ_f,是通过在25至50℃下用庚烷滴定而测得的沥青质絮凝开始时确定的。文献模型预测,当[δ_(mix)-δ_f]> 0时,不会发生沥青质沉淀(可能几乎没有结垢)。随着溶解度参数差[δ_(mix)-δ_f]从负值增加到正值,分批实验中沥青质的沉淀量和热结垢率均降低。但是,在预期的混合物稳定性δ_(mix)≥δ_f的条件下,观察到一些沉淀和结垢。随着絮凝滴定温度升高至实验的整体温度,[δ_(mix)-δ_f]的值降低,并且数据与零沉淀点和结垢点预测的一致性得到改善。对于不稳定的油混合物,溶解度参数可以很好地预测沥青质沉淀和热交换器结垢的趋势。

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