Petroleum stability effects on heat exchanger fouling were studied using mixtures of heavy oil containing asphaltenes, and carrier fluids consisting of a fuel oil cut with varying amounts of added aliphatic or aromatic fluid. Fouling was measured in a recirculation loop using an annular, electrically heated probe. The effects of carrier fluid composition, dissolved oxygen, and heteroatomic species additions were investigated. Insolubles formed in the mixtures, measured by hot filtration, and deposits on the probe had compositions similar to asphaltenes. Fouling by asphaltenes at moderate bulk temperatures and surface temperatures below 220 Grad C is controlled by solubility phenomena which affect the concentration of the asphaltenes found in suspension. The tendency of the asphaltenes to aggregate, and the fouling rate, is correlated with the colloidal stability index. At a fixed asphaltene concentration, fouling was decreased by increases in amounts of aromatics, and increased by n-alkane additions. Higher asphaltene content in solution does not necessarily translate into increased fouling. The fouling rates for these unstable oils can be roughly correlated with the concentration of suspended asphaltenes, as measured by hot filtration. The presence of dissolved oxygen resulting from saturation of the solution with air at a pressure of 410 kPa increased the fouling rate by about an order of magnitude, compared to that under nitrogen saturation. This increase was accompanied by an approximate doubling of the concentration of precipitated solids. Reactive oxygen-containing species such as benzoyl peroxide and ethanediol slightly enhanced fouling when present at 1,000 ppmw level in a nitrogen-blanketed solution. Thiophenol acted much as an antifoulant, reducing the fouling of the heat transfer probe to a very low level. To determine the role of asphaltene aggregation in fouling, improved methods are necessary to characterize the aggregates and relate the size of those in the suspension to what is found in the deposited film.


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    Title :

    Petroleum stability and heteroatom species effects in fouling of heat exchangers by asphaltenes


    Additional title:

    Die Stabilität des Erdöls und der Einfluß von Fremdatomen bei der Verschmutzung der Wärmetauscher durch Asphaltverbindungen


    Contributors:

    Published in:

    Publication date :

    2000


    Size :

    7 Seiten, 9 Bilder, 2 Tabellen, 18 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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