F-28 Mechanistic Investigation of Fouling of Heat Exchangers Caused by Asphaltene Deposition
A systematic investigation of crude oil properties and asphaltene behavior at high temperatures and pressures was performed to understand the occurrence and the magnitude of asphaltene-induced fouling in heat exchangers. The physico-chemical characterization of the oil samples used in this study included the application of a novel methodology to separate the crude oil into asphaltene and multiple maltene fractions, with known properties such as molecular weights and densities. Asphaltene polydispersity, onsets of asphaltene precipitation, and the amount of precipitated asphaltenes were also investigated, as well as the rheological behavior of the crude oils of interest. A novel experimental apparatus that can operate in batch and continuous flow modes were built and operated to investigate the behavior of crude oil blends at high temperatures and pressures. In batch mode, the setup was used to investigate the effect of temperature on asphaltene stability and precipitation tendency. The extent of fouling at high temperatures was studied using the continuous flow mode.
According to evidence obtained in this work, asphaltene solubility decreases with increasing temperature, which leads to the formation of asphaltene deposits on the wall of the heat exchanger tubes. This mechanism, which might seem counterintuitive, is different from the asphaltene behavior reported in upstream conditions.
A modeling framework to predict the precipitation and deposition of asphaltenes at high temperatures and pressured, including a heat transfer model, was also developed and the methodology and some preliminary results are also presented in this report.