Investigating the gelling behaviour of 'waxy' paraffinic mixtures during flow shutdown. (22nd June 2020)

• Record Type: Journal Article
• Authors: Ehsani, Sina; Mehrotra, Anil K.
• Is Part Of: Canadian journal of chemical engineering. Volume 98:Number 12(2020)
• Page Start: 2618
• Page End: 2631
• Publication Date: 2020-06-22
• Subjects: gel formation -- heat transfer -- paraffin deposition -- pipeline shutdown -- waxy oil; Chemical engineering -- Periodicals; Technology -- Periodicals; 660.05
• DOI: 10.1002/cjce.23811
• Languages: English
• ISSNs: 0008-4034

Abstract

Abstract: The flow of waxy or paraffinic crude oils in a pipeline could be shutdown for a variety of reasons, resulting in their cooling and subsequent gelling. Gel formation from a multicomponent wax‐solvent mixture during flow shutdown was investigated experimentally and analyzed with a transient heat‐transfer model based on the moving boundary problem formulation. The gelling experiments were performed with a 0.10 g/g wax‐solvent mixture in a flow‐loop apparatus, following the formation of a steady‐state deposit layer in turbulent flow regime, at two initial wax‐solvent mixture temperatures, with a constant coolant temperature, and for different shutdown times. The gel formation was found to be a fast process, which continued until the gel fully occupied the deposition tube. Gas chromatographic analyses of the deposit samples (under sheared cooling) and the gel samples (under static cooling during flow shutdown) indicated significant differences in the composition and the total wax content. The deposit samples showed an enrichment of heavier paraffins, whereas the composition of gel samples was comparable to that of the original wax‐solvent mixture. The predictions from the transient model showed that a lower initial oil temperature, a lower coolant temperature, and a smaller pipe diameter would result in a faster blockage of the pipe. The predictions from the moving boundary problem formulation agreed well with the flow shutdown data, which further confirmed that the solid and gel formation from wax‐solvent mixtures is modelled satisfactorily as a heat transfer process.