|
Type
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Journal
Article
|
|
Author
|
M.
Ramasamy
|
|
Author
|
Umesh
B. Deshannavar
|
|
URL
|
|
|
Volume
|
917
|
|
Pages
|
189-198
|
|
Publication
|
Advanced
Materials Research
|
|
Date
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6/2014
|
|
Abstract
|
|
Type
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Conference Paper
|
|
Author
|
Junfeng Yang
|
|
Author
|
Omar K. Matar
|
|
URL
|
|
|
Date
|
2014
|
|
Abstract
|
Crude-oil fouling commonly occurs at the heat
transfer surfaces of oil refinery pre-heat trains, reducing the heat transfer
and hydrodynamic efficiency of heat exchangers. The underlying mechanisms of
this process must be understood to design effective fouling mitigation
strategies. Fouling is believed to proceed via several individual steps:
initiation, transportation, attachment, removal and ageing. However, the
mechanisms of initiation, removal and ageing of the fouling layer are not yet
fully known. Current models for crude-oil fouling are mostly based on
relatively simple empirical or semi-empirical correlations that are only
accurate for specific crude oils under certain conditions and have no solid
chemical or physical basis. It is therefore essential to develop an accurate
comprehensive numerical fouling model and to understand the underlying
physical and chemical processes.
In this work, a Crude Oil Surrogate consisting of gasoline-, diesel-, and residual-range organic compounds in volumetric proportions of 24:34:42 is proposed as a practical standard crude oil model. The liquid thermalphysical properties of its constituent organic compounds were predicted using various empirical methods. The chemical reactions of the fouling process were modeled as one-step multi-phase heterogeneous reactions whereby sparingly soluble precursors in the crude oil form insoluble foulants. The asphaltene precipitation process was described using a chemical equilibrium model based on the Gibbs free energy. A rheological model and a first order kinetic model for deposition were used to describe the effects of ageing on liquid viscosity and thermal conductivity, respectively. Deposit removal by interfacial shear stress was modeled using the Large Eddy Simulation method. The resulting comprehensive model was implemented in a CFD tool to investigate the crude oil fouling process under a typical industrial heat exchanger. Based on these studies, we conclude that the rates of the chemical reactions involved in fouling are an order of magnitude faster than that of asphaltene precipitation and increase with the surface temperature. High bulk flow velocities generate a strong interface shear stress that eventually strengthens the interfacial wave rupture and foulant droplet entrainment, thereby increasing the removal rate. Ageing has negligible effects on the removal rate due to competition between structuration and destructuration terms. |
|
Type
|
Journal Article
|
|
Author
|
Junfeng Yang
|
|
Author
|
Omar Matar
|
|
URL
|
|
|
Volume
|
59
|
|
Issue
|
20
|
|
Date
|
November 23–25, 2014
|
|
Abstract
|
Crude-oil fouling proceeds via several
individual steps: initiation, transportation, attachment, removal and ageing.
At initiation, two foulant formation routes have been identified: chemical
reaction and asphaltene precipitation. Current fouling models either focus on
the kinetics of each route individually, or simply lumps the routes together.
Very few studies address the issue of interaction of the two routes.
The sparingly-soluble foulant precursor could either form larger insoluble fouling particles, or precipitate out of the crude-oil phase directly. Clearly, these two routes compete with each other, e.g. higher chemical reaction fouling rates lead to greater consumption of the sparingly-soluble foulant, and lower precipitation rate. Accounting for the mechanism of interaction between reaction- and precipitation-driven fouling is critical for accurate prediction of the overall fouling formation rate, and the development of fouling mitigation strategies. Authors develop CFD tools that account for the individual steps that accompany fouling in circular tubes, and use large eddy simulations to simulate turbulence. They use the simulations to elucidate the interaction between the different deposition routes. |
|
Type
|
Patent
|
|
Inventor
|
Steven W. LEVINE
|
|
Inventor
|
Glen B. Brons
|
|
URL
|
Free Full Text Source: http://www.google.com/patents/US8663455
|
|
Assignee
|
Exxonmobil Research And
Engineering Company
|
|
Patent Number
|
US8663455 B2
|
|
Issue Date
|
Mar 4, 2014
|
|
Abstract
|
