Research Papers: Petroleum Engineering

Mechanistic Modeling For Size-Selective Removal of Fines or Crystals From Thin Beds

[+] Author and Article Information
Peter Toma

P.R.Toma Consulting Ltd.,
Saanichton, BC, Canada

Ergun Kuru

Department of Civil Engineering,
University of Alberta–Edmonton,
Edmonton AB, Canada

Contributed by the Petroleum Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received March 2, 2015; final manuscript received January 22, 2016; published online February 22, 2016. Assoc. Editor: Mohamed A. Habib.

J. Energy Resour. Technol 138(5), 052902 (Feb 22, 2016) (7 pages) Paper No: JERT-15-1097; doi: 10.1115/1.4032618 History: Received March 02, 2015; Revised January 22, 2016

Recently developed laboratory and numerical techniques reveal that the very thin, near-wall (assumed) “laminar” fluid layer, an essential feature of all turbulent flow conditions, houses a world of identifiable jetlike structures including bursts generated from the near-wall regions and lumps of fluids projected back onto the wall zones. This activity, identified as “coherent structures” (CS), is recognized as an important mechanism for radial mass transport and energy dissipation, particularly in near-wall or fluid–bed zones. Buoyancy-, adhesion-, hydrodynamic-, and CS-related updraft forces act on particles positioned in the fluid–bed interface zone. Depending on the particle nature, bulk fluid properties, and transport velocity, three pairs of forces were identified corresponding to the equilibrium condition of deposit particles in each of the three size ranges with respect to the onset of entrainment into the bulk flow. This mechanistic approach using a set of force equilibrium equations to assess the potential entrainment of particles was first suggested in 1980 by Phillips and was later (2006) applied by Toma and a research team from ARC and PETRONAS to explain the aging of wall-deposit layer occurring during waxy crude transportation as an effect of size-selective removal of paraffin crystals formed from a mixture of crystalized alkanes. The merit of this paper, regarded as an extension of the 2006 publication, is to introduce a more general selective extraction rate function that enables calculations of both the rate of paraffin aging and size alteration of any fine, polydisperse particulate matter exposed to bulk turbulent flow, gas or liquid. Without any adjustment of the process or physical constants, the modeling results presented in this paper compared satisfactorily with the experimental results obtained independently by the Texaco Research (aging of waxy crude) and laboratory data from the University of Alberta on the effect of size-selective extraction of fine sand or glass beads (GB) initially deposited on the bottom of a pipe and exposed to a turbulent bulk flow of water. An overarching objective of this paper is to stir interest in mechanistic modeling and prediction of size-selective radial transport and separation for a broad range of industrial and environmental applications and studies and specifically in the recognition and use of burst-sweep CS structures for calculating radial transport of small particle sizes, particularly in near-interface zones exposed to turbulent flow conditions.

Copyright © 2016 by ASME
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Fig. 1

Critical particle removal shear stress versus particle diameters (the U-shaped PSC feature) calculated for (a) waxy crude-paraffin crystals and for (b) water–silica sand and the “pickup flow” regime for water–sand (ID = 9.5 cm and U = 0.31 m/s)

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Fig. 2

The four factors used for calculating the removal rate of particle “dp” from the observation area

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Fig. 3

(a) Entrainment tendency (Et) (L) and critical removal shear velocity (ucr*—Eq. (10)) (R) versus the size of GB calculated for water at U = 0.31 m/s and ID = 95 mm and (b) Et for water velocities U = 0.31 and 0.4 m/s (ID = 94 mm)

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Fig. 4

Size composition modification of GB bed exposed for 2 and 5.5 hrs to U = 0.31 m/s water flow (9.5 cm/9 m in length glass pipe [9]): (a) experimental data and (b) model results

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Fig. 5

Aging of JL for various operation times as experimentally [10] measured (a) or calculated (model introduced in this study) for generic field operation conditions (b) (generic field—basic “flow” data in Table 3)

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Fig. 6

Standard (as introduced in Ref. [4]) observation zone and bursting-related subzone expressed as wall units (wu)




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