Wax Deposition in Stratified Oil/Water Flow

Hoffmann, Rainer; Amundsen, Lene; Huang, Zhaohui; Zheng, Sheng; Fogler, H. Scott

doi:10.1021/ef2018989

Cited by 40 publications

(28 citation statements)

References 16 publications

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“…flow loop and found that the wax deposition rate in the oil/water two-phase flow was higher than that in single-phase flow. More recently, Hoffmann et al 35 performed two-phase, stratified oil/water flow-loop experiments and reported a higher deposit mass per unit area at a lower total flow rate. They also reported higher deposit thicknesses at higher water cuts and attributed this to a higher degree of gelation, resulting from decreased shear stress.…”

Section: ■ Introductionmentioning

confidence: 99%

Solids Deposition from Two-Phase Wax–Solvent–Water “Waxy” Mixtures under Turbulent Flow

Kasumu

Mehrotra

2013

Energy Fuels

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The deposition of solids from two-phase waxy mixtures (comprising a multicomponent paraffinic wax dissolved in a multicomponent solvent and water) was studied under turbulent flow conditions in a flow-loop apparatus, incorporating a cocurrent double-pipe heat exchanger. The deposition experiments were performed with 6 mass % wax solutions, containing 0, 5, 10, 15, 20, 25, and 30 vol % water, at different flow rates over 5600 < Re < 25 300, and at different hot and cold stream temperatures. In the bench-scale apparatus, the deposit was formed rapidly such that a thermal steady state was attained within 10−20 min in all experiments. The water content of the deposit was found to be not related to the water content of the waxy mixture. The deposit mass was found to decrease with an increase in Re, the waxy mixture temperature, and/or the coolant temperature. The deposit mass also increased as the water content of the waxy mixture was increased to about 10 vol % and decreased thereafter. The deposition data, analyzed with a steady-state heat-transfer model, indicated that the liquid−deposit interface temperature was close to the wax appearance temperature of the waxy mixture. The average thermal conductivity of the deposit was estimated to be 0.38 W m −1 K −1 . Overall, the results of this study confirm that the deposition process from waxy mixtures is primarily thermally driven.

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Section: ■ Introductionmentioning

confidence: 99%

Solids Deposition from Two-Phase Wax–Solvent–Water “Waxy” Mixtures under Turbulent Flow

Kasumu

Mehrotra

2013

Energy Fuels

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“…However, the increase of deposit thickness with water cut further increasing has hardly been discussed in previous studies and neither has been the mechanism. As was mentioned in the study of Hoffmann, lower flow rate and higher water cut would contribute to the enhancement of gelation behavior in oil–water wax deposition.…”

Section: Resultsmentioning

confidence: 82%

Modeling of wax deposition for water‐in‐oil dispersed flow

Zhou

Gong

Wang³

2015

Asia-Pacific J Chem Eng

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Wax deposition for waxy crude oil is a long standing issue in oil production and transportation systems. With oil produced with water, the oil-water two-phase wax deposition becomes a research hotspot. Experiments of water-in-oil emulsion wax deposition were conducted in the indoor flow loop. The deposit thickness of emulsion wax deposition shows a trend of increasing after decreasing with water cuts. As the oil or coolant temperature decreases, the gelation phenomena becomes more obvious, and the turning point of the deposit thickness curve versus water cut shifts toward the lower water cut. The influence of gelling adhesion in emulsion wax deposition was discovered. A new model was developed for predicting water-in-oil dispersed flow wax deposition based on the mechanisms of molecular diffusion and gelling adhesion. The deposit thickness values predicted by the new wax deposit model for water-in-oil emulsion laminar flows with different water cuts agree well with experimental results.

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“…[150] The presence of water in two-phase flows, as either water-in-oil or oil-in-water blend, has been reported to have inconclusive effects on wax deposition. While many studies have reported a decrease in wax deposition with increasing water fraction, [115,[150][151][152][153][154][155] others have reported an increase in wax deposition with increasing water fraction, [156,157] or no significant change due to the presence of water. [55,105] Clearly, more studies are needed to establish a conclusive effect of the presence of water on wax deposition.…”

Section: Water Droplets and Emulsionmentioning

confidence: 99%

A review of heat‐transfer mechanism for solid deposition from “waxy” or paraffinic mixtures

et al. 2020

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Summarized in this review are a large number of experimental and modelling studies for advancing the heat-transfer-based mechanism for solid deposition from "waxy" or paraffinic oils and mixtures. This comprehensive heat-transfer approach is entirely different from a more popular molecular-diffusion mechanism. It has evolved from numerous publications, over three decades, which explored topics related to thermodynamic, rheological, crystallization, solid deposition, and shutdown and deposit-aging behaviour of prepared multicomponent paraffinic mixtures of varying compositions to simulate "waxy" crude oils. These investigations covered a wide range of compositions, temperatures, and cooling rates-under static, sheared, laminar and turbulent conditions-in both the hot and cold flow regimes. The heat-transfer mechanism for wax deposition is based on (partial) freezing or liquid-to-solid phase transformation process, for which steady-state and unsteady-state mathematical models have been developed and validated with extensive laboratory data. Furthermore, a shear-induced deformation model for the deposit aging phenomenon has been developed and validated; it is based on a partial release of the liquid phase from the incipient gel, thereby causing an enrichment of heavier alkanes and a corresponding depletion of lighter alkanes in the deposit. A successful analogy with the ice deposition process has confirmed the wax deposition process to be also controlled by heat transfer, without involving any other mechanism for wax deposition. All of these previous studies confirm that wax deposition is predominantly a thermally driven process. K E Y W O R D S aging, cold flow, heat transfer, solid deposition, waxy crude oil 1 | INTRODUCTION Crude oils are complex mixtures of hydrocarbons, including high molar mass alkanes or paraffins, which are referred to as waxes. Waxes contain carbon numbers ranging from 18-65. [1] Crude oils that contain a significant proportion of high molecular weight paraffins or waxes are referred to as paraffinic or "waxy" crude oils. Waxes tend to crystallize and deposit on cooler surfaces because of their decreased solubility in the crude oil at lower temperatures. The highest temperature at which the first crystals start to appear, upon cooling of a "waxy" crude oil, is called the wax appearance temperature (WAT), which is also referred to as the cloud point temperature (CPT). The precipitation and deposition of solids are of significant importance in the production,

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Wax Deposition in Stratified Oil/Water Flow

Cited by 40 publications

References 16 publications

Solids Deposition from Two-Phase Wax–Solvent–Water “Waxy” Mixtures under Turbulent Flow

Solids Deposition from Two-Phase Wax–Solvent–Water “Waxy” Mixtures under Turbulent Flow

Modeling of wax deposition for water‐in‐oil dispersed flow

A review of heat‐transfer mechanism for solid deposition from “waxy” or paraffinic mixtures

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