Modeling of Deposit Formation from “Waxy” Mixtures via Moving Boundary Formulation:  Radial Heat Transfer under Static and Laminar Flow Conditions

Bhat, Nitin V.; Mehrotra, Anil K.

doi:10.1021/ie050149p

Cited by 52 publications

(147 citation statements)

References 32 publications

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“…Without such assumptions, the numerical solution methodology can become complex and time-consuming. 17 Model Description. When a cold finger assembly is inserted into a waxy mixture or crude oil (with the inside of the cold finger exposed to a cooler temperature lower than the WAT of the waxy mixture), a deposit layer would start to form on the outer cold finger surface due to a partial freezing process.…”

Section: ■ Unsteady-state Heat-transfer Modelmentioning

confidence: 99%

Solids Deposition from Wax–Solvent–Water “Waxy” Mixtures Using a Cold Finger Apparatus

Kasumu

Mehrotra

2015

Energy Fuels

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The solids deposition from one-phase and two-phase waxy mixtures (comprising a multicomponent paraffinic wax dissolved in a multicomponent solvent, and water) was studied using a cold finger experimental apparatus. The deposition experiments were performed with a 10 mass % wax solution, containing 0, 10, 20, and 30 vol % water, with two different rates of agitation, and for nine different deposition times ranging from 30 s to 24 h. The water content of the deposit was found to be not related to the water content of the waxy mixture. The short-duration experiments showed the deposition process to be very fast, with more than half of the deposition process completed in 30 s. Following a rapid rate of deposition initially, the deposit mass was observed to increase slowly to reach steady state at about 12 h. The deposit mass decreased with an increase in the agitation speed. The deposition data were modeled satisfactorily with a steady-state heat-transfer model and an unsteady-state model based on the moving boundary problem formulation. The results confirmed the liquid−deposit interface temperature to be equal to the wax appearance temperature (WAT) of the wax solution throughout the deposition process, i.e., for all deposition times. The results of this study provide further confirmation that the solids deposition process can be described adequately with an approach based solely on heat-transfer considerations. ■ INTRODUCTIONThe precipitation and deposition of solids are of significant importance in the production, transportation, and processing of "waxy" or paraffinic crude oils because wax deposition can damage oil reservoir formations and wells and cause blockage of pipelines and process equipment. Solids deposition in pipelines and process equipment causes an increase in pressure drop, an increase in pumping power requirement, and/or a decrease in efficiency. Challenges associated with solids deposition are more severe in cold environments, especially in subsea conditions, where seabed temperatures can be as low as 4°C. 1 With increasing prevalence of deep-water−oil recovery, 2 crude oil is transported over longer distances with an increase in exposure to low temperatures. Such solids deposition problems are expected to become worse and so will the control and remediation costs associated with them.Waxes are mixtures of long-chain hydrocarbons with carbon numbers ranging from 18 to 65. 3 Waxes occur in significant proportions in paraffinic crude oils. These waxes are less soluble in the crude oil at lower temperatures and tend to crystallize and deposit on cooler surfaces. The temperature at which the first wax crystals start to appear in the crude oil during cooling is known to as the wax appearance temperature (WAT) or the cloud point temperature (CPT). It is pointed out that the wax disappearance temperature (WDT, measured while heating a sample) has been shown to provide a better representation of the true solid−liquid phase transformation temperature or the liquidus temperature. 4 Although somewhat higher ...

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Section: ■ Unsteady-state Heat-transfer Modelmentioning

confidence: 99%

Solids Deposition from Wax–Solvent–Water “Waxy” Mixtures Using a Cold Finger Apparatus

Kasumu

Mehrotra

2015

Energy Fuels

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“…The growth of a wax deposit layer is accompanied by the release of the latent heat of phase change. The moving boundary problem formulation has been used for developing mathematical models based on the heat‐transfer approach . In the heat‐transfer approach, the liquid‐deposit interface temperature is taken to be equal to the WAT of the wax solution throughout the deposition process.…”

Section: Introductionmentioning

confidence: 99%

“…The moving boundary problem formulation has been used for developing mathematical models based on the heat-transfer approach. [18,[26][27][28][29] In the heat-transfer approach, the liquid-deposit interface temperature is taken to be equal to the WAT of the wax solution throughout the deposition process. Batch cooling studies under static and sheared conditions [30,31] and bench-scale flow-loop studies [15][16][17][19][20][21][22] have confirmed the interface temperature (T d ) to remain constant, and close to the WAT, during the gelling and deposit-growth periods.…”

Section: Introductionmentioning

confidence: 99%

Investigation of wax deposit ‘sloughing’ from paraffinic mixtures in pipe flow

Sinha

Mehrotra

2017

Can J Chem Eng

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Deposit ‘sloughing’ from ‘waxy’ crude oils has been described in the literature as a possible mechanism, leading to partial or complete dislodging of the deposit from the pipe wall due to changes in flow parameters. A bench‐scale flow loop apparatus was used to investigate ‘sloughing’ with prepared single‐phase ‘waxy’ mixtures of a multicomponent paraffinic wax dissolved in a multicomponent solvent. Experiments were performed to study the changes in the deposit‐layer thickness due to step increments in the ‘waxy’ mixture flow rate, the mixture temperature, and the coolant temperature. It was observed that the deposit‐layer thickness decreased with an increase in each of the three parameters; however, a complete or sudden dislodging of the deposit‐layer did not occur in any of the experiments. A steady‐state heat‐transfer model was used to predict the variation in the deposit mass or thickness due to changes in the selected parameters. In each case, the step‐wise decrease in the deposit thickness, as observed experimentally, was predicted to be caused by changes in the thermal resistance and/or thermal driving force.

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“…In the actual wax deposition loop, the temperature distribution will appear not fully development, so it is necessary to solve the problem of hot inlet. In order to obtain the temperature distribution of the loop test section, the usual method is dimensionless energy balance equation and boundary condition by introducing dimensionless parameters, then the temperature field distribution of the analytical solution can be obtained after proper simplification (The form of Bessel function), the solution process is more complex (Zhu G J., 1989;Li et al, 2014;Saracoglu et al, 2000;Bhat et al, 2005). In addition to this Bessel function method, the temperature distribution of the test segment can be obtained by using Handal method for the heat transfer characteristics of the tested tube of wax deposition loop (Handal A D., 2008).…”

Section: Introductionmentioning

confidence: 99%

The Study on Calculation Method of Temperature Distribution of Tested Tube for Wax Deposition Experimental Loop

Rong-ge¹,

Jin²,

Tian³

et al. 2018

Frontiers in Heat and Mass Transfer

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The loop experiment device plays an important role in the study of wax deposition, and the calculation of the temperature distribution of the test section is the key to establish the wax deposition model. In the conditions of the wax deposition was not formed and constant wall temperature of the tube, the energy balance equation is solved by using separation of variables and combining the Kummer equation (S-K method), the distribution law of temperature in the test section is obtained, and the solution results was compared with Svendsen method, the difference between the results obtained by the two methods and the experimental results is also analyzed. The results showed that, the temperature distribution of the test section is consistent with the two methods, and the computing result of Svendsen method is generally higher than the S-K method. Under different axial distances for the take value, the maximum difference of computing results between the two methods is large when the position is farther away from the entrance, and the maximum difference is 0.27℃. Under different radial distances for the take value, with the increase of the axial distance, the difference between the results obtained by the two methods increases gradually in general, and the greater the radial distance, the greater the difference, the maximum difference is 0.27 ℃, thus the calculation results of these two kinds of methods have a higher coincide degree. The results obtained by the two methods are higher than the experimental results, but the difference is small, the results obtained by the S-K method are closer to the experimental results, and this method can avoid solve the numerical integration (Svendsen method) and the inconvenience of Bessel function, so it has a certain advantages.

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Modeling of Deposit Formation from “Waxy” Mixtures via Moving Boundary Formulation: Radial Heat Transfer under Static and Laminar Flow Conditions

Cited by 52 publications

References 32 publications

Solids Deposition from Wax–Solvent–Water “Waxy” Mixtures Using a Cold Finger Apparatus

Solids Deposition from Wax–Solvent–Water “Waxy” Mixtures Using a Cold Finger Apparatus

Investigation of wax deposit ‘sloughing’ from paraffinic mixtures in pipe flow

The Study on Calculation Method of Temperature Distribution of Tested Tube for Wax Deposition Experimental Loop

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