Effect of cooling rate on the wax precipitation temperature of “waxy” mixtures

Kasumu, Adebola S.; Arumugam, Sridhar; Mehrotra, Anil K.

doi:10.1016/j.fuel.2012.09.036

Cited by 42 publications

(58 citation statements)

References 12 publications

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“…The solvent used was Linpar 1416 V (APCO Industries, Ontario, Canada), which consisted of n ‐alkanes in the range of C 7 –C 19 , with a density of 763 kg/m 3 (at about 25 °C). The WAT of the ‘waxy’ mixture was 28 °C . Each 13‐L batch of the wax‐solvent mixture was prepared by mixing appropriate amounts of wax and solvent, and heated to about 70 °C and stirred for 2–3 h until a homogenous solution was achieved.…”

Section: Methodsmentioning

confidence: 99%

“…Note that each batch of the prepared ‘waxy’ mixture was sufficiently large to avoid any significant change in its composition, due to depletion in C 20 + components during the deposition experiments, and a new batch of the ‘waxy’ mixture was used after completing 6 deposition experiments . The density and viscosity of the ‘waxy’ mixture were estimated from the correlations reported previously …”

Section: Methodsmentioning

confidence: 99%

“…In contrast, the wax disappearance temperature (WDT), which is measured while heating the specimen, provides a better representation of the solid–liquid phase transformation temperature or the liquidus temperature . The WAT has been shown to be lower than the liquidus temperature due to the supercooling effects and it can vary with the cooling rate . However, the WAT is more relevant for the deposition process because it occurs under cooling conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The heat‐transfer modelling approach considers the deposit formation and growth to be a partial solidification or freezing process along with crystallization . According to the heat‐ transfer approach, the deposition occurs because of a temperature difference between the hot ‘waxy’ mixture temperature and the colder surroundings.…”

Section: Introductionmentioning

confidence: 99%

“…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 and bench‐scale flow‐loop studies have confirmed the interface temperature ( T d ) to remain constant, and close to the WAT, during the gelling and deposit‐growth periods. It is also pointed out that the heat‐transfer approach has been validated with experimental measurements under both the ‘hot flow’ (i.e.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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

Sinha

Mehrotra

2017

Can J Chem Eng

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Deposition from waxy mixtures in a flow‐loop apparatus under turbulent conditions: Investigating the effect of suspended wax crystals in cold flow regime

2019

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The effect of suspended wax crystals in wax-solvent mixtures on the solid deposition process in the cold flow regime was investigated experimentally and analyzed with a steady-state heat transfer model. A bench-scale flow-loop apparatus, incorporating a concentric-cylinder heat exchanger, was used to measure solid deposition, in the cold flow and hot flow regimes, from wax-solvent mixtures under turbulent flow conditions. The deposition experiments were performed with two wax-solvent mixtures, at two flow rates, with two coolant temperatures, at 8 wax-solvent mixture temperatures, and for several deposition times. The role of wax crystals on the deposition process was investigated by repeating some of the deposition experiments with a pre-filtered wax-solvent mixture. In all experiments, the deposit was formed rapidly such that a thermal steady-state was attained within 30 min. The deposit mass increased with decreasing the mixture temperature in the hot flow regime, reached a maximum as the mixture temperature became equal to the WAT, and then decreased linearly to zero in the cold flow regime as the mixture temperature approached the coolant temperature. Also, the deposit mass decreased with an increase in the Reynolds number and the coolant temperature. The data and predictions confirmed the solid deposition to be a thermally-driven process. The experimental deposit mass results in the cold flow regime, supported by model predictions, were identical for the unfiltered and filtered mixtures, which showed that the suspended wax crystals do not affect the deposit mass or thickness.

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Investigating the gelling behaviour of ‘waxy' paraffinic mixtures during flow shutdown

Ehsani

Mehrotra

2020

Can J Chem Eng

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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.

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Effect of cooling rate on the wax precipitation temperature of “waxy” mixtures

Cited by 42 publications

References 12 publications

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

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

Deposition from waxy mixtures in a flow‐loop apparatus under turbulent conditions: Investigating the effect of suspended wax crystals in cold flow regime

Investigating the gelling behaviour of ‘waxy' paraffinic mixtures during flow shutdown

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