An experimental design approach for investigating and modeling wax deposition based on a new cylindrical Couette apparatus

Ji, Zhongyuan; Li, Chuanxian; Yang, Fei; Cai, Jinyang; Cheng, Liang; Shi, Yanan

doi:10.1080/10916466.2016.1159222

Cited by 6 publications

(9 citation statements)

References 5 publications

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“…Compared with the original CT system, the in-house cylindrical Couette device used in this work comprises a central stationary cylinder (wax deposition barrel) and an outer rotating cylinder (sample barrel) with the tested fluid occupying the annular space (see Figure ). The superiorities of the current device include: , convenient sampling and observation of the formed wax deposit, easier simulation and calculation of the flow field/temperature field in the device, and shear conditions similar to those of the real crude oil pipelines (see section 1 in the Supporting Information). Figure is the sketch of the in-house wax deposition device, detailed information on which could be seen in previously published papers. , …”

Section: In-house Cylindrical Couette Wax Deposition Devicementioning

confidence: 99%

“…The superiorities of the current device include: , convenient sampling and observation of the formed wax deposit, easier simulation and calculation of the flow field/temperature field in the device, and shear conditions similar to those of the real crude oil pipelines (see section 1 in the Supporting Information). Figure is the sketch of the in-house wax deposition device, detailed information on which could be seen in previously published papers. , …”

Section: In-house Cylindrical Couette Wax Deposition Devicementioning

confidence: 99%

“…Figure 1 is the sketch of the in-house wax deposition device, detailed information on which could be seen in previously published papers. 42,53 3. EXPERIMENTS 3.1.…”

Section: In-house Cylindrical Couette Waxmentioning

confidence: 99%

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Development of Asphaltenes-Triggered Two-Layer Waxy Oil Gel Deposit under Laminar Flow: An Experimental Study

et al. 2016

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In this work, we investigated the development of asphaltenes-triggered two-layer wax deposit with deposition time using an in-house wax deposition device, DSC, HTGC, SARA, and microscopic observation. For the pure waxy oil (Waxy Oil A), the formed wax deposit is a homogeneous and loose waxy oil gel. The wax deposit mass is relatively high and increases with increasing deposition time, while the wax appearance temperature (WAT), wax content, and ΔW of the wax deposit are relatively low and increase slowly with increasing deposition time. The critical carbon number (CCN) of the wax deposit is C24. The precipitated wax crystals (needlelike) in the wax deposit are liable to form a continuous network structure, which is adverse for the diffusion of wax molecules. The presence of asphaltenes in the pure waxy oil (Waxy Oils B–D) causes the formation of a two-layer wax deposit, which can be clearly characterized by the significant difference of structural strength. Different from the outer-layer wax deposit, the inner-layer wax deposit has smaller mass but higher WAT, wax content, CCN (C26), and asphaltene content. The WAT and wax content of the inner-layer/outer-layer wax deposits increase with increasing deposition time, while the asphaltene content of the inner-layer wax deposit stays almost the same at deposition time ≥ 1 h. The presence of asphaltenes greatly modifies the precipitated wax crystals’ morphology (spherical-like flocs) and then favors the diffusion of asphaltenes and wax molecules. Both molecular diffusion of waxes and Brownian diffusion of asphaltenes result in the formation of the two-layer wax deposit, which is formed by a four-step process. The increase of the original asphaltene content decreases the mass but increases the WAT and wax and asphaltene contents of the inner-layer wax deposit.

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Section: In-house Cylindrical Couette Wax Deposition Devicementioning

confidence: 99%

Section: In-house Cylindrical Couette Wax Deposition Devicementioning

confidence: 99%

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Development of Asphaltenes-Triggered Two-Layer Waxy Oil Gel Deposit under Laminar Flow: An Experimental Study

et al. 2016

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“…In this regard, the main goal of this investigation is to evaluate the influence of six different experimental variables on the rheological behavior of model waxy oils under gelling conditions. In the literature, substantial effort has been devoted to modeling crude oil intricate rheological behavior as a function of variables such as temperature, cooling rate, shear stress (or shear rate), disperse phase volume, and aging time. ,,,− It is also important to mention that the initial cooling temperature is another critical variable for the yield stress of waxy crude oils as reported by several authors. − Thus, some of the major experimental variables are assessed in this study. The system was composed of well-characterized but polydisperse paraffin waxes dissolved in spindle oil.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of the Rheology and Crystal Morphology of Model Waxy Oils under Gelling Conditions

2019

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The influence of six experimental variables (cooling rate, weight fraction of linear wax, weight fraction of branched wax, shear rate during cooling, final cooling temperature, and aging time) on the yield stress of gelled waxy oils was simultaneously investigated using an experimental design. Rheological tests were performed with systems comprising spindle oil and a blend of paraffin waxes. The waxes were characterized by differential scanning calorimetry, gas chromatography–flame ionization detection, Fourier transform infrared and 13C NMR spectroscopy, and X-ray diffraction, pointing to predominantly linear- and branched-type wax. Also, wax crystal morphology was assessed through polarized light microscopy. Cooling rate, wax content, shear rate during cooling, final cooling temperature, and aging time were the variables analyzed. The obtained results disclosed the relative importance of these variables on the viscoelastic properties of the gelled oils. Multiple linear regression was used to propose a mathematical expression for yield stress estimation. It was also found that the storage modulus in the linear region was highly correlated with the yield stress; thus, an alternative method to estimate the yield stress was proposed. The wax network restructuring level for different aging times are also discussed, and evidence indicates that after fracture the gel is unable to rebuild its original structure. The presented information may be useful for start-up prediction and/or the feasibility of a remediation procedure aimed at helping the removal of wax plugs.

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“…In terms of wax deposition mechanism, molecular diffusion, shear dispersion, Brown motion, gravitational settling, heat transfer, and other mechanisms were proposed, − but most of the researchers pointed out that molecular diffusion mechanism played a leading role in the process of wax deposition. In terms of wax deposition test systems, coldfinger, , flow loop, , Taylor–Couette device , and visual parallel plate wax deposition system , are developed to simulate the wax deposition characteristics. Numerous influencing factors on wax deposition were well evaluated such as oil temperature, , pipe wall temperature, , temperature difference, , flow rate, − and deposition time. − The aging property of wax deposits with time was also explained by the molecular diffusion/counter diffusion mechanism , and Ostwald ripening mechanism …”

Section: Introductionmentioning

confidence: 99%

Effect of Thermal Treatment Temperature on the Flowability and Wax Deposition Characteristics of Changqing Waxy Crude Oil

Zhu

Yang

et al. 2018

Energy Fuels

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The influence of thermal treatment temperature on the flowability and wax deposition characteristics of Changqing waxy crude oil was researched in detail through pour point/rheological tests, a cylindrical Couette wax deposition experimental device, DSC analyses, asphaltenes stability tests, and microscopic observations. It is found that the flowability of the crude oil can be greatly improved through increasing the thermal treatment temperature. Meanwhile, the wax deposition rate of the crude oil can be outstandingly inhibited with the increase of thermal treatment temperature from 50 to 70 °C. Moreover, the flow regime can also influence the wax deposition characteristics. Under cold flow regime (22 °C/12 °C), the structure of formed wax deposits is homogeneous while the aging of the wax deposits is not obvious. Under hot flow regime (30 °C/20 °C), the aging of the wax deposits is obvious, but a heterogeneous two-layer structure exists in the formed wax deposits at the thermal treatment temperatures 50 and 60 °C, with a hard/thin bottom layer and a relatively soft/thick surface layer. With the increase of thermal treatment temperature to 70 °C, the two-layer wax deposit structure cannot be identified due to the extremely thin wax deposit thickness. Increasing the thermal treatment temperature can disperse and activate the asphaltenes in the crude oil; the activated asphaltenes have stronger interactions with waxes and then decrease the WAT of the oil and change the precipitated wax crystals’ morphology further, hence dramatically improving the crude oil flowability and inhibiting wax deposition. Under hot flow regime, the two-layer wax deposit structure is mainly triggered through the diffusion of wax molecules and asphaltenes from the bulk oil into the wax deposits. Under cold flow regime, the asphaltenes have already coprecipitated with wax molecules into big wax flocs, which is difficult to diffuse from the bulk oil into the already existed wax deposits. Meanwhile, the aggravated flowability of bulk oil under cold flow regime further hinders the diffusion of wax molecules into the interior of the wax deposit. Therefore, the two-layer wax deposit structure cannot be found under cold flow regime.

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An experimental design approach for investigating and modeling wax deposition based on a new cylindrical Couette apparatus

Cited by 6 publications

References 5 publications

Development of Asphaltenes-Triggered Two-Layer Waxy Oil Gel Deposit under Laminar Flow: An Experimental Study

Development of Asphaltenes-Triggered Two-Layer Waxy Oil Gel Deposit under Laminar Flow: An Experimental Study

Experimental Investigation of the Rheology and Crystal Morphology of Model Waxy Oils under Gelling Conditions

Effect of Thermal Treatment Temperature on the Flowability and Wax Deposition Characteristics of Changqing Waxy Crude Oil

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