Wax Precipitation Temperature Research Articles

Research on the Calculation Method for the Wellbore Temperature of Hot Nitrogen Gas Circulation Wax Removal and Plug Removal in Offshore Oil Fields

The problem of wax deposition widely exists in offshore oil fields; waxing of the oil tubing will lead to a reduction in the cross-sectional area of the flow and, in serious cases, the flow path will be blocked, causing the well to stop production. In order to cope with this problem, a thermal dynamic wax removal method has emerged in recent years that utilizes hot nitrogen gas circulation between the oil tube and annulus to raise the temperature of the oil tube to achieve the purpose of wax removal and plug removal and is quick and easy to operate. Unlike conventional wellbore temperature calculation methods, the wellbore temperature field under hot nitrogen circulation conditions is influenced both by the reservoir temperature gradient and the hot nitrogen injection temperature, injection pressure, and injection rate. In this paper, a temperature calculation model for a wellbore considering both annulus injection temperature and tubing temperature and their interactions is modeled, which can consider the effects of different hot nitrogen injection temperatures, injection rates, and injection pressures. The model is used to calculate the temperature distribution for different injection parameters in order to ensure that the tubing temperature is higher than the wax precipitation temperature and that the annulus temperature is not higher than the maximum temperature resistance of the rubber in the packer. The study provides a design method for wax removal and plug removal with hot nitrogen gas circulation.

Chemical inhibition of wax precipitation to improve cracking resistance of warm mix asphalts

In recent years, the wax-based warm mix additives are always doped into the asphalt to lower the construction temperatures, which can lead to the substantial energy savings and promote energy sustainability. However, few studies have considered the methods to inhibit the premature precipitation of wax-based warm mix additives in warm mix asphalt, which will deteriorate the cracking resistances of asphalt pavement. This paper introduced a new method from the essence of the phase separation between the wax-based warm mix additives and asphalt leading to the reduction of cracking resistance, which chemically inhibited the premature precipitation of common additives (linear aliphatic hydrocarbon (LAH), polyethylene (PE), fatty acid amides (FAA), and Fischer-Tropsch (F-T) waxes) by wax inhibitors (WIs) to improve the compatibility of additives, and the cracking resistances of warm mix asphalts with addition of WIs were also investigated through the multi-stress creep recovery (MSCR), linear amplitude sweep (LAS), dynamic mechanical analysis (DMA), and thermal fatigue tests. The results show that the wax precipitation temperature (WPT) of warm mix asphalt reduces with the addition of WIs to inhibit the precipitation of additives to improve the compatibility, and the wax inhibition efficiencies of WIs are better with the asphalt doped with short-chain additives at higher content. The WIs can provide the warm mix asphalt with the additional elasticity and decrease the dependency on the applied strain, which increases the high-temperature rutting and intermediate-temperature fatigue resistances. The cracking and thermal fatigue resistances of warm mix asphalt at the low temperature can also be improved after doping with WIs, which is leaded by the precipitation inhibition of additives. Therefore, it is promising to improve the cracking resistances of warm mix asphalts and develop a new energy-saving pavement by chemically inhibiting the precipitation of additives.

Inhibiting wax precipitation in asphalt binder from perspective of dispersing asphaltenes

In cold region, crystalline wax can continuously precipitate from the asphalt binder distilled from the crude oil after cooling, which seriously damages cracking resistance of the asphalt pavement at the low-temperature. Few researchers have developed wax inhibitors (WIs) to inhibit wax crystallization in the asphalt field and existing WIs only focus on direct interaction with wax crystals. Herein, the ionic liquid (IL) modified with different commonly used concentrations of graphene oxide (GO) (0.3 %, 0.6 %, 0.9 %, 1.2 % IL) was synthesized as novel WI through in situ polymerization from the new perspective that the dispersed asphaltenes could inhibit wax crystal network. The successfully synthesized nanocomposites at the optimal content (900 ppm) and component (IL-0.6 %GO) reduced wax precipitation temperature (WPT) of asphalt binders by 14 °C, and the synergistic effect of IL and GO in the nanocomposite has most significant effect on wax inhibition than the existing WIs (IL and Poly(methyl methacrylate) (PMMA)). IL indirectly inhibits wax crystal network by dispersing asphaltenes through π-π interactions and charge transfers from IL to asphaltenes, which is superior to the direct reduction of wax crystals by PMMA. Therefore, it is very effective and promising to synthesize nanocomposites as wax inhibitors from the new perspective of dispersing asphaltenes compared with existing WIs to improve the low-temperature performance of asphalt.

Investigation of wax inhibition efficiency based on alkane structures in model asphalt for sustainable utilization of wax inhibitors

In recent years, the wax inhibitors (WIs) are used to inhibit premature crystallization of alkane molecules in asphalt at low temperatures has yielded certain benefits. However, the method for effective and sustainable use of WIs in asphalt to avoid inefficient and expensive “trial and error” procedures has not yet been determined. In this paper, the model asphalts were established through non-waxy base asphalt doped with n-alkanes (Eicosane, triacontane and tetradecane) and isoalkane (Squalene), and the wax inhibition efficiencies and cracking resistance of model asphalt with addition of three typical WIs (poly (methyl methacrylate) (PMMA), nano-SiO2 hybrid PMMA and ionic liquid (IL) modified with graphene oxide (GO)) were directly characterized by wax precipitation temperature (WPT) and extended bending beam rheometer (Ex-BBR), double edge notched tension (DENT) and thermal fatigue tests, respectively. On this basis, the microscopic mechanism of wax inhibition was investigated by molecular dynamic simulation. The results show that the wax inhibition efficiencies are higher for the short-chain n-alkanes and ordered isoalkanes to improve the low-temperature cracking, ductile and thermal fatigue resistances more significantly, but the disordered isoalkanes and high content of long-chain n-alkanes will decrease the wax inhibition efficiencies of WIs. The WIs can increase diffusion coefficient and bond stretching, angle bending and dihedral angle torsion energies but decrease the Coulomb and van der waals (VDW) energies of wax molecules to inhibit the formation of wax crystals network. It is recommended to add WIs with higher content or efficiency for asphalts with heavy n-paraffins and low concentration of branched paraffins to inhibit wax precipitation. As for asphalts containing light n-alkanes and high concentration of branched alkanes, it is suggested to add smaller amount of WIs to save resources.

A novel method for determining the wax precipitation temperature in wax-based warm mix asphalt

ABSTRACT To accurately determine the wax precipitation temperature (WPT) of wax-based warm mix asphalt binder, a novel algorithm for WPT calculation was proposed, and the process of wax precipitation in asphalt, as well as the effects of aging, cooling rate, and shear rate on wax precipitation characteristics, were investigated through dynamic shear rheometer (DSR) tests and polarised light microscopy (PLM) experiments. The research findings reveal the following: The refined WPT algorithm exhibits heightened precision compared to the traditional viscosity method, showcasing superior reproducibility and mitigating human-induced errors. During the cooling process, wax molecules become oversaturated, leading to the precipitation of wax crystals and the transformation of asphalt into a solid–liquid two-phase system. The aging of asphalt causes changes in its composition, shifting the phase equilibrium towards favouring wax precipitation. The WPT of asphalt is also influenced by the cooling rate and shear rate, and a larger cooling rate and shear rate will reduce the WPT. Wax crystals are less numerous and more regular in shape at low cooling rates.

Flow assurance, simulation of wax deposition for Rawat field using PIPSIM software

One of the most relevant flow assurance issues in oil transportation is indeed the phenomena of wax deposition. Wax deposition occurs when the temperature along the pipeline falls below a point where it is described as Wax Appearance Temperature (WAT) The deposition may cause a lot of problems to the industry and definitely will involve expensive cause to overcome the problem. The flow system was built for Rawat field which is consists of (13) wells in the Rawat/Wateesh field. In this studies a series of cases were carried out at different flow rates, ambient temperature to study falling temperature through f pipline using PIPESIM Software and providing data from central petroleum laboratory and Rawat operating company. To check that temperature at all points along the flow line and trunk line is above the pour point and wax appearance temperature, check the requirement of heater, heat tracing and insulation for the pipelines more ever is used to studies the influence of changing flow rate, ambient temperature and water cut for pipeline temperature. The line size, line velocity and heat duty of the system have been calculated using excel program.The results show that the minimum temperature criteria for pipelines should be above 54C to avoid gelling of the fluid, Wax precipitation analysis results indicates that the minimum wax precipitation temperature for Wateesh W-was approximately 62°C and the same for Rawat RC-1 well were approximately 58°C.the flowlines size were determined 4” and 6” for trunk line.Also The results show that there is a direct relation between the wax deposition and temperature, It was observed that wax deposit increases with decreasing the temperature. On the other hand, an increase in flow rate results in a decrease in the wax deposition. Finally, hot insulation of the flow lines and trunk line was required, Electrical Heat Tracing to heat the fluid to 75 Deg, chemical injection such as wax inhibitors and pigging process to control the wax deposition.

Synthesis and characterization of nano-SiO2 hybrid poly(methyl methacrylate) nanocomposites as novel wax inhibitor of asphalt binder

Wax crystals may continuously precipitate from the asphalt binder during the cooling process, which seriously damages the low-temperature cracking resistance of the pavement. At present, few researchers have developed wax inhibitors (WIs) to hinder wax crystallization of the asphalt binders. In this paper, a novel wax Inhibitor was synthesized by the hybridization of organically modified Nano-SiO2 to the poly (methyl methacrylate) (PMMA), and the modification effect was validated by the ninhydrin chromogenic method and thermogravimetric analysis. The optimum content and composition of the organic nano-SiO2 hybrid PMMA WIs were also determined by the rheological tests, including viscosity measurement, wax precipitation temperature (WPT), and yield stress tests. Moreover, the wax inhibition mechanism was predicted by the combination of differential scanning calorimetry (DSC) and polarized optical microscopy (POM) tests. According to the obtained results, the successful modification of nano-SiO2 and PMMA were represented by the blue-violet precipitation and improved high temperature stability of PMMA, respectively. The optimal content and composition of nano-SiO2 hybrid PMMA was determined as 200 ppm and mass ratio of 1:4 (nano-SiO2 to PMMA), respectively. Compared with the co-crystallization between PMMA and wax crystals, the introduction of nano-SiO2 provided an additional and more stable heterogeneous nucleation template, which further reduced the size, and increased the dispersion of the wax crystals. Consequently, it is promising to develop the nanocomposites as WIs in the asphalt binder.

Study on the effect of CH4 dissolution on the microstructure of wax crystal in waxy crude oil

In this work, the influence of the dissolution of methane (CH4) gas on the wax crystal of waxy crude oil and the effect on the rheology of crude oil by dissolved CH4 were studied comprehensively. A self-deign high-pressure micro visualization device was developed to analyze wax crystals before and after gas dissolution. The crude oil from Shengli and Nanyang was tested by the device under various gas pressures. Results showed that the viscosity, maximum shear stress and equilibrium shear stress of Shengli crude oil decreased with the increasing pressure of the dissolved CH4. Due to the supersaturation of dissolved gas, the viscosity, maximum shear stress and equilibrium shear stress of Nanyang crude oil decreased initially and increased with the increasing pressure of dissolved CH4. The change in rheology of the dissolved gas crude oil can be a combined influence of gas pressure and dissolution mechanisms caused by CH4. Additionally, the wax precipitation point of Shengli crude oil decreased at the saturated dissolution of CH4, while Nanyang crude oil showed an increasing wax precipitation temperature. Notably, the wax precipitation area, number of wax particles, and average diameter of wax crystal in both crude oils gradually decreased with dissolution. However, a saturation of CH4 caused a small amount of precipitation of wax crystals in Nanyang crude oil, and the small wax crystals were aggregated to form the large wax crystals. The dissolution of CH4 gas can affect the wax crystallization process, crystallization ability, and morphology of wax crystals that resulted in significant variation in the rheology of crude oil.

Measurement and thermodynamic modeling of wax precipitation in asphalt binder

Considering asphalt as a mixed system composed of multiple solid and liquid phases based on the principle of phase equilibrium and regular solution theory, in this paper, the activity coefficient was used to describe the non-ideality of solid and liquid phases. According to the phase equilibrium equation, mass equilibrium equation, and normalization equation, the solid–liquid fraction under the equilibrium condition was calculated, and then the precipitation temperature of paraffin wax in asphalt and the precipitation amount at each temperature were determined. The gas chromatography-mass spectrometry experiment was conducted to measure the paraffinic, naphthenic and aromatic distribution of the asphalt as the input parameter of the prediction model. After the calculation results of the wax precipitation temperature (WPT) and wax precipitation curve (WPC) were compared with measured values acquired from experimental methods (viscosity method, Fourier-transform infrared spectroscopy (FTIR) method), it was found that the trend of WPC is approximately similar, but the WPT of the theoretical model was significantly higher than that of FTIR. The authors believe that this was caused by the overestimation of the thermodynamic properties of the aromatic components. After reducing the melting point and enthalpy of the aromatic components to a certain extent, satisfactory results were obtained.

Oiling low temperature separation process for dehydration and de-hydrocarbon of natural gas and practical application

In order to reach the specification of water and hydrocarbon dew point, most of the water and C3 and heavier hydrocarbons need to be removed from natural gas. Low Temperature Separation (LTS) process by throttling expansion or refrigeration is commonly employed for natural gas dehydration and de-hydrocarbon as the most economical method. In case of some special natural gas which contains small quantity of the wax (mainly C16+ components), wax is easily deposited in the throttling facilities that leads the blockage of internals of low temperature separator and affects safety operation. Oiling LTS process, a novel process for this kind of special natural gas, is investigated in this work. The oil is injected into the natural gas to reduce the wax precipitation temperature and thus to avoid wax blockage. It is a kind of improvement and innovation process based on conventional treatment ones. According to the simulation analysis and practical application for a natural gas processing plant in Aksu, China, the new process presents good performance. Also, it is found that the best injection point is at the inlet pipe of raw gas pre-cooler and the optimal injecting stream is from the three-phase separator. Also, the injection oil flowrate is determined by refrigerating temperature and the concentration of wax. Meanwhile, the detailed economic analysis of oiling LTS process was involved. Comparing the conventional process, its adding investment is around 423,583$ accounting on 5% total capital cost of this unit. However, from the comprehensive aspects, this optimized process presents a good economic benefit.

Variable-temperature Fourier-transform infrared spectroscopy study of asphalt binders from the SHRP Materials Reference Library

A wide range of asphalt binders were studied by variable-temperature Fourier-transform infrared spectroscopy (VT-FTIR) to understand how peak position and intensity are affected by temperature. Conditioning times of 20 and 60 hours were selected in the pressure aging vessel (PAV) to provide two levels of oxidative aging. Spectral intensity consistently increased at lower temperatures, but the magnitude of change varied a great deal depending on binder source. Peak positions within the 2,919–2,856 cm−1 range were found to shift to lower wavenumbers at lower temperatures. In contrast, peak positions within the 1,456–1,465 cm−1 range shifted higher. Shifts were found to both weaken or enhance by oxidation. The wax precipitation temperature (WPT) was generally found to experience a decrease after mild oxidation but increase after more extensive aging. No clear trends were found for the effect of oxidative aging on solid wax content as measured by VT-FTIR. These results provide new and important insights on how binder structure changes at cold temperatures.

Prediction of Wax Precipitation Temperature in Petroleum Fluids

The precipitation and deposition of wax has remained a major challenge that the oil industries is faced with during the production of waxy crude. This problem is simply an issue from the wellbore to the surface facilities. As a result of this, millions of dollars has been invested in remedial operations. In this research, a predictive model that uses thermodynamic relationship in predicting precipitation of wax has been developed. K-values for the solid-liquid equilibrium is described using solubility parameter, melting point temperature, enthalpy of fusion, and the molar volume for the components. The weight fraction was used to describe the wax mixture. Experimental data from three oil mixtures were used in comparing the model predicted wax appearance temperature (WAT). For oil mixA, the experimental value is 294.15K; Pauly et al predicted 302.15K while this work predicted 301.21K. For oil mixB, the experimental value is 300.15K; Pauly et al predicted 310.15K while this work predicted 308.91K. For oil mixC, the experimental value is 298.15K; Pauly et al predicted 302.15K while this work predicted 300.38K. The obtained results from this research confirmed the capability of the model in predicting Wax Appearance Temperature. A more conservative value for the WAT was predicted which is an improvement.

Experimental study of wax deposition pattern concerning deep condensate gas in Bozi block of Tarim Oilfield and its application

The Bozi block of the Tarim Oilfield is a typical tight sand condensate gas reservoir with serious wax plugging. So it is necessary to study the phase behavior and the wax deposition pattern of well fluids in Bozi gas reservoir, which will provide the phase enveloping diagram of the condensate gas and then help to control the paraffin deposition. In this study, the PVT tester and the self-designed microscopic solid deposition tester are used to get the phase enveloping line of the condensate gas. Such testing methods allow us to monitor phase changes of “gas-liquid-solid” system at different temperatures and pressures. In addition, the real reservoir conditions can be fully simulated with visibility. The result shows that the phase behaviors of the wax-containing condensate gas is extremely complex. Under different temperature and pressure, gas phase, gas-liquid, gas-solid, and gas-liquid-solid multiphase appear respectively. The main wax components of Bozi 104 well are C16∼C30, and their content is 0.111% mol per unit mole of condensate gas. The wax precipitation temperature of condensate oil is 15.4°C, the maximum instantaneous wax deposition volume is 0.2258% per unit mass of condensate oil, and its cumulative volume is 9.49% per unit mass of condensate oil. When the pressure is above the dew point, the solid wax is not dominated by the condensate oil but by long plate-like coarse wax crystals. When the pressure is below the dew point, the solid wax is condensed from the gas. The wax is soluble to the condensate oil. Then they form a transparent colloidal, glassy block material, which has a strong binding effect on the condensate oil.

Ethylene–Vinyl Acetate Copolymer and Resin-Stabilized Asphaltenes Synergistically Improve the Flow Behavior of Model Waxy Oils. 2. Effect of Asphaltene Content

In part 1 (10.1021/acs.energyfuels.7b03657), the synergistic effect of ethylene–vinyl acetate copolymer (EVA) pour point depressant (PPD) and rensin-stabilized asphaltenes on improving the flowability of synthetic waxy oil has been verified. This paper is a continuous work studying the effect of the asphaltene content (0.01–3 wt %) on the synergistic effect between EVA PPD and resin-stabilized asphaltenes. The results showed that, in the absence of EVA and with the increase of the asphaltene content, the precipitated wax crystals of the waxy oil tend to grow gradually from initial big needle-like to smaller and more regular (spherical-like) particles with a larger amount; therefore, adding aphaltenes can only decrease the apparent viscosity of waxy oil at the temperature range slightly lower than the wax precipitation temperature (WPT) (the precipitated wax crystal amount is low), and the temperature range is broadened by increasing the asphaltene content. When the temperature is decreased far below the W...

Wax Precipitation Temperature Measurements Revisited: The Role of the Degree of Sample Confinement

In this work, the wax precipitation temperature (WPT) measurements of crude oils are revisited. The conventional methods used to assess the WPT of crude oils are analyzed and the results available are discussed in detail. In addition, three methods, namely polarized light microscopy, microdifferential scanning calorimetry (μDSC), and rheometry, are employed to evaluate the WPT of two Brazilian waxy crude oils. It is shown that polarized light microscopy and μDSC are the most suitable methods to assess the WPT of crude oils and that rheometry can only be used for that purpose under very specific circumstances. In particular, the results indicate that rheometry is able to detect the WPT of crude oils only by decreasing the geometry gap to a small enough value. Moreover, it is shown that the degree of sample confinement has a key role on the accuracy of WPT measurements, so that care must be taken when using laboratory data to design field operations. Discussions on the origin of the effects of confinement a...

On the use of Modulated Temperature Differential Scanning Calorimetry to assess wax crystallization in crude oils

In this paper, measurements of the Wax Precipitation Temperature (WPT) of waxy crude oil samples by a type of Modulated Temperature Differential Scanning Calorimetry, commercially termed StepScan™ (SSDSC), are reported. Repeatable and reliable measurements of WPT by SSDSC are found to depend on specific experimental cooling parameters used with this technique. When appropriate parameters are used, two exothermic peaks can be detected on the non-reversing component and one peak on the reversing component (RC) of SSDSC thermograms. We also present indications that the onset of the peak on RC is related to the change in phase angle detected by sinusoidal temperature modulation programs and that it likely does not correspond to a measurement of the WPT. Additionally, by further adjusting SSDSC experimental parameters, because SSDSC is not based on a sinusoidal temperature modulation, reproduction of SSDSC cooling programs by rheometry and Polarized Light Microscopy (PLM) is possible. It was found that the different values used for the SSDSC cooling parameters, when reproduced on the rheometer, do not impact the oil’s rheology significantly at the applied shear rate. Moreover, it is shown that the onset of the peak detected on the RC portion of SSDSC thermograms is associated with a significant increase in average wax crystal number, as indicated by microscopy; while the consequences on average wax crystal size are found to depend on the initial cooling temperature. Furthermore, comparisons of WPT determination by SSDSC and by conventional DSC analysis show the potential of SSDSC in obtaining comparable and more reliable WPT measurements depending on crude oil composition and SSDSC cooling parameters.

Determination of the optimizing operating procedure for DSC test of wax-solvent samples with narrow and sharp wax peak and error analysis of data reliability

Differential scanning calorimetry (DSC), as a convenient and reliable thermal analysis technique, is widely used to analyze wax precipitation characteristics. This paper studies the optimizing operation conditions in DSC test for wax-solvent mixtures characterized by a narrow and sharp wax peak to promote the test reliability. The influences of cooling rate and isothermal time on the wax precipitation characteristics of wax-solvent samples are investigated through DSC experiments. The shape of heat flow curve, wax precipitation temperature and measured wax content are all affected. According to the stability and repeatability of test results, the optimizing procedure is determined for this kind of oil samples. What is more, this paper analyzes the applicability of the optimizing procedure on a crude oil sample with broad and mild wax peak. Experiment errors in the parallel experiments conducted under the determined procedure are checked, and all of them are in acceptable error ranges. This study may provide a meaningful reference for DSC application and a rethink of the test standard in practical operation for particular waxy mixtures.

Thermal behavior and solid fraction dependent gel strength model of waxy oils

Thermal behavior of waxy oils is investigated using the techniques of thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). Model waxy oils and real waxy crude oils are utilized. Decomposition temperatures of waxy oils are obtained using TG analysis. The effects of thermal history, wax content, and additive on the gelation process of waxy oils are investigated using DSC. The DSC method provides a measure of wax solubility as well as solid fraction. An integration method and a computation method are utilized to predict solid fraction. In addition, wax crystallization onset points are obtained at the cooling rates ranging from 1 to 20 °C min−1. Similarly, wax dissolution endset points are obtained at heating rates ranging from 1 to 20 °C min−1. Extrapolated onset and endset points yield wax precipitation temperature and wax dissolution temperature, respectively. Subsequently, wax solubility curves are obtained using thermodynamic computations. A wax precipitation temperature method and a wax dissolution temperature method combine thermodynamic phase behavior with onset/endset points to predict solid fraction. Both the wax precipitation temperature method and the wax dissolution temperature method can predict solid fraction of waxy oil samples. The wax precipitation temperature method and the wax dissolution temperature method are accurate when the temperature is close to the wax appearance temperature. A heat-integration method provides accurate values of the solid fraction at temperatures significantly below the wax appearance temperature. Therefore, integration method and wax precipitation temperature/wax dissolution temperature method are combined to predict solid fraction. The effect of solid fraction on yield stress is also investigated using differential scanning calorimetry and rheometry. Finally, a new solid fraction dependent gel strength model is obtained for shut in and restart of waxy crude oil pipelines.

Modeling of Solids Deposition from “Waxy” Mixtures in “Hot Flow” and “Cold Flow” Regimes in a Pipeline Operating under Turbulent Flow

Solids deposition from “waxy” mixtures under turbulent flow in a pipeline was modeled as a moving boundary problem involving liquid–solid phase transformation. The developed model is applicable for the “hot flow” regime (i.e., with the mixture temperature above its wax appearance temperature, WAT) and the “cold flow” regime (i.e., with the mixture temperature below its WAT, resulting in solid particles suspended in the liquid phase). A recently proposed correlation for the wax precipitation temperature (WPT) as a function of the wax concentration and the cooling rate was used to predict the transition from the “hot flow” regime to the “cold flow” regime. Predictions obtained for both radial and axial deposit growth in the pipeline with time in the “hot flow” and “cold flow” regimes were found to be in agreement with the trends observed in the laboratory deposition results reported in the literature. The predicted deposit thickness in the axial direction increased under the “hot flow” regime, reached a maximum as the liquid temperature approached the WAT of the wax–solvent mixture, and decreased subsequently under the “cold flow” regime. The axial location for the transition from the “hot flow” regime to the “cold flow” regime was predicted to shift with changes in the inlet mixture temperature, pipe wall temperature, and Reynolds number. The predicted maximum deposit thickness was also impacted by these variables. The predictions in this study indicate that solids deposition in pipelines carrying “waxy” mixtures could be decreased by maintaining the flow under the “cold flow” regime. This study shows that solids deposition from “waxy” mixtures can be modeled satisfactorily as a thermally driven process involving partial solidification.

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

The wax precipitation temperature (WPT) of several compositions of a multicomponent “waxy” mixture, comprising Parowax in Norpar13, was measured at controlled cooling rates. The results of this study indicated that the WPT of a “waxy” mixture is not a constant property, as it varied with the cooling rate. The measured results were expressed as a function of the cooling rate and mixture composition. With the WPT being dependent on the cooling rate, it may not correspond to the thermodynamic liquidus temperature for the liquid-to-solid phase transformation process.