Particle Video Microscope Research Articles

Investigation on natural gas hydrate dissociation from a slurry to a water-in-oil emulsion in a high-pressure flow loop

Investigations of natural gas hydrate dissociation from a slurry to a water-in-oil emulsion are conducted in a high-pressure hydrate experimental flow loop equipped with on-line microcosmic instruments including a focused beam reflectance measurement (FBRM) probe and a particle video microscope (PVM) probe. Three stages of the dissociation processes are observed and sketched in a conceptual mechanistic diagram, including initial dissociation with agglomeration, dissociation with breakage and re-aggregation, and thorough dissociation. The influences of initial pressure, flow rate, and water cut on hydrate dissociation are discussed. The pressure drop is increased by hydrate particle agglomeration, which increases the risk of hydrate plugging; thus, hydrate systems require close monitoring during the hydrate slurry dissociation process. Based on the classical kinetics theory, an improved hydrate dissociation model is developed by introducing a coupled heat- and mass-transfer influence coefficient and by considering the changes in the hydrate dissociated area based on the chord length data recorded by the FBRM probe. The intrinsic rate constant for natural gas hydrate dissociation is within the range of 1.41 × 103–7.18 × 104mol·Pa−1·s−1·m−2, and the activation energy of dissociation ranges from 68.2 to 72.3 kJ·mol−1. The reported investigation is significant for the application of hydrate slurries in risk-management methods to address issues of hydrate flow assurance in deep-water systems.

Characterization of droplet sizes in large scale oil–water flow downstream from a globe valve

Oil–water dispersed flows produced at valves or restrictions are very common in industry. For example, crude oil desalting processes normally use dispersion valves to mix the dilution water. In this case, the knowledge of dispersed droplet sizes is crucial for the design and optimum control of the process. However, little work has been devoted to characterize and model droplet sizes produced in industrial-type valves. The present work studies water droplet sizes produced by the passage of oil–water flow through a globe valve mounted in a large scale flow loop of 0.1 m internal diameter. Experiments were performed under different pressure drops across the globe valve, and different oil and water flow rates. Produced water droplet sizes were measured in situ downstream from the globe valve location using particle video microscopy. Droplet sizes were compared with theoretical scales for turbulent and viscous break-up. The effect of the volume fraction of dispersed phase on droplet size was also examined. In addition, droplet size distributions were analyzed and fitted using known statistical functions.

Microscale Detection of Hydrate Blockage Onset in High-Pressure Gas–Water Systems

A high-pressure stirred autoclave cell equipped with a focused beam reflectance measurement (FBRM) probe and a particle video microscope (PVM) was used to study hydrate formation and plugging in gas–water systems as a function of shear rate. These probes allowed estimates of the mean hydrate particle size and number of hydrate particles to be correlated with the hydrate volume fraction and the hydrate slurry’s resistance-to-flow. Before reaching the hydrate volume fraction φtransition at which the hydrate slurry first exhibits a measurable increase in resistance-to-flow at ≈(16 ± 2) vol %, clear changes in the measured number and size of the hydrate particles were observed. Initially, hydrate particles within the FBRM probe’s field of view decreased in size and increased in number until a maximum was reached at concentrations of 2–9 vol % (increasing with shear rate). However, with continued hydrate growth, the number of particles within the FBRM probe’s field of view unexpectedly decreased and eventually...

A water droplet size distribution dependent modeling of hydrate formation in water/oil emulsion

Experimental data on chord length distributions and growth rate during methane hydrate formation in water‐in‐oil emulsions were obtained in a high pressure stirring reactor using focused beam reflectance measurement and particle video microscope. The experiments were carried out at 274.2 K for 10–30% water cuts and agitation rates ranging from 200 to 500 rpm initially at 7.72 MPa. Rapid growth was accompanied by gradually decrease in rate. Free water was observed to become depleted during rapid growth while some water remained encapsulated inside hydrate layers constituting a mass transfer barrier. The apparent kinetic constants of methane hydrate formation and free‐water fractions were determined using a newly developed kinetic model independent of the dissolution rate at the gas–oil interface. It was illustrated that continued growth depends on distribution and transfer of water in oil‐dominated systems. This perception accords with observations of hydrate film growth on suspended water droplet in oil and clarifies transfer limits in kinetics. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1010–1023, 2017

The use of the organic–inorganic hybrid polymer Al(OH)3–polyacrylamide to flocculate particles in the cyanide tailing suspensions

The organic–inorganic hybrid polymer Al(OH)3–polyacrylamide (Al–PAM) was investigated in flocculation of particles in 10wt% cyanide tailing suspensions in this study. The effect of Al–PAM was evaluated with photoelectric turbidimeter, focused beam reflectance measurement (FBRM) and particle video microscope (PVM). It was found that as the amount of Al45–PAM with maximum zeta potential and molecular weight increased, the initial settling rate of particles increased, reaching the highest 11.7m/h, 18.5 times of the blank without flocculants. Correspondingly, the turbidity of the supernatant was 0.95 NTU, compared to 291.6 NTU in the blank, which was over 98% of turbidity removal efficiency. The cationic Al–PAM demonstrated better flocculation to the particles in the cyanide tailing suspensions than the commercial non-ionic guar gum (GG), and has potential for commercialization .The electrostatic repulsion between tailing particles was regarded as a critical parameter in determining polymer flocculation and our study indicated that both charge neutralization and bridge adsorption contributed to the particle flocculation.

The Growth and Development of Asphaltene Aggregates in Toluene Solution

The effect of asphaltene concentrations from 10 to 140 mg/L on particle diameter of aggregates is studied by multiple angle dynamic and static light scattering. The particle diameter of aggregates is increasing with the asphaltene concentration rising. The observed concentration for massive self-aggregation of asphaltene is about 80 mg/L. And the process of growth and development of asphaltene aggregates is studied by measurements of particle video microscopy (PVM) and focused beam reflectance measurement (FBRM) on asphaltene in toluene solution simultaneously. PVM and FBRM provide dynamic images and real-time statistical data of asphaltene aggregates in toluene solution, which can show that asphaltene aggregation is stronger and stronger with the asphaltene concentration increasing. Statistical data demonstrate that small particles are first massively formed in the range of less than 5 μm and 5–10 μm. Then small particles can interact to result in large particles which are in the range of 10–50 μm and 50–80 μm with asphaltene concentration increasing. The number of particles in the range of less than 50 μm is dominant in solution despite asphaltene concentration increasing.

Topological modeling of methane hydrate crystallization from low to high water cut emulsion systems

Hydrate formation and remediation in oil flowlines facilities represent a major concern for oil industry in respect of capital and operational costs. It is necessary to have a better understanding on the hydrate formation process to be more efficient in hydrate prevention, especially in respect to additive dosage. This work is a contribution to enhance the knowledge of hydrate formation at high water cuts, by introducing new techniques of analysis in the Archimede flow loop: a Focus Beam Reflectance Measurement (FBRM) probe and a Particle Video Microscope (PVM) probe. These results will be supported by Pressure Drop, Flow Rate, Density and Temperature probes. From experimental observations, a method to determine the continuous phase (water or oil) of the system under flowing is proposed. It is based on the time evolution of the most representative chord class measured by the FBRM. In order to predict morphology and size of hydrates, a topological model was developed. It represents hydrate crystallization from different emulsion systems with and without low dosage of hydrate inhibitor additive (anti-agglomerant type). The key parameters are the gas transfer rate at the gas/liquid interface and at the hydrocarbon/water interface, and the role of the hydrocarbon as gas transfer phase. Gas/liquid transfer is low as water phase remains the continuous phase, but is enhanced as hydrocarbon content is increased. Hydrocarbon gas transfer property is depleted as continuous and rigid crust is formed around droplets, especially in well dispersed emulsions. This behavior is highlighted for experiments without anti-agglomerant additive (AA-LDHI) and at high water cut, as a small fraction of hydrocarbon is well dispersed in the water continuous phase. The maximum hydrate plugging risk is in between 70% and 30% water cut (intermediate and low water cut). In this work, experiments at high water cuts (more than 80%) never plug. In order to prevent agglomeration, the AA-LDHI works better if it shows a secondary surfactant benefit, well-dispersing the droplets (and later the formed hydrates) in the continuous phase, which was identified as being preferentially the hydrocarbon phase.

Droplet Size Measurements in Oil–Water Dispersions: A Comparison Study Using FBRM and PVM

Droplets in oil–water dispersions are measured using two different measurement techniques. Both focused beam reflectance measurements (FBRM) and particle video microscopy (PVM) are applied simultaneously in order to obtain direct comparison. A real-time chord length distribution (CLD) is obtained from the FBRM. The picture series by the PVM are post-processed to obtain droplet size distributions (DSDs). By measuring particle samples, it was shown that PVM is able to detect the correct size distribution. Using the PVM images, the uncertainty of the CLD was quantified. Two empirical approaches to convert the CLD to the correct DSD are documented.

Droplet size distribution and droplet size correlation of chloroaluminate ionic liquid–heptane dispersion in a stirred vessel

Droplet size distribution (DSD) and mean droplet size of chloroaluminate ionic liquid (IL)–heptane dispersion in a stirred vessel were investigated as a model system for the composite ionic liquid/hydrocarbon system applied in the commercial isobutane alkylation process. Focused beam reflectance measurement was used to identify the phase inversion, and particle video microscope (PVM) was employed to measure the DSD of IL-continuous dispersions. The effects of agitation speed and dispersed phase holdup on the DSD and mean droplet size were investigated. Phase inversion was found at a heptane hold-up of just above 0.5. The observed DSDs could be described well by logarithmic normal distributions in spite of variable operating conditions. The DSDs appeared to be more or less independent of the dispersed phase holdup (ϕheptane⩾0.3) at the same agitation speed. A semi-empirical correlation based on Shinnar theory was proposed to predict the droplet mean size in the impeller region for the IL-continuous dispersion, and the predicted value agreed well with the experimental data. This work will be a good basis to predict the dispersion behavior under process conditions.

Evaluation of Gas Hydrate Anti-agglomerant Based on Laser Measurement

The feasibility of evaluating the performance of anti-agglomerants from analyzing the variation of morphologies and chord length of particles was examined using an autoclave installed with a particle video microscope and focused beam reflectance measurement probes. The experimental results from methane + water + diesel oil systems show that the agglomeration of hydrate can be judged directly from two laser probes. With the action of an effective anti-agglomerant, the size of droplets/hydrate particles is uniform and tends to that before hydrate formation when most water converts to hydrate or the system stops stirring for 9 h, although the agglomeration occurs when water droplets initially convert into hydrates. The evaluation method was examined under different anti-agglomerant concentrations, water cuts, and subcoolings for water + diesel oil systems. The action mechanism of anti-agglomerants was also proposed.

Insights into methane hydrate formation, agglomeration, and dissociation in water + diesel oil dispersed system

Methane hydrate formation and dissociation in (5vol% water+95vol% diesel oil) dispersed system containing a combined anti-agglomerant were experimentally studied using a high pressure autoclave installed with particle video microscope and focused beam reflectance measurement probes. The agglomeration of hydrate was found to occur at the initial hydrate formation stage. With the continuous formation of hydrate, the agglomeration of hydrate will be inhibited and hydrate was dispersed with the action of the anti-agglomerant. The agglomeration of hydrate also occurs when the hydrate containing fluid is under static state for a certain time. Larger hydrate particles attached by gas bubble with grape-like shape were found during hydrate dissociation. The dissociated surface water would contact with un-dissociated hydrate and accumulate to larger water/hydrate particles may be the reason that causes the agglomeration during initial hydrate dissociation process. A mechanism was proposed to describe hydrate dissociation from water in oil dispersed system.

Study on Gas Hydrate Formation and Hydrate Slurry Flow in a Multiphase Transportation System

As oil and/or gas exploration and production enter deeper water, the flow assurance confronts challenges, one of which is the hydrate formation and blockage. Investigations about gas hydrate formation and hydrate slurry flow in a multiphase transportation system were performed on a newly constructed high-pressure experimental loop. On the basis of the experimental hydrate formation data, an inward and outward hydrate shell model was improved to predict the gas consumed amount during the hydrate formation process. With the help of a focused beam reflectance measurement and particle video microscope installed in this flow loop, the distribution of hydrate particles was observed, characterized in the coalescence and fragmentation. A “minimum safety flow rate” was first addressed for the safety of hydrate slurry flow in a multiphase transportation system. Then, the comparisons between our experimental data of the natural gas hydrate slurry flow pattern and the Mandhane flow pattern map revealed the influence of hydrate particles on the flow pattern of the slurry. Furthermore, the influence of the gas/liquid superficial velocity on the pressure drop was discussed at stratified flow for this gas hydrate slurry multiphase system.

Memory Effect Test of Methane Hydrate in Water + Diesel Oil + Sorbitan Monolaurate Dispersed Systems

Formation and reformation of methane hydrate in (water + diesel oil + sorbitan monolaurate) dispersed systems have been investigated to test the memory effect using particle video microscope and focused beam reflectance measurement probes. The factors which would affect methane hydrate formation, the dosage of sorbitan monolaurate, water cut, and initial experimental temperature, were examined. The results show that there exists obvious memory effect when methane hydrate reformed in water/diesel oil dispersed systems at initial temperature near methane hydrate formation zone, even maintaining at the initial temperature for 168 h after methane hydrate dissociation. The subcooling will increase with prolonging of maintaining time, which suggesting that memory effect would disappear if time is long enough. When initial temperature increases to 5 K higher than the equilibrium value, the subcooling of reformation of methane hydrate is similar to that of hydrate first formation, which implying that memory effec...

Monitoring the Crystallization Process of Methylprednisolone Hemisuccinate (MPHS) from Ethanol Solution by Combined ATR-FTIR- FBRM- PVM

In-situ Attenuated total reflectance Fourier transform infrared (ATR-FTIR), focused beam reflectance measurement (FBRM) and particle video microscope (PVM) have been used simultaneously in this work to monitor the concentration, supersaturation, chord length distribution, and crystal habit, respectively, during a cooling crystallization process of Methyprednisolone Hemisuccinate (MPHS) from ethanol system. We developed a new calibration method based on peak ratios for the assessment of the concentration, solubility, and supersaturation in the 20–60°C temperature range. The crystallizations were conducted at two concentrations (7.5 and 9.5% w/w) with three different cooling rates (0.3, 0.5, and 0.7 K/min). The lower concentration was chosen within the constructed calibration range while the higher one was outside the calibration range and it was used to examine the extrapolating and predicting ability of the constructed calibration curves. The metastable zone widths (MSZW), supersaturation at nucleation, and the number of fine particle chord length of MPHS were all increased with the cooling rate, while the number of the larger chord length decreased with the increasing of the cooling rate.

Separation of ethylene from refinery dry gas via forming hydrate in w/o dispersion system

A so-called absorption–hydration hybrid method was adopted for recovering ethylene from refinery dry gas using water in diesel emulsion under hydrate formation conditions. Span 20 was used to disperse water or hydrate in diesel. Two (CH4+C2H4+N2+H2) quaternary feed gas mixtures were synthesized in order to simulate a two-stage separation of refinery dry gases. The influences of temperature, pressure, feed gas composition, initial gas–liquid volume ratio, and initial water cut in liquid on the separation efficiency were systematically investigated. A pseudo separation factor (S) was defined to evaluate the separation selectivity of ethylene over other components. The experimental results show that ethylene can be enriched in hydrate slurry phase with high selectivity and high recovery ratio. The operation pressure could be reduced remarkably by decreasing temperature to below the ice point. Both separation factor and recovery ratio of ethylene increase with the decrease of temperature; however, when temperature is decreased to 269.2K or so, the trend changes inversely. In order to reveal why S decreases with decreasing temperature at lower temperature range, in situ PVM (Particle Video Microscope) and FBRM (Focused Beam Reflectance Measurement) particle analyses were performed to investigate the variation law of the morphology of water/diesel dispersion system with temperature before and during hydrate formation. The experimental results show that the average ice particle size increases with decreasing temperature and leads to the decrease of the hydrate formation rate and the conversion ratio of water into hydrate.

Control of the agglomeration of crystals in the reactive crystallization of 5-(difluoromethoxy)-2-mercapto-1H-benzimidazole

5-(Difluoromethoxy)-2-mercapto-1H-benzimidazole (DMB) was precipitated by adding acetic acid to the DMB sodium salt solution. The spherical agglomeration of DMB during the reactive crystallization in a batch crystallizer was monitored by real-time Particle Video Microscope (PVM). We found that the low feeding rate of acetic acid, high crystallization temperature, low agitation rate or adding seed crystal can facilitate the formation of spherical agglomerates. By using a simple model, the mean crystal agglomerate size of DMB thus predicted is generally in agreement with the experimental data. In addition, the crystallization process of DMB was optimized by a new control strategy of supersaturation to avoid disadvantages brought by agglomeration.

Investigation of Batch Cooling Crystallization in a Liquid–Liquid Separating System by PAT

Crystallization of butyl paraben from water–ethanol mixtures has been investigated. The liquid–liquid phase separation and the solid–liquid solubility have been determined from 1 to 50 °C. Cooling crystallizations have been performed at different starting compositions, and the processes have been recorded by in-situ infrared spectroscopy, focused beam reflectance measurement, and particle video microscopy. In pure water the butyl paraben solubility is below 1 mg/g, while in pure ethanol the solubility is more than 3 orders of magnitude higher. While the solution saturated with butyl paraben is homogeneous at 1 °C, at the higher temperatures butyl paraben induces a liquid–liquid phase separation of the ethanol–water mixture, and the ternary phase diagram contains up to five different regions. The size of the liquid–liquid phase separation region increases with increasing temperature. At 50 °C, even the binary butyl paraben water system separates into two different liquid phases. In the cooling crystallizat...

Droplet Size Scaling of Water-in-Oil Emulsions under Turbulent Flow

The size of droplets in emulsions is important in many industrial, biological, and environmental systems, as it determines the stability, rheology, and area available in the emulsion for physical or chemical processes that occur at the interface. While the balance of fluid inertia and surface tension in determining droplet size under turbulent mixing in the inertial subrange has been well established, the classical scaling prediction by Shinnar half a century ago of the dependence of droplet size on the viscosity of the continuous phase in the viscous subrange has not been clearly validated in experiment. By employing extremely stable suspensions of highly viscous oils as the continuous phase and using a particle video microscope (PVM) probe and a focused beam reflectance method (FBRM) probe, we report measurements spanning 2 orders of magnitude in the continuous phase viscosity for the size of droplets in water-in-oil emulsions. The wide range in measurements allowed identification of a scaling regime of droplet size proportional to the inverse square root of the viscosity, consistent with the viscous subrange theory of Shinnar. A single curve for droplet size based on the Reynolds and Weber numbers is shown to accurately predict droplet size for a range of shear rates, mixing geometries, interfacial tensions, and viscosities. Viscous subrange control of droplet size is shown to be important for high viscous shear stresses, i.e., very high shear rates, as is desirable or found in many industrial or natural processes, or very high viscosities, as is the case in the present study.

Monitoring of Antisolvent Crystallization of Sodium Scutellarein by Combined FBRM–PVM–NIR

Antisolvent crystallization can be used as an alternative to cooling or evaporation for the separation and purification of solid product in the pharmaceutical industry. To improve the process understanding of antisolvent crystallization, the use of in-line tools is vital. In this study, the process analytical technology (PAT) tools including focused beam reflectance measurement (FBRM), particle video microscope (PVM), and near-infrared spectroscopy (NIRS) were utilized to monitor antisolvent crystallization of sodium scutellarein. FBRM was used to monitor chord count and chord length distribution of sodium scutellarein particles in the crystallizer, and PVM, as an in-line video camera, provided pictures imaging particle shape and dimension. In addition, a quantitative model of PLS was established by in-line NIRS to detect the concentration of sodium scutellarein in the solvent and good calibration statistics were obtained (r(2) = 0.976) with the residual predictive deviation value of 11.3. The discussion over sensitivities, strengths, and weaknesses of the PAT tools may be helpful in selection of suitable PAT techniques. These in-line techniques eliminate the need for sample preparation and offer a time-saving approach to understand and monitor antisolvent crystallization process.

Measurement and Calibration of Droplet Size Distributions in Water-in-Oil Emulsions by Particle Video Microscope and a Focused Beam Reflectance Method

Water droplet sizes in crude oil emulsions were measured using an in situ particle video microscope (PVM) probe and a focused beam reflectance measurement (FBRM) probe for a variety of oils spanning over two orders of magnitude in viscosity and for varying shear rates. The arithmetic or Sauter mean diameter was found to maintain the same constants of proportionality with the maximum (99th percentile) droplet size for different distributions, previously only shown for water-continuous emulsions. The FBRM values for the mean droplet size, while lower than the PVM values, could be related to the latter by an empirical quadratic relationship with an average error of less than 20%. The droplet size distribution was found to be represented well by a log-normal distribution with good agreement between correlated and measured mean droplet size. Following the agreement between the mean and maximum droplet sizes, the log-normal standard deviation was linearly related to the mean droplet size. The PVM probe was foun...