Viscous Slurries Research Articles

High pressure rheological measurements of gas hydrate-in-oil slurries

Gas hydrates are ice-like solids that may form in crude oil flowlines under high pressure and at low temperature, resulting in the formation of viscous hydrate-laden oil slurries. The magnitude of the slurry viscosity has been suggested as a primary means of determining the risk and severity of flow blockage, but there is a dearth of data available to calibrate predictive models of hydrate-in-oil slurry viscosity. This work deploys a controlled-stress, high-pressure rheometer to characterize the rheological properties of methane hydrate-in-crude oil slurries, which were generated in situ from water-in-oil emulsions. A vane blade rotor was found to maintain sufficient methane saturation in the oil phase during the hydrate growth period to allow near full conversion of the water. Dynamic measurements with the rheometer were able to separate the contributions to the viscosity change as the emulsion converted to a hydrate slurry due to (i) formation of the solid particles and (ii) reduction of the methane content in the oil continuous phase. For 5–30 vol% watercut systems, the slurry viscosity increased between 20 and 60 times during hydrate growth, whereas, under equivalent conditions for a 20% watercut emulsion, the viscosity increase due to the desaturation of methane from the oil phase was less than a factor of two. The steady-state hydrate-in-oil slurry demonstrated shear thinning behavior at both 1 and 5° C. The measured slurry relative viscosity deviated between 12 and 212% from the current industry-standard hydrate-in-oil slurry viscosity model, indicating the need for model improvement. After an eight-hour annealing period to simulate subsea shut-in, the yield stress of the hydrate-in-oil slurries varied between 3 and 25 Pa over 5 to 25 vol% hydrate.

Physical, cooking and thermal properties of African rice (Oryza glaberrima) and its starch digestibility in vitro

Rice is a staple food worldwide. In this study, seven African rice (Oryza glaberrima) accessions (ARAs) were evaluated for grain quality attributes, pasting, thermal and in vitro digestion properties in comparison with two Asian rice (Oryza sativa) varieties (ARVs) and a developed cross (O. sativa × O. glaberrima cross). The ARAs were intermediate to high amylose rice types and their 1000-kernel weight and bulk densities were comparable to the ARVs. Volume expansion ratios of cooked kernels overlapped among rice varieties ranging from 2.5 to 4.4 and the ARAs had relatively lower cooking solids loss and harder texture compared to the ARVs which were softer and more adhesive. Flours from the ARVs formed more viscous slurries, exhibiting higher breakdown viscosities than the ARAs. Gelatinization transition temperatures and enthalpies were significantly higher for flours from ARAs than the ARVs suggesting more stable crystal structure for ARAs. This is supported by the higher energy required to liquefy the retrograded ARAs flour gels. The cooked samples of ARAs and ARVs showed close starch digestibility indices with expected glycemic index (eGI) ranging from 71 to 78. Differences observed in cooking characteristics and textural properties between ARAs and ARVs may be partially due to the ARAs’ high amylose content.

A Randomized Controlled Comparison of Esophageal Clearance Times of Oral Budesonide Preparations.

Topical steroids prepared as oral viscous slurries have become common in the treatment of eosinophilic esophagitis. Esophageal mucosal contact time correlates with clinical and histologic improvement. To compare the mucosal contact time of alternative oral viscous budesonide (OVB) slurries with the conventional sucralose OVB. A blinded randomized crossover trial investigating esophageal clearance of three OVB slurry preparations was done on healthy adults. Honey and xanthan gum OVB slurries were compared with standard sucralose OVB in 24 randomly assigned subjects. Each subject ingested the sucralose OVB and either the honey or xanthan gum OVB slurries. The esophageal clearance of each slurry was evaluated as an area under the curve (AUC) using 1 millicurie of technetium-99m-sulfur colloid (Tc99) co-administered in each OVB preparation using nuclear scintigraphy. A standardized taste survey was also administered. Xanthan gum had greater mucosal contact time compared to sucralose as measured by a higher AUC at 3min (P=0.002), while honey showed no significant difference in esophageal clearance relative to sucralose. Taste scores were significantly higher in the honey group, while scores for xanthan gum were no different from standard sucralose. OVB slurries utilizing xanthan gum may be a superior alternative to a sucralose-based slurry due to its increased mucosal contact time and similar taste tolerance. Honey may be a suitable alternative as well, due to its similar contact time and favorable taste.

Gas migration regimes and outgassing in particle-rich suspensions

Understanding how gases escape from particle-rich suspensions has important applications in nature and industry. Motivated by applications such as outgassing of crystal-rich magmas, we map gas migration patterns in experiments where we vary (1) particle fractions and liquid viscosity (10 Pa s – 500 Pa s), (2) container shape (horizontal parallel plates and upright cylinders), and (3) methods of bubble generation (single bubble injections, and multiple bubble generation with chemical reactions). We identify two successive changes in gas migration behavior that are determined by the normalized particle fraction (relative to random close packing), and are insensitive to liquid viscosity, bubble growth rate or container shape within the explored ranges. The first occurs at the random loose packing, when gas bubbles begin to deform; the second occurs near the random close packing, and is characterized by gas migration in a fracture-like manner. We suggest that changes in gas migration behavior are caused by dilation of the granular network, which locally resists bubble growth. The resulting bubble deformation increases the likelihood of bubble coalescence, and promotes the development of permeable pathways at low porosities. This behavior may explain the efficient loss of volatiles from viscous slurries such as crystal-rich magmas.

Construction and Commissioning of a Continuous Reactor for Hydrothermal Liquefaction

The purpose of this paper is to give a comprehensive description of the construction and commissioning of a continuous reactor system for hydrothermal liquefaction of biomass. The basis is a newly established facility at Aarhus University. It is capable of handling viscous biomass slurries and features a novel induction-based heating method that facilitates well-defined reaction environments. Carbon balance closure is obtained as all product fractions are recovered and positively quantified. The paper includes a residence time distribution measurement and a 24 h proof-of-concept experiment conducted at 350 °C, 250 bar, and 15 min reaction time. It is based on the biomass dried distillers grains with solubles, a waste product of the bioethanol industry. The experiment seeks to determine the steady-state characteristics of the continuous reactor system for use in future experimental studies. It was found that steady state occurs within 6 h. Furthermore, data sampling windows of 2.1 h were found to mask the ...

Mixing analysis of PCS slurries in a horizontal scraped surface bioreactor.

Horizontal rotating reactors offer many advantages for enzymatic hydrolysis of viscous biomass slurries; however, they do not provide homogenous mixtures since motion is only in the angular direction. Multi-directional mixing is important for dispersing enzymes and carrying products away from reaction sites. The objective here was to experimentally quantify mixing times and axial dispersion coefficients in a horizontal rotating bioreactor. Mixing times were of the same order as reaction times, indicating that enzymatic hydrolysis could be as much controlled by diffusion and mixing effects as by the complex reaction mechanism. The dispersion coefficient for the highest solids slurry was 20× less than the lowest solids slurry, which is indicative of the difference in free water and the magnitude change of viscosity with relatively small addition of solids. The slow mixing times and low dispersion may be an acceptable tradeoff with significantly lower power requirements compared to a conventional vertical reactor.

Influence of fluorite on the isothermal leaching and rheological behaviours of chlorite mineral pulps at low pH

Chlorite clay gangue mineral leaching at low pH may produce viscous slurries, which deleteriously impact on value metal extraction and recovery in metallurgical plant operations. The presence of fluorite as a minor or an accessory mineral phase with chlorite may markedly exacerbate the pulp rheology and reduce the leaching dramatically. In the present work, isothermal leaching and rheological behaviours of chlorite were investigated in the presence of fluorite (chlorite/fluorite mass ratios of 20, 10 and 5 to 1) at pH1 and 70°C. Fluorite was found to dramatically enhance the kinetics of chlorite leaching, the mechanism of which was incongruent. The leach dispersion rheology showed a distinctly non-Newtonian behaviour characterized by thixotropy, shear thinning and time and fluorite concentration-dependent shear yield stress. The highest, maximum shear yield stress and apparent viscosities were observed at chlorite/fluorite ratio of 10:1, below and above which weaker gels formed. Solution-state 27Al and 29Si NMR studies indicated that polycondensation reactions involving solution Al(III) six to four fold coordination and a plethora of Si(IV) tetrahedra complexes led to the formation of aluminosilicate gels. The chlorite/fluorite ratio had a striking impact on the formation and development of the strongly viscous gel structures. The findings suggest that the resulting maximum yield stresses (40–200Pa) and apparent viscosity (10–25Pa·s) are highly detrimental to plant chlorite clay–fluorite rich, low grade laterite ores' leaching and handling operations.

Influence of Solid Concentration on the Flow Characteristics and Settling Rate of Coal-Water Slurries

Coal–water slurries were prepared with a sub-bituminous coal at varying coal and water ratios using an anionic liquid soap as a surfactant. The slurry properties, viscosity and stability were determined. The rheological properties of the slurries were investigated to ascertain the characteristics of the slurries. The results showed that increasing coal (solid) concentration increased the density of the slurries. Higher density gave rise to more viscous slurries. The behaviour of the slurries changed from Newtonian to non-Newtonian at higher solid concentrations. The slurries with lower solid concentration settled faster than the higher solid concentration slurries.

Application of dispenser printing for the preparation of a SOFC cathode with controlled microstructure

Abstract The fabrication of a cathode layer of solid oxide fuel cells by the dispenser printing was investigated and found to be useful in the creation of a thicker ceramic layer using viscous ceramic slurries. The cathode layer prepared from a mixture of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ (LSCF) and Ce 0.9 Gd 0.1 O 1.95 (GDC) slurry clearly shows an inhomogeneous microstructure which leads to poor cell performance. In order to solve this problem, the size of the LSCF particles was controlled through a milling process. Better cell performance was observed for the cells with controlled microstructure by adjusting the pore former content, the LSCF/GDC ratio, in addition to the particle size control. This process might be useful in the deposition of a thick ceramic layer on a curved substrate such as micro-tubular cell.

MID-PALEOZOIC TRILOBITE LAGERSTATTEN: MODELS OF DIAGENETICALLY ENHANCED OBRUTION DEPOSITS

Spectacular trilobite Lagerstatten occur in distinctive offshore calcareous mudstone facies through the Late Ordovician to Devonian, and reflect a combination of mass mortality or molting and burial, coupled with early diagenetic enhancement. Evidence indicates two distinct modes of burial, Type I and II assemblages, which show evidence for burial without or with seafloor disturbance, respectively. Type I assemblages suggest rapid (hours to days), but not instantaneous burial, without bottom disruption, enabling preservation of in situ behavior, including mass aggregations and molt ensembles. Most occurrences contain bedding planes in which trilobites exhibit incipient disarticulation. These assemblages were buried by cascades of flocculated sediment from hypopycnal, detached flows. Type II assemblages show well-articulated, enrolled, semi-enrolled, and outstretched trilobites in varied orientations relative to bedding. In such cases, bottom flows and seafloor disruption by storm or seismic disturbances in shallow waters suspended large amounts of flocculated muds as viscous slurries, which developed into hyperpycnal flows that entrained carcasses of trilobites and other organisms. In many cases, both Type I and II obrution was followed by additional sedimentation, geochemical zones moved upward through the sediment column, and there was little tendency to form diagenetic overprints. Alternatively, if burial was followed by an interval of sediment starvation, the sediments were bioturbated and very early diagenetic mineralization was superimposed, first, in rare cases, as mineralized soft parts in entombed carcasses, and later as pyritization of burrow linings. Development of the concretionary layers required more prolonged periods of stability of the sulfate reduction zone. Cementation of sediment shielded organism bodies from most or all effects of compaction. Thus, ironically, the best preservation of delicate remains required rapid burial, associated with mass mortality, and very low rates of background sedimentation following the event.

Pipeline transport of high density slurries: a historical review of past mistakes, lessons learned and current technologies

There is a great deal of misinformation in the industry on pumping high density, viscous slurries. These misconceptions become ‘accepted truths’ as time goes on which, at best hinder, and at worst, stop the implementation of appropriate technology. Unfortunately, the root of these misconceptions is often due to negative experiences gained on poorly understood, poorly designed or poorly implemented systems. Advances in a technology can only be realised by accepting that the mistakes of the past can be rectified and learned from. Unfortunately, this does not readily happen in an industry that is resistant to change. The objective of this paper is to address these issues by tracing the historical development of high density pumping and why the problems of the past are not necessarily the same problems that we experience today. It is accepted that many of the fundamental problems cannot be resolved and continued improvements in ore processing will mean that new challenges will arise. However, there is a better understanding of how to deal with the issues practically, by using the latest developments in pump and pipeline technology.

Predicting effective viscosity of magnetite ore slurries by using artificial neural network

In this paper, we study the theoretical models for effect of various parameters used for predicting viscosity of magnetite ore slurry. These models are fitted using data collected from experiments conducted. These viscous slurries of magnetite ore have up to 30% solids (by weight). We prepared the slurry samples of magnetite in aqueous solutions of high viscosity powder of sodium salt of carboxy methyl cellulose (CMC) and guar gum. Average particle sizes of the four solid samples used were of 50, 52.3, 58.4 and 74.8μm. The viscosity of slurry samples was measured using Brookfield DV-III+programmable rheometer. Once the experimental data was collected, we selected six different models for predicting viscosity; also we used artificial neural networks (ANN) for fitting the experimental data, and, trained the neural networks to predict viscosity for unknown samples. We have finally computed the root mean square errors (RMSE) between model predictions and corresponding measured value of viscosity. The conclusions drawn and certain observations made are reported.

α‐Alumina Fiber with Platelet Morphology Through Wet Spinning

Highly loaded Al(OH)3 slurries were prepared in a 2 vol% aqueous acetic acid medium up to 33.3 wt% powder loading. The slurries were blended with 4 wt% chitosan in 2 vol% acetic acid and formed into ceramic fibers through wet spinning in sodium tripolyphosphate (STPP) bath. A gelation kinetics study of the chitosan‐blended slurry also showed instantaneous gelation behavior under oscillatory mode rheological measurement. The slurries with moderate viscosities up to 150 Pa·s were spinnable in STPP bath due to ionotropic gelation. Low viscous slurries were formed into a lump during spinning due to low powder loading and less chitosan present in the blend. The green fibers crystallized into α‐alumina during sintering at ~950°C with an average diameter varying between 70 and 120 μm. α‐alumina platelets were formed at 1350°C and changed to hexagonal platelets at 1550°C. The crystallite size of α‐alumina varied between 26 and 112 nm which was measured from XRD data using Scherrer formula. The grain size of sintered fibers was ~4.5 μm at 1350°C. The fibers were assembled into a cylindrical scaffold and sintered to produce a crushing strength of 0.9 MPa with density 0.9 g/cm3.

Flour Mill Stream Blending Affects Sugar Snap Cookie and Japanese Sponge Cake Quality and Oxidative Cross‐Linking Potential of Soft White Wheat

The purpose of this research was to study the functional differences between straight grade (75% extraction rate) and patent (60% extraction rate) flour blends from 28 genetically pure soft white and club wheat grain lots, as evidenced by variation in sugar snap cookie and Japanese sponge cake quality. Functional differences were examined relative to arabinoxylan content, protein content, and oxidative cross-linking potential of flour slurries. Oxidative cross-linking measurements were obtained on flour slurries with a low shear Bostwick consistometer and considered endogenous oxidative cross-linking potential (water alone) or enhanced oxidative cross-linking potential (with added hydrogen peroxide-peroxidase). A 2-way ANOVA indicated that flour blend was the greater source of variation compared to grain lot for all response variables except water-extractable arabinoxylan content. Patent flours produced larger sugar snap cookies and Japanese sponge cakes, and contained significantly less total and water-unextractable arabinoxylans, protein, and ash than did straight grade flours. Patent flours produced more viscous slurries for endogenous and enhanced cross-linking measurements compared to the straight grade flours. The functional differences between patent and straight grade flours appear to be related to the particular mill streams that were utilized in the formulation of the 2 flour blends and compositional differences among those streams.

Endogenous and Enhanced Oxidative Cross‐Linking in Wheat Flour Mill Streams

ABSTRACTA better understanding of the variation in oxidative cross‐linking potential among flour mill streams can improve flour quality through the formulating of superior flour blends, and hence end‐product attributes. The purpose of this research was to study the variation of oxidative cross‐linking among 10 Miag Multomat pilot mill streams from 31 hard, soft and club wheat cultivars using Bostwick viscosity measurements. Flour slurries were made with either water alone (to measure the endogenous oxidative cross‐linking viscosity) or with added hydrogen peroxide‐peroxidase (to measure the enhanced oxidative cross‐linking viscosity). Hard cultivars tended to produce more viscous flour slurries for both water and peroxide‐peroxidase viscosity measurements in most mill streams. Mill streams with high oxidative cross‐linking potential were those with the largest differences between water and peroxide‐peroxidase viscosity including 1st Break, 1st and 2nd Middlings, and 1st Midds Redust. Conversely, mill streams 3rd Break and 4th and 5th Middlings were the least likely to form oxidative cross‐links. The ability to form oxidative cross‐links is dependent on the availability of ferulic acid and tyrosine residues. Therefore, the arabinoxylan and protein polymers in mill streams that have a high oxidative cross‐linking potential have a structure that is more conducive to forming oxidative cross‐links.

Multifunctional PMMA-Ceramic composites as structural dielectrics

We describe the influence of calcium copper titanate (CCTO), and montmorillonite (MMT) on the thermo-mechanical and dielectric properties of poly(methyl methacrylate) PMMA-based composites prepared by an in-situ, thermally activated, radical polymerization for multifunctional structural capacitor applications. MMT was used for its ability to disperse and suspend the CCTO particles through the generation of viscous monomer slurries. X-ray diffraction (XRD) measurements together with transmission electron microscopy (TEM) analysis revealed that the MMT platelets were present in both intercalated and exfoliated morphologies within the polymer matrix. The filler addition was found to improve the thermal stability and the glass transition temperature of PMMA in the composites. Furthermore, the elastic stiffness and dielectric constant of the resultant composites were observed to increase monotonically with filler loading. By contrast, the dielectric breakdown strength of the composite samples was found to diminish with increasing filler loading.

Rheological behaviour of lateritic smectite ore slurries

The characterisation and rheology of several nickel laterite smectite ores and pure minerals are compared to assess the effect of mineralogy and particle size on the viscosity of high pulp density slurries. A vane viscometer was used to determine the “optimum pulp density” (OPD) that gave a yield stress of 100 Pa which is considered to be optimal for pumping slurries into autoclaves in the HPAL process. In general, slurries containing finer particles were more viscous and smectite slurries exhibited poor rheological behaviour as compared to slurries of goethite < kaolin < talc < hematite < maghemite < magnesite. Blending the smectite ores with a fraction of the pure minerals improved the rheological behaviour of the pulp and can increase the optimum pulp density of the smectite blend by over 5% w/w. When the physical properties of the smectite ore and slurry were examined, a very good linear correlation was obtained between the optimum pulp density and the settling density which provides a simple measure of predicting rheological behaviour of slurries. The variation in the viscosity of the nickel laterite ores depends largely on their mineralogy and particle size distribution. The mean particle size and P 80 values of various smectite ores containing the same mineral phases were also found to have a reasonably good linear correlation with OPD in saline water, but the correlation of ore surface area with OPD was a poorer fit.

Salt/ligand-activated low-valent titanium formulations: the ‘salt effect’ on diastereoselective carbon–carbon bond forming SET reactions

A comprehensive study on the influence of exogenously added electropositive metal salts as promoters/secondary activators on preformed LVT species has resulted in the construction of highly efficient low-valent titanium (LVT) reagents. These salt-activated LVT reagents while exhibiting enhanced chemoselectivity and diastereoselectivity accelerated the reductive olefination rates of aromatic and aliphatic carbonyls under ambient temperature conditions and in much reduced reaction times. The versatility of the salted reagent was further explored in other single electron transfer reactions, namely, imino-pinacol couplings and one-pot synthesis of phenanthrenes from o-alkoxy aromatic carbonyls. We envisage that, in contrast to multiphase heterogeneous colloidal slurries, salt-activated LVT reagents afforded uniformly viscous homogeneous slurries generating a highly reactive monomeric intermetallic LVT complex. Continued judicious exploration of the emerging paradigms by studying the influence of external ligands/auxiliaries/redox agents on LVT reagents, and organometallics in general, will be critical to widen the scope and utility of the classical McMurry reaction and other SET reactions.

A new experimental facility for laboratory debris flow investigation

For debris flow hazard assessment often simple rheologic models are used in engineering practice. A vertically rotating drum has been constructed to study the flow behaviour of debris flow material in a laboratory environment. We provide a detailed description of the experimental setup, which allows generating and observing stationary surges of materials ranging from viscous slurries to granular flows for an extended time period. Results of tests with a homogeneous transparent liquid polymer (Carbopol Ultrez10®) are presented and discussed. Two simple methods are outlined which allow the flow parameters for a Bingham model to be estimated

Fabrication of Fiber‐Reinforced Ceramic Composites by the Modified Slurry Infiltration Technique

A new technique for the homogeneous infiltration of concentrated and viscous ceramic filler slurries into stacked 2D‐woven fabrics has been developed by introducing a flexible mold. The inner space of the mold expanded during slurry infiltration, which enhanced penetration of the viscous slurry into the woven fabric layers. The subsequent precursor impregnation and pyrolysis process yielded fiber‐reinforced ceramic composites with scarce macropores between the fabric layers.