Low Slurry Concentration Research Articles

Rheology of fibre suspension flows in the pipeline hydro-transport of biomass feedstock

In the hydro-transport of biomass feedstock by pipeline to bio-refineries, the rheology of the biomass slurry directly impacts the specifications and, therefore the cost of pipeline components. In this study, the rheological characteristics of untreated fine wood chip slurries across a broad range of slurry temperatures (5–15 °C) and solids concentrations (3–15 wt% dry-matter) were experimentally studied. Slurry samples were pumped in a closed-circuit pipeline facility where slurry flow longitudinal pressure drops were simultaneously measured. The rheological characteristics of the samples were then measured using a rotational viscometer with a vane-in-cup geometry. At low slurry concentrations (˂6 wt% dry-matter), the biomass slurry exhibited Newtonian behaviour; however, non-Newtonian (shear-thinning) behaviour was seen at higher slurry concentrations. In order to approximate the corresponding rheological parameters, different well-known non-Newtonian viscosity models (power-law, Bingham, Casson, and Herschel-Bulkley) were applied to experimental data. In addition, a new approach for approximating the apparent viscosity of biomass slurries using longitudinal pressure drop measurements was introduced and validated. The method has not been previously applied to non-Newtonian biomass slurries under turbulent flow regimes. • Rheological characteristics of untreated wood chip biomass slurries were studied. • Biomass slurry samples were made off a closed-circuit pipeline facility. • Rotational viscometer with vane-in-cup geometry was used over range of temperatures. • Corresponding rheological parameters were approximated using well-known models. • A pressure drop-based method proposed to approximate viscosity of slurry flows.

Analytical and experimental investigation of the relationship between spread and yield stress in the mini-cone test for cemented tailings backfill

The slump test is used to characterize the flow properties of mine backfill. However, the slump is not as easy to measure as spread in the condition of high or low slurry concentration. Models relating the spread length to yield stress in mini-cone test is not well developed. Rheological tests are also often used to determine the yield stress and dynamic viscosity of mine backfill materials. But the rheological test is expensive and not practical in the mine site. This paper evaluates the relationship between spread and yield stress by analytical derivation and experimental tests. Mini-cone tests and rheological tests were performed on 146 cemented tailings backfill (CTB) samples from nine Chinese mines and one Indonesian mine. A significant exponential relationship was found between the spread value and yield stress. An empirical formula between spread and yield stress was proposed and validated by the experimental results. The analytical formula is suitable for CPB with a yield stress of 115–385 Pa, and the empirical formula is suitable for CPB with a yield stress of 2–115 Pa. Using these two formulas, the yield stress can be calculated easily and directly by the spread value in engineering.

Dynamic Undrained Shear Strength Behavior of Bentonite–Grouted Sand

In this paper the results of dynamic and static triaxial tests on uniformed graded sand of Firoozkooh (131) has been tested and examined, which has been injected by bentonite slurry in different concentrations. The bentonite slurry inside the soil texture, can lead to changes the mechanic and hydraulic properties of soil. The results show that the bentonite being in sand leads to increase the liquefaction resistance. It was seen that when the slurry concentration is less than 7.5% it cannot have a significant impact on the liquefaction resistance, but by increasing the concentration of the slurry to 10%, liquefaction resistance increase effectively. The severity of liquefaction resistance changes for samples with low slurry concentrations was slow, and with increasing of slurry concentration was drastic. In addition it was observed that with increasing the concentration of slurry, the maximum dynamic modulus of elasticity increases. Due to obtained results, the soil liquefaction resistance through time and due to thixotropic process of bentonite, increases faster but after a specified period of time the rate of increase was slower. The static triaxial tests on injected bentonite samples were also compatible with dynamic testing results.

Competition of Oxygen Evolution and Desulfurization for Bauxite Electrolysis

To understand the relationship between oxygen evolution and desulfurization for bauxite electrolysis, the apparent activation energy of the anode reaction was examined by analyzing the polarization curves. The results showed that the apparent activation energy of the anode reaction for bauxite electrolysis with a low slurry concentration was lower than that of water electrolysis, indicating that the bauxite particles had some microcell disturbance effects on liquid diffusion. As expected, it was also lower than that of bauxite electrolysis with a high slurry concentration, indicating that the bauxite particles had some inhibition effects on oxygen evolution. Compared with adding bauxite, the increase in stirring speed did not change the concentration polarization of water electrolysis, indicating that the microcell disturbance effect of the bauxite particles was more important. Compared with the low slurry concentration electrolysis, the high slurry concentration electrolysis resulted in a low desulfuriza...

Bed morphological features associated with an optimal slurry concentration for reproducible preparation of efficient capillary ultrahigh pressure liquid chromatography columns

Column wall effects and the formation of larger voids in the bed during column packing are factors limiting the achievement of highly efficient columns. Systematic variation of packing conditions, combined with three-dimensional bed reconstruction and detailed morphological analysis of column beds, provide valuable insights into the packing process. Here, we study a set of sixteen 75μm i.d. fused-silica capillary columns packed with 1.9μm, C18-modified, bridged-ethyl hybrid silica particles slurried in acetone to concentrations ranging from 5 to 200mg/mL. Bed reconstructions for three of these columns (representing low, optimal, and high slurry concentrations), based on confocal laser scanning microscopy, reveal morphological features associated with the implemented slurry concentration, that lead to differences in column efficiency. At a low slurry concentration, the bed microstructure includes systematic radial heterogeneities such as particle size-segregation and local deviations from bulk packing density near the wall. These effects are suppressed (or at least reduced) with higher slurry concentrations. Concomitantly, larger voids (relative to the mean particle diameter) begin to form in the packing and increase in size and number with the slurry concentration. The most efficient columns are packed at slurry concentrations that balance these counteracting effects. Videos are taken at low and high slurry concentration to elucidate the bed formation process. At low slurry concentrations, particles arrive and settle individually, allowing for rearrangements. At high slurry concentrations, they arrive and pack as large patches (reflecting particle aggregation in the slurry). These processes are discussed with respect to column packing, chromatographic performance, and bed microstructure to help reinforce general trends previously described. Conclusions based on this comprehensive analysis guide us towards further improvement of the packing process.

Effects of load filling, slurry concentration and feed flowrate on the attainable region path of an open milling circuit

In this paper, the concept of conversion used in reaction engineering is applied to ball milling. The motivation is to assess the ability of a mill to produce optimally and efficiently a narrowly-sized product.To this end, a sampling campaign was initiated on a full-scale mill in open circuit. Data pertaining to the residence time distribution was collected for a range of ball filling, slurry concentration and feed flow-rate. Feed and product size distributions were also measured.After data processing, a model of the milling circuit was developed to allow for material transport and size reduction. Then, simulations were undertaken in order to determine the mill conversion of a feed material less than 850μm into particles in the range −75+10μm, termed in this work middlings.Based on the exploratory work, it was found that the middlings could be produced selectively at high ball filling and low slurry concentration. And perhaps the most important point to make is that the attainable region technique can find applications in cases where milling needs to be done under size constraints dictated by the downstream operation.

Analysis of heat recovery from a spray dryer by recirculation of exhaust air

Model simulations were employed to investigate the influences of process parameters on the energy recovery in spray drying process that partially recycle the exhaust drying gas. The energy efficiency and energy saving were studied for various values of recirculation ratios with respect to the temperature and flow rate of the drying air, slurry feed rate and concentration of slurry in spray drying of advanced ceramic materials. As a result, significant gains in energy efficiency and energy saving were obtained for a spray drying system with high recirculation ratio of exhaust air. The high slurry feed rate and the low slurry concentration, inlet drying air temperature and drying air flow rate enhanced the energy efficiency of spray drying system. However, the high energy saving was obtained in spray dryers operating at low slurry feed rate and high slurry concentration.

Slurry concentration effects on the bed morphology and separation efficiency of capillaries packed with sub-2 μm particles

Transcolumn dispersion limitations on the separation efficiency of chromatographic columns suggest the need for packing methods that increase bed homogeneity and minimize potential wall effects. Here we address the influence of the slurry concentration in the slurry packing process on the resulting morphology and separation efficiency of ultrahigh-pressure liquid chromatography capillary columns. 30–75μm i.d. capillaries were packed with fully porous 0.9, 1.7, and 1.9μm bridged-ethyl hybrid particles and 1.9μm Kinetex core–shell particles. Capillaries prepared with higher slurry concentrations (20–100mg/mL) showed higher separation efficiencies than those prepared using a low slurry concentration (2–3mg/mL). The effect is explained by an analysis of transcolumn bed heterogeneities in three-dimensional reconstructions acquired from the packed capillaries using confocal laser scanning microscopy. The three-dimensional analysis of porosity distributions and local particle size illustrates that beds packed with higher slurry concentrations suppress particle size segregation, however, at the expense of a larger amount of packing voids. In core–shell packings, where only few packing voids were found, the higher slurry concentration allowed for an additional densification of the bed's wall region, as revealed by a radial analysis of the mean particle distances. Overall, wall effects are attenuated in packed columns prepared with both wide and narrow particle size distributions, which will allow for improved chromatographic performance.

New evaluation method for the kinetic analysis of the grinding rate constant via the uniformity of particle size distribution during a grinding process

A new kinetic analytical method for evaluating the grinding rate constant via the uniformity of the particle size distribution during a grinding process was investigated. The grinding experiments were carried out at various slurry concentrations. A stirring ball mill was used. The relationship between the uniformity of the particle size distribution and the uniformity grinding rate constant K was evaluated. The value of K decreased with the increase in the uniformity of the ground sample, and varied with the experimental conditions. The value of K, which is related to the uniformity of the raw sample, increased at low slurry concentrations.

Gas Holdup Characteristics in a Tapered Bubble Column

Gas holdup characteristics were explored experimentally in a tapered bubble column of 3.00m height. The internal diameter increased from 0.10 m at the bottom to 0.20 m at the top. Two gas holdup characteristic parameters investigated were local gas holdup and overall gas holdup. Local gas holdup was measured by pressure drop method whilst overall gas holdup was measured by both pressure drop and bed expansion techniques. Axial gas holdup profile decreased from the bottom to the top in the range of the experiments. Overall gas holdup reached a maximum in transitional regime for either the gas-liquid system or the gas-liquid-solid system with low slurry concentration, but increased monotonically for gas-liquid-solid system with high slurry concentration. Overall gas holdup decreased with increasing static slurry height or solid concentration. The effect of particle diameter on gas holdup was too insignificant to be considered. Experiments were carried out in a cylindrical column to compare the difference between cylindrical and tapered bubble columns. Moreover, an empirical correlation was presented to estimate overall gas holdup in the tapered slurry bubble column (TSBC).

A Practical and Economical Fracturing Solution For Low Permeability Shallow Reservoirs

Abstract Fluid cost saving is critical for fracturing operations in low permeability reservoirs where the production revenues are low but the job size is relatively large and the fluid cost is high. Cross-linked fluids (CLF) are usually the first option. However, they may cause significant damage to both propped fractures and formations, and are not the cheapest option. Polymer-free fluids, on the other hand, cause much less damage but they are expensive and fluid costs may impair the economic results of fracturing. Waterfrac would be a compromise solution for low permeability reservoirs since its fluids are cheap and fluid damage is low. The success of waterfrac with low slurry concentrations is, however, difficult to predict. This paper presents a new fluid system that was formulated to maximize the economic return of fracturing wells in low permeability shallow oil reservoirs. It is a solid-free, linear, synthetic polymer-based system with a very low formation damage characteristic. The new fluid system can meet a variety of fracturing requirements, including slurry concentrations of conventional field levels. Moreover, it is much cheaper than cross-linked guar gel (CLGG). The method for designing fluid components and the procedure for preparing the fluid to achieve minimum formation damage and minimize the cost are described. A comparison of the production performances from the same well or adjacent reference wells fractured with the new fluids and CLGG is made. The reservoir geology, fluid type, and operation data of fracturing, and well performances from more than 300 successful wells in three different low permeability shallow oil reservoirs (800 ∼ 1,500 m depth) are also presented in detail. Introduction Hydraulic fracturing is a necessary technique to develop low permeability reservoirs. Fracturing fluid takes a paramount role in fracturing treatments. In most cases, cross-linked fluids (CLF) can meet the treatment requirements. However, severe formation damage frequently occurred when cross-linked guar gel (CLGG) was used. The core flow tests by Devine et al.(1) showed that the permeability reduction by CLGG was 56% ∼ 71% for cores of 100 ∼ 200 mD, and 12% ∼ 35% for cores of less than 1 mD. The fluid damage to the tight sand was less severe than that of a permeable formation(1, 2). The experiment study by Almond(3) at 120 ° F with 20/40 mesh sand packs (simulating fractures) showed that the flow reduction by CLGG damage could be as high as 100%. Without doubt, damage of this order of magnitude will greatly decrease the productivity of fractured wells, whether the damage happens in formations or in propped fractures. Therefore, fluid impairment by CLGG could be a significant problem adversely influencing the success of fracturing operations. Fluid cost is another critical factor of fracturing, especially in low permeability and tight reservoirs where the job size is large and the fluid cost is high, but the well productivity is low and declines faster than that of fractured wells in conventional reservoirs. Fluid cost saving is a key factor to economically develop these reservoirs, in particular when they are marginal reservoirs.