Slurry Concentration Research Articles

Study on prediction model of slurry concentration of low-rank coal and anionic sulfonate additives

In this work, eight kinds of low-rank coal and four kinds of anionic sulfonate additives including lignin series, naphthalene series, humic acid series, and aliphatic series dispersants were selected for slurry experiments. The Spearman correlation analysis method was used to investigate the influence of coal quality factors including moisture, ash, volatile matter, fixed carbon, O/C value, and peak area ratio CO/CO value on the slurry ability of low-rank coal under different dispersant conditions. The results show that moisture, volatile matter, O/C value, and CO/CO value in coal are negatively correlated with slurry ability, while ash and fixed carbon are positively correlated with slurry ability. According to the Spearman correlation coefficient, moisture, volatile matter, O/C value, and CO/CO value in coal are closely related to the slurry ability of low-rank coal. The prediction model of slurry concentration of low-rank coal and anionic sulfonic acid additive based on coal characteristic factors is established by partial least squares (PLS):ySLS=75.859-0.498x1+0.566x2-5.786x3-157.895x4yNSF=79.706-0.123x1+0.567x2-7.123x3-182.900x4ySHS=80.642+0.012x1+0.387x2+4.503x3-180.657x4ySAF=80.702+0.271x1+0.508x2-18.743x3-182.057x4Where yi is the constant-viscosity concentration, the unit is %; x1 is moisture (Mad), the unit is %; x2 is volatile (Vdaf), the unit is %; x3 is the O/C value; x4 is CO/CO value. By comparing the experimental value with the predicted value, the R2 value of the linear regression fitting is larger than 0.95, the error rate is within ± 3 %, and while using the constant-viscosity concentration to determine the matching performance of coal and dispersant, the predicted value is consistent with the experimental value, which verifies the rationality and accuracy of the model.

Effects of Critical Operation and Cleaning Parameters on Performances and Economic Benefits of Biogas Slurry Concentration by Forward Osmosis Membrane.

Forward osmosis membrane technology (FO) shows potential application prospects in biogas slurry concentration, which is conducive to promoting the sustainable development of biogas projects. However, at present, the key influencing factors of membrane concentration using FO are not well understood. Therefore, this study analyzed the influence of draw solution concentration, pH, temperature and cross-flow velocity on the concentration efficiency of FO membrane, and optimized the operation parameters of FO membrane. The results showed that the concentration effect of the NaCl draw solution at pH 5 or 9 was better than that at pH 7. The order of factor influencing the water flux was as follows: draw liquid concentration > cross-flow velocity > operating temperature. The optimal combination obtained by orthogonal analysis was under 45 °C, with a cross-flow velocity of 1 L/min and the use of 1.5 mol/L NaCl as draw solution. The results of the membrane cleaning implied that the recovery rate of the fouled membrane after acid-base cleaning is significantly higher (88%) than other cleaning solutions. This research offers a scientific reference for applying positive osmosis technology to re-utilize biogas slurry resources.

Grouting mechanism and experimental study of goaf considering filtration effect.

The filtration effect significantly affects the gangue slurry velocity and concentration, making it difficult to evaluate the gangue slurry diffusion range. Based on the Darcy seepage law, a seepage theoretical calculation model is established considering the filtration time and space effect. And the "water-cement ratio change matrix" in the seepage process of coal gangue slurry is deduced, revealing the basic mechanism of the porous media filtration effect, and the water-cement ratio gradually increases in the seepage process of gangue slurry. The visual test platform for slurry diffusion in goaf was independently developed for testing. The active heating optical fiber method (AHFO) was used to monitor the flow and diffusion of coal gangue slurry in the collapse zone of goaf, and the gravity gradient and water cement ratio of slurry in goaf were measured. The law of particle sedimentation in the gangue slurry flow process under the filtration effect was revealed, and engineering verification was carried out. The results show that the average slope of the gangue slurry in the gangue accumulation is 6.34%, and the overall flow law of the gangue slurry in the goaf is the first longitudinal expansion and then transverse diffusion. The water-cement ratio near the grouting mouth is smaller than the initial water-cement ratio, the near-end water-cement ratio is smaller, and the far-end water-cement ratio is larger. During on-site filling, the accumulated grouting volume of a single hole is 700 m3, and the gangue slurry diffusion distance is greater than 45m, indicating that the gangue slurry has good fluidity.

Preparation and Properties of Double Liquid Grouting Materials (DLGMs) Used for the Regenerated Roof of a Coal Mine

Double liquid grouting materials (DLGMs) are composed of slurry A and slurry B. In response to the need for sustainable development, there is currently a focus on improving the utilization rate of resources. In this paper, industrial solid waste fly ash, slag, and ordinary Portland cement were used to prepare slurry A, while sodium silicate was used as slurry B. Slurry C was made by adding slurry B to slurry A. The mix design parameters of the DLGMs, with large amounts of fly ash, were optimized based on the response surface method. The results showed that the relative content of cement and the reactivity and morphological effect of supplementary cementitious materials (fly ash and slag) were the main factors affecting the operable time, viscosity, and stability of slurry A. The relative content of cement and the sodium silicate modulus were the main factors affecting the operable time of the DLGMs. Compared to the C30F70S0-Z3.3 group (where C, F, S, and Z represented cement, fly ash, slag, and sodium silicate modulus, respectively), the operable time of the C0F70S30-Z3.3 group increased by approximately 36 min. As the sodium silicate modulus was lowered to 2.3, the operable time of the C0F70S30-Z2.3 group increased by about 32 min compared to that of the C30F70S0-Z2.3 group. The established model and response surface can well reflect the influence of multiple factors on the properties of the DLGMs. When the mass ratio of cement/fly ash/slag in slurry A was 7.5%: 70%: 22.5%, and the sodium silicate modulus and content of slurry B were 2.8 and 10%, respectively, the 28-day compressive strength of the DLGMs can reach up to 11.3 MPa. The content of fly ash was the most significant factor affecting the 28-day compressive strength of the DLGMs, followed by the sodium silicate content. The least influential factor was the sodium silicate modulus. The XRD and SEM results showed that a large amount of Ca2+ produced by cement hydration can quickly react with [SiO4]4- in sodium silicate to form C-S-H gel. Moreover, it also promoted the hydration of C3S and C2S in grouting to produce more C-S-H gel, which was conducive to the alkali activation of slag and fly ash, resulting in a denser microstructure and hence, yielded obvious increases in the compressive strengths of the DLGMs.

A novel hydro‐mechanical coupled multiphysics model for slurry penetration in sand with application to face stability analysis of shield tunnel

AbstractThe slurry penetration in tunnels driven by the slurry TBM in the highly permeable water‐bearing ground is a complicated multiphysics process, which significantly affects the stability of the excavation face but has not been fully modelled. This study establishes a novel hydro‐mechanical coupled multiphysics modelling approach for face stability analysis. Different from existing methods, the proposed one is able to quantify simultaneously the spatial and temporal variation of slurry concentration, viscosity, stagnation gradient, soil porosity and pore pressure, as well as the soil skeleton deformation induced by the transferred slurry pressure in two or three‐dimension. The spatial and temporal pressure transfer from slurry suspension to soil skeleton during slurry penetration can be obtained. The coupled formulations are implemented into a finite element package for initial and boundary value problems at the engineering scale and enhanced by the Petrov‐Galerkin weighted residual stabilisation technique. After being validated through the experimental slurry infiltration tests, it is applied to a field case analysis to predict the excess pore pressure in front of the tunnel face, which shows good agreement with the field measurement. The efficiency of the applied slurry pressure and the pressure transfer mechanism are thus verified. Comparative calculations about the influence of the pressure transfer model are presented to further improve the understanding of the pressure transfer mechanism. The proposed approach is also verified applicable to estimate the optimum slurry pressure.

Impact of different brushing/abrasion protocols on erosive tooth wear for in vitro studies

ObjectiveTo investigate the influence of different toothbrushing (with dentifrice) protocols on the progression of erosive tooth wear for in vitro studies. DesignBovine enamel specimens were randomly distributed into 12 experimental groups (n = 10), according to the study factors: (1) brushing movement (horizontal or circular); (2) slurry diluent (artificial saliva or distilled water); (3) toothpaste dilution ratio (1:2, 1:3 or 1:4). A 5-day erosion-abrasion cycling model was performed, each consisting of 4 erosive challenges (0.3 % citric acid, pH=2.6) followed by 60 min exposure to artificial saliva. Brushing with fluoride toothpaste (15 s, 1400 ppm F-, AmF) was carried out 2x/day. Enamel surface loss (SL) was determined by optical profilometry. Data were statistically analyzed with three-way ANOVA and Tukey tests (α = 0.05). ResultsSL was lower for the horizontal movement than for the circular (p = 0.044). There were no significant differences among the dilution ratios for artificial saliva. For distilled water, the more concentrated slurry (1:2) presented greater surface loss than the less concentrated slurries (1:3 and 1:4, p = 0.049 and p = 0.014, respectively). Dilutions with artificial saliva at ratios 1:3 and 1:4 presented higher surface loss than with distilled water (p = 0.008 and p < 0.001, respectively); however, for 1:2 ratio, there were no significant differences between the diluents. ConclusionsThe in vitro progression of enamel SL was influenced by the brushing movement, as well as the combination of the dilution ratio and the diluent of the toothpaste slurry, and therefore, all these factors must be considered when comparing results from different studies.

Experimental Investigations on Erosion-Corrosion Characteristics of HVOF-Sprayed WC-10% Ni Coatings Deposited on Aluminum Alloy

The current work investigates the erosion-corrosion behaviour of thermally sprayed tungsten carbide-10% nickel (WC-10% Ni) coatings placed on the AA6061 aluminum alloy. The AA6061 aluminum alloy was coated with tungsten carbide –10% nickel coatings utilising a high-velocityoxy-fuel (HVOF) spray method. The microstructure and hardness of thermally sprayed coatings were examined using a scanning electron microscope (SEM) and a Vickers hardness tester. The slurry erosion-corrosion wear tests were carried out by varying the parameters of the slurry erosion process, such as testing time, slurry content, slurry speed, and impinging particle size, on the erosion testing equipment. The data demonstrated that when slurry concentration, slurry speed, and impinging particle size increased, so did the slurry erosion-corrosion wear loss. The wear processes of uncoated and thermally sprayed tungsten carbide –10% nickel have been examined using SEM and a 3-D confocal microscope.

Relationships among Physicochemical, Microbiological, and Parasitological Parameters, Ecotoxicity, and Biochemical Methane Potential of Pig Slurry

Background: Pig slurry can negatively impact on the environmental, animal, and human health. Knowing the relationship between the organic and inorganic loads, pathogens, and toxicity allows identifying the main parameters to be removed or treated before final disposal. The aim of this study was to evaluate the relationships between the physicochemical properties, microbiological, and parasitological content, ecotoxicological effects, and biochemical methane potential (BMP) of pig slurries. Methods: Ten pig slurry samples at two production stages were characterized and a BMP test at two substrate/inoculum (S/I) ratios was conducted to compare the methane yields. Results: We found high content of Cu, Zn, quaternary ammonium, pathogenic microorganisms (E. coli and Salmonella), and parasites (Trichuris and Trichostrongylus). Toxicity on lettuce, radish, and Daphnia was observed with a slurry concentration greater than 1.35%. Positive correlations were found between toxicity on Daphnia and chemical oxygen demand (COD), sulfate, Zn, and Cu, as well as between phytotoxicity and COD, NH4, Na, K, and conductivity. The lowest S/I ratio showed 13% more methane yield. It was associated with high removals of COD and volatile fatty acids. Conclusions: We recommend using a low S/I ratio to treat pig slurry as it improves the efficiency of the anaerobic process.

Feasibility of Bio-Coagulation Dewatering Followed by Bio-Oxidation Process for Treating Swine Wastewater.

The unsatisfactory performance of the conventional swine wastewater treatment is drawing increasing attention due to the large amount of refractory chemical oxygen demand (COD), nitrogen, and phosphorus attached to the suspended solids (SS). In this study, for the first time, a novel process based on bio-coagulation dewatering followed by a bio-oxidation (BDBO) system was developed to treat swine wastewater containing high-strength SS, COD, TN, and TP. Firstly, after the bio-coagulation process, the removal efficiencies of SS, COD, NH3-N, and TP reached as high as 99.94%, 98.09%, 61.19%, and 99.92%, respectively. Secondly, the filtrate of the bio-coagulation dewatering process was introduced into the subsequent bio-oxidation process, in which the residual COD and NH3-N were further biodegraded in a sequence batch reactor. In addition, the dewatering performance of the concentrated swine slurry was substantially improved, with the specific resistance to filtration decreasing from 17.0 × 1012 to 0.3 × 1012 m/kg. Moreover, the concentrated swine slurry was pressed and filtered into a semi-dry cake after pilot-scale bio-coagulation dewatering treatment. Finally, the concentrations of COD and NH3-N in the effluent after the BDBO process, ranging between 150-170 mg/L and 75-90 mg/L, met the relevant discharge standard. Compared to traditional treatments, the BDBO system has excellent large-scale potential for improving the treatment efficiency, shortening the operation period, and reducing the processing costs, and is emerging as a cost-effective alternative for the treatment of wastewater containing high concentrations of SS, COD, TN, and TP.

Research on key parameters of pipeline transportation of waste rock treatment in underground residual space

As the key link of coal gangue slurry filling, slurry pipeline transportation is an important guarantee to realize the slurry mixing and safe transportation of gangue from solid powder. To realize the underground excavation gangue of the Huangling No. 2 coal mine without raising the ground, the slurry filling technology is proposed to transport the slurry made by gangue through the pipeline and fill it into the goaf. The phase composition and microstructure characteristics of underground excavation gangue in the Huangling No. 2 coal mine were analyzed by X-ray diffraction and an electron microscope scanning test, the slurry-forming properties of gangue powder with different particle sizes and gradations were studied, and the influence of gangue slurry concentration on its rheological properties was analyzed. The experimental results show that the gangue powder crushed using a cage crusher can be made into stable slurry when the particle grading size is the natural crushing gradation with the upper limit of particle size less than 3 mm. The viscosity of the slurry is positively correlated with the concentration. When the concentration is below 70%, the increase in viscosity is small, and when the concentration is above 70%, the increase in viscosity is significant. It is determined that the concentration of the Huangling No. 2 coal mine slurry is 70%. Based on the determination of slurry preparation parameters, the simulation analysis of slurry pipeline transportation was carried out, the influence of design velocity on the velocity distribution of the pipeline section and the variation law of slurry concentration was explored, and the design velocity of the project is determined to be 1.5 m/s. The engineering practice shows that the slurry preparation parameters are reasonable. The crushing and pulping of gangue under the ground and the safe transportation of a 6 km pipeline are realized, which provides a reference for similar engineering projects.

Slurry erosion behaviour of HVOF sprayed VC+TiC based novel coatings: Characterization and optimization studies

The current experimental work is focused on development and characterization of HVOF sprayed VC-TiC+CuNi-Cr based coatings on hydro-machinery steel SS316. Empirical correlations for mass loss have been developed with the aid of response surface methodology (RSM) approach. Central composite design (CCD) matrix has been acquired with five different levels over four impingement parameters namely impingement angle, jet velocity, slurry concentration, and exposure time. When compared with bare SS316 steel, a significant increase in the slurry wear resistance of SS316 steel was noticed for different variants of developed coating. Moreover, ductile erosion mode was observed in coatings containing CuNi-Cr as the main component, which was reported to transform into the brittle mode with increasing VC-TiC percentage.

Experimental study on supercooled water release supercooled state for generating ice crystals

Ice blocking and low single-cycle ice production rate are the two major deficiencies of supercooled water ice making. A lot of research has been done by domestic and foreign scholars on controlling ice blocking. The ice production rate of a single cycle is theoretically proportional to the degree of subcooling. In fact, the subcooling release also affects the ice slurry concentration. To improve the ice slurry concentration, this paper investigates the factors of affecting the degree of subcooling release, including three factors: ultrasonic power, subcooling degree, and the residence time of subcooled water in the ice slurry generator, and experiments with a way to produce high concentration ice slurry. The results showed that the greater the degree of subcooling, the deeper the degree of subcooling release; the ultrasonic power and the residence time of subcooled water in the ice slurry generator had little effect on the degree of subcooling release. The average ice content of the ice slurry reached 30.5% after 8 min of continuous ice production in the experiment.

Investigations on erosion performance of carbon fiber–epoxy-based composite adhesion on 16Cr5Ni steel

This work presents a novel insight into slurry erosion behavior of thin layer of carbon fiber–epoxy-based composite adhered on 16Cr5Ni steel (adhesive coating) to evaluate its viability as a feasible candidate for slurry erosion applications. Experiments were conducted on a laboratory-developed slurry erosion test rig under accelerated conditions to study the effect erosion parameters namely slurry concentration, impact angle, and impact velocity. Under all the experimental conditions, adhesive coating showed better slurry erosion resistance in comparison with bare 16Cr5Ni steel specimens. Scanning electron microscopy analysis revealed that in the case of bare 16Cr5Ni steel; ploughing, micro-cutting, crater, plastic deformation, and lip formation were identified as main mechanism responsible for slurry erosion, whereas in the case of adhesive coating; pitting, cracking, fracturing, and shearing-off were found to be mainly responsible for material loss. It implies that adhesive coating showed a brittle mode of failure under slurry erosion conditions, whereas 16Cr5Ni steel exhibited a ductile mode of erosion.

Optimisation of phosphorus recovery process from biogas slurry using straw-derived biochar coupled with Mg/La oxide as an adsorbent

Phosphorus recovery from biogas slurry can realize the management and utilization of nutrients. Phosphorus adsorption has been hindered by multiple issues, including the incompatibility of biogas slurry and the lack of phosphorus recovery research. Therefore, the key influencing factors and adsorption mechanisms of phosphorus recovery should be analysed to effectively use biogas slurry resources. In this study, a new adsorbent of straw-derived biochar coupled with Mg/La oxides (6YBC-LDO) was used as an adsorption column filler. The effects of adsorption column height, biogas slurry concentration and flow velocity on phosphorus recovery were also studied via the response surface method (RSM). The results showed that when the mass concentration, flow rate, and column height of biogas slurry were 106.24 mg/L, 2.44 mL/min, and 1.60 cm, respectively, the recovery efficiency of phosphorus was higher, and the equilibrium adsorption capacity (qequ.) could reach 287.58 mg/g. The optimised process could further improve the regeneration rate and life cycle of 6YBC-LDO. Correlation analysis of phosphorus recovery efficiency and the characteristics of biogas slurry showed that high chemical oxygen demand (COD) and total solids (TS) content have a positive correlation with the phosphorus concentration of biogas slurry. High solid content may hinder the flow rate of biogas slurry, which directly and indirectly affects the phosphorus recovery efficiency, and the results provide a scientific basis for regulating phosphorus recovery in biogas slurry.

Computational Fluid Dynamic Modelling of Fully-Suspended Slurry Flows in Horizontal Pipes with Different Solids Concentrations

This research work is a significant step toward further understanding of the β-σ two-fluid model for the simulation of fully-suspended slurry flows in pipeline systems, with the goal of enhancing its potential for scientific research and engineering applications. Particularly, the focus of the study is the characterization and handling of the two main empirical coefficients of the model, namely, β and σ, which require case-specific tuning based on a given set of experimental data. Reference is made to the relevant case of slurry transport in horizontal pipes with infinite length. The influence of β and σ on different features of the fluid dynamic solution has been extensively investigated, considering also the role played by the specific testing conditions. Based on these findings, a procedure for determining appropriate values of β and σ has been developed, which requires only two experimental measurements, namely the concentration profile from a test at moderate slurry concentration, and the hydraulic gradient from another test in which the same slurry flows at high concentration. The procedure has been satisfactorily tested against published experimental data on pipe transport of fine glass bead and sand slurry.

Influences of solid content of slurry on the microstructure of CaO crucible prepared by slip casting

AbstractCaO crucible was prepared from Ca(OH)2 slurry via a slip‐casting method in order to avoid hydration problem caused by free CaO during preparation process. The effect of solid content of Ca(OH)2 slurry on microstructure of CaO crucible was investigated. It was found that the rheological property of the slurry was significantly improved when the solid content of the slurry within a certain range. The change of solid content of slurry affects the microstructure of the final products. When the solid content of the slurry was 71 wt%, the manufactured CaO crucible was of smallest mean pore size (2.58 μm) after 1600°C heating treatment. The heated CaO sample was of lower apparent porosity (4.1%) and higher bulk density (2.93 g/cm3). And the size distributions of most CaO grains are between 10 and 40 μm.

Combination of direct ink writing and reaction bonded for rapid fabrication of SiCw/SiC composites

Silicon carbide ceramic matrix composites are widely used in aerospace field due to their advantages of high temperature resistance, high strength and corrosion resistance. However, its application is greatly limited because of the difficulty in preparing complex shape structures by traditional machining methods. Here, a new strategy for preparing SiC w /SiC complex structure by combining direct ink writing with reaction bonding is proposed. A water-based slurry consisting of silicon carbide, carbon powder and silicon carbide whisker was developed. The influence laws of C content and SiC w content in slurry on sintering properties of direct-written samples were studied. The reaction bonding mechanism and whisker reinforcing and toughening mechanism were analyzed by means of microstructure and phase composition. The results show that the slurry exhibits shear thinning behavior with stress yield point, and its flow behavior and plasticity meet the requirements of direct writing. When the carbon content is 6.4 wt%, the maximum flexural strength is 239.3 MPa. When 15 wt% SiC w was added, the flexural strength of the composite reached 301.6 MPa, and when 20 wt% SiC w was added, the fracture toughness of the composite reached 4.02 MPa m 1/2 , which was increased by 26% and 18% compared with single-phase SiC, respectively. The reinforcing and toughening mechanisms of the whiskers mainly include whisker pullout, crack deflection and whisker bridging. After direct ink writing and reaction bonded, the whole process shows good near net forming ability. 3D printed SiC w /SiC composites have great application prospects in aerospace field.

Just-In-Time Learning Based Functional Spectral Data Modeling for In-Situ Measurement of Slurry Component Concentrations via Infrared Spectroscopy

For using the infrared spectroscopy to conduct in-situ measurement of slurry component concentrations during batch crystallization or fermentation process in engineering practice, a novel just-in-time learning (JITL) based functional modelling method is proposed for spectral data analysis in this paper to improve on-line measurement accuracy, by addressing engineering issues of very limited assay samples, spectral absorption nonlinearity and high-dimensional spectral variables. The traditional univariate or multivariate partial least-squares (PLS) model is subtly extended to the corresponding functional form for describing the relationship between the measured spectra and slurry component concentrations, such that the salient problem of only a small number of slurry component concentration samples available in practice for spectral data modeling could be effectively solved. The wavelet functions are adopted to properly approximate the measured spectral curves owing to their multi-scale and orthogonal properties. Accordingly, a functional spectral data model is established by wavelet functional PLS for on-line measurement of single and multiple component concentrations, respectively. Meanwhile, a JITL strategy is introduced to select the most representative samples for such modeling, which could efficiently handle the disparity issue involved with real-time samples and guarantee the model validity. Experimental results show that root mean square error of model prediction on the solution concentration during L-glutamic acid cooling crystallization process and multiple componts of ethanol fermentation process, could be evidently reduced over 40% and 50%, respectively, compared with the traditional PLS and support vector regression methods.

Entropy generation analysis on thermo-hydraulic characteristics of microencapsulated phase change slurry in wavy microchannel with porous fins

• Combined design enables smaller temperature gradient and more uniform temperature. • Larger h m and lower ΔP can be concurrently gained in wavy MCHS with porous fins. • Thermal entropy is three orders of magnitude larger than the frictional entropy. • Thermal entropy increases with heat flux but the frictional entropy is opposite. • Lower irreversible losses can be achieved at the cost of higher power consumption. Recent advancement in micro/nano-scale electronic systems, the need for efficient heat dissipation has become more rigorous, and traditional thermal management solutions are facing enormous challenges. In this study, a novel combined design of wavy microchannel heat sink (MCHS) with porous fins and microencapsulated phase change material (MPCM) suspension is developed and numerically studied to achieve a balance between flow and heat transfer behaviors. The equivalent heat capacity method is adopted to deal with the phase change process of microcapsule particles in steady and laminar states, and the Brinkman–Darcy–Forchheimer model based on the volume-averaged method is employed to characterize the fluid flow in porous fins. A three-dimensional solid-fluid conjugate model is established based on the finite-volume method to investigate the effects of different coolant types (water and MPCM suspension), geometric parameters (wavy amplitude, wavelength, and channel width ratio), and working conditions (inlet flow velocity, heat flux, and slurry concentration) on the thermo-hydraulic properties and entropy generation of wavy MCHS. The results reveal that the combination of porous fins and MPCM suspension presents smaller temperature gradient and more uniform temperature distribution than conventional design. Larger heat transfer coefficient and lower pressure drop can be simultaneously obtained in wavy MCHS with porous fins than in solid fin configuration. The thermal entropy generation is three orders of magnitude larger than the frictional entropy generation, and the Bejan number is close to 1 for different microchannel configurations. Thermal entropy generation increases with increasing heat flux but the frictional entropy generation decreases. Lower irreversible losses can be achieved at the expense of greater pumping power consumption caused by increasing inlet velocity and suspension concentration. The superior effect of wavy MCHS with porous fins using MPCM suspension as coolant has been observed in all cases.

Development of Dewatering Concentration Method for Cellulose-Nanofibers Slurry by Using Multi Wires

Cellulose nanofibers (CNFs) which are extremely small fibers with a width of several nm comprising mainly crystalline cellulose. They are a promising material with many superior characteristics in a wide range of industrial fields, and have been developed by domestic and foreign paper mill companies. CNF slurry with a high water content (> 98%) is usually supplied because CNFs are generally produced through pulp nanofibrillation in a relatively large volume water. Dewatering of CNF slurry is an important issue because this process affects various processes such as shipping, drying, and product developments. To dehydrate and concentrate CNF with a high-water retention efficiently, the original dewatering CNF method with multiple wires was used in this study. First, the CNFs obtained by mechanical nanofibrillation were prepared using a grinder from Laubholz bleached kraft pulp (LBKP). The fibers with a nano-scale width and a micro-scale fiber network were observed in the prepared CNF slurry. Furthermore, flocculation and dispersion in CNF slurry occurred. Second, the initial solid concentration of CNF slurry, wire opening, and number of wire stacks affected the CNF dewatering in the static and batch tests. In this test, a recovery yield (retention) of 87.7% and concentration to 9.5% were achieved using three stacked wires from CNF slurry of 1.7%. Third, the laboratory-scale apparatus for dynamic CNF dewatering was constructed assuming the practical continuous manufacturing machine, and applied. The gradual suction; combining weaker suction (5 kPa) with multiple wires in the early stage and stronger suction with a single wire in the later stage, was the most effective for dewatering CNF using metal wires. However, multiple wires and the combination of weaker suction in the early stage and stronger suction in the later stage were suitable for dewatering CNF using plastic wires. Ultimately, 98% retention a solid concentration of 9.9% were achieved in the dynamic tests using multiple plastic wires.