Simulated Slurry Research Articles

Research on mercury re-release model in wet flue gas desulfurization (WFGD) in coal-fired power plants

Mercury (Hg), a toxic heavy metal, has triggered regulations for emission control from coal-fired power plants. It has been found that mercury re-release occurs in WFGD slurry, which is affected by WFGD process parameters. The coal co-combustion with bromide technology proves to be an efficient approach for enhancing mercury removal ratio but the accumulation of introduced bromine in WFGD slurry would impact the re-emission behavior of mercury significantly. Model study is efficient method to reveal the physicochemical processes in WFGD systems. However, previous model studies were carried out under Hg2+ contained simulated slurry systems without consideration of Hg2+ transformation process from gas to liquid phase, and co-combustion with bromide technology was not considered. Here, a model which encompasses droplets motion sub-model, gas–liquid heat transfer sub-model, gas–liquid mass transfer sub-model and the mercury re-release kinetic sub-model is developed and validated against experimental data. The effects of bromine concentration, slurry temperature, pH value and S(IV) concentration were investigated. It was found that introduced bromine has significant inhibitory effects on the re-release of mercury. When the slurry temperature is higher, the absorption rate of Hg2+ is lower and more Hg0 is released. Moreover, the increase in the slurry pH value and S(IV) concentration has certain inhibitory effects on the re-release of Hg0 in WFGD. Above all, the developed model has high prediction accuracy for the absorption of Hg2+ and the re-release of Hg0 in WFGD which is expected to be beneficial for guiding the operation of WFGD systems.

Lithium Ion Battery Electrode Calendering Study By Combining X-Ray Computed Tomography and 3D-Resolved Physical Process Models

Significant amount of research has been done recently on how to increase energy densities while maintaining or lowering costs in response to the growing demand for lithium-ion batteries (LIBs). In order to achieve optimization of the manufacturing process of batteries, it is essential to understand the influence of each process stage on the architectures of the electrodes, which affects the energy, power, lifetime and safety of the LIB cells. Our ERC-funded ARTISTIC project1 develops a digital twin that enables predicting the electrode architectures and their electrochemical performances from parameters at each stage of the LIBs manufacturing process.In this work, we present our most recent research, which studies the manufacturing process of LiNixMnyCo1-x-yO2 (NMC)-based cathodes and especially focuses on the electrode calendering stage2. Our methodology encompasses coarse-grained molecular dynamics and discrete element method to simulate the calendering process of electrodes that are virtually produced after the drying and slurry simulations. In this new work, we account in our model for non-spherical NMC secondary particles with realistic 3D shapes derived by X-ray computed tomography (XCT), together with spherical particles representing the carbon binder domain. An in situ compressing micro-XCT experiment is carried out on the NMC electrode to monitor the change of the electrode morphology upon the calendering process. The findings from the simulation are validated by comparing our predicted electrode architectures with the experimental ones. Our approach captures the alterations in orientation of the secondary particles throughout the calendering processes and the relaxation process, as well as their possible deformation and spring back effect brought on by the pressure. Additionally, we discuss the comparison of variations in porosity, tortuosity factor, conductivity, different phases distribution and pore size distribution during the calendering process. ERC Artistic : Home Artistic. http://www.erc-artistic.eu/.Xu, J., Ngandjong, A.C., Liu, C., Zanotto, F.M., Arcelus, O., Demortière, A., and Franco, A.A. (2023). Lithium ion battery electrode manufacturing model accounting for 3D realistic shapes of active material particles. Journal of Power Sources 554, 232294. 10.1016/j.jpowsour.2022.232294.

Experimental study on migration and transformation of selenium species and DFT calculation in WFGD simulated slurry

Selenium is a harmful trace element emitted during the combustion process of coal-fired power plants. Most of the selenium is enriched in the downstream wet flue gas desulfurization system (WFGD). This study found that S2O82- is the most important factor affecting the oxidation of selenite. In the process of simulating slurry oxidation of selenite to selenate, the presence of S2O82- can increase the oxidation rate of selenate from about 50% to about 80%. At the same time, this study also considered the influence of selenium concentration, initial pH, SO2 concentration and temperature etc. on the transformation of selenium species. It was believed that the application of ORP to the indication of selenite oxidation status needs further demonstration. Energy Dispersive X-Ray Spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) were used to confirm the migration of selenium in the desulfurization slurry to gypsum. In addition, DFT calculation was performed to obtain theoretical parameters for the adsorption of selenite and selenate by gypsum. The results of this study are helpful to understand the transformation and migration of selenium in the desulfurization system, which provide theoretical support for the realization of selenium in-situ control.

Selenium migration mechanism in wet FGD slurry: Experimental and DFT analysis

Selenium (Se) is one of the hazardous trace elements emitted from coal-fired power plants. The Se migration behavior in wet flue gas desulfurization (FGD) slurry is still unclear, and the species of Se in FGD gypsum remains controversial. In this research, the bubbling experiments using simulated slurry with/without gypsum crystallization process were conducted. The experimental results indicated that pure gypsum has poor capability to capture Se components, and only selenite could be trapped in gypsum during its crystal growth stage. Furthermore, the DFT calculation was conducted to provide the microscopic information of Se adsorption and substitution characteristics during gypsum crystallization process. The research findings of this study could help understand the mechanism of Se migration process in FGD slurry, and facilitate the development of effective Se emission control technologies in the future.

The distribution and conversion of selenite and selenate with the bubbling of simulated flue gas in simulated WFGD slurry

Selenium is one of the hazardous trace elements emitted from coal-fired power plants. The distribution of selenium in Wet Flue Gas Desulfurization (WFGD) process is still unclear and even in controversial, impeding the development of selenium removal technologies. This research has found that the selenite in simulated slurry could be reduced by SO2 while selenate has not been affected. Characterization methods including X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to provide an evidence that the product of the reduction reaction is amorphous elemental selenium. Meanwhile, the influences of other gaseous components, pH, temperature and S2O82− in simulated slurry has also been considered in this research. It is found that with the increase of SO2 concentration in flue gas, the reduction of selenite increased and the reduction reaction is an exothermic reaction. Meanwhile, the oxidation effect of S2O82− competes with the reduction effect of SO2. This study introduced the influence of flue gas into the research of the conversion of selenium in FGD slurry and indicate the effect of flue gas on the potential emission treatment techniques of selenium in FGD slurry.

Clay in situ resource utilization with Mars global simulant slurries for additive manufacturing and traditional shaping of unfired green bodies

The wet processing of regolith simulant for clay in situ resource utilization (ISRU) on Mars is presented. The two raw materials from the Mars global simulant family, one without clay (MGS-1) and one with clay - sodium montmorillonite smectite - (MGS-1C) were milled and mixed to produce a simulant with small particle size and reduced clay content (MGS-1C/8). All three simulants and the pure clay raw material were extensively characterized using XRF, synchrotron XRD, gas adsorption and gas pycnometry methods. In a straightforward processing approach, MGS-1C/8 was mixed with water and different dispersant approaches were investigated, all of which gave stable slurries. Particle size distribution, rheology, ion concentration, pH and electrical conductivity of these slurries were characterized. The slurry systems can easily be adapted to fit all typical ceramic shaping routes and here parts of varying complexity from slip casting, throwing on a potter's wheel and additive manufacturing, including material extrusion (robocasting) and binder jetting (powder bed 3D printing) were produced. The unique properties of the sodium montmorillonite clay, which is readily accessible in conjunction with magnesium sulfate on the Martian surface, acted as a natural nanosized binder and produced high strength green bodies (unfired ceramic body) with compressive strength from 3.3 to 7.5 MPa. The most elaborate additive manufacturing technique layerwise slurry deposition (LSD) produced water-resistant green bodies with a compressive strength of 30.8 ± 2.5 MPa by employing a polymeric binder, which is similar or higher than the strength of standard concrete. The unfired green bodies show sufficient strength to be used for remote habitat building on Mars using additive manufacturing without humans being present.

Accelerated Optimization Methods for Force‐Field Parametrization in Battery Electrode Manufacturing Modeling

AbstractThe performance, durability and cost of modern Li‐ion batteries (LIBs) strongly depend on their manufacturing process. In this regard, computational methods that attempt to model LIBs manufacturing have the potential to help experimentalists to reduce costs and improve performances of LIBs. To do so, the electrode slurry phase, consisting of a suspension of active material, carbon additive and binder in a solvent must be modeled at first at the mesoscopic scale. However, efforts in that sense are rare in literature due to the inherent complexity of slurries and the difficulty of setting up appropriate metrics for the validation of the modeling results. For the first time, we propose an approach relying on experimental data that allows to validate the properties of simulated Nickel‐Manganese‐Cobalt‐based slurries with different compositions and solid contents through force fields (FFs) parametrization. The latter was attained by Coarse‐Grained Molecular Dynamics (CGMD), which enables to model the slurry phase at the mesoscopic scale and to consider explicitly the carbon binder domain. Moreover, we demonstrate that the CGMD FFs parameterization can be accelerated thanks to different types of Particle Swarm Optimization‐based algorithms, which would allow faster screening of different simulated slurries fabrication conditions.

Jet properties and mixing chamber flow in a high-pressure abrasive slurry jet: part II—machining rates and CFD modeling

Part I of this two-part paper presented mixing chamber conditions and jet characteristics in a high-pressure abrasive slurry jet micro-machining (HASJM) system. The present paper describes the modeling of the slurry entrainment process within the mixing chamber and mixing tube of the nozzle using computational fluid dynamics (CFD) and shows how the results can be used to explain and predict machining performance. The slurry flow rate into the mixing chamber was found to have a large impact on the performance of the jet due to differences in the momentum of the high-velocity water and low-velocity slurry. The erosive efficacy of the jet was assessed by machining channels and blind holes in aluminum 6061-T6. Differences in the centerline erosion rates of holes and channels for a given jet showed clear evidence of incubation and stagnation zone effects. The CFD models simulated various slurry flow rates entering the mixing chamber as a result of the low pressure created by the central high-velocity jet of water. They predicted correctly an experimentally observed flooding condition in which slurry completely filled the mixing chamber and mixing tube. The models could also identify the transient conditions leading to the onset of this flooding as the chamber first began to fill, which could not be identified experimentally. Flooding was found to significantly reduce the jet velocity, thus diminishing its erosive efficacy. The models also identified the operating conditions within the mixing chamber that produced boiling due to the low internal pressure generated by the central high-velocity jet of water. This boiling condition was found in part I to result in a wider jet exiting the mixing tube.

Utilization of Water Utility Lime Sludge for Flue Gas Desulfurization in Coal-Fired Power Plants: Part II. Lime Sludge Characterization and Mercury Reemission.

The feasibility of utilizing lime sludge in the flue gas desulfurization process of coal-fired power plants was evaluated through laboratory-scale studies. Eight lime sludge samples, collected from various water treatment plants, and a high-purity limestone sample were extensively characterized and tested for their ability to capture SO2 from a simulated flue gas, while investigating the mercury reemission profiles during the scrubbing process. The reactivity of lime sludge samples for acid neutralization was significantly higher than the reactivity of the tested limestone sample. At doses less than that of the limestone sample, the lime sludge materials reduced the SO2 concentration from 2,000 to <0.5 ppm. The residual lime, higher surface area, and more accessible pores in lime sludge samples were the major factors contributing to their higher reactivity. Concentrations of several elements including B, Mg, Mn, Fe, Cu, Zn, As, Sr, and Ba in some of the tested lime sludge samples were considerably higher than those elements in the limestone. However, no significant leaching of these elements into the scrubber solutions was observed. To investigate mercury reemission during the scrubbing process, ionic mercury was introduced into the simulated slurry and mercury reemission was monitored continuously. Results showed that compared with the limestone sample, the lime sludge samples tested had lower or similar cumulative mercury reemissions. However, different lime sludge samples showed different emission profiles. No conclusive correlation between the composition or trace element content of lime sludge samples and their mercury reemission could be identified. This result was likely due to the oxidative condition of the scrubbing process, which prohibited the reducing species from transforming the ionic mercury into elemental mercury.

Struvite precipitation from biogas digestion slurry using a two-chamber electrolysis cell with a magnesium anode

A novel, two-chamber electrolysis cell equipped with an ion exchange membrane and a magnesium anode was proposed in this study to recover phosphate as struvite from both the simulated and real biogas digestion slurry of swine wastewater. In the electrolysis experiments with the simulated slurry, the optimal pH and current density were determined to be 8.5 and 22.2 A m−2, respectively, achieving 95% phosphate removal efficiency and 100% current efficiency. The phosphate removal rate was mainly dependent on the magnesium dissolving rate. In the electrolysis experiments with the real digestion slurry, the pH of slurry increased from 7.4 to around 8.7 after the cathode-anode sub-section electrolysis without adding chemical reagents, achieving 93% phosphate removal efficiency at 22.2 A m−2. The phosphate removal efficiency could be kept constant in three consecutive electrolysis cycles with both the anion exchange membrane and the cation exchange membrane. The cost of the magnesium anode treatment for the real biogas digestion slurry for struvite recovery was estimated to be $81.57 kg−1 P, mainly resulting from the consumption of electricity and magnesium anode. The precipitates collected from all experiments were identified as struvite by the X-ray diffraction analysis.

A molecular dynamics study of nano-encapsulated phase change material slurry

Phase change material, which holds a good promise as a media of thermal energy storage, attracts more and more interest in the past decade. In this context, a classic all atom molecular dynamics approach was applied to investigate the thermodynamic properties of crystalline octadecane and octadecane–water slurry. The octadecane structure was established and heated up to study the melting behavior. The relationship between octadecane potential energy change and temperature was presented to determine the melting point. Heat capacity was evaluated to better understand the performance of energy storage system. We also performed the octadecane slurry simulations. The results suggested that the potential energy change of the slurry had a good agreement with lantern heat of octadecane. The pure water simulation was carried out to make a reference for octadecane–water slurry. It has been found that the heat capacity of octadecane slurry decreases with octadecane mass fraction increase. However, with heat absorbed during phase change, the slurry would provide larger heat capacity, which is beneficial to thermal energy storage system.

Long-time performance of a stainless steel crossflow filter with simulated Hanford tank waste

The long-time (>100h of operation) flux was measured for a set of five tests where nuclear waste slurry simulant was separated and continuously recycled using a stainless steel crossflow filter. The tests were conducted at various constant axial velocities and transmembrane pressures. In all five tests, the filter flux continued to decay at long times and did not reach a steady-state value. The long-time slope of the flux decay was unaffected by the axial velocity, but a larger transmembrane pressure resulted in a larger slope. Post-test examination of the filter did not show evidence of significant depth fouling. The experimental results are compared to theoretical predictions of the time to initiate cake formation and the time to reach steady-state predicted by models from the literature, both of which do not imply long-time phenomena would be expected. A more reasonable match between theory and experiment was achieved using a model based on the principles of dead-end filtration.

Effect of particle size distribution on slurry rheology: Nuclear waste simulant slurries

Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among these parameters, the particle size distribution of slurry is especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles in a low salt concentration. Our study suggests that the particle size distribution is a critical factor in understanding and controlling the rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy's Hanford and Savannah River sites, because the particle size distributions vary significantly for different types of nuclear waste slurries.

Quantitative analysis of slurry sample by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been employed for the analysis of slurry samples. Quantitative analysis of slurry samples is crucial and challenging. The problems associated with slurry samples include splashing, surface turbulence, and the difficulties of obtaining reproducible samples due to sedimentation. The LIBS analysis has achieved limited success due to inherent disadvantages when applied to slurry samples. In order to achieve improved measurement precision and accuracy, a spin-on-glass sampling method was evaluated. Five elements (Al, Ca, Fe, Ni, and Si) were examined in five slurry simulants containing varying amounts of each ion. Three calibration models were developed by using univariate calibration, multiple linear regression, and partial least square regression. LIBS analysis results obtained from the partial least square regression model were determined to be the best fit to results obtained from inductively coupled plasma optical emission spectroscopy analysis.

Stabilization and control of rheological properties of Fe 2O 3/Al(OH) 3-rich colloidal slurries under high ionic strength and pH

Significant decreases in yield stress of the AZ-101 pretreated HLW simulant slurry due to citric and polyacrylic acids.

Preliminary evaluation of laser induced breakdown spectroscopy for slurry samples

Laser-induced breakdown spectroscopy (LIBS) was applied to the analysis of simulant slurry samples used in the vitrification process of liquid radioactive wastes. A spectroscopic analysis was performed by two different detection systems: Czerny-Turner spectrometer coupled with intensified diode array detector (IDAD) and an Echelle spectrometer with intensified charge coupled device (ICCD). For the Czerny-Turner detection system, the normalized intensity method, which is the normalization of the atomic emission intensity by the released whole plasma emission area intensity, was employed to improve the reproducibility of LIBS signals. The Echelle detection system showed a high efficiency in simultaneous multi-element detection and determination of the physical quantities of the simulant.

Understanding the Effects of Dispersant Addition to Slurry Rheology using Laser Scanning Confocal Microscopy

The effectiveness of three dispersants to modify slurry rheology was examined using rheology measurements and laser scanning confocal microscopy (LSCM) in simulated waste solutions. All of the dispersants lowered the yield stress of the slurries below the baseline samples. The rheology curves were fitted reasonably to a Bingham Plastic model. The three-dimensional LSCM images of simulants showed distinct aggregates were greatly reduced after the addition of dispersants leading to a lowering of the yield stress of the simulated waste slurry solutions.

The Effects of Dietary Chicory and Reduced Nutrient Diets on Composition and Odor of Stored Swine Manure

<h2>ABSTRACT</h2> Two experiments were conducted to examine the impact of dietary chicory on growth performance and odor of stored swine manure. In Exp. 1, 180 nursery pigs (10.6 ± 2kg BW) were used in a 21-d experiment to evaluate the effects of replacing corn with chicory (0.5 to 10.0%) on pig performance. Overall, ADG increased (linear; P < 0.02) and ADFI tended to increase (P < 0.10) as the level of chicory increased in the diet. This effect was primarily due to numerically reduced performance when pigs were fed 0.5 or 1.0% chicory, with growth similar for pigs fed 0, 5, or 10%. In Exp. 2, 12 barrows (initially 59 ± 3kg BW) were fed each of 4 experimental diets during four 10-d periods in a replicated 4 × 4 Latin square design to compare nutrient excretion and odor analysis of pigs fed 1) conventional corn-soybean meal diet; 2) diet formulated to minimize nutrient excretion; 3) diet 1 with 10% chicory; and 4) diet 2 with 10% chicory. Feces and urine were collected and measured for N, S, and P excretion and retention, as well as for odor and gas analyses. Pigs fed diets formulated to reduce nutrient excretion had less (P < 0.001) total N and P excretion and had simulated slurry with reduced (P < 0.001) pH and less (P < 0.001) S, N, and ammonia. The addition of chicory to the diet also reduced (P < 0.03) N and P excretion. In conclusion, chicory can be fed to pigs to reduce nutrient excretion while maintaining growth performance.

Experimental Investigation and Numerical Simulation of Pad Stain Formation during Copper CMP

ABSTRACTExperiments and simulations were performed to investigate the characteristics of staining on pad surface. Experiments were performed on a table-top axisymmetric polishing system, consisting of a 12-inch non-rotating platen and a 4-inch rotating wafer carrier having the same center axis. Results showed that the stain deposited on each land area was found to be darker in the direction of wafer rotation and in the radial direction, suggesting that staining agent was produced by mechanical action during polishing and was advected downstream by the slurry flow. Generally, staining increased with polishing pressure, wafer rotation rate and polishing time. The simulated slurry velocity showed shear flow on the land areas and wafer-driven circulation in the grooves. Thermal model simulation showed 12 degree temperature rise on the reaction at the surface of wafer.

Aerosol Entrainment from a Sparged Non-Newtonian Slurry

Previous bench-scale experiments have provided data necessary for the development of empirical models that describe aerosol entrainment from bubble bursting. However, previous work has not been extended to non-Newtonian liquid slurries. Design of a waste treatment plant on the Hanford Site in Washington required an evaluation of the applicability of these models outside of their intended range. For this evaluation, aerosol measurements were conducted above an air-sparged mixing tank filled with simulated waste slurry possessing Bingham plastic rheological properties. Three aerosol-size fractions were measured at three sampling heights and for three different sparging rates. The measured entrainment was compared with entrainment models. One model developed based on bench-scale air-water experiments agreed well with measured entrainment. Another model did not agree well with the measured entrainment. It appeared that the source of discrepancy between measured and modeled entrainment stemmed from application beyond the range of data used to develop the model. A possible separation in entrainment coefficients between air-water and steam-water systems was identified. A third entrainment model was adapted to match experimental conditions and fit a posteri to the experimental data, resulting in a modified version that resulted in estimated entrainment rates similar to the first model.