Solid Phase Particles Research Articles

Method to concurrently measure local gas and solid holdups visually with higher precision in circulating fluidized bed

AbstractSimultaneous and visual measurements of local gas and solid phase holdups with high‐precision in a gas–liquid–solid circulating fluidized bed is of great importance for the design and scale‐up of such a reactor. However, such measuring techniques are still limited due to the difficulty of discrete phase identification of gas bubble and solid particle phases in the complex three‐phase flow. Immersed telecentric camera method developed based on the digital image processing is such a measuring technique, but its measuring precision is to be improved due to the existing three problems in the depth‐of‐field particle extraction, reconstruction of dim bubbles, and counting of overlapping particle clusters. This work has solved these problems by developing corresponding algorithms and the relative errors of measured solid holdup and gas holdup are as low as 0.3% and 1.0%, respectively.

Plasma-solution synthesis of particles containing transition metals

The paper proposes a new method for the synthesis of powders containing transition metals using a plasma-solution system. The reactor was an H-shaped glass cell, the two parts of which were separated by a cellophane membrane. A discharge consisting of two discharges - with a liquid cathode and a liquid anode - a high voltage is applied to titanium electrodes located above the surface of the solution. Aqueous solutions of zinc, iron, cadmium, cobalt, nickel, and copper nitrates were used as the liquid phase. Under the action of the discharge on the liquid anode, in the region of contact of the discharge with the solution the formation of a colloidal suspension was observed. The kinetics of the process of synthesis of solid-phase particles in solution under the action of a discharge have been studied. The chemical composition and morphology of the formed solid phase have been established. The mechanisms of chemical reactions occurring in the solution under the action of plasma, and the mechanisms of formation of transition metal oxides in the process of calcining the synthesized powders have been proposed.

Theoretical and Experimental Analysis of the Change in the Solid-Phase Particle Distribution in Process Equipment

Theoretical and Experimental Analysis of the Change in the Solid-Phase Particle Distribution in Process Equipment

Clinical validation of automated and rapid mariPOC SARS-CoV-2 antigen test

COVID-19 diagnostics was quickly ramped up worldwide early 2020 based on the detection of viral RNA. However, based on the scientific knowledge for pre-existing coronaviruses, it was expected that the SARS-CoV-2 RNA will be detected from symptomatic and at significant rates also from asymptomatic individuals due to persistence of non-infectious RNA. To increase the efficacy of diagnostics, surveillance, screening and pandemic control, rapid methods, such as antigen tests, are needed for decentralized testing and to assess infectiousness. A novel automated mariPOC SARS-CoV-2 test was developed for the detection of conserved structural viral nucleocapsid proteins. The test utilizes sophisticated optical laser technology for two-photon excitation and individual detection of immunoassay solid-phase particles. We validated the new method against qRT-PCR. Sensitivity of the test was 100.0% (13/13) directly from nasopharyngeal swab specimens and 84.4% (38/45) from swab specimens in undefined transport mediums. Specificity of the test was 100.0% (201/201). The test's limit of detection was 2.7 TCID50/test. It showed no cross-reactions. Our study shows that the new test can detect infectious individuals already in 20 min with clinical sensitivity close to qRT-PCR. The mariPOC is a versatile platform for syndromic testing and for high capacity infection control screening of infectious individuals.

Following performance of solid particle and liquid phases inside a hydrocyclone

ABSTRACT The following performance between solid particle and liquid phases inside a hydrocyclone remains unclear. The purpose of this paper was to study the following pattern of solid-liquid phases in a hydrocyclone, and to explore the influencing factors affecting solid-liquid followability. Numerical simulation of the effects of seven particle sizes, two particle concentrations and two feed rates on solid-liquid followability were performed. The results from the simulation show that in the axial and tangential directions, the relative velocity difference between the particles and the liquid flow is almost zero. Thus, the followability of the particles and the liquid flow is very good and is not affected by the particle size, concentration or feed rate. In the radial direction, the particle size, particle concentration, and the feed rate have a great impact on the followability of the particle and liquid flows. The followability of particle flow and liquid flow is lower at larger particle size, lower slurry concentration, and higher feed rate. This indicates that the separation of the particles from the liquid flow is easier when the particle size is large, the slurry concentration is low, or the feed rate is high.

Erosion wear characteristics of cemented carbide for mud pulser rotor

Mud pulser is the most commonly used Measurement While Drilling(MWD) instrument for downhole data transmission to the surface. The rotor of the key component of the mud pulser is made of cemented carbide material. Under the action of high speed mud erosion containing solid phase, the rotor will produce erosion wear and reduce the quality of signal transmission. To explore the erosion wear mechanism of rotor carbide in mud containing solid phase particles, the influences of different erosion angles and different erosion abrasive sizes on the erosion wear properties of cemented carbides were studied by taking quartz sand as erosion abrasive. By means of surface profilometer, scanning electron microscope (SEM) and energy spectrum analysis (EDS), the erosion wear mechanism of cemented carbide was revealed. The experimental results show that the erosion wear rate increases gradually with the increase of erosion angle. When the erosion angle is 90°, the maximum average erosion rate of WC-5Co, WC-6Co and WC-10Co cemented carbides is 2.39%, 2.42% and 3.22%, respectively. With the increase of the abrasive particle size, the erosion wear rate of the material increases first and then decreases. When 100–200 um, the maximum average erosion rates of WC-5Co, WC-6Co and WC-10Co are 1.84%, 1.98% and 2.48%, showing a significant “particle size effect”. At low erosion angle, the wear mechanism is furrow and cutting mark, while at high erosion angle, the wear mechanism is pit. The erosion wear mechanism of small particle size abrasives is that a large area of surface layer falls off in the erosion area. The erosion wear mechanism of large particle size abrasive is the material loss in the erosion pit in the erosion area.

Experimental and Theoretical Study of the Axial Distribution of Solid Phase Particles in a Fluidized Bed

The article presents the results of computational and experimental studies of the distribution of a model material (plastic spherical particles with a size of 6 mm) along the height of a laboratory two-dimensional apparatus of the fluidized bed of the periodic principle of action. To experimentally determine the distribution of the solid phase over the height of the apparatus, digital photographs of the fluidized bed were taken, which were then analyzed using an algorithm that had been specially developed for this purpose. The algorithm involved splitting the image by height into separate rectangular areas, identifying the particles and counting their number in each of these areas. Numerical experiments were performed using the previously proposed one-dimensional cell model of the fluidization process, constructed on the basis of the mathematical apparatus of the theory of Markov chains with discrete space and time. The design scheme of the model assumes the spatial decomposition of the layer in height into individual elements of small finite sizes. Thus, the numerically obtained results qualitatively corresponded to the full-scale field experiment that had been set up. To ensure the quantitative reliability of the calculated forecasts, a parametric identification of the model was performed using known empirical dependencies to calculate the particle resistance coefficient and estimate the coefficient of their macrodiffusion. A comparison of the results of numerical and field experiments made us possible to identify the most productive empirical dependencies that correspond to the cellular scheme of modeling the process. The resulting physical and mathematical model has a high predictive efficiency and can be used for engineering calculations of devices with a fluidized bed, as well as for setting and solving problems of optimal control of technological processes in these devices for various target functions.

Regulation of Rheological Properties of Three-Phase Dispersed Systems Used for the Production of Building Materials

The paper considers the relationship of the rheological properties of three-phase dispersed systems with capillary coupling and, on this basis, substantiates the possibility of directional regulation of the rheological properties of raw materials for the production of building materials. It is shown that the rheological properties of two-phase dispersed systems are determined mainly by the action of intermolecular forces in the liquid-filled contact zones of solid phase particles, and in three-phase systems – by the action of capillary coupling forces.

Study of critical suspension speed of impeller in two paddles stirred kettle

Experiments and numerical simulations were used to study the two-layer paddle stirring system. Glass bead particles and aqueous polyvinyl alcohol solution were used as the solid-liquid phases, and the variation of the critical suspension speed of impeller Njs under different parameters was analyzed by testing the parameters of liquid phase viscosity, solid phase particle size, and solid-phase mass fraction. The results showed that the main resistance (surface viscous resistance) increased with the increase of liquid-phase viscosity at particle size d=0.3 and d=0.5 mm, and this factor inhibited the solid-phase diffusion, resulting in an increasing trend of Njs with the increase of liquid-phase viscosity. At particle size d=0.8 and d=1mm, the main resistance (gravity) is not related to the liquid phase viscosity, and the intensity of turbulent pulsation in the kettle is enhanced with the increase of liquid phase viscosity, which is favorable to the solid phase diffusion, and Njs decreases with the increase of liquid phase viscosity. The increase in solid-phase volume fraction increases Njs.

DEVELOPMENT OF UNIVERSAL - ADJUSTABLE HYDROCYCLONE NOZZLE

A hydrocyclone is a technological apparatus designed to separate solid phase particles of a given size and density from a liquid flow . Structurally, a hydrocyclone is a capacitive apparatus, consisting of a central part - a cylindrical shape and a conical bottom.

Raman spectroscopic study of irregular network in the process of glass conversion to CaO-MgO-Al2O3-SiO2 glass-ceramics

The effect of nucleating agent on the amorphous phase results in the change of structure and properties of glass-ceramics. Raman spectroscopic is introduced in the progress of transformation from glass to glass-ceramics with different doping Cr2O3 (with 0wt%, 0.2wt%, 0.4wt%, and 0.6wt%). The polymerization degree of the glass-network decreases with adding of nucleating agent, or heating treatment of nucleating. The total percentage of content Q2 (the glass-network with n bridged oxygens, n = 0, 1, 2, 3, 4) and Q4 is decreased by 19.55% and depolymerizes into Q1 and Q3 with the occurrence of the glass-network being damaged, which promotes the occurrence of phase separation at high temperature. Raman mapping displays that the surface or shape wall of solid phase particles for heterogeneous nucleating, and Si-O bonds in amorphous structure will transform into a crystalline structure skeleton. The Raman spectroscopy and Raman mapping have important applications in understanding structural transformation from amorphous to crystal.

Numerical Study on Particle Deposition Characteristics of Impingement Effusion Cooling Structure

The paper investigates the effect of impingement velocity and particle diameters on the flow and solid-phase deposition characteristics of the impingement effusion cooling structure by numerical simulation of gas-solid two-phase flow using DPM with UDF. The results show that under the same condition of the particle diameter, both the particle deposition flux and the particle deposition rate become increase with the increasing of the impingement velocity while the dimensionless particle deposition rate increases first and then decreases; Under the same condition of the impingement velocity, with the increase of the particle diameter, the particle deposition flux increases, while the particle deposition rate and the dimensionless deposition rate of the particle both increase first and then decrease. Taken together, Brownian motion of particles, turbulent diffusion, and particle inertia and flow characteristics is the main factors that affect the solid-phase particle deposition behaviour.

ПРОБЛЕМЫ РАЗВИТИЯ ЛИТЬЯ ПОД ДАВЛЕНИЕМ ТВЕРДОЖИДКОГО МЕТАЛЛА В РОССИИ

The methods of powder and granular metallurgy are rapidly improving, granulation and spheroidization of solid phase particles is carried out “in–situ” at the stage of alloy preparation, which precedes the casting stage, and on this basis, a new generation of technologies is born and developed. dubbed Thixo – (casting, molding, forming) and PowderInjectionMolding (РIM (МIM, СIM)) technologies. All of the above technologies are united by the term Semi–Solid Processing (SSP), and the mandatory code prefixes Semi–Solid Metal (SSM) and MetalInjectionMolding (MIM) have appeared in the designations of alloys prepared for processing in a solid–liquid state.

Research and analysis of processes occurring during abrasive wear of materials with heterogeneous cementitious structures

The article considers the impact of hardness and the number of solid-phase inclusions, as well as the properties of steels with ferritic, austenitic and martensitic matrices with heterophase cementitious structures on wear resistance. It is demonstrated that to ensure high wear resistance and impact toughness, solid phase particles in the structure of a heterophase metal material must be isolated from each other by sections of a relatively viscous matrix. Such structures can be obtained on the surface of a part or tool by surfacing, chemical-thermal treatment, and other methods. The results of calculations of the hardness of steel with different content of the carbide phase in its structure and the specific strain energy absorbed by the cementitious layer from the relative content of carbides in the ferritic, austenitic and martensitic matrices are presented. The contribution of carbide particles to determining the level of wear resistance of a two-phase material with different amounts of them in steels with different matrices is evaluated.

Three-dimensional Voronoi analysis of realistic grain packing: An XCT assisted set Voronoi tessellation framework

Voids play an important role in both transport properties and mechanical deformation of a granular material. It remains challenging to quantify void spatial distributions, especially in realistic granular packing with irregular grain shapes. This paper presents a three-dimensional (3D) framework for Voronoi analysis of realistic grain packing, based on a combination of modern X-ray computed tomography (XCT), quantitative image processing and computer simulation using the discrete element method (DEM). We also introduce an efficient and robust parallel processing tool, PySVT, based on Set Voronoi tessellation (SVT). 3D reconstruction of a realistic Ottawa sand assembly is conducted, and two numerical packings of ellipsoidal and spherical particles are generated to reproduce the structure of the realistic packing with the same grain size distribution and global void ratio (or porosity). A further comparison is made for a class of microstructural properties among these packings. For the solid (particle) phase, analyses of particle shape characteristics and contact network indicate statistically significant deviation occurs between 2D and 3D particle characteristics, in particular sphericity and roundness. The analyses for the void phase place an emphasis on the morphology of Voronoi cells and the local porosity. A log-normal distribution is found to describe well both the local porosity and the reduced surface area of Voronoi cells, which is in agreement with observations for numerical packings of non-realistic grains.

Evolution and Physical Characteristics of a Raceway Based on a Transient Eulerian Multiphase Flow Model

In industrial processes, a semi-cavity area formed by airflow wherein the particles circulate is called a “raceway”. In a blast furnace, the role of the raceway is particularly important. To understand and predict the evolution and physical characteristics of the raceway, a three-dimensional transient Eulerian multiphase flow model in a packed particle bed was developed. In the model, it was assumed that the gas and solid (particle) phases constitute an interpenetrating continuum. The gas-phase turbulence was described as a k–ε dispersed model. The gas-phase stress was considered in terms of the effective viscosity of the gas. The solid-phase constitutive relationship was expressed in terms of solid stress. It was found that the evolution process of the raceway can be divided into three stages: (1) rapid expansion, (2) slow contraction, and (3) gradual stabilization. When the blast velocity was increased from 150 m/s to 300 m/s, the surface area of the raceway increased from 0.194 m2 to 1.644 m2. The depth and height of the raceway increased considerably with velocity, while the width slightly increased.

Frequency Transition from Diffusion to Capacitive Response in the Blocked-Diffusion Warburg Impedance for EIS Analysis in Modern Batteries

The use of the Blocked-diffusion Warburg (BDW) impedance within electrochemical impedance spectroscopy (EIS) measurements can unveil diffusion properties of the electroactive material of modern batteries at different states-of-charge. The impedance response of the BDW comprises a diffusion response of charge carriers through a short-diffusion distance (e.g. the solid-phase in electroactive material of battery electrodes) and a capacitive response due to accumulation of charge carriers in a blocked-interface (e.g. impermeable current collector of a thin film electrode). This study has developed a mathematical expression based on the Newton-Raphson iteration method to calculate the frequency and time constant during the transition from diffusion to capacitive response in the BDW impedance. The mathematical procedure to calculate the frequency during the diffusion-capacitive transition response in the BDW has been written in a script in Matlab® software and is applied to BDW impedance responses reported in previous studies and extracted from EIS measurements in Li-ion and NiMH batteries. This study demonstrates that the time constant during the transition from diffusion to capacitive response in the BDW differs from the characteristic time constant commonly represented in the BDW mathematical expression. The characteristic time constant represented in the BDW mathematical expression is related to the rate of accumulation of charge carriers in the blocked-interface of the electrode. On the other hand, the time constant during the transition from diffusion to capacitance responses in the BDW impedance can be related to diffusion properties in solid-phase particles with heterogeneous size distribution in the electroactive material of modern battery electrodes.

An error-controlled adaptive time-stepping method for particle advancement in coupled CFD-DEM simulations

Coupled Computational-Fluid-Dynamics (CFD) and Discrete-Element-Method (DEM) models provide an accurate description of multiphase physical systems where a solid granular particle phase exists in an underlying gaseous continuous medium. The time integration of the granular phase in these simulations is typically handled using an explicit scheme with a constant time-step among all particles that is invariant in time to resolve inter-particle collisions. A locally third-order accurate adaptive time integration technique for particles that employs an embedded locally second-order scheme for error determination is presented in this work. The particle time-step size is dynamically adapted based on solution error, thus leading to significant savings in computational time. The efficacy of our scheme is quantified using four test cases of varying complexity (binary collision, homogeneous cooling system, fluidized bed and hopper discharge). The adaptive time-stepping method exhibits improved performance (~ 2–3 times in most of the cases studied) compared to three commonly used non-adaptive time-step methods (first-order Euler-explicit, second-order Adams-Bashforth and third-order Runge-Kutta schemes), while maintaining the same level of accuracy and parallel scalability.

Changes in relative permeability curves for natural gas hydrate decomposition due to particle migration

It is very important to study the fluid flow in a natural gas hydrate (NGH) reservoir for hydrate exploitation. During the decomposition of NGH, some particles fall off and flow with the fluid as a result of poor cementation, which usually leads to sand production in the hydrate mining process. In this study, a three-dimensional pore network model (PNM) was established to simulate the three-phase flow of the gas phase (CH4), water phase, and solid phase (particles). Relevant parameters were set considering the deposition, blockage, and flow in the process of particle migration. Then, the gas–water relative permeability curves under different hydrate saturations, particle diameters, and particle numbers were obtained, considering the influence of the change in the pore-throat space during the hydrate decomposition process. The results showed that the gas–water relative permeability equal points (isotonic points) first turned toward the left and then to the right. The analysis results showed that particle deposition and blockage mainly influenced the relative permeability curves during the early period of the hydrate decomposition process. An increase in the pore-throat space was the main factor affecting the relative permeability curves in the late period of the hydrate decomposition process. Moreover, increasing the particle diameter and number of particles caused the isosmotic points of the relative permeability curves moving to the left as a whole because the pore-throat space decreased. Increasing the number of particles first affected the fluid flow in the hydrate reservoir when the temperature was 280 K, pressure was 5.76 MPa, and hydrate saturation was 0.48. In the actual hydrate mining process, this could cause sudden changes in the relative permeability and production. Thus, this condition needs to be avoided. It has important significance in reference to the process of hydrate mining with sand production.

INLET TEMPERATURE INFLUENCE ON ISOTHERMAL GAS CLEANING FROM MONO-IMPURITIES BY FIXED LAYER OF ADSORBENT

The influence of the temperature of the inlet gas containing mono-impurity was evaluated for the process of physical adsorption purification in a porous fixed bed of granular adsorbent. The theoretical analysis is based on the classical mathematical model of the isothermal adsorption dynamics in a porous stationary medium structurally made-up of the dispersed phase of solid particles, under the assumptions made: the gas to be purified contains a low-concentration mono-impurity, its motion in the adsorber is unidirectional, and the levelling effect of the velocity profile in the porous cross section environment allowed to adopt the hydrodynamic regime of plug flow; axial mixing in the gas flow is negligible; the adsorption heat is negligible; the layer porosity is uniform; adsorption rate is determined by the sorption kinetics equation with an isotherm, obeying Henry's law. An initial-boundary-value problem is formulated for a system of first-order partial differential equations, which solution with respect to mono-impurity concentrations in the gas stream and adsorbent is obtained in an explicit analytical form using the one-sided integral Laplace transform. A comparative analysis of the computational experiment results with known experimental data showed that the proposed model with an assumptions system is quite adequate qualitatively and quantitatively describes the adsorption separation process. Using the example of an industrial adsorber functioning in the ZB-120/120 complex purification unit in a mobile gas production system, it is shown that the temperature increase by 10 K of inlet dried air after compression containing carbon dioxide reduces the working time in the adsorption stage by 45%. It has been established that the temperature change in the gas inlet flow has a significant effect on the adsorber efficiency and should be taken into account when identifying the overall characteristics of the complex cleaning unit.