Separation Of Solid Particles Research Articles

Editorial for Special Issue “Advances on Fine Particles and Bubbles Flotation”

The froth-flotation process allows for the separation of solid particles according to differences in their physical and surface-chemistry properties [...]

Research of the Wear Rate of Elements of the Flow Part of Centrifugal and Axial Pumping Units

The paper presents the results of a theoretical and experimental study of the wear rate of the elements of the flow part of centrifugal and axial pumps. Theoretical formulas recommended by various authors, obtained for models with flat samples based on energy theory, do not take into account the features of hydraulic machines. Considering the movement of solid particles in the inter-blade channels of the impellers of centrifugal and axial pumps, calculation schemes were chosen that correspond to the hydraulic and physical wear processes. The analysis shows that the influence of centrifugal and inertial forces in the inter-blade channel of the impellers of centrifugal and axial pumps causes separation and redistribution of solid particles in the flow. As a result, in centrifugal pumps in the end part of the blade and axial pumps in the end gap of the impeller, the local concentration of solid particles increases compared to the average. The work also provides dependencies for calculating the intensity of water-abrasive wear of pump working parts.

Analysis of characteristics of electric field-enhanced multi-gradient of solid particles in oil

Lubricating oil is easily polluted by solid particles, causing it to deteriorate; therefore, solid particles must be separated from the oil. Furthermore, as conventional filtration devices cannot meet both filtration accuracy and service life requirements, an oil and solid separation method for multi-gradient filtration enhanced by an electric field is proposed. A numerical model for multi-gradient separation was established by coupling the governing equations of electric and flow fields, the particle-wall collision equation, and the discrete phase-tracking equation. Enhanced by an electric field, the characteristics of the multi-gradient filtration of solid particles in oil were investigated using finite element method. The effects of the main control parameters on the filtration performance were analyzed. The results indicate that using the electric field-enhanced multi-gradient filtration method can achieve highly efficient separation of solid particles from the oil. When the electric field strength was increased from 0 kV/mm to 2 kV/mm, the deposition concentration of particles was 2.5 times higher and filtration efficiency of the system increased to 97.46%. Additionally, the deposition concentration and filtration efficiency decreased from 0.15 m/s to 0.3 m/s, while gradually increased from 0.3 m/s to 0.5 m/s, for a particle size range of 10–40 µm.

Numerical Investigation on the Performance of Cyclone Separators

Cyclone separators are commonly employed in the solid particle separation process due to their simplicity and low-cost manufacture. Collection efficiency and pressure drop are two of the most important factors. Small-size cyclone separator has outperformed collection efficiency. However, due to its small size, it’s hard to detailed flow investigation experimentally. So, the target of this work is to perform a numerical investigation of the flow characteristics as well as the collection efficiency and pressure drop of small cyclone separators, using Ansys Fluent software. Discrete Phase Model is included to simulate the particle-flow interaction. Different values of velocity inlet and particle size are considered. Typical flow characteristics of cyclone separators with a strong vortex are revealed. Results also show that the larger particle size or the stronger inlet velocity provides higher collection efficiency. Particularly, for a typical particle diameter of 2.96 micrometers, the collection efficiency of the cyclone separator is always higher than 91% when the inlet velocity surpasses 15 m/s. All these results provide a valuable framework for the operation of cyclone separators.

Analysis of the screening process of particulate material and the application of a grade efficiency curve as a function of screen length

Screening of powders is an important unit operation for industrial separation of solid particles, but to design equipment for a specific material requires considerable time and material, which encourages the use of mathematical models to predict or characterise the process. The goal is to represent the particle size separation during the process, to determine the screening efficiency using mathematical models with the fewest possible adjustable parameters. In this experimental study, a detailed analysis of the continuous screening process using multistage sampling was conducted and modified separation curve models were fitted. Well-known separation curve models were complemented by kinetic models, which became functions not only of the particle size, but also of the screen length T(x,l). These new models were successfully validated on experimental data. They provide a more complex characterisation of the process, due to the added length variable.

Effect of arc element diameter on fine particle collection efficiency of the separator

Clean gas without suspended particles is an essential factor for many industries. The paper is concerned with the design of a separation device with rows of the arc elements, in which a wave-like flow pattern is observed. The separation of solid particles from the gas occurs due to inertial and centrifugal forces. A three-dimensional model of the device and its operating principles are presented. The aim of the work is to numerically study the effect of the size of the arc elements of the separation device on the efficiency of particle collection. In the course of the simulation, the diameter of the arc elements varied from 25 to 50 mm. The exit to the stationary solution was estimated by the pressure drop of the separation device. It was found that about 870 iterations were needed. Results have shown that the diameter of the arc elements, at which the maximum efficiency of collecting particles from gas-solid flow occurs, is 40 mm. The separation efficiency of the device with a diameter of the arc elements of 25, 40, and 50 mm averages 81.1, 90.1, and 86.5%, respectively, at an inlet gas velocity of 0.5 to 5.0 m/s. The pressure loss in the separation device ranged from 12.6 to 1924.1 Pa at a gas velocity of 0.5 to 5.0 m/s. It is concluded that it is important to use a separation device to collect fine particles at a dusty gas velocity of less than 3 m/s because its pressure drop is significantly lower compared with other air separators.

Theoretical models and dependences for calculating intensity of hydroabrasive wear of pump working parts

The paper presents the results of a theoretical and experimental study of the wear intensity of the elements of the flow part of centrifugal and axial pumps. Theoretical formulas recommended by various authors, obtained for models with flat samples based on energy theory, do not consider the features of hydraulic machines. Considering the movement of a solid particle in the interblade channels of the impellers of centrifugal and axial pumps, we chose design schemes that correspond to hydraulic and physical wear processes. The analysis shows that the action of centrifugal and inertial forces in the interblade channel of the impellers of centrifugal and axial pumps results in the separation and redistribution of solid particles in the flow. As a result, in centrifugal pumps at the end of the blade and axial pumps at the end gap of the impeller, the local concentration of solid particles increases compared to the average. The paper also provides dependencies for calculating the intensity of hydroabrasive wear of pump working parts.

Numerical study of particles removal from dusty gas in separation device with straight arc-shaped elements

The paper presents an original design of the separator with straight rows of arc-shaped elements, which allows efficient separation of solid particles without significant abrasive wear of the device’s surfaces. A three-dimensional model of the device is developed, and the principle of its operation is described. In this paper, a numerical study of the capture of solid particles from a gas flow in the separation device is performed. It is found that at a relatively low inlet gas velocity (1 m/s), the separation efficiency of particles with a diameter of 20 to 100 μm is on average 78.9%. An increase in the inlet velocity of the dusty gas flow results in a decrease in the efficiency of the device for particles ranging in size from 25 to 80 μm. The pressure drop of the separator at a velocity of 1 m/s ranges from 45.5 to 95.4 Pa, and at a gas velocity of 4 and 7 m/s – from 740.8 to 4652.1 Pa. An increase in the number of straight arc-shaped elements from 4 to 12 and an increase in particle density from 3400 to 10000 kg/m3 leads to improved separation efficiency.

Optimal Configuration of Gas Solid Separation Equipment Using Mixed Integer Nonlinear Programming

The separation of solid particles from gas-solid process streams is an important unit operation in many chemical processes. Out of the many different types of separation equipment that are used for gas-solid separation, cyclone separators are widely used for their operational flexibility, efficiency and capital cost. This study focused on the design of an optimal configuration for several cyclones used in a fertilizer plant. The granulation step in the fertilizer plant leads to using different size cyclones and a different number of cyclones in series or parallel or a mix of both arrangements. A Mixed Integer Nonlinear Programming (MINLP) model is formulated to find the best cyclone arrangement with the optimal number of cyclones and dimensions from several combinations of 1D3D and 2D2D cyclones arranged in parallel-series for a high volume and heavy loading of solid particles. The objective function was to minimize the total cost, including the operating cost and the capital cost. The results indicated that a maximum of 90% efficiency is achieved with a parallel-series arrangement of 1D3D and 2D2D cyclones to be an optimal configuration for the maximum reduction in pollution level.

Extraction of Mathematical Correlations Applied in the Aerodynamic Separation of Solid Particles

This article describes the methodology used to identify the mathematical equation that describes the correlations between the input and output parameters of an experiment. As a technological process, aerodynamic separation was chosen to represent the behavior of a solid particle within an ascending vertical airflow. The experimental data were used to identify two parameters, namely the average linear velocity and the angular velocity. The Table Curve 3D program was used to develop a mathematical equation describing the dependence between the input parameters (the shape and size of the solid particle, as well as the velocity of the airflow) and the monitored parameters. A pyramid-type analysis (following a filtering system, a general equation was determined from a large number of equations that characterize an experimental set mathematically) was designed in order to determine a single mathematical equation that describes the correlation between the input variables and those obtained as accurately as possible. The determination of the mathematical equation started with the number of equations generated by the Table Curve 3D program; then, the equations with a correlation coefficient greater than 0.85 were chosen; and finally, the common equations were identified. Respecting the working methodology, one equation was identified, which has for the average linear velocity, a correlation coefficient r2 of between 0.88–0.99 and 0.86–0.99 for the angular velocity.

The Numerical Modeling of Gas Movement in a Single Inlet New Generation Multi-Channel Cyclone Separator

The work of traditional cyclones is based on the separation of solid particles using only the centrifugal forces. Therefore, they do not demonstrate high gas-cleaning efficiency, particularly in the cases where gas flows are polluted with fine solid particles (about 20 µm in diameter). The key feature of a new-generation multi-channel cyclone separator’s structure is that its symmetrical upgraded curved elements, with openings cut with their plates bent outwards, make channels for the continuous movement of the gas flows from the inflow opening to the central axis. The smoke flue of the vertical gas outflow is located near the cover of the separating chamber. The present work is aimed at studying the applicability of two various viscosity models and their modified versions to simulate aerodynamic processes in an innovative design for a multi-channel cyclone separator with a single inflow, using the computational fluid dynamics. The research results obtained in the numerical simulation are compared to the experimental results obtained using a physical model. The main purpose of this study is to provide information on how the new design for the multi-channel cyclone affects the distribution of gas flow in the cyclone’s channels. The modified viscosity models, k-ε and k-ω, and computational meshes with various levels of detailed elaboration were analyzed. The developed numerical models of a single-inlet multi-channel cyclone separator allow the researchers to describe its advantages and possible methods of improving its new structure. The developed models can be used for simulating the fluid cleaning phenomenon in the improved fourth-channel cyclone separator and to optimize the whole research process.

Challenges and development directions of membrane bioreactors operated on passenger ships in international shipping

In membrane bioreactor (MBR) technology, the activated sludge method is integrated with the separation of solid particles by ultrafiltration (UF). The technology ensures a high effluent quality, a shortened hydraulic retention time and a long sludge age that promotes slowly growing microorganisms and low sludge production. These advantages and the modular construction mean that MBRs have started to treat wastewater generated on passenger ships to adjust the treatment systems to the International Convention for the Prevention of Pollution from Ships. The aim of this paper is to present operational aspects of MBRs treating wastewater generated on ships, which are different from the aspects of MBR operation on land. This paper describes the consequences of separate treatment of gray wastewater (from showers, washing machines and kitchens) and black wastewater (from toilets), and of discontinuous flow of wastewater resulting from very high variability in the passenger numer and the use of the MBR as a ship ballast element. The possibility of introducing a water recovery technology using the existing infrastructure on passenger ships as well as the hybrid UF/reverse osmosis technology is presented. The findings demonstrated that gray effluent may be reused for marine main engine cooling jackets of high and low temperature, ship boilers or ship laundry.

Adjoint-based topology optimization of filter structures for gas–particle systems

Conventional filters for aerosol particle deposition consist of one or more filter layers, which are either woven or composed of tangled fibers. The quality of the separation results almost exclusively from the density of the fiber arrangement. Due to the manufacturing process, compromises between separation efficiency and pressure loss, which are in the opposite relationship to each other, are inevitable. The objective of this work is to develop a method for topology optimization to optimize filter structures for both higher filtration efficiency and lower pressure drop simultaneously using the adjoint method based on computation fluid dynamic simulations. The key to topology-optimized “bionic” filters is to find suitable cost functions controlling the optimization. These cost functions should take into account different separation mechanisms and pressure loss. The force coefficients for pressure and shear and the surface integrals of pressure and wall shear stress were evaluated for their contribution to the deposition as part of a combined cost function. In this work, a simple algorithm is devised to combine two opposing cost functions. First, promising results are obtained by considering solid particle separation from gas. For example, it was possible to increase the total filtration efficiency by 2% and reduce the pressure drop by 3.6% in one single deformation step.

Agglomeration of Solid Particles in Fluidized Catalytic Cracking Slurry Oil: Particle Separation by the Oil−Water Interface and Particle Composition Analysis

Separation of solid particles in fluidized catalytic cracking slurry oil (SLO) is a tricky task because of their distinctive composition. Centrifugation and the oil–water interface method were used...

A novel neural network approach to modeling particles distribution on vibrating screen

Screening is the most important operation for the separation of solid particles. The distribution of particles on the screen surface is an important factor affecting the screening performance. In this paper, a biological neural network (BNN) approach is proposed for modeling the distribution of particles on a vibrating screen surface. The dynamics of each neuron is characterized by the shunting equation, and the neural connection weights are properly defined according to the movement of particles under different vibration and structural parameters. Neural activities can propagate from the particles input neurons to the whole network through adjacent neural connections. When the iterative calculation is stable, the generated neural activity landscape is used to describe the particles distribution state.Discrete element method (DEM) simulations are carried out to obtain the particles screening processes and the corresponding distribution states. Then, the particles distribution models established using BNN are compared with that obtained by DEM simulations, and the similarities between them are improved by optimizing the BNN model coefficients. Similarity analysis results under different screening conditions show that the general correlation coefficient is higher than 0.9, which verifies the feasibility of the proposed BNN approach. Compared with the traditional kinetic and probability models, the BNN approach has obvious advantages in solving the modeling problem when the particles are fed to screen with multiple areas and non-uniform rate.

To Increase the Degree of Capture of Fine-Grained Dust Particles, the Development of a Mathematical Model of the Motion and Separation of Solid Particles during Dynamic Regeneration

To Increase the Degree of Capture of Fine-Grained Dust Particles, the Development of a Mathematical Model of the Motion and Separation of Solid Particles during Dynamic Regeneration

The Influence of Laser Ablation Parameters on the Holes Structure of Laser Manufactured Graphene Paper Microsieves

The graphene paper microsieves can be applied in the filtration of biological fluids or separation of solid particles from exploitation fluids. To produce graphene paper microsieves for specific applications, good control over fabrication should be achieved. In this study, a laser ablation method using a picosecond laser was applied to fabricate graphene paper microsieves. Holes in the microsieves were drilled using pulsed laser radiation with a pulse energy from 5 to 100 µJ, a duration of 60 ps, a wavelength of 355 nm, and a repetition rate of 1 kHz. The impact method was applied using 10 to 100 pulses to drill one hole. To produce holes of a proper diameter which could separate biological particles of a certain size (≥10 µm), optimum parameters of graphene paper laser ablation were defined using the MATLAB software taking into account laser pulse energy, repetition rate, and a desired hole diameter. A series of structural tests were carried out to determine the quality of an edge and a hole shape. Experimental results and Laguerre–Gauss calculations in MATLAB were then compared to perform the analysis of the distribution of diffraction fringes. Optimum experimental parameters were determined for which good susceptibility of the graphene paper to laser processing was observed.

Improving the separation process of fine particles in drilling mud by ultrasonic waves

Aggregation of solid particles in the drilling fluid has adverse effects on the drilling performance, including blocking drilling pipe, reducing fluid lubrication, and the blowout action. The purpose of this study was to prepare a solution for breaking the adhesion forces between the suspended solids and drilling fluid molecules. To investigate the effect of the ultrasonic waves on the separation of solid particles from reversed emulsion fluid, in vitro studies were conducted. Drilling mud was prepared in the form of different samples and the samples were then irradiated with ultrasonic waves for 2, 5, and 10 min and the intensities of 50, 100, and 150 W/m2. To evaluate the stability of the emulsions and the efficiency of the separation process, caliper (volumetric) and density measurement methods were utilized. The results revealed increased time and intensity of the ultrasonic radiation separates the phases and fine particles from the emulsion, and also increased the stability of reversed emulsion. The increased radiation time and intensity did not have any effect on the drilling mud and only delayed the optimal operation time and energy consumption.

Numerical investigation on the performance and flow pattern of two novel innovative designs of four-inlet cyclone separator

In solid particle separation process, cyclone separators are commonly used due to their simplicity and low-cost manufacture. A reference design S1 and two novel designs C4, N4 of four-inlet cyclone separator have been investigated computationally using the Reynolds Stress Model for turbulent flow and the Discrete Phase Model for tracking the particles. The numerical model has been validated and confirmed to be a reasonable good candidate for the investigation. The results show that, the design S1 provides the lowest average Euler number (4.415) and the design C4 provides the smallest average cut-off diameter (1.399 μm). As comparing the performances using weighted sum method, both two novel designs provide the better performance than the reference design S1. The innovative design N4 delivers the best performance which is 1 % and 0.1 % better in performance than S1 and C4, respectively.

Enhancement of particle collection efficiency considering the structural interplay: particle motion characteristics analysis

The vacuum-blowing cleaning system, utilizing positive and negative pressure mixed-delivery theory, has been adopted for the road sweeper vehicle. To enhance the solid particle separation performance and to evaluate the motion characteristics of inhaled particles under different structural parameters, the gas-solid flow in the vacuum-blowing cleaning system was investigated by using computational fluid dynamics (CFD) technology. The influence of the main structural parameters on the grade dust collection efficiency and average detention time of the inhaled particles was determined, such as suction-inlet diameter, suction-inlet inclination angle, and front baffle inclination angle. And the interplay between them was also investigated. In addition, a dust collection efficiency model was built, based on uniform design (UD) and multiple regression analysis (MRA), and subsequently verified via experiments. The results revealed that the structural parameters have significant influence on the dust collection performance. The suction-inlet diameter, front baffle inclination angle, and suction-inlet inclination angle exerted the highest, second-highest, and lowest influence, respectively. Furthermore, the interaction among structural parameters also influenced the collection performance. The highest, second-highest, and lowest levels of influence were determined for the inlet diameter/baffle inclination angle, inlet inclination angle/baffle inclination angle, and inlet diameter/inlet inclination interactions, respectively. The highest dust collection efficiency (i.e., 96.10%) and a short average detention time of particles in the chamber were realized under the following conditions: suction-inlet diameter and inclination angle: 200 mm and 110°, respectively, and front baffle inclination angle: 105°.