Mass transfer enhancement and hydrodynamic performance with wire mesh coupling solid particles in bubble column reactor

It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on bubble motion and gas-liquid mass transfer process in a bubble column.Particle image velocimetry(PIV)technology was employed to analyze the flow field and bubble motion behavior,and dynamic oxygen absorption technology was used to measure the gas-liquid volumetric mass transfer coefficient(kLa).The effect of embedding wire mesh,adding solid particles,and wire mesh coupling solid particles on the flow characteristic and kLa were analyzed and compared.The results show that the gas-liquid interface area increases by 33%-72%when using the wire mesh coupling solid particles strategy compared to the gas-liquid two-phase flow,which is superior to the other two strengthening methods.Compared with the system without reinforcement,kLa in the bubble column increased by 0.5-1.8 times with wire mesh coupling solid particles method,which is higher than the sum of kLa increases with inserting wire mesh and adding particles,and the coupling reinforcement mechanism for affecting gas-liquid mass transfer process was discussed to provide a new idea for enhancing gas-liquid mass transfer.

Experimental study on solid particle migration and production behaviors during marine natural gas hydrate dissociation by depressurization

Sand production is one of the main obstacles restricting gas extraction efficiency and safety from marine natural gas hydrate(NGH)reservoirs.Particle migration within the NGH reservoir dominates sand production behaviors,while their relationships were rarely reported,severely constrains quantitative evaluation of sand production risks.This paper reports the optical observations of solid particle migration and production from micrometer to mesoscopic scales conditioned to gravel packing during depressurization-induced NGH dissociation for the first time.Theoretical evolutionary modes of sand migration are established based on experimental observations,and its implications on field NGH are comprehensively discussed.Five particle migration regimes of local borehole failure,continuous collapse,wormhole expansion,extensive slow deformation,and pore-wall fluidization are proved to occur during depressurization.The types of particle migration regimes and their transmission modes during depressurization are predominantly determined by initial hydrate saturation.In contrast,the depressurization mainly dominates the transmission rate of the particle migration regimes.Furthermore,both the cumulative mass and the medium grain size of the produced sand decrease linearly with increasing initial methane hydrate(MH)saturation.Discontinuous gas bubble emission,expansion,and explosion during MH dissociation delay sand migration into the wellbore.At the same time,continuous water flow is a requirement for sand production during hydrate dissociation by depressurization.The experiments enlighten us that a constitutive model that can illustrate visible particle migration regimes and their transmission modes is urgently needed to bridge numerical simulation and field applications.Optimizing wellbore layout positions or special reservoir treatment shall be important for mitigating sand production tendency during NGH exploitation.

Influences of solid particles on the formation of the third phase crud during solvent extraction

The influences of solid particles in leach solution on the formation of the third phase crud during solvent extraction of copper were studied. Analyzed from the point of view of pH value and surface tension, the study results showed that the solid particle is one of the most important contributors for the formation of the third phase crud. During solvent extraction, if the pH value was greater than 2.30, the number of solid particles in the mother solution increased, in which case the possibility of forming the third phase crud could also increase, and the interface tension value might grow in pace with the quantity of the third phase crud.

Progress in Bio‑inspired Anti‑solid Particle Erosion Materials:Learning from Nature but Going beyond Nature

Solid particle erosion is a common phenomenon in engineering fields,such as manufacturing,energy,military and aviation.However,with the rising industrial requirements,the development of anti-solid particle erosion materials remains a great challenge.After billions of years of evolution,several natural materials exhibit unique and exceptional solid particle erosion resistance.These materials achieved the same excellent solid particle erosion resistance performance through diversified strategies.This resistance arises from their micro/nanoscale surface structure and interface material properties,which provide inspiration for novel multiple solutions to solid particle erosion.Here,this review first summarizes the recent significant process in the research of natural anti-solid particle erosion materials and their general design principles.According to these principles,several erosion-resistant structures are available.Combined with advanced micro/nanomanufacturing technologies,several artificial anti-solid particle erosion materials have been obtained.Then,the potential applications of anti-solid particle erosion materials are prospected.Finally,the remaining challenges and promising breakthroughs regarding anti-solid particle erosion materials are briefly discussed.

ON EQUATION OF DISCRETE SOLID PARTICLES' MOTION IN ARBITRARY FLOW FIELD AND ITS PROPERTIES

The forces on rigid particles moving in relation to fluid having been studied and the equation of modifications of their expressions under different flow conditions discussed, a general form of equation for discrete particles' motion in arbitrary flow field is obtained. The mathematical features of the linear form of the equation are clarified and analytical solution of the linearized equation is gotten by means of Laplace transform. According to above theoretical results, the effects of particles' properties on its motion in several typical flow field are studied, with some meaningful conclusions being reached.

A Test Study of 50% Lightning Impulse Breakdown Voltage on Rod-Plane Gap with Two-Phase Mixture of Gas and Solid Particles

A test study on 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has been carried out in a specially designed discharge cabinet. A mechanical sieve is set up for sifting different solid particles into the discharge space uniformly. The lightning impulse voltage according with international electro-technical commission （IEC） standard is applied to the electrodes inside the discharge cabinet by the rule of up-down method in a total of 40 times. The results showed that the 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has its own features and is much different from that in air.

Effect of solid particles on gear tooth failure

The failure of spur gears operating in highly contaminated media was studied. In fact, the effect of the presence of solid particles in gear mechanisms during surface tooth contact was observed. It is shown that the solid contaminants lead to significant wear in the first few operating cycles, in zones with a high rate of sliding. The scanning electron microscopy(SEM) images show clearly that the wear is more significant for a dry contact in the presence of larger size particles. Indeed, the presence of contaminants leads to an increase in friction, and therefore raises the temperature and the vibration levels when the operation of gear mechanism becomes very severe especially for a dry contact under the effect of larger size particles. On the other hand, we have tried to obtain a better understanding and a good description of wear debris distributions in gear mechanisms by using unimodal, single distribution models(Weibull and three-parameter Weibull).

Investigation of Movement and Deposition Behaviors of Solid Particles in Hydraulic Water Reservoir via the CFD‑DEM Coupling Method

Solid contamination existing as solid particles in power fluid transmission systems may lead to transmission performance reduction,system failures,and component damage.The hydraulic reservoir will deposit the contamination and store hydraulic fluid.To investigate its purification ability for solid contamination,experiments and simulations for the motion and deposition status of the typical hydraulic system particles are carried out to reveal the interaction of particles and fluid in hydraulic water reservoirs.The results show that the CFD-DEM coupling method could predict the accurate deposition position of iron particles and sand particles when ignoring the small-scale turbulence effect in the flow field.Besides,the particle motion traces and deposition patterns in the reservoir illustrate that the flow development on the bottom surface results in the particles turning,and particles tend to settle in the low flow energy position.The motion of particles is also linked to particles Stokes number,and the same-size sand particles are easily driven by the fluid.The contribution of this paper could provide a guide for predicting the particle motion and deposition pattern in the hydraulic reservoir.

RESEARCH ON STABILITY OF MOVING JET CONTAINING DENSE SUSPENDED SOLID PARTICLES

The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet far different downstream distances, Reynolds number of flow-field, particle properties and velocities of jetting device are got by the finite difference method based on the asymptotic method and the Eulerian conservative difference scheme. Founded on the analysis of the obtained stability curves it is found that the positive velocity of jetting device widens the unstable frequency range of flow-field hut the effect of the negative one is contrary. In addition, particles existing in the flow-field curb the instability of flow-field and the effect enhances with the decrease of Reynolds number of flow-field. These conclusions benefit learning the development of moving two-phase jet.

Numerical evaluation of virtual mass force coefficient of single solid particles in acceleration

Virtual mass force is an indispensable component in the momentum balance involved with dispersed particles in a multiphase system.In this work the accelerating motion of a single solid particle is mathematically formulated and solved using the vorticity-stream function formulation in an orthogonal curvilinear coordinate system.The total drag coefficient was evaluated from the numerical simulation in a range of the Reynolds number(Re)from 10 to 200 and the dimensionless acceleration(A)between2.0 to 2.0.The simulation demonstrates that the total drag is heavily correlated with A,and large deceleration even drops the drag force to a negative value.It is found that the value of virtual mass force coefficient(CV)of a spherical particle is a variable in a wide range and difficult to be correlated with A and Re.However,the total drag coefficient(CDV)is successfully correlated as a function of Re and A,and it increases as A is increased.The proposed correlation of total drag coefficient may be used for simulation of solid–liquid flow with better accuracy.

Lattice Boltzmann study of the interaction between a single solid particle and a thin liquid film

The isothermal single-component multi-phase lattice Boltzmann method(LBM)combined with the particle motion model is used to simulate the detailed process of liquid film rupture induced by a single spherical particle.The entire process of the liquid film rupture can be divided into two stages.In Stage 1,the particle contacts with the liquid film and moves into it due to the interfacial force and finally penetrates the liquid film.Then in Stage 2,the upper and lower liquid surfaces of the thin film are driven by the capillary force and approach to each other along the surface of the particle,resulting in a complete rupture.It is found that a hydrophobic particle with a contact angle of 106.7°shows the shortest rupture duration when the liquid film thickness is less than the particle radius.When the thickness of the liquid film is greater than the immersed depth of the particle at equilibrium,the time of liquid film rupture caused by a hydrophobic particle will be increased.On the other hand,a moderately hydrophilic particle can form a bridge in the middle of the liquid film to enhance the stability of the thin liquid film.

RESEARCH ON STABILITY OF INTERFACE OF JET CONTAINING SUSPENDED SOLID PARTICLES

The stability equation of interface of two-phase jet and the corresponding particle-gas disturbance velocity ratio equation are derived by means of the phase-coupled model. The stability nares of interface of two-phase jet for different particle properties and the corresponding particle-gas disturbance velocity ratio curves are given out through numerical computation. Further, several important conclusions on effect of particle property on growth and propagation of disturbance of interface of two-phase jet and particle disturbance property me presented on the basis of analyses of the obtained stability curves and particle-gas disturbance velocity ratio curves. These important conclusions can play a guiding role in studying development of two-phase jet and executing artificial controls over it in project practice.

EFFECT OF SUSPENDED SOLID PARTICLES ON UNSTABILITY OF TWO-DIMENSION MIXING LAYER

By considering the effect of suspended solid particles in the ordinary equations for two-dimension inviscid incompressible mixing layer, the Rayleigh equation and the modified Rayleigh equation are obtained. And then, by solving the corresponding eigen-value equations with numerical computational method, the relation curves between perturbation frequency and spacial growth rate of the mixing layer for the varying particle loading, ratio of particle velocity to fluid velocity and Stokes number are got. Sever al important conclusions on the effect of suspended solid particles on unstability of the mixing layer are presented in the end by analyzing all the relation curves.

LAGRANGIAN MODEL ON THE TURBULENT MOTION OF SMALL SOLID PARTICLE IN TURBULENT BOUNDARY LAYER FLOWS

The Lagrangian equations of motion of small particle in turbulent boundary layer flows, taking into account the effects of the drug force caused by the wall presence, the Saffman and the Magus lift forces et al., is studied. Using the spectral method, analytical expression relating to the Lagrangian power spectra of particle velocity to that of the fluid are developed and the results are used to evaluate various responses statistics. In this paper, the results clearly show that the turbulent diffusivity of the particle may be larger than that of the fluid for a period of long-time.

Effect of structural characteristics on the transport characteristics of solid particles in the thermal storage and release system of circulating fluidized bed

Coal-fired power generation stands as the most economically viable modulating power source in present-day China.It holds the potential to offer prospective solutions to the challenges posed by the rapid expansion of intermittent,unpredictable,and unstable renewable energy sources.Solid particle thermal storage technology emerges as an effective means to enhance the flexibility of coal-fired circulating fluidized bed power units.To attain an optimized structure for the solid particle thermal storage and release system in circulating fluidized bed units,experimental research was conducted on a 0.1 MWth circulating fluidized bed test platform.This study delved into the impact of ash storage bin geometries and the shapes of their feed-discharge valves on the control properties of solid particle transportation.The experimental outcomes reveal that employing inverted m-shaped valve and dual U-shaped valves for feed control,alongside U-shaped valves and N-shaped valves for discharge control,both enable efficient and rapid storage and release of solid particles within the circulating fluidized bed.Under similar air distribution conditions,the inverted m-shaped valve exhibits lower conveying energy consumption than the dual U-shaped valves,while the N-shaped valve excels in control characteristics over the U-shaped valve.Furthermore,the inverted m-shaped valve and the N-shaped valve demonstrate optimal overflow port heights,and the ash storage bin exhibits an optimum height-to-diameter ratio.

Effect of Air Distribution on the Transport Characteristics of Solid Particles in the Thermal Storage and Release System of Circulating Fluidized Bed

Solid particle heat storage technology offers a potential solution to the challenges posed by the significant growth of renewable energy sources,particularly in terms of grid security and stability.Consequently,it has the capability to optimize the energy utilization efficiency of the power system.In order to investigate the transport regulation characteristics of solid particles in the thermal storage and release system of a circulating fluidized bed(CFB),a test rig with a capacity of 0.1 MW(th)was established.This rig was utilized to systematically study the transport regulation characteristics of solid particles under the double U-type valve feed structure and U-type valve discharge structure.The experimental findings indicate that the system's design enables efficient and rapid storage and release of solid particles in the CFB.The air distribution mode,specifically the double U-type valve feed structure and the U-type valve discharge structure,significantly influence the feed and discharge characteristics of the ash storage bin.It was observed that the impact of loose air on these characteristics is more substantial than that of the return air,irrespective of the feed structure or the return structure.When adjusting the feed and discharge rate,it is recommended to adopt a scheme that involves coarse adjustment through loose air and fine adjustment through return air.

Mixing and segregation assessment of bi-disperse solid particles in a double paddle mixer

A double paddle blender's flow patterns and mixing mechanisms were analyzed using discrete element method(DEM)and experiments.The mixing performance of this type of the blender containing bi-disperse particles has been rarely studied in the literature.Plackett-Burman design of experiments(DoE)methodology was used to calibrate the DEM input parameters.Subsequently,the impact of the particle number ratio,vessel fill level,and paddle rotational speed on mixing performance was investigated using the calibrated DEM model.The mixing performance was assessed using relative standard deviation and segregation intensity.Mixing performance was significantly affected by the paddle rotational speed and particle number ratio.Moreover,the Peclet number and diffusivity coefficient were used to evaluate the mixing mechanism in the blender.Results revealed that the diffusion was the predominant mixing mechanism,and the best mixing performance was observed when the diffusivity coefficients of 3 mm and 5 mm particles were almost equal.

Dynamic simulation and parametric influence analysis on thermal performance of a quartz tube solid particle receiver in solar tower power plants

Due to a higher operating temperature(≥800 ℃),Solar Particle Receiver(SPR)which uses particles as the working medium is considered as one of best candidates to improve the thermoelectric conversion efficiency of concentrating solar power plants.In this paper,a quartz tube solid particle receiver model is fully developed by using the discretized lumped parameter method,in which the calculation process of particle temperature and thermal loss is clearly given.In order to improve the manipulation level of particle receiver during the operation,the dynamic characteristics of the quartz tube particle receiver are comprehensively studied by the disturbance test of selected input parameters.Besides,in order to grasp the influence rule of key parameters on the thermal performance of particle receiver,the key parameters'sensitivity analysis is also deeply studied.The results show that the particle outlet temperature can reach as high as 810 ℃ under a relatively small value of solar flux 600 kW/m^(2),but the receiver efficiency is only about 75%;Besides,the receiver efficiency shows a variation tendency that it rises first falls afterwards with the increase of incident solar flux.The validity of proposed model is verified by a heating experi-mental system with a single quartz tube,and the relative error is not more than 7.9%.The research results are beneficial for understanding the dynamic characteristics and designing the particle receiver.

Numerical simulation of a dense solid particle flow inside a cyclone separator using the hybrid Euler-Lagrange approach

This paper presents a numerical simulation of the flow inside a cyclone separator at high particle loads. The gas and gas–particle flows were analyzed using a commercial computational fluid dynamics code. The turbulence effects inside the separator were modeled using the Reynolds stress model. The two phase gas–solid particles flow was modeled using a hybrid Euler–Lagrange approach, which accounts for the four-way coupling between phases. The simulations were performed for three inlet velocities of the gaseous phase and several cyclone mass particle loadings. Moreover, the influences of several submodel parameters on the calculated results were investigated. The obtained results were compared against experimental data collected at the in-house experimental rig. The cyclone pressure drop evaluated numerically underpredicts the measured values. The possible reason of this discrepancies was disused.

Solid-particle erosion behavior of cast alloys used in the mining industry

The erosive-wear response of five commercial ferrous-based cast alloys used for crushing was examined in this study. The micro- structures of the alloys were modified to elucidate the effect of microstructural features on wear. Erosion tests were conducted using alumi- num oxide particles （90-125μm） at 70 m/s and a normal impact angle （90°）. The worn surfaces were characterized by scanning electron microscopy and 3D non-contact laser profilometry. It is found that （i） a pearlitic structure exhibiting a greater plastic deformation than both bainitic and martensitic structures shows the greatest resistance to erosive wear at normal impact and （ii） the fracture characteristics of carbide and graphite particles plays an important role in determining the erosion wear behavior of the cast alloy matrices.