Solid Mass Flow Rate Research Articles

Gas-Solid Flow Behavior in a Pneumatic Conveying System for Drying Applications: Coarse Particles Feeding with a Venturi Device

The feeding of coarse particles (>0.5 mm diameter) directly into a riser operating at positive pressure is important for drying and pre-heating applications. The presence of the feeding device can lead to heterogeneity of drying and heating, and is the main factor responsible for pressure loss in short conveying systems. However, there is a lack of information concerning the axial and radial distributions of coarse particles in this type of configuration, despite the recent advances when dealing with fine particles (FCC catalyst). The present work therefore investigates a vertical venturi feeder with the conveying system operating in dilute-phase regime with 1 mm spherical glass particles. Experimental assays revealed the behavior of the mass flow rate of solids in the system, and pressure measurements were made along the riser in order to evaluate the accuracy of simulations. Euler-Euler simulations provided close estimation of the experimental pressure drop and the pressure drop according to distance in the linear region. Simulation of the fluid dynamics in the riser showed that solids clusters were formed at low concentrations near the feeding device, reflecting heterogeneity in the solid phase volume fraction.

Estimation of Particle Rotation in Fluidized Beds by Means of PTV

Fluidized bed granulation is a widely used process to produce pharmaceuticals, food and fertilizer. The achievable product quality, for example the uniformity of the formed layer or the size of the agglomerates, inherently depends on the particle dynamics in the bed. Generally, the solid phase velocity field is used to determine characteristic particle times (turn-over and residence time) in different zones of a spray fluidized bed. This information can be acquired using particle image velocimetry (PIV) together with digital image analysis (DIA) as for example in Börner et al. (2011, 2013). In order to derive certain quantities, such as particle mass flow rates, the measurement results are averaged in space and time, which is directly associated with a loss of information. However, an alternative is available when using the Lagrangian particle description (particle trajectories and local particle velocities) in terms of particle tracking velocimetry (PTV). Particle velocities are estimated on the basis of identifying individual particles, leading to exact particle mass flow rates. There are known shortcomings with this method for dense particulate flows, in particular ambiguities during particle identification. These problems have been fixed to a certain extent, for example using colored tracer particles (Natarajan et al., 1995, Bendicks et al., 2011) or recognition of flow pattern (Capart et al., 2002). The former approach yields a low resolution, but ensures reasonable results for particle velocities and associated trajectories. Additionally, it is possible to obtain information concerning the particle rotation, when using traces with an adequate color pattern (e.g. Zimmermann et al., 2011). Therefore, we used half-page blackened tracer particles in order to estimate particle velocities and particle rotation simultaneously and unambiguously within 2D-fluidized bed. Solid mass flow rates and particle residence times can be derived from the local particle velocities. At the same time, the observation of discontinuous particle tracks together with the quantification of the particle rotation can be used to foster the insight and understanding of particle-particle contact and the associated momentum transfer in dense gas-solid multiphase flows. Eventually, we can obtain local particle collision rates and corresponding changes of normal and angular momentum of individual tracer pairs.

Performance of vertical diffusers carrying Gas-solid flow: experimental and numerical studies

In the present work, numerical and experimental studies are carried out to investigate the performance of vertical straight-walled conical diffusers carrying air-solid two-phase flow. Eulerian-Lagrangian approach is used to numerically simulate the two phases using the Chen-Kim k-ε turbulence model. The continuous phase (gas) is simulated using Eulerian frame by solving Reynolds-Averaged Navier-Stokes equations (RANS), while the dispersed phase (solids) is simulated using particle tracking method. Coupling between the two phases is established by adding particle source terms and void fraction in the continuous phase equations. A 4-way coupling is adapted to include the effect of particle-particle collisions. Lift forces, particle dispersion and particle-wall collisions are also considered in the simulation of solid-phase. The experimental study is carried out on a pilot scale vertical pneumatic transport system. Four different diffuser geometries are tested at various inlet-Reynolds numbers and mass loading ratios. Sand particles of different sizes and mass flow rates are used to represent the solid phase. Comparisons between numerical predictions and experimental results indicated good agreement. The effects of solid parameters are significant for small angled-diffusers and decrease as the diffuser angle increases. It is also found that, there is a significant decrease in the separation zone within diffuser due to the presence of solid particles. Energy is transferred from the gas phase to the solid phase in the upstream pipe. This energy is transferred again to the gas phase through the diffuser and its downstream tangent pipe. The rate of energy transfer is enhanced by increasing the solid mass flow rate and decreasing the particle size. The results show that the mass loading and size of solid particles have significant effects on the diffuser loss coefficient.

Simulation of the heterogeneous semi-dry flue gas desulfurization in a pilot CFB riser using the two-fluid model

Simi-dry flue gas desulfurization (FGD) in a pilot circulating fluidized bed (CFB) reactor was studied by the CFD method. Heterogeneous hydrodynamics and desulfurization reaction were simulated in a three-dimensional domain of the CFB riser. Euler–Euler approach was adopted and the O–S drag model was utilized for the unsteady gas–solid two-phase flow, which achieved the typical core-annulus structure of both the particle concentration and the particle velocity. The collision coefficient (e) was selected by comparing with the experimental data of the solid volume fraction. The desulfurization was described by the continuous conversion model and the liquid film thickness equation for interphase mass transport was modified to avoid “divided by zero”. Detailed analysis figured out that the water mass fraction in the particle phase played a significant role in the desulfurization. The sorbent dissolving might be a controlling step when the water mass fraction was very small, and should be taken into consideration rather than neglected. Operating parameters were discussed for their impact on the desulfurization efficiency. Computational results showed that the jet water flow rate was the most significant parameter as the circulating solid mass flow rate followed closely behind, suggesting that uniform water jetting will be the most improving method.

Experimental study of the blockage boundary for dense-phase pneumatic conveying of powders through a horizontal slit

The estimation of the blockage boundary for pneumatic conveying through a slit is of significant importance. In this paper, we investigate the characteristics for blockage of powder (48μm average diameter) through a horizontal slit (1.6m×0.05m×0.002m). The results show that the required critical solid mass flow rate increases as the superficial air velocity increases superficial air velocity. The solid loading ratio and superficial air velocity displayed a decreasing power law relationship. This finding agrees with existing theory and experimental results. However, a minimum inlet solid loading ratio exists. When the air velocity is greater than the corresponding air velocity of the minimum solid loading ratio, the solid loading ratio exhibits an increasing trend in power law. We also found that when the inlet conveying pressure increased, the critical solid mass flow rate required for blockage, the inlet solid loading ratio, and the minimum inlet solid loading ratio increased.

Performance assessment of CO2 capture with calcination carbonation reaction process driven by coal and concentrated solar power

Calcination carbonation reaction (CCR) process is regarded as a promising option for pulverized coal power plant to mitigate CO2 emission. In this paper, concentrated solar power (CSP) substitutes for coal to supply part of the calcination energy in order to reduce the fossil fuel consumption associated with the calciner. A CCR process driven by coal and CSP is examined from the perspective of energy efficiency. This paper focuses on the parameters of heat recovery efficiency, CSP capacity, compression energy, air separation energy and recycled energy to determine the contribution of each to the overall energy penalty. In addition, the effects of heat recovery efficiency, CSP capacity, purge percentage and CO2 capture efficiency on the co-driven case are analyzed through a sensitivity analysis. The results indicate that the thermal efficiency of integrating CCR co-driven process into an ultra-supercritical 1019 MW power plant is 35.37%, which means that the overall efficiency penalty is 9.63 percentage points. Moreover, the co-driven case reduces the fossil fuel consumption and the mass flow rate of fresh sorbent and circulation solids compared with coal-driven case. Increasing heat recovery efficiency and CSP efficiency can improve the co-driven case performance.

Numerical simulation and experimental investigation of plug-flow fluidized bed drying under dynamic conditions

In this study, a mathematical model was presented for prediction of the plug-flow fluidized bed drying process under dynamic conditions resulted from the transient of inlet dry solids mass flow rate. The model previously developed and successfully validated for plug-flow fluidized bed drying process under steady-state condition was the starting point of this study. This model was extended in order to account for the mass and energy transfers between solids and gas phases at dynamic conditions. Additionally, a mass balance equation of dry-based solid holdup and a mass flow rate relationship for outlet solids were developed to predict the transient response of outlet dry solids mass flow rate. The model equations were solved numerically using the finite difference method. To validate the model, drying of rough rice in a laboratory-scale plug-flow fluidized bed dryer was investigated under dynamic conditions. A very satisfactory agreement between simulated and measured results was achieved.

On the prediction of pickup and saltation velocities in pneumatic conveying

This paper presents a comparative study of the critical pickup and saltation velocities of particles in horizontal pipelines for pneumatic conveying design. A comparative study is performed using different existing correlations in the literature for the determination of the minimum velocity of transport as a function of the particle and pipe diameter, particle density, solid mass flow rate and particle sphericity. Their limitations and difficulties in predicting those critical velocities are analyzed. For the pickup velocity, an experimental study was also carried out in order to support the analysis. Recommendations are presented on the use of such correlations.

Weighing without Touching: Applying Electrical Capacitance Tomography to Mass Flowrate Measurement in Multiphase Flows

Electrical capacitance tomography has a well-established reputation as a research tool and has been used in a number of industrial applications including dry solids flows, gas–liquid flows, and wet gas flows. Electrical capacitance tomography can give detailed flow structure information that has been experimentally validated against other techniques. Here, we focus on its use for measuring the detailed flow structure and overall mass flowrate of dispersed dry solids in gravity-drop flows. Electrical capacitance tomography–based flowmeters capable of being mass-produced and deployed into the commercial industrial environment are being developed, and prototypes are available, but none are yet in full-scale manufacture. Sensors of this type are being designed for applications in milling, power generation, and pneumatic transport. The same sensor technology may also be applied to measurements of gas–liquid flows in oilfield applications.

Dilute pneumatic conveying of a horizontal curved 90° bend with soft fins or dune model

In order to reduce pressure drop and conveying air velocity, the paper studied the effect of the dune model and soft fins in horizontal pneumatic conveying involving a 90° bend. Experimental measurements were performed in terms of the pressure drop, conveying air velocity and additional pressure drop. The distributions of particle velocity near and in the curved 90° bend were measured by high-speed PIV. The test pipeline consisted of a 4.5m-long horizontal straight acrylic tube, a curved 90° acrylic bend (mean radius of curvature 250mm) and a 1.5m-long horizontal straight acrylic tube, having an inside diameter of 80mm. The polyethylene particles with diameter of 2.3mm were used as conveying materials. The superficial air velocity was varied from 10 to 14m/s, and the solid mass flow rate was fixed at 0.45kg/s. Comparing with the conventional pneumatic conveying, the pressure drop, the minimum pressure drop (MPD) velocity and additional pressure drop can be reduced by using soft fins in lower air velocity range. The reduction rates of the MPD velocity by using soft fins and dune model were about 4.1% and 8.3%, respectively. At the upstream of bend and in the bend, the particle velocity of using the dune model is evidently higher than that of the conventional pneumatic conveying and using soft fins. However, the effect of soft fins and dune model on the particle velocity is maintained downstream of the bend.

Eulerian–Lagrangian Simulation and Experimental Validation of Pneumatic Conveying Dryer

This paper explores numerical and experimental studies on the performance of a pneumatic conveying dryer. The four-way coupling Eulerian–Lagrangian approach is utilized in the numerical study and the experimental study is carried out in a pilot-scale vertical pneumatic conveying dryer of diameter 8.1 cm and 4.5 m length. The effects of Reynolds number, particle size, solid mass flow rate, and inlet gas temperature on the dryer performance are investigated. It is found that the present model predictions agree well with the experimental data. Generally, it is concluded that the drying rate increases as the Reynolds number increases, while increasing the particle size or the solid mass flow rate decreases the drying rate.

Solid Mass Flowrate Measurement System Using the Double-Elbow Method

The gas-solid flow is widely used in the enterprises. The real-time solid mass flowrate measurement is an important role to the enterprise production. Based on the gas flowrate measurement principle of the Elbow, the new Double-Elbow real-time solid mass flowrate measurement method in the gas-solid flow is brought out in this paper. The new method can finger out the mass flowrate directly and need not measure the mixture density in advance. The instrument on measuring the solid mass flowrate is developed based on the new method; the instrument is using the 8031 as the MCU; the measurement result can be displayed on the LED. The experiment on measuring the solid mass flowrate is carried out in the pneumatic conveying system. The experimental results prove that the instrument can be real-time on-line measuring the solid mass flowrate.

Effect of Air Injector on the Airlift Performance in Air-Water-Solid Three-Phase Flow

AbstractTo understand the effect of an air injector on airlift performance, an experimental study of the influence of air exit-port arrangement on the mass flow rate of solids and lifting efficiency was performed. An airlift with a riser 1,500-mm long and 40-mm diameter was designed and tested. At a constant submergence ratio, the mass flow rate of solids and lifting efficiency were significantly affected by the air exit-port arrangement. As the air flow rate increased, the mass flow rate of solids increased to a maximum value and then decreased slightly. The curve relating the air flow rate to lifting efficiency was m-shaped, i.e., it contained two local maxima. The air flow rate at the second efficiency maximum was approximately equal to the air flow rate at which the solid mass flow rate was maximal. When the measurement results were expressed in dimensionless form, the relation between the volume flow of slurry and air flow rate was approximately the same for all air exit-port arrangements, and was in...

Analysis and Measurements from a Prototype In-Line Thermal Solids Mass Flowmeter in an Industrial Scale Dilute Phase Pneumatic Conveying System

The in-line measurement of solids mass flow rate in a prototype industrial scale pneumatic conveying pipeline by a thermal method has been investigated over a range of dilute conveying conditions. A thermal method of determining solids mass flow rate should, in principle, be capable of achieving a reliable measurement regardless of; inhomogeneities in solids’ distribution, irregularities in velocity profile and variations in particle size or shape. The instrument described in this article operates by the injection of heat energy into the pipeline by way of a heated section and measuring the resultant change in solids’ temperature using infrared sensors. Initial results from the thermal instrument are compared with measurements from a gain in weight system showing good correlation. The importance of sensor window condition and temperature on measurement is discussed.

An investigation of the generation of Acoustic Emission from the flow of particulate solids in pipelines

This paper is concerned with the generation of the Acoustic Emission (AE) from particulate flow and an investigation of the potential of implementing AE for flow parameters, namely the solid mass flow rate, particle velocity and size, monitoring. A series of experiments has been conducted to gather AE signals from a laboratory scale single flow-loop pneumatic conveying system. Initially, AE sensors were attached to two steel meshes which were placed with a fixed axial distance in the pipeline to study the generation of the AE and subsequently the possibility of using those generated AE to determine particle velocity in the pipeline. Particle velocities measured from this approach were compared with theoretical predictions. The results indicated that this approach could measure the mean particle velocity with reasonable accuracy. The generation of AE on five different sensor mounting locations was also studied. The results showed that sensors mounted on all those locations were able to respond to changes in the flow parameters. However, only two sensor locations (outer bend and Mesh) were chosen for further investigation. The final experimental results indicated that the AE features, namely Root-Mean-Square (RMS) and energy of the AE, are related to the changes in the flow parameters and good correlations were found. Good correlations between the RMS and energy of the AE with the momentum and kinetic energy of the particles, respectively, were also found. Overall, the studies indicated that features of AE have great potential in gas–solid two phase flow parameter monitoring. However, the studies also show that the applicability of the AE techniques to measure solid mass flow rates in practice would require tedious calibration.

Experimental Investigation and Modeling of Plug-Flow Fluidized Bed Drying Under Steady-State Conditions

In this study, a model for a plug-flow fluidized bed dryer under steady-state conditions was presented. The model was based on differential equations; thus the bed of the dryer was divided horizontally and vertically into major and minor control volumes, respectively. Each control volume was composed of two thermodynamic systems: solid and gas. The mass and energy balances of the particles in the major control volume based on the axial dispersion were developed to derive the axial profiles of solid moisture content and temperature. To derive the variation of gas humidity and temperature along the bed height and hence the axial profiles of outlet gas humidity and temperature, the mass and energy balances in the gas over the minor control volume, considering the plug flow of gas through the bed, were developed. The model was validated by comparing the simulation results with the experimental data obtained by drying the long-grain rough rice under steady-state conditions in a laboratory-scale, plug-flow fluidized bed dryer. A very satisfactory agreement between the simulation and the experimental data of solid moisture content, solid temperature, and outlet gas humidity and temperature was achieved. Also, the effects of inlet gas temperature, weir height, and inlet dry solid mass flow rate on the simulated axial profiles of solid moisture content and temperature, humidity difference between inlet and outlet gas, and outlet gas temperature were investigated.

Parameter Sensitivity Analysis on Pressure Drop of Gas-solid Flow for Absorber Sphere Pneumatic Conveying

The pressure drop of gas-solid flow for absorber sphere pneumatic conveying is important for the design and operation of the gas circulator. The simplified one-dimension model is introduced to predict the pressure drop of gas- solid flow for absorber sphere pneumatic conveying. The pressure drop of gas-solid flow in the vertical pipe is the main component part of the total gas-solid flow for absorber sphere conveying. The pressure drop of gas-solid flow for absorber sphere conveying in the vertical pipe with the inside diameter 47mm and conveying height 23 m is predicted by the simplified model. The superficial gas velocity considered is in the range of 1.5 to 3.0 times of the terminal velocity of a single particle. The solid mass flow rate considered is in the range of 0.2 to 1.2kg/s. Particle velocity, solid friction factor and solid mass flow rate are important parameters to predict pressure drop of vertical pipe. The typical empirical correlations of particle velocity and solid friction factor reported in the literature are adopted to predict the pressure drop of vertical pipe. The superficial gas velocity for absorber sphere conveying is suggested to be two times of the terminal velocity of a single particle. For the suggested superficial gas velocity, the predicted pressure drop of vertical pipe by using empirical correlations is in the range of 15 to 20kPa and 31 to 50kPa for solid mass flow rate at 0.2kg/s and 1.2kg/s, respectively. For the suggested superficial gas velocity, the relatively conservative predicted pressure drop of vertical pipe is in the range of 20 to 78kPa for solid mass flow rate in the range of 0.2 to 1.2kg/s. Further work is needed to verify the pressure drop model and to modify the key parameters for absorber sphere conveying in helium.

Modeling and analysis for fluidized dense phase conveying including particle size distribution

Abstract Pressure drop in fluidized dense phase pneumatic conveying involves frictional interactions among gas, particle and pipe wall. There have been numerous correlations proposed by different researchers for predicting the pressure drop in fluidized dense phase conveying. In this paper steady state flow equations have been written for different phases and these equations are solved by assuming certain factors for different conveying materials. For writing the flow equations, a single gas phase and certain number of solids phases (which are chosen based on the particle size distribution of the conveying material) have been considered. Experimental data have been used as initial conditions at the exit of the pipeline in order to solve for the value of the flow parameters at the inlet of the pipeline. Experimental data have also been used to find the maximum possible conveying distance or maximum possible conveying pipeline diameter by imposing certain limiting conditions of conveying. Scaling equations for the solids mass flow rate and the air mass flow rate have been used to predict the pressure drop for different pipeline diameters and pipeline lengths.

The Effect of Air Injection Method on the Airlift Pump Performance

With simple structure, excellent reliability, low cost, no restriction at depth of water, and easy control and operation, airlift pumps have special advantage in borehole hydraulic jet mining, river dredging and deep sea mining. To clarify the mechanism and process of action of air injection methods on air lift performance, and to enhance lifting capacity, the pump performance of a small airlift system in transporting river sands is investigated experimentally in the present study. The results are as the follows. The influences of air exit ports on water volume flow rate, mass flow rate of solids and lifting efficiency are studied and found to be very low when the number of air exit ports exceeds 3. The pump design show best pumping capability for water and solids at higher air flow rates, but the lifting efficiency is then very low. In addition, a dimensionless equation which describes the flows in the pipe is presented based on the Bernoulli equation, and compared with measurement results in the dimensionless form, which are nearly in good agreement with each other for all the arrangements of air exit ports and are basically contained within ±18% of the theoretical curve. The results are important for understanding the mechanism of airlift pumps and enriching multiphase flow theory.

Extraction from striped weakfish (Cynoscion striatus) wastes with pressurized CO2: Global yield, composition, kinetics and cost estimation

Extraction with pressurized carbon dioxide was applied to recover polyunsaturated fatty acids (PUFA) from striped weakfish (Cynoscion striatus) wastes. Extraction yield was evaluated at temperatures from 30 to 60°C and pressures from 20 to 30MPa. Temperature and pressure of 30°C and 20MPa were selected to evaluate process kinetics. A scale-up was performed by keeping the ratio constant between solid mass and solvent flow rate. Mathematical models were applied to the extraction curves, and the broken and intact cell model provided good fits, being applied to multiple curves simultaneously. Manufacturing cost of the extraction was estimated, and an optimal extraction time was observed by the end of the convective period. Finally, the extracts were analyzed by gas chromatography, and over 20% of the oil was composed by PUFA, whose concentration increased with extraction time. Therefore, this work shows that pressurized CO2 extraction can obtain valuable compounds from fish residues.