Solid Mass Flow Rate Research Articles

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.

Frictional Force Measurement for Multiple Plugs in Dense Phase Pneumatic Conveying of Polymer Particles: An Industry Application

Frictional forces between particles and the pipe wall in dense phase pneumatic conveying were determined using strain gauges attached to the outside of the pipe wall. To perform the frictional force measurement, a special strain measurement section was designed and inserted in the industrial scale pneumatic conveying system. Three different polymer particles, polyolefin elastomer, polyethylene, and SARAN were transported under the different flow conditions of the superficial air velocity and the mass flow rate of solids. The frictional forces were determined from three different locations of the pipe wall, top, bottom, and sides of the pipe. The plug velocity and plug length were also determined by analyzing pressure signals measured at two different locations. The magnitude of frictional force was found to be proportional to the plug length. In general, the largest frictional forces were measured at the top of the pipe. In addition, the frictional forces were related to the particle’s interaction with the pipe (i.e., the area of contact of individual particle and number of particles that interact with the pipe wall) as well as the material properties. It was also found that the minimum fluidization of the particles could be related to the strain signal fluctuations. Materials with a smaller minimum fluidization velocity showed more fluctuations and thus have less stable operation. The results obtained were compared to the smaller scale laboratory pneumatic conveying system previously performed.(1)

The influence of windows on infra-red temperature measurements for solids’ mass flow rate determination

Thermal mass flow meters can, in theory, be used in pneumatic conveying applications to provide a reliable monitoring of the mass flow rate of solids being transported in a stream of gas. Accurate measurement of temperature is necessary for the mass flow rate to be reliably determined. Direct measurement of temperature of particulate solids being conveyed pneumatically can be achieved, in principle, with the use of infra-red (IR) detectors. This has been done in previous work for the measurement of solids’ temperatures in a pneumatic conveying line where windows were employed. This paper investigates the influence of windows on the temperature measurement process. We investigate specifically the effect of dust deposited on the window surface in conjunction with the window temperature. The results show that if the window is not ideal, measurements of temperatures above the temperature of the window will be below actual, and measurement of target temperatures below the window temperature will be higher than actual. A simple assumption that a non-ideal window would attenuate the IR signal and result in lower temperature measurements is therefore, not valid. An analysis is offered that explains the results obtained.

An Experimental Study of Horizontal Self-Excited Pneumatic Conveying

A new pneumatic conveying system that applies soft fins mounted vertically on a center plane of pipe in the inlet of the gas-particle mixture is developed to reduce power consumption and conveying velocity. The effect of different fin’s lengths on a horizontal pneumatic conveying is experimentally studied in terms of the pressure drop, conveying velocity, power consumption, particle flow pattern, and additional pressure drop. The test pipeline consisted of a horizontal smooth acrylic tube with an inside diameter of 80 mm and a length of about 5 m. Two kinds of polyethylene particles with diameters of 2.3 mm and 3.3 mm are used as conveying materials. The superficial air velocity is varied from 10 to 17 m/s, and the solid mass flow rate is from 0.20 to 0.45 kg/s. Compared with conventional pneumatic conveying, the pressure drop, minimum and critical velocities, power consumption, and additional pressure drop can be reduced by using soft fins in a lower air velocity range, and the efficiency of fins becomes more evident when increasing the length of the fins or touching particles stream by the long fins. The maximum reduction rates of the minimum velocity and power consumption by using soft fins are about 20% and 31.5%, respectively. The particle concentrations of using fins are lower than those of non-fin near the bottom of the pipe and are higher than those of non-fin in the upper part of the pipe in the acceleration region. Based on analyzing the frequency features of the fin’s oscillation, the Strouhal number of more efficient fins is about St ≈ 0.75 in the air velocity range of lower than 13 m/s.

Numerical study of liquid–gas–solid flow in classifying hydrocyclones: Effect of feed solids concentration

This work presents a numerical study of liquid–gas–solid flow in classifying hydrocyclones (CHs). In the numerical model, the turbulent flow of a liquid–gas–solid mixture is modelled using the Reynolds stress model. The interface between the liquid and air core, and the particle flow are both modelled using the mixture multiphase model under different conditions. The flow features are examined in terms of flow field, pressure drop, amount of water split to underflow, and separation efficiency. The approach is first verified by comparing the measured and calculated results. Then, it is used to investigate the effects of feed solids concentration and its fluctuation. The results show that when feed solids concentration is increased, the separation efficiency decreases while the cut size increases; the inlet pressure initially decreases to a minimum and then increases, and the amount of water split to underflow firstly increases to a maximum and then decreases. It is also shown that the air core, solid mass flowrates on the underflow and overflow, and inlet pressure drop fluctuate corresponding to feed solids fluctuation. However, the fluctuation only affects the average CH separation efficiency slightly.

Characteristics of particle velocity and concentration in a horizontal self-excited gas–solid two-phase pipe flow of using soft fins

In order to reveal the mechanism of the low pressure drop at low air velocity in a horizontal excited gas–solid two-phase pipe flow of using soft fins, the distributions of particle velocity and concentration are measured by the high-speed particle image velocimetry (PIV) and image process. The test pipeline consists of a horizontal smooth acrylic tube with an inside diameter of 80mm and a length of about 5m. The polyethylene particles of density 978kg/m3 and 952kg/m3 with diameters of 2.3 and 3.3mm are used as test materials. The distributions of the time-averaged particle velocity and concentration are measured at the minimum air velocity and the solid mass flow rates of 0.45kg/s and 0.40kg/s in the acceleration and fully developed regimes. It is found that the particle concentration of using fins exhibits almost same profile as that of non-fin although the air velocities of using fins are lower than that of non-fin. In the acceleration regime, there is little difference of the normalized axial particle velocity up/Ua between short fins and non-fin. up/Ua of the long fins having low air velocity, however, is slightly higher than that of non-fin. In the fully developed regime, even though up/Ua of using long fins is obviously lower than that of other fins and non-fin in the lower part of pipeline, the steady gas–solid two-phase flow can be observed. It suggests that the long fins easily accelerate the particles and result in low pressure drop and low air velocity. For the relatively large particles, the effect of fins on up/Ua is smaller than that for the small particles. Due to the effect of fins’ oscillation, the vertical particle velocity decreases in the low part of pipeline, resulting in the particle dispersion and the reduction of particles–wall collision.

Experimental Investigation into a Pilot-Scale Entrained-Flow Gasification of Pulverized Coal Using CO2 As Carrier Gas

Using CO2 as a carrier gas in pneumatic conveying of pulverized coal instead of N2 has been paid more and more attention with the wide application of dry-feed entrained-flow coal gasification technology due to its attractive effects as a reactant. Accordingly, a pilot-scale performance of entrained-flow gasification using CO2 as the carrier gas of pulverized coal was investigated at gasifier temperatures between 1300 and 1400 °C. The differences in solid mass flow rate and flow stability are insignificant in the dense-phase pneumatic conveying between CO2 and N2 carrier provided that the conveying pressure differences and solid velocities in the pipeline are kept constant. Regarding syngas composition in dry basis, there was a desired drop in inert gas (N2) concentration from about 6% to less than 2%, while the CO2 concentration increased by about 4%age points in optimal operation conditions when CO2 carrier substituted for N2. At the same time, gasification profiles in different operation conditions indicated that CO2 carrier can act as an auxiliary gasification agent. Steam as another important gasification agent, however, cannot be completely substituted by CO2 carrier gas.

Particle scale modelling of the multiphase flow in a dense medium cyclone: Effect of fluctuation of solids flowrate

Dense medium cyclone (DMC) is widely used to upgrade run-of-mine coal in the coal industry. The flow dynamics/fluctuation in a DMC is important but has not been studied previously. In this work, the dynamics is studied by numerically with special reference to the effect of the fluctuation of solid mass flowrate. The simulation is carried out by use of a combined approach of Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). In the model, the motion of discrete mineral particle phase is obtained by DEM which applies Newton’s equations of motion to every individual particle and the flow of medium (mixture of water, air and fine magnetites) phase by the traditional CFD which solves the Navier–Stokes equations at a computational cell scale. The simulated results are analysed in terms of medium and coal flow patterns, and particle–fluid, particle–particle and particle–wall interaction forces. It is shown that under high fluctuation frequency and current conditions, the performance of DMC is not sensitive to both the fluctuation amplitude and period of coal flow at the DMC inlet. However, under low fluctuation frequency, as fluctuation amplitude increases, the separation performance deteriorates slightly and the flow is obviously affected at the spigot. A notable finding is that the near-gravity particles that tend to reside at the spigot and/or have longer residence time in the DMC would be affected more than other particles. The work shows that this two-way coupled CFD–DEM model could be a useful tool to study the dynamics of the flow in DMCs.

Investigations of pulverized coal pneumatic conveying using CO2 and air

The pneumatic conveying experiments at the high solid–gas ratio (120–300kg/m3) were carried out to compare their conveying characteristics separately using CO2 and air as carrier gas. The differences between them are found to be related with fluidized state of pulverized coal in the feeding vessel and can be explained with material properties involving particle–gas interactions, permeability. Employing electrical capacitance tomography (ECT), the transition from full pipe flow to annular flow was observed with increasing the superficial gas velocity (3.0–8.5m/s) in the vertical pipe and the flow patterns with CO2 and air are found to be similar. The analysis shows there is a significant association between sharp fluctuations of the pressure signals and gas slug. When gas slug was observed in the pipe, there was a large pressure pulse. The occurrence of gas slug is also found to be higher in the transporting with CO2 as carrier gas. The pressure signals may therefore be used to identify gas slug appearing in the pipe. The energy analysis is presented to find that the energy consumption with CO2 is about 7.5% higher than that with air at the same gas flow rate, but the required energy with CO2 is increased by about 20% than that with air at the same solid mass flow rate.

Berechnung des Schüttgutmassenstroms in Dächerschachttrocknern

Mixed-flow dryers are delivered in various modes of recirculation or through-flow dryers and predominantly used for grain drying. To design and control the dryer, the knowledge of the solids mass flow rate or discharge rate is essential. Fundamentals for its calculation are not known from the literature so far. Hence, this work was aimed to derive appropriate fundamentals. Based on experiments on the discharge characteristic at a test dryer equipped with a discharge gate, equations for the solids mass flow rate for the continuous and the interrupted mode of operation were developed, respectively.

The Flow Conditions to Move Different Plastic Particles in Dilute Pneumatic Conveying

In this research, positive-pressure high velocity pneumatic conveying has been tested to determine the flow conditions such as minimum velocity, solid mass flow rate, and pressure drop per unit length of polypropylene (PP), recycled polyethylene (recycled PE), high-density polyethylene (HDPE), and low-density polyethylene (LDPE). The conveying efficiency (η ) of such two-phase flow was also experimentally investigated. During the course of the experimental conduct, the material sphericity ranged from 73.2 to 84.4 %. True density ranged from 904.5 to 1305.7 kg/m3, and bulk density covered the range of 493.7 to 783.4 kg/m3 .The tests were carried out on a pneumatic conveying test rig using a PVC pipes of 0.079-m inner diameter and total test length of 8.57 m. The results showed the minimum conditions to move the particles in dilute phase. For the conveying efficiency (η), the efficiency varies reversely with the air velocity in exponential function.

An experimental study on a horizontal energy-saving pneumatic conveying system with soft fins

In order to reduce power consumption and conveying velocity, a new pneumatic conveying system where soft fins are mounted in a horizontal plane through the pipe axis in the front of inlet is proposed in this paper. The experimental study focuses on the effect of the different fin's lengths on the horizontal pneumatic conveying system in terms of frequency characteristics of fin's oscillation, pressure drop, conveying velocity, particle flow pattern, power consumption and additional pressure drop. The test pipeline consisted of a horizontal smooth acrylic tube with an inside diameter of 80mm and a length of about 5m. The polyethylene spherical particles of density 978kg/m3 and 952kg/m3 with diameters of 2.3mm and 3.3mm are used as conveying materials. The mean air velocity is varied from 10 to 17m/s, and the solid mass flow rate is from 0.20 to 0.45kg/s. Comparing with the conventional pneumatic conveying, the pressure drop, minimum and critical velocities, power consumption and additional pressure drop can be reduced by using soft fins in lower air velocity range. The efficiency of fin is quite evident with increasing the length of fin. The maximum reduction rates of the minimum velocity and power consumption by using soft fins are about 14.8% and 25.5%, respectively. By analyzing the frequency characteristics of fin's oscillation, Strouhal number of more efficient fins is about St=0.65 in the range of low air velocity.

Transient parameter analysis of fluidized dense phase conveying

Fluidized dense phase pneumatic conveying is a common mode of flow for conveying fine particles. Experimental and theoretical investigations conducted for this work suggest that the flow mechanism involved in this type of conveying is highly transient or pulsatile rather than in steady state. Assumption of steady state flow behavior by several researchers has resulted into lower accuracy in predicting the conveying parameters. Pressure fluctuating signals of the gas pulses from the pressure transmitters shows the transient nature of the flow. These are characterized by pulse parameters, in particular, the pulse amplitude and the pulse frequency. These transient parameter variations along the length of pipeline have been investigated and are presented in this paper. Analysis shows that these transient parameters are influenced by pneumatic conveying parameters like the air mass flow rate, solids mass flow rate and pressure drop and non-dimensional parameters relating to power consumption.

Wavelet analysis on particle dynamics in a horizontal air–solid two-phase pipe flow at low air velocity

High-speed particle image velocimetry (PIV) is first used to measure two components of the fluctuating particle velocities for different particle sizes and solid mass flow rates at low air velocity in a horizontal pipe. Then, the continuous wavelet transform and orthogonal wavelet multi-resolution techniques are employed to analyze and decompose the fluctuating particle velocities to provide both quantitative and qualitative information on the particle fluctuation velocity of various frequencies. It is revealed that the fluctuating energy of axial particle velocity is mainly contributed from the wavelet components of low frequency, accounting for about 84%, near the bottom part of the pipe cross-section. However, the contribution to the fluctuating energy of vertical particle velocity accounts for about 82% from the wavelet components of high frequency. The auto-correlation analysis suggests a quasi-periodical large-scale axial particle fluctuating velocity. On the other hand, the spatial correlation analysis indicates that the low-frequency components of the axial particle velocity exhibit a large correlation near the bottom part of the pipe cross-section. From the probability density function (PDF) distribution, it is found that the low-frequency components of the axial particle velocity exhibit larger fluctuation, and this fluctuation reduces as the frequencies increase near the bottom part of the pipe cross-section. Near the top part of the pipe cross-section, however, a larger fluctuating axial particle velocity appears in the high-frequency range.

Multiphase Flow Measurement Techniques for Slurry Transport

Multiphase flow measurement techniques are required to monitor slurry transport in industrial processes. Monitoring methods are used to ensure that the slurry is transported under specific conditions, and as an indicator of potential problems. Intrusive and non-intrusive sensors are used to measure solids concentration, mass flowrates, velocities and flow patterns. Sensing techniques are based on pressure, electrical, sound, imaging and nuclear properties. In this literature review, measurement techniques examined for horizontal pipelines include pressure measurements, the Coriolis mass flowmeter, acoustic sensors, capacitance, conductivity and microwave probes, electrical resistance tomography, laser Doppler imaging and the Pulsed Neutron Activation Technique. The principles of operation are described along with experimental results and a critique of the sensors and technology.

200-MW chemical looping combustion based thermal power plant for clean power generation

SUMMARY The present study demonstrates a possible configuration of a 200 MW chemical looping combustion (CLC) system with methane (CH4) as fuel. Iron oxide-based oxygen carriers were used because of its non-toxic nature, low-cost, and wide availability. We analyzed the effects of different variables on the design of the system. For the air reactor (oxidizer), bed mass is independent, and for the fuel reactor (reducer), it decreases with increase in the conversion difference between the air and fuel reactors. On the other hand, the pressure drop in the air reactor is unchanged, whereas for the fuel reactor, it decreases with the same increase of conversion difference between air and fuel reactors. Also, entrained solid mass flow rate from the air to fuel reactor shows a decreasing trend. Bed mass, bed height, pressure drop, and residence time of the bed materials decrease with increase in the conversion rates in the air and fuel reactors. Residence time of bed material in the air and fuel reactor reduces with increase in the temperature of the air reactor. Copyright © 2011 John Wiley & Sons, Ltd.

Experimental study on the solid velocity in horizontal dilute phase pneumatic conveying of fine powders

The calculation reliability of pressure drop and gas–solid drag force in horizontal dilute phase pneumatic conveying strongly depends on the accuracy of gas–solid velocity correlation. However, there are limited studies on the solid velocity in horizontal dilute phase pneumatic conveying and it is important to further validate suitability of existing correlation of gas–solid velocity, especially for fine particles (such as pulverized coal). Consequently, in this paper, a negative pressure pneumatic conveying test rig is set up and two kinds of powders with different sizes are adopted. Optical fiber probe (OFP) was used to measure the volumetric solid concentration and particle velocity. The volumetric solid concentration was also calculated by using the measured particle velocity. The results show that the solid concentrations obtained by the two methods have good agreement, and discrepancy is within ± 20%. It was found the particle velocities are different in the upper and lower part of the cross-section in the horizontal pipe. However, the difference is generally no more than 2 m/s. The velocity difference will decrease with the increasing gas velocity, and increases with the solid mass flow rate. In the experimental condition of 0.06 mm < d s < 0.35 mm, 1400 kg/m 3 < ρ s < 2600 kg/m 3, the implicit correlation based on Yang's Unified Theory gives the best prediction of particle velocity among existing studies but still with noticeable discrepancy with the comparison of the present experimental data. By modifying the solid friction factor, an improved correlation of the particle velocity was obtained, which agrees better with the experimental data given in the present and literature studies.

A reproducible test to characterise the triboelectric charging of powders during their pneumatic transport

Although several investigations had been carried out to explore the triboelectrification of powders, only few data are available on the experimental procedures and set-ups required to obtain reliable data. The present study deals with the development of a pneumatic test to characterise the tribocharging of fine powders. An experimental device was set up allowing on-line monitoring of the charge of both particles and transport pipes. Experiments were carried out using two types of powder (fine sugar and PVC) coupled with two types of pipe materials (Teflon and nylon). Results showed the extreme importance of the control of the relative humidity, the initial charge of particles and the charge dissipation of the walls to obtain pertinent data. Furthermore, the results showed that solids loadings higher than 1 (kg of solids/kg of air) are not proper to achieve reliable measurements. However, at very dilute solids loading (∼0.001) the time evolutions of the electrostatic charge and the mass of the powder follow similar trends so that the tribocharging becomes independent of the solids mass flowrate. This allows accurate assessment of the tribocharging of cohesive powders for which a regular flow cannot be guaranteed.

Application of high-speed PIV and image processing to measuring particle velocity and concentration in a horizontal pneumatic conveying with dune model

The purpose of this study focuses on analyzing the particle velocity and concentration characteristics in a horizontal pneumatic conveying with dune model, so as to reveal the mechanism of the low conveying velocity and saving-energy conveying. The test pipeline consisted of a horizontal smooth acrylic tube with an inside diameter of 80 mm and a length of about 5 m. The polyethylene particles of density 978 kg/m 3 and 952 kg/m 3 with diameters of 2.3 and 3.3 mm are used as conveying materials. High-speed PIV was first applied to measure the time-averaged particle velocity and was proven to be an efficient measurement technique in the pneumatic conveying. Then the particle velocity and concentration distributions of three locations were measured at mean air velocities of 12 m/s and 13 m/s and the solid mass flow rates of 0.45 kg/s and 0.43 kg/s. A comparison of the particle velocity and concentration profiles between dune model and non-dune model was performed. It is found that the particle concentration of using dune model becomes higher in the upper part of pipeline and becomes lower near the bottom of pipeline in the acceleration region. The particle velocities of using dune model are clearly higher than that of the conventional pneumatic conveying along pipeline and display a uniform profile at the downstream. It is also clear that the particles can be effectively accelerated by increasing air velocity and impacting the surface of dune model. The effect of dune model on the velocity profile of relatively small particles is larger than that of the larger particles and maintains to the downstream.

Effect of operating conditions and particle properties on performance of vertical air-lift

The effect of the fluidization air flow rate and the transport air velocity on the solids mass flow rate and the pressure drop along the transport pipe was investigated in a vertical air-lift. The use of two different materials, glass (150μm) and zirconium oxide (260μm) particles (Geldart's B class), enabled to estimate the effect of particle properties on the air-lift performance. Different levels of the solids mass flow rate were obtained by varying the fluidization air flow rate while keeping the transport air velocity constant. The solids loading ratio varied between 2 and 16 for both types of particles. The pressure drop was non-linearly related to the solids mass flow rate at most of the transport air velocities tested. State diagrams presenting the relationship between the transport air velocity, the solids mass flow rate, and the pipeline pressure drop were constructed to characterize the flow pattern and to compare the behavior of the glass and zirconium oxide particles. Owing to the larger size and higher density, the zirconium oxide particles displayed higher pressure drop values than the glass beads and the minimum pressure drop shifted towards higher transport air velocities. The velocity at the transition between dilute and dense phase conveying was approximately in the range of 7 to 10m/s for glass beads and 10 to 12m/s for zirconium oxide, at the solids mass flow rates tested. The flow patterns could be also effectively characterized from the analysis of the pressure drop fluctuations at different transport air velocities.