Inlet Particle Concentration Research Articles

Improving the removal of fine particles in cyclone using heterogeneous vapor condensation enhanced by atomization

Using a heat exchanger to cool high humidity flue gas can create a supersaturated water vapor environment, allowing fine particles to grow into large droplets by heterogeneous vapor condensation, which is conductive to the removal of fine particles by traditional equipment. However, due to the limited condensable vapor obtained by cooling, this technology can only be used in the flue gas with low particle concentration. In this study, atomization droplets were added before the heat exchanger to improve the effect of heterogeneous vapor condensation at high particle concentration, and then coupled with a cyclone separator, which was used for the deep treatment of the flue gas after the wet dedusting system. The particle removal characteristics were investigated through laboratory experiments and bypass experiments in a metallurgical company. The experimental results show that the application of atomization-heterogeneous condensation reduced the particles concentration after cyclone by 74.2 % compared with that of single heterogeneous condensation. Temperature-drop and atomized volume affected the removal of particles with size < 2 μm and > 2 μm, respectively. The industrial flue gas bypass experiment indicated that the system had strong adaptability to fluctuating conditions. When the inlet particle concentration did not exceed 2000 mg/Nm3, the outlet particle concentration can be maintained within 20 mg/Nm3.

The Secondary Flows in a Cyclone Separator: A Review

A cyclone separator holds significant importance as the primary gas–solid separation apparatus in the industrial sector. Cyclone separators operate based on a fundamental principle, primarily harnessing the centrifugal force produced by the rotation of air in order to segregate solid particles from the gas stream and then collect them. In addition to the main vortex in the flow field, there are a number of secondary flows, which significantly impact the aggregation of fine particles and contribute to the heightened energy consumption. This paper provides a summary of the three secondary flows in a cyclone separator. These include the recirculation flow in the annular space, which is greatly influenced by the inlet particle concentration. Additionally, the short-circuit flow occurs beneath the vortex finder as a result of the collision between the incoming flow and the rotating flow. Furthermore, the eccentric circumfluence is defined as the deviation of the rotation center caused by the interaction between the upward and downward flows near the discharge. This paper aims to establish a theoretical framework to investigate the flow pattern tracking and the mitigation of secondary flows in order to enhance the operational efficiency of cyclone separators.

SO3 removal rate and emission test of the limestone-gypsum wet desulfurization system for coal-fired power plants

This paper studies the SO3 removal ability of dual tower wet desulfurization (in series) and adopts a combination of on-site flue gas sampling and laboratory condensation control. A dual tower (series) supported boiler is used. The SO3 content in the original and clean flue gas of the dual cycle wet desulfurization device was measured, and the removal rate of SO3 of the device was measured. Desulfurization is calculated on the basis of the influence of unit electrical load, coal sulfur content, and desulfurization (raw material flue gas) inlet particle concentration on removal rate. This paper discusses and analyzes the SO3 and SO3 emission concentrations for SO3 removal rules in desulfurization systems. The results indicate that the total sulfur content of coal is relatively high, and the concentration of SO3 is relatively high. The traditional flue gas and net flue gas content in the dual tower wet desulfurization system (series) is relatively high. When burning sulfur-containing coal, there may be “blue smoke” in the flue gas. When the unit load changes between 182 MW and 350 MW, the SO3 removal rate of dual tower wet desulfurization (in series) is between 46.7% and 65.3%, with a net flue gas SO3 concentration of 16.0 mg/m3∼20.5 mg/m3. Due to equipment layout and other reasons, the SO3 removal rate of the primary tower is lower than that of the secondary tower. The removal rate of SO3 is also affected by the concentration of original smoke particles. Due to the condensation of SO3 on the particles and the dust removal of the adsorption tower, the higher the concentration of raw flue gas particles is, the higher the removal rate is. SO3 will be higher. The study also suggests the SO3 removal ability of double tower (series) and double ring wet desulfurization, which is better adapted to changes in load and coal. The next step is to explore the SO3 removal capacity of the dual tower system by optimizing its operating parameters. In addition, due to the arrangement of a desulfurization system after dust removal, it is impossible to control the SO3 source. Subsequent research can control the production of existing SO3 through coal distribution and combustion control.

An experimental investigation on performance of microencapsulated phase change material slurry in ground heat exchanger

As a promising alternative to conventional heat transfer fluids, microencapsulated phase change material slurry (MPCS) was applied in ground heat exchanger (GHE) in this paper. A sandbox system embedded with horizontal serpentine GHE was installed and MPCS using N-eicosane (C20H42) as phase change material is prepared. To explore the merits of MPCS, a comparison study between performance of water and MPCS was conducted. In addition, the enhanced heat transfer mechanism of MPCS were studied by comparing performance of MPCS with different inlet temperature and particle concentration. The experimental results indicate that the heat transfer rate and pumping consumption of 25 wt% MPCS with inlet temperature of 30 °C are 10.5 and 2.8 times that of water, respectively. The heat load-to-pumping consumption ratio has an enhancement of 3.73 times in comparison to water. Obviously, considering the phase transition process, MPCS can efficiently improve thermal performance of GHE. However, in the non-phase transition temperature range, the performance of MPCS is even worse than that of water. The comprehensive performance factor of 15 wt% MPCS and 25 wt% MPCS with inlet temperature of 38 °C declined by 45.6% and 36.9% in comparison with pure water.

On Solvent Losses in Amine Absorption Columns

The current work was dedicated to developing a novel model based on the mass transfer theory in combination with classical nucleation theory in order to predict the amount of solvent loss in the amine absorption columns. The work was adopted to consider the physical mechanisms leading to amine loss, including mass transfer, aerosol formation, and evaporation of the amine. Aspen Plus simulator and MATLAB software were integrated to make such simulations possible through a round–trip interaction. The model predictions for the temperature and concentration of different components were compared with the literature experimental data, and a fair agreement was seen. Then, the effects of some parameters such as the inlet stream temperature, particle concentration, and diameter on the amine loss were investigated. The results of this study may help engineers and practitioners properly design the amine absorption columns to reduce amine consumption.

Experimental study on the treatment of desulfurization wastewater from coal-fired power plant by spray evaporation.

In this study, a pilot-scale evaporation tower system was built to treat the desulfurization wastewater by spray evaporation. The distribution characteristics of Cl- in the wastewater evaporation process were investigated. Besides, the morphology and physicochemical property of solid evaporation products from desulfurization wastewater were analyzed. In addition, the emission characteristics of fine particulates were evaluated. The results indicated that the increase of salt content in desulfurization wastewater increased the mass concentrations of Cl- in three phases, but the proportions of it remained almost unchanged, which were about 10%, 55%, and 35% in the gas phase, outlet solid phase, and bottom solid phase respectively. The increase of flue gas temperature can improve the content of Cl- in the gas phase, while the increase of wastewater pH inhibited the formation of gaseous HCl. The solid evaporation products from desulfurization wastewater had a prismatic crystal structure, which mainly included the sulfate and chloride salts, and the main elements including O, Na, Mg, S, Cl, K, and Ca. Besides, the peak values of particle size distribution in the bottom solid phase and outlet solid phase were 7.67 and 0.32μm, respectively. For the particulate matters in flue gas, the spray evaporation of desulfurization wastewater can reduce the particle concentration, promote particle agglomeration, reduce the number concentration of fine particles, and improve the removal effect of PM10. When the inlet particle concentration was 7.62g/m3, it can reduce the particle concentration at the tower outlet to 4.59g/m3 and reduce the number and mass concentrations of PM10 after ESP by about 43.8% and 36.8%.

Investigation of the Flow and Heat Transfer Characteristics and Erosion Law of Particulate in LBE on the Subchannel

A triangle subchannel model was established to study the flow and heat transfer characteristics of lead-bismuth eutectic (LBE) alloy and the erosion rate of the core channel by the particulate in LBE. Under different inlet velocities, particle types, particle diameters, and particle concentrations, the erosion law of the channel wall in LEB was investigated by using a discrete phase model (DPM). The results of this study showed that with the increase of inlet velocity, the outlet temperature of the LEB decreases and the heat transfer capacity was strengthened. The increase of inlet velocity will lead to the increase of erosion rate on the wall, and the change is exponential. The erosion rate of particulate in the low concentration is small but cannot be ignored; with increasing concentration of particulates, the erosion of the wall by particulates becomes serious. The effect of particulate density on the wall erosion rate can be ignored. The effect of changing the particle size on the erosion rate is more significant when the particle size is small, and at the same time, the erosion rate of the particles on the wall increases with the increase of the particle size.

Effects of interphase coupling in one-dimensional particle-laden flow

In Euler–Euler particle-laden flow models, the interphase coupling terms might include, in addition to the drag force, the effects of fluid pressure interaction with the particles and the volumetric displacement of the fluid phase due to the presence of the particles. This paper presents an analytical study on these effects for laminar, one-dimensional, steady, inviscid particle-laden flow. The interphase drag force is represented by a linear Stokes formula that is valid for low particle Reynolds number. It is shown mathematically that a full two-way coupling model, which includes all the aforementioned effects, depends on three parameters: inlet particle volume fraction (concentration), inlet density ratio–between the fluid and particle phases–and inlet velocity ratio. When the inlet particle concentration and density ratio are kept low at 0.01 and 0.001, respectively, both the interphase pressure coupling force and the volumetric displacement of the fluid phase are insignificant. For density ratios of 0.001 and 1 and for the inlet particle concentration values examined, the effect of pressure interaction force is not significant. However, it becomes significant for higher density ratio of 10 at inlet particle concentration of 0.1.

Effects of Particle Concentration on the Dynamics of a Single-Channel Sewage Pump under Low-Flow-Rate Conditions

Single-channel sewage pumps are generally used to transport solid-liquid two-phase media consisting of a fluid and solid particles due to the good non-clogging property of such devices. However, the non-axisymmetric structure of the impeller of this type of pumps generally induces flow asymmetry, oscillatory outflow during operations, and hydraulic imbalance. In severe cases, these effects can jeopardize the safety and stability of the overall pump. In the present study, such a problem is investigated in the framework of a Mixture multiphase flow method coupled with a RNG turbulence model used to determine the structure of the flow field and the related motion of transported particles. It is shown that under different inlet particle concentrations, the flow field in the pump exhibits periodic variations of the pressure. The volume fraction of solid particles at the trailing edge of the suction surface of the blade is the largest, and solid particles tend to be concentrated at the outer edge of the pump body. With a rise in import particle content, the pressure and volume fraction of particles in the sewage pump also increase; for a fixed inlet particle concentration, the pressure pulsation amplitude increases with an increase in the flow rate. In addition, under small flow conditions, as the inlet particle concentration increases, the flow field leaving the sewage pump diaphragm near the outlet of the volute becomes more turbulent, and even a secondary back-flow vortex appears.

A Prediction Method of Wear for Volute Casing of a Centrifugal Slurry Pump

Volute wall wear situations directly affect a long time safe operation for the centrifugal slurry pump unit and the whole system. In the present study, internal flow field is numerically investigated in a solid-liquid centrifugal pump, and the volute wall wear caused by the solid-liquid two-phase flow is predicted with wear equation. A systematic analysis on the wear mechanism of the centrifugal pump volute wall is carried out deeply, including the volute wall wear region, wear rate, and the relationship among inlet flow rate, particle concentration, and particle size. The predicted high erosion intensity area shows good agreement with the experimental erosion area, and the predicted and experimental areas are both located at the volute angle of 180° and near tongue. Therefore, the wear equation put forward in the present study is effective for estimating the erosion intensity and predicting the erosion area around the volute casing of a centrifugal pump.

Numerical model of particle deposition on wet fin surfaces of heat exchanger under dehumidifying conditions

Dusty particles may easily deposit on fin surfaces of heat exchangers under dehumidifying conditions and thus seriously deteriorate the heat transfer performance. The purpose of this study is to develop a numerical model for simulating the dusty particle deposition on wet fin surfaces in practical working processes, including the shape and mass of the deposited dusty particles in the process of particle-capturing by condensate water and that of particle adhesion on wet particulate layer. The prediction method of the dusty particle deposition in the process of particle-capturing by condensate water is to simulate the motion trajectories of all particles in the air flow at first and then to choose those particles intersecting with the water surface as deposited. The prediction method of the dusty particle deposition in the process of particle adhesion on wet particulate layer is to calculate the critical sticking velocity at first and then to choose those particles with the impact velocity being smaller than the critical sticking velocity as deposited. The validation results show that, the predicted shape of wet particulate layer agrees well with the experimental images, and the predicted mass of deposited particles agrees with 91% of the experimental data within a deviation of ±20% and the mean deviation is 11.8%. Prediction results of the quantitative influence of operation conditions with this model show that the parameters of inlet air relative humidity and particle concentration are the two most important factors on dusty particle deposition on wet fin surfaces.

In-situ experimental investigation on the growth of aerosols along the absorption column in post combustion carbon capture

The amine-based post combustion carbon capture process is one of the most advanced and preferred technologies to reduce CO2 emissions from point sources like power plants. The emissions of amine from capture plants is one of the biggest challenges faced by this technology. These emissions typically occur by means of aerosol/mist formation. To develop effective countermeasures, it is crucial to understand the dynamic behavior of aerosols within the column, which is currently not well understood. This manuscript presents the results from a study aiming to understand the mechanism of aerosol growth and its behavior along the absorber column in terms of particles number concentration, particle size distribution, and amine emissions. For that, a series of experiments were performed in TNO’s bench scale CO2 capture plant using 30 wt% monoethnolamine (MEA) as solvent. For a SO3 and CO2 concentrations of 5.25 ppm and 12.5 vol.% in the flue gas, MEA emissions at the top exit of the column were recorded as 1051 mg/Nm3 (with vapour emissions of 381 mg/Nm3). In the absence of SO3 in the flue gas, inlet particle concentration was 2.71 × 107/cm3 and resulting MEA emissions reduced by 63.5%–383 mg/Nm3.From the bottom of the column until the point of maximum temperature, the MEA content in the vapour phase was consistent with the volatility of the solvent. After this point it drastically increases to 1051 mg/Nm3. Both the number of particles and the total particle mass has lowered from the bottom to the top of the column. For the benchmark test, inlet and outlet total particle concentration were found to be 6.24 × 107/cm3 and 2.3 × 107/cm3 respectively, while total particle mass is 2.22 mg/m3 at inlet and 1.32 mg/m3 at outlet. Particles with a dimeter below 0.006 μm contribute the most to total particle concentration both at the inlet (50%) and outlet (32%), while particles with diameter of 0.087 μm contributes the most to the total particle mass at inlet (47%) and outlet (55%). The measured total mass of particles was in the order of magnitude of 1 mg/m3. This is much lower than the expected aerosol mass emissions, in the order of magnitude of 1 g/Nm3 based on FTIR emissions.No particles larger than 0.147 μm were recorded, which might explain the low total mass recorded. The cause for this is still under investigation, but it suggests that the sampling procedure may induce systematic errors to the measurements. Nonetheless, the observations from this study have given further insight into the aerosol dynamics in the absorber column and corresponding emissions.

Chemical composition and morphology of particles emitted from a wet flue gas desulfurization (WFGD) system

The chemical composition and morphology of particles emitted from a WFGD system were analyzed. The inlet particle diameter, inlet particle concentration and liquid/gas ratio (L/G), were all found to affect particle emissions. Smaller diameter particles and higher inlet particle concentrations resulted in increases Si and total particle mass concentrations. The elemental mass concentrations of the emitted particles were mainly derived from inlet components, along with low levels of Ca, S, AL, Mg and other trace elements carried from slurry in the spray scrubber, with the Ca and S content of emitted particles predominantly being carried from the slurry. The particles emitted from WFGD were mainly fine particles, with up to 96% and 50% of particles being below 2.5μm and 1μm, respectively. Particles with a diameter below 0.5μm accounted for only 8.89%, 7.6% and 16.4% of particle emissions when the inlet particles sizes were 38.55μm 13.42μm and 6.16, respectively. The mean diameter of particles emitted from the WFGD system ranged between 0.6 and 1.2μm. These results confirm the particle removal ability of the WFGD system and improve our understanding of the chemical composition and morphology of particles emitted from WFGD systems, as well as their impact on the atmospheric environment.

The effect of particle humidity on separation efficiency for an axial cyclone separator

The objective of this study is to investigate the effects of particle humidity on the inlet particle size distribution, overall efficiency, grade efficiency and cut size diameter for an axial cyclone separator with inner diameter of 150 mm. The collection and grade efficiencies of the cyclone separator were measured by on-line method for inlet velocities, particle concentration and particle humidity in the ranges of 12–18 m/s, 30–500 mg/m3 and 8–30‰, respectively. By employing a set of fixed parameters for inlet velocity and particle concentration, the effect of particle humidity on separation efficiency was investigated. The experimental results show that the volume ratio of larger particle increases with the increasing of particle humidity due to particle agglomeration. When the inlet velocity and particle humidity remain constant, the collection and grade efficiencies improve greatly as the increasing of the particle concentration because of the particle aggregation. However, it was noticed that the grade efficiencies did not always increased with the increasing of particle humidity under the same conditions of inlet velocity and particle concentration. The trends of grade efficiency curves for different particle humidity change at the particle diameter of approximately 10 μm. The grade efficiency improves with the increasing of particle humidity when the particle diameter is larger than 10 μm, while a contrary tendency is observed when the particle diameter is smaller than 10 μm.

Analysis of the pressure fluctuation in the flow field of a large-scale cyclone separator

Flow field in a cyclone separator is not stable and show complex dynamic properties. Dynamic pressure signals were measured at different positions in a large-scale gas-solid cyclone separator such as the vortex finder, outer vortex and inner vortex, using a micro-differential pressure transmitter with different inlet gas velocities and inlet particle concentrations. Power spectral density (PSD) and fast Fourier transform (FFT) were used to analyze the characteristics of these dynamic pressure signals. The results showed that the PSD of the outer vortex was divided into two parts: part 1 in a low frequency region (0–n Hz) with high magnitude and part 2 in a high frequency region (n–50 Hz) with low magnitude. The dominant frequency region was related to outer vortex, and its range and magnitude increased with increased inlet gas velocity. There was a dominant frequency in the vortex finder of the cyclone separator, which was related to inner vortex rotation. The dominant frequency increased with increased inlet gas velocity and decreased with increased particle concentration. Using data processing methods, including an FFT filter and standard deviation, particle effects were found to be focused in lower frequency region parts, while the effects were not linearly depend on the particle concentration. Furthermore, there were special pressure transfer characteristics in the cyclone separator, which resulted in forming the pressure fluctuation. Through PSDs and the coherence analysis of the dynamic pressure in two positions in the vortex space of the cyclone separator, the outer vortex was found to induce a low frequency range pressure fluctuation with high magnitude and the inner vortex induced a new main frequency because of the periodically-rotating flow behavior. Considering the resonance phenomenon, the natural frequency of cyclone separator should be kept away from the frequency of pressure fluctuation, which concentrated below 50 Hz.

Enhancement of PM2.5 Cyclone Separation by Droplet Capture and Particle Sorting.

Fine particulate matter (PM2.5) is one of the most serious environmental pollutants worldwide, and efficient separation technologies are crucial to the control of PM2.5 emission from industrial sources. We developed a novel method to enhance PM2.5 cyclone separation by droplet capture and particle sorting using a vertical reverse rotation cyclone (VRR-C, inlet particle-sorting cyclone). The separation performances of common cyclone (CM-C) without droplets, CM-C with droplets, and VRR-C with droplets were compared in terms of energy consumption, overall separation efficiency, particle grade efficiency, outlet particle concentration, and outlet particle size distribution. The results show that the highest overall separation efficiencies were 51.7%, 89.9%, and 94.5% for CM-C without droplets, CM-C with droplets, and VRR-C with droplets, respectively, when the mean diameter of the inlet particles was 3.2 μm and the inlet particle concentration was 500 mg/m3. The PM2.5 grade efficiency of VRR-C with droplets was as high as 89.8%, which was 6.2% and 49.9% higher than those of CM-C with droplets and CM-C without droplets, respectively. This novel method was first successfully applied to the deep purification of product gas in the methanol-to-olefin (MTO) industry, for which the separation efficiency of fine catalyst particles was considerably improved.

Simple self-diagnostic method to identify the abnormal functioning of a scanning mobility particle sizer

This study suggests a simple self-diagnostic method for identifying the abnormal functioning of a scanning mobility particle sizer (SMPS). Under the operating conditions of a laboratory-made electrostatic precipitator, where the collection efficiency is expected to be at maximum, the efficiency against neutralized particles was measured using a malfunctioning SMPS. The efficiency was compared with the theoretical maximum collection efficiency. The difference in efficiency between experimental and theoretical collection efficiencies was used as an indicator of an SMPS malfunction. Moreover, the effects of the flow rate, neutralizer condition, and inlet particle concentration on the error signal were investigated. The error signal was shown to properly reflect the operational state of the SMPS; thus, a malfunction can be easily confirmed without the need for accurate comparison data. The error signal was also shown to be robust against a radioactive source, period of neutralizer use, and flow rate. The signal was clear when the particle concentration was sufficiently high, but tended to fade with a decrease in the inlet particle concentration. The suggested self-diagnostic method can be used to check the malfunctioning of a SMPS before a main experiment or to determine whether the SMPS requires calibration.

Evaluation of the can velocity effect on a bag filter

In this study, the effects of can velocity on the performance of a pilot-scale bag filter dust collector were examined. Test bag filters were made of polyester fabric and had a 156mm diameter and a 3m length. The cleaning interval of the pulse-jet cleaning system and the effects of inlet particle concentration with various can velocities were considered. When the dust collector was operated with insufficient can velocity, an unreasonable increase in the cleaning interval was observed. The cleaning interval decreased with the increased can velocity. Furthermore, under the unsuitable can velocity condition, the increasing tendencies of the cleaning interval and dust emission by decreased inlet particle concentration deviated from the expected theoretical tendency. Therefore, the appropriate can velocity should be selected in a pilot-scale experiment for improving the prediction of actual-scale dust collector performance.

Study on the removal of fine particles by using water in a rotating packed bed

AbstractThis study presented an experimental investigation on the capture of fine particles from gas stream by water in a rotating packed bed (RPB). Experiments were carried out to investigate the effects of different operating conditions including packing types, rotation speed, gas‐liquid volumetric ratio, inlet particle concentration, and gas temperature on the removal efficiency of fine particles. The overall removal efficiency of fine particles can reach 98 % under the optimal operating conditions, which are a rotation speed of 1200 rpm, a gas‐liquid volumetric ratio of 600, a gas temperature of 100 °C, and the use of fine metal gauze packing. In addition, the correlation of removal efficiency of fine particles was deduced. It is observed that the predicted removal efficiency and outlet concentration of fine particles are in good agreement with the experimental values, with deviations within 10 % and 20 % respectively. This process exhibits the potential application of RPBs in simultaneous removal of fine particles and SO2 by liquid solution.

Experimental and CFD study of particle deposition on the outer surface of vortex finder of a cyclone separator

Based on the industrial background of carbonaceous deposition in secondary cyclone separators of FCC units, this paper focuses on particle deposition pattern and investigation of factors on deposition on the outer surface of vortex finder of secondary cyclone. Particle deposition experiments were carried out with a 500mm-diameter cyclone in a cold-model pilot test platform. Deposition patterns were obtained under different inlet gas velocities, particle concentrations and experimental materials etc. Furthermore, discrete phase model (DPM) was applied to obtain particles distribution in the annular space and the effect of particle properties and operational conditions on mass of deposited particles was also investigated. In addition, Gas shielding method was preliminarily explored to avoid particle deposition. The results will provide experimental evidence for analyzing the deposition process and help to further understand the deposition mechanism.