Investigation of the performance of bipolar transverse plate ESP in the sintering flue control

In order to improve the particle collection efficiency of the electrostatic precipitator (ESP), a transverse plate ESP with bipolar discharge electrodes is proposed. The simulations of the velocity distribution have shown that when the inlet velocity is 1 m/s, within the range of 40 mm from electrode plate, the average velocities of windward side and leeward side are less than 0.7 m/s and 0.3 m/s respectively. It is clear that the velocity near the collection electrode plate of this bipolar ESP is much lower than that of the ordinary ESP at the same inlet velocity. This low velocity can lead to higher efficiency for fine dust collection due to the less dust re-entrainment in ESP. It is also found that the average velocities are getting lower when the distance between plates electrodes are greater than 150 mm in accordance with the simulations. The voltage current characteristics of the bipolar ESP are superior to the ordinary ESP. The pressure drop of the bipolar ESP is about 30% higher than that of the ordinary one. The dust penetration of the bipolar ESP is about 54% less than that of the ordinary ESP when the sintering dust with 25.405 μm mass median diameter is used as the test particulate under the condition of the electric field from 2.1 kV/cm to 3.2 kV/cm and the velocity from 1.0 m/s to 1.5 m/s.     

EHD flow in a wide electrode spacing spike–plate electrostatic precipitator under positive polarity

In this work, results of two- and three-dimensional particle image velocimetry (PIV) measurements of the flow velocity fields in a wide spacing spike–plate electrostatic precipitator (ESP) under positive polarity are presented. A DC voltage of positive polarity (up to 28 kV) was applied to the spike electrode. The average gas flow velocity was 0.6 m/s. The PIV measurements were carried out in four planes perpendicular to the plate electrodes. Three parallel planes passed along the ESP while one plane passed across the ESP duct. The results show that electrohydrodynamic (EHD) secondary flow with relatively strong vortices exist in the ESP. The EHD secondary flow pattern depends on applied voltage and measuring plane position in respect to the spike tip. The strongest vortices occur in the plane passing through the tip of the upstream-directed spike. These relatively strong EHD vortices may hinder collection of the particles in the diameter range of 0.1–1 μm in the wide electrode spacing spike–plate ESPs.     

Using an improved electrostatic precipitator for poultry dust removal

Pubic concerns related to particulate matter emissions from animal housing operations are increasing. The goal of this study was to custom develop a simple and low cost electrostatic precipitator (ESP) for poultry dust control. The performance of the improved electrostatic precipitator (iESP) to remove a test aerosol was evaluated under a series of operating voltages between ?60 kV and 60 kV. The mass and size distributions of the particles were measured by a cascade impactor. The overall dust removal efficiency ranged from 37% to 79% with the maximum efficiency obtained at ?30 kV. The iESP shows high removal efficiencies for particles less than 2.1 μm.     

Positive effects of thermosonication in Jamun fruit dairy dessert processing

The effects of thermosonication processing (TS, 90 °C, ultrasound powers of 200, 400, and 600 W) on the quality parameters of Jamun fruit dairy dessert compared to conventional heating processing (high-temperature short time, (HTST), 90 °C/20 s) were evaluated. Microbiological inactivation and stability, rheological parameters, physical properties, volatile and fatty acid profiles, and bioactive compounds were assessed. TS provided more significant microbial inactivation (1 log CFU mL⁻¹) and higher microbial stability during storage (21 days) than HTST, with 3, 2, and 2.8 log CFU mL⁻¹ lower counts for yeasts and molds, aerobic mesophilic bacteria, and lactic acid bacteria, respectively. In addition, TS-treated samples showed higher anti-hypertensive (>39%), antioxidant (>33%), and anti-diabetic (>27%) activities, a higher concentration of phenolic compounds (>22%), preservation of anthocyanins, and better digestibility due to the smaller fat droplet size (observed by confocal laser scanning microscopy). Furthermore, lower TS powers (200 W) improved the fatty acid (higher monounsaturated and polyunsaturated fatty acid contents, 52.78 and 132.24%) and volatile (higher number of terpenes, n = 5) profiles and decreased the atherogenic index. On the other hand, higher TS powers (600 W) maintained the rheological parameters of the control product and contributed more significantly to the functional properties of the products (antioxidant, anti-hypertensive, and anti-diabetic). In conclusion, TS proved to be efficient in treating Jamun fruit dairy dessert, opening space for new studies to define process parameters and expand TS application in other food matrices.     

Performance characteristics between horizontally and vertically oriented electrodes EHD ESP for collection of low-resistive diesel particulates

The novel electrohydrodynamically-assisted electrostatic precipitator (EHD ESP) was developed to suppress particle reentrainment for collection of low resistive diesel particulates. The collection efficiency was compared between vertically and horizontally oriented electrodes of the EHD ESP using 400 cc diesel engine. The particle size dependent collection efficiency was evaluated for the particle size ranging in 20 to 5000 nm using a scanning mobility particle sizer (SMPS) and a particle counter (PC). Both horizontally and vertically oriented EHD ESP showed an excellent suppression of particle reentrainment. However, the horizontally oriented electrode EHD ESP showed significantly improved for the particle size of 300–500 nm in comparison with vertically oriented electrode EHD ESP, resulting in more than 90% collection efficiency for all particle size range. The EHD ESP has high potential especially for highly concentrated marine diesel engine emission control.     

Experimental investigation on charging characteristics and penetration efficiency of PM2.5 emitted from coal combustion enhanced by positive corona pulsed ESP

The electrostatic precipitator (ESP) has been extensively used for collecting aerosol particles emitted from coal combustion, but its collection efficiency of PM2.5 (Particulate matter whose aerodynamic diameter is less than 2.5 μm) is relatively low due to insufficient particle charging. The positive pulsed ESP is considered to enhance particle charging and improve collection efficiency. A laboratory-scale pulsed ESP with wire-plate electrode configuration was established to investigate the particle charging and penetration efficiency under controlled operating conditions of different applied impulse peak voltages, impulse frequencies, dust loadings and residence times. The results show that most particles larger than 0.2 μm are negatively charged, while most particles smaller than 0.2 μm are positively charged. For a given operating condition, the particle penetration efficiency curve has the highest penetration efficiency for particles with a diameter near 0.2 μm, and there is always a negative correlation between the particle penetration efficiency and the average number of charges per particle. Under the same operating conditions, the particle penetration efficiency decreases with increasing impulse peak voltage and impulse frequency, but increases as the dust loading increases. The results imply that residence time of 4 s is optimum for particle charging and collection. PM2.5 number reduction exceeding 90% was achieved in our pulsed ESP.     

Electrohydrodynamic flow patterns and collection efficiency in narrow wire-cylinder type electrostatic precipitator

Recently, narrow electrostatic precipitators (ESPs) have become a subject of interest because of their possible application for the cleaning of the exhaust gases emitted by diesel engines. Diesel engines emit fine particles, which are harmful to human and animal health. There are several methods for decrease particulate emission from a diesel engines, but up to now, these methods are not enough effective or very expensive. Therefore, an electrostatic precipitation was proposed as an alternative method for control of a diesel particulate emission.In this work, results of electrohydrodynamic (EHD) secondary flow and particle collection efficiency measurements in a narrow wire-cylinder type ESP are presented. The ESP was a glass cylinder (300 mm × 29 mm) equipped with a wire discharge electrode and two collecting cylinder-electrodes. A 0.23 mm in diameter and 100 mm long stainless-steel discharge wire electrode was mounted in the center of the cylinder, parallel to the main flow direction. The collecting electrodes were made of stainless steel cylinders, each with a length of 100 mm and inner diameter of 25.5 mm. An air flow seeded with a cigarette smoke was blown along the ESP duct with an average velocity of 0.9 m/s.The EHD secondary flow was measured using 2-dimensional particle image velocimetry (PIV) method. The PIV measurements were carried out in the wire electrode mid-plane, perpendicularly to the wire and the collecting electrodes. The results show similarities and differences of the particle flow in the wire-cylinder type ESP for a negative and a positive DC voltage polarity.The collection efficiency was calculated from the fractional particle concentration. The fractional particle concentration was measured using the optical aerosol spectrometer. The results of the fractional collection efficiency confirmed the common view that the collection efficiency of fine particles in the ESP increases with increasing voltage and it is higher for negative voltage polarity and decreases when decreasing particle diameter.     

Design and evaluation of a unipolar aerosol charger to generate highly charged micron-sized aerosol particles

In this study, a unipolar charger for generating highly charged microparticles was designed and its performance was evaluated both theoretically and experimentally. The measured particle charge number and corona current of the charger were in good agreement with the theoretical results from FLUENT. The experimentally determined average particle charge number of 1 μm PSL under an applied voltage of 8 kV was 128, which agreed well with the theoretically predicted and simulated values of 118 and 121, respectively. Computational calculations revealed the average charge of 10 μm particles to be 7560 at an applied voltage of 8 kV.     

Flow characteristics of a single stage EHD gas pump in circular tube

Characteristics of flow induced by electrohydrodynamic (EHD) gas pumps in circular pipe have been experimentally evaluated. Two tube diameters (61.8 mm and 127.8 mm) and two electrode gap distances (25 mm and 50 mm) have been considered. The gas pumps use eight evenly spaced emitting electrodes which are flush mounted on the tube wall. As such, flows induced by the pumps have a profile with a higher velocity near the wall and a lower velocity at the tube center. Experiments are conducted using positive corona discharge with voltage varying from 17.5 kV to 30 kV. The results show that the volume flow rate increases with the applied voltage but approaches an asymptotic value before sparkover takes place. From the present results, several important implications for the practical engineering applications are presented.     

Electrohydrodynamic gas pump in a vertical tube

The characteristics of electrohydrodynamic (EHD) gas pumps have been experimentally evaluated. Two tubes of different size were used to house the EHD gas pumps. Experiments were conducted using positive direct current with voltage varying from 13 kV to 30 kV. The applied voltage at which flow was induced correlates well with the electrode spacing. Air flows with a uniform velocity profile were induced in the smaller tube and an inverted parabolic profile in the larger tube. The results also show that the ionic wind velocity increases to a maximum value and then decreases to an asymptotic value.     

Experimental study on electrostatic removal of high-carbon particle in high temperature coal pyrolysis gas

A high-temperature electrostatic precipitator (ESP) presents a good solution for hot gas cleaning, which can remove fly ash from pyrolysis gas at temperatures higher than the tar dew point. In this paper, the characteristics of negative DC corona discharge in air and simulated coal pyrolysis gas were studied. The removal of coal pyrolysis furnace fly ash (ash A) was investigated and compared with that of coal-fired power plant fly ash (ash B) in ESP with a temperature ranging from 300?K to 900?K. The current density of simulated gas was higher than that of air under the same discharge voltage and at different temperatures. The simulated gas also had a higher spark voltage and a lower onset voltage compared with air. The fractional collection efficiency of ash A was lower for particles with diameters of larger than 0.1?µm at high temperature, compared with ash B. A lower collection efficiency in simulated gas was obtained for particles with diameters of less than 0.1?µm compared with air. The collection efficiency of submicron particles in simulated gas was usually higher than it in air, especially for particles with diameters of less than 0.04?µm. In simulated gas, the overall collection efficiency of ash A was obviously lower than that of ash B, especially at high temperature. From 300?K to 700?K, the collection efficiencies of both ash samples were as high as above 93%, but the collection efficiency of ash A in simulated gas decreased to 78.7% at 900?K.     

Electrohydrodynamic flow and particle collection efficiency of a spike-plate type electrostatic precipitator

In this work, the results of electrohydrodynamic (EHD) secondary flow and particle collection efficiency measurements in a spike-plate type electrostatic precipitator (ESP) are presented. The EHD secondary flow was measured using 2- and 3-dimensional particle image velocimetry (PIV) method under the negative DC voltage. The PIV measurements were carried out in several cross-sectional planes along and across the ESP duct. The results show a complex and turbulent flow structure in the ESP. The EHD secondary flow significantly depends on applied voltage and measuring cross-sectional plane position in respect to the spike tip. The partial collection efficiency of the ESP was measured for negative and positive DC voltage. The particle concentration with and without discharge was measured at the ESP exit using an optical aerosol spectrometer.     

Thermosonication as an alternative method for processing,extending the shelf life,and conserving the quality of pulque: A non-dairy Mexican fermented beverage

The aim of this study was to evaluate thermosonication as an alternative method for the pasteurization of pulque in order to improve its shelf life and retain its quality parameters.Thermosonication was carried out at 50 °C using amplitudes of 75% (for 6 and for 9 min), 85% (for 4 and for 6 min), and 95% (for 3 and for 5 min). These were the optimal conditions found for processing pulque by thermosonication. Physicochemical (acidity, color, alcohol content, and sensory analysis) and microbiological (lactic acid bacteria and yeasts) parameters were determined during 30 days for storage at 4 ± 1 °C. Conventional pasteurization (63 °C, 30 min) and raw pulque were used as controls. According to the results, the shelf life of pulque was extended up to 24 days storage at 4 °C. After this time, the quality of beverage decreased, due that the microbial load increases. Thermosonication treatments at 75% and 85% showed a higher content of LAB (6.58–6.77 log CFU/mL) and yeasts (7.08–7.27 log CFU/mL) than conventional pasteurization (3.64 log CFU/mL of LAB and 3.97 log CFU/mL of yeasts) at 24 days of storage. Raw pulque demonstrated up to 7.77 log CFU/mL of yeasts and 7.51 log CFU/mL of LAB. Pulque processed by thermosonication exhibited greater lightness, sensory acceptance, a maximal acidity of 0.83 g/lactic acid, and an alcohol content of 4.48–4.95% v/v. The thermosonication process preserves sensory and physicochemical properties better than conventional pasteurization. Lactic acid bacteria such as Lactobacillus kefiri, Lactobacillus acidophilus, and Lactobacillus hilgardii and yeasts such as Saccharomyces cereviasiae were identified in thermosonicated pulque.     

Enhancement of submicron particle electrostatic precipitation using dielectric barrier discharge in wire-to-square tube configuration

The aim of the present parametric study is to enhance the performances of a wire-to-square tube electrostatic precipitator (ESP) for the collection of submicrometer particles using dielectric barrier discharge (DBD). The input parameters under study are: the high voltage waveform, the wire electrode diameter, the collection electrode dimensions (width, discretization and number of collection sides) and the tube cross-section. The electrical measurements show that the discharge mode of the ESP is rather homogeneous. The particle collection efficiency as determined from aerosol spectroscopy measurements is higher at high applied voltage and within a certain frequency range. The parametric study of the ESP points out that using thicker wire electrodes as well as collection electrodes with different number of sides does not deteriorate the ESP performance. However, the penetration decreases with larger or discretized collection electrodes and larger tube cross-sections.     

Experimental study of corona jet produced from a circular tube fitted with a nozzle

The flow characteristics of a corona jet, which is produced from a single needle electrode positioned at the centerline of a circular tube fitted with a grounded stainless-steel nozzle at one end of the tube, is experimentally evaluated. Six nozzles with two diameter ratios and three taper angles are evaluated for their effectiveness in accelerating the jet produced by corona discharge with positive polarity. To determine the maximum jet velocity and volume flow rate, experiments have been conducted at a voltage ranging from corona onset (5 kV) to sparkover (approximately 12.5 kV) at an increment of 2.5 kV. The results show that the jet velocity increases with the applied voltage. The maximum velocity occurs at the center line but its value decreases as the jet expands downstream. In addition, the results show that a nozzle with a smaller diameter ratio does not always perform the best in accelerating the flow or producing the maximum volume flow rate. The nozzle's taper angle further accentuates the result produced by the diameter ratio. The implications from the present results for actual applications are provided.     

Electrospray with electrostatic precipitator enhances fine particles collection efficiency

Electrospray was combined with an electrostatic precipitator (ESP) to enhance the collection efficiency of monodisperse nanometer-sized particles. The electrospray of deionized water produced water droplets with sizes ranging from 10 to 300 μm. The combination of the ESP with the electrospray enhanced collection of particles by 21–36% depending on the particle size. The combination of the ESP and the electrospray was also found to reduce the energy consumption of the ESP.     

Transients and efficient generation of electron beams in the pulsed wide-aperture glow discharge

The quasi-continuous wide-aperture glow discharge in helium at pressures from 1.2 to 6.0 Torr is studied. It is found that electron beam generation efficiency η is higher than 96% in the pressure range 1.2–3.0 Torr at voltages from 1.0 to 2.6 kV. The maximum power was ≈ 0 kW at 6 Torr and a voltage across the discharge gap of 2.6 kV. Under these conditions, the beam generation efficiency is about 80%. The pressure and voltage dependences of main parameters of the discharge are explained from the standpoint of its photoemission nature.     

Use of electrostatic precipitation for excess ion trapping in an electrical aerosol detector

In this paper, the technique of electrostatic precipitation was used to remove excess ions from a mixture with charged particles before collection on a filter in a Faraday cup electrometer of an electrical aerosol detector. The ion precipitator part of the detector was designed, constructed, and evaluated. An analytical model was developed to investigate ion and particle transports due to diffusion and space charge effects inside the ion precipitator. Experimental investigations were carried out for positive ions, the positively applied voltage at the wire electrode ranged from 10 to 150 V, ion flow rates ranged from 5 to 15 L/min, and the radial distance of the inlet was 0.15 and 14 mm at a fixed separation between the wire and outer electrodes. The calculation results showed that all charged particles of 10 nm in diameter could pass through the ion precipitator smoothly without precipitation at the outer electrode. For all ion flow rates, an increase in ion trap voltage produced an increase in ion collection efficiency of the precipitator. Experiments confirmed that the efficiency of the ion precipitator could increase to 99% at an ion trap voltage larger than 100 V for all ion flow rates.     

EHD flow measured by 3D PIV in a narrow electrostatic precipitator with longitudinal-to-flow wire electrode and smooth or flocking grounded plane electrode

In this work, results of three-dimensional (3D) Particle Image Velocimetry (PIV) measurements of the electrohydrodynamic (EHD) flow velocity fields in a narrow electrostatic precipitator (ESP) with a longitudinal-to-flow placed wire electrode are presented. The ESP was a narrow transparent acrylic box (90 mm×30 mm×30 mm). The electrode set consisted of a single wire discharge electrode and two plane collecting electrodes. Either two smooth stainless-steel plates or two stainless-steel plane meshes with nylon flocks were used as the collecting electrodes. The 3D PIV measurements were carried out in two parallel planes, placed longitudinally to the flow duct. The positive DC voltage of up to 9.5 kV was applied to the wire electrode through a 10 MΩ resistor. The collecting electrodes were grounded. The measurements were carried out at a primary flow velocity of 0.5 m/s. Obtained results show that the flow patterns for the smooth-plate electrodes and for the flocking plane electrodes are similar in the bulk of the flow. However, the flow velocities near the flocking plane electrodes are much lower than those near the smooth-plate electrodes. This is a beneficial phenomenon, because the lower the flow near the collecting electrodes, the lower re-entrainment of the particles deposited on the collecting electrodes occurs.     

Electrostatic precipitation of fine particles with a bipolar pre-charger

A laboratory electrostatic precipitator (ESP) together with a bipolar pre-charger has been designed for studying charge-induced agglomeration and fine particle collection. In terms of particle numbers, the ESP collection efficiency drops to its minimum of near 90% for particles with diameters of near 0.2 μm and 3 μm. For other particles, its value is around 94%–95%. By using the bipolar pre-charger, the grade efficiency can be significantly increased for all particle sizes due to the charge-induced particle agglomeration. The grade collection efficiency rises to about 95%–98% for all size particles.