Dust Resistivity Research Articles

Abatement of environmental pollution by research on electrical resistivity and conductivity mechanism of poplar dust

Under conventional processing conditions, the resistivity of wood dust is in the range of insulating materials, which can induce a dust cloud explosion when there are static sparks. This paper took the fast-growing poplar wood commonly used in Chinese wood processing and studied the effects of moisture content, temperature, and particle size on the electrical resistivity value of sanded wood dust. Orthogonal analysis was conducted on the influencing factors. The results showed that the influence of moisture content on electrical resistivity was the most significant factor, followed by temperature and particle size. Further experiments have shown that when the moisture content increased from 6% to 32%, the resistivity decreased from 109 Ω cm to 105 Ω cm, which reached the suitable resistivity range of static discharge method. The ion concentration of wood dust extracted in cold water and hot water and the resistivity of poplar dust residue after extraction were determined. Nine metal ions (a total of 105.02 mol/g) were detected in cold-water extract, and the concentrations of K+, Na+, Mg2+ and Ca2+ accounted for 99.8%. The original poplar dust and the extracted poplar dust were measured and analyzed. The changes in water-soluble ion content, functional groups, crystallinity, and complexes of the wood dust before and after ion dissolution, jointly led to changes in the electrical resistivity of the wood dust (a difference of 2–4 orders of magnitude). It was verified that the way wood dust conducts electricity is through ion conduction. There were more abundant capillary system structures between poplar dust particles, allowing water-soluble ions to move more freely with water channels. The larger specific surface area and higher temperature also promoted the dissolution of water-soluble ions, which affected the electrical resistivity.

Experimental study on improving salt resistance of dust suppressing foam with polymers

Mine dust is a prevalent pollutant generated during the mining process, often leading to explosion accidents and causing pneumoconiosis. Foam dust suppression technology has emerged as a promising method for efficient dust control due to its high-efficiency dust collection and ease of use. However, the application of foam in the field has revealed higher concentrations of inorganic salts in the mine dust suppressants, resulting in suboptimal foaming performance. As a result, additional foaming agent and increased concentration are often required to achieve the desired effect, which escalates the cost of mine dust control. To address this issue, this study proposes optimizing the performance of mine dust suppression foam through the incorporation of polymers with excellent salt resistance. In this investigation, foam liquids comprising xanthan gum (XG) and sodium carboxymethyl cellulose (CMC) were tested using FoamScan to evaluate their foaming performance and foam stabilization at various concentrations of inorganic salt. Additionally, the rheological properties of the foam liquids were analyzed by measuring the viscoelastic modulus using an interfacial rheometer. Experimental results demonstrated that the addition of XG and CMC did not compromise the foaming ability of sodium fatty alcohol polyoxyethylene ether sulfate (AES). Moreover, the liquid-carrying capacity of bubbles, in terms of foam stability, was enhanced. Specifically, the foam stabilization remained relatively stable when the XG concentration exceeded 0.5‰, even under different salt concentrations. Interfacial rheological tests revealed that the addition of XG substantially increased the viscoelastic modulus of the foam liquid. Furthermore, the phase angle remained below 45°, indicating the dominant role of the elastic modulus in the foam liquid, resulting in improved bubble resistance to interference and deformation. This experimental study successfully resolved the issue of poor stability in mine dust suppression foam caused by high salt content during the foam preparation process. The findings can significantly contribute to the widespread adoption and application of dust suppression foam technology in mining operations.

Study on the performance and mechanism of extracellular polymer substances (EPS) in dust suppression

Microbial dust suppressants are a green method to prevent and control coal dust, but the role of extracellular polymer substances (EPS) has rarely been studied. Therefore, this paper studied the effect of different EPS concentrations (0, 0.05%, 0.10%, and 0.15% w/v) on dust suppression. The results showed that the dust suppression efficiency increased with the EPS concentration. When the EPS concentration reached 0.15%, the evaporation resistance and wind erosion resistance of coal dust were improved by 37.5% and 89.0%, respectively, compared with water-treated samples (p < 0.05). The contact angle of EPS-added samples was lower than that of water-treated samples and decreased to 57.35° at the highest concentration (0.15%), indicating that EPS enhanced the wettability and reduced the surface tension. Furthermore, changes in the protein and polysaccharide contents in EPS before and after dust suppression showed that the adhesion effect of polysaccharides was greater during dust suppression.

Investigations on Three-Section Plate-Type Electrostatic Precipitators Used in Thermoelectric Power Plants

Dust emissions must be managed and reduced as much as possible to safeguard the environment and human health. Plate-type electrostatic precipitators have been used to decrease pollution in a number of sectors, particularly for applications needing massive volumes of gas to be dedusted at high dust concentrations and temperatures. This paper examines large-capacity plate-type electrostatic precipitators with three sections used in a coal-fired thermal power plant. Using simulations and experiments, the collection efficiency (in different ways of supplying sections, without and with sections rapping), the influence of dust resistivity and a dust layer on the surfaces of collection electrodes, the electrical parameters (voltage, current density, and space charge density) for the sections of the electrostatic precipitators, and the electrical parameters of the power sources (voltage, current, power, and power factor) are studied. A higher dust resistivity will cause a change in the shape of the voltage delivered to the sections, an increase in the average voltage from sections, and a decrease in collecting efficiency (by a few percent). A greater degree of intermittence alters the current-voltage characteristics of the sections, decreases the current across the sections, and improves collection efficiency. The density of space charges increases with the degree of intermittency and is highest at the input section. With increasing thickness of the dust layer on the collection electrodes, the collection efficiency increases. PM10 dust particles (which have a lower migration speed) are the hardest to collect with ESPs. When the sections are rapping, PM 20–30 dust particles are more difficult to collect because their migration speeds decrease significantly (compared to the situation when the sections are not rapping). The operation of the power sources of the ESP sections is dynamic, being controlled by the regulators, and the current (or current density), depending on the voltage characteristics, changes permanently (at intervals of a few seconds). The power sources of the sections are deforming consumers (the current is much different from the sinusoidal form).

Assessment of explosion risk for wood dust in a ventilation-dust separation installation, by determining the concentration of total dust in suspension inside of the installation

Most of combustible dusts present both fire and explosion hazard. Explosion may occur at certain concentrations of dust mixed with air and in the presence of an ignition source. The threat posed by this real danger was confirmed by the events that took place in economic units such as: feed factories, wood products, textile industry, steel, etc. Among the parameters of explosiveness of combustible dust, which can cause an explosion, we mention: maximum explosion pressure, lower explosion limit, explosive index, minimum ignition energy, electrical resistivity of dust, minimum ignition temperature of dust layer and cloud, particle size and concentration of dust in suspension. The current paper presents the results of determinations of combustible wood dust concentrations, performed at an important economic unit, manufacturing veneer and wood panels, at a dusting ventilation installation composed of fan, cyclone and textile filter. These determinations were made in the pipe connecting the fan and the bag filter, to assess possible danger of explosion in the pipe, by relating the measured concentration to the lower explosion limit (concentration of wood dust).

전기집진기의 운전온도와 NH₃가 집진율에 미치는 영향에 관한 연구

초록·키워드 목차 오류제보하기 Carbon neutrality, in which the amount of emission minus the absorption of greenhouse gas emissions becomes zero, is an international agreement to keep the earth"s temperature rise and it is an effort to maintain the guarantee for the earth"s future. However, the power supply and economic loss are inevitable to temporarily stop the thermal power plant, which accounts for 40% of the power generation. Therefore, it is unavoidable to reduce the total amount of dust emitted from currently operating facilities as much as possible and gradually switch to eco-friendly energy. The purpose of this study is to suggest the optimal operating conditions of an Electrostatic Precipitator by studying the effect of the input amount of NH₃, which adjusts the specific resistance of dust, and the operating temperature of the Boiler on the electric dust collection rate to reduce dust emission by collecting fine dust generated in thermal power plants. #Electrostatic Precipitator #NH₃ #Dust collection rate #Greenhouse gas Abstract1. 서론2. 전기집진설비의 이론적 고찰과 시스템분석3. 결론References

Experimental investigation and application of mine airflow purification and reuse technology

To solve the problem of dust concentration higher than the standard on the -415 m roadway in the Fankou lead-zinc mine, a self-made dedusting equipment consisted of chord grid is proposed in this paper. This equipment aims to purify the polluted airflow for deep ventilation in mine. First of all, an image observation is shown that three types of water films on the chord grid surface. Specifically, the chord grid is wetted by the fog drops to form water films and can remove dust from airflow. Then, it is measured that a total dust removal efficiency and resistance are resulted by a single layer of wet chord grids under the conditions of different nozzle out diameters, water spray pressure, and velocities. The results show that: The dust removal efficiency is higher at the experimental conditions meet this conditions(the velocity is 3.5 m/s, the nozzle outlet diameter is 2 mm, and the water supply pressure is 0.75 MPa); (2) The spray pressure seldom influences the resistance of dust removed equipment, whereas this resistance correlates positively with velocities and nozzle out diameters. Finally, one purification system is optimally designed according to the experimental, and applied it in the -415 m middle section of the FKLZM. The field test data showed that the mass concentration of dust meets the quality standard of fresh airflow in metal mine. • A self-made dedusting equipment for mine airflow purification and reuse was proposed. • The dedusting principle of water film making by chord grid was outlined. • The optimal parameters for site application was obtained base on the experiment data. • The developed purification system reduces the dust mass concentration to 0.39 mg/m 3 .

Preparation and performance of a biological dust suppressant based on the synergistic effect of enzyme-induced carbonate precipitation and surfactant.

To control the dust pollution caused by open-pit coal mining and reduce or avoid the secondary hazards of existing dust suppressants to the environment, a biological dust suppressant was prepared through the synergistic effect of a surfactant and an enzyme-induced carbonate precipitation. The optimal ratio of biological dust suppressant was determined, and the dust suppressive effect and dust consolidation mechanism of the biological dust suppressant were investigated. The results showed that the optimal biological dust suppressant had an alkyl polyglycoside (APG) concentration of 0.3 wt.%, a urea-CaCl2 concentration of 0.6 mol/L, and a urease to urea-CaCl2 volume ratio of 1:3. The wind erosion resistance of coal dust treated with this dust suppressant was enhanced by 86.69%. The adsorption of the biological dust suppressant by coal dust was mainly due to the electrostatic interaction between the surfactant and coal dust. The mineralization product of the dust suppressant was calcite-type CaCO3, which consolidated coal dust due to the formation of intermolecular hydrogen bonds between CaCO3 and coal dust.

Experimental Investigation of the Electrical Resistivity of Cement Dust

Electrical resistivity is one of the important particle–based factors influencing the performance of an Electrostatic Precipitator (ESP), a particulate control device commonly employed in most cement industries in Nigeria. Therefore, this study investigated the electrical resistivity of Cement Kiln Dust (CKD) across nine locally-operated cement manufacturing plants in Nigeria with the aim of tracing causes of performance problems associated with the ESP used for dust control in the plants. Samples of CKD were collected from the ESPs of these plants and tested for their resistance using the two probe method. The measured electrical resistivities were in the range of 108 – 1011 Ω·cm and showed strong dependence on temperature and slight variation with particle size. The CKD’s resistivity increases as temperature rises from ambient to about 250℃ and declines as temperature rises above 300℃; Nevertheless, the resistivities are adaptable for efficient ESP performance in the collection of cement dust.

A Numerical Investigation of the Effect of Dust Layer on Particle Migration in an Electrostatic Precipitator

ABSTRACT Electrostatic precipitation processes have been widely applied to remove particulate matter from flue gases in coal-fired power stations. A high negative voltage is usually applied to a discharge electrode so that the gases are ionized in such processes. When the suspended particles in flue gases enter the ionized space, they are electrically charged and deposited on collection plates to form the layer of particle packing. However, the dust layer generally exists during the precipitation of charged particles on the collection plate. The negative effect of precipitated dust layer on the collection plate causes the collection efficiency of electrostatic precipitator (ESP) to deteriorate seriously due to some critical factors, such as dust resistivity and thickness of accumulated dust. In this study, a simulation method by computational fluid dynamics method was applied to investigate the particle collection performance of the ESP system with and without a dust layer. Also, the detailed electric parameters and particle capture performance in the 2D wire-plate electrode configuration were simulated. The results show that the voltage-current characteristics and detailed distribution of electric field and ion charge density are completely different under various dust resistivity conditions. The effect of the dust layer is significant, which causes collection efficiency to decrease sharply with the increasing thickness (1–5 mm) of the dust layer. Furthermore, results indicate that when particles with higher resistivity enter the ESP, their migration velocity decreases sharply. In the case of 80 kV, when the dust resistivity is 1012 Ω·cm, the decline rate of particle migration velocity reaches 57.7%. Meanwhile, useful suggestions were provided to reduce the effects of dust layers by regulating particle properties and designing dust removal systems.

Influence of NO2 and SO2 on the specific resistance of dust in flue gas.

The influence of flue gas composition on the specific resistance of coal-fired fly ash is studied in this paper. We conclude that the negative electrons of NO2 and SO2 gases are strong. The probabilities of electron desorption on SO2 and NO2 negative ions are lower than that in air atmosphere at high temperature. Therefore, the introduction of SO2 causes NO2 to reduce the specific resistance value of coal-fired fly ash. When the pores on the surface of fly ash particles are filled with SO2, no change will occur in NO2, average pore size, pore volume, and specific surface area of fly ash particles, thereby resulting in fly ash that remains unchanged from the resistance value. When humidity increases, the surface conduction effect is greatly enhanced, and the specific resistance value is lowered considerably. Therefore, the specific resistance of dust can be reduced by humidification.

Investigation of dust resistivity for a fractioned biomass fly ash sample during poor combustion conditions with regard to electrostatic precipitation

It is well known that dust resistivity and particle size play a major role in electrostatic precipitation processes. The electrostatic precipitator design also has to be adapted for carbon rich fly ashes such as those found in heavy fuel oil combustion plants. In this work, an ash sample from an electrostatic precipitator downstream an industrial biomass boiler operated under poor combustion conditions was air classified into 5 particle size fractions. Those fractions were then analyzed regarding chemical composition, loss on ignition, particle size distribution and dust resistivity. Furthermore scanning electron as well as optical microscope images were taken to investigate particle structure and shape.Diverse types of particles were found in the different fractions, varying from unburned coal particles to inorganic sand-like particles. It was also found that chemical composition as well as resistivity varied significantly with different size fractions. During resistivity measurements, fluctuating voltage and current values were recognized, similar to what can be seen during the back-corona phenomenon, but found at medium resistivity values. Furthermore, suggestions for an electrostatic precipitator design will be given based on findings in this study.

Study on the Change Characteristics of Dust Specific Resistivity and Electrostatic Precipitation Efficiency

Specific resistance is an important factor affecting the performance of ESP. For the dust resistance than the impact of electrostatic dust removal mechanism, the relationship between dust specific resistance and electrostatic dust removal efficiency, high dust specific resistance and low dust specific resistance in the electrostatic dust produced by the adverse effects. The method of controlling the specific resistance of dust is proposed, which reduces the specific resistance of high specific resistance dust by adjusting the flue gas humidity, changing the flue gas temperature and flue gas quenching. The surface modification technology is used to improve the low specific resistance dust. By controlling the dust specific resistance to 104 to 1010 Ω · cm, the electrostatic precipitator is kept at a high dust removal efficiency.

축사별 먼지 저항률에 따른 트래킹화재 위험성에 관한 연구

본 논문에서는 동식물시설 중 전기화재 비율이 높은 우사, 계사, 돈사에서 먼지샘플을 채취하여 증류수에 희석시킨 후 이 물의 저항률을 측정하고, 저항률에 따른 물의 온도변화 및 전류 측정실험, 트래킹 재현실험을 통해 축사별로 먼지에 따른 트래킹화재 위험성을 분석하였다. 분석결과 저항률 수치는 우사, 계사, 돈사 순으로 돈사가 가장 낮게 측정되었으며, 축사별 평균 값 역시 우사, 계사, 돈사 순으로 돈사가 가장 낮게 나타났다. 온도변화 및 전류 측정실험에서는 저항률이 낮을수록 물의 온도변화가 큰 경향을 보였으며, 전류 실효값 역시 높게 나타났다. 트래킹 재현실험에서도 저항률이 낮을수록 트래킹 진전속도가 빠르게 진행되었으며 착화시간이 단축되었다. 실험결과를 통해 도출된 결과를 가지고 축사별 먼지 저항률이 다른 이유를 고찰하였다. In animal and plant facilities, dust samples were collected from cattle sheds, pigsties and hen-houses, which have high proportion of electrical fires. The samples were diluted in distilled water and water resistivity was measured. Current measurements and tracking reappearance experiments were conducted using distilled water with dust samples. The analysis results were obtained to track the fire risks according to the dust resistivity. The highest value was the dust from cattle sheds followed in order by the dust of pigsties and hen-houses. In experiments measuring the temperature change and RMS current, the lower resistivity of water showed a significant trend of temperature and high amperage. In the tracking reappearance experiment with the lower resistivity water, the tracking speed was fast and the ignition time was shortened. This study investigated why each dust resistivity shows different results.

Filter penetration and breathing resistance evaluation of respirators and dust masks

ABSTRACTThe primary objective of this study was to compare the filter performance of a representative selection of uncertified dust masks relative to the filter performance of a set of NIOSH-approved N95 filtering face-piece respirators (FFRs). Five different models of commercially available dust masks were selected for this study. Filter penetration of new dust masks was evaluated against a sodium chloride aerosol. Breathing resistance (BR) of new dust masks and FFRs was then measured for 120 min while challenging the dust masks and FFRs with Arizona road dust (ARD) at 25°C and 30% relative humidity. Results demonstrated that a wide range of maximum filter penetration was observed among the dust masks tested in this study (3–75% at the most penetrating particle size (p < 0.001). The breathing resistances of the unused FFRs and dust masks did not vary greatly (8–13 mm H2O) but were significantly different (p < 0.001). After dust loading there was a significant difference between the BR caused by the ARD dust layer on each FFR and dust mask. Microscopic analysis of the external layer of each dust mask and FFR suggests that different collection media in the external layer influences the development of the dust layer and therefore affects the increase in BR differently between the tested models. Two of the dust masks had penetration values < 5% and quality factors (0.26 and 0.33) comparable to those obtained for the two FFRs (0.23 and 0.31). However, the remaining three dust masks, those with penetration > 15%, had quality factors ranging between 0.04–0.15 primarily because their initial BR remained relatively high. These results indicate that some dust masks analysed during this research did not have an expected very low BR to compensate for their high penetration.

The response of reworked aerosols to climate through estimation of inter-particle forces

This paper describes the first use of inter-particle force measurement in reworked aerosols to better understand the mechanics of dust deflation and its consequent ecological ramifications. Dust is likely to carry hydrocarbons and micro-organisms including human pathogens and cultured microbes and thereby is a threat to plants, animals and human. Present-day global aerosol emissions are substantially greater than in 1850; however, the projected influx rates are highly disputable. This uncertainty, in part, has roots in the lack of understanding of deflation mechanisms. A growing body of literature shows that whether carbon emission continues to increase, plant transpiration drops and soil water retention enhances, allowing more greenery to grow and less dust to flux. On the other hand, a small but important body of geochemistry literature shows that increasing emission and global temperature leads to extreme climates, decalcification of surface soils containing soluble carbonate polymorphs and hence a greater chance of deflation. The consistency of loosely packed reworked silt provides background data against which the resistance of dust’s bonding components (carbonates and water) can be compared. The use of macro-scale phenomenological approaches to measure dust consistency is trivial. Instead, consistency can be measured in terms of inter-particle stress state. This paper describes a semi-empirical parametrisation of the inter-particle cohesion forces in terms of the balance of contact-level forces at the instant of particle motion. We put forward the hypothesis that the loss of Ca2+-based pedogenic salts is responsible for much of the dust influx and surficial drying pays a less significant role.

A new understanding of electric conduction in highly resistive dusts and bulk powders

The electric properties and current transport mechanisms in highly resistive dusts and granular materials are investigated both by theory and by experiments.Highly resistive dusts show markedly non-ohmic properties in analogy to semiconductor and electret materials. The resistivity of dust layers shows extremely strong time effects and is strongly dependent on the dust layer thickness, on current density and also on experimental arrangement. The current transport occurs by the injection of excess charges of both polarities. For asymmetric arrangements (e.g., charging by corona), asymmetric injection leads to high excess charge densities and induces strong electrostatic fields. Dust resistivity measured with asymmetric injection arrangement is found to be several orders of magnitude higher than resistivity measured with symmetric injection arrangement. The dependence of dust resistivity on layer thickness and current density can be explained as a result of space charge limited current in analogy to semiconductor and electret theory. Time effects are a result from charge carrier immobilization in combination with space charge limited conduction.Based on electret and semiconductor theory, a simulation model for current transport through dust layers was developed. The model uses an effective medium approach and therefore can be validated with reference simulations for homogeneous materials found in the literature. With an empirical adaptation of the kinetic parameters, the continuum approach seems to be well suited to describe the experimental results obtained with porous dust layers.So far, the experimental validation is limited to idealized situations and does not include effects from adsorption layers. Nevertheless, the results allow a new understanding of effects like back corona in electrostatic precipitators.

Characterization of sintering dust collected in the various fields of the electrostatic precipitator

ABSTRACTSinter plant off-gas is usually de-dusted by electrostatic precipitators. Compliance with the dust emission limits is often difficult because of the high specific resistivity of the emitted dust. Mechanical properties of the dust are also relevant for the electrostatic precipitator design. Dust samples from the four consecutive electrostatic precipitator fields were characterized in this study. Most measured parameters showed a considerable variation in the various dust samples. The particle size of the dust as well as its bulk density continuously decreased from the first field to the fourth field. The flowability of the dusts was generally bad and decreased from the first to the last field. In contrast, the wall friction angles with structural steel were quite constant at approximately 30°. The Fe content was lower in the dust from the last two fields while the concentration of K, Na, Cl− and was significantly higher. At the same time the particle density was lower. The maximum specific dust resistivity for the first field and second field dust was approximately 3 × 1011 Ω cm and no signs for the occurrence of back corona were detected. For the dusts from the last two fields the maximum value was approximately 2 × 1012 Ω cm. Back corona was observed in the temperature range from 120°C to 210°C. In this area the dust resistivity values were higher than 4 × 1011 Ω cm.

Research of Improving the Technique of Electrostatic Collection to High Resistivity Dust by Humidifying and Cooling through Ultrasonic Atomization

In order to study the effect of dust removal in the electrostatic precipitator under the influence of change of temperature and air moisture of flue gas, the ultrasonic atomization and electrical heating has been adopted for simulated gas to change its air moisture and temperature. The specific resistance of fly ash of fluidized bed boiler, the V-j characteristics of the precipitator model and the efficiency of dust removal has been tested in gas working conditions. The measured results of dust specific resistance shows that: when the temperature of gas at range of 100°C to 150°C, the specific resistance of dust was lower when the air moisture is at 23.73% than at 5.21%, especially when the gas temperature is below 120°C, the specific resistance of dust reduce more,and it can reach the orders of magnitude at1010Ω·cm when the moisture of 23.73%; then keep the temperature at 150°C and make the moisture increased, the specific resistance of dust is decreased, however it is still more than 1011Ω·cm when the moisture is increased to 23.73%. The measured results of V-j characteristics of the precipitator model shows that: when the moisture keeps at 23.73% and the temperature is below 120°C, the electric field does not occur the phenomenon of anti-corona. The test result of the efficiency of dust removal indicated that: when we make the moisture increased to 23.73% and the gas temperature below 120°C, the efficiency of dust removal shows a significant increase. The results confirmed that we can improve the purification efficiency of high resistivity dust through flue gas humidification and proper temperature maintain.

Numerical modeling of electrostatic precipitation: Effect of Gas temperature

A Computational Fluid Dynamics model is presented to calculate the particle collection efficiency in electrostatic precipitators in terms of the interactions among gas-particle flow, dust resistivity and electric field. Various material properties and operation parameters are included to extend the model capability for process optimization. The current paper focuses on the effect of gas temperature for a cold-side precipitator. It is found that, as temperature increases in the range 90–120°C considered, the operation voltage drops significantly, due to increased dust resistivity. Behaviors of fine particles in the range from 0.05 to 25μm in diameter are simulated in a circular wire-plate configuration. A minimum efficiency is predicted for particle size around 0.5μm. Below this critical size, the increased collection efficiency results from relatively large surface charge density due to diffusion charging, and reduced inter-phase drag. For moist gas, temperature has significant non-linear effect on the fly ash resistivity. It is demonstrated that a same change in temperature from 120°C to 90°C is more effective than from 150°C to 120°C, as far as the collection efficiency is concerned.