Study on Non-Static Collection Theory for Dust of Electrostatic Precipitator

It is generally accepted that dust resistivity in excess of $${10}^{11}\, \Omega {\rm cm}$$ leads to the formation of back corona and to a deterioration of ESP performance. Besides dust conditioning, the most popular approach for reducing problems with back corona is the application of pulsed corona systems. The idea behind pulsing is very simply to reduce the E-field within the dust layer by reducing the time-averaged current density. However, experience shows that other high resistivity cases are resolved successfully with an opposing approach, using especially smooth HV from three-phase rectifiers in combination with high current densities. A detailed investigation into this discrepancy has revealed that high values of dust resistivity can be traced back to at least two different mechanisms. “Standard” high resistivity dusts show the behaviour which is typical for dielectrics. High potential drop across the dust layer is produced by the injection and immobilization of charge carriers into the material. Resistivity is strongly dependent on time and corona polarity and inversely proportional to the root of current density. The dust layers reach a high level of space charge density. In a sample of an “untypical” high resistivity dust we found that resistivity is independent of layer thickness and of corona polarity and does not show time effects. The dust layer does not accumulate any significant amount of space charge. The potential drop across the dust layer is nearly independent from current density, resulting in a resistivity which is inversely proportional to current density. With very high E-fields, the dust layer shows a progressive increase of current uptake with time, ending in a breakthrough. All these are the typical characteristics of a varistor material. Our results show that different mechanisms of high dust resistivity do exist. Therefore an appropriate choice of the high voltage supply and its control should be based on a thorough analysis of the electrical properties of the dust. A clearly better separation efficiency will be achieved.

This paper deals with investigations of discharge phenomena in porous materials. Experimental investigations with high-resistivity dust have been performed in a laboratory scale electrostatic precipitator. High dust resistivities in combination with a high electric field are responsible for the occurrence of discharges inside the dust layer, so called back corona. The local occurrence strongly depends on dust layer thickness and porosity which is strongly influenced by forces of the electrohydrodynamic field. The corresponding increase of the electric current density was monitored and compared for different geometric parameters and electric operation settings. This paper verifies a correlation between the electric current density, the quality of the porous material and the discharge phenomena. Furthermore a model based on percolation theory describing the initial electrical process in correlation with the porous material is presented.

One of the key issues of the ESP's collection efficiency is the control of collection parameters. Reasonable shaking periods and collection voltages control can effectively improve the collection efficiency. This article start from the non-steady state premise to research on the charge density of dust layer, electric field parameter changes model, and analyze the variation of collection efficiency in the process of dust deposition and variation of electric field intensity. The numerical analysis shows that the collection efficiency decrease amplitude related with initial efficiency and electrical properties of dust. The dust charge density deposited on the plates exponential decays with the time parameter. From the point of collection efficiency, the article proposes new dynamic drive speed of dust particles and collection efficiency formula, and further put forward the optimization of numerical reference of shaking periods and the value of supply voltage.

Electrostatic precipitators (ESP) serve as the primary air pollution control device for the majority of coal-fired utility boilers in the Eastern and Midwestern regions of the United States. Since most of these ESPs are collecting flyash generated from medium- and high-sulfur coal, they are not experiencing operational limitations which are common when treating high-resistivity particles and are performing at an efficiency that is as high as could be expected. However, there are indications that the collection efficiency could be improved with flue gas conditioning. Conditioning is commonly used for solving operational problems associated with high-resistivity dusts. The purpose of conditioning for low- and moderate-resistivity applications is to increase the adhesive characteristics of the dust. Flue gas conditioning that increases particle adhesion has the potential to improve collection efficiency because a large percentage of particulate emissions from a well-performing ESP is due to reentrainment. Improved ESP performance should result if particle reentrainment could be reduced by making the particles more adhesive. This could produce a significant reduction in emissions from and ESP from the Following mechanisms: reduced erosion-type reentrainment; reduced rapping emissions; reduced hopper reentrainment; increased agglomeration of fine particles.

Electrostatic precipitators (ESP) serve as the primary air pollution control device for the majority of coal-fired utility boilers in the Eastern and Midwestern regions of the United States. Since most of these ESPs are collecting flyash generated from medium- and high-sulfur coal, they are not experiencing operational limitations which are common when treating high-resistivity particles and are performing at an efficiency that is as high as could be expected. However, there are indications that the collection efficiency could be improved with flue gas conditioning. Conditioning is commonly used for solving operational problems associated with high-resistivity dusts. The purpose of conditioning for low- and moderate-resistivity applications is to increase the adhesive characteristics of the dust. Flue gas conditioning that increases particle adhesion has the potential to improve collection efficiency because a large percentage of particulate emissions from a well-performing ESP is due to reentrainment. Improved ESP performance should result if particle reentrainment could be reduced by making the particles more adhesive. This could produce a significant reduction in emissions from and ESP from the Following mechanisms: reduced erosion-type reentrainment; reduced rapping emissions; reduced hopper reentrainment; increased agglomeration of fine particles.

High resistivity dust is normally the major problem in electrostatic precipitation. Even though the corona current is only a fraction of a microampere per cm2 the resulting RI drop exceeds the breakdown voltage gradient of the dust layer. This breakdown or sparking through the collected dust causes the familiar back corona and premature sparkover. The Trielectrode Electrostatic Precipitator (TEP) is an effort to make precipitator performance insensitive to dust resistivity. The TEP (U. S. Patent 3,915,672) is based on the concept that the layer of collected dust behaves like capacitance and resistance in parallel so that the corona can occur in short pulses and yet maintain a moderately constant current through the dust layer. In between corona pulses the precipitating field is supplied by a third set of electrodes. Initial bench scale tests using high resistivity particulate indicate that the concept is sound. Recent testing has extended the effective operating range of the TEP for particulate resistivit...

The performance of pulse-jet bag filters is characterised by two contradictory parameters: separation efficiency and pressure drop.Both parameters depend on the filtration time when the dust layer is created.The time between cleaning pulses -the filtration cycle -is also of great importance for the separation efficiency of the filter.This paper describes the results of experimental studies on the wood dust separation efficiency of a pilot scale pulse-jet filter during the initial phase of the process when the number of particles penetrating the filter visibly decreased.

Average iron content in industrial ores decreases from year to year. To use them in the processes of agglomeration and pelletizing, enrichment is necessary, accompanied by abundant emission of dust. A significant amount of iron is lost in tailings at existing magnetic enrichment technologies. Therefore, the development and implementation of new generation cyclone facilities to increase the efficiency of iron ore beneficiation and dust collection during its processing is an urgent scientific, practical and social task. The results of the of new generation cyclone facilities implementation for enrichment of iron ore and dust collection during its processing at the mining and processing factories of Kryvbas (Ukraine) are presented. It has been established that dry magnetic separation of finely crushed ore makes it possible to isolate a magnetic product with an iron content of 64-65%. The yield is up to 45%, the extraction of iron into the magnetic product is 73-75% in two-stage schemes. The degree of dust collection by the new generation cyclone facility is exponentially dependent on the speed of the cleaned flow, number and size of coaxial shells, as well as the diameter of dust particles) and is 1.23 times higher comparing with the previously used cyclone of the same size and capacity. The mobile magnetic field in the recommended cyclone allows to capture magnetic dust with an efficiency of up to 95%, and at the same time the dust is separated into a magnetic component (with an iron content of up to 65%) and a non-magnetic component (up to 12% of Fe) with an initial total iron content of up to 33%.

This paper takes the influence of tax collection and management efficiency on enterprise tax avoidance behavior as the research object, and discusses the influence mechanism of macro policy at the government level on micro enterprise behavior. First of all, this paper uses the three-stage DEA model to measure the tax collection and management efficiency of 28 provinces in China in 2017. Secondly, the multiple regression model is used to empirically analyze the impact of tax collection and management efficiency on corporate tax avoidance activities. It is found that the efficiency of tax collection and management has a significant impact on corporate tax avoidance behavior, and every 1 percentage point increase in tax collection and management efficiency will increase the tendency of corporate tax avoidance by 0.04 percentage points. And local financial pressure will negatively regulate the impact of tax collection and management efficiency on tax avoidance.

In this study, two different dust collectors, one based on an inertial separator and the other based on an electrostatic precipitator (ESP), were developed in order to reduce brake wear particulate matter (PM) emissions. Additionally, the collection efficiencies for brake wear particles (BWPs) of the inertial separator and the ESP were evaluated according to brake pad type. In the case of the inertial separator, the BWP collection efficiencies for the low-metallic (LM) and non-asbestos organic (NAO) pads were similar, and the cut-off size at 50% collection efficiency (D50) was 2.2 µm. The ESP was designed without an additional electrostatic charging device because naturally induced electrostatic charging occurred due to the friction between the brake disc and pad. The BWP collection efficiency of the ESP was higher for NAO pad than for LM pad because the BWPs generated from the NAO pad contained a relatively low iron (Fe) component compared to that of the LM pad, thereby generating more frictional electricity. The maximum ESP collection efficiencies of the BWPs generated from the LM and NAO pads were determined to be 60% and 75%, respectively, and the remaining BWPs that were not collected were presumed to be particles that were not frictionally charged.

The standards of the environmental protection which have critically become tougher in the last decades demand to look for constant ways of improving the systems of technological gases purification in industry. Currently acute problem of thin clearing of large amounts of gases from the dispersed particles. Dedusting is carried out with the help of special devices that can be integrated into the main equipment or placed outside the process. To clean the vented gases used the apparatus of different principle and construction: scrubbers, cyclones, dust-collecting chambers, electrostatic precipitators and others. According to the method of separating dust from the gas following dust control methods: a mechanical method (paleoscience camera, inertial dry dust collection, wet dust removal, filtration) physical method (electrostatic precipitators); physical-chemical method (absorption, adsorption, chemisorption, catalyzing the thermal method). When assessing the efficiency of the dust collectors take note: the overall efficiency of dust removal, or the amount of dust caught in the dust collector, in relation to the amount of dust contained in the in the dust-free gas; fractional efficiency, which determines the completeness of capture of the particles of a certain size; the residual dust content in the gas when leaving the scrubber; the distribution of residue of dust in the gas to particle size or velocity. Under the effective capture know capture efficiency of over 95 %. In the article we deal with the methods of firm particles and dust removal from technological gas during the use of the plant reactivation operation of black sulphuric acid. There is the short characteristic of an electrostatic precipitator. Also we consider the problems standing in a GTS of the industrial enterprises, which lead to decrease in overall performance of the dust and gas purificating equipment. Possible ways of these problems solution are suggested.

Fiber probe is an important component in optical coherence tomography (OCT) and distance measurement system, its collection efficiency of the light reflected from target surface directly affects the signal-to-noise ratio (SNR) of the system, while the target distance will have direct influence on the collection efficiency. However, there are few researches on specific analysis of the collection efficiency variation of fiber probe when target distance change. In this paper, we proposed the theoretical model of fiber probe, and we deduce the collection efficiency of the light reflected from the target surface which is deviated from the ideal image plane of the fixed-focus fiber probe with Δl in the direction of the optical axis. The theoretical result is testified by ZEMAX simulation, and the difference between the simulation result and the theoretical calculation is 0.0023 when Δl = -5mm. In addition, ZEMAX is utilized to simulate the light collection efficiency when target distance change for reflective target surface. The results of simulation are basically consistent with theoretical calculation. It is concluded that the rate of descent for the collection efficiency is greater when target surface is placed in front of the ideal image plane, and the working range of the fiber probe increases with the increase of ideal image distance. The findings can guide us to make effective use of fiber probe and chose a detector with the right dynamic range to improve distance measurement precision.

With the deepening of human exploration of the Earth, more and more survey tasks are being carried out in unstructured environments. Biomimetic robots that can replace humans in completing related tasks under harsh conditions have gradually become a hot topic in robot development. Therefore, developing a biomimetic robot with a wide range of activities, strong mobility, excellent obstacle crossing ability, and rapid avoidance response has important theoretical research significance and broad application prospects. This paper focuses on frogs as the research object,research is conducted from the perspective of institutional design, aiming to design a frog like jumping robot with strong obstacle crossing ability and good environmental adaptability. In terms of overall structural design, a M-shaped structure based on linear bearings was proposed to ensure the stability of the robot during takeoff and landing; In terms of leg structure design, C-shaped flexible springs are used to integrate the calf, ankle joint, and foot into one, which can play a buffering role when the robot lands; In terms of transmission structure design, Propose to control the compression cycle of the jumping leg through a cam to achieve continuous jumping of the robot. The relevant research results indicate that the structural principle of the designed frog like jumping robot is correct, and the jumping effect is relatively good.For the sake of ideals, this paper provides a certain theoretical basis and basis for further research on bionic jumping robots.

Criteria for designing electrostatic precipitators

The Environmental Protection Agency Office of Pollution Prevention and Toxics is currently conducting a study, the Comprehensive Abatement Performance Study, at some Housing and Urban Development demonstration houses, to assess the performance of the abatements after the houses have been reoccupied. The performance of the abatements will be addressed by measuring the levels of lead in dust and soil. The in-line dust collector's efficiency varies significantly between carpet and all other surfaces, including the window sill. However, for all smooth surfaces and the window sill, the in-line dust collector achieves a high average efficiency of 94.5%, regardless of dust particle sizes, thus significantly exceeding the required minimum of 85%. C Overall, the cyclone dust collector's performance slightly exceeds that of the in-line dust collector. Except for small-sized particles on carpet, the efficiency of the cyclone dust collector significantly exceeds the required minimum of 85%.