PRELIMINARY PERFORMANCE TESTS OF A PULSED JET PLEATED PAPER CARTRIDGE FILTER SYSTEM

A pulsed jet pleated paper cartridge filter system was tested for particle removal efficiency and operating stability using agricultural limestone as the test dust. The test system consisted of 6 pleated paper filter units arranged in parallel, each unit having an effective filtration area of 18.1 square meters. The system was operated at constant pressure drops of 6.25, 7.50 and 8.75 kPa (2.5, 3.0 and 3.5 inches of water), with face velocities of 0.78 to 1.04 m/ min (2.5 to 3.4 feet per minute) and dust loadings ranging from 0.5 g/ m to 2.5 g/ m³. Penetration through the media appeared to be relatively independent of dust loading, and efficiencies were in the 99.95 + % range. Slightly lower efficiencies were found for particles having diameters of 0.3 to 1.0 micrometers. A measure of the redeposition of dust pulsed from the filter was required to describe the effects on the pulse rate caused by changes in system flow and pulsing set point. Increased redeposition was found to occur with increasing flow rate, causing an increase in the pulse rate required to maintain operation of the system at a pulsing set point. Overall, the reverse pulse jet pleated paper cartridge filter system displayed extremely high particle removal efficiency in a compact unit that operated with low differential pressure.     

PRELIMINARY PERFORMANCE TESTS OF A PULSED JET PLEATED PAPER CARTRIDGE FILTER SYSTEM

ABSTRACT

A pulsed jet pleated paper cartridge filter system was tested for particle removal efficiency and operating stability using agricultural limestone as the test dust. The test system consisted of 6 pleated paper filter units arranged in parallel, each unit having an effective filtration area of 18.1 square meters. The system was operated at constant pressure drops of 6.25, 7.50 and 8.75 kPa (2.5, 3.0 and 3.5 inches of water), with face velocities of 0.78 to 1.04 m/ min (2.5 to 3.4 feet per minute) and dust loadings ranging from 0.5 g/ m to 2.5 g/ m³. Penetration through the media appeared to be relatively independent of dust loading, and efficiencies were in the 99.95 + % range. Slightly lower efficiencies were found for particles having diameters of 0.3 to 1.0 micrometers. A measure of the redeposition of dust pulsed from the filter was required to describe the effects on the pulse rate caused by changes in system flow and pulsing set point. Increased redeposition was found to occur with increasing flow rate, causing an increase in the pulse rate required to maintain operation of the system at a pulsing set point. Overall, the reverse pulse jet pleated paper cartridge filter system displayed extremely high particle removal efficiency in a compact unit that operated with low differential pressure.     

覆膜滤筒侧壁压力正峰值的测试与分析

为研究脉冲喷吹时滤筒侧壁压力正峰值大小对普通聚酯滤筒的清灰性能的影响,针对材质为聚四氟乙烯的覆膜滤筒,采用自制脉冲喷吹实验台,通过测试滤筒侧壁压力正峰值大小,对直径为147 mm、长度为1 000、1 500 mm的两种滤筒进行测试与分析,并与普通聚酯纤维滤筒的侧壁压力正峰值大小相比较。结果表明:聚四氟乙烯覆膜滤筒各测点的压力正峰值约是普通聚酯纤维滤筒的5～10倍,过滤机理主要为表观过滤,且透气性小的聚四氟乙烯覆膜滤筒清灰效果比普通聚酯纤维滤筒要好;在相同条件下,不同长度的滤筒在滤筒长度方向上,其压力值变化趋势不同。     

FILTER INLET VELOCITY REDISTRIBUTION WITH FILTER LOADING

Previous flow visualizations and laser Doppler anemometer velocity measurements have shown that clean engine air filters are presented with very non-uniform velocity distributions when tested in the SAE universal panel Filter test housing. Experiments were conducted to measure the changes that occur in the velocity distribution in the plane 12.7 mm upstream of the filter as it is loaded with dust. Laser Doppler anemometer measurements of velocity profiles were performed for a production engine air Filter in the SAE universal panel filter test housing. Test conditions corresponded to a clean Filter, and dust-loaded Filters at additional pressure drops corresponding to 50 percent, 100 percent, and 150 percent of the design terminating pressure value. The results show that dust loading does make the velocity profiles less non-uniform, but that the changes are not dramatic. The inlet velocity profiles for the design capacity Filter remain very non-uniform.     

Effects of cleaning mode on the performances of pulse-jet cartridge filter under varying particle sizes

In order to solve the problem of pollution induced by particulate matters, bag filters and pleated cartridge filters have been widely applied to industries. However, the effects of cleaning mode on the performances of filters under varying particle sizes are rarely studied. In this paper, the influence of cleaning mode on the pressure drop and dust emission concentration under varying particle sizes were studied through experiments. The results show that the smaller the particle size is, the faster the pressure drop increases, and the higher the dust emission concentration becomes. In the cleaning process, the smaller the particle size, the greater the residual pressure drop, and the worse the cleaning effect. The cleaning frequency rises with the decrease of particle size under the clean-on-demand (C-D) mode, while the maximum pressure drop grows with the decrease of particle size under the clean-on-time (C-T) mode. For the medium and fine particulate matters, the average dust emission concentration and the average pressure drop under the C-D mode are both slightly larger than those under C-T mode. By comparing the quality indexes under different cleaning modes, it can be found that for medium and fine particulate matters, the use of the C-D mode can ensure more excellent filtration and cleaning performances, while for large particulate matters, the choice between the two modes has very limited influence on the filtration and cleaning performances of pulse-jet cartridge filters.     

FILTER INLET VELOCITY REDISTRIBUTION WITH FILTER LOADING

ABSTRACT

Previous flow visualizations and laser Doppler anemometer velocity measurements have shown that clean engine air filters are presented with very non-uniform velocity distributions when tested in the SAE universal panel Filter test housing. Experiments were conducted to measure the changes that occur in the velocity distribution in the plane 12.7 mm upstream of the filter as it is loaded with dust. Laser Doppler anemometer measurements of velocity profiles were performed for a production engine air Filter in the SAE universal panel filter test housing. Test conditions corresponded to a clean Filter, and dust-loaded Filters at additional pressure drops corresponding to 50 percent, 100 percent, and 150 percent of the design terminating pressure value. The results show that dust loading does make the velocity profiles less non-uniform, but that the changes are not dramatic. The inlet velocity profiles for the design capacity Filter remain very non-uniform.     

PERFORMANCE OF AGRICULTURAL VEHICLE CAB FILTERS MEASURED WITH MONODISPERSE AEROSOLS

The filtration efficiencies of various types and makes of filters used in the cabs of agricultural vehicles have been measured in the laboratory using monodisperse aerosols. Both new and used filters were tested, though in the latter case areas of minimal dust loading were selected as samples for testing in order to obtain results close to those expected from unladen filters. Monodisperse aerosols of urea, in the respirable and near-respirable size range, were used. The results showed that pleated paper and needlefelt filter materials were poor at capturing small particles, though they have the advantage of robustness and low pressure drop. Pleated glass fibre materials performed much better but with the disadvantages of high pressure drops and fragility. The electrostatic filters tested had a low pressure drop and high filtration efficiency, but the form in which they were used was not that which would result in the optimal efficiency, resistance and lifetime.     

Effect of nozzle type on pulse-jet cleaning performance of ceramic filter tube

The dust-cleaning efficiency of the ceramic filter tube is the key factor to determine the long-term stable operation of the dust removal system, and the type of nozzle significantly influences the performance. In this study, four types of nozzles (injection hole, sudden enlargement nozzle, tubular nozzle, and induction nozzle) are used to conduct comparative experimental study on the dust-cleaning effect of the ceramic filter tube. Using the schlieren technique find that the tubular and induction nozzles can improve the deviation angle of pulse-jet airflow. The injection parameters were set as an injection pressure of 200 kPa, an injection distance of 120 mm and a pulse width of 80 ms in the experiment. Using the sidewall pressure measurement system indicates that the integrated pressure of the sudden enlargement nozzle is the largest, but the uniformity is poor. The comprehensive pressure of the sudden enlargement nozzle is increased by 64.86 %, and the non-uniformity is reduced by 28.62 % compared with those of the induction nozzle. Using the visualization filtration cycle test system implies that the degree of damage and stripping state of the dust layer are directly proportional to the sidewall pressure. Moreover, it is found that the residual pressure drop changes exponentially with the dust removal quality under different nozzle types. These conclusions can help explain the mechanism of dust stripping and provide a basis for the selection of nozzles.     

The impact of fouling on the performance of filter–evaporator combinations

This paper presents results of experiments performed on different combinations of five types of filters of varying efficiencies (MERV4, 6, 8, 11, and 14) and four types of evaporator coils with depths and fin geometries under clean and fouled conditions. The fouled conditions were obtained after injection of 600 g (1612 g/m² of coil face area) of dust upstream of the filter–coil combination, which was meant to simulate a year of operation in the field. The air-side pressure drops of the coils and filters and air-side effective heat transfer coefficients of the coils were determined from the measurements under the clean and fouled conditions. Depending upon the filter and coil, the coil pressure drops increased in the range of 6–30% for an air velocity of 2.54 m/s. The impact was significantly greater for tests performed without an upstream filter (the coil pressure drops increased from 43% to 200%). The largest relative effect of fouling on pressure drop occurs for coils with fewer rows, primarily due to higher fin densities. The impact of fouling on air-side effective heat transfer coefficients was found to be relatively small, which ranged from −14% to 4%. In some cases, heat transfer was actually enhanced due to additional turbulence caused by the presence of dust. However, with large dust deposits, heat transfer is degraded because the dust also acts as insulation and creates an uneven air velocity.     

Semi-coke powder filtration experiments using a dual layer granular bed filter

The separation of semi-coke powders from tars and gases during coal pyrolysis is of crucial importance to the coal chemical industry. This work describes an experimental study on semi-coke powder filtration using an experimental dual layer granular bed filter with an inner diameter of 100?mm. With an initial filtration velocity of 0.2?m/s, the dual layer granular bed filter had a filtration efficiency of 99.943% and a pressure drop across the filter of only 1456?Pa. When the initial filtration velocity was increased to 0.25?m/s, the filtration efficiency was 99.937% and the pressure drop was 1834?Pa. Our results indicated that the dual layer granular bed filter we developed and tested showed significant promise as a high-temperature dust collector in low-temperature coal pyrolysis.     

Observation of dust release behavior from ceramic filter elements

The dust-releasing behavior from a ceramic candle filter, which is a key technology of the hot gas cleaning system in advanced coal power generation processes such as pressurized fluidized bed combustion and integrated gasification combined cycle, is discussed based on the observation of the dust-releasing process using a high-speed video camera and the measurement of time change of pressure inside the filter. Time changes of dust-released area and geometrical characteristics and motion of released dust cake fragments were investigated by analyzing photo images from the video camera, compared with the time change and distribution of pressure inside the filter. In order to discuss the influence of porosity of the dust layer, a consolidated dust layer was prepared by clean air filtration at an elevated filtration velocity after the dust filtration. The dust-releasing process was found to be a multi-mode process, i.e. release occurred in a short time after the injection of cleaning air, followed by one or two intermittent releases afterwards. The amount of dust released by the first strike increased with tank pressure. The dust-releasing behavior was sensitive to the cake porosity: the mean size and perimeter of cake fragments increased with porosity and tank pressure for the consolidated dust layer. The initial radial velocity of cake fragment released just after the first strike increased with tank pressure and was almost independent of the filter location.     

直通式脉冲阀性能试验研究

脉冲阀是脉冲袋式除尘器清灰装置的核心部件,其处理能力的大小和喷吹性能的优劣,直接关系到该类除尘设备的运行能耗、设备投资及占地面积.本文开发了一种同步测试系统,用以测定脉冲阀的压力变化特性,并对脉冲阀的喷吹过程做出定性的分析,并拟合出喷吹过程的曲线方程,还提出了以后的研究方向.     

Influence of pulse-jet cleaning pressure on performance of compact dust collector with pleated filter operated in clean-on-time mode

To operate a bag filter continuously, pulse-jet cleaning of dust particles from the filter medium is commonly required, and the pulse-jet pressure significantly affects the filter performance. In this study, the accumulation structure of residual dust particles inside and on the surface of a filter medium at different pulse-jet pressures was investigated by constructing a simple model, and the influence of the dust structure on the filter performance was clarified. Using a simple model, we determined the effective ratio of filtration area β, which represents the ratio of the filterable area to the total filtration area, the true resistance coefficient due to the primary dust layer ζ_p’ thinly deposited on the filter surface, and the true resistance coefficient inside the filter media itself ζ_f’_. The effective ratio of filtration area β decreased with operation time for all pulse-jet pressures; however, it maintained a high value when the pulse-jet pressure was high. The validity of β analyzed by the model was verified using two different methods, and the results showed good agreement, indicating that the model is effective in identifying real conditions. The true resistance coefficient due to the primary dust layer ζ_p’ decreased as the pulse-jet pressure increased; however, the true resistance coefficient inside the filter media itself ζ_f’ was the highest at 0.5 MPa. In addition, the dust collection efficiency was different at each pulse-jet pressure, which was considered to be caused by the difference in the dust particle accumulation structure.     

Influence of air inlet and cleaning chamber on the performance of mining cartridge filter

This study is aimed at shedding light on the influence laws of air inlet position, air inlet area and cleaning chamber. To achieve this aim, first, the influences of air inlet position on pressure drop, air flow rate and mass of coal dust collected on the filter cartridges were investigated with the aid of a homemade experimental system. In addition, the effects of air inlet area on dynamic pressure and air flow rate of the air inlet were evaluated. Furthermore, the velocity within 30 cm in front of the air inlet was tested for determining the effective suction range. Finally, the impacts of cleaning chamber height on pressure drop and air flow rate of the cartridge filter were demonstrated. The research is expected to provide guidance for the setting of the air inlet and the cleaning chamber of the cartridge filter.     

DESIGN AND CALIBRATION OF A STACK SAMPLER FOR OIL FLY ASH

A particle sampling system was developed for the collection of Fly ash the stacks of ail-fired electrical generation plants. The apparatus has a cyclone separator which is designed to provide a cutpoint of approximately 2.5 µ followed by a pulse jet fabric filter. Flow rate is a nominal 226 L/min (8 cfm).

The system was tested in the laboratory with monodisperse aerosols to determine the fractionation characteristics of the cyclone and the inlet probe. Efficiencies of three candidate filters were examined with clean media, with a dust cake and with the dust cake removed. Tests were conducted using monodisperse polystyrene aerosols of 0.50, 0.76 and 1.09 µ

The pulse Jet apparatus was checked by operating the system at a flow rate of 200 L/min, loading the filter with AC fine test dust, and determining the stable filter pressure drop as a function of pulse jet air pressure.     

Use of bluff body for enhancing submicron particle agglomeration in plasma field

A bluff body was installed to generate a vortex shedding in gas flow under nonthermal plasma field. Various shapes of bluff body were analyzed using computational fluid dynamics for their ability to enhance submicron particle agglomeration. The cylindrical bluff body produced the lowest pressure drop and the plate bluff body showed the widest amplitude of vortex shedding. In the experiment, exhaust gas with a velocity of 1–3?m/s were fed into the test section. The electrical pulse peak voltage was 35?kV, 10?kHz. The bluff body improved the reduction efficiency by 27% and 17% for flat plate and cylindrical bluff bodies, respectively, relative to no-bluff body.     

Application of ESP for gas cleaning in cement industry--with reference to India

Electrostatic precipitators (ESP) are used for gas cleaning in almost every section of cement manufacture. Application of ESP is studied, keeping in view Indian conditions. The characterisation of dust emissions has been done for different units, such as rotary kiln and raw mill, alkali by-pass, clinker cooler, cement and coal mill, in terms of exit gas quantity, temperature, dew point, dust content and particle size. It is seen that all these characteristics have a wide range of variance. The ESP system must effectively deal with these variations. The fundamental analytical expression governing the performance of ESP, i.e. the Deutsch equation, and that for particle migration velocity, were analysed to predict the effect of major operating parameters, namely particle size, temperature and applied voltage. Whereas the migration velocity (and the efficiency) varies directly with the particle size, it is proportional to the square and square root of applied voltage and absolute temperature of the gas, respectively. The increase in efficiency due to temperature is not seen in dc based ESP, perhaps due to more pronounced negative effect on the applied voltage due to the increase in dust resistivity at higher temperatures. The effect of gas and dust characteristics on the collection efficiency of ESP, as seen in the industrial practice, is summarised. Some main process and design improvements effectively dealing with the problem of gas and dust characteristics have been discussed. These are gas conditioning, pulse energization, ESP-fabric filter (FF) combination, improved horizontal flow as well as open top ESP.Generally, gas conditioning entails higher operating and maintenance costs. Pulse energization allows the use of hot gas, besides reducing the dust emission and power consumption. The improved horizontal flow ESP has been successfully used in coal dust cleaning. The open top or vertical flow ESP has a limitation on collection efficiency as it provides for only one electric field.     

Observation of the process of dust accumulation on a rigid ceramic filter surface and the mechanism of cleaning dust from the filter surface

The accumulation process of captured particles on the surface of a rigid filter element is experimentally studied by measuring the pressure drop. It is then related to the packing density of the dust layer. The process of the release of dust from filter surface is also studied through the changes in the pressure difference across the filter and the movement of the released dust after clean air is injected. As a result, for a given filtration condition, dust forms the densest layer at the initial and the loosest at the middle stage of the filtration, and forms a uniform layer at the final stage. The cleaning efficiency of the dust layer is found to depend upon the layer structure, i.e, it decreases as dust forms a denser layer, even if the accumulated mass per unit filter surface area is the same. The release velocity of dust from the surface is also found to become slower as the porosity of the layer decreases.     

Characterization of Dust Particles Emitted Through Pulse-Jet Fabric Filters During Industrial Pollution Control

The present investigation elucidates the role of pulse-cleaning parameters and filter media designs on the extent of dust emission and emitted particle characteristics during industrial pollution control using the pulse-jet filtration process. The study is followed by statistical analysis based on L₈ (2⁷) orthogonal design methodology. The experimental study shows that the dust concentration in clean gas increases with an increase in pulse pressure and pulse duration, whereas it decreases with an increase in pulse cycle. However, the contribution of pulse pressure and pulse duration is much higher than the impact of pulse cycle. In regard to the impact of filter media design, a higher level of bag height (which also implies lower air-to-cloth ratio) and lower level of seamline spacing can lead to higher outlet emissions at the transitory stage. The role of pulse pressure, bag height, and seamline spacing are found to be very significant in regulating fine particles in the emission (PM_2.5) and, consequently, the aforesaid factors affect all volume particles diameters (D₁₀, D₅₀, and D₉₇) and weight mean particles diameter D (4, 3) of particles in bulk.     

Development of Venturi negative-pressure secondary dedust device and application of local spray closure technique

In order to enhance the spray for dust suppression performance in a fully-mechanized mining face, based on orthogonal test, comparison test, numerical simulation and field application, the Venturi negative-pressure secondary dedust device was developed. Meanwhile, the local spray closure technique was proposed, which can not only effectively prevent the escape of coal dust from entering the footway space, but also remove coal dust around the respiratory zone from the footway space successfully. The results demonstrated that, under spray pressure of 6?MPa, the Sauter mean droplet size, negative pressure suction flow rate and effective spray distance of the novel dedust device with a throat-to-nozzle distance and throat diameter of 20?mm and 65?mm were 47.37?µm, 11.21?m³/min and 5.4?m respectively. Moreover, the novel dedust device produced droplets to a smaller scale than a single-nozzle. Additionally, the negative pressure and airflow velocity in the negative pressure suction inlet of novel dedust device were within the range from ?0.97?Pa to ?541.04?Pa and from 2.96?m/s to 27.29?m/s respectively. Finally, compared with the original dust suppression measures, the local spray closure technique can enhance the removal ratio of respiratory dust by an average of 44.3%.