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.     

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.     

Investigation to rectangular flat pleated filter for collecting corn straw particles during pulse cleaning

This work investigated the amounts of dust residual of a rectangular flat pleated filter for collecting corn straw particles during pulse cleaning and attempted to explore the causes of incomplete cleaning. In this study, dust residual, filter’s pressure drops and static peak pressures were obtained across flat pleated filter during the pulse cleaning. The optimum parameters were obtained that the pulse electromagnetic valve size was one inch, the pulse pressure was 0.2–0.3?MPa, and the filtration velocity was 0.6?m/min for the nozzle type with 7 holes with a diameter of 7?mm (7?×?Ф7?mm). Under this condition, the experimental results show that the dust residuals were 198.4 (64%), 52.7 (17%), 58.9 (19%)?g for initial collected dust residual 310?g at top, middle and bottom areas of the filter panel, respectively. The dust residuals were major on the top area of the filter panel, especially on the gap locations between the two-adjacent pulse airflows. Meanwhile, the more pulse interval or dust concentration was increased the dust residuals of the filter panel and the pressure drops of the filter were increased. Moreover, the static peak pressure distribution can give guidance to the dust residual distribution.     

Effect of filtration velocity and dust concentration on cake formation and filter operation in a pilot scale jet pulsed bag filter

Bag filters are used for the removal of fine solid particles from process gases. Thus, understanding the filter cake build up and its properties is a subject of interest. The filter cakes properties may depend on many factors like, for example, filtration velocity and dust concentration. The effect of dust concentration and filtration velocity on filtration time, specific cake resistance and mean cake density is investigated in a pilot scale jet pulsed bag filter. An in situ optical system is used to measure cake thickness distributions on the filter surface. Additionally, the operation is simulated using a one-dimensional model and results are compared with experiments. The experimental results indicate that cake density and specific resistance increase with increasing velocity at constant dust concentration. The effect of dust concentration on filter cake density and specific resistance is small.     

BENEFITS OF SERIAL LAYER MICROFILTRATION

Many filtration applications are of necessity being driven toward finer and finer particulate removal and improved permeate quality. Finer particle removal requires filters with smaller pore sizes and absolute pore size guarantees, and the finer the pores in the membrane filter, the sooner it will clog slowing its throughput rate and reducing its useful life. Engineers will frequently design processes involving several separate filtration and clarification steps to allow the process to run larger batches or for extended periods of operation without, system shutdown for filter changes. Membrane manufacturers who produce the final filters used at the end of the filtration train have resorted to a familiar technique in many liquid filtration and purification applications to achieve the desired final fluid quality level at reasonable filtration rates and final filter life by designing and producing filter elements with two membrane layers.

It is the objective of this paper to illustrate simple techniques used by a microporous nylon membrane manufacturer to select and optimize the prefilter membranes to be used in a dual-layered membrane pleated cartridge filter element. The membranes are thin polymeric sheets of nylon supported internally with a nonwoven polyester cloth that is coated with the nylon polymer in such a way that fluid passing through the filter contacts only the nylon and does not contact the polyester.     

Measurement of total energy flux density at a substrate during TiOx thin film deposition by using a plasma jet system

The total energy flux density delivered to an electrically isolated substrate in a low-pressure pulsed DC hollow cathode plasma jet sputtering system during TiO₂ thin film deposition has been quantified. The plasma source was operated in constant average current mode and in a mixture of argon and oxygen or only in pure argon working gas. A titanium nozzle served as the hollow cathode. The total energy flux density measurements were made using a planar calorimeter probe. The main results from the calorimeter probe showed clearly that the total energy flux density at the electrically isolated substrate decreases significantly with duty cycle from 100% (DC mode) to 10% at a given pulsing frequency 2.5 kHz. A local maximum at duty cycle 60% for only pure argon operation has been observed. In addition, the voltage waveforms on the hollow cathode and before the ballast resistor have been saved for pulsed DC measurements for both pure argon and argon + oxygen mixture. A similar transient phenomenon on the cathode voltage and discharge current as observed recently in mid-frequency pulsed DC magnetron discharge has been discovered in the hollow cathode plasma jet sputtering system. We can conclude from these preliminary measurements that the main asset of the pulsed DC hollow cathode plasma jet discharge as distinct from the DC driving of the same plasma system lies in the possibility to reduce or to increase energy influx on the floating substrate within the change of duty cycle.     

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.     

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。     

气液深度分离过滤元件的研制

针对天然气气液深度分离工况条件，对预过滤器和聚结器的滤芯进行了设计与研制。详细论述了气液深度分离元件过滤机理，由工况条件确定了滤芯过滤面积、精度、材质等参数。滤芯采用纸玻璃纤维制成折叠式筒状滤芯，其分离（过滤）面积是未折叠筒状滤芯的4-6倍，是一种过滤精度高透过性能好的高效分离元件。滤芯应用试验表明，该滤芯强度优于国外进口滤芯，使用寿命大大延长，天然气的气质达到国家二类气质标准。     

液氮净化系统仿真设计与性能测试实验研究

针对低温液体净化特点,设计褶皱型316L不锈钢烧结丝网过滤器。建立液氮净化系统动力学模型,仿真结果与实验结果对比表明过滤单元水平布置情况下的颗粒沉积并不影响过滤性能,优于垂直布置。基于过滤单元的水平布置搭建过滤实验台,将液氮与二氧化碳气体混合形成滤浆,测定恒速与恒压工况下的过滤性能并研究滤浆流量、干冰体积含量的影响。结果表明过滤效率均能达到99.99%以上,且滤饼的形成与堆积是影响过滤性能的最关键因素。     

脉冲布袋除尘器在钢铁冶炼中的应用

脉冲布袋式除尘器是一种清灰效果好、净化效率高、处理气量大、滤袋寿命长、维修工作量小、运行安全可靠、自动化程度高的高效除尘净化设备。1957年美国粉碎机械公司制造出的脉冲布袋式除尘器被认为是除尘器的一项重大发明。南钢中厚板卷厂高度重视环保设施,使用的就是目前国际上最普遍、最高效的脉冲布袋式除尘器。本文着重介绍这套设备系统组成、工作原理、工艺流程及特点。     

ROOM-TYPE AIR CLEANER DESIGN CRITERIA AND PROTOTYPE PERFORMANCE

Two rules-of-thumb for minimum performance of a room-type air cleaner have been developed from consideration of a first order model for room air quality. By adopting a criterion that the use of an air cleaner should cause the particle concentration to be at least cut in half, the rule-of-thumb for a room with no smokers is that the product of filter efficiency and flow rate should be ≥.8 m³/min (≥30 cfm). If the particle concentration is dominated by smokers or other sources, the product of filter efficiency and filter flow rate should be = m³ /min (= 100 cfm)

Tests were conducted to determine the efficiencies of candidate filter media. The selected media, Filtrete G-0115, has a fractional efficiency for 1 μm particles of 97 percent when clean, and an efficiency of 78 percent when fully loaded. This drop in efficiency is due to the masking of the electrets on the surfaces of the filter fibers.

A fibrous filter room-type air cleaner was designed to perform in accordance with the rules-of-thumb. When operated with a clean filter, the maximum flow rate is 3.2 m³/min and, when operated with a fully loaded filter, the maximum flow rate is 1.8 m³/min. The system has a multispeed fan which will provide lower flow rates.     

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.     

ROOM-TYPE AIR CLEANER DESIGN CRITERIA AND PROTOTYPE PERFORMANCE

ABSTRACT

Two rules-of-thumb for minimum performance of a room-type air cleaner have been developed from consideration of a first order model for room air quality. By adopting a criterion that the use of an air cleaner should cause the particle concentration to be at least cut in half, the rule-of-thumb for a room with no smokers is that the product of filter efficiency and flow rate should be ≥.8 m³/min (≥30 cfm). If the particle concentration is dominated by smokers or other sources, the product of filter efficiency and filter flow rate should be = m³ /min (= 100 cfm)

Tests were conducted to determine the efficiencies of candidate filter media. The selected media, Filtrete G-0115, has a fractional efficiency for 1 μm particles of 97 percent when clean, and an efficiency of 78 percent when fully loaded. This drop in efficiency is due to the masking of the electrets on the surfaces of the filter fibers.

A fibrous filter room-type air cleaner was designed to perform in accordance with the rules-of-thumb. When operated with a clean filter, the maximum flow rate is 3.2 m³/min and, when operated with a fully loaded filter, the maximum flow rate is 1.8 m³/min. The system has a multispeed fan which will provide lower flow rates.     

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.     

Stopped-flow technique for transit time measurement in a gas jet

A “stopped-flow” technique for the measurement of transit time of reaction products in a gas jet is described. The method involved establishing the gas flow through the jet system when the reactor is operating steadily and allowing the pressure to reach equilibrium values. The gas flow is stopped by means of electrically operated valves. The transit-time measurement is achieved by opening the valves and initiating the multiscaling of total activity simultaneously. The value obtained agrees well with the transit time measured by pulsing the reactor. The “stopped-flow” technique allows on-line measurement of transit time in any gas jet system where the physical transportation time is the major component of the transit time. This technique is especially useful for systems installed in reactors which do not have pulsing capability.     

Polarized polymer films as electronic pulse detectors of cosmic dust particles

A dust particle detector based on a new physical principle of detection is described. The basic detecting element requires no bias voltage and consists of a thin film of the polarized polymer polyvinylidene fluoride (PVDF) having conducting electrodes on each of its surfaces. A high velocity (～10 km/s range) dust particle entering the detector removes dipoles along its trajectory. This produces a local depolarization, which results in a fast (ns range) charge pulse signal in the external circuit which is detected using pulse electronics. A theory has been developed for this new mechanism of pulse detection. The dependence of signal amplitude on particle mass and velocity has been measured for several PVDF detectors having thickness in the range 2–28 μm and area in the range 4–150 cm² using iron particles with velocity in the range ～1–12 km/s and mass in the range ～ 10^?13–10^?10 g. In addition, measurements carried out using a two-detector arrangement show that time of flight information may be obtained. Experimental results are presented which show, for example, that PVDF detectors have mass detection thresholds in the range ～10^?14–10^?12 g, at an impact velocity of 10 km/s, which compare favorably with mass thresholds reported for current dust detectors based on other physical principles. PVDF detectors have the advantages of being inexpensively and easily fabricated, tough, flexible and radiation resistant (to at least 10⁷ rad). They exhibit long term stability, and may be operated for extended periods of time over the temperature range ?50°C to + 50°C. In addition, their fast response permits a detector-pulse electronics system to count dust impacts at event rates up to 10⁴ s^?1 with no corrections required, and they have a response to dust particle impacts which is unaffected by high background fluxes of charged particles. As an example of the application of PVDF dust detectors, a detector is described which is being carried on space probes to measure the mass and flux of dust particles from Halley's Comet in March 1986. Other important applications for experiments in space are discussed.     

Performance evaluation of two-stage electrostatic air filter with low-ozone emission corona charger

The ozone emitted from indoor air cleaners with corona chargers is harmful to the human respiratory system. In this study, a functional treatment of the discharge electrode surface was attempted to reduce the level of ozone generation from the corona discharge. The ozone emission level and charger performance were evaluated by measuring the particle removal efficiency and the pressure drop characteristics with the dust loading on the filter. Ozone production from the low-ozone discharge electrode was reduced by approximately 60% compared to conventional discharge electrode, but the corona initiating voltage and discharge current were equivalent to those of the conventional electrode. The particle removal efficiency of a low-grade filter assisted by the corona charger increased to a high-grade filter without a charger. The replacement time for the low-grade filter with the charger was approximately three times longer than that of a high-grade filter.     

Final precession angles for pulsed ferrite samples

A theoretical study has been made of the transient motion of the magnetization vector in isotropic ferrite spheres during the application of pulsed magnetic fields at an angle to the dc saturating field. Results are presented which permit the determination of the final precession angle for 1) arbitrary pulse-rise rates and pulsing angles when the pulse is linear, and 2) arbitrary pulsing angles when the pulse is slowly rising and nonlinear.     

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.