WO2010109261A1 - Dust cleaning and collecting device based on electrostatic principles - Google Patents

Dust cleaning and collecting device based on electrostatic principles Download PDF

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Publication number
WO2010109261A1
WO2010109261A1 PCT/IB2009/005801 IB2009005801W WO2010109261A1 WO 2010109261 A1 WO2010109261 A1 WO 2010109261A1 IB 2009005801 W IB2009005801 W IB 2009005801W WO 2010109261 A1 WO2010109261 A1 WO 2010109261A1
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WIPO (PCT)
Prior art keywords
particles
film
airflow
air
dust
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PCT/IB2009/005801
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English (en)
Inventor
Sukhanos Laopeamthong
Kristian Pontoppidan Larsen
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Nito A/S
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Application filed by Nito A/S filed Critical Nito A/S
Publication of WO2010109261A1 publication Critical patent/WO2010109261A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
    • A47L5/00—Structural features of suction cleaners
    • A47L5/12—Structural features of suction cleaners with power-driven air-pumps or air-compressors, e.g. driven by motor vehicle engine vacuum
    • A47L5/14—Structural features of suction cleaners with power-driven air-pumps or air-compressors, e.g. driven by motor vehicle engine vacuum cleaning by blowing-off, also combined with suction cleaning
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47L—DOMESTIC WASHING OR CLEANING; SUCTION CLEANERS IN GENERAL
    • A47L5/00—Structural features of suction cleaners
    • A47L5/12—Structural features of suction cleaners with power-driven air-pumps or air-compressors, e.g. driven by motor vehicle engine vacuum
    • A47L5/22—Structural features of suction cleaners with power-driven air-pumps or air-compressors, e.g. driven by motor vehicle engine vacuum with rotary fans
    • A47L5/24—Hand-supported suction cleaners
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/02—Plant or installations having external electricity supply
    • B03C3/04—Plant or installations having external electricity supply dry type
    • B03C3/12—Plant or installations having external electricity supply dry type characterised by separation of ionising and collecting stations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/32—Transportable units, e.g. for cleaning room air
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/36—Controlling flow of gases or vapour
    • B03C3/368—Controlling flow of gases or vapour by other than static mechanical means, e.g. internal ventilator or recycler
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/40—Electrode constructions
    • B03C3/60—Use of special materials other than liquids
    • B03C3/64—Use of special materials other than liquids synthetic resins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B6/00—Cleaning by electrostatic means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C2201/00—Details of magnetic or electrostatic separation
    • B03C2201/28—Parts being easily removable for cleaning purposes

Definitions

  • Dust cleaning and collecting device based on electrostatic principles
  • the invention relates to arrangements for removing and collecting undesired particles from air and from surfaces with the use of electrostatic principles.
  • Airborne dust particles often contain allergens and microorganism like bacteria, fungi and viruses as well as their toxic products. Inhalation of these biological contaminants may result in lung problems and other illness, like asthmatic and allergies. Even particles that are free from biological contaminants can cause serious health problems. When the particles are smaller than 10 ⁇ m in diameter they will enter the respiratory system. Fine particles, from 0.1 to 3 ⁇ m, get into the lungs, where they deposit.
  • Non-degradable mineral particles such as quartz
  • quartz can get stuck in the lungs and accumulate. Eventually they can cause a chronic state of inflammation, the often deadly disease, silicosis, to which there is no cure.
  • Ultrafine particles below 0.1 ⁇ m, get deep into the alveoli, and through the natural protection system of the lungs. Here the particles can damage the fine lung structure or even enter the bloodstream. These particles are suspected to cause large effect inside the body, where they are considered toxic and possible have an effect on the whole body.
  • the toxicity of particles is considered to directly depend of the size. The smaller the particles are, the more toxic they are.
  • An add on effect is that fine and ultrafine particles will not settle by gravitation, but will stay suspended in air for long time duration (from hours to days).
  • HEPA filter systems can be adapted, where the most efficient ones collects up to 99.97%- 99.995% of the particles larger than 0.3 microns. Though effective, they possess problems due to cost, clogging and constant need of change and/or cleaning.
  • Electrostatic precipitators are another highly efficient system to extract dust particles from air. It works in the way that the particulate laden gases are drawn into one side of the box often using a perforated plate and diffusers to evenly distribute the gas. Inside, high voltage electrodes impart a negative charge to the particles entrained in the gas. These negatively charged particles are then attracted to a collecting metal surface, which is positively charged or grounded. The gas then leaves the box, up to 99.9% cleaner than when it entered. Inside the precipitator, the particles from the continuing flow of dust build up on the collection plates or tubes. At periodic intervals, to keep the efficiency and remove collected particles, the plates are mechanically cleaned by rapping or flushing, causing the particles to fall into the collection hopper, from where it is disposed. The drawbacks with the precipitators are the same as mentioned for HEPA filters together with their high cost.
  • Dust filters and collectors are only able to clean suspended particles in air - not surface dust.
  • the main problems with mechanical systems relate to clogging and expensive replacements or mechanical cleaning, which creates problems with resuspended dust. Also they pose a risk as an ignition source, which can create dust explosions in high dust concentrated areas.
  • ESD Discharge
  • Dust adhesion in general is a problem for many companies, in various industries, like the SME dominated sectors of printing industry, fine mechanical industry, optical lenses, packaging, polymer, glass making and medical device manufactures. Many of these sectors experience a need for higher cleanliness levels among other things because of rapid advancements in various current technologies and the constant trend in miniaturizing of components. This is described normally as precision or critical cleaning. The trend towards higher cleanliness level is reinforced for the SME supply chain, since larger manufacturers are now more inclined to pass cleanliness requirements on parts and assemblies to their SME sub-tier suppliers ( "Precision Cleaning and Verification: A Practical
  • Microfiber cloths - are made from microfibres that become statically charged during use, and thereby attract the dust. It works basically on the same principle as a normal dust cloth; you need to touch the surface you are cleaning, but you can pick up more dust, and clean without the use of water and detergents. Like normal cloth a microfiber cloths must be washed after usage, because it is filled up with dust. So if not used correctly this creates the possibility of decreasing its effectiveness, moving the dust around, and resuspending dust if using it too vigorously. Also manual cleaning does not ensure that all spots are covered. Another problem is that the microfiber cloth will scratch the surface, though the best microfiber cloths today made of even finer fibres have reduced this drastically, it will still be a problem on delicate surfaces. Furthermore, a microfiber cloth is not able to clean (effectively enough) in confined spaces, e.g. notches, cracks, with many small component, etc. Finally, microfiber cloth is not optional when cleaning hazardous dust or continuously cleaning of products in production line.
  • Vacuum cleaning typically work with the use of an air pump that creates a vacuum to suck up the dust and dirt, which is collected by a filter system for later disposal.
  • the most common types for house cleaning may re-suspend dust that will increase dust concentration to more than 50%, mainly because the finer dust particles are not collected by the filtering system and hence re-suspended through the outlet air.
  • Cyclone is another dust collecting system for vacuum cleaning, which helps the problem of clogging.
  • spinning air creates a centrifugal force, which when the dirt and debris are subjected to this it is thrown out of the air and deposited at the bottom of the cyclone.
  • vacuum suction to remove dust in the production industry
  • vacuum cleaners use fibres/brooms (touch surface) to help eliminate the bond between dust and surface, whereas this is often not the case in industrial application.
  • a stronger suction power will be used, which however can be difficult to direct (unless very close to object's surface), and is more energy costly and noisy.
  • Vacuum suction is more often used in the industry to remove particles that are already in the air, since it takes extremely strong suction power to remove very fine dust particles from the surface because of the electrostatic attraction forces. Strong suction power forbids the usage for some application area, where the products are light, small or thin (e.g. paper and some part of the plastic industry).
  • the Electrostatic Discharge (ESD) Control sector produces many types of applications for removing electrostatic attraction from a product.
  • ESD Electrostatic Discharge
  • One often used in the above-mentioned industries is ionizing, which to some extent can eliminate the electrostatic attraction (depending on attraction force, amount of ions provided, surface form, distance to object etc.). But this does not remove the particle from the surface, so a combination with other technologies such as vacuum suction, compressed air blowing, shaking or other is needed. These combinational methods are however not 100% effective, among other things because they create new electrostatic attraction because of friction from moving the dust.
  • Electrostatic Discharge (ESD) control There are a number of devices for Electrostatic Discharge (ESD) control, which are focused on the dust problem elimination either by eliminating the electrostatic charge and hence the dust attraction or combined with dust removal methods, typically with the use of strong airflow (blowing or suction) or by touching the surface. A combination is necessary since anti-static solutions only eliminates the extra adhesion of dust from the electrostatic attraction to a surface, and hence not solve problem of dust already attracted or dust attracted due to gravity force.
  • ESD Electrostatic Discharge
  • US 6,076,216 describes an arrangement for cleaning dust from light-collecting surfaces of solar power generators. The idea is to use an alternating electrical field with very broad frequency range of 10 to 1 ,000 Hz and amplitude between 1 ,000 to 30,000 Volts. Dust is loosened and then has to 'fall off the object being cleaned - with the risk of dust re-suspension. This process will not remove the smaller dust particles below 5 ⁇ m.
  • SU 698494 describes a method of cleaning the surface of laser mirrors, to remove dust particles, by moving above the surface a film, particularly a fluoropolymer film, carrying a static electrical charge.
  • fine dust cannot be cleaned by this manner, and only relatively large particles are removed by attraction to the cleaning film, and the cleaning film must be periodically cleaned of dust.
  • US 5,634,230 describes an apparatus and for removing microscopic particle contaminants from an object such as a photomask, where the particle contaminants are identified by an inspection device. After positioning of a particle contaminant, a polarised probe is dispatched to the position to remove the particle contaminant using an electrostatic method, and hereafter moves to a cleaning compartment where the particle contaminant is removed from the probe. This is a very time consuming process, for very small amount of dust.
  • Ionizers ("Preventing Electrostatic Problems in Semiconductor Manufacturing", A. Steinman, Compliance Engineering, 2004) are ion generators that act by generating positive and/or negative air ions, e.g. with the use of a very high electric field (corona ionization). This increases the conductivity of the air and when the ionized air comes in contact with a charged surface, the surface attracts ions of the opposite polarity, which neutralizes the static electricity.
  • ionizers which combine the ESD element with a dust removing mechanism.
  • One example is ion blowers (or Ionized Air Knife Blowers), where the dust is removed with compressed airflow (e.g. 45m/s at 50mm target distance).
  • Web Cleaners are typically used in the converter industry for paper or film. They can be single or double sided and like for the previous mentioned techniques dust removal is done either by surface touch or with air.
  • the normal principle behind is that a roll is moving across the web (paper, film, foil, etc.) and removes the particles on the web. Different methods are applied, depending on the product needs. Bristles in the form of a brush rotating at a speed of 600 to 800 rpm, have been employed to lightly brush the surface of the web, which has also been combined with vacuum blowers.
  • Another technique is using a roll coated with some kind of tacky surface (polymer), where the dust from the web will stick to the roll, when it moves over the web.
  • Web cleaners with the sole use of airflow are also known, however only for slower moving applications, since breaking through the laminar airflow layer else is problematic. Typical, the used airflow is ionized with positive and negative charges to neutralize surface charges. Problems with web cleaners are that they only work on smooth or fairly smooth surfaces like paper or foil.
  • the way to control dust in these environments are to lower the dust concentration level. This can be done by a combination of things through the use of air filters (HEPA and ULPA) and continuous air circulation, air lock and possible air shower, protective clothing, the construction material of the room, control of operating procedures, frequently cleaning, etc.
  • the cleanliness levels of a cleanroom generally begin at 100,000 particles/ft 3 (>0.5 ⁇ m in size) and extend down to 0.01 particles/ft 3 or less. This can be compared to the 400,000 particles/ft 3 that is the general outdoor atmospheric dust level.
  • the cleanliness level needed depends on the products produced, where low-level cleanrooms are often not sterile (i.e., free of uncontrolled microbes) and more attention is given to airborne dust. But even in the very best cleanrooms you may find particles (e.g. micro fibres from protection garment) that can ruin your products, a problem known from the semiconductor industry. Furthermore, cleanrooms are extremely expensive, so with mass-production of cheap products/components you tend to compromise the need for dust free environments by using some of the earlier mentioned methods.
  • the above mentioned state-of-the-art-technologies mainly focus on removing undesired particles from a surface and often leave the problem to get the particles disposed unsolved.
  • Microfibre cloths are for manual usage, do not ensure covering of all surface, not for hazardous dust usage without protective clothing, can damage delicate surfaces.
  • Vacuum cleaners are generally not efficient enough, re-suspend dust, get damaged by silicate dust, though improved with HEPA filters they clogs and need changing.
  • Air filter dust collecting systems are mainly for cleaning from the outlet, no cleaning/collecting dust from surfaces, expensive, may clog and pose the risk as ignition source for dust explosions.
  • ESD Control from ionizers do not necessarily eliminate the electrostatic attraction 100%, at least not at cost-effective price, must be combined with airflow/suction to collect dust.
  • the problem is their limited usage, only for smooth surfaces. Cleanroom are too expensive for low price unit products, still fine particles like fabric fibres are possible.
  • the main object of the present invention is to achieve an arrangement according to the ingress that makes it possible to remove undesired particles with sizes under 20 ⁇ m from a surface without the need of physical contact with the surface.
  • An other object is to collect the removed particles in a safe way without the risk of re-suspension.
  • One more object is to catch air carried particles under the size of 20 ⁇ m and collect them in a safe way without the risk of re-suspension.
  • Still another object is to develop a disposable unit for safe deposit of dust particles, allowing emptying the collector without the risk of re-suspension.
  • the arrangement according to the invention is primarily intended for the removal and collecting fine, - potentially hazardous - particles below 20um on surfaces and suspended in air.
  • Critical side aspects for this technology were to eliminate the re- suspension of particles during the cleaning process, and safely store and handle the collected particles.
  • the developed technology differs radically from traditional suction and filter solutions.
  • the dust particles are both released from the surface and carried by the same fast airflow.
  • the approach according to the invention is to separate the releasing and the transporting mechanisms. This is achieved by making use of electrostatic effects to release the particles from the surface and use the airflow to a larger extends for the transport.
  • the arrangement according to the invention will have a minimum of re-suspended particles.
  • a circulating airflow, reusing the air will reduce suspended particles and reduce the need for expensive filtering solutions for the exhaust air.
  • the invention has potential applications within a wide range of industries where particles are a problem, technically and health wise. These will include paper manufacturing and processing, printing industries, parts manufacturing, optical parts manufacturing, medical/pharmaceutical industries. Furthermore, there are potential long term applications within traditional office/household cleaning emphasized with the increased focus on indoor air quality and knowledge on fine particle pollution.
  • the main invention intended for dust removal from surfaces compromises the following logical units: an airflow generator comprising a charger that produces ions, an attractor comprising an electrode, a dust collector and preferably at least one neutralizer.
  • An air blower preferably accomplishes the airflow.
  • the technology according to the invention involves charging the dust particles with ions instead of neutralizing them.
  • the electrostatic attraction is overcome thanks to evolving Coulombic force between the charged electrode and the opposite charged dust particles. As a result, the dust particles are lifted from the surface and transported to the dust collector via a controlled airflow.
  • Collector module collecting the released particles from of airflow with low airflow resistance.
  • a cassette system is presented, for providing safe sealing, handling and disposal options of the collected particles at a low cost.
  • Figure 1 is a schematic figure showing some logical parts in the invention.
  • Figure 2 is an illustration showing the velocity profile of a laminar airflow close to a surface.
  • Figure 3 is an illustration showing the forces acting on a charged particle in an E-field and in airflow.
  • Figure 4 is a diagram showing the voltage waveform of an AC ioniser.
  • Figure 5 is a schematic figure showing the essential parts of a handheld arrangement according to the invention, partly in cross-section.
  • Figure 6 is a schematic figure showing the dust collector.
  • FIG. 7 illustrates essential parts of the dust collectors cassette system seen in perspective.
  • Figure 8 illustrates in more detail essential parts of a handheld arrangement according to the invention, partly in cross-section.
  • a surface 2 is contaminated with dust particles 3.
  • dust particles are, according to DMT-Theory, bond to the surface by two dominating adhesion forces i.e. the Van der Waals (VdW) force and capillary forces.
  • VdW Van der Waals
  • Two main electrical forces acting on a particle are the Coulomb force and the dielectrophoretic force. While the Coulomb force is directly linked to the charge of the particle, the dielectrophoretic force acts on uncharged particles due to polarization.
  • the field gradient and the dielectric properties of the particles are determining factors. Particles are attracted to regions of stronger electric field when their permittivity exceeds that of the suspension medium.
  • Alternating current electrical field is usually used for transporting micro particles in a system where the distance between the electrode and particles is in a magnitude of few micrometers. Moreover, high magnitude of electric field strength in the order of MV/cm becomes necessary for attracting particles in submicron level. As a result, the use of an electric field alone to release particles from a surface will be expensive in term of unit and energy costs. Therefore, it must be used in a combination with another force to overcome the adhesion forces between dust particles and a surface in an energy- and cost- efficient way.
  • the invention solves this problem by expose the contaminated surface 2 to an ionized airflow at a certain angle to the surface.
  • an air blower air A is pressed into a plenum chamber 41 of an airflow generator 4, here an air knife.
  • the flow is directed to a precise, slotted orifice, here called slit 42.
  • slit 42 As the primary air jet B exits the thin slit 42, it directs airflow in a perfectly straight line. This creates a uniform sheet of air across the entire length of the air knife. Velocity loss is minimised and force is maximised as the surrounding air is entrained into the primary air stream at a high ratio (up to 40:1). The result is a well-defined sheet of laminar airflow with hard-hitting force and minimal wind shear.
  • a main concern, for the airflow transporting particles is the fact, that the flow speed distribution always approach zero at a non-slip surface according to figure 2. This means that, particles 3 ' released only a few micrometers above the surface, will only experience very slow airflow speeds. This is a main limitation for using low speed laminar flow for carrying the particles. By this reason, low-velocity laminar airflow is not appropriate for transporting dust particles 3 from a surface 2 to the dust collector 7. This is a consequence of the distance between the device and the contaminated surface. Airflow B leaving the air knife 4 has smaller influence on dusts with the increasing height (z) due the lower velocity profile. Blowing angle has also a significant effect on the transportation of dust particles.
  • the arrangement according to figure 1 further comprises a charger 5, the charger preferably comprising ionising pins connected to a high voltage DC generator, not shown in the figure, ionizes the laminar airflow B.
  • a charger 5 preferably comprising ionising pins connected to a high voltage DC generator, not shown in the figure, ionizes the laminar airflow B.
  • corona wires could be used or some other means of ionizing an airflow. So the laminar airflow B is used to not only remove particles from the surface and transport them to the dust collector 7, but also to exert charges onto the adhered particles 3.
  • the housing material of the air knife is preferably polytetrafluoroethylene (PTFE) or Teflon® and the ionising pins are preferably made of special alloy selected from the group consisting of stainless steel, platinum, and carbon.
  • the arrangement according to figure 1 further comprises an attractor 6 comprising an electrode with opposite polarity to that of the particles.
  • the attractor is connected to a high voltage DC generator and so an electrical field is induced. In this electrical field, the charged dust particles 3 are floating above the surface 2.
  • dust particle 3 is charged to a positive polarity.
  • the attractor 6 is connected to the negative pole of a high voltage DC generator, preferred through a capacitively high voltage coupling to eliminate the risk of electrical shocks.
  • the attractor 6 is situated at a certain distance z above the surface 2, here supposed to be horizontal.
  • the released particle 3 experiences a gravity force mg, aerodynamic drag forces F x and an electric force qE y , opposite to mg. When qE y exceeds mg the particle will move towards the attractor 6.
  • the particle As the particle is small, it will have a rather small velocity towards the attractor, relative to the airflow direction.
  • the airflow B from the air knife 4 provides the horizontal force F x to the particle.
  • the particle 3 will be transported towards the dust collector 7 according to figure 1. If the distance to the dust collector 7 is not far the particle 3 will go into the dust collector with the airflow C before it is trapped by the attractor 6.
  • the slit 42 in the air knife 4 preferably should have an opening width between 0.5 - 1 mm.
  • a laminar airflow B with the velocity 30 - 60 m/s so can be achieved.
  • the charger 5, here the ionising pins is given a positive or negative electrical potential 3.5 - 8.0 kV, preferably by connection to a high voltage DC generator.
  • the electrical potential applied to the attractor 6, the particle-attracting electrode must be opposite to polarity to that of the charger 5 and high enough in order to lift up particles from the surface for 0.5 to 1.0 mm.
  • the voltage up to 60 kV is required in accordance with a 2-cm space between the electrode and the surface. This corresponds to a non-linear electric field strength from 3.5 to 10.0 kV/cm depending on the charges of the attaching particles.
  • the electrical potential applied to the attractor is in the span between 10- 6O kV.
  • the arrangement 1 is moved, preferably in the direction E, approximately parallel over the surface, at a distance Z between 1 -2 cm, where the distance is dependent on the system parameters.
  • the relative speed between the arrangement 1 and the surface can be 1 cm/s.
  • the arrangement according to figure 1 further comprises preferably at least one neutralizer 8, preferably comprising alternate current ionising bars, preferably connected to 7.0 kV AC.
  • Positive and negative ions are produced by applying a high voltage AC waveform according to figure 4 to the neutralizer 8. Only one emitter is required to produce ions; both positive and negative ions are produced at each emitter.
  • the main reason to involve a neutralizer 8 is, according to the description above, to avoid adhesion of other particles to the surface been cleaned. But the neutralizer on the left side in figure 1 also helps to neutralising the charged particles, so that they can be effectively charged with the desired ions.
  • the arrangement 1 may further comprises walls 9 in order to control the air flow so that the air B that goes out from the air knife 4 can be the same air C that later goes into the dust collector 7. Preferably the same air is circulated back to the air knife.
  • FIG 5 the system for circulating the air is shown schematically.
  • An electrical air blower 10 is pressing the air via the tube 12 into the plenum 41 in the air knife 4.
  • a laminar airflow B is directed towards the surface (not shown in this figure) to be cleaned.
  • the airflow B is ionized by the charger 5.
  • Dust particles on the surface are by this arrangement charged and can be attracted by the attractor 6 as described before.
  • the dust particles are floating above the surface and transported to the inlet 701 of the dust collector 7.
  • the dust collector comprises a channel 702.
  • the channel is closed by sidewalls 13 so that the airflow is guided in the direction F. In this channel, 702 the most part of the dust particles are trapped.
  • the outlet 703 of the channel 702 is preferably connected to a HEPA filter 704 where the remaining dust particles will be trapped. After the HEPA filter the airflow is guided back to the air blower through the tube 11.
  • the dust collector 7 comprises a flat airflow channel 702, having a symmetric set of plate electrodes 705 at the right and left sides in the figure.
  • a number of corona wires 706, preferably thin metal wires, transverses the airflow perpendicular, which airflow is directed according to the arrow F.
  • the right and left electrodes are covered by a movable film 707, which is supplied from the film container 709, here upper rolls and spooled up on the lower rolls 710.
  • the electrodes 705 are partly surrounding the rolls 709 and 710 in order to keep the film charged at a longer distance.
  • the electrodes sealing walls 708, made of non-conducting materiel can be arranged.
  • the rolls are preferably rotated by the means of an electrical motor around axes 709 ' and 710 ' , respectively.
  • the films 707, being charged by the electrodes 705 can be made of a conducting or non-conducting thin material such as polyester, Mylar, polyethylene etc. or other materials.
  • the film is supplied from an other type of film container 709 then a roll, e.g. the film could be stored folded.
  • the essential aspect is that the film is spooled up on roll as the particles 3 by this means will be trapped between the film layer spooled up on the roll (710) and hence be sealed in a safe way.
  • air is sent from the inlet 701 through the channel 702, and airborne particles 3 of the airflow will be collected on the charged films 707 in front of the electrodes.
  • the collector functions basically as an electrostatic precipitator. Applying a high voltage between the electrodes 705 and the corona wires 706, generates a very strong electric field around the wires 706, eventually creating free flowing ions or electrons in the surrounding air. Thus the air is ionised, a flow of current is passing towards the collector electrodes.
  • corona wires other known means of ionizing air could be employed. Particles 3 in the air will hit those emitted electrons or ions and accordingly be charged.
  • the particles 3 of the airflow will be attracted to the collecting electrodes 705 of opposite polarity.
  • the electrodes 705 preferably have the same polarity as that of the attractor 6.
  • those particles 3 that have kept their charge from the charger 5 will be attracted to the films 707 charged by the collecting electrodes 705, without the need of be recharged by the ion current from the corona wires.
  • an electrical conducting film 707 the film could be charged by contact to electrodes in the form of edges or rolls with a small contact area. In this case the films do not need to be supported by a large contact area and can be stretched between the upper and lower rolls 709 and 710.
  • An advantage with such an arrangement is that it is easy to build up a strong e-field between the corona wires and the films. Also the friction between the films and the electrodes will be lower.
  • a disadvantage is that electrical conducting films are much more expensive than non- conducting film.
  • the collected particles 3 are encapsulated and sealed.
  • the film is moved in the direction G, opposite to the direction F of the airflow.
  • the lower roll of film with collected matter is counter rotated, in the direction I, so that the film surface that is carrying the particles 3 is turned towards the rotation axes 710 ' , according to the figure 6.
  • the speed of which the film 707 is moved depends of the amount of particles 3 collected.
  • the film can either be moved continuously or stepwise. Typical speeds are within 1mm to 5cm per minute.
  • the film can be made of non-conducting or conducting material, e.g. polyester with a thickness of (7-15um).
  • the electrodes 705 forming the airflow channel are slightly narrowing giving a trapezoid cross section.
  • the typical distance between the electrodes is 2.0-0.3 cm, and the length about 30 cm. In this way, larger particles, which are easier to collect, will be trapped earlier than smaller particles.
  • the typical applied voltage between the corona wires 706 and the collector electrodes 705 is 3-15kV. Both positive and negative polarity can be used, but it is preferred that the electrodes have the same polarity as that of the attractor 6.
  • the two collector electrodes 705 are however at the same potential, i.e. both positive or both negative.
  • several methods can be applied, such as roughening the electrode surface, employing rollers at the curved parts of the electrodes or using a powder between the film and the electrode. It can also be possible to reduce the friction by pressing air through a set of small holes in the electrodes 705 and so achieve air lubrication.
  • the film is moved in the opposite direction of the airflow.
  • Surface treatment of the metal electrode surface can be made to avoid the film to clamp to the electrode.
  • Use of conductive polymer materials for the film is an option, if the highest efficiency of the precipitator is needed. It also is thinkable that the electrodes 705 are made by conductive polymer material.
  • the collector 7 comprises a cassette system according to figure 7 in order to achieve the following functionality requirements: safe sealing of the particles, disposable, interchangeable, easy operation, sufficient long operation time, end-of film and movement detection and also low operation costs.
  • a cassette system according to figure 7 is preferably arranged as a set comprising two carrier, one carrier 712 with the unused films and the other 711 with the used film containing the collected particles.
  • the cassette is not yet inserted into the collector 7.
  • the principal is to have two unused films 707 initially spooled on rolls 709.
  • the rolls 709 are turnably journalled in the carrier 712 via axis 709 ' .
  • the carrier 711 comprises rolls 710 turnably journalled in the carrier 711 via axis 710 ' .
  • the carriers preferably are inserted in a pair and after use, both are replaced.
  • a DC motor preferably drives the rolls 710. Both rolls 710 preferably run with the same speed, ensured by linking gear.
  • the collector 7 may comprises means to stretch the films 707 between the carriers 712 and 711.
  • the films 707 with collected particles on one surface will in this way be spooled into the rolls 710, which provides an efficient sealing of the particles as long as the roll is firm and the outer shelf defined by the carrier 711 prevents external mechanical impact.
  • disposal cassette carriers for the film By using disposal cassette carriers for the film, safe particle collection and handling of hazardous particles is possible.
  • the film is completely spooled into carrier 711. This ensures safe encapsulation of the collected particles.
  • the thin plastic film 707 is made of polyethylene or polyester. Length of film is typical 30m.
  • the carriers 711 and 712 can be made of extruded or injection-moulded High density PE, PVC or ABS., similar to existing disposable print toner.
  • carrier 712 comprises an optical film movement sensor, using encoded lines on a gear. It is also preferred that carrier 712 comprises an optical film end-point sensor, sensing encoded lines in the film, when this film has reached a certain end-point ( ⁇ 0.5 m before end of film). After this point, the film will get spooled off, which encapsulates the film safely.
  • the capturing of particles may be enhanced by using a sticky surface on the film.
  • the direction of the movement of the film can be parallel or orthogonal to the airflow.
  • a movable film to the collector electrodes of an electrostatic precipitator. Instead of the current setup with two separate film strips, it can be made using only one film strip going all the way around.
  • the design of the collector electrodes can be made in many different ways. It can be a parallel (uni-distance) or v-shaped (narrowing down) or other varying distance configurations.
  • Using an orthogonal film movement relative to the airflow will provide a method to perform particle separation.
  • an automatic cleaning system for the film is imaginable where the film is cleaned using Mylar blade, like the drum cleaning system in a photocopier.
  • the collector idea is to have a method for collecting particles from an airflow on a movable film by use of electrostatic effects. It is a method to provide automatic cleaning of the electrodes in a electrostatic precipitator. With this method the collected particles are sealed in a safe way in the film roll.
  • This part of the invention has above been described in combination with an arrangement to remove undesired particles from a surface.
  • the collector idea can however also be used alone in order to clean air from air carried particles under the size of 20 ⁇ m and collect them in a safe way without a low risk of resuspension, for instance cleaning the indoor air from dangerous particles.
  • the system preferably is up scaled with wide rolls of film in order to increase the surface area and lower the air speed.
  • Electrostatic precipitators according to the present state of the art (without the film) are employed for such tasks.
  • the efficiency to trap ultrafine particles may not be better than existing systems. Nevertheless, the handling of the collected hazardous particles will be much safer, and there will be an automatic way of keeping the collection surface fresh.
  • FIG 8 a preferred embodiment of a handheld system 80 is presented in more details.
  • the system comprises a cover 81 , shown in the figure as outer contours.
  • the system further comprises a handle 82, an on/off switch 83, a battery 87, a control unit 86, a high voltage generator 85 and a film motor 84.
  • the inlet air A to the airflow generator 4 is pressed by an electrical air blower 10 via the tube 12.
  • the outlet air B from the airflow generator is ionized by a charger 5 placed in the vicinity to the out let of the airflow generator.
  • the air flow B is directed towards the surface (not shown in this figure) to be cleaned.
  • Dust particles on the surface are hence charged and attracted by the attractor 6 for further transport to the inlet 701 of the dust collector 7.
  • the dust collector the dust particles will be disposed according to the function described above.
  • the outlet of the collector 7 is connected to a HEPA filter 704 where the remaining dust particles will be trapped. After the HEPA filter the airflow is guided back to the air blower through the tube 11.
  • the upper carrier 712 comprises a film movement sensor 713 and a film endpoint sensor 714, both preferably optical.
  • the system 80 also comprises a neutralizer 8, although such is not shown in the figure.
  • the system 80 is controlled by the electronic control unit 86, which can be made based on microcontrollers.
  • the control unit 86 controls the film movement motor 84, the air blower 10 and the high voltage generator 85 for the corona wires 706, the air charger 5, the attractor 6 and the electrodes 705.
  • the control unit receives input from the on/off switch 83, the film movement sensor 713 and the film endpoint sensor 714.
  • a charger 5, an attractor 6, a collector 7 and preferably a neutralizer 8 also a stationary cleaning device for industrial application can be achieved. For instance, it is possible to separate the cleaning process into four zones: charging, floating and transporting, collecting and neutralizing.
  • a stationary unit could be used in areas like paper industry, parts cleaning (car parts/optical parts), printing industry, cleaning of foils, food industry, cleaning in hazardous environments (nuclear, nanoparticle, quartz dust).
  • An obvious application is for web-cleaning where the method according to the invention differs from the state of the art by charging the particles and using the charge to float the particles in a controlled way above the surface and transport them to the collector.

Landscapes

  • Electrostatic Separation (AREA)

Abstract

L'invention porte sur un appareil (1) éliminant les particules (3) non désirées de surfaces (2) comprenant: un générateur (4) produisant un flux d'air (B) entraînant les particules (3) par effet de traînée aérodynamique; un chargeur (5) ionisant le flux d'air (B) lequel charge à son tour les particules (3) avec la même polarité; et un attracteur (6), muni d'une électrode de polarité opposée à celle des ions du flux d'air (B) produits par le générateur (4) et le chargeur (5), et produisant une force électrostatique d'attraction qui détache de la surface (2) les particules (3), qui flottant au-dessus de la surface (2), sont transportées par effet de traînée aérodynamique essentiellement parallèlement à la surface (2) par le flux d'air (B).
PCT/IB2009/005801 2009-03-27 2009-05-30 Dust cleaning and collecting device based on electrostatic principles WO2010109261A1 (fr)

Applications Claiming Priority (2)

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SE0900405-2 2009-03-27
SE0900405 2009-03-27

Publications (1)

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WO2010109261A1 true WO2010109261A1 (fr) 2010-09-30

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012104089A1 (fr) * 2011-02-04 2012-08-09 MAX-PLANCK-Gesellschaft zur Förderung der Wissenschaften e.V. Appareil de nettoyage des sols équipé d'un applicateur de plasma
EP2543419A1 (fr) 2011-07-04 2013-01-09 Gölz GmbH Filtre-presse
WO2016118613A1 (fr) * 2015-01-20 2016-07-28 Ikonics Corporation Appareil et procédé pour éliminer des particules abrasives à partir de l'intérieur d'un panneau
CN107175689A (zh) * 2016-03-09 2017-09-19 海德堡印刷机械股份公司 具有驱动器、工具头和用于引导柔性管线的多轴机器人
DE102016108477A1 (de) * 2016-05-09 2017-11-09 Vorwerk & Co. Interholding Gmbh Vorrichtung zum trockenen Reinigen von Oberflächen in Form eines Handstaubsaugers oder einer als Aufsatzteil ausgebildeten Saugdüse
US10551611B2 (en) 2018-04-18 2020-02-04 Microsoft Technology Licensing, Llc Techniques for removing particulate from an optical surface
WO2021147656A1 (fr) * 2020-01-20 2021-07-29 哈尔滨工业大学 Dispositif pour réaliser un nettoyage de surface d'un élément optique par un vent d'ions et un couplage électrostatique
WO2021224933A1 (fr) * 2020-05-06 2021-11-11 Sugirthamuthu Shobhana Visière électronique et équipement de protection individuelle (epi) chargé électriquement
CN114101221A (zh) * 2021-11-11 2022-03-01 北京理工大学 一种基于驻极体的表面积尘清除系统及其除尘方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4976749A (en) * 1989-04-24 1990-12-11 Raytheon Company Air filter and particle removal system
US6932857B1 (en) * 2001-09-10 2005-08-23 Henry Krigmont Multi-stage collector and method of operation
US20060187609A1 (en) * 2002-08-21 2006-08-24 Dunn John P Grid Electrostatic Precipitator/Filter for Diesel Engine Exhaust Removal

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4976749A (en) * 1989-04-24 1990-12-11 Raytheon Company Air filter and particle removal system
US6932857B1 (en) * 2001-09-10 2005-08-23 Henry Krigmont Multi-stage collector and method of operation
US20060187609A1 (en) * 2002-08-21 2006-08-24 Dunn John P Grid Electrostatic Precipitator/Filter for Diesel Engine Exhaust Removal

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012104089A1 (fr) * 2011-02-04 2012-08-09 MAX-PLANCK-Gesellschaft zur Förderung der Wissenschaften e.V. Appareil de nettoyage des sols équipé d'un applicateur de plasma
EP2543419A1 (fr) 2011-07-04 2013-01-09 Gölz GmbH Filtre-presse
WO2016118613A1 (fr) * 2015-01-20 2016-07-28 Ikonics Corporation Appareil et procédé pour éliminer des particules abrasives à partir de l'intérieur d'un panneau
CN107175689A (zh) * 2016-03-09 2017-09-19 海德堡印刷机械股份公司 具有驱动器、工具头和用于引导柔性管线的多轴机器人
CN107175689B (zh) * 2016-03-09 2021-07-16 海德堡印刷机械股份公司 具有驱动器、工具头和用于引导柔性管线的多轴机器人
DE102016108477A1 (de) * 2016-05-09 2017-11-09 Vorwerk & Co. Interholding Gmbh Vorrichtung zum trockenen Reinigen von Oberflächen in Form eines Handstaubsaugers oder einer als Aufsatzteil ausgebildeten Saugdüse
US10551611B2 (en) 2018-04-18 2020-02-04 Microsoft Technology Licensing, Llc Techniques for removing particulate from an optical surface
WO2021147656A1 (fr) * 2020-01-20 2021-07-29 哈尔滨工业大学 Dispositif pour réaliser un nettoyage de surface d'un élément optique par un vent d'ions et un couplage électrostatique
WO2021224933A1 (fr) * 2020-05-06 2021-11-11 Sugirthamuthu Shobhana Visière électronique et équipement de protection individuelle (epi) chargé électriquement
CN114101221A (zh) * 2021-11-11 2022-03-01 北京理工大学 一种基于驻极体的表面积尘清除系统及其除尘方法

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