"Apparatus for Particle Removal From Small-Scale Exhausts"
Field of the Invention
The present invention relates to an apparatus and method for particle removal from small-scale exhausts.
Background Art
The following discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge of any jurisdiction as at the priority date of the application.
Extraction of pollutant particles from smoke has desirable health and environmental benefits. For these reasons, large-scale industrial complexes have implemented into their exhaust stacks devices such as electrostatic precipitators.
An electrostatic precipitator, as implemented in an industrial exhaust stack, comprises an emitter and collector electrode located within a large chamber through which the exhaust gases are forced by way of a fan system. It is therefore an object of the present invention to provide an apparatus for particle removal from small-scale exhausts that does not require a large structure and eliminates the need for forced air.
Typically these large industrial precipitators are not effective on particulates which are resinous. In instances where these resinous particulates are present, a wet type precipitator is used. This wet precipitator technique is not practical in respect of small- scale exhausts.
It has also been noted that cleaning of the electrodes of an electrostatic precipitator implemented in an industrial exhaust stack involves rapping the collector on a regular basis. However, this cleaning technique is not practical in respect of small-scale exhausts.
It is therefore an optional object of the present invention to provide an apparatus for particle removal from small-scale exhausts that can be easily installed and cleaned as necessary.
Throughout the specification, unless the context requires otherwise:
• the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers; and
• the phrase "small scale exhausts" includes, but is not limited to, flues, chimneys or other exhausts where the function of the flue, chimney or other exhaust is to channel the smoke stream created by the burning of such fuels as wood, coal, peat, diesel fuel or other biomass product. These flues, chimneys or other exhausts would typically range in size from 75mm (3in) to 250mm (10in).
Disclosure of the Invention
In accordance with the invention, there is provided an apparatus for the removal of particulate matter from air, the apparatus comprising:
a main body having an inlet and an outlet, the inlet including means for attaching the main body to an exhaust outlet of a device, the main body further including a cylindrical wall defining a chamber, and having a first electrode provided on at least a portion of the cylindrical wall and a second electrode arranged substantially centrally within the chamber;
a power supply means coupled to the first and second electrodes to provide electric potential thereto; and
temperature sensing means provided at the inlet and coupled to the power supply means, whereby the temperature sensing means is operable to cause the power supply means to switch on when the ambient temperature in the vicinity of the sensing means is above a predetermined level and to cause the power supply means to switch
off when the ambient temperature falls below the predetermined level, and such that, when the ambient temperature is above the predetermined level, the first and second electrodes cause electrostatic precipitation to occur within the chamber in the presence of particulate matter causing collection of particulate matter in the region of the first electrode.
The inlet may include baffle means to provide condensation of the moisture contained within the exhaust gases, the baffle being a plurality of metal plates with holes which are connected by metal cylinders, having the outer metal skin of these cylinders exposed to the atmosphere. Alternatively, the baffle may have a combination of circular plates with a series of holes contained within a metal cylinder with the outer skin being exposed to the atmosphere.
The first electrode may be comprised of a sheet of metal foil arranged around the cylindrical wall. Alternatively, the first electrode may be provided integral with the cylindrical wall.
A plurality of first electrodes may be provided on the cylindrical wall.
Brief Description of the Drawings
The invention will now be described, by way of example only, with reference to the accompany drawing, of which:
Figure 1 is a cross-section view of a small-scale exhaust incorporating the present invention.
Figure 2 is a perspective view of a preferred arrangement for the baffle which would be contained within the present invention.
Figure 3 is an elevation view of a preferred arrangement for the baffle which would be contained within the present invention.
Figure 4 is a perspective view of the holding structure which supports the emitter electrode within the present invention.
Best Mode(s) for Carrying Out the Invention
In a first embodiment of the invention, an apparatus 1 to remove particles from a cylindrical small-scale exhaust 2, is arranged to be located near the exit opening of the small-scale exhaust 2, and within a cylindrical chamber 3. Typically, the exhaust is arranged to collect exhaust fumes from a device (not shown) which emits hot air containing particulate matter.
The apparatus 1 comprises a main cylindrical body 4 which forms the cylindrical walls of chamber 5 and is constructed of a thermal and electrically insulating material. The cylindrical body 4 has two apertures 12, 13 provided at each end. Aperture 12 extends into lower tube 14. The lower tube 14 is of smaller diameter than the main body 4, the lower tube 14 being arranged to abut the exhaust 2. Aperture 13 is covered by a cap 15 being arranged to abut the main body 4 and protect the aperture 13 from weather while allowing the exhaust fumes to exit the apparatus 1 when they have passed through the main body 4.
Positioned on the inside wall of the cylindrical main body 4 is a collector electrode 6 supported by the main body 4. The collector electrode 6 can be affixed to the wall or integral thereto. The collector electrode 6 can be a single electrode made from metal and forming a cylindrical shape or more than one - spaced equidistantly around the circumference of the main body 4
Extending through the wall of the main body 4 is a holding plate 7. The holding plate 7 retains an emitter electrode 8 located substantially central to the chamber 5. The holding plate 7 is constructed of a thermal and electrically insulating material and may be in the shape of a U channel. The emitter electrode 8 is a metal rod screwed onto the holding plate 7 by means of an embedded bolt on holding plate 7. The emitter electrode 8 needs to be sufficiently spaced from the collector electrode 6 to prevent what is referred to as sparkover. This sparkover distance is dependent upon the size of the small-scale exhaust to which the present invention is to be attached
Fitted below the holding plate 7, and across the lower tube 14, there is a baffle plate 10. A thermal detection device 11 is provided above the baffle plate 10 on the inner wall of the lower tube 14. Preferably, the detection device 11 is a bimetallic strip. The lower tube 14 is positioned so as to funnel some of the hot air onto the bimetallic strip. Alternatively the switching may be controlled by a microprocessor controlled thermostatic device.
The baffle plate 10 is provided to allow for condensation of moisture contained within the exhaust gases and the chamber 5. The baffle plate 10 comprises a plurality of metal plates with holes, which are connected by metal cylinders, having the outer metal skin of these cylinders exposed to the atmosphere. Alternatively, the baffle may have a combination of circular plates with a series of holes contained within a metal cylinder with the outer skin being exposed to the atmosphere.
A high-voltage power supply 9 is connected to the mains supply (not shown) of the device to which the small-scale exhaust 2 is attached. The high-voltage power supply 9 is also coupled to collector electrode 6 and emitter electrode 8. The power supply 9 is also coupled to the thermal detection device 11 to receive a signal when the ambient temperature in the exhaust 2 reaches a predetermined temperature to switch the power supply 9 on and off as described in more detail below. Alternatively the switching may be controlled by a microprocessor controlled thermostatic device, rather than a bimetallic strip described above.
In use, this embodiment operates as follows:
When a fire is started in the device, the hot air and smoke produced by the fire enters the small-scale exhaust 2. As the hot air and smoke rises through the small-scale exhaust 2 the thermal detector 11 detects the ambient temperature in the exhaust 2.
When the ambient temperature reaches a predetermined temperature of between 25 and 30 degrees Celsius, the thermal detector 11 sends a signal to the high-voltage power supply 9 to switch it on. The power supply 9 is coupled to the emitter and collector electrodes 8, 6 so that the emitter electrode is at a negative potential and the collector electrode 6 is at a positive potential. When power is supplied to the emitter
electrode 8, a corona discharge is formed and ionisation occurs in the region of the emitter electrode 8 producing ionised particles. These ionised particles can then be used to electrostatically charge particulate matter in the region of the emitter electrode 8 within the corona. The use of corona discharges and the process of electrostatic precipitation to remove particulate matter in gases is well known and, as such, need not be described in any further detail herein.
Once powered, hot air and smoke rising through the small-scale exhaust 2 pass through the baffle plate 10. As the hot air and smoke pass through the baffle plate, the gases are cooled causing the resinous particles to loose moisture and become solid particulates. The hot air and smoke then enter the chamber 5 and passes through the corona generated by the high potential at the emitter electrode 8. As the particulates pass through the corona discharge this causes the particulates within the hot air and smoke to become negatively charged as discussed above.
As the hot air and smoke, including the negatively charged suspended particles, rises, the negatively charged suspended particles are attracted to the positively charged collector electrode 6. As much of the particulate matter is sticky due to the resinous particulates, they become stuck to the collector. This also causes the dry particulates to become stuck. Ideally the collector electrode 6 within the chamber 5 can be removed for ease of cleaning or replacement (as appropriate). This removal is achieved by removing the cap 15 and sliding the collector electrode 6 out of the main cylindrical body 4 and a new or cleaned collector electrode 6 is inserted.
When the fire is put out, or dies out, the ambient temperature falls, and when it falls below a predetermined level, then the thermal detector 11 acts to switch off the high- voltage power supply 9.
In accordance with a second embodiment of the invention, the apparatus 1 may be encased within an open-ended casing (not shown). The open-ended casing can then be retrofitted for installation within a small-scale exhaust 2.
In accordance with a third embodiment of the invention, the cylindrical main body 4 may be made completely of the collector electrode 6. Alternatively, the collector
electrode 4 can comprise a disposable sheet of metal foil arranged on the inner wall of the chamber 5.
Instead of being coupled to the mains supply, the high-voltage power supply 9 may include a battery (not shown). This battery is than charged, and re-charged, by electricity generated by a solar panel attached to the device to which the small-scale exhaust 2 is attached.
The high-voltage power supply 9 can be arranged to supply high voltage positive emitter electrode 8 and to the collector electrode 6 so that the emitter electrode is at the positive potential and the collector electrode is the negative potential to produce a positive discharge at the emitter electrode. Alternatively, the high-voltage power supply 9 supplies high voltage electricity to the emitter 8 and collector 6 is referenced to ground potential.
Ideally the collector electrodes within the chamber can be removed for ease of cleaning or replacement (as appropriate). This removal is achieved by removing the cap 15 and sliding the collector electrode 6 out of the main cylindrical body 4 and a new or cleaned collector electrode 6 is inserted.
It should be appreciated by the person skilled in the art that the present invention is not limited to the embodiments described and that variations and modifications thereon are considered within the scope of the invention. For instance, the above invention could be used within exhaust pipes of vehicles that run on diesel fuel.
Further, features disclosed in one embodiment may be combined with features disclosed in other embodiments to form yet further embodiments within the scope of the present invention.