EP2327481A2

EP2327481A2 - Method for cleaning an electric filter cell of an air filter

Info

Publication number: EP2327481A2
Application number: EP10190070A
Authority: EP
Inventors: Ilpo Kulmala; Hannu Salminen
Original assignee: Lo Group Oy
Current assignee: Lo Group Oy
Priority date: 2009-11-06
Filing date: 2010-11-05
Publication date: 2011-06-01
Also published as: FI20096157A; EP2327481A3; FI20096157A0

Abstract

The invention relates to a method for cleaning an air filter's electric filter cell, which comprises determining (220) a threshold value for a parameter relevant to the cleaning of a filter cell and executing (260) the cleaning of the filter cell upon crossing the threshold value of a parameter relevant to the filter cell cleaning. In addition, the invention relates to an air filter, which is capable of cleaning its electric filter cell, and to a ventilation system which includes an air filter capable of cleaning its electric filter cell.

Description

OBJECT OF THE INVENTION

The invention relates to a method for cleaning an air filter's electric filter cell. In addition, the invention relates to an air filter capable of cleaning its electric filter cell, and to a ventilation system provided with an air filter capable of cleaning its electric filter cell.

PRIOR ART

Over the recent years, the quality demands for industrial indoor air have become more stringent as requirements regarding occupational safety regulations and the energy economics of buildings are increasing. Efforts have been made to improve the indoor air quality and energy efficiency of various buildings for example by tightening the relevant legislation, both on national level and internationally.
In several branches of industry, such as for example metal, woodworking, construction and food industries, the indoor air in working facilities often develops considerable amounts of health-affecting flue gases generated in industrial production, or visually imperceptible micro-particles which are particularly harmful to asthmatics, persons with heart and lung diseases, and the elderly. In these demanding environments, the traditional air cleaning equipment does not provide a capability of complying with today's regulations or guidelines. Future regulations shall put traditional technologies in an even more difficult position, because the regulations will be tightened even further by the new upcoming, indoor-air-related regulations and guidelines for air cleaners.
Attempts have been made to improve the quality of air inhaled by employees working in industry for example by means of continuously operating electric air filters capable of being installed in air ducts, and capable of charging particles which are migrating in air ducts and harmful for respiratory tracts, and capable of collecting the charged particles by means of a powerful electric field, thus preventing the same from re-entering the indoor air. Collected particles become adhered to collection elements in the air filter and the collection elements become soiled thereby, causing a short circuit and a malfunction of the air cleaning device.
The cleaning of collection elements, which is usually carried out during working hours, is generally performed by removing the electric collection unit from an air filter present in a ventilation duct and by cleaning it manually. During the electric collection unit's cleaning operation, the air filter cannot be in service, as a result of which the amount of health-hazardous flue gases and micro-particles in the indoor air increases, causing a radical deterioration of the air quality in the working facilities.
The above type of continuously operating electric air filters function poorly from the standpoint of saving energy, and the energy consumption thereof increases even further because of dirt particles adhering to the collection units thereof in case the intervals between the collection units' cleaning operations become inadvertently too long. This, in turn, increases operating costs of the device.

SUMMARY OF THE INVENTION

One objective of the invention is to alleviate the foregoing drawbacks and to present a method which enables an air filter's electric filter cell to be cleaned as effortlessly as possible.
An objective of the invention is achieved with a method of claim 1, an air filter of claim 9, and a ventilation system of claim 10.
One embodiment of the invention relates to the method according to claim 1.
In addition, one embodiment of the invention relates to the air filter according to claim 9.
Still furthermore, one embodiment of the invention relates to the ventilation system according to claim 10.
Other embodiments of the invention are presented in the dependent claims.
According to one embodiment, the method for cleaning an air filter's electric filter cell comprises determining a threshold value for a parameter relevant to the cleaning of a filter cell present in an air filter capable of being installed for example in a ventilation duct, and, upon crossing the threshold value for the parameter relevant to the cleaning of a filter cell, executing the cleaning of the filter cell.
The term "electric filter cell" is used in reference to a filter cell, which is employed in air filters and which comprises at least one of the following: a collection unit for particles, a charging unit for particles, and filters present upstream and downstream of the collecting and charging unit.
The term "threshold value for a parameter" is used in reference to some preset value, the fulfillment or surpassing of which is under observation. Such a threshold value can be for example a time of day, a date, a period of time, or some measured value used as a basis for deciding the filter element cleaning time.
According to one embodiment of the invention, the air filter, which is capable of cleaning its electric filter cell, comprises a control device for determining a threshold value for a parameter relevant to the cleaning of a filter cell and a control device for executing the cleaning of a filter cell upon crossing the threshold value for the parameter relevant to the cleaning of a filter cell.
According to one embodiment of the invention, the ventilation system comprises an air filter, which cleans its electric filter cell and which comprises a control device for determining a threshold value for a parameter relevant to the cleaning of a filter cell and a control device for executing the cleaning of a filter cell upon crossing the threshold value for the parameter relevant to the cleaning of a filter cell.
In the air filter according to embodiments of the invention, the particles migrating in a ventilation duct are charged prior to the arrival thereof in the filter cell's electric field, in which the charged particles end up in an aluminum cell loaded with a reverse charge. The cell does not become significantly blocked and, hence, it does not create an obstruction to ventilation. As the device is soiled, there is activated an automatic washing operation which maintains the device clean and effective.
The air filter according to embodiments of the invention enables for example the use of displacement ventilation in industry, providing a possibility of exchanging all of the air in an industrial hall and removing the impurities of air from working facilities.
The air filter according to embodiments of the invention can be used in the heat recovery of indoor air upstream of the heat exchanger, whereby the heat recovery is enhanced as the thermal energy does not escape along with outgoing air.
It is also worthwhile to take notice of small pressure losses in air filters according to embodiments of the invention in comparison with traditional filters. The difference between pressure losses can be as much as 200 Pa, which has a major significance of energy economics in the electric power consumptions of fans. In this case, the reduction in the electric power consumption of fans is generally in the order of 10 to 30%.
In addition, the air filter according to embodiments of the invention enables indoor air to be cleaned also alongside a ventilation system in the form of a separate unit at a project outlet or in the form of a recirculation air cleaner, and it can be used in locations where incoming air is impure due to the environment and it is desirable to block the access of impurities to indoor spaces.
The cleaning method according to embodiments of the invention enables an effortless automatic air filter washing procedure, which provides for an improvement of the device in terms of its longevity, a reduction of costs incurred thereby, as well as an ability to increase the use of recirculation air and safety at work.
A significant reduction in the amount of adverse micro-particles in industrial facilities enhances also the work motivation of employees, reduces the number of sickness-related absences, improves the quality of products, and also protects the production machines.

BRIEF DESCRIPTION OF THE FIGURES

The detailed specification of figures contains a slightly more accurate description of the invention in its preferred embodiments with reference to the accompanying figures, in which

fig. 1: shows one air cleaning system of the invention in a schematic view,
fig. 2: shows an exemplary flowchart for one method of the invention for cleaning an air filter's electric filter cell,
fig. 3: shows an exemplary flowchart for one filter cell washing operation of the invention,
fig. 4: shows an air filter control device of the invention in a schematic view, and
figs. 5a-5d: show exemplary schematic views of an inlet air terminal device used in a ventilation system of the invention.

DETAILED DESCRIPTION OF THE FIGURES

An air filter according to the invention, which is encapsulated and readily connectable to a variety of ventilation ducts by means of adapters, is possible to install in the outlet, inlet or recirculation air duct of a building. The air filter provides for effective heat recovery in ventilation and/or the use of recirculation air, by virtue of which the energy consumption in ventilation is reduced to a significant degree.
The air filter's operating principle does not depend on its installation point. A fan is used for drawing the indoor or outdoor air into a ventilation duct, wherein the indrawn air borne impurities collide first with a dense woven wire mesh screen, functioning as a pre-filter for the air filter and having the largest airborne impurities adhere thereto. Upstream of the wire mesh screen it is also possible to employ a second separate pre-filter, for example when the air filter is accommodated in an incoming air duct.
However, the majority of particles advancing in a ventilation duct are of a sufficiently small size to pass through the pre-filtration and to migrate to a charging element of the air filter's electric filter cell, in which for example the small-size dust, fume and gas particles obtain a powerful electric charge of several kilovolts by means of a high voltage source fitted in attachment with the air filter. The charged particles advance to a collection element of the filter cell, which is supplied with a high voltage from the above-mentioned high voltage source. In response to a collection voltage of several kilovolts, the particles adhere to the filter cell having a charge of opposite sign, from which such particles can only be dislodged by washing.
Should impurities in gaseous form be still present in the air flowing through the filter cell, these can be removed by means of a filter positioned downstream of the air filter, for example by means of an activated carbon filter.
An air filter, which functions according to this principle, can be used for example in food industry, printing houses, machine shops, repair shops, bakeries, farming environment, and textile industry.
Fig. 1 shows one air cleaning system 100 of the invention, which includes an air filter 110 housing a filter cell (not shown in the figure) and a wash motor or washer (not shown in the figure) needed for its cleaning. The system includes also a washer control device (logic control) 120, which takes care of controlling the washer, magnetic valves 130a, 130b of the washing system, and a pressure booster pump 140. The control device 120 is controlled by way of its own user interface, containing a display, signal lights for information about the washer's operation, and keys for defining control commands. The user interface enables defining a point in time for the washing operation or a threshold value for some other parameter, which triggers the activation of a washing process. On the other hand, it is also possible to activate the wash program manually.
The filter cell washing can be carried out for example by a washer controlled by the control device 120, which washer proceeds, in accordance with a program, to perform one or more reciprocating wash cycles in a horizontal plane. Alternatively, the washer motion may consist of one or more reciprocating wash cycles at two different heights in a horizontal plane, whereby, after completing the wash, the washer proceeds from a first washing height up or down to a second washing height.
The magnetic valve 130a is used for making sure that wash liquid required by the washer is available from a wash liquid tank 150, and the magnetic valve 130b is used for controlling the availability of service water. The washer control device 120 is responsible for the inactivation and activation of inlet and outlet fans by means of a building's ventilation control center 160, as well as for switching off and on a high voltage unit (not shown in the figure) in a filter cell included in the air filter 110 at various stages of a cleaning operation. The water and wash liquid used by the washer are draining during a washing operation, and subsequent to that as the filter cell is drying, into a wash water tray 170, migrating therefrom along a pipe 180 to the floor drain.
Fig. 2 illustrates a way of executing a cleaning method 200 for an air filter's electric filter cell.
Starting procedures of a step 210 comprise for example attaching an air filter for a part of the ventilation system, coupling the air filter's incoming electricity, water and sewer lines, programming the air filter to working order, and activating the ventilation system (fans).
Once the ventilation system with its fans and filter is up and running, a step 220 can be used for determining some parameter for the execution of a cleaning program, said parameter being relevant to the quality of indoor air to be cleaned, and some threshold value for the parameter. Such a parameter can be for example a time between cleaning operations, making it possible to determine that the cleaning operation is performed every week or every other week, depending on the amount of impurities present in the indoor air. Optionally, the parameter can be some parameter representing the cleanliness of indoor air, such as an indoor air particle concentration or an indoor air particle size distribution, both being determinable for example by means of measuring equipment in communication with the control device. It is also possible that the number of monitored parameters is two and the fulfillment of both threshold values is followed by executing a wash or optionally by prioritizing one of the parameters, which alone is sufficient to trigger the cleaning process even if the other parameter were not fulfilled. The automatic wash sequence can be programmed to take place for example outside the production hours of a company. In this example, the parameter is a time period between cleaning operations and the threshold value is two weeks, such that the washing may take place every other weekend at nighttime.
According to one preferred embodiment of the invention, the method for cleaning an air filter's electric filter cell comprises steps of determining a threshold value for a parameter relevant to the cleaning of a filter cell and executing the filter cell cleaning upon crossing the threshold value of a parameter relevant to the filter cell cleaning.
According to one preferred embodiment of the invention, the air filter capable of cleaning its electric filter cell comprises a control device for determining a threshold value for a parameter relevant to the cleaning of a filter cell and a control device for executing the filter cell cleaning upon crossing the threshold value of a parameter relevant to the filter cell cleaning.
In one embodiment, the invention relates to a ventilation system, including an air filter capable of cleaning its electric filter cell, said air filter comprising a control device for determining a threshold value for a parameter relevant to the cleaning of a filter cell and a control device for executing the filter cell cleaning upon crossing the threshold value of a parameter relevant to the filter cell cleaning.
In steps 230 and 240, the control device continues monitoring the parameter value until the two-week period, selected for the threshold value, has lapsed, at which time the air filter wash program can be activated.
In one embodiment, the invention relates to a method as set forth in any of the preceding embodiments, said method further comprising a step of monitoring the value of a parameter relevant to the filter cell cleaning.
In one embodiment, the invention relates to an air filter as set forth in any of the preceding embodiments, said air filter further comprising a control device for monitoring the value of a parameter relevant to the filter cell cleaning.
In one embodiment, the invention relates to a ventilation system as set forth in any of the preceding embodiments, said ventilation system comprising an air filter which further comprises a control device for monitoring the value of a parameter relevant to the filter cell cleaning.
In one embodiment, the invention relates to a method as set forth in any of the preceding embodiments, in which method the parameter to be determined and relevant to the cleaning of a filter cell is at least one of the following: a time, a parameter relevant to the indoor air particle concentration, and a parameter relevant to the indoor air particle size.
In one embodiment, the invention relates to an air filter as set forth in any of the preceding embodiments, in which air filter the parameter to be determined and relevant to the cleaning of a filter cell is one of the following: a time, a parameter relevant to the indoor air particle concentration, and a parameter relevant to the indoor air particle size.
In one embodiment, the invention relates to a ventilation system as set forth in any of the preceding embodiments, said ventilation system including an air filter in which the parameter to be determined and relevant to the cleaning of a filter cell is at least one of the following: a time, a parameter relevant to the indoor air particle concentration, and a parameter relevant to the indoor air particle size.
In a step 250, the filter cell charging and collecting voltages are switched off and the inlet and outlet fans are shut down.
In one embodiment, the invention relates a method as set forth in any of the preceding embodiments, which further comprises switching off the filter cell voltages, the inlet air fan and/or the outlet air fan prior to the filter cell cleaning. The high voltage unit in attachment with the filter is controlled by the air filter control device so as to switch off both the voltage applied for charging the particles and the voltage applied for collection. In addition, the control device gives the ventilation system an instruction to shut down the fans in order to enable execution of the wash program.
In one embodiment, the invention relates to an air filter as set forth in any of the preceding embodiments, said air filter further including control means for switching off the filter cell voltages, the inlet air fan and/or the outlet air fan prior to the filter cell cleaning.
In one embodiment, the invention relates to a ventilation system as set forth in any of the preceding embodiments, said ventilation system comprising an air filter which further includes control means for switching off the filter cell voltages, the inlet air fan and/or the outlet air fan prior to the filter cell cleaning.
After shutting down the high voltages and the fans, there is a momentary waiting period prior to executing the filter cell wash and rinses in a step 260. The wash may consists of several washing and rinsing cycles and washing of several filter cells, depending on how many filter cells are included in the air filter. Execution of the wash will be discussed in more detail in reference to fig. 3.
In one embodiment, the invention relates to a method as set forth in any of the preceding embodiments, wherein the filter cell cleaning, which is applied to at least one filter cell, comprises rinsing the filter cell with water prior to washing the filter cell, washing the filter cell with a wash liquid by means of an appropriate washer, and finally rinsing the filter cell after the washing.
In one embodiment, the invention relates to an air filter as set forth in any of the preceding embodiments, said air filter comprising a washer which in the filter cleaning is adapted to rinse the filter cell with water prior to washing the filter cell, to wash the filter cell with a wash liquid, and finally to rinse the filter cell after the washing.
In one embodiment, the invention relaters to a ventilation system as set forth in any of the preceding embodiments, said ventilation system containing an air filter which includes a washer adapted in the filter cleaning to rinse the filter cell with water prior to washing the filter cell, to wash the filter cell with a wash liquid, and finally to rinse the filter cell after the washing.
After completing the number of washing cycles necessary for cleaning the air filter's all filter cells, there is a momentary waiting period prior to re-activating the fans in a step 270. The fans are allowed to blow a sufficiently long time, for example 60 to 90 minutes, for giving the filter cell enough time to dry prior to switching on the high voltage source, after which the air filter is back in working order in a step 280.
In one embodiment, the invention relates to a method as set forth in any of the preceding embodiments, which further comprises activating the ventilation system's inlet air fan and outlet fan, whereby the filter cell dries prior to switching on the filter cell charging and collecting voltages.
In one embodiment, the invention relates to an air filter as set forth in any of the preceding embodiments, which further comprises a control device adapted to activate the ventilation system's inlet air fan and outlet air fan, whereby the filter cell has enough time to dry prior to switching on the filter cell charging and collecting voltages.
In one embodiment, the invention relates to a ventilation system as set forth in any of the preceding embodiments, said ventilation system including an air filter which further comprises a control device adapted to activate the ventilation system's inlet air fan and outlet air fan, whereby the filter cell dries prior to switching on the filter cell charging and collecting voltages.
In one embodiment, the invention relates to a method as set forth in any of the preceding embodiments, which method further comprises, after activating the ventilation system's inlet air fan and outlet air fan, switching on the filter cell charging and collecting voltages.
In one embodiment, the invention relates to an air filter as set forth in any of the preceding embodiments, said air filter further including a control device for switching on the filter cell charging and collecting voltages after activating the ventilation system's inlet air fan and outlet air fan.
In one embodiment, the invention relates to a ventilation system as set forth in any of the preceding embodiments, said ventilation system comprising an air filter which further includes a control device for switching on the filter cell charging and collecting voltages after activating the ventilation system's inlet air fan and outlet air fan.
Fig. 3 illustrates an execution chart for a filter cell washing operation 300, whose starting step 310 comprises, among other things, identifying the crossing of a parameter threshold value that triggers a washing operation, switching off the voltages of the air filter's high voltage unit, and shutting down the ventilation system's fans, as explained in connection with the previous figure.
There is a delay which is followed by opening a magnetic valve of the service water side and activating a pressure booster pump. Next, in a step 320, an actual wash sequence is started by executing the filter cell rinsing, in which, on the basis of an instruction given by the control device, the washer (nozzle), which establishes a consistent jet and travels in a horizontal plane under the drive of its motor, sets off from an "initial condition" and, at the same time, the control device gives an instruction to a water valve, whereby the filter cell rinsing may begin. The control device maintains the wash motor control activated for as long as the washer has returned from a first washing cycle. The air filter is provided with at least one damper, the purpose of which is to prevent the water and wash liquid used in rinsing and washing operations from entering ventilation ducts and thereby to eliminate the emergence of harmful and hard-to-eradicate growths in ventilation ducts.
In one embodiment, the invention relates to a method as set forth in any of the preceding embodiments, wherein the washing water and washing liquid used in cleaning are prevented from entering the ventilation system's ventilation ducts by means of one or more dampers installed in the air filter.
In one embodiment, the invention relates to an air filter as set forth in any of the preceding embodiments, in which air filter the damper is adapted to prevent the washing water and washing liquid used in cleaning from entering ventilation ducts.
In one embodiment, the invention relates to a ventilation system as set forth in any of the preceding embodiments, said ventilation system featuring an air filter whose damper is adapted to prevent the washing water and washing liquid used in cleaning from entering ventilation ducts.
In a step 330, discovering that the washer has returned to the start position, the control device issues a control instruction to open a magnetic valve for the washing agent, whereby the washer begins a second washing cycle with a mixture of washing agent and water, while the service water valve is till open and the pump is working. The washing agent compound may consist, for example, of alcohol ethaxylate, phosphoric acid, and citric acid. Once the washer has returned to the start position, the valves as well as the pump are closed and there is a pause in the washing operation during which the water and washing agent used for filter cell washing have time to exit from the filter cell and for the washing water tray to drain out.
After the pause, in a step 340, the control device is allowed to re-issue the control instructions, whereby the washer, the pump, and the water valve become activated, and the washer is now performing two washing cycles after which the pump and the water valve are closed and the process has a pause for dewatering.
In a step 350, a check is conducted to see whether the control device is programmed to perform the filter cell wash yet another time, and, if this is the case, a return is made to the initial rinsing step 320.
If, according to the washing program, the filter cell has been washed, a check is made in a step 360 to see whether the air filter contains other washable filter cells, and, if the air filter consists of several cells, a return is made to step 320.
If all filter cells have been washed, the washing program is terminated in a step 370 and, after a brief delay, the fans are activated as explained in connection with fig. 2.
Fig. 4 illustrates a control device 400 for an air filter of the invention, said device including a processor 410, which carries out instructions given to be executed thereby and which processes application data, as well as a user interface 430 for receiving control commands given by a user. The user interface can be for example a keypad, a touch screen, or a touch surface. The control device 400 comprises additionally a data transfer interface 430, by way of which it is able to forward the control instructions for example to a high voltage unit, fans, a pressure booster pump, valves, a washer, and indoor air measuring equipment, as well as to receive information therefrom. In addition, the control device 400 includes a display 460, by way of which the user is supplied with information relevant to the operation of the control device and the air filter.
A memory 420 contains for example a wash application with its control instructions 422 and some control data 424. In addition, there may be a measuring application 426 in the event of measuring data being utilized in connection with the air filter.
Figs. 5a-5d illustrate an incoming air terminal device 500, which is included in a ventilation system of the invention and to be accommodated in indoor working facilities, and which includes an adapter member 510 by means of which the incoming air terminal 500 can be connected to the inlet air duct, an air control member 520 with its air deflectors 530, and a terminal member 540 featuring a curvilinear shaped low-speed element (perforated damper) 550 and a blow slit 560.
The incoming air terminal device 500 is used for combining a high flow-speed and low air-stream blow jet (carrier jet) 570, emerging from the narrow blow slit 560, with a low-speed inlet air distribution, the latter being carried out in the terminal member 540 by means of the low-speed element 550. It is a vertical component in the momentum of the downward-directed blow jet 570 which compensates for the upward rising tendency of an over warm air stream 580 coming in through the low-speed element, as a result of which the over warm air 580 can be delivered over a desired area in the working facilities. The incoming air terminal's blow jet 570 can also be used for guiding over warm incoming air towards a breathing zone.
The incoming air terminal device 500 can be provided with a fixed blow slit 560, whereby the blow jet 570 is always applied at the same height and over the same range. Alternatively, the incoming air terminal device can have its blow slit 560 configured in an adjustable manner, thus enabling the blow jet 570 to be regulated as desired in terms of its direction. The incoming air terminal device 500, both with a fixed and adjustable blow slit 560, enables increasing the effective range of inlet air, enhances the operation of ventilation, and improves the quality of air.
Presented above are just a few embodiments of the inventive solution. Naturally, the principle according to the invention can be modified within the scope of protection defined by the claims, regarding for example details as well as intended applications of a given implementation.

Claims

A method for cleaning an electric filter cell of an air filter, which method comprises determining (220) a threshold value for a parameter relevant to the cleaning of the filter cell and executing (260) the cleaning of the filter cell upon exceeding the threshold value of the parameter relevant to the filter cell cleaning.
The method of claim 1, which comprises monitoring (230) a value of the parameter relevant to the filter cell cleaning.
The method of claim 1 or 2, wherein the parameter to be determined and relevant to the filter cell cleaning is a time or a parameter relevant to an indoor air particle concentration.
The method of any of the preceding claims, which further comprises switching off (250) filter cell voltages, an inlet air fan, and an outlet air fan prior to the filter cell cleaning.
The method of any of the preceding claims, wherein the filter cell cleaning comprises rinsing (320) the filter cell with water prior to washing the filter cell, washing (330) the filter cell with a wash liquid by means of an appropriate washer, and rinsing (340) the filter cell after the washing operation.
The method of any of the preceding claims, which further comprises activating (270) the inlet air fan and the outlet air fan, whereby the filter cell dries prior to switching on the filter cell voltages.
The method of any of the preceding claims, which further comprises switching on (270) the filter cell voltages after the air filter's inlet air fan and outlet air fan have been activated.
The method of any of the preceding claims, which comprises the use of a damper for preventing the washing water and washing liquid used in cleaning from entering ventilation ducts.
An air filter, which is capable of executing the method of any of claims 1-8.
A ventilation system, which comprises the air filter of claim 9.