Air humidification and/or purification

Abstract

The present application relates to an apparatus for purifying and/or humidifying air, and a related method for purifying and/or humidifying air. The apparatus comprises a rotary filter (1), a fan (9, 10) for passing air through the rotary filter (1), and a reservoir (4, 5), and wherein the rotation speed of the rotary filter (1) and the settings of the fan (9, 10) depend on the ambient relative humidity and ambient gas pollutant concentration. The apparatus combines the feature of chemisorption with the use of a rotary filter (1), thereby providing an apparatus which is able to purify air and/or regulate the ambient humidity based on humidity levels and levels of a target gas pollutant in the air. The invention removes the need for a pump for liquid transport, removes the need for frequent and expensive filter changes by the user, and instead only requires the user to periodically refresh the filtration solution in the reservoir (4, 5).

Claims

1. An apparatus for humidifying and/or purifying air, the apparatus comprising: a rotary filter, a fan for passing air through the rotary filter, and a reservoir, wherein the settings of the fan and the rotation speed of the rotary filter are controlled by feedback from a humidity sensor, wherein: settings of the fan and the rotation speed of the rotary filter are further controlled by feedback from a gaseous pollutant sensor.

2. The apparatus according to claim 1, wherein the rotary filter comprises one or more hydrophilic materials.

3. The apparatus according to claim 2, wherein the rotary filter comprises one or more of ceramics, hydrophilic polymeric materials, hydrophilic fibrous materials, or hydrophilic paper.

4. The apparatus according to claim 1, wherein the rotary filter has a surface area with air of at least 0.1 m.sup.2.

5. The apparatus according to claim 1, wherein the rotary filter has a corrugated or honeycomb structure, and wherein the corrugated or honeycomb structure comprises a plurality of open channels.

6. The apparatus according to claim 5, wherein the open channels have a length of at least 10 mm and/or a pore diameter of between 0.5-2 mm.

7. The apparatus according to claim 5, wherein the open channel walls are permeable to a filtration solution and no more than 1 mm thick.

8. The apparatus according to claim 1, wherein the rotary filter is controlled to rotate if the level of a gaseous pollutant sensed by the gaseous pollutant sensor is above a pre-set level.

9. The apparatus according to claim 1, further comprising a user reminder mechanism for indicating when to refill the reservoir, and wherein the user reminder mechanism is activated when a gaseous pollutant sensed by the gaseous pollutant sensor is above a pre-set level for a pre-set amount of time.

10. The apparatus according to claim 1, wherein the rotary filter is a chemisorption filter.

11. The apparatus according to claim 1, wherein the rotary filter is controlled to rotate and the fan is controlled to produce an air flow, when an ambient relative humidity level received from the humidity sensor is below a pre-determined humidity value.

12. The apparatus according to claim 1, wherein the rotary filter is controlled to intermittently rotate and wherein the fan is controlled to continuously produce an air flow, when the ambient relative humidity level received from the humidity sensor is above a pre-determined humidity value, and when a gaseous pollutant concentration level received from the gaseous pollutant sensor is above a pre-determined gaseous pollutant level.

13. The apparatus according to claim 1, wherein the rotation of the rotary filter and the fan are controlled to be deactivated, when ambient relative humidity level received from the humidity sensor is above a pre-determined humidity value and when the gaseous pollutant concentration level received from the gaseous pollutant sensor is below a pre-determined gas pollutant level.

14. The apparatus according to claim 1, wherein the rotary filter is partly located in the reservoir.

15. A method of purifying and/or humidifying air, the method comprising: rotating a rotary filter, thereby depositing a filtration solution onto the rotary filter and dispersing the deposited filtration solution through the interior of the rotary filter; passing air through the rotary filter; and controlling a rotation speed of the rotary filter and the air flow through the rotary filter in dependence upon an ambient relative humidity; wherein: controlling a rotation speed of the rotary filter and the air flow through the rotary filter is further dependent upon a gaseous pollutant concentration in the ambient air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a schematic view of one embodiment of the apparatus according to the invention.

(3) FIG. 2 shows a schematic view of one embodiment of the apparatus according to the invention.

(4) FIG. 3a shows an air-permeable rotary filter according to one embodiment of the invention.

(5) FIG. 3b shows a schematic cross-sectional view of an air-permeable rotary filter according to one embodiment of the invention.

(6) FIG. 4 shows a schematic view of one embodiment of the apparatus according to the invention.

(7) FIG. 5 shows a cross-sectional view of an apparatus according to one embodiment of the invention.

(8) FIG. 6 shows a cross-sectional view of an apparatus according to one embodiment of the invention.

(9) FIG. 7 shows a schematic view of an appliance comprising an embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(10) Throughout the description reference is made to filtration solution. This is a solution that may be used to wet a chemisorption filter. By wetting the filter, a high-performance chemisorption of polluting gas from air is ensured, even under conditions of a low ambient relative humidity.

(11) The present invention advantageously combines the feature of chemisorption with the use of a wetted air-permeable rotary filter, thereby providing an apparatus which is able to both purify the air and regulate the relative humidity of the air.

(12) Wetting of the air-permeable rotary filter is achieved by deposition of the filtration solution onto the air-permeable rotary filter as a result of rotation of the rotary filter, followed by effective dispersal of the filtration solution through the air-permeable rotary filter. In some embodiments, the deposited filtration solution disperses throughout substantially the entire volume of the air-permeable rotary filter. This wetting system allows the apparatus to achieve a high-performance chemisorption of polluting gas from air, even under conditions of a low ambient relative humidity.

(13) The degree of wetting of the rotary filter can be controlled, in part, by controlling the speed of rotation of the rotary filter.

(14) When the air is particularly dry, the rate of air humidification and air cleaning can be increased by increasing the rotational speed of the rotary filter. This increases the rate of rotary filter wetting, thereby increasing the rate of moisture evaporation from the filter into air.

(15) Under conditions of high relative ambient humidity, wetting of the air-permeable rotary filter can be terminated by termination of rotation of the air-permeable filter. Airflow through the rotary filter, generated by the fan, may then be continued, and the filter thus dries. Drying of the rotary filter stops air humidification, while the chemical species capable of absorbing ambient polluting gas(ses) are retained inside the rotary filter, thereby maintaining the air purification functionality of the apparatus.

(16) When neither air humidification nor air purification is needed, both the airflow through the filter, as generated by the fan, and rotation of the air-permeable rotary filter are terminated.

(17) In preferred embodiments, the rotational speed of the filter depends upon the ambient relative humidity.

(18) The invention removes the need for frequent and expensive filter changes by the user, and instead requires the user to only periodically refresh or replace the filtration solution. The invention also removes the need for a pump for transporting the filtration solution to the filter.

(19) The rotary filter may be made of any suitable construction or structure. Advantageously, the rotary filter is constructed in such a way that it provides a large contact surface area with air, whilst incurring only a relatively low pressure drop when a fan passes an airflow through the filter. For example, the rotary filter may possess a honeycomb structure or a corrugated structure with a plurality of parallel open channels for air passage as shown in FIGS. 3a and 3b. FIG. 3b shows the open channels (1a) and corrugations (1b) in the rotary filter. The rotary filter may have a surface area of at least 0.1 m.sup.2, at least 0.2 m.sup.2, at least 0.3 m.sup.2, or at least 0.4 m.sup.2.

(20) In preferred embodiments, the pore diameter of the air channels or other surface area-increasing features of the rotary filter is between 0.2 mm and 5 mm, more preferably between 0.3 mm and 3 mm, even more preferably between 0.4 mm and 2.5 mm, and most preferably between 0.5 mm and 2 mm.

(21) In preferred embodiments, the air channels are substantially straight.

(22) In preferred embodiments, the air channels have a length of at least 10 mm. This helps to ensure a sufficiently long residence time of air inside the channels when a flow of air is passed through the filter for air pollutants to be absorbed. A residence time of at least 5-10 ms is required to enable a satisfactory degree of air cleaning and/or air humidification to be accomplished. During the residence time of air in the air channels of the rotary filter, air cleaning occurs via diffusional transport of polluting gas to the air channel walls where the gas reacts with the chemisorbing species comprised in the air channel walls. Simultaneously, air humidification occurs via diffusional transport of moisture from the wet air channel walls into air. The air channel length substantially corresponds to the filter thickness.

(23) The rotary filter may be made of any suitable material. Advantageously, the rotary filter comprises one or more hydrophilic materials, such as ceramics, hydrophilic polymeric materials, hydrophilic fibrous materials, or hydrophilic paper. By comprising hydrophilic materials in the filter structure, a rapid dispersion of deposited filtration solution on the rotary filter may be achieved. In addition, rapid dispersion of deposited filtration solution on the rotary filter is facilitated throughout the filter structure, driven by the forces of capillarity, hydration, and gravity.

(24) In preferred embodiments, the walls of the air channels comprise hydrophilic materials that are permeable to filtration solution but substantially impermeable to air passage. In this way, filtration solution can conveniently be drawn into and contained inside the porous hydrophilic air channel walls, thereby becoming directly and intimately exposed to air passing through the air channels. The intimate exposure and the overall large surface area of the channel walls in the rotary filter structure facilitate a rapid transfer of moisture from the filtration solution in the channel walls into the air. Simultaneously, a very effective transfer of polluting gas from the air to the gas-absorbing filtration solution in the channel walls is accomplished. This results in an efficient rate of air humidification and/or air cleaning.

(25) The air-permeable rotary filter shown in FIG. 3a is a pleated structure of PET and Rayon.

(26) The filtration solution may comprise any agent suitable for use in an air purification or air humidification system. In some embodiments, the filtration solution may be an aqueous solution. In some embodiments, the filtration solution may be water. In some embodiments, the composition of the filtration solution may be tailored for a specific pollutant(s), such as acidic gaseous pollutants, or volatile organic compounds such as formaldehyde, benzene, methylene chloride. For example, an aqueous alkaline filtration solution, such as an aqueous solution comprising (bi-)carbonate salts (e.g., NaHCO.sub.3, KHCO.sub.3, K.sub.2CO.sub.3) or hydroxide salts (e.g., KOH, NaOH), would help to effectively clean the air from acidic gaseous pollutants such as SO.sub.2 and carboxylic acids like acetic acid and formic acid. Alternatively, a filtration solution which is intending to remove formaldehyde from the atmosphere may comprise an alkanol-amine such as tris-hydroxymethyl-aminomethane, either alone, or together with a bi-carbonate salt such as KHCO.sub.3 and a humectant such as potassium-formate. Preferably, the amount of tris-hydroxymethyl-aminomethane in a filtration solution is no more than 25% w/w. Preferably, the amount of potassium bicarbonate in a filtration solution is no more than 15% w/w.

(27) In some embodiments, the filtration solution may also have disinfectant properties, for example due to the concentration level of salt(s) in the solution which, by itself, prevents the growth and survival of microorganisms. In alternative embodiments, one or more disinfectant agents may be added to the filtration solution. Disinfectant agents which are suitable for use in an air purification system or an air humidifier may be used, and include agents such as propolis and fluorides. The presence of a disinfectant in the filtration solution confers the advantage that the features of the apparatus in contact with the filtration solution, including the air-permeable rotary filter, will not become a source of micro-organisms. This may help to inactivate, amongst others, micro-organisms associated with the apparatus.

(28) In some embodiments, the apparatus is provided as an appliance, wherein the apparatus is located within a housing which comprises means for activating and deactivating the apparatus. In some embodiments, the appliance or housing is provided with a user interface, to allow selection of the desired function (air purification and humidification; air purification only; air humidification only, or selection of function as dependent upon ambient RH values). In some embodiments, selection of the desired function(s) is done by an app which is, for example, controlled by a user. For example, an app running on a smartphone of the user.

(29) In some embodiments, the apparatus or appliance further comprises a user reminder mechanism, such as the illumination of a light on the apparatus or any housing in which it is inserted or encased, or the activation of a sound, or the activation of an alert within an app running on a smartphone of the user, in order to indicate to the user when to refill the tank or renew the filtration solution. In some embodiments this may be effected via a sensor and an algorithm, as provided, for example, by a suitably programmed computer.

(30) In some embodiments, the apparatus can be used substantially only as an air humidifier. To operate the apparatus as a humidifier only, the rotary filter is required to be maintained in a wetted state by maintaining rotation of the rotary filter, thereby maintaining wetting of the rotary filter with a filtration solution from the reservoir. The filtration solution comprises water, and, in some embodiments, may comprise one or more agents for removal of gaseous pollutant(s). In some embodiments, the fan speed and rotary filter rotation speed are controlled by means of a humidity sensor, which uses the set-point ambient relative humidity levels RH.sub.max and RH.sub.min. In preferred embodiments, a measured RHRH.sub.max triggers the appliance to stop both the rotary filter rotation and the fan-driven airflow. This ceases wetting of the rotary filter with filtration solution, substantially stops the transfer of moisture from the filter into the ambient air, and thus prohibits further air humidification. In preferred embodiments, a measured RHRH.sub.min triggers the appliance to start both rotation of the rotary filter and activates the airflow through the rotary filter via the fan. This enables wetting of the rotary filter with water, enables moisture transfer from the filter into the airflow passing through the filter, thus realizing air humidification. Preferred values for the set-point RH levels are RH.sub.min=35% and RH.sub.max=65%. The user would be reminded to add water to the reservoir when required.

(31) In some embodiments, the appliance is set so that no air humidification is needed within the ambient RH range RH.sub.min<RH<RH.sub.max. Both the fan and the filter rotation motor can remain OFF in the latter RH range.

(32) By making the rotation speed of the air-permeable rotary filter dependent on the ambient relative humidity, it becomes possible to adjust the amount of evaporated moisture and the evaporation rate to the ambient relative humidity. Specifically, by stopping the rotation when the relative humidity exceeds a maximum set-point level RH.sub.max, the wetting of the rotary filter with filtration solution is terminated. This quickly leads to drying of the rotary filter, which ends the air humidification (even when the airflow through the rotary filter continues) and prevents the occurrence of an uncomfortably high ambient relative humidity level. By starting rotation of the rotary filter and thus rotary filter wetting when the ambient relative humidity falls below a minimum set-point level RH.sub.min, air humidification becomes initiated only when needed for preventing the air to become too dry. When the ambient relative humidity falls well below RH.sub.min, the rotation speed and thereby the rate of filter wetting can be increased to increase the rate of air humidification.

(33) In alternative embodiments, the apparatus can be used substantially only as an air purifier. To operate the apparatus as a purifier only, air is continuously passed through the air-permeable rotary filter via activation of the fan, irrespective of the ambient RH level. In such embodiments, rotation of the rotary filter occurs periodically (for example only for a few minutes every day (for example for less than 10, 8, 5, 3, 2 or 1 minute) in order to periodically wet the rotary filter briefly with the filtration solution, thereby ensuring the timely replacement/regeneration of the initially dissolved chemical species in the filtration solution on and inside the rotary filter. Once rotation of the rotary filter ceases, the apparatus operates as an air purification device only, as air is passed through the rotary filter by the fan, and water from the filtration solution which is located inside the rotary filter evaporates until the filter is dry, thereby leaving only the initially dissolved chemical species behind inside the rotary filter. The chemical species inside the filter continue to chemisorb gaseous pollutants from the airflow. In the air purification mode, the ON/OFF and speed settings of the fan can be controlled by means of feedback from a sensor capable of measuring in air the concentration of the gaseous pollutants that can be absorbed by the active chemical species in the filtration solution. The user would be reminded to add filtration solution and/or water in the reservoir on a periodic basis by means of a reminder mechanism.

(34) To act as an air humidifier and an air purifier, the settings of the fan and the filter rotation speed are controlled by feedback from, for example, both a humidity sensor and a gaseous pollutant sensor. In preferred embodiments, the apparatus is set to maintain a level of atmospheric humidity of around RH 50%, as the performance of a chemisorption filter may, as discussed above, be significantly affected by the relative humidity, and maintenance of an ambient humidity level of around 50% ensures effective adsorption of pollutants such as formaldehyde. The functionalities of the apparatus towards both air humidification and air purification are thus activated based upon measured values of the RH and the gaseous pollutant concentration in the ambient air.

(35) The one-pass removal efficiency of pollutant(s) from air (i.e., the accomplished percentage removal of pollutants when passing the air once through the filter) depends on parameters such as the air flow rate through the air-permeable rotary filter, the rotary filter design parameters, and the concentration of the filtration solution. Typically, the higher the air/filter contact surface, the higher the one-pass removal efficiency. For example, the one-pass efficiency can be up to 70-90% for formaldehyde removal if the air flow is around 1 m/s, filter surface is >0.1 m.sup.2, and the organic amine solution concentration is around 20% w/w. Change of any of the parameter will result in a change of removal efficiency.

(36) As an example, a one-pass formaldehyde removal efficiency of more than 90% can be achieved with a superficial air velocity v.sub.s1 m/s at the filter face when using a rotary corrugated filter composed of a hydrophilic paper-like material wherein the air channels are 0.5-2 mm in diameter and 10 mm in length; the corrugation pitch is 3 mm; and the air channel walls are 1 mm thick, and when the porous air channel walls comprise filtration solution wherein tris-hydroxymethyl-aminomethane is dissolved at a 5% w/w concentration.

(37) In preferred embodiments, the rotation speed of the air-permeable rotary filter is such that flooding of the air-permeable parts (e.g., the air channels) of the rotary filter is avoided, yet the rotary filter remains wet in all positions during revolution of the frame, so as to avoid local drying of the rotary filter and thus local accumulation of, for example, salts. It was found that this can be accomplished with a rotary filter possessing a 0.1 m.sup.2 face area by limiting its rotation speed to 2 rpm or less, the rotation speed decreasing at increasing RH of the ambient air. In alternative embodiments, the rotation speed of the rotary filter can be controlled and adjusted via a duty cycle wherein short periods of rotary filter rotation/wetting are separated by longer periods wherein no rotary filter rotation occurs and wherein excess filtration solution is allowed to drain from the rotary filter back into the reservoir or tray, and wherein the moisture from the remainder of the filtration solution inside the filter evaporates into the air passing through the filter.

(38) As discussed above, in some embodiments, the apparatus and/or appliance comprises a user reminder mechanism in order to indicate to the user when to refill the tank or renew the filtration solution. In some embodiments the reminder may relate to the total volume of air that has passed through the filter since the last renewal of the filtration solution. The total displaced air volume through the filter during a set period of time is readily derived from the air flow settings of the apparatus during the set period of time. When the total displaced air volume exceeds a pre-set level, a reminder mechanism is thus activated to signal to the user that the filtration solution is to be replaced with a fresh filtration solution. In alternative embodiments, the apparatus may comprise a formaldehyde gas sensor, which activates a mechanism which causes the rotary filter to rotate if the level of formaldehyde in the ambient air is above a pre-set level, thereby wetting the rotary filter. If the formaldehyde concentration registered by the sensor then remains above the pre-set level, the sensor activates a reminder mechanism, alerting the user that the filtration solution requires replacing. Alternatively, such a reminder may comprise a mechanism for detecting when the filtration solution is below a pre-set level. For example, the reminder mechanism may be a magnet, mounted in a float, in the reservoir or tray. When the level of filtration solution drops, the float also drops its position, and, when the filtration solution reaches a pre-set level, the magnet sends a signal to a reed switch. The reed switch then communicates with a control system, for example via an algorithm, as provided by a suitably programmed computer, to signal an alert to the user.

(39) FIG. 1 shows a schematic view of one embodiment of the apparatus according to the invention. The apparatus comprises an air-permeable rotary filter 1, housed within a frame 2, which comprises one or more buckets 3, a tank 4 and a tray 5. A filtration solution is located in the tray 5, and is replenished by filtration solution from the tank 4 via a passive level control valve 6. The arrow indicates rotation of the rotary filter in use.

(40) The term bucket as used herein denotes any means which is suitable for collecting filtration solution from the reservoir, transporting the filtration solution beyond at least the lowest point of the frame, and depositing the filtration solution substantially over or substantially within the rotary filter.

(41) As shown in FIG. 2, the tank 4 is detachable from the tray 5. Advantageously, the rotary filter 1 is positioned above the tray 5 at an appropriate height so that the buckets 3 on the frame 2 scoop up a volume of the filtration solution when they rotate to the bottom position. As the buckets 3 then rotate to the top position, the filtration solution is deposited onto the rotary filter 1.

(42) In some embodiments, the apparatus further comprises one or more ribs, as shown as feature 7 in FIGS. 4-6. Advantageously, the rib(s) occlude area(s) around the air-permeable rotary filter, via which air flow would otherwise leak instead of passing through the rotary filter (shown as a dotted line in FIGS. 5 and 6). Reduction of air flow leakage typically results in improved air humidification and cleaning performance, due to improved flow of the air via the intended pathway (i.e. through the filter).

(43) As shown in FIG. 4, during use of the apparatus in humidification mode, the frame 2 rotates, causing the bucket(s) 3 to rotate and thus contact the filtration solution in the tray 5. The filtration solution is scooped into a bucket 3 and transported as rotation of the frame continues. The filtration solution is deposited over the air-permeable rotary filter 1 as the frame 2 rotates, thereby wetting the air-permeable rotary filter 1. Any excess filtration solution flows through the rotary filter structure and eventually drains back into the tray 5. As ambient air passes through the rotary filter, pollutant(s) react with the filtration solution located on and inside the rotary filter, and become removed from the air.

(44) FIGS. 5 and 6 illustrate the location of the motor 8, fan rotor 9, fan scroll 10 and area in which a rotary filter, such as a conventional air-permeable pleated filter or corrugated filter, can be located 11.

(45) FIG. 7 illustrates an appliance comprising an embodiment of the apparatus according to the present invention, comprising an air inlet 12, rear cover of the appliance 13, optional hepa filter 14, rotary filter 1, tank 4, tray 5, fan rotor 9, fan scroll 10, air outlet 15, and front cover of the appliance 16. Hepa is a well-known abbreviation of High Efficiency Particulate Arrestance/Air, see https://en.wikipedia.org/wiki/HEPA.

(46) It should be noted that the terms humidification and/or purification and humidifying and/or purifying as used herein mean the processes of: purification alone; humidification alone; or purification and humidification.

(47) It should be noted that the abbreviation w/w % is used herein to mean weight/weight percentage.

(48) The above embodiments as described are only illustrative, and not intended to limit the technique approaches of the present invention. Although the present invention is described in detail referring to the preferable embodiments, those skilled in the art will understand that the technique approaches of the present invention can be modified or equally displaced without departing from the scope of the technique approaches of the present invention, which will also fall into the protective scope of the claims of the present invention. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope.