WO2013010328A1

WO2013010328A1 - Air purifier with electric field regeneration

Info

Publication number: WO2013010328A1
Application number: PCT/CN2011/077410
Authority: WO
Inventors: Chi Keung Rudy Chan; Ka Tung Ho
Original assignee: Rht Limited
Priority date: 2011-07-21
Filing date: 2011-07-21
Publication date: 2013-01-24
Also published as: HK1193773A1; CN103702690B; CN103702690A

Abstract

An air purifier with electric field regeneration comprises a housing (1) having an air inlet (2) and an air outlet (3), an oxidant generator (4), an adsorbent filter (5), an electric field generator (6) and an air suction unit (7) enclosing by the housing (1). The air suction unit (7) is operable to generate an airflow which draws air contaminants from surrounding into the air purifier with electric field regeneration (4) through the air inlet (2). The oxidant generator (4) is operable to release oxidants; the adsorbent filter (5) is operable to trap the air contaminants and oxidants, so as to efficiently decompose the air contaminants by the oxidants. The electric field generator (6) is operable to generate electric field traversing the adsorbent filter (5), so as to regenerate the adsorbent filter (5). The air purifier is effective in removal of gaseous contaminants, avoids from secondary pollution and makes the adsorbent filter becoming regenerative.

Description

AIR PURIFIER WITH ELECTRIC FIELD REGENERATION

The present invention relates to technical field of air purification, particularly to an air purifier with electric field regeneration.

Background of invention

Indoor air quality is getting more concern because poor air quality is recognized as the cause of human illness such as sick building syndromes. The major indoor air contaminants are air particulates, bacteria, virus and gaseous contaminants like toluene, formaldehyde, MEK, hydrogen sulfide, ammonia. Using air purifier is a common way to improve the indoor air quality. In the market, there are different types of air purification technologies but they have their own drawbacks and problems.

Air purifier with high efficiency particulate air, HEPA filter, composing a mat of randomly arranged fiber can effectively trap the air particulates, bacteria and virus. However, it fails to remove gaseous contaminants.

Air purifier equipping with adsorbent filter like activated carbon is used to adsorb gaseous contaminants. However, it is easily saturated by air contaminants after a period of usage leading to performance degradation. In worst case, it may induce secondary pollution that even creates more serious problem towards human health. Furthermore, the performance of activated carbon is easily affected by high humidity as water molecules can adsorb onto the porous structure of activated carbon leading to competition of adsorption sites with gaseous contaminants. In some cases, thermal regeneration by applying heat on adsorbents is used to desorb both the gaseous contaminants and water molecules but the issue of secondary pollution has not been coped with. Furthermore, installation of heating elements into the adsorbents is always having difficulty in realizing uniform heating. The generated heat will also warm the incoming air. If the environment is air-conditioned, more energy is needed for cooling. It is not favorite towards energy saving.

Some air purifiers release oxidants like ions or ozone for decomposition of gaseous contaminants. Nevertheless, the decomposition rate is so low due to the reaction taking place in gaseous phase that makes both oxidants and air contaminants hardly to meet together. Generation of high concentration of oxidants can be the possible remedy. Nevertheless, oxidants at high concentration can threaten human health.

The objective of this invention is to provide an air purifier with electric field regeneration which can effectively remove air contaminants but without causing secondary pollution.

Summary of Invention

The present invention relates to an air purifier with electric field regeneration which removes gaseous contaminants from indoor air by decomposition into non harmful products and continuously regenerates the adsorbents for further adsorption.

According to one aspect, the air purifier with electric field regeneration according to present invention comprises a housing having an air inlet and an outlet. The housing encloses an oxidant generator, an adsorbent filter, an electric field generator and an air suction unit. The air suction unit is operable to generate an airflow which draws air contaminants from surrounding into the air purifier with electric field regeneration through the air inlet. The oxidant generator is operable to release oxidants. The oxidant generator can be an ion generator, a charged particle generator, an ozone generator, a peroxide generator, a radical generator, a reactive oxidizing gas generator or an electrostatic precipitator. The adsorbent filter is operable to trap the air contaminants and oxidants, so as to efficiently decompose the air contaminants by the oxidants. The electric field generator is operable to generate electric field traversing the adsorbent filter, so as to regenerate the adsorbent filter. The air suction unit can be an exhaust fan, an air suction motor, or the likes, and also can be located at air inlet and/or outlet for airflow generation. The oxidant generator is located in front of the adsorbent filter along the direction of the airflow. The electric field generator is located nearby the adsorbent filter, which generates electric field traversing the adsorbent filter.

The oxidant generator release oxidants, which are mixed with gaseous contaminants along the airflow, and both of them are transferred towards the adsorbent filter. The adsorbents in the adsorbent filter confine both oxidants and gaseous contaminants within their porous structure for achieving decomposition of air contaminants into non-harmful by-products like water molecules and carbon dioxide. Then the electric field generator generates electric field traversing the adsorbents. As the adsorbents are dielectric materials with dielectric constant above 1 and the electric field is oscillating, the charged dipoles are generated and vibrate within the crystalline structure of dielectric materials following the direction of electric field thereby increasing the temperature of the adsorbents. The above dielectric heating effect is able to acquire the desorption of generated by-products like water molecules from their porous structure so that adsorbent saturation from gaseous contaminants and corresponding by-products is avoided making the adsorbent filter become regenerative. The problem raised by high humidity environment is eliminated because water molecules competing the adsorption site with gaseous contaminants can be constantly desorbed out from the porous structure of the adsorbents. On the other hand, the decomposition rate is also increased at this elevated temperature.

The adsorbent filter comprises a porous enclosure and adsorbents, wherein the adsorbents are packed inside the porous enclosure. The porous enclosure comprises a plastic framework and an air permeable layer, wherein the plastic framework gives the shape of the adsorbent filter, and the air permeable layer facing towards the airflow allows either air contaminants or oxidants from the oxidant generator passing into the adsorbents. The adsorbents are dielectric materials with dielectric constant above 1.The pores of adsorbents are incorporated with metal oxide such as titanium oxide, manganese oxide, palladium oxide, cobalt oxide, nickel, zinc oxide or the mixtures of above by wet impregnation. The shape of the adsorbents is spherical, cylindrical, rectangular, irregular or in the form of pellets and granules with a length or a diameter in the range of 1 to 10 mm. The adsorbent filter is in a honeycomb structure made from adsorbent materials with dielectric contact above 1being zeolite, alumina, silica or the mixture of above; the adsorbent materials are doped with metal oxides within their porous structure.

The electric field generator comprises a power supply, a voltage transformer, and electrodes connected in series for generating variable electric fields. Under the presence of electric field, electron-hole pairs are generated on the surface of metal oxide enhancing the production of oxidants such as hydroxyl radicals, charged oxygen molecules, oxygen atoms and ozone from oxygen and water molecules in air. The generated oxidants further decompose the gaseous contaminants within the crystalline structure of the adsorbents. What’s more, the electric field irradiating on the adsorbents can help to speed up the reaction between oxidants and gaseous contaminants since both of them are ionized, depolarized and energized by the electric field. In the present invention, the adsorbents are well chosen for effectively confining and removing the excess oxidants for avoiding leakage.

The electrodes can be located on surfaces of the adsorbents filter perpendicular to the direction of the airflow and the electrodes are in a net structure so that the airflow can pass through the electrodes freely without reduction. The electrodes also can be located on the lateral sides of the adsorbent filter parallel to the direction of the airflow. Otherwise, one of the electrodes can be in cylindrical shape whereas another electrode can be a wire, and the adsorbent filter is also in cylindrical shape and situated in between the electrodes.

In additional, a layer of protection coating is applied on surfaces of the electrodes for avoiding corrosion from humidity and generated oxidants. A particulate filter can be located in between the oxidant generator and the adsorbent filter serving for particulate and bacteria removal.

As a whole, the present invention provides air purifier with electric field regeneration, which is effective in removal of gaseous contaminants, avoids from secondary pollution and makes the adsorbent filter becoming regenerative.

Brief Description of the Drawings

So as to further explain the invention, an exemplary embodiment of an air purifier according to the invention will be described with reference to the below drawings, wherein:

Fig. 1 is a schematic diagram of the air purifier of the present invention;

Fig. 2 is a schematic diagram of the adsorbent filter;

Fig. 3 is a schematic diagram of the adsorbent filter in honeycomb structure;

Fig. 4 is a schematic diagram of the electric field generator;

Fig.5 is a schematic diagram showing one of the electrode position arrangements, in which the electrodes are located on the surface of the adsorbent filter;

Fig. 6 is a schematic diagram showing one of the electrode position arrangements, in which the electrodes are located at the lateral sides of the adsorbent filter;

Fig. 7 is a schematic diagram showing one of the electrode position arrangements, in which one of the electrodes encloses the adsorbent filter in cylindrical shape;

Fig. 8 is a schematic diagram showing one of the electrode position arrangements, in which the electrodes are located at the lateral sides of the adsorbent filter in honeycomb structure;

Fig. 9 is a schematic diagram of the air purifier of the present invention including a particulate filter.

Detailed Description of the Preferred Embodiments

These and other advantage, aspect and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understand from the following description and drawings. While various embodiments of the present invention has been presented by way of example only, and not limitation.

Fig. 1 is the schematic diagram of the air purifier of the present invention. The air purifier comprises a housing 1 having an air inlet 2 and an air outlet 3. The housing 1 encloses an oxidant generator 4, an adsorbent filter 5, an electric field generator 6, and an exhaust fan 7. The exhaust fan 7 being located at the air inlet 2 or air outlet 3, generates an airflow, which draws the air contaminants from the surrounding into the air purifier through the air inlet 2. In other embodiment of present invention, the exhaust fan 7 also can be an air suction motor, an air pump or the likes. The oxidant generator 4 is located in front of the adsorbent filter 5 along the airflow and responsible for releasing oxidants. Along the airflow, the released oxidants firstly mix with air contaminants and both of them are then transferred towards the adsorbent filter 5. The adsorbents 9 of the adsorbent filter 5 are effective in trapping them within their crystalline structure. As both adsorbed oxidants and gaseous contaminants are confined within the space in nanometer scale, gaseous contaminants are efficiently decomposed by oxidants into non-harmful products like water molecules and carbon dioxide. The electric field generator 6 is located nearby the adsorbent filter 5 and generates electric field traversing the adsorbents 9. As the adsorbents 9 in the present invention is dielectric materials like zeolite, dielectric heating of adsorbents 9 is attained due to the presence of oscillating electric field. Once the temperature of the adsorbents 9 arises, the by-products will be desorbed out from the crystalline structure freeing the adsorption site for further adsorption of incoming gaseous contaminants. Finally, clean air is released from the air outlet 3.

The oxidant generator 4 located in front of the adsorbent filter 5 releases oxidants for decomposition of gaseous contaminants. The oxidant generator 4 can be ion generator, charged particle generator, ozone generator, peroxide generator, radical generator (such as hydroxyl radical generator), reactive oxidizing gas generator or electrostatic precipitator. Thus, the oxidants can be cation, anion, charged particles, ozone, peroxide, radicals (such as hydroxyl radical), or any other reactive oxidizing gases, which are reactive enough to decompose gaseous contaminants. The oxidants can be generated by electrical method such as electrostatic precipitator and corona discharge, chemical method and photolytic method such as UV. Excessive oxidants are easily confined and decomposed by the adsorbent for avoiding leakage. The choice and amount of oxidants are determined by the nature and amount of air contaminants, one skilled in the art may choose appropriate species and amount of oxidants based on the polluted environment.

As shown in Fig. 2, the adsorbent filter 5 comprises a porous enclosure 8 and adsorbents 9, where the adsorbents 9 are packed inside the porous enclosure 8. The shape of the adsorbent filter 6 can be rectangular, cylindrical, cubic or any kind of shape depending on the application. The porous enclosure 8 comprises a plastic framework 10 and an air permeable layer 11. The plastic framework 10 giving the shape of the adsorbent filter 5 is made from insulating plastic materials, like polyester, polypropylene, polystyrene, polycarbonates. The air permeable layer 11 facing towards the airflow allows either air contaminants or oxidants passing into the adsorbents 9. The materials of the air permeable layer 11 can be cloth or plastic net, which are insulating. The mesh size of the air permeable layer 11 has to be small enough to prevent the fall-off of the adsorbents 9. The shape of the adsorbents 9 can be spherical, cylindrical, rectangular, irregular or in the form of pellets and granules with length or diameter in the range of 1 to 10 mm. Powder can be used as adsorbents 9 in the present invention and mesh size should be in microscale. The adsorbents 9, being dielectric materials with dielectric constant larger than 1, can be zeolite, alumina and silica and the likes. As the adsorbents 9 are insulating materials, they will not conduct electricity when applying voltage on them. What’s more, the possibility of electric breakdown within the adsorbent filter 5 is highly reduced even applying high voltage. Certain range of pore size of adsorbents 9 is chosen for achieving good confinement of both gaseous contaminants and oxidants within their crystalline structure. As both gaseous contaminants and oxidants are held together within the crystalline structure in nanometer scale, they will then react with each other thereby decomposing the gaseous contaminants into non-harmful products like carbon dioxide and water molecules. Both hydrophilic and hydrophobic absorbents 9 are used and formulated so as to acquire efficient adsorption of both polar and non-polar gaseous contaminants. Metal oxides such as titanium oxide, manganese oxide, palladium oxide, cobalt oxide, nickel, zinc oxide or the mixtures of above are incorporated into the crystalline structure acting as catalyst for enhancing the decomposition of gaseous contaminants by oxidants. Apart from that, as the metal oxides are semiconducting materials, electron-hole pairs are generated on their surface under the presence of electric field thereby making the metal oxide surface to be more reactive for achieving oxidant generation within the crystalline structures such as hydroxyl radical, peroxide, ionized oxygen and ozone from oxygen and water. The newly generated oxidants are able to further oxidize the gaseous contaminants trapped within the porous structure. The adsorbents 9 can also confine and decompose the excess oxidants for avoiding leakage.

The adsorbent filter 5 can also be in honeycomb structure as shown in Fig. 3, which is also made from the same adsorbent materials such as zeolite, alumina and silica and the likes by any methods like injection molding. The adsorbent materials are also doped with metal oxides as mentioned above. The adsorbent filter 5 in honeycomb structure located within the housing 1 can be rectangular or cylindrical in shape. It gives the benefit in low-pressure drop while still keeping high adsorption surface area. Airflow from the air inlet 2 will pass through the holes of the adsorbent filter 5 in honeycomb structure, wherein both gaseous contaminants and oxidants are adsorbed on the walls of the holes for achieving catalytic oxidation within the porous structure of adsorbent materials.

Fig. 4 shows the schematic diagram of the electric field generator 6. The electric field generator 6 of the present invention located nearby the adsorbent filter comprises a power supply 13, a transformer 14 and electrodes 15 connected in series. There are several possibilities in position arrangement of electrodes 15. Some of the possibilities are indicated in the following Figures. However, one skilled in the art knows that, besides the disclosed position arrangements and shapes, the electrodes 15 also can be arranged and shaped in other proper forms without reduction of airflow.

Fig. 5 indicates that the electrodes 15 are located on the surface of the adsorbents filter 5 perpendicular to the direction of the airflow. The electrodes 15 are in net structure so that airflow can pass through electrodes 15 freely without reduction of airflow. In other possible embodiment, the electrodes 15 also can be in stick, wire, or other suitable structure that will not deteriorate the airflow.

Fig. 6 shows that the electrodes 15 are arranged on the lateral sides of the adsorbent filter 5 parallel to the direction of the airflow. As it will not affect the airflow, the electrodes 15 can be in plate, net, stick, wire, or other suitable structure.

Fig. 7 shows another arrangement that one of the electrodes 15 is in cylindrical shape whereas another electrode 15 is a wire. The adsorbent filter is also in cylindrical shape and situated in between the electrodes 15.

Fig. 8 indicates that the electrodes are located on the lateral side of the adsorbent filter 5 parallel to the direction of the airflow. The adsorbent filter 5 is in a honeycomb structure. In such embodiment, as it will not affect the airflow, the electrodes 15 can be in plate, net, stick, wire, or other suitable structure.

The materials of the electrodes 15 can be iron, steel, aluminum and tungsten, which possess good electrical conductivity. A layer of protection coating like epoxy can be applied on the surface of the electrodes 15 for avoiding corrosion from the humidity and generated oxidants. Electric field generation is achieved by the power supply 13 and voltage transformer 14. The frequency of the system can be varied and normally in sinusoidal waveform, where the range of frequency is 0.5-5kHz. AC sinusoidal voltage is more preferred since oscillating voltage highly enhances the effect of dielectric heating and generation of oxidants. However, DC voltage can also be applied that gives less electromagnetic interference towards the peripheral electronics. The applied voltage can be in the range of 0.1 to 10kV, which is strong enough in inducing heating effect on the adsorbents 9. As the by-products created by the decomposition of gaseous contaminants are water molecules and carbon dioxide, the dielectric heating is capable of increasing the desoprtion rate of the by-products from pores of adsorbents 9 for achieving thermal regeneration. At high humidity environment, water molecules from the incoming air will compete the adsorption sites with gaseous contaminants. The thermal regeneration by electric field can reduce this undesirable effect from moisture thus enhancing the adsorption capacity of gaseous contaminants. According to the experimental result, most water molecules will be desorbed out from the pores when the temperature rises to 80℃ to 120℃.

The presence of electric field also enhances the decomposition rate of gaseous contaminants because the gaseous contaminants are ionized, depolarized and energized under the irradiation of electric field making them to be more reactive in reaction of generated oxidants. As there is incorporation of metal oxides within the porous structure of adsorbents, electron-hole pairs are generated on the surface of metal oxides under the irradiation of electric field, thereby speeding up the decomposition rate due to this catalytic effect. Apart from that, the generated electron-hole pairs assist in creation of oxidants such as hydroxyl radicals, charged oxygen molecules, oxygen atoms and ozone from oxygen and water molecules within the porous structure of adsorbents 9 for further decomposition of confined air contaminants. Furthermore, unlike the traditional oxidant generation by corona discharge in air, the threshold voltage in oxidant generation can be highly reduced due to the presence of metal oxides. In general, there are two modes of operation. The first one is to keep continuous generation of electric field during the operation of the air purifier while another one is to generate electric field only at certain period. The advantage of the first operation mode is that the electric field can continuously regenerate the adsorbents 9 by thermal method and produce more oxidants so that it will get the benefit in attaining high air purification efficiency. However, as it keeps warming the adsorbents 9, the treated air is warmed, too. It induces undesirable effects towards air-conditioned environment since more electricity is needed for cooling down the air. As electric field is generated only at certain period, the effect of above drawback can be highly reduced. Thus, the choice in the above two modes will depend on application environment.

In other embodiment of the present invention as shown in Fig. 9, the particulate filter 16 can be located in between the oxidant generator and the adsorbent filter serving for particulate and bacteria removal. As oxidants released from the oxidant generator will pass through the particulate filter, the trapped bacteria and virus will be inactivated. What’s more, the presence of the particulate filter 16 can also protect the adsorbent filter 5 from particulate contamination of the adsorbents 9.

The foregoing description is just the preferred embodiment of the invention. It is not intended to exhaustive or to limit the invention. Any modifications, variations, and amelioration without departing from the spirit and scope of the present invention should be included in the scope of the prevent invention.

Claims

1. An air purifier with electric field regeneration, wherein, comprising:

a housing having an air inlet and an air outlet;

an oxidant generator, an adsorbent filter, an electric field generator and an air suction unit enclosed by the housing;

the air suction unit is operable to generate an airflow which draws air contaminants from surrounding into the air purifier with electric field regeneration through the air inlet;

the oxidant generator is operable to release oxidants;

the adsorbent filter is operable to trap the air contaminants and oxidants, so as to efficiently decompose the air contaminants by the oxidants;

the electric field generator is operable to generate electric field traversing the adsorbent filter, so as to regenerate the adsorbent filter.

2. The air purifier with electric field regeneration according to claim 1, wherein, the oxidant generator is located in front of the adsorbent filter along the direction of the airflow, the electric field generator is located nearby the adsorbent filter, and the air suction unit is located at the air inlet and/or the air outlet.

3. The air purifier with electric field regeneration according to claim 1, wherein, the oxidant generator is an ion generator, a charged particle generator, an ozone generator, a peroxide generator, a radical generator, a reactive oxidizing gas generator or an electrostatic precipitator.

4. The air purifier with electric field regeneration according to claim 1, wherein, the adsorbent filter comprises of a porous enclosure and adsorbents, wherein the adsorbents are packed inside the porous enclosure.

5. The air purifier with electric field regeneration according to claim 4, wherein, the porous enclosure comprises of a plastic framework and an air permeable layer, the plastic framework gives the shape of the adsorbent filter, and the air permeable layer facing towards the airflow allows either the air contaminants or the oxidants passing into the adsorbents.

6. The air purifier with electric field regeneration according to claim 4, wherein, the adsorbents being dielectric materials with dielectric constant above 1, are zeolite, alumina, silica or the mixture of above; and the shape of the adsorbents is spherical, cylindrical, rectangular, irregular or in the form of pellets and granules with a length or a diameter in the range of 1 to 10 mm; and the adsorbents are incorporated with metal oxides within their porous structure.

7. The air purifier with electric field regeneration according to claim 1, wherein, the adsorbent filter is in a honeycomb structure made from adsorbent materials with dielectric contact above 1 being zeolite, alumina, silica or the mixture of above; the adsorbent materials are doped with metal oxides within their porous structure.

8. The air purifier with electric field regeneration according to any one of claims 1-7, wherein, the electric field generator comprises a power supply, a voltage transformer, and electrodes connected in series for generating variable electric fields; and the variable electric field generated from the electric field generator induces dielectric heating on the adsorbents for thermal regeneration.

9. The air purifier with electric field regeneration according to claim 8, wherein, the metal oxides irradiated by the variable electric field enhance the oxidant generation within the porous structure of adsorbents for decomposition of the confined air contaminants.

10. The air purifier with electric field regeneration according to claim 8, wherein, the electrodes are located on surfaces of the adsorbents filter perpendicular to the direction of the airflow.

11. The air purifier with electric field regeneration according to claim 8, wherein, the electrodes are located on the lateral sides of the adsorbent filter parallel to the direction of the airflow.

12. The air purifier with electric field regeneration according to claim 8, wherein, one of the electrodes is in cylindrical shape whereas another electrode is a wire, and the adsorbent filter is also in cylindrical shape and situated in between the electrodes.

13. The air purifier with electric field regeneration according to claim 8, wherein, a layer of protection coating is applied on surfaces of the electrodes for avoiding corrosion from humidity and generated oxidants.

14. The air purifier with electric field regeneration according to claim 1, wherein, a particulate filter is located in between the oxidant generator and the adsorbent filter serving for particulate and bacteria removal.

15. The air purifier with electric field regeneration according to claim 1, wherein, the air suction unit is an exhaust fan, an air suction motor, or an air pump.