WO2010108328A1

WO2010108328A1 - Rejuvenated foam support filter

Info

Publication number: WO2010108328A1
Application number: PCT/CN2009/071036
Authority: WO
Inventors: Chi Keung Rudy Chan; Yee Lam Chan; Lam Lung Yeung; Ka Tung Ho
Original assignee: Rht Limited
Priority date: 2009-03-27
Filing date: 2009-03-27
Publication date: 2010-09-30

Abstract

An air cleaning apparatus (1) for removing air contaminants and bacteria includes a foam support filter (5) which includes foam (8) affixed with adsorbent particles (9) thereby providing an open pore foam structure The air resistance and air contaminants removal efficiency are easily and effectively adjusted by the percentage of particles (9) filling in foam volume Since air contaminants adsorbed on the filter (5) will be oxidized by reactive oxidizing species into non-harmful products like water molecules and carbon dioxide, the air cleaning apparatus (1) will not cause secondary pollution and the filter (5) is rejuvenated and semi-permanent.

Description

Rejuvenated Foam Support Filter

FIELD OF THE INVENTION

[1] The present invention relates to air cleaning, more particularly, to an air cleaning apparatus for removing air contaminants and bacteria. BACKGROUND OF THE INVENTION

[2] Currently, people are concerned more about indoor air quality because it is recognized as the cause of human health hazard. Air contaminants such as volatile organic compounds, ammonia, hydrogen sulfide, bacteria and virus are well known to threaten human health. There are various technologies such as activated carbon absorbent filter, photo-catalytic decomposition and oxidation with reactive oxidizing species to solve these problems but they still have their limitations.

[3] Disclosed by U.S. Pat. No. 5,678,576 and 6,835,237, activated carbon pellets packed inside a cartridge is commonly used as an adsorbent filter in air cleaner. Nevertheless, the adsorbent pellets become saturated by air contaminants after period of time that reduces its removal effectiveness and eventually causes secondary pollution. Apart from it, this tightly-packed and bulky structure has high flow resistance and induces heavy loading towards the air delivery system. What's more, under this packing structure, the pellets are always in contact with others thereby reducing effective adsorption area.

[4] U.S. Pat. No. 5,656,063 teaches that reactive oxidizing species (ROS) such as ions, ozone, radicals or any oxidizing gases are applicable to decompose air contaminants. However, the ROS at low concentration is not effective in decomposition and generate intermediate products instead, which may be more harmful towards human health. On the contrary, once high concentration is used, the excessive ROS may be released out from the air cleaning apparatus and pollute the environment.

[5] Disclosed by U.S. Applied Pat. No. 20030140794 and 20040089154, foam coated with adsorbent powders is used as filter with low flow resistance. Nevertheless, its removal efficiency is low at high air flow rate since the open pore foam structure is not efficient to retain and trap air contaminants. Similar to aforementioned bulk adsorbent filter, the adsorbent materials are easily saturated by air contaminants.

[6] The objective of this invention is to provide an air cleaning apparatus with a low air-resistant and rejuvenated filter, which can effectively remove air contaminants but without causing secondary pollution. SUMMARY OF THE INVENTION

[7] The present invention has the principal objective of providing an air cleaning apparatus for the removal of air contaminants and bacteria in domestic, commercial or industrial areas.

[8] The present invention comprises a housing having an air inlet and an air outlet. The housing encloses a foam support filter and ROS generator. In some cases, air delivery unit can be installed in the housing for air flow generation.

[9] The foam support filter of present invention comprises a foam, adsorbent particles, covering layers and frame. The foam provides a 3 dimensional network with open pores and the adsorbent particles suspend whereon. This open pores foam structure increases the effective adsorption surface area of air contaminants but decreases air resistance to achieve high circulation rate. Under air flow, this open pore foam structure can induce air turbulence which extends the mean free path of air contaminants within the filter and thus enhances the adsorption efficiency.

[10] Thanks to the elasticity of foam, the filter is less fragile and can be easily manufactured into different shapes. Comparing with conventional bulk filter, less adsorbent particles are consumed in the present invention while still providing even distribution and arrangement of adsorbent particles.

[11] The present invention provides a rejuvenation system, in which the air contaminants and ROS are confined in the micro/nanopores of adsorbent materials. Unlike the gaseous phase reaction, they are held closely with each other (in the range of nanometer scale), thereby enhancing the efficiency of the ROS in decomposing air contaminants into non-harmful product such as water and carbon dioxide. Since the oxidized products are too small to be retained inside the pores, they will diffuse out from the pores for further adsorption of air contaminants.

[12] In the present invention, the adsorbent materials of the filter are designed, chosen and engineered for having high capability of retaining both oxidants and air contaminants in order to increase the decomposition rate of air contaminants and avoid the release of excessive oxidants from the air cleaning apparatus.

[13] Comparing with conventional adsorbent filter, the foam support filter of present invention is light, less fragile and flexible but effective in removal of air contaminants with low air resistance. The air resistance and air contaminant removal efficiency are easily and effectively adjusted by the percentage of particles filling in foam volume. Since air contaminants adsorbed on the filter will be oxidized by reactive oxidizing species into non-harmful products like water molecules and carbon dioxide, the technology of present invention will not cause secondary pollution and the filter is rejuvenated and semi permanent. BRIEF DESCRIPTION OF THE DRAWINGS

[14] So as to further explain the invention, an exemplary embodiment of an air cleaning apparatus according to the invention will be described with reference to the below drawings, wherein:

[15] FIG. 1 schematically shows an air cleaning apparatus according to the invention;

[16] FIG. 2 schematically shows a foam support filter according to the invention;

[17] FIG. 3 schematically shows a cross section of the foam support filter according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[18] 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.

[19] FIG. 1 shows one possible embodiment of the invention. The air cleaning apparatus 1 comprises a housing 2 having an air inlet 3 and an air outlet 4. The housing 2 is continuous between the air inlet 3 and outlet 4 so that air is unable to enter or leave the housing except at the inlet 3 and outlet 4. The foam support filter 5 is located inside the housing 2 where all air must pass through the filter 5. Along the moving direction of airflow, the ROS generator 6 is placed in front of the foam support filter 5 so that the ROS are transported by the air stream thereto. An air delivery unit 7 can be installed inside the housing 2 to generate airflow.

[20] FIG. 2 shows the structure of the foam support filter 5, which comprises foam 8, adsorbent particles 9, covering layers 10 and framework 11. As illustrated by FIG. 3, the adsorbent particles 9 are affixed inside the open pores of the foam network. The size of adsorbent particles 9 is merely smaller than the pore size of foam 7, and thereby the adsorbent particles 9 can be incorporated into the network as well as affixed firmly whereon without any adhesive materials which block the adsorption surface area. Comparing with bulk filter, the adsorbent particles 9 are suspended individually in the open pore foam network providing less contact area among adsorbent particles 9 but increasing the net adsorption surface area. The adsorption surface area and air permeability of the filter 5 are determined by the size of adsorbent particles 9 and percentage of particle filling in the foam volume. After the incorporation of adsorbent particles 9, the foam 8 is covered by covering layers 10 to avoid the falling-out of the particles 9. The shape of the filter 5 is formed and supported by the framework 11. The framework 11 has at least one inlet and outlet for air passing through the foam and adsorbent particles.

[21] The foam 8 can be made from poly ethylenes, polyurethanes polyesters, polyacrylates, polyurea, poly amides and polydiene block polymer. The foam 8 has reticulated structure and open pores therein with a range of diameter. The foam 8 is elastic and can be compressed or extended, and then resumed to the original shape thereby providing the ease of incorporation of particles 9. However, after the incorporation of particles 9 into the open pores, the filter becomes rigid. This open pore foam structure and elastic feature make the filter 5 become more resistant to shock and easier to be manufactured in different shapes. In the present invention, the pore size of the foam 8 is in the range of 3 ppi to 50 ppi. The foam 8 thickness can be from 5 mm to 50 mm. The foam 8 can be coated with adsorbents in either granules or powders in order to increase the adsorption surface area for both air contaminants and oxidants. [22] The shape of the adsorbent particles 9 can be spherical, cylindrical, rectangular, irregular or in the form of pellet or granule. The size of adsorbent particles 9 is in the range of 1 to 10 mm. The adsorbent materials can be activated carbon, zeolite, metal oxide framework, alumina, silica or in mixture of the aforementioned adsorbent materials. The adsorption capacity of the materials depends on micro/nanopore size, shape, orientation of crystal structure, chemical nature, hydrophobicity and hydrophilicity. It was known that air contaminants commonly found in domestic, commercial and industrial areas are with size between 4 to 20 Angstrom so that the pore size of the adsorbent materials is tuned in the range of 4 to 20 Angstrom for effective adsorption. When the micro/nanopore size is too small, air contaminants are too big to penetrate into the micro/nanopores. On the contrary, when the micro/nanopore size is too big, air contaminants are too small to be confined inside the micro/nanopores. The property of the adsorbent materials can either be hydrophobic or hydrophilic or in physical mixture of both. The hydrophobic materials are used for adsorption of non-polar air contaminants such as aromatic and aliphatic hydrocarbons. The hydrophilic materials are mainly for adsorption of polar air contaminants including hydrogen sulfide, ammonia, aldehyde and alkanol. Mixtures of both hydrophilic and hydrophobic materials can also be used for the enhancement of adsorption capacity. Transition metals can be incorporated into the porous structure of the adsorbent materials so as to enhance the oxidation rate of air contaminants thanks to their catalytic properties. In summary, the adsorbent materials in the present invention can be designed, chosen and engineered according to the nature of air contaminants and oxidants.

[23] In the FIG. 2, the covering layers 10 are attached on the surfaces of the foam 8 by adhesive and any mechanical methods. The covering layers 10 can be plastic net, metal net, cloth and foam layer. The pore size of the covering layers 10 is smaller than that of the foam 8 for avoiding falling-out of adsorbent particles 9. The covering layers 10 can be coated with adsorbents in either granules or powders in order to enhance the adsorption capacity. What's more, air particle filter such as High Efficiency Particulate Air filter (short for HEPA) can be served as covering layers 10 with advantages in removing air particles along the air flow and avoid the contamination of adsorbent particles 9. The framework 11 forms the shape and provides mechanical support to the filter 5. The materials of framework 11 can be metal, paper, wood or plastic.

[24] In other embodiment (FIG. 1), the ROS generator 6 is placed in front of the foam support filter 5 along the air flow direction. The generated ROS are actively transferred by the airflow towards the foam support filter 5 for the decomposition of air contaminants. The ROS generator 6 can be ion generator, radical generator such as hydroxyl radical, ozone generator, reactive oxidizing gas generator. The ROS can be cation, anion, charged particles, ozone, radicals, or any other reactive oxidizing gases. ROS can be generated by electrical method such as electrostatic precipitator and corona discharge, chemical and photolytic method such as UV. ROS are easily confined and decomposed within the filter 5 for avoiding the leakage of excess ROS. The choice and amount of ROS are determined by the nature and amount of air contaminants.

[25] In other embodiment (FIG. 1), comparing with bulk filter, the open pore foam structure of the filter 5 has lower air resistance which can relieve the loading, power and noise level of the air delivery unit, as well as achieve high air circulation rate. In the presence of air flow, the open pore foam structure of the filter 5 is able to create turbulent flow within the filter 5 that extends the mean free path of air contaminants within the filter, and thus enhances the adsorption efficiency. The percentage of particle filling in foam volume determines the air resistance and net adsorption surface area of the filter 5. The percentage of particle filling can be varied in between 20 to 80%. When higher the percentage of particle filling is, higher the air resistance and adsorption surface area will be, and vice versa. Hence adjusting the percentage of particle filling is a convenient and effective way to maximize the overall performance of the air cleaning apparatus with respect to applications. Under same type and amount of adsorbent materials, this dispersive filter layer of the present invention has larger volume than bulk filter but lower air resistance. For example with a 1000 cm³ volume, only 500g adsorbent particles 9 are needed instead of lOOOg at bulky packing structure thereby reducing the weight and production cost of the filter 5.

[26] Apart form the adsorbent particles 9, the foam 8 and covering layers 10 are recommended to be coated with adsorbents either in granules or powders to provide larger adsorption surface area for both air contaminants and oxidants thereby enhancing the decomposition rate of air contaminants and avoiding the leakage of excessive ROS in the present invention.

[27] Being more versatile in application, the filter 5 can comprise several foam layers 10, each with specific compositions in removing specific air contaminants. The aforementioned foam layers 8 can be tailor made in different thickness, pore sizes together with different types and amount of adsorbent particles 9. Then, the foam layers 10 are attached with each other by adhesive or any mechanical methods, followed by assembling inside the framework 11. For example, the first foam layer 10 is for removal of volatile organic compound such as acetone and ethyl benzene while the second layer 10 is for removal of inorganic compound such as ammonia and hydrogen sulfide.

[28] 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] 1. An air cleaning apparatus for removing air contaminants and bacteria, which comprising a housing having an air inlet and an air outlet; wherein the housing encloses a foam support filter and a reactive oxidizing species generator, the

ROS generator is placed in front of the foam support filter along the air flow direction. [2] 2. The air cleaning apparatus according to claim 1, wherein an air delivery unit is installed inside the housing for air flow generation. [3] 3. The air cleaning apparatus according to claim 1, wherein the ROS generated by the ROS generators are transferred into the foam support filter by air flow. [4] 4. The air cleaning apparatus according to claim 1, wherein the foam support filter comprises a foam, adsorbent particles, covering layers and a framework, the foam is incorporated with the adsorbent particles, and the covering layers are used to cover the foam to avoid the falling-out of the adsorbent particles, the framework is used to support the foam. [5] 5. The air cleaning apparatus according to claim 4, wherein the framework has at least one inlet and outlet for air passing through the foam and adsorbent particles. [6] 6. The air cleaning apparatus according to claim 4, wherein the foam has open pores in 3 dimensional network. [7] 7. The air cleaning apparatus according to claim 4, the adsorbent particles are affixed inside the open pores of the foam network. [8] 8. The air cleaning apparatus according to claim 7, wherein the pore size of foam is merely larger than the size of adsorbent particles. [9] 9. The air cleaning apparatus according to claim 8, wherein the pore size of foam is in the range of 3-50 ppi. [10] 10. The air cleaning apparatus according to claim 8, wherein the materials of the foam is elastic, so the adsorbent particles are affixed firmly inside the foam network. [11] The air cleaning apparatus according to claim 10, wherein the materials of foam are poly ethylenes, polyurethanes polyesters, polyacrylates, polyurea, poly amides and/or polydiene block polymer. [12] The air cleaning apparatus according to claim 6, wherein the foam is coated with adsorbents in either granules or powders. [13] The air cleaning apparatus according to claim 12, wherein the coating materials are activated carbon, zeolite, metal oxide framework, alumina, silica or in mixture of the aforementioned adsorbent materials. [14] The air cleaning apparatus according to claim 4, wherein the shape of the adsorbent particles is spherical, cylindrical, rectangular, irregular or in the form of pellet or granule. [15] The air cleaning apparatus according to claim 14, wherein the materials of adsorbent particles are activated carbon, zeolite, metal oxide framework, alumina, silica or in mixture of the aforementioned adsorbent materials. [16] The air cleaning apparatus according to claim 15, wherein the size of adsorbent particles is in the range of 1 to 10 mm. [17] The air cleaning apparatus according to claim 15, the micro/nanopores of the adsorbent material is in the range of 4 to 20 Angstrom. [18] The air cleaning apparatus according to claim 15, the adsorbent materials can be hydrophobic, hydrophilic or in a mixture of both. [19] The air cleaning apparatus according to claim 17, wherein transition metals are incorporated into the porous structure of the adsorbent materials. [20] The air cleaning apparatus according to claim 4, wherein the covering layers are attached on the foam by either adhesive or mechanical methods. [21] The air cleaning apparatus according to claim 20, wherein the covering layers are plastic net, metal net, cloth or foam layer. [22] The air cleaning apparatus according to claim 9 or 21, wherein the pore size of covering layer is smaller than that of the foam. [23] The air cleaning apparatus according to claim 21, wherein the covering layers are

HEPA filters serving to remove air particles. [24] The air cleaning apparatus according to claim 21, wherein the covering layers are coated with adsorbents in either granules or powders. [25] The air cleaning apparatus according to claim 4, wherein the materials of framework are metal, paper, wood or plastic. [26] The air cleaning apparatus according to claim 4, wherein the foam support filter further comprises several foam layers, each with specific compositions in removing specific air contaminants. [27] The air cleaning apparatus according to claim 4, the foam layers are tailor made in different thickness, pore sizes together with different types and amount of adsorbent particles. [28] The air cleaning apparatus according to claim 26 or 27, wherein the foam layers are attached with each other by adhesive or mechanical method and followed by assembling inside the framework. [29] The air cleaning apparatus according to claim 1, wherein the ROS is cation, anion, charged particles, ozone or radicals. [30] The air cleaning apparatus according to claim 29, wherein the ROS generator includes an ion generator, ozone generator, radical generator or reactive oxidizing gas generator. [31] The air cleaning apparatus according to claim 30, wherein the radical generator generates hydroxyl radical. [32] The air cleaning apparatus according to claim 30, wherein the ROS are generated by electrical, chemical or photolytic method. [33] The air cleaning apparatus according to claim 32, wherein the choice and amount of generated ROS are determined by the nature and amount of air contaminants. [34] The air cleaning apparatus according to claim 7, wherein the adsorbent particles are suspended individually in the open pore foam network providing less contact area among adsorbent particles but increasing the net adsorption surface area. [35] The air cleaning apparatus according to claim 7, wherein the suspension of adsorbent particles within the open pore foam structure can provide even distribution and arrangement of particles. [36] The air cleaning apparatus according to claim 7, wherein the open pore foam structure with suspension of particles reduce the air resistance of the foam support filter. [37] The air cleaning apparatus according to claim 7, wherein the air resistance of the foam support filter is fine-tuned by the size of adsorbent particles and percentage of particles filling in the foam volume. [38] The air cleaning apparatus according to claim 7, wherein the adsorption surface area of the foam support filter is fine-tuned by the size of adsorbent particles and the percentage of particles filling in the foam volume. [39] The air cleaning apparatus according to claim 7, wherein the suspension of particles within the open pore foam structure create turbulent flow, which extends the mean free path of air contaminants within the foam support filter and thus enhances the adsorption efficiency. [40] The air cleaning apparatus according to claim 17, wherein both air contaminants and ROS are confined inside the micro/nanopores of the adsorbent materials. [41] The air cleaning apparatus according to one of claim 40, wherein the ROS decompose the confined air contaminants into non-harmful products. [42] The air cleaning apparatus according to claim 41, wherein the micro/nanopores of the adsorbent materials are rejuvenated by the ROS for further adsorption. [43] The air cleaning apparatus according to claim 40, wherein the adsorbent materials trap and decompose excessive ROS.