HK1118245B - Gas treatment adsorption-oxidation system - Google Patents

Description

Gas treatment adsorption-oxidation system

Background

The present invention relates to air treatment modules, and more particularly, to air treatment modules having two gas purifiers that cooperate to control the concentration of contaminants in an output gas stream from the air treatment module.

Air treatment modules are commonly used in automotive, industrial, and residential heating, ventilation, and air conditioning (HVAC) systems to purify a circulating air stream. Typical air treatment modules utilize an air purifier to remove contaminants, such as Volatile Organic Compounds (VOCs), from a circulating air stream. For example, an air purifier typically includes one of a filter, an adsorbent media, a photocatalyst, a plasma reactor, or other means of removing, treating, purifying, or chemically converting contaminants.

As the inventors have experimentally discovered, known air purifiers may not be able to adequately control the VOC concentration in the recycle gas stream when the VOC concentration entering the air purifier is temporarily higher than the normal VOC concentration. Temporarily excessive VOC concentrations may occur, for example, when certain foods or beverages are present, when alcohol-based handkerchiefs are used, or when VOC-containing products are spilled out.

Known air purifiers are capable of removing or treating normal VOC concentration levels (i.e., without excess food or beverage, when using alcohol-free or low alcohol-based handkerchiefs and without spillage) and may not completely treat a circulating air stream with an extraordinary VOC concentration. For example, the adsorbent media cannot adsorb VOC fast enough to keep up with the source rate of the VOC. Also, the photocatalyst may not be able to capture and chemically convert the VOC completely quickly enough to keep up with the source rate of the VOC. Thus, the VOC may remain in the recycle gas stream at an excessive VOC concentration or may be converted to an intermediate VOC product that is also undesirable. The VOC and/or intermediate VOC products may then continue to produce odor or other undesirable conditions in the recycle gas stream.

It has been proposed to design larger capacity air purifiers, such as adsorbent media with additional adsorption sites or photocatalysts that can capture and treat VOCs more quickly, however these designs can require a substantial increase in the size and expense of the air purifier.

It is desirable to design and develop an air treatment module that more effectively and economically controls the concentration of contaminants in the circulating gas stream when the VOC concentration is excessive.

Summary of The Invention

The gas treatment module includes a first gas purifier and a second gas purifier that cooperate to control the concentration of contaminants in the output portion of the gas stream when the concentration of contaminants in the input portion of the gas stream is temporarily equal to or greater than a threshold concentration. In one embodiment, the first gas purifier and the second gas purifier maintain a concentration of the contaminant in the output portion within a selected concentration range, but each of the first gas purifier or the second gas purifier alone cannot maintain the concentration within the selected concentration range.

Another embodiment includes an adsorbent media that adsorbs and desorbs contaminants in a gas stream according to the concentration of the contaminants in the gas stream. The adsorbent media primarily adsorbs contaminants when the concentration is greater than or equal to the threshold concentration. When the concentration is below the threshold concentration, the adsorbent media primarily desorbs contaminants into the gas stream output or the photocatalyst.

An exemplary method of gas treatment includes controlling a concentration of a contaminant in an output portion of a gas stream when the concentration of the contaminant in the input portion of the gas stream temporarily exceeds a threshold concentration.

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view of an exemplary structure including a heating, ventilation, and air conditioning system.

FIG. 2 is a schematic cross-sectional view of an exemplary air treatment module.

Fig. 3 is a cross-sectional view of an exemplary adsorbent media bed and photocatalyst.

FIG. 4 is a schematic cross-sectional view of another exemplary air treatment module.

FIG. 5 is a perspective view of an exemplary integrated gas purifier.

Detailed description of the preferred embodiments

Fig. 1 illustrates a structure 10, such as a residential, industrial, or vehicular structure, that includes an interior space 12, such as a room, office, or vehicle cabin. A heating, ventilation, and air conditioning (HVAC) system 14 selectively heats or cools the interior space 12 based on a signal input to the HVAC system 14 by a user. An air moving unit 15 (e.g., a fan, blower and/or compressor) moves air from the interior space 12 of the structure 10 into the HVAC system 14 via an input path 16, and a ventilation portion 17 transfers air between the HVAC system 14 and the outside atmosphere.

The HVAC system 14 includes an air treatment module 18 that purifies the received air. The air moving unit 15 then returns the purified air to the interior space 12 via the output path 20. The terms "purify," "purified," and variations thereof, as used in this specification, refer to the removal, purification, chemical conversion, and other means of rendering air free of contaminants, such as dust, Volatile Organic Compounds (VOCs), biological compounds, or other contaminants.

FIG. 2 is a schematic cross-sectional view of an exemplary air treatment module 18 of the HVAC system 14 of FIG. 1. The air treatment module 18 includes a first gas purifier 30 and a second gas purifier 32 in fluid communication with the input path 16 (fig. 1) such that the first gas purifier 30 and the second gas purifier 32 receive air in the form of a gas stream 34 from the interior space 12 via the input path 16.

An exemplary input portion 38 of the gas stream 34 includes a concentration of contaminants 36 therein. The source of the contaminants 36 is short term conditions in the interior space 12 such as alcohol spillage or the presence of food and beverages. The first gas purifier 30 and the second gas purifier 32 cooperate to control the concentration of the contaminants 36 such that the concentration of the contaminants 36 in the output portion 40 of the gas stream 34 is maintained within a selected concentration range.

In one embodiment, the concentration of contaminants 36 is equal to or greater than a threshold concentration such that neither the first gas purifier 30 nor the second gas purifier 32 alone is capable of maintaining the concentration of contaminants in the output portion 40 of the gas stream 34 within a selected concentration range. However, the first gas purifier 30 and the second gas purifier 32 can cooperate to control the concentration in the output section 40 within a selected range.

In previously known air treatment systems, the concentration of contaminants 36 in the output portion of the airflow may increase dramatically when the concentration of contaminants 36 temporarily exceeds a threshold concentration due to a short-term event (e.g., alcohol breakthrough). However, the cooperation of the first gas purifier 30 and the second gas purifier 32 may mitigate or eliminate such sharp increases in concentration.

In one embodiment illustrated in fig. 3, the first gas purifier 30 comprises a bed of adsorbent media 50 arranged in series with the second gas purifier 32, the second gas purifier 32 comprising a known photocatalyst 52. The adsorbent media bed 50 adsorbs contaminants from the gas stream 34. An exemplary adsorbent media bed 50 includes adsorbent media 54 between a first screen 56 and a second screen 58. The photocatalyst 52 chemically converts the contaminant 36, for example, to a more environmentally acceptable compound.

An exemplary known photocatalyst 52 includes a titanium dioxide catalyst 62 supported on a honeycomb 63 and an ultraviolet light source 64 that irradiates and activates the catalyst 62 to chemically convert the contaminants 36. The photocatalyst receives the gas stream 34 and contaminants 36 flowing through the honeycomb 63. When the ultraviolet light source 64 illuminates the catalyst 62, photons of the ultraviolet light are absorbed by the titanium dioxide to drive electrons from the valence band to the conduction band and thus generate holes in the valence band. The pushed electron reacts with oxygen and the hole remaining in the valence band reacts with water to form a reactive hydroxyl group. As the contaminants 36 in the gas stream 34 flow through the honeycomb 63 and are adsorbed onto the titanium dioxide catalyst 62, the hydroxyl radicals attack and oxidize the contaminants 36 to water, carbon dioxide, or other substances.

In another exemplary adsorbent media bed 50, the adsorbent media 54 adsorbs contaminants 36 from the gas stream 34 as the gas stream 34 passes through the adsorbent media 54. Briefly, the adsorbent media 54 retains contaminants from the gas stream 34 by sorptively capturing the contaminants 36 on a surface 60 of the adsorbent media 54.

In one example of the adsorbent media 54, the type of adsorbent media 54 is selected from zeolites, activated carbon, aluminum-containing media, or titanium-containing media.

As is known, the adsorbent media 54 adsorbs or desorbs the contaminants 36 depending on the concentration of the contaminants 36 in the gas stream 34 relative to the equilibrium concentration of the contaminants 36 at the surface 60. When the contaminant 36 concentration is above the equilibrium concentration, the contaminant will adsorb onto the surface 60. Conversely, when the contaminant 36 concentration is below the equilibrium concentration, the contaminant will desorb from the surface 60.

The rate of adsorption or desorption of the contaminant 36 is proportional to the difference between the concentration of the contaminant 36 and the equilibrium concentration and depends, for example, on the temperature and the magnitude of the difference between the concentration of the contaminant 36 and the equilibrium concentration. The adsorption and desorption processes of the adsorbent media 54 vary with the magnitude of the difference between the concentration of the contaminant 36 and the equilibrium concentration. The rate at which contaminants are adsorbed by the adsorption media 54 or desorbed from the adsorption media 54 depends on, among other things, the temperature, the magnitude and relative sign (+ or-) of the difference between the concentration of the contaminants 36 in the gas phase relative to the equilibrium concentration of the contaminants 36 on the surface 60 of the media 54.

In another embodiment, the adsorbent media 54 includes at least two different types of adsorbent media. One possible benefit associated with utilizing at least two different types of adsorbent media is to produce a desired adsorption affinity for the adsorbent media bed 50. The term "sorptive affinity" as used herein refers to the tendency of the sorption media 54 to retain or release a particular type of contaminant 36. In short, an adsorbent media 54 having a high adsorptive affinity for a particular type of contaminant 36 (e.g., an alcohol-based contaminant 36) tends to advantageously retain the particular type of contaminant 36 rather than release the contaminant 36 under normal gas flow 34 conditions (i.e., generally constant flow and generally constant non-elevated contaminant concentration). Adsorbent media 54 having a low adsorptive affinity for a particular type of contaminant tends not to retain a significant amount of that type of contaminant and tends to readily release the amount retained under normal gas flow 34 conditions.

Different types of adsorbent media 54 have different adsorption affinities for different types of contaminants 36. In one embodiment, the zeolite media has a high affinity for adsorbing water and a lower affinity for adsorbing hydrocarbons. Activated carbon media have a high affinity for adsorbing hydrocarbons and a lower affinity for adsorbing water. A mixture of different types of adsorbent media 54 (e.g., zeolite media and activated carbon media) produces a composite adsorbent media 54 having an adsorption affinity corresponding to the ratio of the different types of adsorbent media 54 in the mixture. An exemplary mixture of zeolite and activated carbon adsorbent media compounded in a 1: 1 ratio has a moderate affinity for hydrocarbon and water, which is one exemplary desired adsorption affinity for the adsorbent bed 50.

Other examples may include different ratios of other types of adsorbent media 54 and/or more than two different types of adsorbent media 54 to achieve other desired adsorption affinities, such as a desired adsorption affinity selected for a particular type of contaminant 36. Particular types of contaminants may include, for example, hydrocarbons, water, alcohols, or aldehydes. This may provide the benefit of controlling the concentration of specific contaminants 36 in the gas stream 34 when there is competition between different types of contaminants 36, including specific contaminants 36, for active catalytic sites in the photocatalyst 52.

In another embodiment, the adsorbent media 54 retains at least a portion of the contaminants 36 when the concentration of the contaminants 36 in the input portion 38 of the gas stream 34 is equal to or greater than a threshold concentration. Subsequently, when the concentration is less than the threshold concentration, the adsorbent media gradually releases the retained contaminants into the output portion 40 of the gas stream 34 (when the adsorbent media bed 50 is disposed downstream of the photocatalyst 52) or into the photocatalyst 52 for chemical conversion (when the adsorbent media bed 50 is disposed upstream of the photocatalyst 52). In short, above the threshold concentration, the adsorbent media 54 primarily adsorbs contaminants 36, and below the threshold concentration, the adsorbent media 54 primarily desorbs contaminants 36.

Such a feature may advantageously allow the adsorbent media bed 50 and the photocatalyst 52 to cooperate to control the concentration of the contaminants 36 in the output portion 40 of the gas stream 34 when the concentration in the input portion is equal to or greater than a threshold concentration.

In another embodiment, the threshold concentration exceeds the gas purification capability of the photocatalyst 52. The gas purification capacity is a concentration above which the photocatalyst is unable to chemically convert the contaminants 36. Alternatively, the gas purification capacity may be related to the gas purification efficiency, which is the percentage of the total chemically converted contaminants 36 that are all the contaminants 36 received by the photocatalyst 52. In the absence of the adsorbent media bed 50, excess contaminants 36 above the gas purification capacity would pass through the photocatalyst 52 into the output gas stream 40 and back into the interior space 12 without first being chemically converted. However, in configurations having a bed of adsorbent media 50, the bed of adsorbent media 50 acts as a buffer by retaining at least a portion of the contaminants 36 below the gas purification capacity during periods when the concentration exceeds the threshold concentration and maintaining the concentration of the contaminants 36 received by the photocatalyst 52. The adsorbent media bed 50 then gradually releases the retained contaminants 36 to the photocatalyst 52 for chemical conversion when the concentration of the contaminants 36 in the gas stream 34 is less than the threshold concentration.

FIG. 4 is a schematic cross-sectional view of another exemplary air treatment module 18 of the HVAC system 14 of FIG. 1. The air treatment module 18 includes integrated first and second gas purifiers 74. In short, the first gas purifier 30 and the second gas purifier 32 of fig. 2 are integrated into a single structure.

In one exemplary integrated first and second gas purifier 74 illustrated in fig. 5, the adsorbent media 84 and the catalyst material 86 are deposited onto the honeycomb structure 88 such that the gas stream 34 may flow through the honeycomb structure openings 90 and contact the adsorbent media 84 and the catalyst material 86. In addition to the other benefits described above, the integrated first and second gas purifiers 74 may also provide a more compact size air treatment module 18.

The air treatment module 18 of the present embodiment may control the concentration of the contaminants 36 in the output airflow 40 when the concentration of the contaminants 36 in the input airflow 38 temporarily exceeds a threshold concentration.

Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims (21)

1. A gas treatment module, the module comprising:

a first gas purifier and a second gas purifier arranged in fluid communication with each other, wherein the first gas purifier and the second gas purifier are integrated in a single monolithic structure comprising a honeycomb having an adsorbent media comprising at least two different types of adsorbent media and a photocatalytic material on the surface of the honeycomb, and wherein the first gas purifier comprising the adsorbent media is capable of temporarily retaining at least a portion of the contaminants in the gas stream when the concentration of the contaminants is greater than or equal to a threshold concentration and subsequently releasing at least a portion of the retained contaminants to the second gas purifier when the concentration is less than the threshold concentration.

2. The module of claim 1, wherein the first gas purifier and the second gas purifier maintain the concentration of the contaminant in the output portion of the gas stream within a selected concentration range during a period in which the concentration of the contaminant in the input portion of the gas stream temporarily exceeds a threshold concentration.

3. The module of claim 2, wherein each of the first gas purifier and the second gas purifier is individually incapable of maintaining a concentration of the contaminant in the output portion of the gas stream within a selected concentration range.

4. The module of claim 2, wherein the first gas purifier temporarily maintains the concentration of contaminants in the gas stream below the gas purification capacity of the second gas purifier to control the concentration in the output portion of the gas stream when the threshold concentration is temporarily greater than the gas purification capacity.

5. The module of claim 1, wherein the first gas purifier gradually releases the retained contaminants when the concentration is less than a threshold concentration.

6. The module of claim 1, wherein the second gas purifier comprises an oxidation reactor, and the adsorbent media adsorbs contaminants to retain the contaminants and desorbs the contaminants to release the contaminants into the oxidation reactor.

7. The module of claim 1, wherein the first gas purifier includes a catalyst, the second gas purifier includes the adsorbent media, and the catalyst adsorbs at least a portion of the contaminants on a surface of the catalyst and chemically converts the adsorbed portion of the contaminants to other compounds.

8. A gas treatment module, comprising:

an adsorbent media comprising at least two different types of adsorbent media, the adsorbent media capable of temporarily retaining at least a portion of the contaminants in the gas stream when the contaminant concentration is greater than or equal to a threshold concentration and subsequently releasing at least a portion of the retained contaminants when the concentration is less than the threshold concentration; and

a reactor in fluid communication with the sorption media, the sorption media cooperating with the reactor to control the concentration of the contaminant in the output portion of the gas stream, wherein the sorption media and the reactor are integrated into a single monolithic structure, wherein the single monolithic structure comprises a honeycomb having the sorption media and a photocatalytic material on the surface of the honeycomb.

9. The module of claim 8, wherein the adsorbent media comprises a plurality of different types of adsorbent media.

10. The module of claim 9, wherein the plurality of different types of adsorption media comprises at least one of a zeolite, activated carbon, titanium-based adsorption media, silica gel, activated clay, or aluminum-based adsorption media.

11. The module of claim 8, wherein the reactor has a gas purging capacity and the threshold concentration exceeds the gas purging capacity.

12. The module of claim 8, wherein the reactor comprises a catalyst that receives the released contaminants and chemically converts at least a portion of the released contaminants.

13. The module of claim 8, wherein the adsorbent media is disposed downstream of the reactor and the retained contaminants retained by the adsorbent media are received from the reactor.

14. The module of claim 8, wherein the adsorbent media gradually releases the retained contaminants when the concentration is less than a threshold concentration.

15. A method of treating a gas by using the gas treatment module of claim 1 or 8, the method comprising:

the concentration of contaminants in the output portion of the gas stream is controlled when the concentration of contaminants in the input portion of the gas stream is temporarily greater than or equal to a threshold concentration by temporarily retaining the contaminants when the concentration of contaminants in the input portion of the gas stream is temporarily greater than or equal to the threshold concentration, and releasing the retained contaminants when the concentration is less than the threshold concentration.

16. The method of claim 15, comprising maintaining the concentration of the contaminant in the output portion within a selected concentration range.

17. The method of claim 16, comprising gradually releasing the retained contaminants and chemically converting the released contaminants before the released contaminants enter the gas stream output section.

18. The method of claim 15, comprising chemically converting a portion of the contaminant concentration, temporarily retaining a remaining portion of the contaminant concentration, and subsequently releasing the remaining portion to maintain the contaminant concentration in the output portion within a selected concentration range when the concentration does not exceed the threshold concentration.

19. The method of claim 15, comprising controlling the concentration of the contaminant in the output portion of the gas stream when the threshold concentration exceeds the purification capacity of at least one gas purifier in the gas stream.

20. The module of claim 1, wherein the first gas purifier and the second gas purifier are disposed directly adjacent to each other.

21. The module of claim 8, wherein the adsorbent media comprises a plurality of different types of adsorbent media selected from the group consisting of zeolites, activated carbons, titanium-based adsorbent media, silica gels, activated clays, and aluminum-based adsorbent media.