Patent Application
20220176006
Photocatalytic oxidation (PCO) is a known technique for removing volatile organic compounds (VOCs) such as formaldehyde, methane, chlorides, and benzene from air. PCO generally involves exposing a catalytic surface such as a titanium dioxide (TiO2) surface to ultraviolet (UV) light. In general, the UV light breaks chemical bonds in compounds that are in contact with the catalytic surface. For example, UV light interacts with water vapor (H2O) at a TiO2 surface to produce reactive OH− ions that can oxidize VOCs. An efficient PCO process can convert the VOCs into more basic and non-toxic compounds such as carbon dioxide (CO2) and water.
Current PCO-based air purifiers have limitations. PCO-based air purifiers particularly need a controlled air flow. If air flow moves too quickly, the desired reactions do not occur or are incomplete, and the purifier could even create and release additional toxic pollutants. Many current PCO-based air purifiers also have mesh-shaped catalyst that allow air to pass through large gaps without interacting with the catalyst, and as a result, the air purifiers may not provide enough catalytic surface area that interacts to provide effective one-pass air cleaning. Another problem is that current PCO air purifiers are mostly standing devices that take up floor or counter space in homes or establishments using the PCO air purifiers.
In accordance with an aspect of the present disclosure, a PCO system has a thin, flat structure that may be wall mounted and disguised with a decorative face or feature such as a painting or other aesthetically pleasing wall decoration. The wall mounting saves space, and the flat geometry of the PCO efficiently produces oxidation reactions with a large continuous surface area catalyst. The PCO system may include a distributed or large-area UV-light source positioned to directly irradiate a catalytic sheet, e.g., a titanium dioxide (TiO2) sheet or TiO2-coating on a sheet of another material. The catalytic sheet may have surface variations such as undulations, projections, or villi-like structures to further increase catalytic surface area for improved reactions. The flat PCO structure may also provide wide air inlets and outlets for an effective air flow even at slow air velocities. Ambient air passes in between the UV lighting sheet and the catalytic sheet, and heating of air in the PCO system, which is inherent to the catalyzed reactions and absorption of UV light, drives or helps move air upward through the PCO system. In some configurations, uneven heating, e.g., a non-uniform UV light intensity emission from the UV sheet, may create a temperature gradient that improves air flow.
The drawings illustrate examples for the purpose of explanation and are not of the invention itself. Use of the same reference symbols in different figures indicates similar or identical items.
Highly efficient air purification systems and methods use a flat, wall-mounted enclosure containing a photocatalytic oxidation (PCO) system to remove airborne contaminants such as volatile organic compounds (VOCs) from the air. The horizontal width and vertical height of the PCO system being large compared to its thickness of the PCO system maximizes area available for a catalyst of light-driven reactions. PCO performance may be optimized through increasing the surface area of the catalyst and reducing the air flow speed, which results in efficient pollutant contact with the catalytic surface where UV light is incident. The structure and does not require floor or counter space for PCO air purification, and a visible face of the wall-mounted structure may have an integrated or user-selected aesthetic feature to make the air purification system a desirable addition to a room or other interior environment.
Enclosure 110 and air purifier 100 are generally flat having vertical and horizontal dimensions up to about 20 cm to 2 m or more and thickness about 1 to 10 cm or less. More generally, while air purifier may be box shaped with horizontal and vertical sides forming edges of a square or a rectangle, air purifier 100 may have any shape, e.g., square, rectangular, circular, oval, polygonal, star-shaped, or irregularly shaped. Further, the size and shape of air purifier 100 may be chosen according to the desired air purification capabilities for air purifier 100, the available wall space where air purifier 100 will be install, or aesthetic inclinations. Air inlet 116 and air outlet 118 are generally narrow to provide a thin air purifier profile but may run substantially the entire horizontal width of enclosure 110 to maximize air throughput at low air velocity.
PCO air purifier 100 internally includes a UV light panel 120 and a catalytic panel 130 that are separated by an air channel or gap 150. Air channel 150 is thin e.g., less than about 1 cm, but has an area that is substantially the same as the wall area of air purifier 100. In operation, UV light panel 120 directs UV light in a roughly horizontal direction through air channel 150 onto a surface 132 of catalytic panel 130 while ambient air flows vertically upward through channel 150. More specifically, ambient air from the room containing air purifier 100 enters air channels 150 via inlet 116 at the bottom of air flow channels 150, flows upward along surface 132 of catalytic panel 130 while being irradiated with UV light from UV light panel 120, and exits through outlet 118 at the top of air channel 150. Optionally, inlet system 116 or outlet system 118 may have associated air filter and movement systems. For example, a filter system 152 may include a high-efficiency particulate air (HEPA) filter that removes particulates from the ambient air passing through air purifier 100. An air filter system 152 may remove particulates, while photocatalytic reactions remove chemicals such as VOCs that may pass through filter system 152. Alternatively, the photocatalytic process may oxidize particulates, but filter system 152 may advantageously prevent particles from entering channel 150 to avoid or reduce fouling of light panel 120 or catalytic panel 130. An air movement system 154 may include an array of small diameter fans lined up along the length of inlet 116 or one or more squirrel cage fans or blowers. In general, whether air movement system 154 is needed in air purifier 100 may depend on the air flow that convection provides, the maximum air velocity providing efficient photocatalytic reactions, and the minimum air velocity needed to achieve a desired air purification rate.
UV light panel 120 includes one or more light sources that produce UV light that is directed at catalytic panel 130 and distributed across the area of catalytic panel 130. UV light panel 130 may for example include an array of light emitting diodes (LEDs) or laser diodes that emit that collectively emit one or more of UV-A light having wavelengths between about 320 nm and about 400 nm, UV-B light having wavelengths between about 290 nm and about 320 nm, or UV-C light having wavelengths between about 100 nm and about 290 nm. For example, UV-A and UV-C wavelengths may be used for TiO2 as the catalyst in catalytic panel 130. UV-A light is generally safer if humans may be exposed to UV light that escapes from air purifier 100, but UV-C light may be safely confined inside air purifier 100 and used to kill or deactivate airborne germs or virus that enter air purifier 100.
The intensity of light from UV light panel 120 is related to the optimal air velocity through air purifier 100. In general, the airflow may intentionally be kept slow to allow for the complete decomposition of VOCs. An air flow rate may be about 1 CFM for every 10 W/m2 incident on catalytic panel 130.
Energy from UV light panel 120 and from the catalyzed reactions may heat air inside air channel 150 resulting in convection where the heated air rises up and out of outlet 118 and draws ambient air in through inlet 116 at the bottom of air purifier 100. The heating may be achieved using a nominally uniform spatial distribution of the light from UV light panel 120. In accordance with an aspect of the current disclosure, a UV light panel that produces UV light with a non-uniform, spatial intensity distributions may drive convective airflow in an air purifier.
Air flows inside air purifier 100 of
In accordance with an aspect of the current disclosure, surface 132 of catalytic panel 130 includes a continuous sheet that may be contoured to increase catalytic surface area that enclosure 110 of air purifier 100 can accommodate. Surface 132 may, for example, be pleated or textured to increase surface area and maximize the efficiency of the PCO process. A catalytic panel may be layered or textured to increase the area available for catalyzed reactions. A layered catalytic panel may have one or more layers that are exposed to air flow and semitransparent to pass UV to underlying layers. Additionally, a catalytic panel may include a reflective surface to reflect some UV light back through translucent or transmissive layers or reflect some UV light to catalytic surface areas that might not receive direct UV light from the light panel.
PCO system 300 illustrates only one example of contoured surface shaped to increase the catalytic surface area available within a specific horizontal width W and vertical length L. Some additional or alternative ways to provide increased catalytic surface area include any repetitive shape contours, e.g., a saw shape. Additionally, a catalytic surface may include fingers or villi-like projections, e.g., TiO2 rods or threads, extending from an otherwise continuous flat or contoured surface. Projections 334 on wave-shaped catalytic surface 332, for example, may increase the reactive surface area of catalytic panel 330. Fractal surfaces may be most efficient to maximize the reactive surface area of a catalytic sheet contained within a specific width and length.
Air purifiers such as air purifier 100 of
Although particular implementations have been disclosed, these implementations are only examples and should not be taken as limitations. Various adaptations and combinations of features of the implementations disclosed are within the scope of the following claims.
This patent document claims benefit of the earlier filing date of U.S. Provisional Pat. App. No. 63/120,894, entitled “Photocatalytic Oxidation System for Removal of Indoor Pollutants within Wall-Mounted Decorative Structures,” filed Dec. 3, 2020, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63120894 | Dec 2020 | US |
