Patent Application
20230089967
The invention generally relates to systems and methods for air treatment. More specifically, the invention relates to a method for purifying air from chemical and biological pollutants, such as Volatile Organic Compounds (VOCs), formaldehyde, viruses, bacteria, etc., and to a domestic system for air purification, achieving reduction of CO2 levels and biological load.
Heating, ventilation and air conditioning (HVAC) systems used in homes and offices facilitate the accumulation of air pollutants within air-regulated closed spaces. A central HVAC system that operates in an office building accumulates outdoor air, regulates its temperature and moisture, and circulates the regulated air within spaces of the building. However, the air which is brought from the outdoor to the system is in many cases polluted, resulting in a conveyance of micro-particles of, for example, dust, smoke, smog, chemicals, etc. into the closed space, and additional micro-particles are added from within the spaces themselves. The situation is similarly problematic in the air-conditioning of small homes, where the indoor air is circulated in a closed-loop, without even adding outdoor refreshing air into the loop. Both cases (i.e., of office-buildings and small homes) result in the accumulation of solid particles and gases, such as dust, smoke, smog, and bio-hazards such as viruses and bacteria, within the air-regulated spaces. These micro-pollutants impair health and productivity.
A variety of domestic air purifiers (hereinafter also referred to as “home-purifiers” or “room purifiers” that are used in individual rooms at homes, offices, hospitals, medical clinics, waiting rooms, etc.) that are supplementary to existing HVAC systems have been developed to reduce the accumulation of polluting particles in closed spaces. These are stand-alone devices that typically include a quiet blower and a set of one or more fine filters. These air purifiers are designed to circulate the room's air through the set of fine filters, thereby capturing particles in sizes ranging from 1 μm to 10 μm and larger. 1 μm particles generally originate from smoke and smog, 2.5 μm particles originate from motor-vehicle exhausts and wood-burning fires, and 10 μm and larger particles originate from general dust. While capturing up to 99% of those micro-sized particles, these traditional air purifiers are usually not effective against a multitude of chemical and biological contaminants, i.e., reduction of carbon dioxide indoor levels, alongside Volatile Organic Compounds (VOCs), (e.g., formaldehyde), allergens, bacteria, viruses, etc.
There exists a need to provide a domestic air purifier having the capability of removing airborne chemical and biological pollutants.
Incorporation of chemistry into air purifiers to improve the quality of indoor air by reduction of biological load is described in JP 2003-161482 (electrochemically generated H2O2 solution), JP 2001-062239 and CN 2675130 (the treated air is passed through chemical solutions arranged successively, including alkali hydroxide and sodium peroxide).
An aqueous alkali hydroxide/H2O2 solution (i.e., an alkali hydroxide solution to which H2O2 is added, hereinafter also named “MOH/H2O2 reagent”; M stands for the alkali metal, e.g., sodium, potassium or a mixture thereof) has been previously reported as a generator of the superoxide radical anion (O2—.). In a series of publications (WO 2013/093903; Stoin, U. et al. ChemPhysChem, 2013, 14, 4158 and WO 2015/170317), it was shown that the aqueous MOH/H2O2 reagent is a powerful oxidizer that could be used to serve several useful purposes:
absorbing carbon dioxide from flue gases;
destroying bulk carbon tetrachloride and other chlorinated methane and ethane compounds; and
remediating soil from diesel oil and crude oil contaminants.
In co-assigned WO 2018/002710, the focus was shifted to air treatment, proposing using the aqueous MOH/H2O2 reagent for removing target gases from the air, mainly carbon monoxide arising in case of fire. Other target gases which the MOH/H2O2 reagent could neutralize are listed on page 15 of WO 2018/002710. The system described in WO 2018/002710 includes an inlet that receives a flow of contaminated air from the treated space and a reaction chamber that contains an aqueous solution such that an amount of one or more target gas species contained within a plurality of bubbles are reduced through reaction with the solution. The treated air that flows out of the solution is then returned into the treated space. WO 2018/002710 demonstrates the efficiency of the reaction chamber in converting toxic gases (such as carbon monoxide, carbon dioxide, NOx, etc.) to harmless chemical substances, e.g., oxygen, therefore facilitating breathing, particularly in the case of highly contaminated air during a fire. However, the state of a home or office room in a normal condition is substantially different from the state of the fire-polluted air treatment as demonstrated by WO 2018/002710, as the concentration rate of contaminants in the case of fire is several orders higher compared to a room in normal conditions.
In another aspect, a conventional domestic air-purifier is a stationary unit, requiring the positioning of a dedicated unit in each room to be treated, no matter whether the rate of contaminants in the room in a given time is above a harmful threshold or not. This configuration results in waste of resources or compromise of air-quality in rooms where a home-purifier is not positioned.
It is an object of the present invention to provide a novel home-purifier for reducing bio-hazards.
Another object of the present invention is to provide a home-purifier that reduces hazardous or harmful gases and bio-hazards.
Another object of the invention is to provide said novel home-purifier in a compact size and quietness of operation.
Still another object the invention is to provide a single home air purifier capable of treating a plurality of rooms within an office or home.
Still, another object of the present invention is to provide a compact reactor within said compact and quiet home air purifier for reducing bio-hazards and hazardous or harmful gases.
It is still another object of the present invention to integrate the home air purifier of the present invention with a traditional home air purifier.
Other objects and advantages of the invention become apparent as the description proceeds.
The present invention is specifically aimed at addressing the need to maintain good indoor air quality. Contaminants found in indoor air in buildings and structures are classified into two groups: chemical contaminants and biological contaminants.
A major chemical contaminant is formaldehyde, a colorless, pungent-smelling gas which is considered by the United States Environmental Protection Agency to be an important hazardous air pollutant, arising from glues and foams used in furniture, some textiles (e.g., carpets), and from combustion processes such as cooking and smoking. The major biological contaminants are bacteria, fungi, and viruses.
Experimental work conducted in support of this invention indicates that the MOH/H2O2 reagent can reduce VOC levels (e.g., formaldehyde) in indoor air. The MOH/H2O2 reagent has demonstrated high, steady conversion rates of gaseous formaldehyde into harmless by-products over a long test period, challenging characteristic formaldehyde levels (few tenths of a milligram per cubic meter, ˜0.2 mg/m3). Likewise, low carbon dioxide concentrations in indoor air could also be effectively targeted by the MOH/H2O2 reagent, leading to essentially complete elimination of carbon dioxide with a potential benefit of oxygen generation (O2 is by-product of CO2 oxidation by superoxide).
Results reported below also indicate that the MOH/H2O2 reagent possesses air-sanitizing action. That is, it acts on airborne microorganism. The MOH/H2O2 reagent may therefore be used to control microbiological load in indoor air, specifically by eliminating bacteria. Hydrogen peroxide is known to act on bacteria, but the antibacterial effect of the MOH/H2O2 reagent is surprising, bearing in mind that hydrogen peroxide decomposes instantly in an alkaline environment. Experimental work conducted in support to this invention shows that when air stream that was loaded with a bioaerosol (produced from bacteria (K. rhizophila) was treated with the MOH/H2O2 reagent, high log reduction of bacterial load was measured versus control. The MOH/H2O2 reagent is also effective in combatting viruses: in the experimental model described below, a removal rate of more than 99.9% was measured (the tested virus was a corona virus, e.g., human coronavirus such as OC43).
As shown below in reference to the drawings, several reactor configurations could be used to achieve an efficient contact between the incoming indoor air stream and the aqueous MOH/H2O2 reagent, mainly based on the creation of air bubbles that are forced to travel through the bulk reagent.
One major aspect of the invention is therefore a method for improving indoor air quality in a room, comprising drawing air from the room and guiding the air to a gas/liquid contactor charged with aqueous alkali hydroxide/H2O2 solution, passing the air through a perforated membrane installed in the gas/liquid contactor below the surface level of the aqueous alkali hydroxide/H2O2 solution, such that bubbles produced travel through said solution, and getting treated air with improved quality from said gas/liquid contactor, said treated air is characterized by having:
reduced carbon dioxide levels (from 1000-200,000 ppm, e.g., from 1000-10,000, down to less than 1000 ppm, e.g., down to 400-700 ppm); and/or
reduced VOC (e.g., formaldehyde) levels; and/or
reduced microbiological load (e.g., at least 1-log reduction of bacterial load and/or viral load, e.g., at least 2-log reduction). Another benefit gained is oxygen enrichment in indoor environment, up to 233.
The term “perforated membrane”, as used herein, relates to a perforated element allowing passage of air therethrough, to disperse the air stream and create bubbles within a solution. It can have a flat geometry, (e.g., membrane 836 as shown in
The invention also relates to an air purifier for eliminating chemical and biological pollutants from a room, which comprises: (a) an inlet air channel; (b) one or more air sucking components configured to direct air from the room into said inlet channel, and to direct the air via said air channel into a perforated membrane mounted in a chemical and biological pollutants-elimination reactor; and (c) an outlet air channel configured to receive treated air from the reactor; (d) wherein the reactor comprises: (d.1) a reservoir configured to contain a purifying aqueous alkali hydroxide/H2O2 solution; wherein during the purifier's operation, said perforated membrane is positioned below a surface level of the solution such that air passing through the perforated membrane is converted into bubbles that travel through the solution and towards said outlet channel; and wherein the air purifier further comprises a removable storage unit positioned above the reactor, said removable storage unit is configured to contain and supply alkali hydroxide, hydrogen peroxide, and optionally water to said reactor.
In an embodiment of the invention, said inlet air channel conveys air in a downwards direction, the inlet air channel passes through an opening in said perforated membrane towards an air compartment located below the perforated membrane.
In an embodiment of the invention, a bottom outlet of said inlet air channel is sealed against a top surface of the perforated membrane, thereby allowing passage of air from the inlet air channel only through the perforations of the membrane towards a section of the reservoir below the membrane, and wherein the diameter of said membrane is smaller than the diameter of the reservoir of alkali hydroxide/H2O2 solution.
In an embodiment of the invention, each perforation at the membrane has a diameter in the range of 40 μm and 1200 μm.
In an embodiment of the invention, each of the perforations has top and bottom openings, respectively, at top and bottom surfaces of the perforated membrane, the diameter of said top opening is larger than a diameter of said bottom opening.
In an embodiment of the invention, each of the perforations is divided into two sections in cross-section, a lower section having a cylindrical shape, and an upper section having a frustoconical shape.
In an embodiment of the invention, a bottom outlet of said inlet air channel is configured to lead contaminated air to a perforated membrane, said perforated membrane having a spiral tubing configuration and positioned at a lower portion of said purifying solution's reservoir.
In an embodiment of the invention, each said perforations is positioned at a lower portion of the tubing in cross section, thereby directing air outlet through the perforation downwards.
In an embodiment of the invention, each of said perforations is positioned at least 30° lower than the tubing horizontal diameter in cross-section. In this embodiment of the invention, each of said perforations has a diameter in the range of between 40 μm and 1200 μm.
In an embodiment of the invention, a distance between each two perforations is in the range of 2-50 of the perforation's diameter.
In an embodiment of the invention, said storage unit comprises an alkali hydroxide container, a H2O2 container, and optionally a water container.
In an embodiment of the invention, the air purifier has an essentially cylindrical shape, wherein said alkali hydroxide container, said H2O2 container, and said water container are arranged concentrically within the storage unit.
In an embodiment of the invention, the alkali hydroxide container is configured to contain alkali hydroxide tablets in a releasable arrangement.
In an embodiment of the invention, the alkali hydroxide container comprises a plurality of columns, each column is configured to store alkali hydroxide tablets.
In an embodiment of the invention, the alkali hydroxide container is configured to angularly revolve, thereby to position a single column above an opening to a passage leading to said solution reservoir, thereby to allow a periodical feeding of the solution by hydroxide tablets.
In an embodiment of the invention, the air purifier has a blower and a HEPA filter fitted in the inlet channel upstream to the reactor.
In an embodiment of the invention, the air purifier is integrated with a domestic room purifier having a HEPA filter, wherein the inlet air channel is a branch from an inlet air channel of the domestic room purifier diverging downstream to the HEPA filter, and wherein the outlet channel joins an outlet channel of the domestic room purifier.
In an embodiment of the invention, the air purifier further comprising a sensor for measuring a concentration of CO2 at the room-air, and wherein a schedule and a period of operation of the device is based on CO2 measurements by said sensor.
The invention also relates to a home air purifying system, comprises: (a) a plurality of air-quality sensors, each sensor being positioned at another room of the home; (b) a docking station which is configured to: (b.1) host a mobile, air purifier; (b.2) receive air quality measurements from all said plurality of sensors, and determine when a level of contamination at a room exceeds a predefined contamination threshold; and (b.3) communicate with said mobile air purifier, and at least send to it an indication of a room in which a contamination above said predefined contamination threshold has been detected; and (c) said mobile air purifier, which is configured to: (c.1) communicate with said docking station, and at least receive from it an indication of the room in which the contamination above said predefined contamination threshold has been detected; (c.2) upon receipt of said indication, navigate to the contaminated room, operate there to purify the room, and upon completion, return to the docking station.
In an embodiment of the invention, said contamination comprises one or more chemical and biological contaminants.
In an embodiment of the invention, said mobile air purifier comprises: (a) an inlet air channel; (b) one or more air sucking components configured to suck air from the room into said inlet channel, and to direct the air via said air channel into a perforated membrane mounted at a bio-hazards elimination reactor; and (c) an outlet air channel configured to receive treated air from the reactor, and to return the treated air into the room; wherein the bio-hazards elimination reactor comprising: (d) a reservoir configured to contain a purifying aqueous alkali hydroxide/H2O2 solution; wherein during the purifier operation said perforated membrane is positioned below a surface level of the solution such that air passing through the perforated membrane is converted into bubbles that travel through the solution and towards said outlet channel; and wherein the air purifier further comprising a removable storage unit positioned above the reactor, said removable storage unit is configured to contain and supply alkali hydroxide, hydrogen peroxide, and water to said reactor.
For example, an aqueous alkali hydroxide/H2O2 solution is charged to the gas/liquid contactor either by feeding alkali hydroxide solution prepared beforehand, or by dissolving solid alkali hydroxide (e.g., in a tablet or granular form) in water supplied separately to the gas/liquid contactor, with continuous or periodic addition of hydrogen peroxide solution to the alkali hydroxide solution.
For example, air bubbles (created by forcing the incoming air stream to flow across a membrane as described in detail below) are caused to travel through the alkali hydroxide solution (e.g., NaOH or KOH, or their mixture), to which H2O2 stream is periodically or continuously added (for example, by injection beneath the level of the alkali hydroxide solution, in close proximity to the perforated membrane, i.e., in the vicinity of the perforations). Concentration of the alkali hydroxide solution varies from 5% to 48%-50% by weight, e.g., from 10 to 48%-50% by weight. The concentration of the hydrogen peroxide solution added to the alkali hydroxide solution is from 3%, 4- or 5% up to 35% by weight, e.g., from 10 to 30% by weight. Acceptable addition rate of the H2O2 stream may vary from 0.01 ml/min to 10 ml/min, e.g. up to 2, 3 or 4 ml/min. The volumetric ratio between the solutions in the range of 2:1 to 10:1 in favor of the alkali hydroxide solution. The proportion can be adjusted according to the profile of pollutants. As mentioned above, chemical pollutants targeted by the invention include carbon dioxide and VOC; biological pollutants include bacteria and viruses such as corona virus, e.g., human coronavirus such as OC43.
A perforated membrane with flat (planar) geometry is preferably horizontally mounted in the vertically positioned air-purifier. Suitable perforated membranes are 1-10 mm thick, made of chemically inert materials (stainless steel, plastic, etc.), and have 40-1200 μm diameter holes, which are generally evenly distributed over the membrane. The diameter of a hole may be constant, i.e., it does not vary within the membrane thickness, such that the two opposing sides of a passage (a hole) are equal in diameter. One design of the perforated membrane involves variation of the diameter of the perforations (holes) through which the air flows to cross the membrane. Preferably, the air is passed through the membrane via perforations whose diameter increases across the membrane thickness (in operation, the diameter increases from the bottom surface to top surface of the membrane); the perforations are passages consisting of a cylindrical section (with diameter (Dcylinder) in the range from, e.g., 0.08 mm to 1 mm) joining an inverted frustoconical section facing the solution (the diameter of the small base of the frustoconical equals Dcylinder; the diameter of the large base of the frustoconical section, facing the solution, is 1.3 to 2.0 times larger than Dcylinder, with separation between the perforations (passages) being at least 3 times larger than Dcylinder). Alternatively, the passage is shaped as a frustrum of a cone having a small base and a large base; the air passes through the membrane by entering through the small base and exiting through the large base facing the solution. The benefits received from this geometry are explained below.
With the aid of HEPA filter (high-efficiency particulate filter) added and a blower, the device described above can function as a stand-alone air purifier that reduces the chemical and microbial load of an indoor environment. Alternatively, it may be coupled to conventional air purifiers or HVAC systems. As pointed out above, a conventional air purifier (equipped with a static filter) or HVAC system could benefit from an auxiliary unit integrated thereinto to treat a secondary air stream that has been diverted from the main airflow, with the aid of the MOH/H2O2 reagent. The chemically and/or biologically decontaminated air thus generated (e.g., with reduced formaldehyde and/or CO2 levels and/or reduced microbiological load) is guided to join the main airflow released from the conventional air purifier, as illustrated below in
Accordingly, the air drawn into the gas/liquid contactor (where the MOH/H2O2 reagent is placed) is a filtered air stream resulting from passing indoor air through a filter that captures particles.
A specific aspect of the invention is a method for improving indoor air quality, comprising the steps of:
drawing indoor air and passing same, at a first flow rate, across a filter to capture airborne particles and produce a main filtered air stream;
diverting a portion of the main filtered air stream to generate a secondary filtered air stream flowing at a second flow rate, forcing said secondary filtered air stream into a gas/liquid contactor charged with the MOH/H2O2 reagent, where the filtered air, in the form of bubbles, is contacted with the MOH/H2O2 reagent;
withdrawing filtered and decontaminated air stream from said gas/liquid contactor; and
joining said filtered and decontaminated air stream with the main filtered air stream.
Characteristic flow rates for the main filtered air stream and secondary filtered air stream may be from 500 to 8000 L/min and 80 to 1,000 L/min, respectively.
In the drawings:
In the structure presented in
In one embodiment of the invention, controller 435 may periodically drain the entire purifying solution 438 into a waste container 454 and renew the solution by fresh content from cartridge A, Cartridge B, and water. In some cases, one or more of the cartridges contains aqueous MOH and/or aqueous H2O2. Therefore a separate cartridge for water may not be necessary. The inventors have found that the structure presented in
Also shown in
The airborne bio-hazards purifier of the invention was tested. The purifier of the invention significantly reduces the level of bio-hazards (such as viruses and bacteria) in the air and reduces other toxic gases, such as CO2, CO, formaldehyde, etc.
Periodically, or based on any other definition, the docking station 712 is activated to drain the existing liquid from reservoir 738 of the mobile air purifier into sewage tank 748, and refill reservoir 738 with new liquids (or solids, as is applicable) from tanks 742, 744, and 746 (in predetermined proportions). The docking station and the mobile air purifier include additional components, such as pumps, valves, etc., to perform these tasks. The mobile air purifier also includes a blower for circulating air into the reservoir (in the form of bubbles, as described) and release it into the room.
The components that are required for the navigation may be divided between the mobile purifier and the docking station in various possible configurations. In one embodiment, the mobile purifier 710 maintains a full navigation capability (i.e., map of the house, etc.). The docking station can indicate the targeted room, and based on this indication, the mobile purifier navigates autonomously to the targeted room. In another configuration, the navigation capabilities are maintained within the docking station 712, while it sends real-time direction commands, such as right, left, forward, backward, move, stop, etc., to the mobile purifier.
The system may also include a remote control (for example, user smartphone 720). The remote control may define various parameters of the system.
As noted, the system preferably utilizes the Wi-Fi router of the house for communication between all its components. Other types of wireless networks may be used. Moreover, a central computer, which may be separate from the docking station, may be utilized to receive sensors' data and send commands to the mobile device. In such a case, the docking station serves only as a recharging station for the mobile air purifier.
Reference is now made particularly to
For example, the weight of each tablet may be about 5 to 100 g, e.g., from 15 to 30 g, and 2 to 100 tablets may be included within cartridge 826. The water container may contain 1 to 10, e.g., 2 to 6 liters, and the hydrogen peroxide container may include between 250 ml and 10 liter. Initially, the user removes the storage unit using handle 863 and fills it with the solution ingredients. Upon filling the water container with tap water, and filling cartridges A 826 and B 828 with tablets and liquid, respectively, and remounting the storage unit at the purifier, the device is ready for operation. The water is poured down to the reactor via pipe 853, and one tablet (or more, if necessary) is dropped down to the solution via opening (and respective pipe) 859. A dose of the hydrogen peroxide is conveyed periodically into proximity of the perforated membrane utilizing pump 839, pipe 855 (one or more pipes may be used), and respective perforations (not shown) on tube 855a (
During the process, air from the sump penetrates solution 838 via the membrane's 836 perforations, creating bubbles that interact with the solution as described above. The bubbles leave the solution as a purified air. The purified air passes through demister 846, which removes from the purified air residues of aerosol and droplets of the reactive liquid that the airflow may carry. The outlet of the demister includes a funnel (not shown), which is connected to a pipe (not shown) leading to the carbon filter 849.
After some period of operation, the effectiveness of solution 838 reduces to a degree requiring entire replacement by fresh water and ingredients from cartridges A and B, respectively. When such a necessity arose, pump 857 pumps and conveys the entire liquid content of compartment 820 (
The inventions' process is optimized when as small as possible and as many as possible bubbles are simultaneously created. This configuration maximizes the overall interaction surface between the bubbles and solution 838. However, it has been found that a membrane with too close perforations results in vast merges of proximate bubbles, as illustrated in the prior art membrane 896 of
In some cases, the height of the lower cylindrical section of the perforation is reduced (compared to the upper conical section's height). In some other cases, the lower cylindrical section of the perforation may be eliminated, resulting in a truncated cone cross-section.
Purifier 800 may be stationary, mobile (in similarity to embodiment 700), or manually carried from one room to another.
Another aspect of the invention involves modifying the indoor air treatment program offered by the MOH/H2O2 reactor described above, by incorporating a CO2 adsorption scrubber upstream of the MOH/H2O2 reactor. A battery consisting of CO2 adsorption scrubber and MOH/H2O2 reactor offers greater versatility in coping with changes in CO2 levels in the room, and better management of alkali hydroxide and hydrogen peroxide feed supply to the reactor, because the battery can switch between different modes of operation, depending chiefly on factors such as CO2 level in the room and presence of occupants in the room. The CO2 adsorption scrubber and MOH/H2O2 reactor may be designed to operate with airflows supplied at different volumetric rates (high and low, respectively).
Reduction of CO2 levels in indoor air can be achieved in different ways using a battery consisting of CO2 adsorption scrubber and MOH/H2O2 reactor:
1) by the action of adsorption scrubber alone: indoor air is passed through the scrubber; CO2 is captured and held for some time in the scrubber. During that period of time, air with improved quality is supplied to the room from the scrubber. The scrubber is discharged by releasing CO2 to the room, e.g., overnight.
2) by the action of MOH/H2O2 reactor alone: indoor air is guided directly to the MOH/H2O2 reactor, bypassing the adsorption scrubber; CO2 is transformed into harmless carbonate/bicarbonate salts; air with improved quality is supplied to the room from the reactor.
3) by a combined mode of operation: indoor air flows through the scrubber over a period of time during which the MOH/H2O2 reactor is at rest. CO2 is captured and held in the scrubber but after a while the MOH/H2O2 reactor enters into service such that CO2 discharged from the scrubber is directed to, and mineralized in, the MOH/H2O2 reactor.
Accordingly, one aspect of the invention relates to the combined mode of operation outlined above, i.e., by capturing and holding CO2 is an adsorption scrubber, and after a while, discharging the CO2 from the scrubber and mineralizing the CO2 in the MOH/H2O2 solution, i.e., to a method of improving indoor air quality, comprising:
providing airflow through CO2 adsorption scrubber over a first period of time to capture CO2 by an adsorbent in the scrubber while reintroducing CO2-depleted air from the scrubber into a room; desorbing CO2 from the adsorbent during a second period of time (for example, by heating the adsorption scrubber to reach desorption temperature) while guiding air laden with the desorbed CO2 from the scrubber into a gas/liquid contactor charged with aqueous alkali hydroxide/H2O2 solution, passing the CO2-laden air through a perforated membrane installed in the gas/liquid contactor below the surface level of the aqueous alkali hydroxide/H2O2 solution, such that bubbles produced travel through said solution, and getting treated air with reduced CO2 level from said gas/liquid contactor.
Another aspect of the invention is an air purifier based on a battery consisting of CO2 adsorption scrubber and MOH/H2O2 reactor, which can improve indoor air quality by the three options set out above. In its most general form, the air purifier comprises:
a device used to move air, e.g., a blower or a fan, for supplying continuous air flow through the air purifier;
CO2 adsorption scrubber;
a gas/liquid contactor located downstream of the scrubber;
an outlet pipe to release air from the air purifier to the room; a first airflow line connecting the blower or the fan, to the outlet pipe, configured to direct incoming air stream to the adsorption scrubber, and outgoing air stream from the scrubber to the outlet pipe;
a second air flow line connecting the blower or the fan to the outlet pipe, configured to direct incoming air stream to the gas/liquid contactor, and outgoing air stream from the gas/liquid contactor to the outlet pipe; and
a third air flow line connecting the blower or the fan to the outlet pipe, configured to direct incoming air stream to the adsorption scrubber, and outgoing air stream from the scrubber to the gas/liquid contactor;
an array of valves to guide the moving air through said first, second or third air flow lines;
and optionally a heater positioned downstream to the adsorption scrubber.
A blower (1) provides airflow through the air purifier, capable of supplying volumetric flow rate of 100-2000 litre/min, adjusted to fit the selected mode of operation, as explained below. The airflow moves via, e.g., 15-50 mm diameter conduits installed in the air purifier, and is directed to the air outlet (9) via a path regulated by the states of valves (4), (5), (6) and (7), i.e., after the airflow was passed through the adsorption scrubber (2) or the gas/liquid contactor (3).
CO2 adsorption scrubbers (2) suitable for use in the invention exist in the marketplace, utilizing physisorption or chemisorption-based sorbents. A simple design is of a fixed-bed scrubber, usually a vertical cylindrical fixed-bed scrubber, as shown in
The air purifier may include a heating unit (8) positioned downstream to CO2 adsorption scrubber (2), in the form of a convection heater in which an electric heating coil is installed, operating at 100-3000 watt. To goal served by heating unit (8) is to enable CO2 adsorption scrubber (2) to switch from adsorption to desorption, i.e., to regenerate the sorbent material after it reached saturation or nearly saturation, by passing heated air through the scrubber. Rise in temperature causes CO2 molecules to detach from the sorbent surface. In the embodiment of the invention shown in
HEPA filter (not shown) is placed downstream to blower (1) or upstream to air outlet (9). Whereas blower (1), CO2 adsorption scrubber (2) and heating element (8) are fairly conventional, the gas/liquid contactor (3) has unique configuration which was described in detail above.
Perforated membrane is mounted at the lower part of the reactor, below the surface level of the MOH/H2O2 aqueous solution. One useful design of the perforated membrane is shown in
The unique geometrical motifs of membrane (836) and their useful effect are perhaps better illustrated in
Turning back to
In the variant of
The upper portion of the gas/liquid contactor (870) consists of a storage unit which includes three concentric containers, as follows: Cartridge A container (826) for the alkali hydroxide (NaOH, KOH or both, (in a tablet form), water container (847), and H2O2 container (cartridge B) (828). Cartridge A is divided into a plurality of column cylinders (826a), each containing a plurality of tablets. In an embodiment of the invention, the plurality of column cylinders (826a) are arranged in a revolving drum (845). To add MOH tablet to the reaction zone, a motor (not shown) rotates the drum 845 to angularly position a tablets' column (826a) above opening accessing the reaction zone, enabling one or more tablet(s) to fall into the reaction zone (850). Hydrogen peroxide is supplied using a pump, via pipe (828p), below the level of the solution (838). Demister (846) is also included.
For example, the weight of each tablet may be about 5 to 100 g, e.g., from 15 to 30 g, and 2 to 100 tablets may be included within cartridge (826a). The water container may contain 1 to 10, e.g., 2 to 6 liters, and the hydrogen peroxide container may include between 250 ml and 10 liter.
Turning back to
According to the first mode of operation, blower (1) supplies airflow through CO2 adsorption scrubber (2) and moves depleted-CO2 airflow which exists the scrubber via air outlet (9) to be reintroduced into the room, by keeping two-way valves (7) and (5) open and two-way valves (6) and (4) closed. The air purifier switches to such mode of operation in response to detecting increased CO2 levels in the room, or is programmed to operate likewise during time periods at which relatively high CO2 levels are anticipated, e.g., when a large number of attendees is expected, such as when a meeting takes place in the room. Because only the CO2 adsorption scrubber is at service while the gas/liquid is disconnected, the air purifier can operate with the blower (1) supplying airflow at a fairly high volumetric flow rate, over short time periods, i.e., a couple of hours or so. When the sorbent material becomes saturated, or after the people (e.g., workers, meeting participants) have left the room, the scrubber regeneration phase may start, e.g., heating unit (8) is turned on so as to feed the scrubber with hot air and release air laden with CO2 through air outlet (9). It is noted that this mode of operation largely deals with peak CO2 levels in the room, to produce and constantly reintroduce CO2-deplated airflow to the room when it occupied by people, without chemically eliminating the CO2 molecules.
According to the second mode of operation, blower (1) supplies airflow through gas/liquid contactor (3), i.e., bypassing scrubber (2) and moves depleted-CO2 airflow which exists the gas/liquid contactor (3) via air outlet (9) to be reintroduced into the room, by keeping two-way valves (6) and (4) open and two-way valves (7) and (5) closed. Volumetric flow rates received by the gas/liquid contactor are generally lower than those received by the scrubber, just holding CO2 temporarily in the scrubber (2).
According to the third mode of operation, blower (1) supplies airflow through CO2 adsorption scrubber (2) and moves depleted-CO2 airflow which exists the scrubber via air outlet (9) to be reintroduced into the room over a period of time t1 during which the MOH/H2O2 reactor (3) is at rest, by opening two-way valves (7) and (5) and closing two-way valves (6) and (4). During t1, CO2 is captured and held in the scrubber but after a while the MOH/H2O2 reactor enters into service. That is, CO2 is discharged from the scrubber (2) and is directed to, and mineralized in, the MOH/H2O2 reactor (3), by keeping two-way valve (7) open, turning on the heater to supply hot air thereby promoting the desorption process of the CO2 molecules from the sorbent in scrubber (2), to produce CO2-laden airflow. Two-way valve (5) and (6) are closed whereas two-way valve (4) is open, such that the CO2-laden airflow is passed through gas/liquid contactor (3).
CO2-laden air delivered to gas/liquid contactor (3) over a period of time t2, and is forced to flow across the membrane (236) to create bubbles which are caused to travel through the alkali hydroxide solution (e.g., NaOH or KOH, or their mixture), to which H2O2 stream is periodically or continuously added (for example, by injection beneath the level of the alkali hydroxide solution, in close proximity to the perforated membrane, i.e., in the vicinity of the perforations). Concentration of the alkali hydroxide solution varies from 5% to 481-50% by weight, e.g., from 10 to 48%-50% by weight. The concentration of the hydrogen peroxide solution added to the alkali hydroxide solution is from 3%, 4%, or 5% up to 35% by weight, e.g., from 10 to 30% by weight. Acceptable addition rate of the H2O2 stream may vary from 0.01 ml/min to 10 ml/min, e.g. up to 2, 3 or 4 ml/min. The volumetric ratio between the solutions in the range of 2:1 to 10:1 in favor of the alkali hydroxide solution. In the combined mode of operation (CO2 capture in scrubber (2), CO2 mineralization in reactor (3)), t1<t2, that is, the scrubber captures CO2 during relatively short time periods at CO2 peak hours, whereas reactor (3) runs the chemical elimination of CO2 with low volumetric flow rate over an extended time period.
The goal of the study was to test the ability of the aqueous NaOH/H2O2 reagent to remove formaldehyde vapors from air that is passed/bubbled through the reagent and decompose the formaldehyde, challenging characteristic formaldehyde indoor loading and maintaining adequate formaldehyde conversion rates over a couple of hours.
The experimental set-up is shown in
The formaldehyde solution was vaporized using hot plate (2) with an average temperature of 35° C. and the vapors were led to reactor (4). The peristaltic pump (3) used was operated at 1 m3/min flow rate. The formaldehyde concentration in the incoming stream was adjusted to 0.2-0.3 mg/m3 in air, representing typical contamination level in residential areas, based on WHO guidelines for Indoor Air Quality. A pair of formaldehyde detectors (5-formaldemeter htv-m, manufactured by PPM technology Ltd., UK) connected to the incoming (contaminated) and outgoing (purified) streams were used to measure the concentration of formaldehyde, respectively.
Results of characteristic experiments are shown graphically in
The goal of the study was to test the ability of the aqueous NaOH/H2O2 reagent to remove CO2 from air that is passed/bubbled through the reagent, when the air is loaded with low CO2 concentrations, challenging characteristic CO2 indoor loading and maintaining adequate CO2 conversion rates over a couple of hours.
The experimental set-up is shown in
CO2 levels in the incoming and outgoing streams were recorded continuously over forty minutes. The results are presented graphically in
Reaction of CO2 with alkali hydroxide alone would merely result in formation of the corresponding carbonate, as shown by the following reaction equation:
CO2+2MOH→M2CO3+H2O
In contrast, reaction of carbon dioxide with the superoxide leads to formation of oxygen:
2MO2+CO2→M2CO3+1.5O2
Hence, the involvement of the superoxide radical in decomposing of CO2 is demonstrated by evolution of O2. That is, enrichment of the outgoing air stream with oxygen. Oxygen levels in the incoming and outgoing streams recorded over forty minutes indeed indicate oxygen evolution and creation of oxygen-rich outgoing air stream, as shown by the O2 concentration versus time plot of
The goal of the study was to investigate the biocidal action of NaOH/H2O2 reagent on contaminated air, that is, to achieve reduction of microbial load of indoor air, e.g., by removing bacteria such as Micrococcus luteus, Bacillus and Clostridium. The initial load was 1*108 CFU/ml for each of the bacteria species tested (which is approximately equal to 400 CFU/plate contaminated air).
The Experimental set-up is shown in
Biocide contact time was fifteen minutes. A sealed container accommodating six petri dishes was used to receive the treated air existing reactor (4) after the fifteen minutes elapsed. It was found that 15 minutes of exposure to the superoxide radical (active solution) achieved reduction of bacteria concentration to 2 CFU/plate, indicating conversion rate of 99.51.
Experimental Set-Up
The experimental set-up is shown in
(A) a mixing unit, where an air stream is loaded with biological contamination.
(B) a treatment unit, i.e., a gas-liquid contactor, where the biologically contaminated air stream is treated with the aqueous MOH/H2O2 solution.
(C) a filtration and sampling unit, where condensable samples are collected; the so-formed solutions are then analysed (to count the microorganisms that survived the treatment).
The Mixing Unit (A)
Air stream from an air compressor (1) is passed through an air filter (2) before it enters a mixing chamber (4) at a pressure of 5 bars (flow rate of about 100 L/min). The air feed line is equipped with a regulator and a flowmeter (3) to adjust the air flow rate. Syringe pump (7; NE-300 Just-Infusion™, by New Er Pump Systems Inc.) delivers a microbial suspension to a bioaerosol generator (6; Blaustein atomizer (BLAM), a multi-jet model by CH technologies), where it becomes small and light enough to be carried on air. The BLAM atomizer is installed inside mixing chamber (4), discharging the bioaerosol at the lower portion (5) of mixing chamber (4), at a flow rate of 6 L/min, where the bioaerosol is loaded onto the compressed air fed to chamber (4), creating biologically contaminated air stream. Chamber (4) is also provided with a jet nozzle port (not shown) to introduce a disinfectant (6-10% hydrogen peroxide solution) and a secondary air stream, creating a disinfectant aerosol to clean the interior of chamber (4) between the tests. An outgoing, biologically contaminated air stream flows from chamber (4) to the treatment zone at about 106 L/min.
The Treatment Zone (B)
A reactor, i.e., a gas-liquid contactor, where the biologically contaminated air is mixed with the aqueous reagents MOH/H2O2, is indicated by numeral (8). Reactor (8) is tubular in shape (inner diameter: 9 cm; height: 40 cm). 5 mm thick stainless steel membrane (9) is mounted horizontally inside the reactor, about 2.5 cm from the bottom the reactor. The pore size of the membrane was 147 μm; centre to centre distance between adjacent pores is ˜50 μm. Sodium hydroxide (30% by weight solution) and hydrogen peroxide (10%-30% by weight solutions) are held at tanks (11) and (12), and are supplied to reactor (8) using peristaltic pumps operated under controllers 15 and 16. The NaOH and H2O2 aqueous streams enter the reactor (8) through openings located at the lateral surface of the reactor, below the level of the membrane (9). A third peristaltic pump C (not shown) is installed to discharge the exhausted aqueous reagent from the bottom of reactor (8) to a waste tank (not shown). Numeral (10) indicates the surface level of the aqueous reagent added to the gas-liquid contactor (8). An outgoing disinfected air stream (13) flows to the filtration and sampling unit.
The Filtration and Sampling Unit (c)
The filtration and sampling unit (3) consists of a dry filter air sampler (14); ACD-200 Bobcat). The air effluent of reactor (13) is passed through the Bobcat sampler (controlled by (17)) which generates liquid samples for analysis. That is, the collected fluid is withdrawn from the Bobcat sampler and samples (5-7 ml) are incubated to detect and count the microorganism. The experimental set-up is mounted inside a hood, such that air sampler (14) is fed with the treated air stream (13) delivered from reactor (8) with minimal ambient air interference.
Experimental Protocol
The strain of bacteria chosen for the tests was Kocuria rhizophila (ATCC 9341). It is readily visible when grown on agar plate, owing to its spherical morphology and intense yellow color. TSB was used as a culture broth to grow the bacteria (overnight, at 30-35° C.).
Each session consisted of the following experiments:
One negative control experiment, in which purified water is injected from the syringe pump (7) to the aerosol generator (6), creating a sterile aerosol that is discharged to chamber (4), where it is mixed with incoming sterile air stream. The outgoing air/aerosol stream flows to reactor (8). Reactor (8) operates under dry conditions, i.e., the air stream is not contacted with a liquid whatsoever. The aerosol moves to the Bobcat sampler (14), condensed, collected and tested for the presence of the bacteria (no bacterial growth was to be detected in a successful run).
Two or more test experiment, in which a microbial suspension is injected from the syringe pump (7) to the aerosol generator (6), creating a bioaerosol that is discharged to chamber (4), where it was mixed with incoming sterile air stream. The air/bioaerosol stream from chamber (4) flows to reactor (8); it enters reactor (8) from the bottom, flows in an upward direction across the aqueous NaOH/H2O2 solution. The outgoing, disinfected air/aerosol stream flows from the top of reactor (8) to the Bobcat sampler (14), samples are condensed, collected and tested for the presence of the bacteria. The combinations of NaOH/H2O2 aqueous solutions added to reactor (8) are tabulated below:
One positive control experiment, which only differs from the test experiment in that reactor (8) was filled with purified water in place of the active NaOH/H2O2 solution. The positive control experiment showed that the system does not block the passage of microorganism and functioned as the positive baseline to which each test was com-pared to, on each session, to evaluate the efficacy of the treatment. Positive control runs were performed once per session, usually after the test experiments.
System disinfection was performed at the beginning of each session and after each test involving the passage of microorganisms into the system (see the 6-10 H2O2 disinfectant arrangement mentioned above); i.e., reactor (8) was drained to discharge the exhausted aqueous reagent, and the system was cleaned and disinfected. Samples collected were diluted (e.g., 10−5 dilution), disposed on agar plates to enable CFU counting.
Results
The concentration and total number of CU injected to create the contaminated biological air stream and removal rates measured (expressed by log reduction units, calculated based on total CFU injected and relative to the positive control base) are tabulated in Table 2.
It is seen that the combined action of alkali hydroxide and hydrogen peroxide achieved high removal rates of the bacteria Kocuria rhizophila from air (>99.99% elimination).
The goal of the study was to evaluate the effect of direct contact of NaOH/H2O2 aqueous solution on hCoV-OC43, over different exposure times.
Pre-Test Preparations
Biological samples: A549 cells (Colon; ATCC, Cat. #CCL-185) were grown in 96-well plates (96-well plate, Greiner Bio One) in F-12K growth medium (ATCC, Cat. #30-2004) supplemented with 2 mM L-Alanyl-L-Glutamine solution (200 mM; Biological Industries, Cat. #03-022-1B), 1% Penicillin-Streptomycin solution (Biological Industries, Cat. #03-031-1B) and 10% Fetal Bovine Serum (FBS; Biological Industries, Cat. #04-127-1A), at 37° C. and 5% CO2.
Chemical samples: 300 μl of H2O2 10% solution were added to 9 ml of NaOH 30% solution, to form 9.3 ml samples of the active reagent.
Experimental Protocol
Test A: Negative Control—Cytotoxic Effect of NaOH/H2O2 Solution
Two experiments were conducted to determine the cytotoxicity of the NaOH/H2O2 solution.
In experiment 1-310 μl sterile growth medium were added to 9.3 ml of the NaOH/H2O2 solution and incubated for 60 seconds, followed by preparation of 10-fold serial dilutions (1:10, 1:100, 1:1000, 1:10000, 1:100000 and 1:1000000), and adding 150 μl/well from each dilution to the cells in 4 replicate wells.
In experiment 2-500 μl sterile growth medium were added to 500 μl of the NaOH/H2O2 solution, and incubated for 10 seconds, followed by preparation of 10-fold serial dilutions (1:10, 1:100, 1:1000, 1:10000, 1:100000 and 1:1000000) and adding 150 μl/well from each dilution to the cells in 4 replicate wells.
Test B—Antiviral Effect of NaOH/H2O2 Solution
Two experiments were conducted to assess the antiviral effect of the of the NaOH/H2O2 solution.
In experiment 1—310 μl of stock hCoV-OC43 were added to 9.3 ml of the NaOH/H2O2 solution, and incubated for 13, 30 and 60 seconds (total 3 test samples), followed by preparation of 10-fold serial dilutions (1:10, 1:100, 1:1000, 1:10000, 1:100000 and 1:1000000) and adding 150 μl/well from all dilutions produced at each incubation duration, to the cells in 4 replicate wells.
In experiment 2—500 μl of stock hCoV-OC43 were added to 500 μl of the NaOH/H2O2 solution and incubated for 2, 5 and 10 seconds (total 3 test samples), followed by preparation of 10-fold serial dilutions (1:1000, 1:10000, 1:100000 and 1:1000000) and adding 150 μl/well from all dilutions produced at each incubation duration, to the cells in 4 replicate wells.
Viral Standard Curve Preparation for Stock Titration:
Untreated hCoV-OC43 stock was diluted in 10-fold serial dilutions in sterile growth medium supplemented with 2% FBS, and 150 μl/well were applied from each dilution to the cells in 4 replicate wells.
Four (4) additional wells were used as calibration curve negative control (cNC), in which sterile medium containing no hCoV-OC43 was applied onto the cells.
The A549 96-well plate was incubated for 6 days at 35° C. and 5% CO2, and cells were daily monitored for cytopathic and/or cytotoxic effects under the microscope.
Results
Viral Standard Curve
Viable and uninfected/contaminated cells were observed in all cNC wells in both experiment 1 and 2.
In experiment 1 standard curve titration calculated using the Reed and Much titration formula was: 2.11·106 TCID50/ml.
In experiment 2 standard curve titration calculated using the Reed and Much titration formula was: 3.09·107 TCID50/ml.
The results indicate that the virus stock used in each experiment stands in the calibration range of our viral stocks and is reliable for experimentation.
Test A: Negative Control—Cytotoxic Effect of NaOH/H2O2 Solution
Cytotoxicity leading to cell death within hours was observed in both experiments for all replicates of dilutions 1:10 and 1:100. At dilution 1:1,000 and above, no cell death, and no difference in cell appearance were observed, compared to untreated cells incubated in growth medium and no chemical treatment.
The antiviral experiment was conducted accordingly, referring to the 1:1,000 viral dilution as a baseline for CPE monitoring and TCID50 calculations.
Test B—Antiviral Effect of NaOH/H2O2 Solution
No cytotoxic effect was observed for dilutions of 1:1,000 and above of the NaOH/H2O2 solution, no viral infection was observed for all test samples in all wells infected by treated virus containing these dilutions. That is, hCoV-OC43 infectivity by at least ≥99.9%, already at 2 seconds of contact with the virus. These percentages can be interpreted based on Table 5, for the calculated −3.7 viral log reduction obtained as the result for the 3 Test samples (Table 4).
Since no TCID50 could be calculated in any of the 3 test sample wells, calculation of the viral log reduction was based on the delta between the calculated TCID50 units that were inoculated (following incubation with the chemical mixture) into each well of the 1:1,000 dilutions, and the end-point viral titer obtained (0). The TCID50 inoculated into the wells was calculated based on the standard curve samples.
Legend for Table 3 and 4:
Initial viral TCID50/well: the total amount of hCoV-OC43 inoculated into the 96-well plate and onto the cells, at dilution 1:1,000 of the chemical mixture following incubation for 13, 30 and 60 seconds (Table 3), and 2, 5 and 10 seconds (Table 4) of the virus in the aqueous NaOH/H2O2 solution. This value was calculated based on the titration of the viral standard curve wells, using the Reed and Much titration formula, and normalization to the total volume inoculated into the wells following the dilution (150 μl). The initial viral TCID50/well was only calculated for the 1:1,000 sample dilutions, as up to 1:100 there was massive cell death not allowing for CPE (cytopathic effect) observation.
Observed viral TCID50: the TCID50 obtained for each sample at the experiment end-point (5 and 7 days post viral inoculations). As no CPE and infection were visible, all samples were assigned 0 TCID50.
Viral log reduction: was calculated per the 1:1,000 sample dilutions as log10 from the initial viral TCID50 per well).
In this study, a chemical mixture of 9 ml NaOH solution and 300 μl H2O2 solution was tested for its ability to hamper the infectivity of hCoV-OC43 by direct contact of the solution and virus. Results of the three tests performed, for three different contact durations, indicate that the tested NaOH/H2O2 solution abolished virus infectivity as soon as 2 seconds following the direct exposure. Since there was cytotoxic effect of the NaOH/H2O2 solution to the cells at up to 1:100 dilution, in these wells CPE observations were not possible. As to 1:1,000 dilution and above, we can conclude that the NaOH/H2O2 solution indeed reduced ≥99.9% the viral load capable of infecting the cells, compared to the load first introduced into the wells of this dilution following incubation in the mixture. This reduction can be assessed as at least −3.7 log reduction in hCoV-OC43 virus infectivity.
The goal of the study was to examine the performance of two types of perforated membranes which differ from one another in the geometry of their holes. In one membrane, the diameter of the holes does not vary across the membrane thickness, i.e., the air flows through passages which are cylindrically in shape, with constant diameter of 600 μm. The other membrane that was tested was perforated with holes with unique geometry, as the air flows through passages consisting of a cylindrical section joining an inverted frustoconical section: to move across the membrane, the air flows through the cylindrical section, with diameter of 300 μm, then through the frustoconical section, whose small base is contiguous with the cylindrical section (they are equal in diameter). The large base of the frustoconical section, with diameter of 900 μm, is the opening of the hole in the side of the membrane facing the bulk solution.
The experimental set-up was similar to the one described in Example 2, but was larger in scale. Also, this time potassium hydroxide solution 50% was used. 1.1 L of the KOH solution was charged to a tubular reactor with diameter of 26.5 cm. The membrane tested was installed 2.5 cm from the bottom of the tubular reactor. H2O2 solution (10%) was added at a flow rate of 10 ml/hour over the test period, by intermittently operating the pump delivering the H2O2 solution. CO2 feed and its mix with an air stream to create a combined stream of 1200 ppm-CO2 bearing air were carried out as described in Example 2; this stream was fed at a flow rate of 120 L/min to the reactor, where the KOH/H2O2 reagent was held.
CO2 levels in the incoming and outgoing streams were recorded periodically over one hour by the arrangement described in Example 2, and conversion rates were calculated. The results are shown in the form of a bar diagram in
| Number | Date | Country | |
|---|---|---|---|
| 62704664 | May 2020 | US | |
| 63282322 | Nov 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/IL2021/050592 | May 2021 | US |
| Child | 17991630 | US |
