GB2426469A

GB2426469A - Cabin air purifier

Info

Publication number: GB2426469A
Application number: GB0511032A
Authority: GB
Inventors: Oluwole Shamusi Fagbemi
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-28
Filing date: 2005-05-28
Publication date: 2006-11-29
Also published as: GB0511032D0

Abstract

An air purification system that cleans air contained in a vehicle cabin or similar enclosure comprising of a series of filters 5 a compressor 6 and a membrane molecular sieve 9. The air purification system could be used to remove dust, allergens and other airborne contaminants including carbon dioxide produced by the occupants of such enclosure, thereby restoring the oxygen and carbon dioxide concentration to the level found in normal air.

Description

CABIN AIR PURIFIER

INTRODUCTION Significant effort has been directed towards the reduction of air pollution inside confined spaces for example, the cabin of motor vehicles. In fact the major vehicle manufacturers in Europe, America and Asia now include air filters/cleaners within the ventilation system of their cars. Most of this effort has been directed towards removing allergens like dust, pollen and odours. These filters are usually designed as gross particulate filters with activated carbon included to trap odours. Some of the filters are electrostatic non-woven filter media that use electric charges on the media to capture fine particulate matters. There are also small electronic devices that target fine particulate matter within the airflow system.In this application, efforts are directed not only to cleaning the air that enters the motor vehicle cabin of particulates but also enriching it by ensuring that the oxygen content is maintained at the level of outside air. The device cited in this application is an air purifier for the reduction of specific air pollutants within motor vehicle cabins and other similar enclosed structures containing humans and animals. Cabins often have two types of ventilation systems: the re-circulating and the intake system. In the intake system, cabin air is continually supplied with "outside" or "ambient" air through the vehicle ventilation system, open windows, and other openings. Ambient air entering the cabin carries along with it a variety of particulate contaminants from the environment. These contaminants have been classified as inhalable particulates (Goodish, 1991 ) and respiratory particulates (ANSI/ASHRAE, 1989). Inhalable particulates are those that are drawn into the human airways with each inhalation but are trapped on the mucous covered surface of the nose, throat and upper respiratory tract. Particles smaller than 10Microm are classified as inhalable. Respiratory particulates are all particles that can penetrate the mucus blanket of the upper respiratory tract and are deposited in the lungs.Respiratory particulates are particles less than 2.5Microm. In the re-circulating system, air within the vehicle cabin and the particulates it may contain are constantly recycled through the heating and air conditioning system. In addition, the cabin air is constantly supplied with respiratory gases particularly carbon dioxide generated by the occupants. For clarity, the term "ambient air" is used in this application to mean the air through which the vehicle is being driven while the term "cabin air" refers to air within the cabin of the vehicle. This invention addresses the purification of air, particularly in the passenger cabins of motor vehicles, but also in any confined or enclosed space that could be occupied by humans and animals. This includes homes, schools, shopping complexes, hospitals, nursing homes, health care, leisure and industrial environments. In these settings, the level of carbon dioxide is likely to rise particularly when the ventilation system is in the re-circulating mode. Why measure carbon dioxide? Carbon dioxide is a natural component of the air we inhale. The outdoor air in most locations contains about 350-400 parts per million (ppm). Higher concentrations of carbon dioxide can be found close to sources of combustion such as automobile traffic, in confined spaces occupied by humans or animals, like buildings, cars, planes, boats etc. This is because the occupants of such environments are constantly using oxygen and emitting carbon dioxide as they breathe. The average adult breath contains about 35,000 to 65,000 ppm of carbon dioxide. Without adequate ventilation, the concentration of carbon dioxide in air in a confined space soon rises while the oxygen level falls. A rise in carbon dioxide concentration in an enclosed space soon produces physiological responses in the occupants of such a space.In fact a measure of carbon dioxide concentration is used as an indication of the adequacy of a ventilation system. The international occupational safety standard limit for carbon dioxide is 5000 ppm. The table below summarises the physiological effects of various concentrations of carbon dioxide.

Although levels below 5000 ppm are considered to pose no serious health threat, it is known that individuals working in confined spaces with elevated carbon dioxide concentrations tend to report drowsiness, lethargy, and loss of concentration. No prior art device intended for vehicle cabin air purification known to the researcher has specifically targeted carbon dioxide for which the Environmental Protection Agencies or other agencies have established ambient air quality standards, and safety limits. This is not surprising in that attention has always been focussed on removing particulate pollutants and odours from air coming into the vehicle cabin. This is the first attempt to monitor the carbon dioxide concentration in a vehicle as it is being driven through urban streets.

Prior Art Patents known to the inventor that relate to air purification systems especially in the cabins of motor vehicles are described below. It should be emphasised that none of the patents below addressed the question of carbon dioxide generated by the occupants of such cabins. Most of them described the various methods of filtering and purifying air coming from outside into the vehicle cabin. (1) U.S.Pat. No 3722182 issued on 27/3/1973 to Gilbertson for an air filtering device that removes particulate matter using electrostatic plates. The device could be fitted separately within the cabin or can be connected directly to the air intake of the vehicle. (2) U.S. Pat. No. 3870495 issued on 11/3/1975 to Dixon et al., for air filters comprising of non woven fibres of wood, paper, hemp and similar compounds. (3) U.S, Pat. No. 3883637 issued on 13/5/1975 to Benedict for an air filter comprising of activated charcoal, mixture of chromium and copper oxide, chromates and dichromates for the removal of hydrogen sulfide, and other airborne sulphur compounds like mercaptans, organic sulfides and sulfoxides. (4) U.S.Pat. No. 4207291 issued on 10/6/1980 to Byrd et al. for filter comprising of a fabric impregnated with Mn02 for removing ozone from air within aircraft cabins. (5) U.S. Pat. No. 4629482 issued on 16/12/1986 to Davis described a portable air filter containing HEPA filters for removal of particulate matters in rooms. (6) U.S. Pat. No. 4658707 issued on 21/4/1987 to Hawkins et al. for an air filter and a smoke detector for use in vehicle cabins. (7) U.S. Patent No. 4722747 issued on 2/2/1988 to Ambruster described an air filter consisting of foam, activated charcoal and a pair of blowers. (8) U.S. Pat. No, 4917863 issued on 17/1/1990 to Kraw et al. described an activated carbon filter system for the removal of mercury, pathogens and other vapours from air in a dental office. (9) U.S. Pat. No. 5004487 issued on 2/4/1991 to Kowalzyk, described an air filter system that could be installed in a vehicle heating/cooling system that is pressure driven for the purification of air coming into the passenger's cabin. (10) U.S. Pat. No. 5192346 issued on 9/3/1993 to Kowalzyk for a filter similar to (9) above but employs a pleated flat filter to permit greater air flow. (11) U.S. Pat. No. 5042997 issued on 27/8/1991 to Rhodes for an environmental control system for use in buildings and consisting of a series of particulate filters and activated carbon for odour. (12) U.S Pat. No. 5221292 of 22/6/1993 to Aoyams for vehicle cabin air cleaners that consists mainly of two cleaners, one that functions at low pollution levels and the other that functions when the pollution level is high. (13) U.S Pat. No. 5879423 of 9/3/1999 to Luka et.al. for filters which can be included within the air conditioning system of a motor vehicle. The plate like filter element consisting of a carbon mat, placed between two frame parts, (14) U.S Patent application number U.S. 2004031248 of 19/2/2004 by Deharpport for a portable motor vehicle cabin air purifier made of non woven gross particulate filter media, a HEPA filter and a carbon impregnated filter. (15) EP 1433532 and EP 1433515 by Kim Jung-Ho et al of 30/6/2004 for an air purifier for removing dust, and contaminants from air using charged electrodes. As it is well known to those in the art, an air purifier is used to provide clean air after dust, bacteria and contaminants in the air have been removed. These contaminants are removed either by using filter media, ionizers, and other electronic devices. The prior art so far uses either particulate filters or electronic devices to filter the air coming into the vehicle. The draw back in this approach is that the effectiveness of the media diminishes as it fills up, and the electronic devices require frequent cleaning to prevent arcing and to minimise the intrinsic production of ozone. The present invention filters air without these disadvantages. The present invention could also be used injunction with filters and ionizers. I shall now proceed to presenting the result of the research supporting the present invention. Experimental Results [1] The results presented in Tables 1 and 2 below indicate a reduction of carbon dioxide levels to levels obtained in normal air when the present invention was in operation but values in excess of the standards when the device was not in operation. Measurements were made in a vehicle that had a filter system built into its ventilation system and were in operation during the experiments. [2] Although prior art disclosed the technology for the systematic purification of air, such technology has been specifically directed at air coming into the vehicle cabin from outside. The data presented herein (Table2) shows the effectiveness of the air purification unit in the purification of air within the vehicle. Commercially available synthetic zeolites were used as the molecular sieve in these studies. The chemical formula of zeolite that was tested is Na86(Al86S106O384). The diameter of the pore size in the zeolite crystal was 1.3nm and a total surface area of 610m .g-1. Table 1: Level of carbon dioxide in the passenger cabin of a car as it was driven through the streets of Lincoln.

Table 2.Level of carbon dioxide in the same passenger cabin as it was driven through the streets of Lincoln with the purification and oxygen enrichment unit in operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[001] The present invention provides an apparatus and methods for air purification and oxygen as set forth in the appended claims. Unique features of the invention and its advantages over other air purifiers will be obvious from the dependent claims and description which follows. [002] Embodiments of the air purification unit according to the present invention are described in details with reference to figures 1 to 3 [003] Figure 1 illustrates the process involved in producing air with reduced carbon dioxide concentration according to the present invention. The ambient air is drawn into the purification unit from the car cabin (compartment A). The air is filtered and separated into its components. Oxygen and nitrogen passes through the membrane sieve in the separator into compartment B and is recycled into the car cabin. The carbon dioxide is sent out of the car cabin through the purge line. [004] Figure 2 shows that the main body of the purification unit has a cover (1) containing air suction slits (2) through which air to be purified passes. Connected to the purification unit is a control unit (10) having a carbon dioxide monitor (11) that senses the concentration of carbon dioxide in the cabin and triggers the mechanisms for activating the air purification unit when the carbon dioxide concentration becomes higher than the preset value. Also within the control unit is a means for altering the power supply to the compressor motor and thereby adjusting the speed of operation of the compressor. [005] Figure 3 shows a cross-section of components of the air purification unit enclosed within the main body shown in figure 2. These are, a heater (3), a prefilter (4) and a series of filters of different pore sizes (5), including a desiccant filter. The filters are to remove dust and bacteria from the incoming air. The desiccant preferably comprises standard desiccants including activated alumina, impregnated alumina, silica gel. The desiccants remove water vapour and carbon dioxide from the air before it is drawn through the heater into the separation chamber (8). The heater dries the air by removing any remaining water vapour. It is conventional to remove these contaminants so as to avoid poisoning the molecular membrane sieve. [006] Also enclosed by the main body of the present invention is a compressor (6). The compressor draws the incoming air through the filters and heater. The dried air is driven through an air conduit (7) to an air tight separation chamber (8) where the air is separated by being forced through a zeolite membrane (9). The zeolite membrane serves as a molecular sieve separating the air into its component gases according to their molecular size. This technology has been used in the industrial production of nitrogen, or oxygen from air. [007] One advantage of using a sodium zeolite X membrane in this invention is that it has a low separating efficiency for separating nitrogen from oxygen. The main focus of this invention is not the separation of oxygen from nitrogen, but the separation of oxides of carbon and nitrogen from air. [008] Although sodium zeolite X is used in this example, other suitable membrane may be used. Examples of membranes that can be used include low silica -X zeolite containing one or more elements from the monovalent alkaline, alkaline earth, transitional metal and rare-earth element groups. [009] The membrane must preferably contain less than 0-0.01% total divalent cations. Exclusion of divalent cations, especially magnesium and calcium bestow on the membrane adsorbent a greater resistance to water molecules. [010] If air at a temperature of 20 degrees centigrade and a pressure of 2- 8 bars is pressed through the membrane, the permeated gas mixture containing oxygen and nitrogen is passed through the return line (12) into the car cabin This is then mixed with the air in the cabin. The rate of dilution is so fast that the net oxygen concentration in the vehicle cabin is similar to the level in unpolluted air. [011] The carbon dioxide and other gases that are unable to permeate the membrane are purged out of the chamber through the purge line (13). [012] Within the walls of the chamber (8) are two normally closed diaphragm valves (14) and (15). These valves open when the pressures in the air separation chamber reach the appropriate level to allow clean oxygen and nitrogen to be recycled into the vehicle cabin through the return line (12) and to allow carbon dioxide and other gases unable to pass through the membrane filter to be expelled from the cabin through the purge line (13). The present invention has been shown and described with two diaphragm valves, other types of valves could be used without departing from the principles and spirit of the invention. [013] Although the invention has been described with these specific embodiments, it is evident that many alterations and variations will be apparent to those skilled in the art in the light of the foregoing description. Accordingly, the invention is intended to include all of the alternatives and variations that fall within the spirit and scope of the appended claims.

Claims

1. An air purifier and oxygenator for the reduction of oxide of carbonand nitrogen and specific air pollutants within motor vehicle cabins and other similar enclosed structures containing humans and animals. The air purifier and oxygenator is characterized in having a main body through which air to be purified is drawn in and discharged; a pre-filter to trap particles larger than dust, filters to collect dust and other airborne allergens; a compressor and at least one packed bed membrane molecular sieve.

2. The air purifier and oxygenator is characterized by being a portable self-contained unit, can be operated from any accessible power source independently, or in conjunction with any heating, air conditioning or ventilation system.

3. The air purifier and oxygenator of claim 1 is designed to purify only air contained in the motor vehicle cabin or similar enclosure to the exclusion of air entering said cabin or similar enclosed structure from areas external thereto.

4. The air purifier and oxygenator of claim 1 permitting a method of removing specific pollutants from air within a motor vehicle cabin or similar enclosed structure, characterized by the steps of passing the air through a series of filters of different pore sizes, compressing the filtered air through a molecular sieve thereby enabling the separation of carbon dioxide and other oxides of carbon or nitrogen from oxygen and mtrogen by adsorption.

5. The air purifier and oxygenator of claim 1 is further characterized in having air inlet and air outlet apertures to at least one of which is attached an air conduit, a compressor in fluid connection with said air conduit for the purpose of drawing air into said air conduit through said air inlet and transmitting air out of said air conduit through said air outlet apertures. Also in fluid connection with the air conduct are purge and return lines containing pressure sensitive valves.

6. The air purifier and oxygenator of claim 1 having an air inlet and an air outlet of claim 5 being in direct fluid connection with the interior of said motor vehicle cabin or similar enclosed structure.

7. The air purifier and oxygenator of claim 1 has a power means for connecting to a power source for operating said compressor from within and/or without said cabin or similar enclosed structure.

8. The air purifier and oxygenator of claim 1 wherein the gas separation means is comprised of one or several zeolite X adsorbers, operating according to the pressure swing adsorption cycles.

9. The air purifier and oxygenator of claim 1 is further characterized in comprising a synthetic zeolite X adsorber containing one or more elements from the monovalent alkaline, alkaline earth, transitional metal and rare-earth element groups used as the molecular sieve.

10. The air purifier and oxygenator, wherein the zeolite X adsorbent membrane according to claim 9, has a granulometry less than 1.00 mm and the diameter of the pore size in the zeolite crystal is 1.3nm and a total surface area of 610m .g-1.

11. The air purifier and oxygenator of claim 1 is further characterised by having a temperature regulated heater, to raise the temperature of the air coming through the inlet aperture of claim 5 to between 10 and 60 degrees centigrade.

12. The air purifier and oxygenator of claim 1 is further characterised by having a control unit to which is linked a carbon dioxide sensor, a thermostat and a control circuit for the operation of the air purifier.

13. The air purifier of claim 1 is further characterized in that said control unit includes means for adjusting the level of power provided to the compressor motor to desired values, whereby the speed of operation of said compressor will be adjusted to desired values.

14. The air purifier and oxygenator according to claim 1, having a means of securing the main body to the motor vehicle cabin or similar enclosure and at least one carrying handle which can be attached to the main body.