Abstract:
An apparatus and method for sterilizing airborne pathogens and reducing airborne pollutants in air for buildings, aircraft, or other structures. The apparatus is capable of high air flows and is integrated with an efficient air heating/cooling system. High fields are produces by a static, preferably infrared, field combined with a high intensity microwave field. This combination allows fields to develop that are high enough in intensity to kill pathogens and dissociate contaminant molecules. The heat produced by the field generators is used to operate an absorption chiller to cool and dehumidify, or alternatively heat, the sterilized air before it is returned to the building or structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of the filing of U.S. Provisional Patent Application Ser. No. 60/474,006, entitled “Combined High Energy Field Hybrid Air Sterilizer and Absorption Chiller”, filed on May 28, 2003, and U.S. Provisional Patent Application Ser. No. 60/477,316, entitled “High Energy Field Quantum Air Sterilizer”, filed on Jun. 9, 2003, the specifications of which are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention (Technical Field)  
           [0003]    The present invention relates to a method and apparatus for cleaning and sterilizing air while providing for efficient heating or cooling and dehumidification.  
           [0004]    2. Background Art  
           [0005]    Note that the following discussion is given for more complete background of the scientific principles and is not to be construed as an admission that such concepts or publications listed are prior art for patentability determination purposes.  
           [0006]    The need for cost effective air quality improvement that can be used in new construction or existing heating cooling and ventilation equipment systems is seen in almost every level of public and private dwellings in modem society. Schools, hospitals, doctors&#39; offices, airports, office buildings, sports and events stadiums are all places where people interact enabling disease to be spread through the air or by contact or close contact. The ability to eliminate airborne pathogens like Legionnaire&#39;s disease, micro-bacterium tuberculosis, hepatitis and influenza and SARS with cost effective air sterilization and humidity control in a single high volume heating, cooling and ventilation package that is easily installed and maintained will reduce healthcare costs and lost productivity from sickness caused by airborne contamination. The use of antibiotics by the agricultural industries worldwide for disease control in milk and meat production increases the threat of highly contagious diseases entering our populations that may be resistant to treatment by current or future antibiotics. Applications which benefit from destroying airborne pathogens include pharmaceuticals, food processing, water filtration, public buildings, hospitals, microelectronics manufacturing, biotechnology, breweries, food sterilization, clean rooms, greenhouses, isolation rooms, airports, aircraft, HVAC air-handling, bioremediation, livestock barns and bio-security.  
           [0007]    In addition, airborne inorganic and organic pollutants such as carbon monoxide and volatile organic compounds (VOCs), including hexane, dihydrofuran, benzene, and methyl acetate, are prevalent in most buildings, airplanes, and other enclosed or semi-enclosed structures, causing illness and lowering worker productivity. Thus there is a need for a high air flow device to simultaneously reduce or eliminate both airborne pathogens, including resistant strains, and contaminants such as VOCs for buildings, while simultaneously providing energy efficient temperature and humidity control.  
         SUMMARY OF THE INVENTION  
       Disclosure of the Invention  
         [0008]    The present invention is an apparatus for sterilizing air which comprises a static field generator, two or more microwave generators preferably comprising magnetrons, a sterilization cavity, and an air temperature control system, wherein the air temperature control system is heated by the static field generator and the microwave generators and a superposition of electric fields produced by the microwave generators is modulated in order to produce high electric fields in air flowing within the cavity. The static field generator preferably comprises an infrared generator, which preferably comprises one or more quartz tubes. The tubes may be turned on or off independently. A combined field density of between approximately 9 watts per cubic centimeter and approximately 13 watts per cubic centimeter, including approximately 13 watts per cubic centimeter, is created in the air. The two or more microwave generators are preferably situated so that magnetic fields produced by the generators cancel each other out within the cavity. They apparatus can sterilize large volumes of air flowing through the cavity, at a rate of up to approximately 250,000 cubic feet per minute (CFM). A pathogen or contaminant in the air preferably flows through the cavity in no less than approximately six milliseconds. The air temperature control system preferably comprises an absorption chiller, which preferably comprises a coolant selected from the group consisting of ammonia and lithium bromide. The air temperature control system preferably heats, cools, or dehumidifies the air.  
           [0009]    The present invention is also a method of sterilizing air comprising the steps of applying a static field, preferably an infrared field, and two or more modulated microwave fields to the air, transferring excess heat to an air temperature control system, and varying a temperature of the air. Modulation of the microwave fields preferably produces a combined field density of between approximately 9 watts per cubic centimeter and approximately 13 watts per cubic centimeter, including approximately 13 watts per cubic centimeter, in the air. The air temperature control system preferably comprises an absorption chiller. The varying step preferably comprises heating, cooling or dehumidifying the air, which preferably is flowing at a rate of up to approximately 250,000 CFM.  
           [0010]    An object of the present invention is to provide an energy efficient, high volume combination air sterilizer/cooler/heater with low capital and operating costs, and having greater durability than compressor style refrigeration units using refrigerants that can harm the environment.  
           [0011]    An advantage of the present invention is its safe, efficient all electric design.  
           [0012]    A further advantage is that the staged variable load capacity of the present invention can easily match the HVAC requirements of a facility, including built-in humidity control.  
           [0013]    Yet a further advantage is the modular design and small footprint of the present invention, which allow for semi-portable applications since the unit is totally self-contained. Multiple units can be added to serve a wide range of building loads and even increase reliability.  
           [0014]    Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The accompanying drawings, which are incorporated into and form a part of the specification, illustrate several embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating a preferred embodiment of the invention and are not to be construed as limiting the invention. In the drawings:  
         [0016]    [0016]FIG. 1 is a schematic of the combined high energy field air sterilizer/absorption chiller/heater of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     Best Modes for Carrying Out the Invention  
       [0017]    The present invention is a combined high energy field hybrid air cleaner, sterilizer and absorption chiller/heater for use with buildings or other structures.  
         [0018]    As used throughout the specification and claims, the term “pathogen” means microbe, mircoorganism, germ, virus, bacterium, allergen, fungus, pollen, spore, mildew, mold, protozoa, cyst, parasite, and the like.  
         [0019]    As used throughout the specification and claims, the terms “contaminants” or “pollutants” mean organic or inorganic compounds such as VOCs, oil mist, NOx and other nitrogen oxides, carbon monoxide, carbon dioxide, sulfur oxides, and the like.  
         [0020]    As used throughout the specification and claims, the term “sterilize” and variants thereof mean to render a majority of pathogens inactive, as well as to significantly reduce the concentration of pollutants and/or contaminants (including but not limited to VOCs), and the like.  
         [0021]    The present invention requires the convolution of at least two high energy fields. Air passing through the system is exposed to a static, preferably infrared (IR) field in addition to a pulsed field, preferably in the microwave range. This convolution dramatically increases the intensity of the field, thus producing excited molecular events resulting in sterilization of the pathogens in the air, as well as dissociation of contaminants. Specifically, high intensity slow microwaves excite the contaminant molecules and pathogens, which ordinarily would reemit heat (which is the normal operation of a microwave oven). The static IR field suppresses this thermal reemission, creating an avalanche pulse which creates an electric field with a high enough intensity to dissociate contaminant molecules. This pulse modulates the microwave field. The avalanche pulses preferably have a rise time of approximately 20 ns, and the pulse width is preferably approximately 5 ns, depending on air flow. The pulse frequency depends on the impedance of the sterilization cavity, which depends on the constituents of the air in the cavity. Typical pulse frequencies range up to 100 ns. The combined fields sterilize resistant strains of pathogens because cell structures are deeply penetrated by the fields, resulting in irreversible thermal molecular and cell expansion by as much as 400%. This produces a pathogen reduction between approximately 99.9% and 99.999%. A combined field density of from approximately 9 wafts per cubic centimeter to about 13 wafts per cubic centimeter is required to dissociate contaminants such as VOCs, NOx, and CO; approximately 13 wafts per cubic centimeter is required to sterilize pathogens. These field levels can be achieved by adjusting the power of each of the fields. For example, a 10 kW microwave power convolved with the infrared field strength disclosed herein will provide the necessary field density to achieve sterilization.  
         [0022]    [0022]FIG. 1 is a schematic depiction of a preferred embodiment of the present invention. Outside air and/or return air from the building enters the apparatus through duct  240 , and preferably passes through pre-filter  260  which filters out all particulates over approximately 150 microns. Alternatively, filters with Other particulate size ratings may be employed. Air  230  then passes to air sterilization cavity  170  comprising a static infrared radiation field generator, preferably comprising infrared quartz tube array  220  which preferably surrounds the bottom portion of absorption generator  60  and transfers the IR energy to air  230 . Gold plated quartz tube elements are preferably utilized due to their long life and easy replacement. In a preferred embodiment twelve tubes are arrayed along the cavity, spaced evenly. It is preferable to use 900 waft single element tubes, having a temperature range up to 145° C. each; alternatively, 1500 waft dual element tubes may be used if higher fields are desired. Thus temperatures up to 1700° C., or higher if desired, may be reached in the cavity. However, due to rapid air flow the temperature of the air passing through the cavity rises less than or equal to only about 10-15° C. from inlet duct  240  to the cavity exit. A high density infrared field (95% efficient) is preferable to insure decontamination. Any frequency radiation, such as ultraviolet, may be used instead of infrared radiation, as long as the field is substantially static or constant in intensity. Applying a static field to air  230  has the additional advantage of rendering water vapor in air  230  transparent to microwave radiation; that is, preventing thermal reemission and thereby increasing efficiency.  
         [0023]    Air  230  is also treated with microwave radiation produced by at least one permanent magnet type magnetron. Preferably two magnetrons  90 ,  150  are employed along cavity  170 . Their relative locations are preferably chosen so that the produced electric fields superpose but the magnetic fields cancel out. (Coupled magnetic fields would limit the attainable maximum superposed electric fields.) Thus the electric field in cavity  170  is maximized, forming maser-like standing or slow waves in cavity  170  without requiring a tuned cavity. If more power is required, more magnetrons may be employed. Although any frequency may be used in the practice of the present invention, as a practical matter regulatory issues currently limit the possible frequencies to only a few. Which frequency is chosen depends on the required airflow. To accommodate more airflow cavity  170  must be larger, thus the microwave wavelength must be longer to efficiently couple microwave energy into cavity  170 . In addition to satisfying airflow requirements, the size of the cavity is chosen to ensure that transit time of air  230  through cavity  170  is no less than 6 milliseconds, which is the minimum time for the pathogens and contaminants to absorb the radiation and thus be sterilized and/or dissociated. Table 1 summarizes this relationship.  
                                     TABLE 1                           Approx. Cavity   Microwave       Air Flow (CFM)   Diameter (cm)   Frequency (GHz)                                250,000   117   0.915       27,000   22   2.45       3,000   6   5.8       150   1   24.125                  
 
         [0024]    The microwave radiation section preferably comprises a low air restriction cavity design. The exposure of the air  230  to microwaves may occur before, after, and/or substantially simultaneously with the application of the infrared radiation. Magnetrons  90 ,  150  are powered by back plates  120 ,  130  via high voltage lines  125 ,  127  and preferably couple to cavity  170  via waveguides  80 ,  160 , which are impedance matched to cavity  170 . Borosilicate hot mirrors  70 , which are transparent to microwave radiation, are preferably installed to prevent heat from cavity  170  from affecting magnetrons  90 ,  150 . Tuning of coupled microwaves by stub tuners is preferred, although any tuning method may be used. Optional instant on/off operation allows for efficient and safe operation, as do optional safety interlocks to defeat the field if access covers to the microwave cavity are opened. The system is controlled and monitored via processor  250 .  
         [0025]    Sterilized air  190  optionally passes from cavity  170  over or through an infrared concentration grid (not pictured) if a desired airflow increase reduces the time air  190  has spent in cavity  170  to less than approximately six milliseconds. Air  190  then passes over coils  200  containing chilled water, thus both cooling and condensing moisture in air  190 . The chilled water is preferably provided by an absorption chiller system, such as those known in the art, which takes advantage of heat produced by the air sterilization system. Other refrigeration systems may alternatively be used. Excess heat from both the infrared quartz tubes and the microwave units heats generator  60 . By using heat that would otherwise be wasted, system efficiency is dramatically increased. (The actual efficiency of heat transfer from the microwave units will depend on the air density during operation.) Generator  60  contains at least one coolant mixture, preferably comprising liquid ammonia such as R-717, or alternatively lithium bromide; however, the mixture may comprise any coolant known in the art. Preferably the coolant is mixed with water to form a mixture comprising one-third coolant and two-thirds water. R-717 is preferred when dehumidification is a high level requirement, since ammonia units can reach colder chiller temperatures. When using ammonia as the coolant, chilled water in coils  200  is sufficient to cool air  109  to 42° F. Otherwise, features of ammonia based systems are similar to those of lithium bromide chillers.  
         [0026]    The coolant mixture is heated in generator  60 , causing the mixture to separate. Pump  50  pumps the liquid coolant from generator  60  to absorber  40 , while the differential pressure in the system drives the water remaining in generator  60  to preabsorber  180 . In absorber  40 , which functions as a heat exchanger, hot water circulated from coils  200  is cooled by evaporation of the liquid ammonia. This chilled water then is circulated through self-contained chilled water system  205  to coils  200  which cool air  190 . The resulting warmed water is circulated back to absorber  40 . The chilled water preferably comprises ethylene glycol which protects against freezing and helps prevent corrosion. The gaseous ammonia optionally circulates to heat exchanger  30  which lowers its temperature with cooling air  15  circulated by condenser fan  10 , thus utilizing more of the available cooling air, thereby increasing efficiency of the system. The ammonia then circulates to preabsorber  180  which preferably comprises a cooling coil from condenser  140 , where the ammonia is precooled so it may be more efficiently absorbed back into the water which came from generator  60 . Then the mixture proceeds to condenser  140  where it is cooled further by cooling air  15  circulated by condenser fan  10  powered by motor  20 , and then is circulated back to generator  60 . Condenser  140  typically requires approximately 6000 SCFM of air flow provided by condenser fan  10 , which is preferably adjustable based on outside ambient conditions. Pump  50  may optionally be located between condenser  140  and generator  60 .  
         [0027]    Air  190  is discharged out of the present apparatus and returned into the building intake duct by fan  210 . In addition to cooling the air, dehumidification is also provided, both by condensation occurring as air  190  passes over chilled water coils  200  but also optionally as air  190  passes through a standard dehumidification impact pad  100  on its way to being discharged into the building. Pad  100 , which is preferably comprised of stainless steel, rapidly removes moisture droplets from air  190 , and the droplets preferably collect in drip pan  110 , which optionally comprises a drain. Dehumidification is efficient enough so that relative humidity of air discharged to the building return is approximately 40% when the ambient relative humidity is 70% or greater. Return air can be controlled to full or partial vent or makeup. The absorption chiller preferably uses a staged infrared power input to provide dehumidification and cooling over a wide ambient temperature range. That is, when cooling needs are reduced, some of the quartz IR elements may be individually turned off, resulting in greater energy savings than currently used units, which can only be cycled completely on or completely off. In cold weather, heating the air is also possible by preventing evaporation of the ammonia in absorber  40 . In this case, the hot liquid ammonia in absorber  40  heats the water, which then circulates to coils  200  and heats air  190 . In addition, as discussed above, air  190  exiting cavity  170  has already been heated by up to about ten degrees over the temperature of inlet air  230 . The present invention has the advantages of high efficiency and stable chiller operation even at extreme temperatures of −12° C. to +45° C. for chiller operation and −20° C. for heating cycles.  
         [0028]    The total system is currently designed for total electric operation and is mounted outside for proper condenser air flow with duct access available for discharge and return air application. In order to improve energy efficiency, the operation of the combined fields can be programmed to reduce energy consumption once the air in the building has been recirculated enough so that the pathogen and contaminant concentration of the air has been reduced to the desired level. An advantage of the design of the present invention is that semi-portable wheel around or roller type embodiments with an air flow capacity in the 1500-10,000 CFM range can be used to quickly control air contaminants where existing air systems are inadequate. Multiple units of the present invention may be arrayed for use in intermediate and large mechanical systems requiring hundreds of tons of air capacity.  
       EXAMPLE 1  
       [0029]    A preferred embodiment of the present invention was tested for contaminant reduction. Concentrations of Methyl Ethyl Ketone (MEK), a highly stable VOC used as a paint solvent, were collected by EPA method 18 and tested in accordance with EPA TO-14 and TO-25A at temperatures not exceeding 112° F. Reductions of 60% of the MEK concentration confirmed the low temperature VOC destruction capabilities of the present invention. E-com KL testing verified 100% reduction of 1870 ppm oil mist (comprising 46 and 68 wt hydraulic oil) contamination of air with a temperature raise from 88° F. of the ambient air to 100° F. for the air discharged from the sterilization cavity. A reduction of 50% of 250 ppm CO at air flow volumes of 14,500 SCFM, and 80% reduction of 10 ppm input NO at 6000 SCFM, with both tests performed below 104° F., were achieved. A typical temperature rise across the system (from the intake air to the air exiting the sterilization cavity) is 12° F. from 88° F. to 100° F. at air flows of 27,000 SCFM. It was estimated that 2° F. of the rise was due to blower compression; 6° F. were attributed to the microwave field; and the remaining 4° F. was due to the IR tuned static field.  
         [0030]    Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover all such modifications and equivalents. The entire disclosures of all patents and publications cited above are hereby incorporated by reference.