Title of Invention

AN AIR TREATMENT SYSTEM AND A METHOD FOR TREATING AIR IN AN ENVIRONMENT

Abstract A method and apparatus for reducing air contamination using a contaminant adsorbent to remove contaminants from air, and a nonthermal plasma to desorb and oxidize or detoxify the contaminants. The adsorbent may be comprised of a unique combination of a zeolite with a material having a high dielectric value. The power supply for the nonthermal plasma reactor is designed to seek and operate at the system resonant frequency. In one embodiment, the adsorbent material is separated from the nonthermal plasma reactor. In this embodiment, heat is applied to the adsorbent material to thermally desorb contaminants during a desorption/regeneration phase. Air is recirculated within the system to move desorbed contaminants from the adsorbent material to the nonthermal plasma reactor for decomposition. The recirculating air repeatedly moves contaminants through the reactor until they are destroyed or the desorption/regeneration phase is complete. (FIG. - 1)
Full Text AN AIR TREATMENT SYSTEM AND A METHOD FOR
TREATING AIR IN AN ENVIRONMENT
This application claims the benefit of U.S. Provisional Application No.60/401,665 filed
August 7, 2002.
Field of the Invention
The present invention relates to an air treatment system and a method for treating air in
an environment.
Background of the Invention
Numerous air purification systems are described in the literature and available in the
marketplace. These systems rely on various techniques to remove and detoxify waste gases,
volatile organic compounds, odors, nitrogen oxides, sulfur oxides, toxic gases, etc.,
hereinafter referred to as contaminants. These systems rely on a variety of methods, such as
combustion, adsorption, catalytic or nonthermal plasma processes to remove airborne
contaminants.
The combustion systems are the simplest in principle, and comprise primarily of
heating the air, causing thermal decomposition or combustion of the airborne contaminants.
However, this method is uneconomical because it requires large amounts of energy to
effectively remove the contaminants from the air. This method also can create large amounts
of thermal pollution.
The adsorption method relies on the use of an adsorbent material to capture airborne
contaminants. However, this method requires the frequent replacement or regeneration of the
adsorbent material, resulting in higher operating costs for these systems.
The catalytic method relies on the use of catalysts to accelerate the chemical reactions
that convert airborne contaminants into relatively harmless chemical components. However,
the catalytic method generally requires impracticably high energy requirements when the
concentration of the contaminants are low. Furthermore, the catalysts used by these systems
may be subject to poisoning by the contaminants, resulting in a substantial decline or
complete loss of catalytic function.
Typical nonthermal plasma systems rely on the use of a nonthermal plasma to treat air
streams that contain contaminants. A nonthermal plasma is a high voltage electrical
discharge between the two electrodes. This discharge creates high energy electrons in the air,
which collide with gas molecules and create free radicals. These free radicals oxidize the
contaminants in the airstream. Most of the reactants are produced from oxygen, producing a
number of different oxygen species. However, free radicals are also formed from nitrogen
and water vapor that may be in the airstream. Because most of the energy consumed by the
nonthennal plasma systems is used to create high energy electrons, the temperature of the
airstream being treated by these systems remains essentially unchanged. The high voltage
that powers the plasma can be in the form of an alternating current, direct current or pulsed
current, with a rapid rise time pulse in a pulsed current having the highest performance.
Generally, a nonthermal plasma air treatment system is comprised of a nonthennal
plasma reactor and a means for moving air through the reactor. The nonthennal plasma
reactor is comprised of a plurality of opposing electrodes, and is generally manufactured
according to one of two configurations: corona discharge or dielectric barrier discharge.
Corona discharge reactors use bare electrodes and the nonthermal plasma is created between
them. The dielectric barrier reactor has a dielectric coating on the one or both electrodes, or
has a packed bed containing a dielectric material between the electrodes.
Nonthermal plasma systems can suffer from several deficiencies, such as oxidation
by-products, ozone production, and high electrical energy requirements. Oxidation by-
products are the result of incomplete oxidation, and new contaminants can be formed in the
airstream, defeating the purpose of the system. Ozone is thought to be harmful, so the
creation of ozone also may defeat the purpose of these systems. Finally, the high energy
requirements for many nonthermal plasma systems render these systems impracticable.
As noted above, nonthermal plasma is typically created by applying high electrical
power to a plasma reactor. Some conventional nonthermal reactors require hundreds of
joules of electric energy to treat a liter of air. This need for large amounts of electrical energy
presents a significant challenge to conventional nonthermal plasma systems. The power
supply issues are further complicated by the fact that the parameters necessary to enable and
control nonthermal plasma can vary dramatically not only from reactor to reactor, but also
from time to time within the same reactor. For example, for a nonthermal plasma system that
includes a packed bed of dielectric material between the electrodes, the conductivity of the
bed of dielectric material can vary as a result of changes in humidity in the air being treated
and changes in the quantity and type of contaminants in the bed. These variations can also
result in significant changes in the impedance of the bed. As the conductivity and impedance
of the bed changes, the amount of power required to generate and maintain nonthermal
plasma also changes.
Another known problem associated with nonthermal plasma reactors is caused by
"streamers" that can form in the reactor. Streamers are essentially self-propagating electron
streams that, if left unchecked, may transition into an arc and/or cause the nonthermal plasma
to transition into a thermal plasma condition. This can have significant adverse effects on the
bed and on the performance of the system. To avoid arcing or a transition to a thermal
plasma condition, the streamers must be terminated or quenched quickly after being formed.
To achieve this function, conventional nonthermal plasma reactors are required to include
relatively complex external or self-quenching mechanisms.
It is therefore an object of the present invention to provide an air treatment system
that remedies some or all of the deficiencies found in the systems described above.
Summary of the Invention
The present invention provides a method and apparatus for the effective and efficient
removal and destruction of airborne contaminants, while minimizing the release of oxidation
byproducts. The present invention also provides a nonthermal plasma reactor design for use
in conjunction with a nonthermal plasma air treatment system. In a farther aspect, the
present invention provides a power supply for a nonthermal plasma reactor that includes an
inductive coupling for transferring power from a ballast circuit to a secondary circuit
containing the nonthermal plasma reactor.
In one embodiment of the present invention, a nonthermal plasma reactor is provided
that is comprised of a plurality of opposing electrodes, with one or more packed beds of
material with a relatively high dielectric constants between the electrodes. In another
embodiment of the present invention, a nonthermal reactor is provided that is comprised of a
plurality of opposing electrodes, with one or more packed beds of material between the
electrodes, wherein the packed bed is further comprised of an absorbent material and a
material with a relatively high dielectric constant. In another embodiment of the present
invention, a nonthermal reactor is provided that is comprised of a plurality of opposing
electrodes, with one or more packed beds of material between the electrodes, wherein the
packed bed is further comprised of an absorbent material, a material with a relatively high
dielectric constant, and a catalyst used to aid in the destruction or detoxification of ozone, or
accelerate the oxidation reactions.
In an alternative embodiment, the adsorbent material is separated from the nonthermal
plasma reactor. In this embodiment, a heating device is provided to provide thermal
desorption of the adsorbent and a fan is provided to circulate the air repeatedly through the
reactor. The separate heating device can provide quicker heat-up time and a higher operating
temperature than the nonthermal plasma reactor. Accordingly, the separate heater can
shorten the time required for the desorption/regeneration phase. Further, by separating the
nonthermal plasma reactor from the adsorbent material, the size of the plasma reactor can be
reduced. Instead of including a nonthermal plasma reactor that is of essentially the same size
as the adsorbent material, a significantly smaller reactor can be provided. A smaller reactor
requires a smaller power supply and has reduced power consumption during operation. The
cost of the reactor can also be reduced.
In another embodiment, the inductive coupling between the power supply and the
nonthermal plasma reactor includes a primary and a secondary that are separated by an air
gap, which provides a degree of isolation between the ballast and the secondary circuit. This
air gap can be selected to provide a current limiting function that limits the formation of
streamers in the bed.
In another embodiment of the present invention, the primary of the ballast circuit is
electrically connected within a resonant tank circuit and the ballast circuit includes a current
sensing circuit that monitors the current applied to the primary. The ballast circuit varies the
frequency of the signal applied to the resonant tank circuit as a function of the measured
current. In an embodiment, the current sensing circuit includes a transformer with at least
one primary electrically connected to the resonant tank circuit and a secondary located in the
ballast circuit. The current sensing circuit provides a dynamic power supply that can vary its
frequency to seek resonance over a range of reactor characteristics. Because the ballast
circuit can self-adjust to provide resonance despite changes in the characteristics of the
reactor, it permits the use of a smaller and more efficient power supply.
In another embodiment, the power supply also includes a load sensing circuit that
monitors the characteristics of the bed and adjusts the power supplied to the nonthermal
plasma reactor based on the monitored characteristic. In one embodiment, the load sensing
circuit measures the impedance of the bed and adjusts the power supplied to the nonthermal
plasma reactor based on the measured impedance. This permits the ballast circuit to adjust to
changes in the characteristics of the bed, perhaps most notably humidity which can have a
material affect on the generation and maintenance of plasma within the bed.
These and other objects, advantages, and features of the invention will be readily
understood and appreciated by reference to the detailed description of the preferred
embodiment and the drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 depicts one embodiment of a nonthermal plasma air treatment system of the
present invention;
Fig. 2 depicts one embodiment of the nonthermal plasma reactor used in the air
treatment system;
Fig. 3 depicts one embodiment of the nonthennal plasma reactor used in the air
treatment system;
Fig. 4 depicts one embodiment of the nonthennal plasma reactor used in the air
treatment system;
Fig. 5 depicts one embodiment of the nonthennal plasma reactor used in the air
treatment system;
Fig. 6 depicts one embodiment of the nonthennal plasma reactor used in the air
treatment system;
Fig. 7 depicts one embodiment of the nonthennal plasma reactor used in the air
treatment system;
Fig. 8 depicts one embodiment of the nonthermal plasma reactor used in the air
treatment system;
Fig. 9 depicts one embodiment of the nonthermal plasma reactor used in the air
treatment system;
Fig. 10 depicts one embodiment of the nonthermal plasma reactor used in the air
treatment system;
Fig. 11 depicts several embodiments of the electrodes used in the nonthermal plasma
reactor.
Fig. 12 is a block diagram of the major circuits and assemblies of the air treatment
system;
Fig. 13 is a block diagram of the inductively coupled ballast circuit;
Fig. 14 is an electrical circuit schematic of a portion of the inductively coupled ballast
circuit, the current sensing circuit and the interlock circuit;
Fig. 15 depicts a plurality of waveforms representing operation of the current sensing
circuit;
Fig. 16 is an electrical circuit schematic of the current limit circuit;
Fig. 17 is an electrical circuit schematic of a portion of an alternative current sensing
circuit;
Fig. 18 is a schematic diagram of an air treatment system in accordance with an
alternative embodiment of the present invention; and
Fig. 19 is a an exploded perspective view of the nonthermal plasma reactor of the
embodiment shown in Fig. 18.
Detailed Description of the Illustrated Embodiment
Fig. 1 illustrates one embodiment of the present invention. The air treatment system
10 is comprised of a housing 11, and a nonthermal plasma reactor 20 comprising a bed of an
adsorbent material 22 located between two opposing electrodes 24 and 26. Optionally, air
treatment system 10 is further comprised of a fan 12, a set of inlet vanes 16, a set of outlet
vanes 18, a prefilter 14, and a HEPA filter 29.
A typical operation cycle of air treatment system 10 is comprised of two phases of
operation; an adsorption phase and a desorption / regeneration phase. During the adsorption
phase, vane sets 16 and 18 are open and fan 12 is turned on, causing air to move first through
open vane set 16 and then through the prefilter 14 and into the nonthermal plasma reactor 20.
Those skilled in the art would recognize that fan 12 could easily be replaced by a blower or
other air-movement mechanism known in the art. Power is supplied to the fan 12 and vane
sets 16 and 18 using power and power switching systems well known in the art. Airborne
contaminants are captured by the adsorbent material in the packed bed 22. Finally, air moves
through HEPA filter 29, then through vane set 18 and out of system 10. A person skilled in
the art would recognize that the above identified components could be rearranged within the
air treatment system 10. For example, HEPA filter 29 could be placed between fan 12 and
reactor 20.
At completion of the adsorption phase, air treatment system 10 enters the desorption /
regeneration phase. During this phase of operation, vane sets 16 and 18 are closed, and fan
12 may be turned off, effectively isolating the interior of air treatment system 10 from the
surrounding environment. Electrodes 24 and 26 are then energized, creating a nonthermal
plasma. This nonthermal plasma oxidizes or detoxifies the contaminants entrained in the air
gaps within the packed bed of adsorbent material 22. As these contaminants are oxidized or
detoxified, contaminants are desorbed by the adsorbent bed. These contaminants are also
oxidized or detoxified by the nonthermal plasma. The nonthermal plasma elevates the
temperature of the adsorbent bed, which serves to further assist in the desorption of
contaminants. Because air treatment system 10 is isolated from the surrounding environment
during the desorption / regeneration phase, most oxidation by-products created during this
phase are trapped within the air treatment system 10 and detoxified by the nonthermal
plasma. Adsorbent bed may further include a catalyst to aid in the destruction or
detoxification of ozone. Fan 12 may be operated during the desorption / regeneration phase
to circulate air within air treatment system 10 and reactor 20.
A schematic illustration of an alternative air treatment system 10" is shown in Fig. 18.
The system 10" generally includes a housing 11", a nonthermal plasma reactor 20", an
adsorbent material 22", a heat source 23" and fan 12". The system 10" also includes structure
for selectively closing the interior of the system 10" off from the environment during the
desorption/regeneration phase, and an air recirculating system 21" for recirculating air
through the system during the desorption/regeneration phase. In the illustrated embodiment,
this structure includes vane sets 16" and 18", which can be pivoted to open and close the inlet
and outlets of the system 10". The vane sets 16" and 18" can be replaced by other similarly
functioning structure, such as a sliding or pivoting door. A further alternative may include a
pair of adjacent perforated plates in which at least one of the two plates is movable to
selectively align or misalign the perforation of the two plates. This system 10" may
optionally include a pre-filter 14", a HEPA filter 29" and/or other conventional air treatment
components.
In this system 10", the adsorbent material 22" is separated from the nonthermal
plasma reactor 20". The adsorbent material 22" may be located upstream (See Fig. 18) or
downstream (not shown) from the reactor 20". In the illustrated embodiment, the adsorbent
material 22" is a generally conventional activated-carbon fabric that adsorbs contaminants in
a generally conventional manner. The fabric may be pleated to provide increased surface
area. The carbon fabric can be replaced by other adsorbent materials, such as a packed bed
of activated carbon (not shown), or a pressed activated carbon filter (not shown). Because
the nonthermal plasma reactor 20" is separated from the adsorbent material, the system 10"
includes heat source 23" for selectively generating heat to cause thermal desorption of the
carbon fabric 22" during the desorption/regeneration phase. The heat source 23" may be an
array of conventional heat lamps, such as the infrared heat lamps 23" shown schematically in
Fig. 18. Alternatively, the heat source may be heat generating wires (not shown) extending
along or through the fabric 22", steam generator (not shown), an electric or gas heater (not
shown) or other conventional heat sources. As a further alternative, the heat source may
simply include an electric circuit for applying a current to the fabric 22".
The air recirculating system 21" generally includes a recirculating fan 35", an air
return 31" for causing air to circulate within the system 10" during the
desorption/regeneration phase and a vane set 19" for closing off the air return 31" during the
adsorption phase. In the illustrated embodiment, fan 35" is separate from fan 12".
Alternatively, a single fan may be provided to perform both functions, for example, to move
air through the system 10" during the adsorption phase and to circulate air through the system
10" during the desorption/regeneration phase. The air return 31" provides a flow path from a
point downstream of the nonthermal plasma reactor 20" to a point upstream of the adsorbent
material 22". In the illustrated embodiment, the air return 31" provides a flow path from a
location just upstream of vane set 18" to a point just downstream of vane set 16". The
configuration of air return 31" causes recirculating air to pass through all of the internal air
treatment components. This is not necessary, however, and the configuration of the air return
31" may be varied to exclude certain components, such as the pre-filter 14" and HEPA filter
29", from the recirculation flow path. Vane set 19" operates in a conventional manner as
described above in connection with vane sets 16" and 18". Vane set 19" can be replaced by
other structure for opening and closing the air return 31".
Like air treatment system 10, air treatment system 10" operates in a two phase cycle.
During the adsorption phase, vane sets 16" and 18" are opened and fan 12" is energized to
move air from the environment through the system 10". During this phase, vane set 19" is
closed to seal off the air return 31" and fan 35" is powered off. This prevents air from
recirculating through the system 10. The air passes through various levels of treatment at the
pre-filter 14", HEPA filter 29" and carbon fabric adsorbent 22". At the appropriate time, the
system 10" switches from the adsorption phase to the desorption/regeneration phase.
During the desorption/regeneration phase, the vane sets 16" and 18" are closed to seal
the interior of the system 10" off from the environment. Also, vane set 19" is opened and fan
35" is energized to move air through the air return 31", thereby establishing a recirculating air
flow within the system 10". Additionally, the heat source 23" and nonthermal plasma reactor
20" are activated. The heat source 23" generates heat that causes thermal desorption of
contaminants from the carbon fabric 22". The fan 35" moves air through pre-filter 14",
HEPA filter 29" and then the carbon fabric 22". As the air passes through the carbon fabric
22", it draws away the desorbed contaminants. The moving air then passes through the
plasma generated by the reactor 20" to break down the contaminants. Finally, fee fan 35"
moves the air back to the beginning of the air treatment system via air return 31" to
recirculate the air through the pre-filter 14"., HEPA filter 29", carbon fabric 22" and the
nonthermal plasma reactor 20". In this way, air moves desorbed contaminants from the
carbon fabric 22" to the plasma reactor 20" where they are destroyed. Because the air
continually circulates through the system 10", contaminants that are not destroyed in a single
pass will recirculate through the system 10", returning to the plasma reactor 20". Depending
on the timing of the desorption/regeneration phase, contaminants may pass through the
reactor 20" numerous times. The timing of the desorption/regeneration phase can be
controlled by predetermining the amount of time necessary to provide the desired level of
desorption/regeneration and then programming that timing into the controller. Alternatively,
the system 10" may include conventional sensors (not shown) that continually monitor the
level of contaminants in the air moving through the systems 10". The information provided
by the sensors (not shown) can be used to trigger the desorption/regeneration phase, for
example, when the contaminant level in the air output exceeds a predetermined threshold,
and to determine when that phase is complete, for example, when the contaminant level in
the circulating air falls below a predetermined threshold.
REACTOR
Adsorbents
As shown in Fig. 2 the reactor of the illustrated embodiment is comprised of opposing
electrodes 24 and 26, with a bed of adsorbent material in between. The adsorbent of the
illustrated embodiment is designed to provide a relatively large surface area to volume ratio,
and is comprised of a hydrophobic zeolite and a material of a particular dielectric value.
Zeolites are a class of natural occurring and synthetic compounds that are microporous
crystalline solids with a defined pore structure. The most common zeolites are composed of
silicon, aluminum and oxygen atoms, which form a three dimensional structure with voids, in
which organic compounds can adsorb. However, a number of other elements may be
incorporated within the structure. Different ratios of silicon to aluminum, and the inclusion
of other elements change the bonding in the zeolite, which determines the shape and
dimensions of the voids. As the amount of silicon increases in relationship to the amount of
aluminum, zeolites tend to become more hydrophobic. These zeolites adsorb less water
vapor as the humidity increases, and are better adsorbents for VOCs.
A dielectric material is a material that is a poor conductor of electric current, but an
efficient supporter of electrostatic fields. Metal oxides, in general, have high dielectric value.
An example of a material with a high dielectric value is barium titanate. The adsorbent bed
of the present invention contains an adsorbent, such as a zeolite, and a material with a high
dielectric value, such as barium titanate. In one embodiment of the present invention, barium
titanate powder is mixed with a binder, such as boehmite alumina, dispersed in water and
sprayed onto an extruded zeolite pellet. This would form, after drying, an adsorbent pellet
coated with a high dielectric material. In another embodiment of the present invention, the
adsorbent is comprised of a zeolite blended with a material of high dielectric value, and
extruded into small beads, spheres, extruded pellets, powders, and ground or crushed to
various particle sizes. Suitable binders to attach the high dielectric value material to the
zeolite include sodium silicate, alumina, colloid alumina and colloidal silica.
In another embodiment of the present invention, an adsorbent such as activated
carbon could be extruded into a suitable form, and then coated with a material with a high
dielectric value, such as barium titanate. The coating should be sufficient to coat the carbon
granules with an insulating material and prevent arcing through the bed. Activated carbon
has the advantage of higher adsorption capacity than zeolites, but the performance can be
quite dependent on humidity.
Figure 3 illustrates a multi-bed reactor with 2 beds of adsorbent material 38 and 39
sandwiched between three electrodes 32, 34 and 36. The electrodes are configured such that
the center electrode 34 opposes the two outside electrodes 32 and 36. In this configuration,
the air flowing through the reactor flows in a direction perpendicular to the electrodes. One
skilled in the art could readily recognize that the reactor could be constructed with multiple
adsorbent beds located between opposing electrodes.
Figure 4 illustrates a multi-bed reactor with three beds of adsorbent material 46, 47,
and 48, sandwiched between opposing electrodes 42, 43, 44, and 45. In this configuration,
the air flows through the reactor in a direction parallel to the electrodes 42, 43, 44, and 45.
One skilled in the art could readily recognize that the reactor could be constructed with
multiple adsorbent beds located between opposing electrodes.
Figure 5 illustrates a cylindrical reactor, with a first electrode 52 placed at the core of
the cylinder, a second electrode 54 defining the outer surface of the cylinder, and the volume
between the core and the outer surface being at least partially filled with an adsorbent
material 56 as described above.
An alternative reactor design is provided by coating an air permeable substrate with
an adsorbent as described above. A suitable structure would allow air to pass through, yet the
path of the air through the media make it likely that the air would contact the adsorbent.
Possible configurations for the air permeable substrate include:
• honeycomb monoliths, made of ceramics, inorganic fibers, metals or plastics;
• fibrous substrates;
• reticulated foams;
• metal mesh or expanded metal;
• a monolith made from corrugated materials.
It would be obvious to one skilled in the art that other structures could be used.
In alternative air treatment system 10", the adsorbent material 22" is separated from
the reactor 20". Accordingly, the reactor 20" need not include an adsorbent material. In the
illustrated embodiment, the reactor 20" is disposed downstream from the adsorbent material
22s along the flow path followed by air during the adsorption phase. The reactor 20" may
alternatively be disposed in essentially any location along the flow path followed by air
during the desorption/regeneration phase. Referring now to Fig. 19, the reactor 20" of system
10" generally includes a pair of opposing electrodes 24" and 26" disposed on opposite sides of
spacer 25". In the illustrated embodiment, the electrodes 24" and 26" are manufactured from
conventional stainless steel mesh. The spacing of the mesh is selected primarily to prevent
any dielectric materials or catalysts from spilling from the reactor 20". The reactor 20" may
alternatively include electrodes of essentially any conventional constructions. The spacer 25"
of this embodiment is a ceramic peripheral frame, for example, a rectangular frame as shown
in Fig. 19. The spacer 25" may include a replaceable plug 27" that permits access to the
interior 37" of the reactor 20". In this embodiment, the plug 27" is removable to permit a
dielectric material 33" and/or a catalyst to be disposed within the interior 37" of the reactor
20". The dielectric material improves the operation of the plasma and may include any of a
wide variety of conventional dielectric materials. In this embodiment, the dielectric material
33" includes a plurality of alumina beads, which provide a reasonable balance between cost
and dielectric constant for many applications. The beads are typically of a larger diameter
than the openings in the electrodes 24" and 26" to entrap the beads in the reactor 20". The
dielectric beads 33" are poured into the reactor 20" by removing plug 27". After the dielectric
beads 33" are installed, the plug 27" is returned to enclose the dielectric beads 33". The plug
27" may be secured to the spacer 25" with adhesives or mechanical fastening structures. For
example, the plug 27" may be frictionally fitted within the spacer 25", may include a snap
(not shown) to permit the plug 27" to be snap-fitted in place or may be secured by screws or
other fasteners (not shown). Alternatively, the plug 27" may be removed and the dielectric
material can be added during assembly of the reactor 20", for example, before attaching the
final electrode 24" or 26" to the spacer 25". As described in more detail below, the reactor
20" may also include one or more catalysts that facilitate decomposition of contaminants. A
separate catalyst may be added to the interior 37" along with the dielectric material or a
dielectric material may be selected that has the desired catalytic properties. Although the
reactor 20" is illustrated as a rectangular box, the size, shape and configuration of the reactor
20", including the electrodes 24", 26" and the spacer 25" may vary from application to
application as desired. For example, the size and shape of the reactor 20", including the
electrodes 24", 26" and the spacer 25", may be varied to accommodate the size constraints of
the corresponding air treatment system housing.
Catalysts
Catalysts can increase rate of decomposition of organic contaminants in a nonthermal
plasma. Since ozone is formed in the nonthermal plasma, catalysts that help decompose
ozone have application in the reactor. Therefore, the adsorbents used in this type of product
could include the addition of a catalyst. Potential catalysts are the noble metals such as
platinum and palladium, tin oxide, tungsten oxide, manganese oxides, copper oxides, iron
oxides, cerium oxides, vanadium oxides, or mixtures thereof. It would be obvious to one
skilled in the art that other catalysts could be used.
An alternative to adding the catalyst to the adsorbent is to include the catalyst in the
reactor on a separate media, such as a reticulated foam, or other substrate with a high surface
area.
Activated carbon is also very effective for the decomposition of ozone, although the
carbon is a reactant, rather than a catalyst. Activated carbon could be used in the form of
activated carbon cloth, in the form of small particles supported on a media with a large
surface area, or in the form of a packed bed of larger particles.
In air treatment system 10", a catalyst can be added to provide improved
decomposition of contaminants. The catalyst may be disposed on adsorbent material 22", in
the nonthermal plasma reactor 20" or in other locations along the air recirculation flow path.
In the embodiment illustrated in Figs. 18 and 19, the catalyst (not shown) is added to the
nonthermal plasma reactor 20". More specifically, the catalyst is coated on the surface of the
dielectric beads 33". The catalyst-coated dielectric beads 33" are disposed within the interior
37" of the reactor 20". The beads may be coated with barium titanate, titanium dioxide,
manganese dioxide or other catalysts, such as other metal oxides, to provide improved
decomposition rates for ozone and other contaminants.
Electrode Design
The electrodes of the present invention are designed to create a multitude of
streamers, or groups of high energy electrons leaving the electrode surface. In one
embodiment of the present invention, the reactor is designed as a dielectric barrier discharge
reactor, in which at least one the electrodes is coated with a dielectric material, or there is a
dielectric material between the electrodes. A high voltage AC or pulsed electrical power is
applied to the electrodes. A charge builds up on the surface of the dielectric material and the
charge is discharged into the air The charge on the surface requires a time to recharge in the
location of the discharge. This type of dielectric barrier system has the advantage in that it is
not likely to have an arc strike between the two electrodes. The disadvantage of a dielectric
barrier discharge is that it requires more power to treat a given amount of air.
In another embodiment of the present invention, the reactor uses bare electrodes and
does not contain a dielectric barrier. This type of design is more efficient, but requires
controls to assure that an arc is not established. It would be obvious to one skilled in the art
that other reactor designs could be used.
Figure 6, illustrates one embodiment of a reactor 60 that utilizes two electrodes, 62
and 64, made from either metal mesh, expanded metal or perforated metal. This design
allows air to pass through the electrodes. In the space between the electrodes is a
nonconductive porous substrate that contains the adsorbent 66. In normal operation, the air
passes through the reactor and the contaminants are adsorbed. This design could be
considered a dielectric barrier discharge or a corona discharge, depending on the design of
the porous media between the electrodes, and whether the electrodes are coated with a
dielectric material.
Fig. 7 illustrates an embodiment of a reactor 70 similar to the reactor shown in Fig. 6,
except the nonconductive porous media 76 which contains an adsorbent material and has
been placed in the air flow following the two electrodes 72 and 74. In this design the air
flows past the electrodes 72 and 74 and the high energy electrons are created and the air
molecules that are ionized pass through the porous media 76. The free radicals in the air
desorb and oxidize the contaminants that are trapped on the adsorbent held within the porous
media 76. This design can be a dielectric barrier discharge or a corona discharge, depending
on the design of the electrodes. During the desorption/regeneration mode this design requires
some air movement to move the free radicals into the porous media 76.
Fig. 8 illustrates another reactor embodiment 80 that utilizes the porous media 84 as
one of the electrodes. The electrical discharge takes place between the conductive mesh
electrode 82, and the closest surface of the conductive porous media 84. This reactor
functions similar to the reactor illustrated in Figure 7, in that the ions and free radicals are
created and them pass through the porous media. This reactor can be designed as a dielectric
barrier discharge or a corona discharge depending on the design of the conductive mesh
electrode.
Fig. 9 illustrates a reactor design 90 that utilizes parallel plates 95 that have been
coated with an adsorbent 96 and have alternate polarity. The composition of the adsorbent
coating 96 can determine if this reactor design is a corona discharge or a dielectric barrier
discharge.
Fig. 10 illustrates a reactor design 100 that is similar to the reactor shown in Fig. 9,
except the plates 102 all have the same polarity. The electrode with the alternate polarity 104
is comprised of a wire or rod between the plates. The electrode could also be a plate or mesh,
between the plates coated with the adsorbent 106. If the adsorbent coating 106 can act as a
dielectric barrier, then the reactor will be of that design. The type of reactor could also be
operated as a corona discharge, depending on the adsorbent coating.
Further electrode designs are illustrated in Fig. 11. Sheet metal would be die cut on
the solid lines as shown in the figures, or a similar pattern, forming numerous triangles cut
through the metal. The sides of the triangles could be die cut with a sawtooth type edge, to
increase the number of points. The triangle form would then be folded on the dashed line, 90
degrees, forming a porous electrode that could have a multitude of points that would aid in
passing the high energy electrons into the air. These drawings are only intended to show a
small section of an electrode, because the ideal electrode would have many of points on it.
As noted above, Fig. 19 depicts the reactor 20" of air treatment system 10". In the
illustrated embodiment, the reactor 20" generally includes a pair of mesh electrodes 24" and
26". The electrodes may be manufactured of stainless steel to resist corrosion and provide
relatively long life. A dielectric material and/or decomposition catalyst may be added
between the electrodes 24" and 26", but is not strictly necessary to operation of the reactor
20".
Power Supply
To provide efficient and proper operation in the face of the changing characteristics of
the bed, the present invention may, as in the described embodiment, include a dynamic power
supply that adjusts to changes in the operating parameters of the nonthermal plasma reactor.
The power supply preferably includes a primary circuit and a secondary circuit that are
coupled to one another by an inductive coupling. In a first aspect, the power supply has the
ability to adjust power output to match the load and maintain resonance, which is described
in more detail below. This permits a smaller and more efficient power supply. With
conventional power supplies, the power supply would be tuned to match the load at certain
pre-selected characteristics. As a result, efficiency (and possibly proper operation) is
compromised when the load does not match the pre-selected characteristics to which the
power supply is tuned. Although a pre-tuned power supply can be used, a dynamic power
supply, such as the power supply described below, provides marked benefits. This design
can be used to span a pre-defined range of frequencies and automatically maintain the system
at resonant frequency. As an additional benefit, the inductive coupling preferably includes an
air gap that can be designed to limit current across the gap, thereby limiting the formation of
thermal streamers within the nonthermal plasma reactor. If a thermal streamer forms the
current starts to spike and is immediately limited. The transient discharges that are known as
streamers can be arrested when the electric field is reduced to the point where electron
attachment becomes dominant. This identifies the transformation of a streamer or transient
discharge to a thermal streamer. The current used to maintain a thermal streamer is much
larger and can have an adverse affect on the bed by causing carbonization. The limiting of
thermal streamers through the reactor under various operating conditions while maintaining
effective and efficient control of the streamer potential becomes very essential to a low cost
system. Having a system that limits the voltage potential as the reactor changes and adjusts
to resonance for variable operating conditions makes it easier to control the dynamics and
contributes to a small low cost system. The power limiting capability is also affected by the
efficiency of the resonant center and how far off center the supply is as compared to the load.
The load can be pre-matched to the optimum frequency and operating point by designing for
the proper impedance and selecting a matching capacitor on the load side either in series or
parallel depending on the drive method. The power supply can be used to generate the AC
that charges the high voltage capacitor. It can be used to charge an AC capacitor and control
the AC signal imposed on the high voltage DC. This power supply can be used as an AC
power source. The frequency of drive is dependent on the design of the bed and the ability to
correct for resonance over the expected operation range.
In an embodiment, the power supply also includes a control system for adjusting the
power supplied to the nonthermal plasma reactor based operational characteristics, such as
the impedance of the adsorbent bed or the impedance of the reactor. For example, the reactor
impedance can be determined by submitting the bed to a high voltage pulse while monitoring
power consumption. A bed with higher humidity will consume more power and will run at
different frequencies then a bed with lower humidity. The reactor impedance could be
measured with a low voltage potential but the high voltage pulse allows a more complete
analysis of the load. This added power translates to heat and is subsequently used to drive off
moisture. The moisture and air together create a gas. The presence of O2 and H2O in the air
makes the air or gas around the reactor bed electronegative. The heat driving off the
moisture absorbed by the bed specifically enhances this effect. The control sequence of the
present embodiment would be designed to test the bed and start at a power level that will
drive off moisture in a safe range as to not damage the bed. The power can be easily
monitored using the current feedback transformer on the power supply. It must also be
mentioned that the span of the self seeking resonant supply discussed prior can be designed
to cover the range of the reactor impedance. Power could also be chosen to limit the drying
process of the bed. Voltage may easiest parameter to control in this embodiment. The
voltage applied is varied along a curve that is inverse to the humidity within the reactor. That
is to say that the lower the humidity needs a higher voltage to create a non thermal plasma
and higher humidity situations may not establish a non-thermal plasma but creates enough
heat to drive off moisture until the bed is regenerated. The design can allow for resonance
while monitoring bed impedance and driving off moisture to reach optimum non-thermal
plasma.
The power supply controls described above are applicable to several types of non-
thermal plasmas and drive techniques. The following paragraphs address some of the drive
and switch methods that can be used with these controls.
A. Pulsed AC
The AC power supply as described becomes quite effective in the pulse control. The
frequency and pulse control or rise times can be controlled by bed impedance. To achieve a
faster rise time the design of the bed will be adjusted to allow a higher resonant frequency.
This is accomplished by changing the bed capacitance and resistance. The adjustments to
resonance are performed using multiple beds, using series beds, parallel beds, or any
combination to allow the frequency to be selected within the physics of the selected
materials. The bed thickness may require a different number of beds, for example, two or
twenty beds in series. Making a bed thinner or thicker can help control the capacitance and
resistance. Controlling the square inches of electrode area also control the resistance and
capacitance. The combination of these characteristics will in large part determine the
resonant frequency of the bed at specific drive and bed conditions.
B. Pulsed DC
In this design, the AC self-resonant power supply is rectified and charges a high
voltage capacitor. The same control methodology is used but the switching is also controlled
to the resonance of the bed. This is not required for function, but may improve the efficiency
of the system. The same type of self-resonant power supply is used to create the DC and then
switch the DC at a resonant frequency.
C. DC with Pulsed AC
The DC with an AC ripple is very conducive to synergistic results. The DC is
suspected to provide a DC corona while the AC also allows the AC corona discharge. With
the DC voltage level at a point of creating a DC discharge and an AC discharge that creates
the streamers added to this DC voltage both discharges are created. This means that the AC
can have less rise time to get the same result because the potential is already at the DC level
and only has to be increased to the point of creating the streamer.
An embodiment of the power supply will now be described in detail with reference to
Figs. 12 through 17. Referring to Fig."s 1 and 12, the inductively coupled ballast circuit 140
is a self-oscillating, half-bridge switching design that operates at high frequencies. The
inductively coupled ballast circuit 140 self-oscillates once resonance is achieved, uses
MOSFET transistors as switching elements, and is designed to accommodate an air-core
transformer coupling arrangement, which simplifies the design of the nonthermal plasma
reactor assembly 20. The nonthermal plasma reactor assembly 20 may be readily replaced
because of the air-core transformer coupling arrangement created by the inductively coupled
ballast circuit 140.
As illustrated in Fig. 13, the inductively coupled ballast circuit 140 of the described
embodiment generally includes a control unit 102, a control circuit 142, an oscillator 144, a
driver 146, a half-bridge switching circuit 148, a series resonant tank circuit 150. The
nonthermal plasma reactor assembly 14 generally includes the secondary coil 52, the
secondary circuit 152 and the nonthermal plasma reactor 20 (See Fig. 1). The oscillator 144
is electrically connected with the control circuit 142, which energizes the oscillator 144 by
providing electric signals to the control circuit 142. During operation, the oscillator 144
provides electrical signals to direct the driver 146, which then causes the half-bridge
switching circuit 148 to become energized. The half-bridge switching circuit 148 energizes
the series resonant tank circuit 150 that, in turn, inductively energizes the nonthermal plasma
reactor 20.
As noted above and as further illustrated in Fig. 13, the nonthermal plasma reactor
assembly 14 includes the secondary coil 52, the resonant secondary circuit 152 and the
nonthermal plasma reactor 20 while the electronic assembly 44 houses the control circuit
142, the oscillator 144, the driver 146, the half-bridge switching circuit 148 and the series
resonant tank circuit 150. As previously set forth, once the series resonant tank circuit 150 is
energized, the secondary coil 52 in the nonthermal plasma reactor assembly 14 becomes
inductively energized, which is illustrated by the line between the resonant tank circuit 150
and the secondary coil 52 in Fig. 13. The range of frequencies over which the ballast circuit
operates may be varied based on an anticipated range of characteristics of the bed. As known
to those skilled in the art, the resonant frequency may be any desired frequency selected as a
function of the component selection in the series resonant tank circuit 150 and the nonthermal
plasma reactor assembly 14.
Referring to Fig. 14, the control circuit 142 is electrically connected with the control
unit 102 and the oscillator 144. The control circuit 142 includes a plurality of resistors 156,
158, 160, 162, 164, 166, a plurality of capacitors 168, 170 172, a diode 174, a first
operational amplifier 176 and a second operational amplifier 178. As illustrated, resistor 156
is connected with a first direct current ("DC") power source 180, the output of the control
unit 102 and resistor 158. Resistor 158 is further connected with diode 174, resistor 160 and
capacitor 168. The first DC power source 180 is connected with capacitor 168, which is also
connected with diode 174. Diode 174 is further connected with a ground connection 182, as
those skilled in the art would recognize. Resistor 160 is connected with the negative input of
operational amplifier 176 and the positive input of operational amplifier 178 to complete the
current path from the control unit 102 to the operational amplifiers 176, 178.
Referring once again to the control circuit 142 depicted in Fig. 14, resistor 162 is
connected with a second DC power source 184 and in series with resistors 164 and 166.
Resistor 166 is connected with the ground connection 182 and capacitor 170, which is, in
turn, connected with the first DC power source 180 and resistor 164. The positive input of
operational amplifier 176 is electrically connected between resistors 162 and 164, which
provides a DC reference voltage to operational amplifier 176 during operation. The negative
input of operational amplifier 178 is electrically connected between resistors 164 and 166,
which provides a DC reference voltage to operational amplifier 178 during operation. The
output of operational amplifiers 176 and 178 is connected with the oscillator 144, as set forth
in detail below.
During operation, the control circuit 142 receives electrical signals from the control
unit 102 and, in turn, acts as a window comparator that only switches when the input voltage
produced by the control unit 102 is within a certain voltage window. The preferred signal
from the control unit 102 is an AC signal that, together with its duty cycle, allows the control
unit 102 to turn the nonthermal plasma reactor 20 on and off through the remaining
components of the inductively coupled ballast circuit 140, as will be set forth below. The
control circuit 142 also prevents false triggering and allows positive control if the control unit
102 fails.
As illustrated in Fig. 14, the first DC power source 180 and the second DC power
source 184 provide power to the circuits depicted in Fig. 14. Those skilled in the art of
electronics would recognize that DC power supply circuits are well known in the art and
beyond the scope of the present invention. For the purposes of the present invention, it is
important to note that such circuits exist and are capable of being designed to produce
various DC voltage values from a given AC or DC power source. Those skilled in the art
would recognize that the circuits disclosed in Fig. 5 could be designed to operate on various
DC voltage levels, as desired, and that the present invention should not be limited to any
particular DC voltage level.
In the embodiment depicted in Fig. 14, the output of the control circuit 142 is
connected with an interlock circuit 190 to prevent the nonthermal plasma reactor 60 from
becoming energized if the air treatment system 10 is not properly assembled. The interlock
circuit 190 includes a magnetic interlock sensor 192, a plurality of resistors 193, 194, 196,
198, 200, 202, 204, a transistor 206 and a diode 208. The magnetic interlock sensor 192 is
positioned so that if a shroud or covering for air treatment system 10 is not securely
positioned, the air treatment system 10 will not energize the nonthermal plasma reactor 20.
Those skilled in the art would recognize that the magnetic interlock sensor 192 might be
placed in any convenient place of the air treatment system 10.
Referring to Fig. 14, the magnetic interlock circuit 190 operates by directing the
output of the control circuit 142 to the ground connection 182, through transistor 206, if the
magnetic interlock sensor 192 detects that the air treatment system 10 is not assembled
properly, as set forth above. As those skilled in the art would recognize, if the air treatment
system 10 is not assembled properly, the output of the magnetic interlock sensor 192 causes
the current flowing through resistors 194, 196 and 198 to energize the gate of transistor 206,
which thereby shorts the output signal of the control circuit 142 to the ground connection
182. The magnetic interlock sensor 192 is powered by the second DC power source 184
through resistor 193 and is also connected with the ground connection 182. In addition, the
magnetic interlock sensor 192 sends a signal to the control unit 102, through the combination
of resistors 200, 202 and 204, diode 208, first DC power source 180 and second DC power
source 184. This signal also allows the control unit 102 to determine when the air treatment
assembly 10 is not assembled properly. To that end, the interlock circuit 190 provides two
methods of ensuring that the nonthermal plasma reactor 20 is not energized if the air
treatment system 10 is not assembled properly. The magnetic interlock is not necessary for
the operation of the present invention.
Referring once again to Fig. 14, the oscillator 144 provides electrical signals that
energize the driver 146 while the air treatment system 10 operating. The oscillator 144
begins operating immediately once an electrical signal is sent from the control unit 102,
through control circuit 142, as set forth above. As readily apparent, the oscillator 144 may
also be controlled by any other mechanism capable of activating and deactivating the
oscillator 144. The illustrated oscillator 144 comprises an operational amplifier 210, a linear
bias resistor 212, a buffer circuit 214, a buffer feedback protect circuit 216 and a positive
feedback circuit 218. During operation, the operational amplifier 210 receives input signals
from the control circuit 142, the linear bias resistor 212 and the positive feedback circuit 218.
The operatbnal amplifier 210 is also connected with the second DC power source 184 and
the ground connection 182, which energizes the operational amplifier 210.
As illustrated in Pig. 14, the illustrated buffer circuit 214 comprises a first transistor
220, a second transistor 222 and a pair of resistors 224, 226. The output of operational
amplifier 210 is connected with the gates of transistors 220, 222, thereby controlling
operation of transistors 220, 222. The second DC power source 184 is connected with
resistor 224, which is also connected with collector of transistor 220. The emitter of
transistor 220 is connected with resistor 226, the emitter of transistor 222 and the input of the
driver 146. The collector of transistor 222 is connected with ground connection 182. During
operation, the buffer circuit 214 buffers the output signal from the operational amplifier 210
and prevents load changes from pulling the frequency of oscillation. In addition, the buffer
circuit 214 increases the effective gain of the inductively coupled ballast circuit 140, which
helps ensure a quick start of the oscillator 144.
The buffer feedback protect circuit 216 comprises a pair of diodes 228, 230 that are
electrically connected with the output of the buffer circuit 214 by resistor 226. As illustrated
in Fig. 5, the second DC power source 184 is connected with the cathode of diode 228. The
anode of diode 228 and the cathode of diode 220 are connected with resistor 226 and the
linear bias resistor 212. The linear bias resistor 212 provides bias feedback signals to the
negative input of operational amplifier 210. In addition, the anode of diode 230 is connected
with ground connection 182, which completes the buffer feedback protect circuit 216. The
buffer feedback circuit 216 protects the buffer circuit 214 from drain to gate Miller-effect
feedback during operation of the reactor 20.
As illustrated in Fig. 14, the current sensing circuit or positive feedback circuit 218
includes a first multi-winding transformer 232, a plurality of resistors 234, 236,238, a pair of
diodes 240, 242, and a capacitor 244. The transformer 232 preferably includes two primary
coils that are connected in parallel between the output of the half-bridge switching circuit 148
and the input of the series resonant tank circuit 150 as illustrated in Fig. 5. The transformer
232 preferably includes two primary coils connected in series rather than a single primary
coil to reduce the total reactance on the primary side of the transformer, thereby reducing the
reactive impact of the transformer 232 on the tank circuit 150. In other applications, the
primary side of the transformer may be divided into a different number of primary coils. For
example, the transformer 232 may include only a single primary coil where reduction of the
reactive impact of the transformer is not important or may include three or more primary
coils where even further reduction of the reactive impact of the transformer 232 is desired.
The first lead of the secondary coil of transformer 232 is electrically connected with
resistors 234,236, 238, the diodes 240, 242 and the positive input of the operational amplifier
210. The second lead of the secondary coil of the transformer 232 is connected with resistor
238, the cathode of diode 242, the anode of diode 240 and capacitor 244. As such, resistor
238 and diodes 242, 244 are connected in parallel with the secondary winding of transformer
232, as illustrated in Fig. 5. Capacitor 244 is also electrically connected with the negative
input of operational amplifier 210. In addition, resistor 234 is connected with the second DC
power source 184 and resistor 236 is connected with the ground connection 182. Resistors
234, 236 and 238 protect the operational amplifier 210 from current overload and diodes 240,
242 clip the feedback signal that is sent to the input of the operational amplifier 210.
During operation, the oscillator 144 receives signals from the control circuit 142 that
charges capacitor 244, which, in turn, sends an electrical signal to the negative input of the
operational amplifier 210. The output of the operational amplifier 210 is electrically directed
to the driver 146, which energizes the half-bridge switching circuit 148. As illustrated in Fig.
14, the transformer 232 is connected in this current path and sends electrical signals back
through resistors 234, 236 and 238, which limits the current, and eventually directs the
electrical signal back to the inputs of the operational amplifier 210 to provide a current
sensing feedback. The current sensing feedback provided by transformer 232 allows the
oscillator 144 to self-resonate and the inductively coupled ballast circuit 103 remains
oscillating until the control unit 102 shuts the air treatment system 10 down or transistor 206
of the interlock circuit 190 pulls the input to the oscillator 144 low.
More specifically, the positive feedback circuit 218 (or current sensing circuit)
provides feedback to the operational amplifier 210 that controls the timing of the oscillator
144 so that the oscillator 144 does not impair the tank circuit"s 150 inherent tendency to
oscillate at resonant frequency. In general, the current in the series resonant tank circuit 150
flows through the primary coils of transformer 232, thereby inducing a voltage in the
secondary coil of transformer 232. The AC signal generated by the transformer 232 is
superimposed upon a DC reference signal set by resistors 234 and 236. The operational
amplifier 210 is preferably a conventional difference operational amplifier providing an
output based, in part, on the difference between the amplitude of the signal on the positive
lead and the amplitude of the signal of the negative. Given that opposite leads of the
operational amplifier 210 are connected to opposite sides of the secondary coil of the
transformer 232, the signal applied to the positive lead of the operational amplifier 210 is
essentially equal in magnitude, but opposite in polarity from the signal applied to the
negative lead of the operational amplifier 210. Accordingly, the output of the operational
amplifier 210 oscillates above and below the reference signal in accordance with the
oscillating signal of the current feedback circuit. The operational amplifier 210 is preferably
alternately driven between saturation and cutoff, thereby providing a quasi-square wave
output. When the output of the operational amplifier 210 exceeds the reference signal,
transistor 220 is driven to "on," while transistor 222 is driven to "off," thereby charging
capacitor 248 and discharging capacitor 250. When the output of the operational amplifier
210 falls below the reference signal, transistor 222 is driven to "on" while transistor 220 is
driven to "off," thereby discharging capacitor 248 and charging capacitor 250. This
alternating charging/discharging of capacitors 248 and 250 results in an alternating signal
being applied to the primary coil of the driver 146, as described in more detail below. The
frequency shifting (or resonance seeking) operation of the circuit is described in more detail
with reference to Fig. 15. In this illustration, the current in the primary coil is represented by
waveform 600, the voltage in the current transformer 232 is represented by waveform 602
and the current feedback signal is represented by waveform 604 (shown without clipping of
diodes 240 and 242). As noted above, the operational amplifier 210 is alternately driven
between saturation and cutoff with a transition period interposed between the saturation and
cutoff portions of the waveform. The length of the transition period is dictated by the slope
of the current feedback signal. The timing of the operational amplifier 210 is dependent on
the length of the transition period. By varying the length of the transition period, the timing
of the transitions in the operational amplifier 210 output signal is controlled. This shift in
timing is perpetuated through the driver 146, which truncates the signal in the tank circuit
150. The truncated signal in the tank circuit 150 is reflected into the current feedback signal
by the current transformer 232 to perpetuate the frequency shift. When an increased load is
applied to the secondary circuit, a corresponding increase occurs in the amplitude of the
current in the tank circuit 150. This increased signal is represented by waveform 606 in Fig.
15. The increased signal in the tank circuit 150 results in a corresponding increase in the
voltage in the current transformer 232. The increased voltage in the current transformer 232
is represented by waveform 608. The increased voltage in the current transformer 232 finally
results in an increase in the amplitude of the current feedback signal, represented by
waveform 610 (shown without clipping of diodes 240 and 242). The increased current
feedback signal has a greater slope at the zero crossings and therefore causes the operational
amplifier 210 to transition from one state to the other sooner in time. This in turn causes the
transistors 220 and 222 to switch sooner in time and the AC signal applied to the driver 146
to alternate sooner in time. Ultimately, there is a corresponding shift in the timing of the
signals applied to the tank circuit 150 by the half-bridge switching circuit 148. The shift in
timing of the signals applied by the switching circuit 148 has the effect of truncating the
inherent osculating signal in the tank circuit 150, thereby shifting the timing of the signal in
the tank circuit 150. The truncated signal in the tank circuit 150 is reflected into the current
sensing circuit 218. This varies the current feedback signal applied to the operational
amplifier 210, thereby perpetuating the time shift and effecting an upward increase in the
frequency of the oscillator. In this way the oscillator 144 and driver 146 permit the tank
circuit 150 to shift its frequency to remain at resonance despite a change in load. When a
decrease in the load applied to the secondary circuit occurs, the frequency of the oscillator
144 decreases in a manner essentially opposite that described above in connection with an
increase in frequency. In summary, the decreased load results in decreased current in the
tank circuit 150. This results, in turn, in a decrease in the voltage induced in the current
transformer 232 and a decrease in the amplitude of the current feedback signal. The
decreased current feedback signal has a decreased slope, and accordingly causes the
operational amplifier 210 to complete the transition between saturation and cutoff later in
time. The transistors 220 and 222 also transition later in time, thereby shifting the timing of
the driver 146 and the timing of the switching circuit 148. The net effect of the shift in the
timing of the switching circuit 148 is to extend the signal in the tank circuit 150. The
extended signal is reflected into the current sensing circuit 218 where it is returned to the
operational amplifier 210 to perpetuate the decrease in frequency of the oscillator 144.
Optimal performance is achieved when the half-bridge switching circuit 148 alternates at the
zero crossings of the current signal in the tank circuit 150. This provides optimal timing of
the energy supplied by the switching circuit 148 to the tank circuit 150. In some applications,
it may be necessary or desirable to shift the phase of the current feedback signal to provide
the desired timing. For example, in some applications, the parasitic effect of the various
circuit components may result in a shift in the phase of the current feedback signal. In such
applications, the current sensing circuit can be provided with components, such as an RC
circuit, to shift the signal back into alignment so that the switching circuit 148 alternates at
the zero crossings. Fig. 17 illustrates a portion of an alternative current sensing circuit 218",
which includes an RC circuit configured to shift the phase of the current feedback signal 120
degrees. In this embodiment, the current sensing circuit 218" is essentially identical to the
current sensing circuit 218 of the above described embodiment, except that it includes two
capacitors 800, 802 and two resistors 804, 806 that are connected along the leads extending
back to the operation amplifier 210. Fig. 17 forther illustrates that the secondary of the
current transformer 232 can be connected to ground 182 to provide a zero reference, if
desired.
Referring once again to Fig. 14, the output of the oscillator 144 is electrically
connected with the driver 146, which comprises the first primary winding of a second multi-
winding transformer 246 in the illustrated embodiment. In this embodiment, the second
transformer 246 is the preferred driver 146 because the phasing arrangement of the
transformer 246 insures that the half-bridge switching circuit 148 will be alternately driven,
which avoids shoot-through conduction. A double arrangement of capacitors 248, 250 is
electrically connected with the second primary winding of transformer 246, thereby
preventing DC current overflow in the transformer 246. Capacitor 246 is also connected with
the ground connection 182 and capacitor 250 is also connected with the second DC power
source 184.
Both secondary coils of transformer 246 are electrically connected with the half-
bridge switching circuit 148, which receives energy from transformer 246 during operation.
The half-bridge switching circuit 148, which is also illustrated in Fig. 5, is electrically
arranged as a MOSFET totem pole half-bridge switching circuit 252 that is driven by both
secondary coils of transformer 246. The MOSFET totem pole half-bridge switching circuit
252 includes a first MOSFET transistor 254 and a second MOSFET transistor 256 that
provide advantages over conventional bipolar transistor switching circuits. Energy is
transferred from the driver 146 to the MOSFET transistors 254, 256 through a plurality of
resistors 258, 260, 262, 264. The MOSFET transistors 254, 256 are designed to soft-switch
at zero current and exhibit only conduction losses during operation. The output generated by
MOSFET transistors 254, 256 is more in the form of a sine wave that has fewer harmonics
than that generated by traditional bipolar transistors. Using MOSFET transistors 254, 256
also provides advantages by reducing radio frequency interference that is generated by the
MOSFET transistors 254, 256 while switching during operation.
In the half-bridge switching circuit 148 depicted in Fig. 14, the first secondary coil of
transformer 246 is connected with resistor 258 and resistor 260. The second secondary coil
of transformer 246 is connected with resistor 262 and resistor 264. Resistor 260 is connected
with the gate of MOSFET transistor 254 and resistor 264 is connected with the gate of
MOSFET transistor 256. As illustrated, the first secondary coil of transformer 246 and
resistor 258 are connected with the emitter of MOSFET transistor 254. The second
secondary coil of transformer 246 and resistor 264 are connected with the gate of MOSFET
transistor 256. The collector of MOSFET transistor 254 is connected with the second DC
power source 184 and the emitter of MOSFET transistor 254 is connected with the collector
of MOSFET transistor 256. The emitter of MOSFET transistor 256 and resistor 262 are
connected with the ground connection 182.
A further benefit of the driver 146 is that multi-winding transformer 246 is a very
convenient way to apply gate drive voltage to the MOSFET transistors 254, 256 that exceeds
the second DC power source 184. The MOSFET transistors 254, 256 provide further
advantages because they have diodes inherent in their design that protect the MOSFET totem
pole half-bridge switching circuit 252 from load transients. In addition, over-voltages
reflected from the series resonant tank circuit 150, by changes in load, are returned to supply
rails by the inherent diodes within MOSFET transistors 254, 256.
Referring to Fig. 14, the output of the half-bridge switching circuit 148 is connected
with the input of the series resonant tank circuit 150, which, in turn, inductively energizes the
secondary coil 52 of the nonthermal plasma reactor assembly 20 (Fig. 1). As set forth above,
in the illustrated embodiment of the invention, the positive feedback circuit 218 of the
oscillator 144 is connected with the output of the half-bridge switching circuit 148 and the
input of the series resonant tank circuit 150 to provide current sense feedback to operational
amplifier 210 of the oscillator 144 during operation. The output of the half-bridge switching
circuit 148 is connected with the input of the series resonant tank circuit 150 by the
secondary coil of transformer 232 as illustrated in Fig. 14.
Referring to Fig. 14, the series resonant tank circuit 150 comprises an inductive
coupler 270, the parallel combination of a pair of tank capacitors 271, 272, a pair of diodes
274, 276 and a capacitor 278. The inductive coupler 270 is connected with the secondary
coil of transformer 232 and between tank capacitors 271, 272. Tank capacitor 271 is also
connected with the second DC power source 184 and tank capacitor 272 is also connected
with the ground connection 182. In addition, tank capacitor 271 and the second DC power
source 184 are connected with the anode of diode 274. The cathode of diode 274 and
capacitor 278 are both connected with the second DC power source 184. Capacitor 278 is
connected with the anode of diode 276 and the ground connection 182. Tank capacitor 272 is
also connected the cathode of diode 276.
It is important to note that the series resonant tank circuit 150 sees all of the stray
inductances of the component combination of the inductively coupled ballast circuit 140.
This is important because the stray inductance, which is the combined inductance seen by the
series resonant tank circuit ISO, will limit the power transfer dramatically to the load (the
nonthermal plasma reactor assembly 20) under any condition outside resonance. The
inductance of the secondary coil 52 and the secondary circuit 152 are also reflected
impedance values that help determine and limit the power that is delivered to the secondary
coil 52 of the nonthermal plasma reactor assembly 20. In general, brute force
oscillator/transformer combinations have power transfer limits because of stray and reflected
inductance. In other words, the inductance of transformers and capacitors appears in series
with the load thereby limiting power transfer capability.
In the illustrated embodiment, the frequency of operation for the series resonant tank
circuit 150 is determined by the inductance of the inductive coupler 270 and the parallel
capacitance value of tank capacitors 271, 272, which will vary from application to
application depending, in large part, on the characteristics of reactor bed. Tank capacitors
271, 272 must have low dissipation factors and be able to handle high levels of current. As
noted above, the ballast circuit 140 seeks resonance through a feedback signal from the
current sensing circuit 218. The current feedback signal is proportional to the current in the
resonant tank circuit 150. The range of frequencies through which the ballast circuit 103
can search for resonance are readily varied by adjusting the values of the tank capacitors
271, 272. For example, by increasing the value of the tank capacitors 271, 272, the range
can generally be decreased.
The number of turns of wire in the primary and secondary coils of the inductive
coupler 270 will vary from application to application depending on the power requirements
of the particular nonthermal plasma reactor assembly 20. In the illustrated embodiment, litz
wire is used for the inductive coupler 270 because litz wire is especially efficient in both
performance and operating temperature, due to a fringing effect caused by the high currents
that are created while operating at high frequencies. As set forth above, the inductive
coupler 270 inductively energizes the secondary coil 52 of the nonthermal plasma reactor
assembly 20 during operation.
In the described embodiment, the primary and secondary coils of the inductive
coupler 270 are separated by an air gap. The gap between the primary and secondary coils
of the inductive coupler 270 may be used to adjust the coupling coefficient, thereby
adjusting the operating point of the nonthermal plasma reactor 20. The permeance of the air
gap between the inductive coupler 270 and the secondary coil 52 may be adjusted by
changing the distance between the inductive coupler 270 and the secondary coil 52, as
known in the art. As is apparent, the air gap within the air core transformer formed with the
inductive coupler 270 and the secondary coil 52 may be selectively adjusted to limit power
transfer from the inductive coupler 270 to the secondary coil 52. In addition, selective
adjustment of the air gap may adjust the control response of the oscillator 144. Accordingly,
selection of the permeance of the air gap balances overcurrent protection of the inductively
coupled ballast circuit 140 with the bandwidth and responsiveness of the oscillator 144 when
the secondary coil 52 is inductively energized.
As known in the art, inductive energization of the secondary coil 52 occurs when the
inductive coupler 270 induces a magnetic flux in the air gap between the secondary coil 52
and the inductive coupler 270. In the illustrated embodiments, the magnetic flux is an
alternating flux with a frequency that is preferably controlled by the oscillator 144 in an
effort to maintain resonance.
During operation, the oscillator 144 may control the frequency at close to the resonant
frequency of the series resonant tank circuit 150 and the nonthermal plasma reactor
assembly 20. As previously discussed, the positive feedback circuit 218 monitors the
reflected impedance in the series resonance tank circuit 150 to allow the inductively coupled
ballast circuit 140 to self-oscillate to a frequency which optimizes power transfer efficiency.
If, for example, the impedance reflected by the nonthermal plasma reactor assembly 14 to
the series resonant tank circuit 150 shifts slightly, the positive feedback circuit 218 may
adjust the frequency to correct for the shift in power transfer efficiency.
In the case where the impedance shifts significantly lower, such as, for example,
when the nonthermal plasma reactor 60 fails in a shorted condition, the increase in current is
limited by the air gap. As known in the art, the air gap functions to limit the amount of
impedance that may be reflected. In addition, the impedance that is reflected may result in
an impedance mismatch causing the reflection of power back to the series resonant tank
circuit 150. As is readily apparent, the reflection of power to the series resonance tank
circuit 150 may further limit power transfer to the secondary coil 52. Based on the
combination of the air gap and the resonant frequency control, the inductively coupled
ballast circuit 140 may be optimized for efficient operation while maintaining desirable
levels of overcurrent protection.
The configuration of the air core transformer provides for simple and efficient
replacement of the nonthermal plasma reactor assembly 20. In addition, the present
invention provides further advantages by providing a coupling that does not require special
contacts for the nonthermal plasma reactor assembly 20 because of the inductively coupled
ballast circuit 103. Further, the configuration eliminates the need for conductors or other
similar power transfer mechanisms that may compromise waterproofing, corrode and/or
otherwise malfunction.
Referring once again to Fig. 14, the ballast feedback circuit 122 is electrically
connected with the inductive coupler 270 of the series resonant tank circuit 150 and the
control unit 102. The ballast feedback circuit 122 provides feedback to the control unit 102
while the inductively coupled ballast circuit 103 is providing power to the nonthermal plasma
reactor 60. This allows the control unit 102 to monitor the energy being provided by the
inductive coupler 270 to the secondary coil 52 of the nonthermal plasma reactor assembly 20.
This provides the control unit 102 with the ability to determine if the nonthermal plasma
reactor 20 is on or off and also, in other embodiments, the amount of current and voltage
being applied to the nonthermal plasma reactor 20.
As depicted in Fig. 14, the ballast feedback circuit 122 includes an operational
amplifier 280, a pair of resistors 282, 284, a pair of diodes 286, 288 and a capacitor 290. The
signal from the series resonant tank circuit 150 is directed to the anode of diode 286. The
cathode of diode 286 is connected with capacitor 290 and resistor 282. In addition, resistor
282 is connected with the anode of diode 288, resistor 284 and the positive input of
operational amplifier 280. Resistor 284 is also connected with the positive input of
operational amplifier 280 and the first DC power source 180. Capacitor 290 is also
connected with the first DC power source 180, while the cathode of diode 288 is connected
with the second DC power source 184. The negative input of operational amplifier 280 is
connected directly with the output of operational amplifier 280. The output of operational
amplifier 280 is connected with the control unit 102, thereby providing the feedback signal
from operational amplifier 280 to the control unit 102.
As noted above, the secondary circuit 152 may include a capacitor 312 that changes
and limits the current supplied to the nonthermal plasma reactor 20 from the secondary coil
52 by changing the reflected impedance of the nonthermal plasma reactor 60 through the
inductive coupler 270 (see Fig. 14) of the series resonant tank circuit 150. As is apparent, by
selecting the value of capacitor 312 in view of the impedance of the nonthermal plasma
reactor 60 and the secondary coil 52, the nonthermal plasma reactor assembly 20 may be
impedance matched with the power source (the series tank circuit 150). In addition, the
nonthermal plasma reactor assembly 20 may be tuned to resonate at a frequency similar to
the resonant frequency of the series resonant tank circuit 150, thereby optimizing coupling
and minimizing reflected power.
In one embodiment, the ballast circuit 140 also includes a current limit circuit 700
designed to monitor the current produce by the circuit, and shut the circuit down when it falls
outside of desired parameters. The current limit circuit 700 can be configured to disable the
ballast circuit 103 when a current threshold is exceeded (i.e. an upper limit) or when the
current falls outside of a range (i.e. both upper and lower limits). Upper and lower limits are
particularly useful in applications where low current and unstable operation can damage the
load.
One embodiment of the current limit circuit 700 is shown in Fig. 16. The current
limit circuit 700 includes a current sensing transformer 702 that produces current
proportional to the flow of current to the primary coil 270. The current transformer 702 is
preferably created by forming a coil of wire around the core of the current sensing
transformer 232 of the current sensing circuit 218. The current from the current transformer
702 is dropped across resistor 704. Another resistor 706 is tied to the input voltage of ballast
circuit. The relationship to the input voltage causes the level to shift as the input voltage
shifts. This permits the current transformer 702 to track the real performance even as input
voltage shifts. Resistor 708 allows a voltage bias from ground that helps to raise the variable
current transformer voltage to a level detectable by the operational amplifier 710. Resistor
712 is connected between voltage source 184 and the positive input of operational amplifier
710. Resistor 714 is connected between ground connection 182 and the positive input of
operational amplifier 710. Resistors 712 and 714 establish a limit or threshold to set the
operating and non-operating modes. Resistor 716 is connected between the current
transformer 70 and the negative input lead of operational amplifier 710 to prevent the
operational amplifier 710 from drawing too much current from the current transformer 102.
The output of the operational amplifier 702 is connected to integrated circuit 720, which is
preferably a conventional latch or flip-flop, such as IC 14044. When the output from the
operational amplifier 702 is driven high, the latch is triggered, thereby latching the disable
signal. The integrated circuit 720 preferably maintains the ballast circuitlO3 in the disabled
condition until the manual reset switch 722 is pressed or otherwise actuated. Alternatively,
the reset switch 722 can be replaced by a timer circuit (not shown) that resets the current
limit circuit 700 after a defined period of time. The current limit circuit 700 may also include
a test circuit 724 that permits testing of the operation of the current limit circuit 700. The test
circuit 724 is connected to power source 184 and includes resistor 726 and switch 728.
When switch 728 is depressed or otherwise actuated, current in excess of the threshold is
applied to the operational amplifier 710. If operating properly, this current will cause the
current limit circuit 700 to disable the ballast circuit 103.
As an alternative, the current from the current transformer 702 can be monitored by a
microprocessor that is programmed to disable the ballast circuit when the current exceeds the
desired threshold or falls outside of the desired range. In some applications, however, the
microprocessor may not provide sufficient speed to provide acceptable response times.
The above description is that of various embodiments of the invention, including the
preferred embodiment. Various alterations and changes can be made without departing from
the spirit and broader aspects of the invention as defined hi the appended claims, which are to
be interpreted in accordance with the principles of patent law, including the doctrine of
equivalents. Any reference to claim elements in the singular, for example, using the articles
"a," "an," "the," or "said" is not to be construed as limiting the element to the singular.
WE CLAIM :
1. An air treatment system (10, 10") for treating air within an environment
comprising;
a housing (11, 11") having an inlet (16, 16"), an outlet (18, 18") and an air flow
path connecting said inlet (16, 16") and said outlet (18, 18");
an adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106)
disposed along said flow path;
a nonthermal plasma reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) disposed
along said flow path;
means (12, 12") for moving air from the environment through said inlet (16, 16")
along said flow path and through said outlet (18, 18") back to the environment;
means (16, 16", 18, 18") for closing at least a portion of said flow path off from
the environment, whereby said adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66,
76, 95, 96, 106) and said reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) are
segregated from the environment; and
control means (102) for operating the system in an adsorption phase during
which air from the environment is moved through the system for treatment and a
desorption/regeneration phase during which said closing means (16, 16", 18, 18") is
actuated to segregate said adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76,
95, 96, 106) and said reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) from the
environment and said reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) means is
actuated to treat contaminants within said housing (11, 11").
2. The system as claimed in claim 1, comprising recirculating means (21") for
recirculating air through said adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76,
95, 96, 106) and said reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) during said
desorption/regeneration phase.
3. The system as claimed in claim 2, wherein said absorbent material (22, 22", 38,
39, 46, 47, 48, 56, 66, 76, 95, 96, 106) is separated from said reactor (20, 20", 30, 40,
50, 60, 70, 80, 90, 100) and wherein air circulating through said adsorbent material (22,
22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) and said reactor (20, 20", 30, 40, 50, 60,
70, 80, 90, 100) carries contaminants from said adsorbent material (22, 22", 38, 39, 46,
47, 48, 56, 66, 76, 95, 96, 106) to said reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100)
for treatment.
4. The system as claimed in claim 3, wherein said recirculating means (21")
comprises an air return (31") defining an air flow path for recirculating air through the
system.
5. The system as claimed in claim 4, wherein said recirculating means (21")
comprises a means (19") for closing said air return (31") during said adsorption phase
and for opening said air return (31") during said desorption/regeneration phase.
6. The system as claimed in claim 5, wherein said adsorbent material (22, 22", 38,
39, 46, 47, 48, 56, 66, 76, 95, 96, 106) comprises an activated carbon fabric.
7. The system as claimed in claim 5, wherein said reactor (20, 20", 30, 40, 50, 60,
70, 80, 90, 100) comprises a pair of spaced apart mesh electrodes (24, 26, 24", 26", 32,
34, 36, 42, 43, 44, 45, 52, 54, 62, 64, 72, 74, 82, 84, 92, 94, 102, 104).
8. The system as claimed in claim 7, wherein said reactor (20") comprises a
dielectric material (33") disposed between said electrodes (24", 26").
9. The system as claimed in claim 8, wherein said reactor (20") comprises a
catalyst disposed between said electrodes (24", 26").
10. The system as claimed in claim 5, wherein said means for moving air is a first
fan (12, 12"), said first fan being powered off during said desorption/regeneration
phase; and
wherein said recirculating means is a second fan (35") for recirculating air
through the system during said desorption/regeneration phase.
11. The system as claimed in claim 10, comprising a HEPA filter (29") disposed
along said flow path.
12. The system as claimed in claim 5, comprising a heat source (23") for causing
thermal desorption of said adsorbent material during said desorption/ regeneration
phase.
13. The system as claimed in claim 8, wherein said dielectric material (33")
comprises alumina beads.
14. The system as claimed in claim 9, wherein said catalyst is manganese dioxide.
15. The system as claimed in claim 12, wherein said heat source (231) is a heat
lamp.
16. The system as claimed in claim 15, wherein said control means (102) comprises
means for engaging said heat lamp (23") during said desorption/regeneration phase.
17. The system as claimed in claim 1, wherein said adsorbent material (22, 22", 38,
39, 46, 47, 48, 56, 66, 76, 95, 96, 106) is disposed within said reactor (20, 20", 30, 40,
50,60,70,80,90, 100).
18. The system as claimed in claim 17, wherein said means (12, 12") for moving air
is deactivated during said desorption/regeneration phase.
19. The system as claimed in claim 18, wherein said adsorbent material (22, 22", 38,
39, 46, 47, 48, 56, 66, 76, 95, 96, 106) comprises a plurality of zeolites.
20. The system as claimed in claim 19, comprising a dielectric material (33") coated
on said zeolites.
21. An air treatment system (10, 10") comprising:
a housing (11, 11");
an adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106)
disposed within said housing (11,11");
a nonthermal plasma reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) disposed
within said housing (11, 11");
an adsorption flow path passing through at least said adsorbent material (22,
22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106), comprising an inlet (16, 16") and an
outlet (18,18");
a desorption/regeneration flow path passing through at least said adsorbent
material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) and said reactor (20, 20",
30, 40, 50, 60, 70, 80, 90,100);
controls means (102) for operating the system in an adsorption phase and a
desorption/regeneration phase, said control means comprising a means for closing
said inlet (16, 16") and said outlet (18, 18") during said desorption/regeneration phase
and opening said inlet (16, 16") and said outlet (18, 18") during said adsorption phase,
wherein during said adsorption phase said control means (102) causing air to be
moved from an environment through said adsorption flow path where said adsorbent
material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) adsorbs contaminants
carried in said air, during said desorption/regeneration phase said control means (102)
causing air to be moved through said desorption/regeneration flow path, wherein said
reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) destroys contaminants released by
said adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106).
22. The system as claimed in claim 21, wherein said adsorption flow path is at least
partially coextensive with said desorption/regeneration flow path.
23. The system as claimed in claim 21, wherein said control means (102) comprises
a means (35") for recirculating air through said desorption/regeneration flow path during
said desorption/regeneration phase.
24. The system as claimed in claim 23, wherein said desorption/regeneration flow
path comprises an air return (31") connecting a point downstream of said adsorbent
material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) and said reactor (20, 20",
30, 40, 50, 60, 70, 80, 90, 100) to a point upstream of said adsorbent material (22, 22",
38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) and said reactor (20, 20", 30, 40, 50, 60, 70,
80, 90, 100).
25. The system as claimed in claim 24, wherein said control means (102) comprises
a means (19") for closing air return (31") during said adsorption phase and opening said
air return (31") during said adsorption phase.
26. The system as claimed in claim 25, wherein said reactor (20, 20", 30, 40, 50, 60,
70, 80, 90, 100) has a pair of spaced apart electrodes (24, 26, 24", 26", 32, 34, 36, 42,
43, 44, 45, 52, 54, 62, 64, 72, 74, 82, 84, 92, 94, 102, 104).
27. The system as claimed in claim 26, wherein a dielectric material (33") is
disposed between said electrodes (24, 26, 24", 26", 32, 34, 36, 42, 43, 44, 45, 52, 54,
62, 64, 72, 74, 82, 84, 92, 94, 102, 104).
28. The system as claimed in claim 27, wherein said dielectric material (33")
comprises a plurality of alumina beads.
29. The system as claimed in claim 27, comprising a catalyst disposed in said
desorption/regeneration flow path.
30. The system as claimed in claim 29, wherein said catalyst is disposed within said
reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100).
31. The system as claimed in claim 28, comprising a catalyst coated on said
alumina beads (33").
32. The system as claimed in claim 21, comprising a heat source (23") disposed
adjacent to said adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96,
106); and
wherein said control means (102) comprises means for activating said heat
source (231) during said desorption/regeneration phase.
33. The system as claimed in claim 32, wherein said heat source (231) is a heat
lamp.
34. The system as claimed in claim 33, wherein said adsorbent material (22, 22",
38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) comprises an adsorbent fabric.
35. The system as claimed in claim 34, wherein said adsorbent material (22, 22", 38,
39, 46, 47, 48, 56, 66, 76, 95, 96, 106) is an activated carbon fabric.
36. A method for treating air in an environment comprising the steps of:
providing an air treatment system (10, 10") having an adsorbent material (22,
22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) and a nonthermal plasma reactor (20,
20", 30, 40, 50, 60, 70, 80, 90, 100) in a housing (11,11");
moving air from environment through at least the adsorbent material (22, 22", 38,
39, 46, 47, 48, 56, 66, 76, 95, 96, 106) and returning it to the environment for a period
of time during an adsorption phase;
segregating the adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95,
96, 106) and the reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) from the environment
and activating the reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) for a period of time
during a desorption/regeneration phase;
alternating operation of the system between the adsorption phase and the
desorption/regeneration phase.
37. The method as claimed in claim 36, comprising the step of recirculating air
through the adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) and
the reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) during the desorption/ regeneration
phase.
38. The method as claimed in claim 37, wherein said recirculating step involves the
step of moving air from a point downstream of the adsorbent material (22, 22", 38, 39,
46, 47, 48, 56, 66, 76, 95, 96, 106) and the reactor (20, 20", 30, 40, 50, 60, 70, 80, 90,
100) to a point upstream of the adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66,
76, 95, 96, 106) and the reactor (20, 20", 30, 40, 50, 60, 70, 80, 90, 100) through an air
return (31").
39. The method as claimed in claim 38, comprising the steps of opening the air
return (31") during the desorption/regeneration phase and closing the air return (31")
during the adsorption phase.
40. The method as claimed in claim 39, comprising the step of applying heat to the
adsorbent material (22, 22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106) during the
desorption/regeneration phase.
41. The method as claimed in claim 40, wherein said step of applying heat involves
the step of activating a heat lamp (23") located adjacent to the adsorbent material (22,
22", 38, 39, 46, 47, 48, 56, 66, 76, 95, 96, 106).
42. The method as claimed in claim 41, comprising the step of providing the reactor
(20, 20", 30, 40, 50, 60, 70, 80, 90, 100) with a pair of spaced apart electrodes (24, 26,
24", 26", 32, 34, 36, 42, 43, 44, 45, 52, 54, 62, 64, 72, 74, 82, 84, 92, 94, 102, 104).and
a dielectric material (331) disposed between the electrodes.
43. The method as claimed in claim 42, comprising the step of moving the air over a
catalyst during the desorption/regeneration phase.
44. The method as claimed in claim 43, wherein the catalyst is coated on the
dielectric material (33").
A method and apparatus (10") for reducing air contamination using a
contaminant adsorbent (22") to remove contaminants from air, and a nonthermal
plasma (20") to desorb and oxidize or detoxify the contaminants. The adsorbent
(22") may be comprised of a unique combination of a zeolite with a material
having a high dielectric value. The power supply for the nonthermal plasma
reactor (20") is designed to seek and operate at the system resonant frequency.
In one embodiment, the adsorbent material (221) is separated from the
nonthermal plasma reactor (20"). In this embodiment, heat is applied to the
adsorbent material to thermally desorb contaminants during a
desorption/regeneration phase. Air is recirculated within the system to move
desorbed contaminants from the adsorbent material to the nonthermal plasma
reactor for decomposition. The recirculating air repeatedly moves contaminants
through the reactor until they are destroyed or the desorption/regeneration phase
is complete.

Documents:

238-kolnp-2005-granted-abstract.pdf

238-kolnp-2005-granted-assignment.pdf

238-kolnp-2005-granted-claims.pdf

238-kolnp-2005-granted-correspondence.pdf

238-kolnp-2005-granted-description (complete).pdf

238-kolnp-2005-granted-drawings.pdf

238-kolnp-2005-granted-examination report.pdf

238-kolnp-2005-granted-form 1.pdf

238-kolnp-2005-granted-form 18.pdf

238-kolnp-2005-granted-form 3.pdf

238-kolnp-2005-granted-form 5.pdf

238-kolnp-2005-granted-gpa.pdf

238-kolnp-2005-granted-letter patent.pdf

238-kolnp-2005-granted-reply to examination report.pdf

238-kolnp-2005-granted-specification.pdf


Patent Number 216038
Indian Patent Application Number 00238/KOLNP/2005
PG Journal Number 10/2008
Publication Date 07-Mar-2008
Grant Date 06-Mar-2008
Date of Filing 22-Feb-2005
Name of Patentee ACCESS BUSINESS GROUP INTERNATIONAL LLC.
Applicant Address 7575 FULTON STREET EAST ADA MI 49355 USA.
Inventors:
# Inventor's Name Inventor's Address
1 KUENNEN ROY W. 7086 SUMMIT HILLCT.,CALEDONIA MI 49316, USA
2 TAYLOR ROY M 8095 COURTLAND DRIVCE ROCKFORD MI 49341 USA.
PCT International Classification Number D 04 B 15/48
PCT International Application Number PCT/US2003/024722
PCT International Filing date 2003-08-07
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/401.665 2002-08-07 U.S.A.