U.S. patent application number 11/603669 was filed with the patent office on 2008-05-22 for apparatus and method for treating impurities in air and materials.
Invention is credited to Karen Benedek.
Application Number | 20080118395 11/603669 |
Document ID | / |
Family ID | 39417141 |
Filed Date | 2008-05-22 |
United States Patent
Application |
20080118395 |
Kind Code |
A1 |
Benedek; Karen |
May 22, 2008 |
Apparatus and method for treating impurities in air and
materials
Abstract
An apparatus and method for sanitizing, decontaminating,
deodorizing, conditioning, drying, treating, cleaning, modifying
and/or otherwise improving an atmosphere within a container. The
container can be a bag or other housing for equipment, food and/or
suitable material. Ozone is generated within an atmosphere that is
exposed to the materials. The generated ozone is mixed with the
atmosphere. At least a portion of the generated ozone is then
removed from the mixed atmosphere. The apparatus and method of this
invention can be used to treat contaminated sports equipment and
the like, as well as to treat food storage atmospheres, such as
those exposed to fresh fruits and vegetables.
Inventors: |
Benedek; Karen; (Winchester,
MA) |
Correspondence
Address: |
Douglas H. Pauley;Pauley Petersen & Erickson
Suite 365, 2800 West Higgins Road
Hoffman Estates
IL
60195
US
|
Family ID: |
39417141 |
Appl. No.: |
11/603669 |
Filed: |
November 21, 2006 |
Current U.S.
Class: |
422/4 ;
422/123 |
Current CPC
Class: |
F24F 8/40 20210101; A23B
7/144 20130101; A61L 9/205 20130101; B01D 2257/7022 20130101; B01D
2257/90 20130101; A61L 9/015 20130101; A61L 2209/212 20130101 |
Class at
Publication: |
422/4 ;
422/123 |
International
Class: |
A61L 9/015 20060101
A61L009/015; A61L 9/00 20060101 A61L009/00 |
Claims
1. A method for at least one of exposed to a material sanitizing,
decontaminating, deodorizing, conditioning and drying an atmosphere
within a container, the method comprising: generating an ozone
within the atmosphere; mixing the generated ozone with the
atmosphere; and removing at least a portion of the generated ozone
from the mixed atmosphere.
2. The method according to claim 1, wherein the ozone is generated
with at least one of an ultraviolet light source and a corona
discharge device.
3. The method according to claim 1, wherein the ozone is generated
within a generation zone, the atmosphere and the generated ozone
are mixed within a mixing zone, and the mixing zone is at least one
of within the generation zone and downstream of the generation
zone.
4. The method according to claim 1, wherein at least a portion of
the generated ozone is removed within a removal zone, the
atmosphere and the generated ozone are mixed within a mixing zone,
and the mixing zone is at least one of within the removal zone and
upstream of the removal zone.
5. The method according to claim 1, wherein the generated ozone and
the atmosphere are mixed by at least one of passing the atmosphere
through a flow nozzle, passing the atmosphere across a baffle,
passing the atmosphere through a mechanical mixer, passing the
atmosphere through a changing diameter nozzle, passing the
atmosphere through a plurality of flow channels, and changing a
flow direction of the atmosphere.
6. The method according to claim 1, wherein at least a portion of
the generated ozone is removed by at least one of thermally
decomposing the generated ozone, absorbing and reacting the
generated ozone on a combusitble support, catalytically decomposing
the generated ozone, and photo-disassociating the generated ozone
with an ultraviolet light source.
7. The method according to claim 1, wherein removing the at least a
portion of the generated ozone produces a reduced atmosphere, and
the reduced atmosphere is introduced into a space of the
container.
8. The method according to claim 7, wherein the reduced atmosphere
contains at least a portion of the generated ozone.
9. The method according to claim 1, wherein the atmosphere is at
least one of heated, cooled, dried and diluted.
10. The method according to claim 1, wherein the generated ozone
removes ethylene from the atmosphere.
11. An apparatus for at least one of sanitizing, decontaminating,
deodorizing, conditioning and drying an atmosphere exposed to a
material within a container, the apparatus comprising: a structure
forming a first zone in which an ozone is generated within the
atmosphere, a second zone in which the generated ozone is mixed
with the atmosphere, and a third zone in which at least a portion
of the generated ozone is removed from the mixed atmosphere.
12. The apparatus according to claim 11, wherein at least one of an
ultraviolet light source and a corona discharge device generates
the ozone within the first zone.
13. The apparatus according to claim 11, wherein with respect to a
flow direction of the atmosphere through the structure, the second
zone is at least one of within the first zone and downstream of the
first zone.
14. The apparatus according to claim 11, wherein with respect to a
flow direction of the atmosphere through the structure, the second
zone is at least one of within the third zone and upstream of the
third zone.
15. The apparatus according to claim 11, wherein at least one of a
flow nozzle, a baffle, a mechanical mixer, and a nozzle forming a
plurality of flow channels, is at least one of mounted within and
exposed to the second zone.
16. The apparatus according to claim 11, wherein at least one of a
thermal decomposer, a combusitble support, a catalytic decomposer,
a photo-disassociating device and an ultraviolet light source is at
least one of mounted within and exposed to the third zone.
17. The apparatus according to claim 11, wherein an outlet of the
structure forms communication between the third zone and a space of
the container.
18. The apparatus according to claim 11, wherein the container is
one of a transportation trailer, a storage trailer, a storage bin,
a bag, a shipping container, an equipment bin and an expandable
structure.
19. The apparatus according to claim 11, wherein the structure is
mounted near at least one of an air conditioner and an air
mover.
20. The apparatus according to claim 11, wherein an ultraviolet
light source generates at least one of ultraviolet light at about
187 nm within the first zone and ultraviolet light at about 254 nm
within the third zone.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a material and/or air cleaning
apparatus and a method for removing impurities from the air,
resulting in air that has been deodorized, dried, sanitized,
treated, modified, improved and/or otherwise cleaned of undesired
contaminants. More specifically, this invention relates to an
apparatus and a method that uses UV light to generate ozone, uses
the ozone to destroy impurities in the air, and then uses UV light
to destroy ozone so that damaging ozone does not contact the
sensitive materials or surfaces being cleaned.
[0003] 2. Discussion of Related Art
[0004] A wide range of sports equipment is designed and used to
protect the human body from injury. Equipment pieces are relatively
large, bulky, oddly shaped, fitted with straps, and difficult to
wash and dry. In soccer, a player wears shin guards and ankle
guards to protect the lower leg. In hockey, a player wears knee
pads, a chest protector, elbow pads, gloves, a helmet and hockey
pants. In football, a player wears shoulder pads, leg and hip pads,
a helmet, a neck roll, elbow pads and gloves. Bicyclists and roller
blade skaters use helmets. Many sports require general or
specialized footwear, such as cleats, sneakers, spikes, skates,
roller blades and the like. Workers can wear similar equipment.
[0005] Protective equipment can be worn with direct contact against
a skin or a head surface. Whether the equipment directly contacts
the human body or is separated by clothing or a piece of cloth,
sweat soaks into materials, such as pads, elastic material, straps,
foam, and other materials. If not properly dried or cleaned, the
sweat-soaked equipment becomes a site for growth of bacteria, mold,
mildew, fungus, and other microorganisms that can spread disease,
cause odor and/or damage or discolor the equipment. The equipment
and the bag, bin or other storage container can become malodorous.
Odors from the equipment can emanate from or through the container
and make unpleasant the corresponding room, such as a vehicle
compartment. Merely blowing air across the equipment to dry the
equipment can more broadly release odors from the evaporated sweat
and moisture into the room, house or other compartment. It is
desirable to have an apparatus and/or method for drying,
deodorizing, and/or sanitizing equipment, quickly and
conveniently.
[0006] Known products in the marketplace have addressed this need.
Dhaemers, U.S. Pat. No. 6,134,806 describes a portable sport
equipment bag having an air distributor connected with a hose to a
blower and an ozone generator operable to move pressurized air and
ozone into the air distributor. The air distributor moves the air
and ozone into the bag to dry the sports equipment contained within
the bag, to destroy bacteria, molds and fungus in the bag. The
ozone directly contacts the sports equipment, which can be a
serious problem because ozone can destroy many equipment materials,
such as when the ozone exists in air at concentrations that are
high enough to kill undesirable microorganisms. When well mixed
with contaminated air, ozone can more effectively and efficiently
oxidize contaminants. Also, ozone is a lung irritant and can leak
out of the equipment bag and dangerously be inhaled, such as when
the user opens the sports equipment bag. These safety issues can be
serious enough to warrant alternative approaches.
[0007] Dhaemers, U.S. Pat. No. 5,369,892 describes a dryer in the
form of an armoire with an internal drying chamber for housing
articles that are subjected to heated circulating air, to remove
moisture from the articles. Ultraviolet lamps within the drying
chamber destroy contaminants in the air and on the air conditioning
coils, in the drying chamber. A similar configuration is taught by
Liang, U.S. Pat. No. 5,152,077, which is limited because
contaminated materials must be in a direct line of sight of a UV
light source, in order to be sanitized. The clothes alone can
restrict exposure between the material and the UV light. Air that
circulates in the armoire cannot be deodorized.
[0008] There is a need for a convenient, efficient, cost effective
and efficient method and apparatus for drying, deodorizing and/or
sanitizing air and equipment, particularly without damaging the
equipment.
[0009] Many other types of products can benefit from being dried,
sanitized and deodorized, such as toys used at home or in
commercial or institutional settings, including health care
facilities, day care centers and/or schools. The materials used in
toys and stuffed animals makes it difficult to clean them quickly
and conveniently. Many toys need to be individually wiped with
disinfectant to clean their surfaces. Disinfectants and wipes can
be used to clean toys. These cleaning procedures are time consuming
and burdensome.
[0010] There is a need for a method and apparatus for drying,
deodorizing, and/or sanitizing a variety of products, quickly,
safely and/or effectively, with minimal physical or chemical impact
to the products.
[0011] Ethylene gas (C.sub.2H.sub.4) accumulates during the
transport and storage of fresh fruits and vegetables and thus
causes a problem for commercial agriculture and consumers. Small
amounts of ethylene, sometimes less than 1 ppm, can induce fruit
ripening, and can produce undesirable flavors such as bitterness,
colors, such as yellowing or browning, and textures, such as
softening, and thus can increase susceptibility to disease. Certain
fruits and vegetables naturally generate ethylene during a ripening
cycle. Other fruits and vegetables are highly sensitive to the
presence of ethylene, but may or may not actually produce ethylene.
The table in FIG. 16 lists some fruits and vegetables and known
ethylene production rates and sensitivities.
[0012] The amount of ethylene that produces undesirable amounts or
characteristics varies with different fruits and vegetables, but
ethylene concentrations in the range of 0.1-10 ppm can produce a
significant effect. There is a need for a system that removes
ethylene from the air within a fruit or vegetable storage container
while not damaging the fruits or vegetables.
[0013] Because there is significant industry value in maintaining
fresh fruits and vegetables during transportation and storage, some
technologies have been researched, developed and commercialized to
control ethylene. These conventional methods and their limitations
are shown in the table of FIG. 17.
[0014] There is a need for an alternative approach to ethylene
control that would be less expensive, consume less power, and
require less space.
SUMMARY OF THE INVENTION
[0015] It is one object of this invention to provide an apparatus
and method for oxidizing the ethylene to carbon dioxide and water
using UV-generated ozone.
[0016] It is another object of this invention to produce ozone to
destroy ethylene and then to dissociate the excess ozone back to
oxygen, to maintain acceptable levels of ozone within a shipping or
storage container, for example that carries fresh fruits and
vegetables.
[0017] According to this invention, ethylene can be oxidized in an
ethylene control unit and/or in ambient air of the storage
container, such as at a lower ozone concentration. This dual
approach can maximize ethylene removal from the container air
and/or the produce packages. This dual approach can also minimize
negative effects of ozone concentrations in an air handling system
or in the produce itself. UV-generated ozone can also be used to
remove additional pathogens that can degrade produce quality, such
as with certain fungus or mold spores. The apparatus and method of
this invention can meet application requirements of a wide range of
container sizes and refrigeration or other environmental control
systems.
[0018] The method and system of this invention can generate, use,
and destroy ozone, for example to remove ethylene and/or other
impurities in the air or atmosphere within fresh fruit and
vegetable containers. In one embodiment of this invention, ozone is
both generated and destroyed by UV light rays. The ethylene removal
apparatus and/or method can be accomplished with a wide variety of
known configurations of storage containers, air flow patterns
and/or refrigeration units.
[0019] According to this invention, it is possible to dry,
deodorize and sanitize materials and their surrounding air. The
materials can be sports equipment stored in a sports bag or an
equipment bin, toys stored in a toy box and/or fruits or vegetables
stored in a refrigerator or produce storage container.
[0020] According to this invention, it is possible to clean,
deodorize, and sanitize materials by circulating cleaned and
conditioned air across the materials. The contaminants that are
transferred from the materials to the air are treated in an air
cleaning unit. The cleaned air is circulated back across the
materials, such as in a convective manner. Air flow and/or heat can
be used to drive the contaminants from the materials into the air.
The contaminants can be, for example, moisture, volatile matter,
such as odors, bacteria, spores, dirt, or other gases, liquids
and/or microorganisms.
[0021] The contaminants that are driven into an air stream can be
drawn into a compact, low-cost, effective cleaning unit where the
contaminants are destroyed. The cleaned air can be re-circulated
back to the storage container.
[0022] This invention provides a method and device to generate,
use, and ultimately at least partially destroy the generated ozone
for decontamination, deodorization, and/or conditioning of the air
and/or the materials. The air cleaning unit can be positioned
inside a chamber of various suitable configurations or designs. Air
that requires cleaning and deodorization is drawn from the chamber
into the cleaning unit, passes across an ozone generator, such as a
UV bulb that emits light rays in the UV wavelength that generates
ozone. The ozone-laden, contaminated air can be further drawn
through a mixing zone to establish enhanced contact between the
generated ozone and the contaminants. The clean air is then drawn
across a second UV bulb that emits in the UV wavelength that
destroys ozone. Clean, ozone-free air is then reintroduced to the
storage chamber.
[0023] One or more additional treatment devices may be placed in
the chamber to heat, dry, cool or dilute the air stream that
circulates through the air cleaning unit.
[0024] The system of this invention, which includes the apparatus
and/or the method, can produce ozone to destroy contaminants and
then used to dissociate the excess ozone back to oxygen in order to
maintain appropriate levels of ozone within the storage container.
The system of this invention provides a number of significant
benefits compared to existing technology.
[0025] Circulation of air and ozone through a well designed mixing
unit can be more efficient at cleaning the air than by injecting
gaseous ozone, at non-hazardous levels, into still or calm air or
other ambient conditions. It appears that at low concentrations of
ozone, random encounters with contaminants is too slow of a
process. However, there can be significant benefits to combining
both of these methods to maximize benefits from ozone use.
[0026] This invention provides two opportunities to oxidize the
odors and the microorganisms, one in an air cleaning unit, and the
second, such as at a lower ozone concentration, in the ambient air
of the storage container. This dual approach can better remove
impurities from the air in the storage container and from surfaces
of the materials. Ozone concentrations are relatively high in the
air cleaning unit and the mixing rates between the ozone and the
air is relatively high, and thus the oxidation rates of the
impurities is relatively high. The air in the storage container can
be quickly deodorized and sanitized. The concentration of ozone at
the exit of the air cleaning unit can be precisely established. A
very low concentration of ozone can be established in the storage
container in order to sanitize surfaces of the materials, such as
over a longer period of time. This dual approach can minimize
negative effects of ozone concentrations in the air handling system
or the surface of the sports or other equipment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The above and other features and objects of this invention
are better understood from the following detailed description taken
in view of the drawings wherein:
[0028] FIG. 1 is a diagrammatic view showing three elements of an
air cleaner, including an ozone generation zone, a mixing zone and
an ozone dissociation zone, according to one embodiment of this
invention;
[0029] FIG. 2 is a diagrammatic showing an inside of a container,
such as a refrigerated truck trailer, a housing and an evaporator,
an air cleaner, and a material or product, according to one
embodiment of this invention;
[0030] FIG. 3 is a diagrammatic side view of a cylindrical
configuration of an air cleaner unit, according to one embodiment
of this invention;
[0031] FIG. 4 is a diagrammatic partial sectional view of an air
cleaner unit, according to one embodiment of this invention;
[0032] FIG. 5 is a diagrammatic partial sectional view of an air
cleaner unit, according to another embodiment of this
invention;
[0033] FIG. 6 is a diagrammatic partial sectional view of an air
cleaner unit, according to one embodiment of this invention;
[0034] FIG. 7 is a diagrammatic partial section view of an air
cleaner unit, according to one embodiment of this invention;
[0035] FIG. 8 is a diagrammatic perspective view of an air cleaner
unit, according to one embodiment of this invention;
[0036] FIG. 9 is a diagrammatic perspective view showing a section
of the air cleaner unit, as shown in FIG. 8;
[0037] FIG. 10 is a diagrammatic sectional side view of the air
cleaner unit, as shown in FIG. 8;
[0038] FIG. 11 is a schematic perspective view of an air cleaner
unit, according to one embodiment of this invention;
[0039] FIG. 12 is a schematic sectional view showing an air cleaner
mounted to a housing, according to one embodiment of this
invention;
[0040] FIG. 13 is a schematic top view of the air cleaner unit, as
shown in FIG. 12;
[0041] FIG. 14 is a schematic side view of the air cleaner unit, as
shown in FIG. 12;
[0042] FIG. 15 is table showing ozone-generating ultraviolet light
performance parameters;
[0043] FIG. 16 is a table showing ethylene production and
sensitivity of selected produce;
[0044] FIG. 17 is a table showing conventional ethylene control
technologies and corresponding limitations; and
[0045] FIG. 18 is a graph showing a reduction of ozone using
ultraviolet light, according to one embodiment of this
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0046] Throughout this specification and in the claims, the term
air cleaning unit is intended to relate to an apparatus for
sanitizing, decontaminating, deodorizing, conditioning, drying
and/or otherwise treating, cleaning, modifying and/or improving an
atmosphere within a container.
[0047] FIG. 1 shows air cleaning unit 40, according to one
embodiment of this invention. FIG. 2 shows air cleaning unit 40
positioned or mounted within container 32, such as a truck trailer,
according to one embodiment of this invention. FIG. 3 shows air
cleaning unit 40 positioned or mounted within a different container
32, according to another embodiment of this invention.
[0048] As shown in FIG. 1, air cleaning unit 40 has structure 42,
such as a housing, that forms zone 44, zone 46 and zone 48. As air
or another suitable atmosphere passes through air cleaning unit 40,
such as shown by the arrows of flow direction 41, in FIG. 1,
atmosphere 33 passes first through zone 44, then through zone 46,
and then through zone 48.
[0049] In certain embodiments according to this invention, ozone is
generated within atmosphere 33 passing through zone 44. The
generated ozone is mixed with atmosphere 33, through zone 46. At
least a portion of the generated ozone is removed from the mixed
atmosphere, within zone 48. Thus, as the atmosphere discharges from
zone 48, the atmosphere has been exposed to generated ozone, mixed
with the generated ozone and then disassociated from at least a
portion of the generated ozone.
[0050] FIGS. 4-7 each shows a different embodiment of air cleaning
unit 40, according to this invention. As shown in FIGS. 4-7, UV
source 50 comprises a light bulb with an ultraviolet output and/or
a corona discharge device that generates ozone within zone 44. Any
other suitable mechanical, electro-mechanical and/or other device
can be used to generate ozone within zone 44.
[0051] FIGS. 1 and 2 show zone 48 downstream with respect to zone
46, and zone 46 downstream with respect to zone 44. In other
embodiments according to this invention, zone 46 which is the
mixing zone can be at least partially within or part of zone 44
where ozone is generated. In other embodiments according to this
invention, zone 48 in which ozone is removed can be at least
partially within or part of zone 46, in which mixing occurs. In
other embodiments according to this invention, mixing, such as in
zone 46, can occur entirely throughout zones 44 and/or 48.
[0052] FIG. 1 shows flow diverter 54 positioned within zone 46. In
other embodiments according to this invention, flow diverter 54 can
be mounted within or exposed to zone 44 and/or zone 48. Flow
diverter 54 can be any suitable device that mixes fluid flowing
through air cleaning unit 40, including but not limited to a flow
nozzle, a baffle, a structure, a mechanical mixer and/or a nozzle,
such as a nozzle forming a plurality of flow channels.
[0053] As shown in FIGS. 1 and 4-7, for example, mixing can occur
by forming a nozzle that has a variable diameter along a flow
direction of the atmosphere flowing through air cleaning unit 40.
Any suitable venturri nozzle or other converging and/or diverging
nozzle can be used to mix the fluid flow.
[0054] Any suitable conventional device for removing ozone can be
mounted within or exposed to zone 48. In certain embodiments
according to this invention, ozone can be removed or disassociated
from zone 48 with a thermal decomposer, a combustible support, a
catalytic decomposer, a photo-disassociating device and/or an
ultraviolet light source.
[0055] In certain embodiments according to this invention, the UV
light is generated at a wavelength of about 187 nm to absorb oxygen
and thus produce ozone, such as within zone 44. In certain
embodiments according to this invention, the UV light is generated
at a wavelength of about 254 nm to absorb the ozone and cause
photolysis or photo-disassociation. FIG. 18 shows a graph of
reducing ozone with ultraviolet light at about 254 nm.
[0056] As shown in FIGS. 2 and 3, for example, an outlet of
structure 42 which forms air cleaning unit 40 is in communication
with zone 48 and atmosphere 33 or the space of container 32. As
shown in FIGS. 2 and 3, material 34 is mounted, positioned or
otherwise housed within container 32 so that material 34 is exposed
to atmosphere 33.
[0057] Also shown in FIGS. 2 and 3, air mover 36 can be used to
circulate atmosphere 33. Any suitable fan or other air moving
device can be used to create flow of atmosphere 33 through air
cleaning unit 40. As shown in FIG. 2, air conditioner 35, such as
an evaporator or any other suitable air conditioning device, is
mounted within atmosphere 33 of container 32.
[0058] Container 32 can comprise any suitable structure that
defines a chamber or other suitable space for accommodating
material 34. Container 32 can be formed by a transportation
trailer, a storage trailer, a storage bin, a bag, a shipping
container, an equipment bin and/or an expandable structure.
[0059] In certain embodiments according to this invention, the
method for sanitizing, decontaminating, deodorizing, conditioning,
drying or otherwise treating atmosphere 33 begins with generating
ozone within atmosphere 33 passing through zone 44. Within zone 46,
the generated ozone is mixed with the atmosphere 33 to enhance
removal of undesirable contaminates or other elements of atmosphere
33. At least a portion and possibly the entire amount of generated
ozone is removed from the mixed atmosphere 33 as it passes through
zone 48.
[0060] It is possible to mix atmosphere 33 with the generated ozone
within zone 44 and/or zone 46. It is possible to continue to mix
atmosphere 33 with the generated ozone as it passes through zone
48.
[0061] The apparatus of this invention can comprise a control unit,
for example located at the exit of the evaporator. The control unit
can comprise three sections, including a UV-light (187 nm) ozone
generation chamber for generating a relatively high ozone
concentration, a mixing zone for removeing ethylene with ozone, and
a UV-light (254 nm) ozone dissociation chamber for destroying ozone
to a level desired for the atmosphere in the container.
[0062] The units of this invention can have a low pressure drop and
may use a conventional or existing air handler and/or refrigeration
system. The ducting and unit structure can be fabricated from
plastics, such as PVC, CPVC or from sheet metal with a suitable
coating, such as a PTFE coating. The volume of the apparatus can be
designed as a function of a size of an evaporator outlet, such as
if ducting needs to interface with the refrigeration unit. In
certain embodiments, the total volume of the ECU and the ducting
connecting it to the evaporator outlet can be approximately 3-5
cubic feet. The UV bulb life can be about 10,000 hours. It is
possible that no other part require maintenance in the apparatus,
according to certain embodiments of this invention.
[0063] It is possible to estimate the required ozone generation
capacity of the ozone generation chamber. The required ozone
generation rate can be a function of an expected ethylene
generation rate. The stoichiometric requirement for oxidation of
ethylene by ozone is four moles of ozone for each mole of ethylene
destroyed, assuming that only the oxygen radical participates in
the oxidation of the hydrocarbon.
4O.sub.3+C.sub.2H.sub.4.fwdarw.2CO.sub.2+2H.sub.2O+4O.sub.2
[0064] Thus, with an ethylene generation scenario having an
estimated production of 1 liter per day of ethylene gas in a 20'
shipping container, there is a need of 4 liters per day of ozone
generation to destroy the ethylene. This volumetric production rate
of ozone corresponds to about 0.3 grams per hour of ozone
production. Using a design factor of about 10, assuming that only
10% of the UV light emitted by a lamp is absorbed by oxygen, with
the remainder absorbed by walls of the duct work, there can be an
upper limit on size, power and cost estimates. The performance of
commercially available ozone-generating UV lamps is shown in the
table of FIG. 15. A U-shaped lamp, 14'' long that draws 32 Watts of
power can generate the desired level of ozone, such as 3.0 grams
per hour.
[0065] Instead of estimating an absorption of 10%, an efficiency of
UV radiation utilization is calculated using the Beer-Lambert law
for attenuation of light traveling through an absorbing medium.
Log(I/Io)=-(a)(p)(l)
[0066] Where
[0067] Io=intensity of light entering the layer of air
[0068] I=intensity of light leaving the layer of air
[0069] a=absorption coefficient=(0.1)
[0070] p=partial pressure of oxygen in air (0.2)
[0071] l=absorption path length
[0072] According to the Handbook of Ozone Technology and
Applications (Rice 1984), for oxygen and UV light at a wavelength
of 187 nm, "a" is approximately 0.1 atm.sup.-1cm.sup.-1. The
partial pressure of oxygen in air is 0.21. With a duct diameter of
about 30 centimeters (approximately 1 foot), the absorption of the
UV light I/Io will be 0.73, and an expected absorption of the UV
light is 27%. Thus, an assumption of 10% is a conservative design
approach.
[0073] The required volume of the ozone generation chamber can be
relatively small, for example approximately 1.2 cubic feet, given a
duct diameter of 1 foot and a duct length of about 1.5 feet, to
accommodate the UV lamp and associated mounting hardware and a
ballast.
[0074] The geometry of the mixing chamber can be determined as a
function of the actual use or the proposed program. The mixing
chamber can have a simple design, such as a continuation of the
duct from the ozone generation chamber with at least some change in
duct diameter, in order to enhance mixing. A simple, low pressure
drop mixing chamber configuration is shown in FIG. 1.
[0075] In an ultraviolet (UV) light system, there are two spectral
lines that are pertinent to ozone formation. UV light at a
wavelength of 187 nm is absorbed by oxygen and causes ozone
production. UV light at a wavelength of 254 nm is absorbed by ozone
and causes photolysis or photo-dissociation of the ozone. An
equivalent lamp to the one selected above, with a glass tube
designed to emit at a 254 nm wavelength, will break ozone down to
oxygen with an efficiency such as shown in the graph of FIG.
18.
[0076] At least some, most or all of the ozone can be removed in
the later or downstream chamber of the ECU. For a variety of
reasons, it may be desirable to maintain a low level of ozone in
the ambient air of the container, for example to have an
opportunity to diffuse the ozone into the produce cartons and to
oxidize the ethylene in situ. The ozone removal chamber can be
sized to achieve the desired exit concentration of ozone. The size
and thus residence time of the ozone removal chamber can be
estimated by calculating or measuring a UV lamp intensity
throughout a duct, and setting the desired ozone concentration at
the end of the duct. The resultant residence time sets the required
duct length for the desired degree of ozone reduction.
[0077] The geometry of the ozone removal chamber can set the ozone
removal properties of the system. It is possible to also use an
operating sequence. For example, UV lamps can be set to sequence on
so that the ozone removal lamp stays on longer than the ozone
generating lamp, the chamber size remains small, and the air
continues to cycle through the ethylene removal unit after the
ozone generation lamps are turned off.
[0078] While in the foregoing detailed description this invention
has been described in relation to certain preferred embodiments
thereof, and many details have been set forth for purposes of
illustration, it will be apparent to those skilled in the art that
this invention is susceptible to additional embodiments and that
certain of the details described herein can be varied considerably
without departing from the basic principles of this invention.
* * * * *