Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02249966 1998-10-09
METHOD AND SYSTEM FOR ULTRAVIOLET RADIATION
STERILIZATION OF GASES AND FLUIDS
Field of the Invention
The invention relates in general to apparatuses and processes for
sterilization
of gaseous and liquid media, more particularly, to a method and apparatus for
improving the quality of indoor air and drinking water by means of ultraviolet
radiation sterilization.
1 o Background of the Invention
The provision of clean and safe drinking water is essential for human health
and life. As clean water sources diminish researchers have tried to develop
various
sterilization methods and systems for water and air that include the use of
ultraviolet
radiation. The main problems associated with known ultraviolet radiation air
15 sterilization methods and systems are the high cost of ultraviolet lamps
incorporated
within such and low apparatus outputs.
In order to treat the water, using ultraviolet lamps, the water must be made
to
flow close to the lamp and in a layer which should be as shallow as possible
since
ultraviolet rays are quickly absorbed by the water (which should be perfectly
clear).
2 o In all known apparatuses for ultraviolet radiation sterilization of indoor
air and
drinking water, it is realized at a uniflow of media along the ultraviolet
lamps. Most
apparatuses provide an exposure time of approximately 3.5 to 4.0 seconds which
is
suitable for layers or depths of approximately 3.5 to 4.0 centimeters. It is
possible to
increase the exposure time in the case of greater depths. However, then the
apparatus
2 5 may become unduly inefficient. High-intensity ultraviolet lamps need water
cooling
for indoor air processing.
Accordingly, the principal object of this invention is to provide a unique
method and a system for ultraviolet radiation sterilization of gases and
fluids in a cost
efficient and effective manner.
Summary of the Invention
It is an aspect of the present invention to provide an ultraviolet radiation
screw
conveyor system for sterilization of gaseous and liquid media that does not
require
CA 02249966 1998-10-09
revolving components. Alternative embodiments depend on the operating
temperature
for the ultraviolet radiation screw conveyor system since a coefficient of
linear
expansion of the system materials should be taken into account.
Yet another aspect of the present invention is a method for sterilizing gases
and
fluids, said method comprising:
passing a gas or fluid in a rotatively translational motion along the entire
length
of an ultraviolet lamp for a time sufficient to destroy bacteria and viruses
contained
within said gas or fluid, and
collecting said irradiated gas or fluid.
i o A further aspect of the present invention is an ultraviolet radiation
sterilization
device for liquids and gases, said device comprising:
a hollow housing;
an ultraviolet light source positioned within said housing; and
helicoid flights positioned along the entire length of said ultraviolet light
source
1 s forming a continuous helix, wherein liquids and gases pass along said
continuous helix
along the entire length of said ultraviolet light source.
Yet another aspect of the present invention is an ultraviolet radiation
sterilization device for liquids and gases, said device comprising:
a hollow housing,
2 o a hollow transparent conveyor screw positioned within said housing; and
an ultraviolet light source positioned within said hollow transparent conveyor
screw.
Yet a further aspect of the present invention is an apparatus for
sterilization
liquids and gases, said apparatus comprising:
2 s a plurality of sterilization devices comprising a hollow housing; an
ultraviolet
light source positioned within said housing; and helicoid flights positioned
along the
entire length of said ultraviolet light source forming a continuous helix;
means to introduce liquids and gases into said devices and pass along said
continuous helix along the entire length of said ultraviolet light source; and
3 o means to collect the irradiated liquid or gas.
CA 02249966 1998-10-09
Brief Description of the Drawings
A detailed description of the preferred embodiments are provided herein below
with reference to the following drawings, in which like numerals denote like
parts
throughout, and in which:
s Figure 1 is a side elevational view illustrating an embodiment of the
present
invention;
Figure 2 is a side elevational view of the screw of Figure 1 with a portion of
the
tubular body broken away;
Figure 3 is a side elevational view of an ultraviolet lamp of Figure 1;
1 o Figure 4 is a side elevational view of a sectional assembly of the screw
of
Figure 2 and ultraviolet lamp of Figure 3;
Figure 5 is a side elevational view of a second embodiment of the assembly
from the sectional assembly of Figure 4 and a housing (conveyor pipe) that
forms a
finished ultraviolet radiation screw conveyor system;
1 s Figure 6 is a schematic diagram illustrating the use of the ultraviolet
radiation
screw conveyor system in an apparatus for the sterilization of fluids;
Figure 7 is a side cross-sectional view of a chamber apparatus with standard
ultraviolet low pressure mercury vapor lamps for residential use taken on line
1-1 of
Figure 8.
2 o Figure 8 is a cross-sectional view taken on line A-A of Figure 7; and
Figure 9 is a side cross-sectional view of another embodiment of the
invention.
In the drawings, preferred embodiments of the invention are illustrated by way
of example. It is to be expressly understood that the description and drawings
are only
2 s for the purpose of illustration and as an aid to understanding, and are
not intended as a
definition of the limits of the invention.
Detailed Description Of The Preferred Embodiments
A first embodiment of the ultraviolet radiation screw conveyor system of the
s o present invention is shown with reference to Figure 1. It should be noted
that the
system does not require revolving components. The system comprises a conveyor
housing (pipe) 1, helicoid flights 2 (forming a continuous helix), and a
single standard
ultraviolet lamp 3. The helix of the screw is mounted preliminary on a hollow
tube
3
CA 02249966 1998-10-09
having outside diameter equal to an outside diameter of an envelope of the
ultraviolet
lamp 3. The outside diameter (OD) of the screw helix is equal to the inside
diameter
(ID) of the conveyor housing (pipe) 1.
The screw and conveyor housing (pipe) 1 should have a tight fit in the
s assembly. The tight fit can be achieved by heating the conveyor housing
(pipe) 1 prior
to its assembly with the screw and afterwards, cooled down. The hollow tube of
the
screw is subsequently drilled through, thus forming through holes in the screw
flights.
The diameter of the through holes is equal to the outside diameter of the
envelope of
UV lamp 3. The LJV lamp is inserted into the through holes of the screw
flights. This
1 o new assembly should also have a tight fit. This is how a first embodiment
of said
system is manufactured.
If the system operates at a temperature less than about 65°C, the
conveyor
housing (pipe) 1 and the screw helix can be manufactured from aluminum. If the
system operates at a higher temperature, for example about 126.7°C
(260°F), the
1 s components should be manufactured from quartz or other materials with the
same
coefficient of linear expansion as quartz (e.g. some types of special fire
resistant
ceramics). The inside surface of the conveyor housing (pipe) 1 should be
coated with
a substance that reflects ultraviolet radiation.
In the system the single standard ultraviolet lamp 3 performs two functions,
and
2 o is the most important feature in the system. In addition to its standard
fi~nction, i.e. a
source of ultraviolet radiation, the standard ultraviolet lamp performs the
second
function of a conditional screw shaft, i.e. it is an integral component of the
screw
conveyor system. This causes the system to not require revolving parts.
The invented system can operate in vertical, inclined or horizontal positions
in
2 s order to process fluids and gases. The material can be fed from either top
or bottom
depending on the system apparatus designs.
The larger the number of coils passed by the processed gas or fluid media
inside the system, the longer the passage in contact with the UV lamp and the
higher
the specific area of the contact. Thus, the material to be sterilized performs
rotatively-
3 o translational motion around and along the lamp. In such a manner,
substantial
quantities of material (gases or fluids) may pass in close proximity to a
single lamp in
larger volumes while maintaining the kill rate of the microorganisms therein.
The pitch
of the screw flights determines the number of the coils. As the material goes
through
4
CA 02249966 1998-10-09
the invented system it gets agitated and even the most remote bacteria in the
gas or
fluid comes in close contact with UV lamp, while the bacteria in proximity to
the UV
lamp moves to the periphery. This reduces the exposure time and increases
cooling of
the entire system, which is especially important for indoor air sterilization.
Proper
s cooling allows the use of ultraviolet lamps of higher intensity. The latter
seems to
speak in favor of the a Double Flight Short Pitch Conveyor Screw. However,
such
design causes the invented system to be more complicated to manufacture and
increases the power consumption required to pump the gas or fluid through the
system. Therefore, a Single Short Pitch Conveyor Screw was chosen wherein the
1 o direction of screw flights can be either left-handed or right-handed.
When the ultraviolet radiation screw conveyor system is used in the apparatus
for residential use, there is no need for high capacity, while low price is
the decisive
factor on the market. In this case, the pitch of screw flights should be
larger. For
instance, when the inside diameter (ID) of the conveyor housing (pipe) 1 is
114 mm
i s and the diameter of the ultraviolet lamp envelope is 38 mm, the optimum
pitch of the
screw flights, in terms of power required for pumping indoor air through the
system, is
38 mm (Figure 9).
In other types of apparatus having similar ID of conveyor housing (pipe) 1,
the
pitch of screw flights may vary from 19 mm to 38 mm. Although the lower limit
is
2 o possible.
A second embodiment of the present invention is shown in Figures 2 - S. This
embodiment for the ultraviolet radiation screw conveyor systems comprises a
conveyor
screw 4 with a hollow tube as a single whole; a standard ultraviolet lamp S
which
embodies the invention and a conveyor housing (pipe) 6.
2 s The ID of the screw hollow tube (screw pipe shaft) is equal to the OD of
an
envelope of ultraviolet lamp S envelope. The OD of the screw helix is equal to
the ID
of the conveyor housing (pipe). The assembly of conveyor screw 4 with
ultraviolet
lamp 5 should have a tight fit. This can be achieved by heating the conveyor
screw
prior to assembly. The conveyor housing (pipe) 6 is then heated to the
permissible
30 limit, and the assembly inserted. The system is completed after it has been
cooled
down, and the inside surface of the conveyor housing 6 is coated with
ultraviolet
radiation reflecting coating.
CA 02249966 1998-10-09
The conveyor screw 4 (Figure 2) is made of quartz. The conveyor pipe 6 can
be manufactured either from quartz or any other material with the same
coefficient of
linear expansion as quartz.
The principle of operation for both embodiments is the same.
s As shown in Figure 6, the fluid to be sterilized may be collected in
collection
tank 7. The fluid is then pumped by pumps 11 through separate conduits to
individual
ultraviolet radiation screw conveyor systems 8 and flows therethrough in the
direction
indicated by the arrows. Thus, the fluid must travel around and along
ultraviolet lamps
9 numerous times before exiting into collection tank 10.
1 o Figures. 7, 8 and 9 show two apparatuses of the same design for indoor air
sterilization in the rooms. There is only one difference between the
apparatuses. The
germicidal units in the first apparatus (Figures 7 and 8) are designed as
chambers in the
form of tubes with standard ultraviolet lamps mounted inside. The germicidal
units in
the second apparatus (Figure 9) are designed as ultraviolet radiation screw
conveyor
1 s systems with the same standard ultraviolet lamps. The following table
presents their
test results.
6
CA 02249966 1998-10-09
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o
~ W o
o M ~ ~ 00 M
~
l~ M N
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CA 02249966 1998-10-09
Table 1 shows that the capacity and efficiency of the second apparatus
supercedes the first design to such an extent that it can be graded as an
apparatus of
the new generation. Also, higher intensity ultraviolet lamps can be used in
the second
apparatus due to the better cooling effect provided by the system invented by
us. This
enhances the apparatus performance. Consequently, the method and said system
of
this invention may be readily used as a means for sterilizing large quantities
of gases
and fluids which have heretofore been unattainable.
Although preferred embodiments have been described herein in detail , it is
1 o understood by those skilled in the art that variations may be made thereto
without
departing from the scope of the invention or the spirit of the appended
claims.
