CA2249966A1

CA2249966A1 - Method and system for ultraviolet radiation sterilization of gases and fluids

Info

Publication number: CA2249966A1
Application number: CA 2249966
Authority: CA
Inventors: Leonid Pavlov
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-10-09
Filing date: 1998-10-09
Publication date: 2000-04-09

Abstract

The present invention relates to a method for sterilizing gases and fluids, the method comprises 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 the gas or fluid, and collecting the irradiated gas or fluid.

Description

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 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.

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 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 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.

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.

~O O

o ~ W o o M ~ ~ 00 M
~

l~ M N

O M M N

~n M ~ N ~ v~

00 ~O d' '~t o0 O o ~" ~ Ov N M ,n M r' lD

O

M M ~ .-~ ~O N

O ~O

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M M ~ ~ Q\ M

C N

O
O~ ~n O

M M n N

N

M M ' \

C oo ~ ,~ N

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C/~ O O
O~ C

~

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~

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O

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~ ~ ~ i O

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y ~ M ~ O
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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.

Claims

1. 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.

2. 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 forming a continuous helix, wherein liquids and gases pass along said continuous helix along the entire length of said ultraviolet light source.

3. An ultraviolet radiation sterilization device for liquids and gases, said device comprising:
a hollow housing, a hollow transparent conveyor screw positioned within said housing; and an ultraviolet light source positioned within said hollow transparent conveyor screw.

4. An apparatus for sterilization liquids and gases, said apparatus comprising:
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;
means to collect the irradiated liquid or gas.

5. The apparatus of claim 4, wherein said apparatus is provided within a portable containment unit comprising a housing having a bottom portion with castor wheels mounted thereto and lid.