Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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GAS INJECTION METHOD AND APPARATUS
INTRODUCTION
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This invention relates to a method of adding gas
to a liquid and, more particularly, to a method and
apparatus for introducing gas to a liquid which liquid and
gas mixture is then passed through a static aeratorO
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BACKGROUND OF THE INVENTIQN '
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In U.S. Patent 4,749,527 entitled STATIC AERATOR
and assigned to the same owner as the present application,
there is disclosed a static aerator used to mix a gas and
liquid. Such mixing is done, for example, to enhance
liquid oxygenation of a liquid such as sewage effluent to
enhance sewage breakdown. The method and apparatus
disclosed in tha '527 patent improves the gas and liquid
mixing. The use of the aerator according to the '527
patent creates rotational acceleration in the liquid by
the helical blade of the aerator which increases as the
liquid moves around the spiral as it traverses the liquid ~ ~ ;
conduit in which the aerator is located. As the
acceleration increases, the pressure on the liquid
likewise increases. This increases the absorbtion of the
gas by thP liquid. Thus, for example, and in the case of ~;
oxygen, the oxygen absorption rate is increased which is
bene~icial for many applications.
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While the static aerator according to the '527
operates in a satisifactory manner, it has been found that
the oxygenation rate of the liquid can be increased
further by adding gas to the liquid upstream of the
aerator and utilizing two specific techniques. In the
first technique which is typically used for minute or
smaller flows of liquid, a gas supply pipe is positioned
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adjacent the upstream end of the aerator helically shaped
vane and orifices are drilled in the pipe equidistant and
longitudinally along the pipe for the distance of the vane
and are located on opposite sides of the vane. This
allows the gas to be emitted from the orifices in a
uniform manner on both sides of the vane as the liquid
passes by the supply pipe. It has been found that
distributing gas to the liquid on both sides of the vane
from orifices can substantially increase the rate of
oxygenation over tha~ obtained from the simple
introduction of oxygen upstream of the aerator.
The second technique is particularly useful for
larger liquid flows. In the second technique, a venturi
is located upstream from the helical vane of an aerator
and, as the liquid flows through the venturi, a pressure ;
reduction occurs as is well known when the velocity of the
liquid increases. The pressure reduction creates a low ~
pressure or suction area and a supply of oxygen gas is -
provided at the suction area which then enters the liquid.
A ball and spring-loaded check valve is provided to
prevent gas from being emitted by the supply pipe when -~
there is no liquid flow through the conduit.
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2 5 SUMMAXY OF THE INVENTION
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According to one aspect of the invention, there
is provided an apparatus for mixing gas with a liquid
comprising a helical vane twisted about a longitudinal
axis and being positioned in a conduit, said vane having
an upstream end and a downstream end, a gas supply pipe
located adjacent said upstream end of said helical vane
and orifices located in said gas supply pipe on opposite -
sides of said vane ko supply gas into a liquid travelling
through said conduit, said orifices being located on
opposite sides of said end of said vane.
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.. According to a further aspect of the invention, :~
there is provided a valve for inject:ing gas into a liquid
; upstream of the helical vane of an aerator, said valve
comprising a venturi to increase the flow of said liqu.id
and thereby creates a low pressure zone adjacent said
venturi and a gas supply conduit allowing access to said
. valve and said liquid adjacent said venturi.
According to yet a further aspect of the
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invention, there is provided a method of mixing gas and
liquid comprisins passing liquid through a venturi to ~.
create a low pressure zone, exposing a supply of gas to ~ :~
said low pressure zone adjacent said venturi, allowing . ~.
said low pressure zone to extract gas from said gas supply
and passing said gas and liquid mixture through a helical
vane of an aerator. ~ ~;
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
Specific embodiments of the invention will now
be described, by way of example only, with the use of j.
drawings in which~
Figure 1 is an isometric diagrammatic view of
25 the helical vane of a static aerator according to that ..
disclosed in U.S. Patent 4,749,572; -~
Figure 2 is an isometric v.iew similar to that of
Figure 1 but illustrating the gas supply pipe utilized to
supply gas to liquid according to the invention;
Figure 3A illustrates the gas supply pipe and
static aerator oP Figure 2 in plan:
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Figure 3B is an enlarged plan view of the gas ~:
supply pipe and helical vane of the static aerator of
Figure 3A; :
Figure 4A is a side view o~ a gas injection
reactor valve according to a further embodiment of the ::-
invention;
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Figure 4B is a sectional view of the gas -~
10 injection reactor valve of Figure 4A; .
Figure 5 is a waste water treatment system
utilizing the teachings of the present invention; and
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Figure 6 is a view of the reactcr valve
according to the invention located upstream of the
aerator.
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DESCRIPTION OF SP_CIFIC ~MBODIMENT
Referring now to the drawings, a static aerator
is generally illustrated at 10 in Fi.gure 1 and is of the
same type static a~rator as that disclosed in U.S. Patent :~
4l749,527 (Rasmussen) and entitled STATIC AER~TOR. The
static aerator 10 includes a helical vane 11 which curves
about a longitudinal axis 12. As seen in Figure 3A the
vane 11 twists through 360 and as the length of the ;~
static aerator 10 is traversed from upstream to :::
downstream, the angle of curvature of the helical vane 11
increases as seen in Figure l. The upstream end 13 of the
vane ll and the downstream end 14 are elongate and :~
positioned substantially vertical as seen in Figures 1 and
2.
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A gas supply pipe 20 (Figure 2) is connected to
the upstream end 13 o~ the helical vane 11 of the aerator
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lo. The gas supply pipe 20 has a vertical axis 21 which
is parallel with the vertical and elongate upstream end 13
of the helical vane ll. A plurality of orifices 22 are ~ :
positioned in the supply pipe 20. The orifices 22 are
5 located symmetrically on each side of the upstream end 13 :~
of the helical vane 11. As liquid 24 flows through the
conduit 23 as seen in Figures 3A and 3B, the gas, such as
oxygen, is supplied from the supply pipe 20 and enters
into the liquid on both sides of the vertical end 13 of
. 10 the helical vane 11. Thus, gas is distributed into the
liquid 24 from the orifices 22 on both sides of the
vertical elongate end of helical vane 11. Typically, the
diameter of the orifices 22 are approximately 1/64 of an ::
inch. The gas supply pipe 20 has a diameter of ~ :
approximately 1/4 inch. The Figure 3 embodiment is
typically used for smaller or minute liquid flow. ~ ~
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A further embodiment of tha invention is ~
illustrated in Figures 4A and 4B. In this embodiment, the -`:
gas supply pipe 20 illustrated in Figures 2 and 3 i.s
replaced with a gas supply pipe 30. The gas supply pipe
30 is connected to a reactor valve 31 and the reactor
valve 31 is connected to conduit 23 (Figure 3A)
immedia-tely upstream of the end of the helical vane 11 as
illustrated in Figure 6. Liquid 32 flows through the
reactor valve 31 and, before reaching the aerator 10, the
liquid 32 encounters a venturi section generally
illustrated at 33.
The venturi section 33 decreases the diameter of
the inside circumference of the reactor valve 31 thereby
increasing, the velocity of the liquid 32 in the valves
31. A low pressure or suction area adjacent to the outlet
34 of the gas supply pipe 30 is created. The gas supply
pipe 30 further comprises a seal 40, a ball 41 and a
spring 42 which, when there is no flow of liquid in the
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reactor valve 31, is closed thereby preventing the escape
of oxygen from the outlet 34 of the gas supply pipe 30.
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OPERATION
In operation and when liquid 32 flows in ;~;
reactor valve 31, the low pressure created at the outlet ::~
34 of the gas supply pipe 30 will be of a magnitude such
that the ball 41 will move against compression spring 42 ~ ~;
and be removed from its seat on seal 40 thereby allowing
gas such as oxygen to enter into the liquid 32 flowing :~
through the reactor valve 31. When flow is terminated,
the vacuum at outlet 34 will cease, the ball 41 will
return to its seat on seal 40 and the gas will no longer
be emitted from outlet 34.
Referring to Figure 5, a septic tank and tile
field waste system according to the invention is
illustrated at 70 in a typical configuration. The static
aerator 43 has a reactor valve 31 according to the
invention connected upstream of the aerator 43. An
oxygen supply conduit 44 is connected by way of a check
valve 50 and a supply solenoid 51 to a source of oxygen
such as an oxygen bottle 52. A septic tank 53 is located .
underground as is usual and the organic waste within the
septic tank 53 is sub~ect to anaexobic bacterial breakdown
within the septic tank 53. The effluent or waste water
leaves septic tank 53 via outlet 5~ and enters into the
well module 60. As the water level rises in the well
, 30 module 60, the high wate~ level ("HW.~") is reached. A
switch tnot shown~ is activated and turns on pump 61 as
well as solenoid valve 51. Pump 61 pumps the effluent
through a pump discharge pipe 62 and the oxygen supply
conduit 44 provides oxygen to the reactor valve 31 as has
been described in association with the Figure 4A and
Figure 4B embodiment. The oxygenated effluent with the
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oxygen dissolved in the waste water then travels through
the static aerator 43 and is discharged ~rom a discharge
pipe 63 to the tile field 64 ~not shown) with a desired
portion being returned to the well module 60 as is
5 controlled by control valve 72 for recirculation. When `;
the liquid level in module 60 reaches the low water level
("LWL"), the pump 61 and the solenoid valve 51 will cease
operationO In the event of a failure of the switch
activated by the liquid reaching the high water level
("HWL"), an emergency overflow ("EO") is provided which
will allow the effluent or waste water in module 60 to
overf~ow under gravity. A suitable control apparatus is
generally illustrated at 71 and is operable to power the ;~
solenoid 51 and the pump 61 thereby to provide oxygen to ~`~
the reactor valve 31 when effluent is pumped through the
reactor valve 31~
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While specific ~mbodiments of the invention are
illustrated, such embodiments should be taken as examples
of the invention only and not as limiting its scope. Many
modifications will readily occur to those skilled in the
art to which the invention relates. Accordingly, the
invention should be limited only by the scope of the
accompanying claims.
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