WO1995012452A2

WO1995012452A2 - Gas injection method and apparatus

Info

Publication number: WO1995012452A2
Application number: PCT/CA1994/000595
Authority: WO
Inventors: Erik Hoel
Original assignee: Erik Hoel
Priority date: 1993-11-01
Filing date: 1994-11-01
Publication date: 1995-05-11
Also published as: WO1995012452A3; AU7988194A

Abstract

Method and apparatus for injecting gas into a liquid stream. The inside diameter of a conduit through which the liquid flows is reduced in a venturi section thereby creating a low pressure zone. A gas supply is exposed to the low pressure zone and gas from the gas supply is allowed to enter the liquid so as to mix therewith. The gas and liquid mixture is passed through an aerator to further reduce the size of the gas bubbles and thereby increase the surface area of the gas bubbles exposed to the liquid to enhance the reaction between the gas and the liquid.

Description

GAS INJECTION METHOD AND APPARATUS

INTRODUCTION

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 aerator.

BACKGROUND OF THE INVENTION

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 oxygenation of a liquid such as sewage effluent to enhance sewage breakdown. The method and apparatus disclosed in the '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 the liquid. Thus, for example, and in the case of oxygen, the oxygen absorption rate is increased which is beneficial for many applications.

While the static aerator according to the '527 patent operates in a satisfactory 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 by 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 adjacent the upstream end of the helically shaped aerator 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 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 that 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 the aerator and, as the liquid flows through the venturi, a pressure reduction occurs as is well known when liquid velocity increases. The pressure reduction creates a low pressure or suction area and a supply of oxygen gas is provided at the suction area which 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.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided 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 to supply gas into a liquid travelling through said conduit. According to a further aspect of the invention, there is provided a valve for injecting gas into a liquid upstream of the helical vane of an aerator, said valve comprising a venturi to increase the flow of said liquid and thereby create 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 invention, there is provided a method of mixing gas and liquid comprising 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.

According to yet a further aspect of the invention, there is provided apparatus for removing sulphur and other compounds from combustion products comprising a smoke stack, a source of oxygenated liquid, means to convey said oxygenated liquid to injector nozzles which emit said liquid into said smoke and means to collect the byproducts removed from said smoke by the injection of said oxygenated liquid into said smoke.

According to yet a further aspect of the invention, there is provided a method to remove sulphur and other compounds from combustion products comprising conveying smoke from said combustion products through a smoke stack, injecting oxygenated liquid into said smoke stack and collecting the byproducts removed from said smoke by said oxygenated liquid. 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 drawings in which:

Figure 1 is an isometric diagrammatic view of the helical vane of a static aerator according to that aerator disclosed in U.S. Patent 4,749,572;

Figure 2 is an isometric view similar to that of Figure 1 but illustrating a gas supply pipe utilized to supply gas to liquid according to the invention;

Figure 3A illustrates the gas supply pipe and static aerator of Figure 2 in plan;

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 of a venturi gas injection reactor valve according to a further embodiment of the invention;

Figure 4B is a sectional view of the venturi gas injection valve of Figure 4A;

Figure 5 is a waste water treatment system utilizing the teachings of the present invention;

Figure 6 is a view of the venturi gas injection valve according to the invention located upstream of the aerator; Figure 7A is a diagrammatic view of experimental apparatus used as an acid rain interceptor; and

Figure 7B is a diagrammatic view of a further embodiment of an experimental embodiment of an acid rain interceptor.

DESCRIPTION OF SPECIFIC EMBODIMENT

Referring now to the drawings, a static aerator is generally illustrated at 10 in Figure 1 and is of the same type static aerator as that disclosed in U.S. Patent 4,749,527 (Rasmussen) and entitled STATIC AERATOR. 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 1. The upstream end 13 of the vane 11 and the downstream end 14 are elongate and positioned substantially vertical as seen in Figures 1 and 2.

A gas supply pipe 20 (Figure 2) is connected to the upstream end 13 of the helical vane 11 of the aerator 10. 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 11. A plurality of orifices 22 are positioned in the supply pipe 20. The orifices 22 are 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 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.

A further embodiment of the invention is illustrated in Figures 4A and 4B. In this embodiment, the gas supply pipe 20 illustrated in Figures 2 and 3 is replaced with a gas supply pipe 30. The gas supply pipe 30 is connected to an injector valve 31 and the injector valve 31 is connected to conduit 23 (Figure 3A) immediately upstream of the end of the helical vane 11 as illustrated in Figure 6. Liquid 32 flows through the injector 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 venturi injector valve 31 thereby increasing the velocity of the liquid 32 in the valve 31. A low pressure or suction area adjacent to the outlet 34 of the gas supply pipe 30 is thus 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 venturi injector valve 31, is closed thereby preventing the escape of oxygen from the outlet 34 of the gas supply pipe 30.

OPERATION

In operation and when liquid 32 flows in venturi injector 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 injector 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 gas supply pipe 20 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 subject to anaerobic bacterial breakdown within the septic tank 53. The effluent or waste water leaves septic tank 53 via outlet 54 and enters into the well module 60. As the water level rises in the well module 60, the high water level ("HWL") is reached. A switch (not 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 gas supply pipe 20 of the aerator 43. The oxygenated effluent is discharged from a discharge pipe 63 to the tile field 64 (not shown) with a desired portion being returned to the well module 60 as is 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 operation. 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 overflow 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 43 when effluent is pumped through the reactor valve 43.

Reference is now made to Figures 7A and 7B which illustrate two embodiments of an acid rain interceptor ("ARI") utilizing the teachings according to the present invention in an experimental or prototype apparatus. A fire box 73 creates combustion products which emanate, in the normal course, from smoke stack 74. In order to determine the efficacy of the process, wood was burned in the fire box 73 and heated until it became red hot and had glowing embers. Sulphur powder was then placed into the fire box 73 in an envelope and the fire box door through which the sulphur powder was inserted was closed.

The smoke emanating from the smoke stack 74 became yellow in colour with a strong odour of sulphur permeating the air nearby. Oxygen rich water created according to the teachings of the present invention was held in cylindrical tank 80 and a compressed air bottle 81 was connected to the cylindrical tank 80. The cylindrical air bottle 81 was opened so that the compressed air was introduced into the cylindrical tank 80 thereby forcing the oxygen rich water having an enrichment factor of 50 parts per million 0₂ through pipe 82 to the interior of the smoke stack 74 where the oxygenated water was emitted from twin ejector nozzles 83. Thus, a fine mist of oxygenated water was injected downwardly into the smoke stack 74 from the nozzles 83. Upon the ejection of the oxygenated water in mist form, the smoke emanating from the chimney changed colour to a whitish form that had little or no sulphur smell. The smoke dissipated within a few feet from the output of the smoke stack 74.

Upon shutting down the system, the drain 84 was opened and a mixture of soot grit and sulphur dioxide was recovered thereby providing evidence that removal of sulphur compounds about to be emitted from the smokestack can be controlled through the use of the oxygenated water or oxygenated liquid.

A further embodiment utilizing the same teachings can occur outside the chimney 74 as illustrated in Figure 7B. In this event, a deflector 90 is provided which is used to deflect the smoke emanating from the smoke stack 74. Oxygenated water is emitted from the nozzles 83. These nozzles provided the same benefits as illustrated in connection with the Figure 7A embodiment. A deflector 91 with a drain 92 is provided which acts to collect the products similar to the function of the drain 84 in the Figure 7A embodiment. Piping (not shown) can be connected to the drain 92 of deflector 91 in order to continuously remove the byproducts.

Besides the removal of sulphur by oxygen, other impurities may be removed by the addition of different gases to the liquid as may be desirable. Likewise, an accelerator or accelerators may also be used in combination with the oxygenated or gas permeated liquid which would be useful in enhancing the rate and quantity of impurity removed.

While specific embodiments of the invention have been described, such embodiments should be taken as illustrative 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 and, accordingly, the invention should be limited only by the scope of the accompanying claims.

Claims

THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. 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 to supply gas into a liquid travelling through said conduit.

2. Apparatus as in claim 1 wherein said end of said helical vane is elongate and said gas supply pipe and said elongate end are substantially vertical, said orifices being spaced vertically along said gas supply pipe.

3. Apparatus as in claim 2 wherein said gas supply pipe supplies oxygen to said liquid.

4. A valve for injecting gas into a liquid upstream of the helical vane of an aerator, said valve comprising a venturi to increase the flow of said liquid and thereby create a low pressure zone adjacent said venturi and a gas supply conduit allowing access to said valve and said liquid adjacent said venturi.

5. A valve as in claim 4 wherein said gas supply conduit supplies oxygen to said valve and liquid.

6. A valve as in claim 5 and further including a check valve operably associated with said gas supply conduit.

7. A valve as in claim 6 wherein said check valve comprises a seal and a spring loaded ball biased to seat on said seal.

8. A method of mixing gas and liquid comprising 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.

9. Apparatus for removing sulphur and other compounds from combustion products comprising a smoke stack, a source of oxygenated liquid, means to convey said oxygenated liquid to injector nozzles which emit said liquid into said smoke and means to collect the byproducts removed from said smoke by the injection of said oxygenated liquid into said smoke.

10. Apparatus as in claim 10 wherein said injector nozzles are located inside said smoke stack and said collection means is a drain located below said injector nozzles in the lower portion of said smoke stack.

11. Apparatus as in claim 10 wherein said injector nozzles and said collection means are mounted outside said smoke stack.

12. A method to remove sulphur and other compounds from combustion products comprising conveying smoke from said combustion products through a stack, injecting oxygenated liquid into said stack and collecting the byproducts removed from said smoke by said oxygenated liquid.

13. A method as in claim 12 wherein said oxygenated liquid is injected and said byproducts are removed outside said stack.

14. A method as in claim 12 or 13 wherein said oxygenated liquid is oxygenated water.