| US4042351A | 1977-08-16 | |||
| US2983331A | 1961-05-09 |
C l a i m s
1. A method of separating gas from a liquid where the gas is dispersed in the liquid, c h a r a c t e r i z e d i n that the liquid is mechanically agitated to cause cavitation in the liquid, whereupon at least some of the gas that separates from the liquid during the cavitation is removed by the gas being pumped out of the liquid.
2. A separation device for gas from a liquid where the gas is dispersed in the liquid, and where the liquid flows in a space closed off from the surroundings, c h a r a c t e r i z e d i n that an agitator (1) has been placed in the space (2) , the agitator (1) being arranged to cause cavitation in the liquid, and where a pump-out pipe 8 for gas is connected to the space (2) downstream of the agitator (1) .
3. A separation device in accordance with Claim 2 , c h a r a c t e r i z e d i n that the agitator (1) is constituted by a motor-driven propeller.
4. A separation device in accordance with Claim 2 , c ha r a c t e r i z e d i n that the agitator (1) is constituted by a stationary object.
5. A separation device in accordance with Claim 2, c h a r a c t e r i z e d i n that the space (2) is constituted by a pipe.
6. A separation device in accordance with Claim 5 , c h a r a c t e r i z e d i n that the pump-out pipe (8) leads into the pipe (2) downstream of the agitator (D • o
7. A separation device in accordance with Claim 5 , charac t er i z ed in that the pump-out 'pipe (8) is connected to a gas dome (12), the gas dome (12) communicating with the pipe (2) downstream of the agitator (1) . |
A METHOD AND A DEVICE FOR SEPARATING A GAS FROM A LIQUID
This invention regards a method for separating a gas from a liquid. More particularly, it regards a method to be applied when the gas in question is dispersed in the liquid, the liquid being mechanically agitated to cause cavitation, whereupon at least some of the gas separated from the liquid during the cavitation is removed by the gas being pumped out of the liquid. The invention also includes a device for implementation of the method.
A large number of liquids contain dispersed gases. It is often necessary to reduce the gas content of a liquid before this can be used, stored or discharged into the environment.
As an example, oxygen must be removed from water before the water is injected into a petroleum reservoir. Separation of volatile organic compounds (VOC) from oil is often required before the oil can be transported, and organic compounds must be removed from produced water before the water can be discharged to sea.
Common to many dispersed gases is their tendency to form large bubbles in the liquid upon a reduction in pressure.
In prior art, installations for separating gas from liquids often comprise relatively large and expensive installations.
The object of the invention is to remedy or reduce at least one of the drawbacks of prior art.
The object is achieved in accordance with the invention, by the characteristics given in the description below and in the following claims.
According to the invention, a gas, which is dispersed in a liquid, is separated from the liquid by mechanically agitating the liquid to cause cavitation in the liquid. Then at least some of the gas that separates out from the liquid during the cavitation is removed by the gas being pumped out of the liquid.
Cavitation is characterized by the occurrence of local negative pressure in the liquid. Cavitation can occur in an impeller or a propeller. In the areas of local negative pressure, gas bubbles will form and rise to the surface due to their buoyancy. Cavitation may also occur at stationary objects in the presence of a sufficient pressure drop.
A device according to the invention for separating gases from liquids comprises an agitator located in a space that is closed off from the surroundings, the agitator being arranged to cause cavitation in the liquid. A pump-out pipe for gas is connected to the space downstream of the agitator.
Advantageously the agitator is constituted by a motor-driven propeller, preferably arranged in a pipe. The pipe forms said space.
The pump-out pipe can lead into the pipe, and the inlet is located in a "cavitation bubble" that is formed downstream of the agitator. The term cavitation bubble here refers to an area that comprises a substantial share of gas. The pump-out pipe may also be connected to a gas dome on the pipe. The gas
dome is located downstream of the propeller.
The method and the device according to the invention provide a relatively simple and inexpensive way of efficiently separating dispersed gas from a liquid.
The following describes a non-limiting example of a preferred method and embodiment illustrated in the accompanying drawings, in which:
Fig. 1 is a schematic view of a device according to the invention for separating dispersed gases from a liquid; and;
Fig. 2 is a schematic view of an alternative embodiment of the device.
In the drawings, reference numeral 1 denotes a propeller placed in a pipe 2. The propeller 1 is connected to a motor 4, which is secured to the pipe 2 by a bracket 6.
A pump-out pipe 8 coupled to a pump (not shown) extends through the pipe's 2 wall 10 and leads into the pipe 2 downstream of the propeller 1, preferably in a cavitation bubble 11. Arrows in the drawing indicate directions of flow.
When the propeller 1 is driven by the motor 4, cavitation occurs at the propeller 1, whereby the dispersed gas congregates in large bubbles. The gas bubbles are drawn out through the pump-out pipe 8.
In an alternative embodiment, see Figure 2, the pipe 2 is provided with a gas dome 12 downstream of the propeller 1.
The gas dome 12 has a relatively large opening 14 through the pipe wall 10. Gas, which congregates in large bubbles, may thereby rise to the surface and into the gas dome 12 by virtue of its buoyancy, and then flow out of the dome through
the pump-out pipe 8 .
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