GB2180474A

GB2180474A - Device for removing bubbles

Info

Publication number: GB2180474A
Application number: GB08617481A
Authority: GB
Inventors: Ryushi Suzuki; Joji Yamaga; Takeo Nakazawa; Jiro Higase
Original assignee: OMNIPACK KK; IHI Corp
Current assignee: OMNIPACK KK; IHI Corp
Priority date: 1985-09-21
Filing date: 1986-07-17
Publication date: 1987-04-01
Also published as: KR910001892B1; DE3620999A1; JPH0334244Y2; KR870002858A; JPS6256105U; GB2180474B; GB8617481D0

Abstract

A device for removing bubbles from a liquid comprises a plurality of elongate, cylindrical bubble-collection bodies 2. One end of each body has one or more tangential inlet apertures 8 and a liquid inlet space 5 is defined around the said one end of the bodies. The one end of the bodies is closed by a cover 4 in which a plurality of gas outlet openings 11 is formed each communicating with a respective bubble-collection space in a body 2 and with a common gas outlet space 10. The other ends of the bodies communicate with a common liquid outlet space 9 and flow resistance means 16 downstream of the bodies induces a back pressure greater than 0.05 kgf/cm<2> in the liquid flowing through the device. <IMAGE>

Description

SPECIFICATION Device for removing bubbles The present invention relates to a device for removing bubbles from liquids, such as paint, coating liquids, varnish, enamel, ink, adhesive agents, liquid food stuff such as molasses, slurry, medical fluids, liquid chemical products, cooling water, washing liquids, bleaching agents, waste liquids, sewage, liquids used in air conditioning systems, sponge, emulsions, latex, lubricating oils and mineral oils, such as the working oils used in hydraulic systems. The invention is particularly concerned with the removal of bubbles entrained in large volumes of liquid flowing at high speed.

Bubbles entrained in various liquids must commonly be removed therefrom because they can variously cause damages to machinery, erosion due to aeration and cavitation, noise, degradation of the finished products and non-painted or non-coated zones when painting or coating.

Figure 4 is a diagrammatic side sectional elevation of a conventional device for removing bubbles. A cylindrical vessel a has end covers b and c and a tangential inlet e formed in the cylindrical wall of the vessel a through which a liquid is supplied from a pump d into the cylindrical vessel. A liquid outletfisformed at the centre of the upper cover band a gas drain opening g is formed at the centre of the bottom cover c. The liquid outlet f communicates via a line h with a liquid tank i and the gas drain opening g is connected to a gas drain pipe j including a valve k.

In this known device, a liquid with bubbles entrained therein is introduced into the cylindrical vessel a by the pump d at a predetermined flow rate through the tangential inlet e. The liquid flow pattern within the vessel is generally helical, flowing along the inner surface of the cylindrical vessel. Due to centrifugal force, the helical liquid flow becomes an axial flow with the highest flow rate in the vicinity of the inlet e and whose flow rate decreases in the downstream direction. The liquid flows out of the outletf and the bubbles collect along the axis of the cylindrical vessel due to the centrifugal force. As a result, the pressure distribution along the axis of the cylindrical vessel is such that the pressure is lowest in the vicinity of the inlet e, increases as the liquid flows downstream to reach a maximum value and then drops.Because of this pressure distribution, the bubbles are collected along the axis of the cylindrical vessel in the vicinity of the inlet e so that an axial gas column is formed. The bubbles are discharged from the cylindrical vessel a through the gas drain opening g.

The device shown in Figure 4 must have a cylindrical vessel with a relatively small diameter in order to fully achieve its intended function. This means that the device can only handle a relatively small volume of liquid flowing at a relatively low flow rate.

The need has recently arisen to remove bubbles from a liquid flowing at a high flow rate through a pipe line. When the device shown in Figure 4 is used for this purpose, the inflow velocity and inflow pressure of the liquid must be increased. However, such high velocity and high pressure are in opposition to the desiderata that the discharge pressure of the pump d is as low as possible and that the liquid is charged into the cylindrical vessel in such a manner that the resolution of the bubbles into the liquid, the compression of the bubbles, cavitation and erosion resulting from cavitation are avoided.

It is an object of the present invention to provide a device for removing bubbles entrained in a large amount of liquid flowing at a high flow rate without increasing the inflow pressure of the liquid flowing into the device.

According to the present invention, a device removing bubbles from a liquid comprises a plurality of bubble-collection bodies defining elongate, circular section bubble-collection spaces extending parallel to one another, one end of each body having at least one tangential liquid inlet aperture for the tangential introduction of a liquid, a liquid inlet space being defined around the said one end of the bodies, a cover closing the said one end of the bodies, a plurality of gas-outlet openings being formed in the cover and communicating with a respective bubble-collection space, a liquid outlet space with which the other ends of the bodies communicate, and flow resistance means downstream of the bodies for inducing a back pressure in a liquid flowing through the device.

When a liquid flows through a tangential liquid inlet into one end of each bubble-collection body, fine bubbles are caused to move towards the axis of the body due to the centrifugal force produced by the circular motion. As a result of the back pressure produced at the other end of each body, the collected bubbles can be readily discharged through a gas discharge port provided at the said one end.

In one embodiment, the liquid inlet space surrounds substantially the entire periphery of all the bubble-collection bodies and in an alternative embodiment, surrounds only the said one end of the bubble-collection bodies.

The invention relates also to such a device when in use in the removal of bubbles from a liquid, the device being so dimensioned and the flow rate being such that the back pressure induced in the liquid by the flow resistance means is greater than 0.05 kgf/cm2.

Further features and advantages of the present invention will be apparent from the following description of two preferred embodiments which is given by way of example with reference to Figures 1 to 3 of the accompanying diagrammatic drawings, in which:~ Figure 1 is a vertical sectional view of a first embodiment of the present invention; Figure 2 is a horizontal sectional view in the direction of the arrow II in Figure 1; and Figure 3 is a vertical sectional view of the second embodiment of the present invention.

Referring first to Figures 1 and 2, the bubble separator includes a plurality, in this case four, of cylindrical bodies 2, each of which defines an internal cylindrical space and which are disposed in parallel with one another within a cylindrical main body 1 such that their axes are equidistant from the axis of the body 1. The interior of the main body 1 is traversed by an upper partition plate or cover 3 and a lower partition plate or cover 4. The upper ends 1 of the cylindrical bodies 2 are open and extend through and slightly beyond the upper cover 3 whilst their lower ends terminate at the lower cover 4. The interior of the main body 1 outside the cylindrical bodies 2 between the upper and lower covers 3 and 4 constitutes an enclosed inlet space 5.

The space 5 communicates with an inlet pipe 7 through which liquid may be charged into the main body 1 by a liquid supply pump 6. A pressure gauge 19 is connected to the inlet pipe 7. The lower end of each cylindrical body 2 has one or more, and in this case two, tangential liquid inlets 8, whereby the liquid introduced into the inlet space 5 flows into the cylindrical bodies 2. In each body 2, the liquid supplied through the tangential inlets 8 adopts a helical flow pattern and flows out of the open upper ends of the bodies 2 into an inlet space 9 defined at the upper portion of the main body 1 above the upper cover 3.

A gas outlet space 10 is defined at the lower portion of the main body 1 belowthe bottom cover4 and a respective gas outlet opening 11 extends through the bottom cover4 into each cylindrical body 2 and connects the latter axially with the gas outlet space 10 so that bubbles which accumulate along the axis of each cylindrical body 2 due to the helical flow therein are discharged through the gas outlet openings 11 into the gas outlet space 10. A gas discharge port 12 communicating with the gas outlet space 10 is formed on the main body 1 and is connected to a gas discharge pipe 13 including a gas drain valve 14. The upper end of the main body 1 is provided with an uppermost ortop cover 15 in which there is a central aperture 16 which is connected to a pipe line 17 having a small cross section and/or a throttle valve 18.The line 17 or the valve 18 are so dimensioned that, in use, a back pressure higher than 0.05 kgf/cm2 is produced across it which ensures a reliable discharge of the bubbles collected along the axis of each of the cylindrical bodies 2 into the gas outlet space 10 through the openings 11.

In each of the cylindrical bodies 2, the liquid flow changes from helical to axial in the downstream direction. Therefore the pressure distribution along the axis of each body 2 is such that the pressure is lowest in the vicinity of the tangential liquid inlets 8, increases downstream (upwardly in Figure 1 ) to reach a maximum value at a certain point and then decreases. Because of this pressure distribution, the bubbles entrained in the liquid collect along the axis of each of the bodies 2 principally in the vicinity of the tangential inlets 8 so that a gas column is formed along the axis of each of the bodies 2.

In operation, a large amount of liquid is supplied by the pump 6 through the inlet pipe line 7 into the inlet space 5 defined by the main body 1. The liquid flows through the tangential liquid inlets 8 into the cylindrical bodies 2 whereby a helical liquid flow is produced in each of the bodies 2 and the bubbles are collected along the axes of the bodies 2 due to the centrifugal force induced by the helical flow. Due to the pressure distribution described above along the axis of the cylindrical body 2, the bubbles entrained in the liquid are collected along the axis of the bodies 2 between the vicinity of the tangential liquid inlets 8 and a point at which the pressure becomes a maximum. The liquid which is now free from bubbles flows downstream through flow resistance means such as the orifice 16, the smalldiameter outlet pipe line 17 and/or the throttle valve 18.

As described above, due to the centrifugal force resulting from the helical flow, a negative pressure is produced along the axis of the cylindrical bodies 2 in the vicinity of the tangential liquid inlets 8.

However, if there is no liquid load at the downstream side of the bodies 2, the collected bubbles cannot be discharged through the gas outlet openings 11 into the gas outlet space 10. The reason for this is that if the back pressure at the downstream side is zero, the pressure along the axis of the bodies 2 in the vicinity of the tangential liquid inlets 8, which varies in dependence on various conditions such as the inflow velocity and the internal diameter of the bodies 2, cannot force the collected bubbles out into the gas outlet space 10.

According to the present invention, a flow resistance means such as the orifice 16, the throttle valve 18 and/or the small-diameter outlet pipe line 17 are disposed downstream of the outlet space 9 of the main body 1 so that a back pressure higher than 0.05 kgf/cm2 is produced across it and consequently the collected bubbles are discharged through the gas outlet openings 11 into the gas outlet space 20.

Extensive studies and experiments conducted by the inventors show that the back pressure must be higher than 0.05 kgf/cm2 regardless of the viscosity of the liquid, the size of the bubbles and the dimensions of the cylindrical bodies 2. This back pressure may be monitored with the pressure gauge 19. The back-pressure may be regarded as the difference between the readings of the gauge 19 when the flow resistance means is inoperative or not present and when it is operative or present.

The bubbles discharged into the gas outlet space 10 pass through the gas discharge port 12 and then the gas discharge pipe line 13.

In the first embodiment described above, the cylindrical bodies 2 are wholly accommodated in the cylindrical main body 1 and the inlet space 5 extends around substantially the entire peripheral surface of the cylindrical bodies 2. However, if it is to be expected that viscous materials may become attached to the outer periphery of the cylindrical bodies 2 and thereby adversely affect the operation of the bubble removing device, contact of the outer peripheries of the cylindrical bodies 2 with the liquid should be minimised. This is achieved in the embodiment of Figure 3 in which the liquid inlet space 5 is defined around the bodies 2 only in the vicinity of the tangential liquid inlets 8 of the cylindrical bodies 2.Thus, the major proportion of the outer periphery of the cylindrical bodies 2 is exposed to the atmosphere and the adhesion of viscous materials to the outer periphery of the cylindrical bodies 2 can be reduced to a minimum.

In addition, the upper and bottom covers 3 and 4 are detachably connected to the other components defining the outlet space 9 and the inlet space 5, respectively, so that the liquid outlet space 9, the gas outlet space 10 and the cylindrical bodies 2 can be easily cleaned. The remaining components are substantially similar to those of the first embodiment described above.

The bodies 2 have been described as being of constant diameter along the whole length thereof, but it will be understood that conical bodies diverging upwardly (that is, in the downstream direction) may be used. In addition, flow resistance means may be disposed downstream of each of the cylindrical bodies 2. Moreover, the diameters of the cylindrical bodies 2 may differ.

In the construction of the present invention, the bubbles entrained in a large amount of liquid flowing at a high flow rate can be removed as easily as the bubbles entrained in a small amount of liquid flowing at a low flow rate. Moreover, the bubbles can be removed without increasing the pressure of the liquid flowing into the device and the collected bubbles can be positively discharged from the device so that high-quality products free from bubbles can be obtained.

Claims

1. A device for removing bubbles from a liquid comprising a plurality of bubble-collection bodies defining elongate, circular section bubble-collection spaces extending parallel to one another, one end of each body having at least one tangential liquid inlet aperture for the tangential introduction of a liquid, a liquid inlet space being defined around the said one end of the bodies, a cover closing the said one end of the bodies, a plurality of gas-outlet openings being formed in the cover and communicating with a respective bubble-collection space, a liquid outlet space with which the other ends of the bodies communicate and flow resistance means downstream of the bodies for inducing a back pressure in a liquid flowing through the device.

2. A device as claimed in Claim 1 in which the liquid inlet space surrounds substantially the entire outer periphery of all the bubble-collection bodies.

3. A device as claimed in Claim 1 in which the liquid inlet space surrounds only the said one end of the bubble-collection bodies.

4. A device for removing bubbles from a liquid substantially as specifically herein described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.

5. A device as claimed in any one of the preceding claims in use in the removal of bubbles from a liquid, the device being so dimensioned and the flow rate being such that the back-pressure induced in the liquid by the flow resistance means is greater than 0.05 kgf/cm2.