GB2084051A - Process for rapidly and continuously defoaming liquid material and the apparatus thereof - Google Patents

Abstract

A viscous liquid is defoamed under vacuum in a rotating vessel 7 provided with a partition 10 having holes 9 around its periphery. The liquid is fed through a pipe 1, passes through the holes 9 and is discharged through a fixed pipe 8. Gas is withdrawn through a pipe 6. The vessel 7 is located in a cooling chamber 19 to which water is supplied through an inlet 17. <IMAGE>

Description

SPECIFICATION Process for rapidly and continuously defoaming liquid material and the apparatus thereof The present invention provides a defoaming process for continuous operation and an apparatus characte rized in a compact unit, a high-defoaming rate and an automatic feed and discharge. Particularly this invention provides outstanding effects in defoaming the high viscous fluids which contains bubbles.

The conventional methods for defoaming liquid material can be fairly divided into two types; The first method isto subject the liquid material to form a thin-film viscous flow along the surface of a slanting plate and then flowing downward in the defoaming cylinder under a very low pressure (Shown in Figure 1), said slanting plate (101 ) is set to increase the distance of flow path of fluid which enables the liquid material to flow stagnantly in a form of a thin film and bubbles therein to expand and break off under a lower pressure so that the objective of the present invention can be achieved.

However, there are some disadvantages in such a defoaming method, one of the disadvantages is that they need a very bullcy apparatus and also the flow rate of the liquid is very slow. Moreover, a thick liquid layer could easily be created due to an excess feed which would results in an undesirable effect in the the defoaming treatment, another disadvantage is that the machine operations such as air suction and the like must be stopped to outlet the material when a considerable amount of the defoamed material has been accumulated atthe bottom of the cylinder, this also causes inconvenience in the continuous opera tion.

The second method makes use of a stirrer (Shown in Figure 2). Material is charged in a closed vessel and stirred with afan-shaped stirr (102) under low pressure, which causes bubbles expanding and raising up to the surface of the liquid and flee away and therefore the purpose of defoaming is achieved.

However, there are some disadvantages in such a method: the volume of said vessel is too large, the defoaming rate is too slow and the defoaming effect, usually, is not satisfactory; Particularly, the defoam ing effect can not be completed at the defiladed space where the stirring fan does not reach. Furth ermore, bubbles may never break off even they have expanded when the fluids with high viscosity is stirred at the upper portion of said fan because the surface tension of the bubbles is sufficient to compete with the pressure difference between the inner and outer pressure of bubbles, this causes a soap foam like materials floating over the upper layer of the liquid. Accordingly, this method cannot provide a satisfactorydefoaming results for a high viscous fluids.

The primary concept of the present invention resides in an easier defoaming method characterized in that: feed is charged into the central portion of a high-rapid rotating cylindrical vessel under a near vacuum pressure that the fluids may creep from the central portion towards the outer margin of the rotary vessel in a sprial way (refer to Figure 3), and a rotating effect along with the thin fluid flow that cause bubbles expanding under low pressure and rolling in the thin film spiral flow of the creeping fluid. Therefore, bubbles can be separated from the liquid material gradually. Since heavy liquid flows towards the outer margin of the vessel, bubbles expanding underthe near vacuum (or low) pressure will be more easily to be separated from the liquid material.

The distribution of the liquid material in the rotating vessel is shown in Figure 4. Pressure head at the vessel margin is estimated according to fluid dynamics: P1 - = pr2so2/2, wherein P1 is the pressure at r distance (refer to Figure 5) from the rotating center (i.e. the center of the vessel according to the present invention).

PO is the pressure at the center region, p is the density of liquid, r is the radius of the vessel, o is the angular velocity.

In the above formula the factor of pressure pgh, formed from different heightofliquid material near the margin region of the defoaming room (refer to 21 in Figure 21 in Figure 6) is not estimated since the defoaming room of the present invention is not high prefer to h in Figure 5) and the density of liquid material is usually close to that of water, the contribution of the pressure pgh (about 15cm water column pressure) can be neglected as compared with the pressure head produced from the rotation of the vessel (about 3 atm) the details relating to the pressure head is described here in:: For an embodiment of the present invention wherein h=17.5 cm, p=1g/cm3, the rotation speed of vessel=1,200 rpm, the pressure head P1-P,=2.5kg/ cm2 and PO S 20mm/hg (due to the air suction in the defoaming chamber),the liquid pressure at the vessel margin is about 2.3-25kg/cm2 which is 1.3 to 1.5 atm pressure higher than that of the outer surrounding atmosphere. This pressure difference drives liquid material flowing through the small holes at the circumference of a partition board (bottom board of defoaming chamber) into a lower chambertherebelow. A S-shaped curve pipe is connected to a central discharge pipe at the vessel bottom to render to an automatic discharge.

The feed material can be transported through a feed pipe extended from the central portion of the vessel into a defoaming chamber and is driven by the atmospheric pressure outside the cylinder when the low pressure in the defoaming chamber is created due to the sucking of an vacuum pump. An additional control valve is set at the feed pipe to control the feeding rate.

The Figures described hereinafter are used to illustrate the apparatus of the present invention: Figure 1 and 2 are schematic diagrams of the conventional types of the defoaming apparatus, Figure 3 is a schematic diagram according to the present invention showing a spiral flow path of the liquid material after being charged into the central portion of the vessel, Figure 4 is a schematic diagram showing the distribution of the liquid material in the roatry vessel, Figure 5 illustrates each position of the symbol r, h, p1 and PO in the defoaming chamber, Figure 6 is a cross-sectional view of the defoaming apparatus according to an embodiment of the invention, Figure 7 is a perspective view of the main portion of the defoaming unit according to the present invention, Figure 8 is an outer view of the S-shaped curve pipe according to the present invention.

Figure 9 and 10 are the schematic diagram illustrating the circumference of the partition board of the cylindrical vessel according to the present invention.

Figure 1 7 is a cross-sectional view of the defoaming apparatus according to another embodiment of the invention.

Referring to Figure 3, the symbol I shows the direction of feed, R shows the rotation direction of cylindrical vessel and P the flow path of liquid material along the partition board of the cylindrical vessel. Referring to Figure 4, 1 shows the direction of feed and 0 shows the direction of discharge, numeral 7 and 8 represent cylindrical vessel and S-shaped curve pipe respectively, and 10 is the partition board between upper and lower chambers of the cylindrical vessel 7. 15 is the discharge pipe and 100 represents liquid materials. Obviously, Figure 3 and 4 readily show the movement and distribution of the liquid material from feeding to discharging.

Referring to Figure 6, liquid material is fed into the feed pipe (1) through a feed-control valve (22), and absorbed into the defoaming chamber (21) of cylindrical vessel (7) and then passed through the central portion of partition board (10). Since cylindrical vessel (7), upper sleeve (12) and lower sleeve (11) are connected together as a whole body by screws, and lower sleeve (11) is fixed on a belt pulley (14) with a pin (13) wherein said belt pulley (14) is connected with a motor, all the cylindrical vessel (7), lower sleeve (11), upper sleeve (12), pin (13) and belt pulley (14) are in rotation while the operation are proceeding.A S-shaped curve pipe (8) is connected with dis#charge pipe (15) and are kept fixed without rotation. Afterthe materials crept towards the outer margin of defoaming chamber (21) due to the rotation of cylindrical vessel (7), the pressure head of material at the position close to said margin turned to be about 2.3 to 2.5 kg1cm2 which drived the material passing through small holes (9) at the margin of partition board (10) into margin region of the lower chamber of cylindrical vessel (7) and then being discharged through said S-shaped curve pipe (8) which have openings under said small holes (9) and are connected with outside space (pressure: 1 atm). Finally, material passed the small holes (9) is automatically discharged due to the pressure difference between the pressures of inside and outside vessel.A check valve (23) is also fixed at the opening of discharge pipe (15). The check valve (23) is in a close state at the beginning of the operation, thus, enabling the pressure within the defoaming chamber to be smoothly sucked to a near vacuum pressure so that the liquid material can be absorbed into the defoaming chamber automatically. While the air is sucked, the air flow path is through the pipe (6), a vacuum pump and a vacuum pressure gauge (20), which enables air to be sucked from the defoaming chamber upwards through the small space between feed pipe (1) and upper sleeve (12) and finally into pipe 6.

The perspective view and the operating embodiment of the cylindrical vessel (7), partition board (10), small holes (9), S-shaped curve pipe (8), upper sleeve (12), lower sleeve (11) and discharge pipe (15) are illustrated in Figure 7,8,9 and 10. As shown in Figure 6 feed pipe (1) is fixed together with shaft bearing set (2), upper cover (5) of outer cylinder (26), outer cylinder (26) and machine body stand (24), wherein said machine body stand (24) is connected by a fixed bar (25) to discharge pipe (15) in order to fix the discharge pipe. The clearances between upper, lower sleeves (12) (11) and their respective shaft bearing set (2), and the clearance between lower sleeve (11) and discharge pipe (15) are properly sealed with bearings (3) and seals (4).

As a result of the rotation of material in the cylindrical vessel (7), friction heat is caused due to the viscous effect of the fluid flow. In order to protect the machine body and prevent the temperature increase in the discharged material, an outer cylinder (26) is fixed outside the vessel (7) to form a cooling chamber (19) in which cooling water (normally city water will work) is charged from an inlet (17) into the lower portion of the cooling chamber (19).

Acurve piece (18) is fixed below the cooling chamber to force cooling water feeding towards the rotation center. Cooling water is charged into the outer cylinder (26) by centrifugation effects due to the rotation of cylindrical vessel (7), then discharged through a discharge pipe at the outlet (16) at the upper portion of the outer cylinder (26).

The above-mentioned embodiment can be carried out by utilizing a cylindrical vessel, for example, having a diameter of 350mm of the defoaming chamber (21) with a height of 40mm, and having a lower chamber with a height of 40mm applying to defoam a viscous chemical material of DFM (about 1.2 x 104cps). From our test run, the defoaming speed was 5 liters/min. for a conventional apparatus having a capacity of 50 liters, it takes 2.5 hr (i.e. 0.133 1/min) to defoam 20 1 materials by means of stirring.

Obviously, the present invention provides an outstanding defoaming ability (30 times of the conventional way).

Furthermore, the present invention provides another outstanding advantage that the operation of the present apparatus needs unnecessarily to be raised up to a considerable height above the ground, because the rotation of cylindrical vessel provides a pressure head to the liquid materials at the maggin region so as to discharge materials automatically and rapidly while the conventional apparatus must be raised up 30 meters above the ground to let the materials flow downwards by gravity force.

Referring to Figure 11, another embodiment of the present invention is illustrated hereinafter: The material defoamed is passed through a funnel-shaped cylinder (36) below the cylindrical vessel (35) to the discharge pipe (37). However, this defoaming apparatus must be raised up to a height of 10 meters above the ground so as to maintain a continuous operation for the automatic discharging.

If the height is lower than 10 meters, a pump must be employed at the discharge outlet so that a continuous defoaming process can be obtained. The advantages of this embodiment are that the Sshaped curve pipe lower sleeve, and their related parts can be omitted and that friction heat caused by viscosity effects between the rotating liquid material and the fixed S-shaped curve pipe can be avoided.

Accordingly, the cooling system could also be eliminated in the apparatus of this embodiment. In order to match with the operation of the funnelshaped cylinder (36), the bottom of the cylindrical vessel (35) is designed to be hollow except for the portion near its margin. In addition a motor (31), motor gear (32) and speed-reducing gears (33) are provided for the apparatus in this embodiment so as to drive the rotation of outer sleeve (38) and disk vessel (35), instead of belt and belt pulley driving means.

Claims (11)

1. A process for defoaming bubbles-containing liquid which is characterized in that the bubbles are separated from liquid in a rotating vessel at a low (or very low) air pressure. The defoaming process is achieved by employing the effects of centrifiguration and the long flow distance of thin viscous creeping flow by creating a spiral flow path in a compact space due to the rotation of the liquid and the vessel at a low (or very low, close to vacuum) air pressure.

2. The process according to claim 1, in which a continuous operation is achieved by an automatic feed and discharge, the automatic feed is driven by a pressure difference between the inside and outside of the near vacuumed defoaming chamber, and the automatic discharge is caused by a pressure head produced by a rotating centrifugation capable of discharging the defoamed liquid outside of the rotating vessel.

3. The process according to claim 1, wherein a cylindrical vessel is divided into two chambers, (the upper one is a defoaming chamber) with a partition board having a plurality of small holes at the circumference thereof.

4. The process according to claim 1 wherein the upper and lower portions of said cylindrical vessel are connected with hollow cylindrical sleeves respectively, the two sleeves are supported on the upper machine body stand and the fixed discharge pipe of the lower machine body stand with shaft bearings to make the cylindrical vessel rotatable.

5. The process according to claim 1, wherein said cylindrical vessel comprises a feed pipe set within said sleeve at the upper portion thereof, said feed pipe is fixed on the machine body with additional fixing pieces so that a small clearance space between said feed pipe and said sleeve at the upper portion of said cylindrical vessel is formed to connect with the inlet of an air-suction pipe.

6. The process according to claims 1,2 and 3, wherein the cylindrical vessel comprises a couple of S-shaped curve pipes in the lower chamber, the openings of the curve pipes are closed to the small holes at the circumference of said partition board and is connected with the discharge pipe at the center of the lower machine body, the lower portion of said discharge pipe is connected with the machine body and is supported on the sleeve at the lower portion of said cylindrical vessel with shaft bearings.

7. The process according to claim 3, wherein said cylindrical vessel is surrounded by a outer cylinder of a larger radius to form a cooling chamber between the space of said outer cylinder and cylindrical vessel.

8. The process according to claims 1, 2 and 3 wherein said cylindrical vessel can be fixed with a funnel shaped cylinder in connection with the discharge pipe, the equipping of an additional discharge pump for the discharging depends on the height of the machine apparatus above the ground level.

9. A process for defoaming bubble-containing liquid substantially as described herein with reference to the drawings.

10. Apparatus for performing the method claimed in any one of the preceding claims.

11. Apparatus for defoaming bubble-containing liquid substantially as described herein with reference to the drawings.