ES2212896B1 - PROCEDURE AND ULTRASONIC SYSTEM OF DEFROSTING THROUGH EMISSORESCON VIBRANT SCALE PLATE. - Google Patents

Abstract

Ultrasonic defoaming procedure and system by means of emitters with stepped vibrating plate. The object of this patent application is an ultrasonic device that allows to eliminate foams and control their growth in large containers. The device uses sonic and / or ultrasonic emitters of the stepped vibrating plate type, special to radiate high acoustic intensities in gases, which, being freely suspended on a rotating support with controlled variable rotation, generate in their movement by action of the centrifugal force a complex path of the emitted acoustic beams that allows sweeping the surface on which the foam is formed. Due to the high acoustic intensity (> 170 dB ref. 2.10 {sup, -4} {mi} bar), a large part of the foam bubbles break almost instantaneously to the passage of the ultrasonic beam.

Description

Ultrasonic procedure and system of defoaming by emitters with stepped vibrating plate.

Object

The object of this patent application is a ultrasonic device that allows to eliminate foams and control their Growth in large containers. The device uses transmitters sonic and / or ultrasonic of the step vibrating plate type, special to radiate high acoustic intensities in gases, the which, being freely suspended on a rotating stand with controlled variable rotation, generated in its movement by action of centrifugal force a complex path of acoustic beams emitted that allows to sweep the surface on which the foam. Due to the effect of high acoustic intensity (> 170 dB ref. 2.10 <-4 \ mubar) much of the foam bubbles are gone breaking almost instantly to the passage of the ultrasonic beam.

State of the art Industrial sectors affected by problems of foams

Problems caused by excess foam in the processes, they affect a large number of industrial sectors: pharmacy and biochemistry, paper mills, detergents, enamel paints and varnishes, mining, textiles, beers and soft drinks, food in general, plastics, etc.

Problems caused by foam

Decrease in deposit capacity, deficiencies in processes and reactions, spills and loss of products, difficulties in dosing, packaging, filling and emptying, pollution, damaging effects on machinery and equipment, etc.

Industrial facilities where problems occur foams

Reactors, fermenters, mixers, tanks storage, distillers, evaporators, washing machines, channels evacuation, packaging machines, etc.

Characteristics of foams

Regarding the types of foam, it should be noted that there is a large degree of difficulty for its elimination despite Let the bubbles be 95% air. According to its "structure" a foam can be "wet" when the liquid layer of Bubbles is thick allowing spherical bubbles to form (shape for which the energy in the bubble is minimal); these bubbles, When they are small, they are difficult to break. Also the foam can be "dry", with a thin liquid layer on the bubbles, polyhedral shapes. This foam is normally formed when draining the liquid, after a while and, in general, it is easy to break.

According to its "stability" the foam can be: unstable (progress continuously), metastable (that stops progress), transient (the foam has a very short life), persistent (life of hours or days).

The stability of the bubbles depends on their ability to deform without breaking (Gibbs elasticity) which is linked to the amount of surfactant (surfactant that lowers the surface tension) in the liquid layer and the thickness of it. Also important are the viscosity of the liquid (the higher the viscosity of the liquid, the more stable is the foam) and the size of bubbles (the smallest are the most
stable).

"Foaminess" (ability to generate foam) is another important feature, which depends essentially of the activity of the surfactant and its concentration. The impurities present in the liquid (colloids, proteins, salts, etc.)

Commercial systems for foam removal

Currently the most commonly used systems They are: chemical defoamers mechanical systems, vacuum systems, water jet or spray and thermal methods. Defoamers Chemicals are the most widespread but have the problem of interfere with the processes and add an item to the product that It can be polluting and, in any case, unwanted. This difficulty It is particularly important in industries such as food and Pharmaceutical

Mechanical systems have the problem of their Low efficiency, especially to eliminate the finest foam. The thermal methods that consist of heating and cooling foams They are expensive and difficult to apply. (1)

Sonic and ultrasonic systems to eliminate foams

They developed experimentally between the years 1950-1970 using dynamic and static sirens, With pressurized air. Fermentation foams were treated and mining processes.

The problems of these systems were their limited acoustic emission level (144-154 dB) its low performance especially at ultrasonic frequencies (20 KHz) as well as the disturbances generated by the introduction of external air (2). Currently we have no news of commercial systems of this type.

Some devices have been patented, to Remove foams, which use ultrasonic vibrators. One of them, place the vibrator very close to a small inclined channel where the foam flows; 1000 Pa (154 dB) levels in a small sector where, when passing, bubbles are removed (3). Another device uses a 20 KHz piezoelectric vibrator, finished in a set of mechanical amplifiers that, put very close to a filling line, vibrating with 60 µm of vibratory displacement, remove foam from carton packs, before going through the sealing point (4). In general these systems are very limited and only serve to act on Very small surfaces

References

1. Foam control in Submerged Fermentation: State of the Art. NP Ghildyal , BK Lonsane , and NG Karanth . Advances in Applied Microbiology , Volume 33, 1988 pp. 173-222.

2. Foam control by acoustics and aerodynamic means RM Boucher and AL Weiner . British Chemical Engineering, Vol. 8, No. 12, Dec 01- 1963 pp.808-812.

3. Apparatus for liquefying bubbles using ultrasonic wave. Iwatani , Toshiyuki , c / o Kawasaki steel Co. European Patent Application No. 94102291.5, 04-01- 1995

4. Method and apparatus for removing froth on a liquid. Erwin Matzner UK Patent application No. 8002292, 23 Jan 1980

5. High power ultrasonic equipment for industrial defoaming. G. Rodríguez , JA Gallego , A. Ramos , E. Andres , JL San Emeterio , F. Montoya . Ultrasonics International 85, Conf. Proc. pp. 506-511.

6. Electroacoustics unit for generating high sonic and ultrasonic intensities in gases and interphases. JA Gallego Juárez, G. Rodríguez Corral, JL San Emeterio and F. Montoya Vitini. USA Patent No. 5299175 ( 1994 ).

Description of the invention

The device object of the invention is based on the use of ultrasonic profile plate emitters staggered / ribbed. These issuers properly suspended freely with a rocker device in a rotation system variable, can cover with its narrow but intense beam of emission A large area area.

On emitters of the vibrating plate type a bending with stepped / grooved profile (6), the geometry of this profile determines obtaining a directive issuance or focused. With this type of emitter it is possible to concentrate the emission in a small volume and get, for a frequency of 20 KHz and an applied power of 350 W, levels greater than 170 dB. This high sound pressure level allows the foam to break in very short times (10-20 milliseconds normally), depending on the type of foam.

The main mechanisms that act in the Ultrasonic foam breakage are high acoustic pressures, the radiation pressure, resonance of bubbles, wind Acoustic and cavitation in the liquid layer.

To destroy a foam by ultrasonic waves high acoustic intensity and a certain time of treatment. In addition to reduce the flow of foam that covers a wide surface it is necessary to radiate continuously with high acoustic intensity several points. This would force many high intensity acoustic sources or to sweep, shifting beam of a single ultrasonic emitter so suitable, on the surface of the foam.

The device that is patented allows to combine a certain treatment time (t_ {t}), when the emitter, in the area covered by the acoustic beam (10-20 milliseconds, depending on the type of foam and of the applied acoustic pressure), with a sweep time of beam (t_ {b}), of several seconds, which is repeated periodically, over the total area to be treated.

The sweep is obtained by a rotation variable of the emitter or of the ultrasonic emitters. Being the emitter (or emitters) freely suspended from a perpendicular arm at the axis of rotation and at a distance r thereof, the variation of the rotation speed n implies a variation of the angle that It forms the emitter shaft with the clamping bar per action of the centrifugal force (see fig. 1). In this way the emitter beam describe a spiral curve on the foam surface (Fig. 2) that will clearly differ from the circumference that I would describe in case of constant rotation speed. Yes that speed variation is repeated periodically, you have a "rotating" and "pendular" movement of the emitter on the foam surface that allows you to easily travel a Good part of the surface to be treated.

Example of application

The centrifugal force is

F_ = mv2 r;

M being the mass, v = 2 \ pirn the velocity tangential, r the turning radius and n the angular velocity of rotation. Tangential speed is limited by time minimum treatment (t_ {t}) needed to break the foam. This time is determined experimentally for each type of foam. If, for example, this time is t_ {t} = 15 ms and the beam covers an area of diameter (d) 6 cm, it will be that the maximum linear speed with which we can perform the treatment it will be V_ {maximum} = d / t_min = 0.06 / 0.015 = 4 m / s.

If the container where the foam is produced has a diameter of 3 m (r = 1.5m), the angular speed of rotation maximum will be n_ {max} = v_ {max} / 2 \ pir = 4/2 \ pi 1.5 = 0.42 r.p.s. or which is equal n_ {max} = 25 r.p.m.

The maximum angle that sweeps the beam of the emitter by The effect of the variable centrifugal force will be:

tgα_ {max} F_ {cmax} / P = (2 \ max_) 2 r / g 1.06 (P = emitter weight). That is to say, α_max 47 ° for the case considered.

If the sweep angle is not enough to cover most of the surface to be treated, can be put two or more emitters, located in different positions with respect to the axis of rotation. The arm should be balanced if necessary with additional masses

On the other hand the spiral type sweep of the emitter or emitters can be controlled electronically in such a way that compensate for the minimum treatment time of the peripheral ring, where you have the maximum tangential speed, with a greater number of laps in that position. The control curve of the system rotation presented in Fig. 3 is a qualitative example of the Time programming required. In general the sweep with the variation n = f (t) can be programmed and adjusted to the problem specific to each type of foam.

The device that is patented is shown on the Figure 4 installed in a closed container. This device It consists essentially of the following parts:

A rotor system (1) composed of an engine (2) with a reducer capable of mechanically varying the number of revolutions per minute. You must also provide sufficient torque to drag and stop the weight of the emitters located in the respective arms.

A rotating connector (3) with two or more circuits independent, that connect by means of brushes the feeding of electronic generators (4) to ultrasonic emitters to through the axis of rotation (5) which is hollow inside and whose length can be varied so that the focus of the emitters is located at the appropriate distance from the foam surface. In this vertical axis the electrical connections of power to the emitters (6); a shaft is also installed dynamic closure that ensures the tightness of the container. To the axis vertically an extendable arm (7) is coupled perpendicularly where one, two or more vibrating plate type emitters (8) are placed. These emitters are fixed to the horizontal arm by means of a support on a axis (9) that allows angular displacements thereof when Centrifugal force acts by rotating the system assembly. The system rotation is controlled directly by a electronic speed controller (10). This controller, which It consists of a power supply, an exciter of power and a microprocessor, has a program stored with different speed profiles that act on the feed the motor. A prototype similar to the one described above has been built and tested in a 1.5 m diameter cylindrical tank and 1.2 m high where various types of foams were generated for experimentation. Through this device, flows of fine foams (bubbles 1-10 mm in diameter) of order of 20 m 3 / hour.

Main features and advantages of the invention

The emitter radiates acoustic energy in air so very concentrated obtaining high levels of intensity (> 170dB). This allows to obtain a defoaming effect at a distance, without contact with foam or liquid.

The defoaming effect does not affect the characteristics of the liquid or foam, or its elements constituents Just destroy the bubbles by releasing the gas.

The bubble destruction effect is very fast (depending on the type of foam it may take a few milliseconds) This is why the acoustic emitter can be moved to relatively high speed: (2-3 m / s), eliminating in its path a certain volume of foam on which it acts.

Through a variable rotation system (a cycle of 0-50 rpm or less, repeated every 5 to 30 seconds), it is possible to sweep with the emitted acoustic beam a considerable area on which an effect of defoaming The defoamed volume produces on the foam neighboring a drag effect, allowing to regulate the level of foam of large containers. Variable rotation, you can Program to optimize the defoaming process.

The defoaming system can be built by closed parts, flexibly according to the container. Be they use authorized materials in the food industry and Pharmaceutical Part of the system can be installed inside hermetically sealed containers and from the outside you can vary the speed manually or automatically using a device electronic. The interior is isolated from the outside by a closure dynamic. The parts that go inside can be sterilized by steam at 110 ° C.

Explanation of the Figures

Fig. 1: Effect of change of orientation of the Ultrasonic emitter by the action of centrifugal force by varying the rotation speed of the clamping arm.

Fig. 2: Spiral type curve describing the ultrasonic beam on the surface to be foamed, by varying progressively the rotation speed of the shaft that supports the transmitter.

Fig. 3: Example of system control curve of rotation in which the variation of the rotation speed (n) with time (t).

Fig. 4: General scheme of the device to be patent that essentially consists of:

A rotor system (1) composed of an engine (2) (usually direct current) with a reducer capable of being able to vary the number of revolutions per minute. Also must provide enough torque to drag and stop the weight of the emitters located in the respective arms.

A rotating connector (3) with two or more circuits independent, that connect by means of brushes the feeding of electronic generators (4) to ultrasonic emitters to through the axis of rotation (5) which is hollow inside and whose length can be varied so that the focus of the emitters is located at the appropriate distance from the foam surface. In this vertical axis the electrical connections of power to the emitters (6). The vertical axis is coupled perpendicularly an extendable arm (7) where one, two are located or more vibrating plate type emitters (8). These issuers are set to horizontal arm by means of a support on an axis (9) that allows angular displacements thereof when the force acts centrifuge when rotating the system assembly. Rotation of system is controlled directly by a controller electronic speed (10) that generates different profiles of speed acting on the motor supply voltage. East controller, which is constituted by a power supply, a power exciter and a microprocessor, it has stored a program with different speed profiles. These profiles (speed curves) have as variable the speed of rotation and the sweep time.

Claims (10)

1. A device for removing foam and limiting its growth in containers and reactors by means of high intensity sonic or ultrasonic waves emitted through the air, characterized in that the acoustic emitter (or emitters) is of the stepped vibrating plate type that allows to obtain sonic beams of very high acoustic intensities (greater than 170 dB, ref. 2. 10-4). 2. A device according to claim 1 characterized in that the emitter or emitters that generate a high acoustic intensity move on the surface to be treated, at a certain distance from it without coming into contact with it. 3. A device according to each and every one of claims 1 and 2 characterized in that the maximum speed of movement of the emitter on the surface results in a treatment time that allows the foam of the surface to be treated to be completely broken. 4. A device according to each and every one of claims 1 and 2 and 3 characterized in that the path taken by the acoustic beam when traveling on the foam covers the entire surface to be treated. A device according to each and every one of claims 1 and 2 and 3 and 4 characterized in that by means of the variable rotation speed of the transmitter system of the emitter or acoustic emitters an additional pendular movement of the direction of the radiation of the emitter is generated or emitters on the surface to be foamed. A device according to each and every one of claims 1 and 2 and 3 and 4 and 5 characterized in that the control of the variable rotation speed of the emitter or emitter support system achieves a speed value that allows the foam to break and its growth. A device according to each and every one of claims 1 and 2 and 3 and 4 and 5 and 6 characterized in that the variable rotation system of the emitter or acoustic emitter suspension system uses additional mechanical, pneumatic, magnetic or electrical means of movement generation and control. A device according to each and every one of claims 1 and 2 and 3 and 4 and 5 and 6 and 7 characterized in that the suspension system of the emitter or acoustic emitters uses a ball joint or bearing to connect the emitter or acoustic emitters mounted on said suspension system. A device according to each and every one of claims 1 and 2 and 3 and 4 and 5 and 6 and 7 and 8 characterized in that the suspension system of the emitter or acoustic emitters contains a rotary connector for connecting the electronic generators to the or Acoustic emitters A device according to each and every one of claims 1 and 2 and 3 and 4 and 5 and 6 and 7 and 8 and 9 characterized in that the suspension system of the emitter or acoustic emitters is moved by means of a motor with control of programmable speed