MXPA99005198A - Method to make more effective the sec - Google Patents

Abstract

The present invention relates to a method for making more effective the drying of finely divided materials, methods in which a filter cake is formed by suction from a slurry containing a liquid and finely divided solids, on a substantially flat surface of a filter medium, the filter cake has substantially planar external and internal flat surfaces, said inner surfaces being in contact with an external surface of the filter medium, the method comprising placing the outer surface of the filter cake and an outer surface substantially flat of an oscillator with mechanical contact therebetween, so as to generate an acoustic field having an oscillation frequency, throughout the filter cake, wherein the entire external surface of said oscillator is in substantially continuous contact with said external surface of said filter cake when said sound field is generated, and removing the residual liquid that is in the filter cake and that is difficult to eliminate by said suction only by the application of the acoustic field to the outer surface of said filter cake

Description

METHOD FOR MAKING DRY MORE EFFECTIVE Field of the Invention The present invention relates to a method for making the drying of materials, particularly finely divided materials, more effective by subjecting the filter cake made from said materials to the influence of an acoustic field.

Background of the Invention A limiting factor in the filtration of finely divided materials, such as fine sulphide concentrates, titanium pigments, kaolin or calcite, is the high flow resistance of the filter cake as well as its enormous internal area, the which catches large quantities of the liquid to be filtered. Naturally, the residual humidity is also affected by the capillaries formed by small particles and their capillarity forces. In this way, the filtration capacity is kept low and the residual moisture in the filter cake remains high. The residual moisture of the filter cake is bound to the cake material by various mechanisms. Part of the liquid to be filtered is adsorbed on the surface of the particles as a thin layer. The removal of this liquid is not possible without heat energy. Part of the liquid is trapped by the capillary networks formed by the particles. Depending on the chemistry of the surface of said particles and the diameter of the capillarity, with a given pressure difference, a given amount of liquid remains. By increasing the pressure difference, the liquid can be eliminated through increasingly smaller pores, which reduces the residual moisture. Moreover, part of the liquid is trapped in extremely narrow capillaries and at points of contact of particles, as well as in closed pores. In the application WO 96 / 35,340 a method for drying food products and other materials is described, said method applies a combination of hot air and ultrasonic oscillation. The products to be dried are transported through a closed chamber, so that inside the chamber the products are subjected to the influence of hot air. In the chamber, ultrasonic waves are conducted to the products by means of flat ultrasonic oscillators, which are in direct contact with the products to be dried. The method described in said application WO 96/35340 is designed for materials such as vegetables, which are dried as complete articles. In that case the specific area to be dried is very small compared to finely divided materials.

Objects of the Invention The object of the present invention is to eliminate some of the disadvantages of the prior art and achieve a new and more effective method for drying materials filtered in a suction dryer, particularly finely divided materials and with a larger particle size. small 100 micrometer, so that the filter cake prepared from said material is subjected to the influence of an acoustic field with the purpose of reducing the residual moisture of the filter cake. The essentially novel features of the invention will be more clearly appreciated from the appended claims.

Brief Description of the Drawings Figure 1 is a side view illustrating a preferred embodiment of the invention, Figure 2 illustrates the preferred embodiment of Figure 1, seen in the AA direction, Figure 3 is a side view illustrating another embodiment preferred of the invention. Figure 4 illustrates the preferred embodiment of Figure 3, seen in the BB direction, Figure 5 is a side view of a third preferred embodiment of the invention, and Figure 6 illustrates the preferred embodiment of Figure 5, seen at CC address, Detailed Description of the Preferred Modes In the method according to the invention, of the finely divided solids that are present in the slurry, a filter cake is first produced on the surface of the filter medium. According to the invention, the filter cake produced can be further dried by means of an oscillation generated by an acoustic field, whereby the filter cake and the oscillator are additionally arranged, one with respect to the other, in a position wherein a mechanical contact is achieved between the filter cake and the oscillator used to effect the drying process, or a structural element oscillated by means of said oscillator. The mechanical contact between the oscillator or the oscillating structural element oscillated by means of said oscillator and the filter cake creates an acoustic coupling. By virtue of said acoustic coupling, the residual moisture remaining in said filter cake can be reduced, and in this way the filtrate is further improved, because the acoustic field created by said acoustic coupling creates oscillation in the cake. filtered and, consequently, it eliminates water, which is difficult to eliminate in some other way. In the method according to the invention, the surface of the oscillator or of the structural element that is oscillated by means of said oscillator mechanically touching the filter cake is arranged, with respect to the filter cake, in a position where the Filtering cake, essentially all along the entire surface opposite the filtering surface, is in mechanical contact with the surface of the oscillator or of the structural element that is made to oscillate. Advantageously, the mechanical contact is achieved in such a way that the filter cake is caused to move ahead of the permanently installed oscillator or of the structural element oscillated by means of the oscillator, in which case the surface of the filter cake opposite the filter medium, it does, at least from time to time, a mechanical contact in order to create an acoustic field. A mechanical contact, and hence an acoustic field, between the oscillator or the structural element that is oscillated and the filter cake can also be achieved in such a way that the oscillator or the structural element that is made to oscillate moves with respect to the filtering cake. The movement of the oscillator or of the structural element that is made to oscillate with respect to the filter cake is carried out, for example, so that the oscillator or the structural element that is made to oscillate is transferred towards the surface of the filter cake that it is opposite to the filter medium, and the movement of the oscillator or of the structural element that is made to oscillate is stopped, when a mechanical contact is made. Now the acoustic field can be substantially and simultaneously substantially focused on the entire filter cake. The movement of the oscillator or of the structural element that is made to oscillate, with respect to the filter cake, can also be carried out so that the oscillator or the structural element that is made to oscillate moves forward of that surface of the cake of permanently installed filtrate that is opposite the filtering medium, so that a mechanical contact is achieved between the filter surface and the oscillator or the structural element that is oscillated in order to create an acoustic field. The oscillation frequency applied in the method according to the invention is advantageously within the range of 20-60 kHz. Lower frequencies can also be applied, but these lower frequencies can lead to environmental hazards due to the extremely high noise level caused by the low frequency. The amplitude used in relation to the oscillation frequency is inversely proportional to the oscillation frequency, such that a lower amplitude is applied at a higher frequency. Advantageously, the oscillator used in the method according to the invention is an ultrasonic oscillator, for example. In order to generate oscillation, a piezoelectric material or a magnetostrictive material can also be used, either as the oscillator itself or in the structural element attached to said oscillator.

Materials that are suitable for use in the method according to the invention advantageously have a particle size in the range of 0.5-10 microns. Such materials are for example copper and zinc sulphide concentrates, titanium pigments, kaolin, calcite and organic compounds, such as starch. However, depending on the structure of the material, the range of the particle size advantageously for the application of the method can be markedly larger. In that case the variation in particle size can be 0.01 - 100 micrometers. According to Figures 1 and 2, the filter cake 2, placed on the surface of the filter medium 1 is made of the slurry 4 consisting of solids and liquids and that is contained in the slurry tank 3. The support structure 5 of the filter medium 1 is installed so that by means of the support structure 5, the filter cake 2 formed on the surface of the filter medium 1 is movable with respect to the oscillator 6. An element is connected to said oscillator 6. structural 7 that can be oscillated by virtue of the oscillator 6, said structural element 7 being placed, in relation to the support structure 5 of the filtering device, so that while moving the support structure 5, in the middle of that surface 8 of the filter cake 2 which is opposite the filter medium 1, and that surface 9 of the structural element 7 constituting an outer surface in relation to the oscillator 6, creates a contact m when the filter cake 2 is being displaced in front of the structural element 7. When the filter cake 2 is displaced in front of the structural element 7, the structural element 7 is oscillated, and between the filter cake 2 and the structural element 7 an acoustic field is generated in order to reduce the residual moisture remaining in the filter cake 2. In the embodiment according to Figures 3 and 4, the filter cake 12 located on the surface of the filter medium 21 is made of slurry 14 consisting of solids and liquid and contained in a slurry tank 13. The filter cake 12 is oscillated by virtue of an oscillating structural element 16 attached to the oscillator 15, so that said structural element 16 moves towards the surface 17 of the filter cake 12 opposite the filter medium 11, until that surface 18 of the structural element 16 which is positioned opposite to the oscillation 15 and the surface 17 of the filter cake are in mechanical contact with each other. The surface 18 of the structural element is advantageously shaped in such a way that the surface 18 covers the entire surface 17 of the filter cake and thus when in mechanical contact the surfaces 17 and 18 can be maintained in their positions, one with respect to the other. As the mechanical contact between the surfaces 17 and 18 is achieved, the structural element 16 is oscillated by virtue of the oscillator 15, so that an acoustic field is generated in the middle of said surfaces 17 and 18, and the filter cake 12 also begins to oscillate. Due to said oscillation, the residual moisture remaining in the filter cake 12 can be reduced. According to Figures 5 and 6, the filter cake 22 located on the surface of the filter medium 21 is made of slurry 24 consisting of solids and liquid contained in a slurry tank 23. The filter cake 22 is made to oscillate under of an oscillating structural element 26 attached to the oscillator 25, so that said structural element 26 moves towards the surface 27 of the filter cake 22 opposite the filter medium 21, until that surface 28 of the structural element 26 which is positioned opposite to the oscillator 25 and the surface 27 of the filter cake are in mechanical contact with each other. As the mechanical contact between surfaces 27 and 28 is achieved, the structural element 26 is oscillated by virtue of the oscillator 25, so that an acoustic field is generated as the structural element 26 is displaced along the surface 27. When the structural element 26 has passed over the entire surface 28 of the filter cake, the oscillation of the structural element 26 is stopped, in which case the acoustic coupling between the surfaces 27 and 28 also disappears.

Claims (8)

1. Novelty of the Invention 1. A method to make more effective the drying of materials, particularly finely divided materials, method in which a slurry containing liquid and solids is made a filter cake on the surface of the filter medium, characterized in that the cake filter and the oscillator are placed in relation to each other, so that in the middle of the filter cake and the oscillator an acoustic field is generated by virtue of a mechanical contact between the filter cake and the oscillator or an element structural attached to said oscillator.
2. 2. A method according to claim 1, characterized in that the filter cake is displaced relative to the oscillator.
3. 3. A method according to claim 1, characterized in that the structural element of the oscillator is offset with respect to the filter cake.
4. 4. A method according to claim 1, characterized in that the filter cake and the oscillator are held immobile with respect to each other, while there is a mechanical contact between them.
5. 5. A method according to any of the preceding claims, characterized in that the oscillation frequency of the acoustic field is within the range of 20-60 kHz.
6. 6. A method according to any of the preceding claims, characterized in that the oscillator used is an ultrasonic oscillator.
7. 7. A method according to any of the preceding claims 1-5, characterized in that the oscillator used is a piezoelectric material.
8. 8. A method according to any of the preceding claims 1-5, characterized in that the oscillator used is a magnetostrictive material.