MXPA99005199A - Method to make more effective the sec - Google Patents

Abstract

The present invention relates to a method for making more effective the drying of materials, particularly finely divided materials, in a suction dryer provided with a fine pore suction surface, wherein the radii of the fine pores of the suction surface are essentially within the range of 0.5-2 micrometers, and method in which a slurry containing liquid and solids is made a filter cake on the fine pore liquid suction surface, which constitutes the filtering surface of the filter medium, characterized in which the filter cake and the oscillator are placed, in relation to one another, 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 a structural element attached to said oscillating

Description

METHOD FOR MAKING DRY MORE EFFECTIVE Field of the Invention The present invention relates to a method for making the drying of filtered materials in a suction dryer, particularly finely divided materials, more efficient by subjecting the filter cake of said materials to the influence of an acoustic field BACKGROUND OF THE INVENTION From the Finnish patent 61, 739 a drying method and apparatus for drying solid or porous material, in powder, with network configuration, method in which the material to be dried is placed is known. , by intermediation of a suction surface saturated with liquid and a fine porosity, to a hydraulic contact with a liquid maintained at low pressure in relation to the material to be dried. The apparatus used in said method comprises a thin-pored liquid suction surface, wherein the spokes of the fine pores are mainly within the range of 0.5-2 micrometers. The fine-pored liquid suction surface constitutes the filtering surface of the filter medium of the dryer by suction, filtering surface which is brought into contact with the material to be dried, such as a slurry. While the filter surface is for example of rather flat configuration, and by creating a low pressure on the opposite side with respect to the filter surface of the filter medium, on the surface of the filter it is formed, due to the influence of the suction, a filtered cake of the material to be dried, cake that is then detached from the filter surface. A limiting factor in the filtration of finely divided materials, such as fine sulphide concentrates, titanium pigments, kaolin or calcite, is the high resistance to flow of the filter cake as well as its enormous interior area, which traps 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 remains 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 articles 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.

Objectives 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 particle size smaller than 100 microns, 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 cake filtering 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 B-B, Figure 5 is a side view of a third preferred embodiment of the invention, and Figure 6 illustrates the preferred embodiment of Figure 5, viewed in the direction C-C, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method according to the invention, of the finely divided solids which are present in the slurry, a filter cake is first produced on the fine pore suction surface of the suction dryer. 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 increase 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 filter cake and, consequently, it removes water, which is difficult to eliminate in some other way. In the method according to the invention, the surface of the oscillator or 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 liquid suction surface, of fine pore, is in mechanical contact with the surface of the oscillator or the structural element that is made to oscillate. More advantageously the mechanical contact is achieved so that the filter cake is caused to move ahead of the permanently installed oscillator or the oscillating structural element oscillated by means of the oscillator, in which case the surface of the filter cake opposite the surface Liquid suction, of fine pore, makes, at least from time to time, a mechanical contact in order to create an acoustic field. A mechanical contact, and hence an acoustic field, in the middle of the oscillator or of 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 filter cake. The movement of the oscillator or the structural element that is oscillated with respect to the filter cake is carried out, for example, so that the oscillator or the structural element that is oscillated is transferred to the surface opposite the surface of the oscillator. suction of liquid, fine pore, from the filter cake, and the movement of the oscillator or 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 the permanently installed and opposite surface to the liquid suction surface, of fine pore, of the filter cake, 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. While the method according to the invention is applied to a suction dryer provided with a fine pore suction surface, wherein the spokes of the fine pores of the suction surface are mainly within the range of 0.5-2 micrometers, the residual moisture extracted from the filter cake due to the oscillation of the filter cake caused by the acoustic field is caused to be eliminated through the fine-pored liquid suction surface, which constitutes the filtering surface of the filter medium , when the pressure difference applied in the filtering process is maintained between the filtering surface and the surface of the filtering medium opposite said filtering surface. 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 fine-pored liquid suction surface, which constitutes the filtering surface, is made of the slurry 4 consisting of solids and liquids and which is contained in the grout 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 able to move with respect to the oscillator 6. To said oscillator 6 is connected a structural element 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 it moves the support structure 5, in the middle of that surface 8 of the filter cake 2 that is opposite the filter medium 1, and that surface 9 of the structural element 7 that constitutes a surface ex terior 9 in relation to the oscillator 6, a mechanical contact is created, 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 liquid suction surface, of fine pore, constituting the filtering surface of the filter medium 11 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 a structural element capable of oscillating 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 oscillator 15 and the surface 17 of the filter cake are in mechanical contact with each other. As the mechanical contact is made between the surfaces 17 and 18, 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 thin-pored liquid suction surface which constitutes the filtering surface of the filter medium 21 is made of slurry 24 consisting of solids and liquid contained in the filter. a slurry tank 23. The filter cake 22 is oscillated by virtue of an oscillating structural element 26 attached to the oscillator 25, so that said structural element 26 moves towards the surface 27 of the opposite filter cake 22 to the filtering 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 is made between the surfaces 27 and 28, 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, in a suction dryer provided with a fine pore suction surface, wherein the radii of the fine pores of the suction surface are essentially within the range of 0.5-2 micrometers, and method in which a slurry containing liquid and solids is made a filter cake on the fine pore liquid suction surface, which constitutes the filtering surface of the filter medium, characterized in which the filter cake and the oscillator are positioned, 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 filter cake. oscillator or a structural element 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 kept 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.