ANNULAR DRYING ELEMENT, METHOD AND USE HEREOF AND DRYING APPARATUS

Abstract: Annular drying element (15) for mounting on a rotor axle in a drying apparatus, and where the drying element comprises at least two annular plate elements, a first (16') and a second plate element (16"), where at least the first plate element (16') is configured with a number of through-going openings (25) in the plate. The plate element with said openings (25) is lying opposite the non-broken through surface (51) of the adjacent plate element, and the plate elements are connected to one other by welding (52) along the edge (53) of the openings, and the non-broken through surface (51) lying in the bottom of an opening (25) is perced to provide through-going holes (54) through the annular plate element, extending from the one side to the other side of the drying element (15). There is hereby achieved an annular drying element, in that the substantially identical drying elements are assembled against each other by being welded together at the periphery and along the inner circumference, whereby a pressure-tight assembly is achieved. Moreover, welding is carried out along the whole periphery of the openings, so that this welding fastens partly agains the edge of the opening in the first plate and partly against the adjacent non-broken surface of the opposite plate element. There is hereby achieved a pressure-tight element, and where it is subsequently possible to carry out piercings corresponding to the earlier openings, insasmuch as here a piercing shall thus be carried out only through a single plate.

Description: ANNULAR DRYING ELEMENT, METHOD AND USE HEREOF AND DRYING APPARATUS The invention concerns an annular drying element for mounting on a rotor axle in a drying apparatus, and where the drying element comprises at least two annular plate elements, a first and a second plate element, where at least the first plate element is configured with a number of through-going openings in the plate. The invention also concerns a drying apparatus for heating or cooling of moist, comminuted material of animal, vegetable or chemical origin, comprising a stationary housing and a rotatable rotor, comprising a number of annular drying elements, each comprising at least two annular plate elements with means for the transport of a medium for heating or cooling hereof and for leading away possible condensation, and where at least the one plate element is configured with a number of through-going openings extending from the one side of the plate to the other side of the plate. The invention also concerns a method and use of the method and of the annular drying element. A drying element of the kind disclosed in the introduction is known, for example, from WO 98/15791. With drying elements of this kind, a large heating area is provided at the same time that a good stirring and trans- port of the product being processed is achieved, where said product can be products containing fat or oil, abattoir waste, biological materials of various character such as fishmeal, brewery waste and similar materials of animal, vegetable or chemical origin. The drying elements constitute a form of heat exchanger and are used for indirect heating or cooling of said products. However, there is the risk with such an annular drying element that the cavity which is formed between the two plate elements is not sufficiently tight, and is thus not able to withstand the pressures which arise during the introduction of steam etc. The object of the present invention is thus to provide a drying element which is pressure-tight, and where this pressure-tightness is ensured during the actual production, and where there is also achieved the suitable opening for ensuring a flow of the product in the machine in which the an- nular drying element may have been placed. This is achieved with an annular drying element of the kind disclosed in the preamble, and also where the plate element with said openings is disposed opposite the non-perforated surface of the adjoining plate element, and where the plate elements are connected to each other by welds at the edge of the openings, and that the non-perforated surface lying in the bottom of an opening is perforated to provide through-going holes in the annular drying element extending from the one side to the other side of the drying element. The idea with an annular drying element is thus that two substantially identical plate elements are assembled against each other by welding together at the periphery and at the inner circumference, whereby a pressure-tight assembly is achieved. Welds are also effected along the whole of the peripheries of the openings, so that this welding fastens partly against the opening edge of the first plate and partly against the adjoining non-perforated surface of the opposite plate element. There is hereby provided a pressure-tight element, and where perforations are subsequently carried out corresponding to the earlier openings, inasmuch as a per- foration here shall only take place through a single plate. By providing an annular drying element according to the invention, and as disclosed in claim 2, a doubling of the possible passage openings is achieved for the fluid which shall be handled by the annular drying element. By providing an annular drying element according to the invention, and as disclosed in claim 3, there is achieved a suitable contact surface of the one plate element against the other, in that the upper edge of this outward swaging will thus lie against the non-perforated area of the adjoining sur- face, and where the height of the swaging thus comes to define the space which must exist between the two plate elements. By providing an annular drying element according to the invention, and as disclosed in claim 4, a good stirring together of the substance is achieved and the surface of the heat exchanger is increased. By providing an annular drying element according to the invention, and as disclosed in claim 5, 6 and 7, an expedient and simplified production of the annular drying element is achieved, and there is achieved a very strong and rigid construction which can withstand a high pressure, which makes it possible for steam at a high temperature to be used as heating medium. The tube pieces are preferably configured as disclosed and characterised in claim 8, i.e. with circular cross-section profiles, which among other things make it possible to use tubes of standard production which are cut off in the desired lengths. The tube pieces can have a length as disclosed in claim 9. When use is made of such a length, this corresponds to the thickness of the element, and whereby the possibility is provided of using scraper elements in the drying apparatus which scrape the drying ele- ments clean which, for example, can be relevant at that end where the product is the most moist or in the zone where the product is most viscous. However, it is also possible for the tube pieces to be of a diameter as disclosed in claim 10, whereby the possibility is achieved of being able to vary the drying element in cases where larger openings or smaller openings are required. The invention also concerns a drying apparatus as disclosed in the preamble to claim 11 , and also where the plate element with openings is disposed with said openings opposite the non-perforated surface of the adjoining plate element, and where the plate elements are connected to one another by welds at the edge of the openings, and the non-perforated area lying in the bottom of an opening is pierced to provide holes through the annular drying element extending from the one side to the other side of the drying element. By means of such an apparatus, the earlier used advantages are achieved during use of the annular drying element in said drying apparatus. The claims 12-17 disclose expedient example embodiments of the drying apparatus. The invention also concerns a method as disclosed in claim 18 and the use of the method as disclosed in claim 19. Furthermore, the invention concerns use of an annular drying element as disclosed in claim 20. The invention will now be explained in more detail with reference to the drawing, where fig. 1 shows a first embodiment of the drying element according to the invention, fig. 2 shows a section along the line 11-11 in fig. 1 , fig. 3 shows the section shown in fig. 2, where perforations are effected through the openings, fig. 4 shows a plate element for the production of an annular drying element according to the invention, fig. 5 shows an example embodiment, and where tube pieces are placed in the holes, fig. 6 shows a second embodiment of a drying element according to the invention, fig. 7A shows a section in fig. 6 seen in the direction VII-VII and shown on a larger scale, fig. 7B shows that shown in fig. 7A and with tube pieces mounted in the holes, figs. 8A and 8B show an axial cross-section through the drying apparatus according to the invention. Fig. 1 shows an annular drying element 15 seen from the front, where the foremost plate element, i.e. the first plate element 16' is shown. The plate elements are circular with an outer and an inner diameter, and where along the outer edge 18 they are welded against each other to form a tight closure, and where along the inner edge, the so-called annular base part 17, they are similarly welded together and surround an axle. In the annular plate part itself, a number of openings 25 are provided. These openings 25 are preferably cylindrical and, where the first plate element 16' is concerned, they will be placed opposite the unbroken surface 51 of a second plate element 16", i.e. in the areas between the openings 25 in the second plate element 16". The two plate elements 16', 16" are also welded along the periphery of the opening 25 in the provision of a weld 52 along the whole of the edge 53 of the opening. The non-perforated surface in the bottom of such an opening is shown by the reference number 51. Fig. 2 shows a section along Il-ll in fig. 1 , and shows the first plate element 16' welded against the second plate element 16". The distance between the two elements corresponds to the height of the outward swaging 55, which demarcates the openings 25 provided in both of the plate elements. The geometry of the swaging appears almost crater-like, both in cross- section and in the plan view. Between the two plate elements 16', 16" there is thus formed an annular opening 23 in which steam and the like is retained under pressure. As mentioned, the two plate elements are welded together by welds 52 along all of the annular openings 25, so that the opening edge 53 of the swaging 55 is in abutment against the non-perforated surface 51 of the second plate element. A piercing will be carried out later, the so-called breaking-through, corresponding to the centre and at the same centre distance of these welded areas, in the provision of a through-going hole 54 such as will be seen in fig. 3. The through-going hole 54 is thus essentially smaller than the opening 25. Fig. 4 shows a section through a plate element before this is brought into contact against a second plate element in the formation of an annular drying element 15. Fig. 5 shows an example of a second embodiment according to the invention, with a section through the annular drying element. The drying element consists of two identical, plane, annular disks or plate elements of steel plate. The annular disks or plate elements are e.g. 2m in diameter and have a number of holes 25, e.g. 42. The two plate elements are coupled together, i.e. they are joined together at the outer edge 18 by means of an annular steel band 19 and an annular weld 20. At the inner edge/the foot part, the plate elements are provided with an annular base piece on each plate element. The plate elements have a thickness in the order of 4-20mm. In all of the openings 25, a tube piece 26 is inserted and welded fast to both plate elements, so that the tube pieces 26 constitute stays between the plate elements. In the example shown, the stays are four-inch tube pieces. The tubular stays 26 are robust and are welded securely to the two plate elements, so that between these there appears a chamber 22 for a heating medium, for example steam, under a pressure of 10 bar, said chamber having an annular opening 23 for the supply of steam and the discharge of exhaust steam and condensation in a commonly known manner. The foot pieces 17, which as shown in the drawing extend out on each side of the plate element, are arranged to be welded directly together with the adjacent elements, and hereby constitute a tube element which surrounds the rotor axle in the drying apparatus. In the example, the axes of the tubular stays 26 are parallel with the axis 30 of the drying element, and the tubular stays are of such a length that they correspond substantially to the thickness of the element. However, the tubular stays will be able to extend out over the surface of the element, and they will also be able to be cut off non-parallel with the element's plate and at an inclined angle hereto, possibly with another shape so that the projecting tubular stays constitute vane elements, carriers or stirring elements which have influ- ence on the stirring of the material which is dried in the apparatus. The tubular stays and herewith the openings 25 are arranged in two circles 28 concentric with the outer edge 18 of the drying element, and staggered in relation to one another so that a substantially uniform dis- tribution of the through-going holes 54 is achieved and, where tubular stays are provided, also a uniform distribution of the annular stays across the element, whereby it is achieved that the free plate area between the tubular stays does not become too large. This is of significance with regard to how great a steam pressure can be applied to the element without too great a deflection of the plate material arising between the tubular stays. Fig. 6-7 show an example where use is made of a drying element 15 of the same size, but where a larger number of smaller tubular stays are used, i.e. 90 stays distributed over three concentric circles 28, where the tubular stays are three-inch stays. Fig. 7A is a section along the line VII A in fig. 6, and before a piercing is carried out in the provision of the holes 54. Fig. 7B shows the same as in fig. 7A after the piercing has been carried out, and where tube pieces have been inserted in the holes. According to the invention, regardless of the material to be processed in a drying apparatus, i.e. regardless of the consistency of the material, its moistness, grain size etc., it is thus possible to dimension the drying elements in an optimum manner by selection of the size of the through-going holes, and in the cases where tubular stays are used, by selecting the number of these and also their size, configuration and positioning, so that the resulting drying apparatus has an optimal energy consumption without any sacrifice in the quality of the apparatus with regard to lifetime and operational reliability. Fig. 8A and 8B show an axial cross-section through a drying apparatus according to the invention. The centre axis 30 of the rotor is indicated, and above this is seen the central pipe 11 for the supply of steam for heating and removal of condensate, which is carried out in a commonly known manner. A number of annular drying elements 15 of the type discussed earlier in connection with fig. 1-7 are built up of plate elements, and via their foot pieces 17 are welded together in an annular manner around the central pipe 11. The drying elements can be supplied with steam for heat- ing via the stub connections 35. The central pipe 11 is shown terminated at the one end with an axle journal 37 in a commonly known manner, and sealed off by the wall 32 of the housing 2. The drying apparatus is otherwise built up in a commonly known manner and is therefore not explained in detail. As explained earlier, each of the annular drying elements 15 comprise a number of through-going openings in the axial direction, and said openings can be provided with tubular stays 26. In the drying apparatus accord- ing to the invention, all of the annular drying elements 15 are welded together at the annular foot pieces 17 in such a way that the through-going openings 25 lie axially in line, so that holes lying opposite have the same centre axis. It is hereby possible to mount axial, elongated elements 31 through the openings, e.g. in the form of hollow tubes as shown in the figures. The elements 31 are at least of a length which enables them to span over the space between two adjacent drying elements 15, preferably over three adjacent drying elements. The elements 31 can be tubular as shown, and can be divided into hold- ing parts 31 A for engagement with the drying elements 15, and in lifting parts 31 B which can be configured in any desirable manner so that they constitute a lifting element. The areas 31 B can, for example, be polygonal or directly U-shaped, so that the product to be processed is lifted during rotation. The elements 31 are preferably fastened to the first of the annular drying elements 15 by welding 31 E. The elements 31 are preferably standard tubes with a diameter with which they substantially fill out the tubular stays 26. A cover 33 can be provided in the end wail 32 of the housing, fastened for example with bolts 34. When the cover is removed, it is possible to insert or remove drying elements 31 in or from the rotor, in that by rotation of the rotor the openings in the drying elements 15 can be brought in line with the opening which lies under the cover. The insertion of an element 31 is indicated sketch-wise. In the example shown, elongated elements 31 are placed in some of the outermost openings 25 and in some of the innermost openings, but not in the centremost openings. The number of elongated elements and where they are placed depends on the degree to which it is desired to increase the stirring. In the examples shown, four elements 31 displaced 90° are inserted in the outermost openings 25, and four elements similarly displaced 90° in the innermost openings, i.e. eight elements in all. It will be obvious to a person skilled in the art that the number of elements 31 and their positioning depends on many different factors, e.g. the type of product to be processed, the manner in which it is desired to be handled, how the rotor is arranged and dimensioned etc. Fig. 8A shows an embodiment of the invention where at the one end all of the elongated tube elements 31 are welded together by welds 31 d with a manifold 39, which comprises a distribution chamber 40 and a supply pipe 41 for steam. The opposite ends of the elements 31 are blanked off by closures 31c. With steam heating, condensation is formed which can be led away in the same direction as that in which the steam is introduced. This can be effected, for example, by inclining the drying apparatus slightly towards the manifold 39, e.g. a slope of a few degrees, so that the condensation can return to the manifold 39 of its own accord.

Claims: CLAIMS 1. Annular drying element (15) for mounting on a rotor axle in a drying apparatus, and where the drying element comprises at least two annular plate elements, a first (16') and a second plate element (16"), where at least the first plate element (16') is configured with a number of through- going openings (25) in the plate, characterised in that the plate element with said openings (25) is placed opposite the non-perforated surface (51) of the adjoining plate element, and that the plate elements are connected to one another by welds (52) at the edge (53) of the openings, and that the non-perforated surface (51) lying in the bottom of an opening (25) is pierced to provide the annular drying element with through-going holes (54), extending from the one side to the other side of the drying element (15). 2. Annular drying element according to claim 1, characterised in that both the first (16') and the second (16") plate element comprises openings (25), said openings lying opposite the non-perforated surface (51) of the adjoining plate element. 3. Annular drying element according to any of the foregoing claims, characterised in that the openings are demarcated by an outwards swaging (55) along the full periphery of the openings. 4. Annular drying element according to any of the foregoing claims, ch a ra cte rised in that tube pieces (26) are inserted in the holes (54). 5. Annular drying element according to claim 4, characterised in that the tube pieces (26) are positioned so that their longitudinal axes are parallel with the axis (30) of the drying element. 6. Annular drying element according to claim 4 or 5, characterised in that each element comprises two substantially identical plate elements (16', 16") arranged at a distance from one another. 7. Annular drying element according to claim 4-6, characterised in that the tube pieces (26,27) are secured as stays between the plate elements which are configured with holes (54) corresponding to the tube pieces (26). 8. Annular drying element according to claim 4-7, characterised in that the tube pieces (26) have circular cross-section profiles, and that the holes (54) in which they are preferably mounted by welding are similarly circular. 9. Annular drying element according to claim 4-8, characterised in that the tube pieces (26) have a length which corresponds substantially to the thickness of the element (15). 10. Annular drying element according to claim 4-9, characterised in that use is made of pipe pieces (26) with different diameters. 11. Drying apparatus for the heating or cooling of moist, comminuted materials of animal, vegetable or chemical origin, comprising a stationary housing (32) and a rotatable rotor comprising a number of annular drying elements (15), each comprising at least two annular plate elements (16', 16") with means for the delivery of a medium for heating or cooling said materials, and for the leading away of possible condensation, and where at least the one plate element is configured with a number of through-going openings (25) extending from the one side of the plate to the other, characterised in that the plate element (16') with openings (25) is arranged with said openings opposite the non-perforated sur- face (51) of the adjoining plate element (16"), that the plate elements (16', 16") are connected to each other by welding (52) along the edges (53) of the openings, and that the non-perforated surface (51) lying in the bottom of an opening (25) is pierced to provide the annular drying element 5 with through-going holes (54), extending from the one side to the other side of the drying element. 12. Drying apparatus according to claim 11, characterised in that both the first (16') and the second plate element (16") comprises openings 10 (25), said openings lying opposite the non-perforated surface (51) of the adjoining plate element. 2. 13. Drying apparatus according to claim 11-12, cha racterised in that the openings are demarcated by an outwards swaging (55) along the 15 full periphery of the openings (25). 14. Drying apparatus according to claim 11-13, characterised in that the drying elements (15) are positioned on the rotor (11) in such a manner that at least one through-going hole (54) is lying axially opposite 20 corresponding through-going holes in an adjacent element, and that in said holes (54) there is inserted at least one elongated element (31) with a length which corresponds at least to the distance between the drying elements. 25 15. Drying apparatus according to claim 14, characterised in that the element (31) is divided into areas for engagement with a drying element, and in intermediate areas for positioning between the drying elements, and arranged for the lifting/stirring of the product in the apparatus. 16. Drying apparatus according to claim 14-15, c h a r a c t e r i s e d in that each element (31 ) is mechanically fastened to a drying element by e.g. welding. 17. Drying apparatus according to claim 14-16, c h a r a c t e r i s e d in that at least one of the elements (31 ) has a through-going cavity arranged for the introduction of a medium for heating or cooling, e.g. steam for heating. 18. Method for the production of an annular drying element (15) for mounting on a rotor axle in a drying apparatus, and where the drying element comprises at least two annular plate elements, a first (16') and a second plate element (16"), where at least the first plate element (16') is configured with a number of through-going openings (25) in the plate, c h a r a c t e r i s e d in that the plate element with said openings (25) is placed with the openings opposite the non-perforated surface (51) of the adjacent plate element, and that the plate elements are connected to one other by welding (52) along the edge (53) of the openings, and that the non-broken through surface (51 ) lying in the bottom of an opening (25) is pierced to provide through-going holes (54) in the annular drying element, extending from the one side to the other side of the drying element (15). 19. Use of the method according to claim 18 for the production of an annular drying element according to claim 1-10. 20. Use of an annular drying element according to claim 1-10 for the production of a drying apparatus according to claim 11-17.

Inventors: FOSBOEL PEDER, FOSBOEL, PEDER
Applicants: ATLAS STORD DENMARK AS, FOSBOEL PEDER, ATLAS-STORD DENMARK A/S, FOSBOEL, PEDER
Application year: 2001
Main classification: F26B11
IPC codes: F26B17