US 3861059 A
An upright first conduit has an upper open end, and hot gas with entrained material which is to be dried is passed through the conduit so that it issues from the upper open end into an upwardly closed chamber. A second conduit surrounds the first conduit with clearance and has an upper open end also communicating with the said chamber and located in the region of the level of the open end of the first conduit. A third conduit surrounds the second conduit with clearance and its wall communicates with the wall of the chamber and it serves as the outlet for the hot gases. An arrangement is provided for raising and lowering the level of the upper open end of the second conduit with reference to that of the upper open end of the first conduit to thereby influence the flow conditions in the chamber from the first conduit to the third conduit.
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Description (OCR text may contain errors)
United States Patent 1 Lindemann et al.
[ Jan. 21, 1975 DRYING APPARATUS  Inventors: Wilhelm Lindemann, Appelhulsen;
Kurt Riisner, Munster, both of Germany  Assignee: Hazemag Dr. E. Andreas KG,
Munster, Germany  Filed: July 2, 1973  Appl. No.: 375,924
 Foreign Application Priority Data 3,015,390 l/1962 Stewart, Sr. 209/140 Primary Examiner-Manuel A. Antonakas Assistant Examiner-William C. Anderson Attorney, Agent, or Firm-Michael S. Striker  ABSTRACT An upright first conduit has an upper open end, and hot gas with entrained material which is to be dried is passed through the conduit so that it issues from the upper open end into an upwardly closcd chamber. A second conduit surrounds the first conduit with clearance and has an upper open end also communicating with the said chamber and located in the region of the level of the open end of the first conduit. A third conduit surrounds the second conduit with clearance and its wall communicates with the wall of the chamber and it serves as the outlet for the hot gases. An arrangement is provided for raising and lowering the level of the upper open end of the second conduit with reference to that of the upper open end of the first conduit to thereby influence the flow conditions in the chamber from the first conduit to the third conduit.
6 Claims, 2 Drawing Figures FATENTED 5 3,861,059
SHEET 10F 2 I My] DRYING APPARATUS BACKGROUND OF THE INVENTION The present invention relates generally to a drying apparatus, and more particularly to an apparatus for entraining and drying particulate materials.
It is already known to provide various types of drying apparatuses wherein materials are entrained by a stream of hot gas and dried as they are conveyed by the gas. They utilize an upright conduit through which the gas and entrained material are advanced in upward direction, so as to issue from an upper open end of this conduit. They enter from the upper open end into a chamber whose dimensions are larger than those of the conduit and in which the coarser and therefore as yet insufficiently dried particles -become separated from the finer and sufficiently dried particles. These coarser particles can then be recirculated and subjected to the drying action again, if desired.
In some of the prior-art apparatuses of this type, the separation of the coarser and finer (not yet properly dried, and already dried) particles takes place after the gas carrying the particles has been deflected upon issuing from the upper open end of the upright conduit only to one side. However, it has been found that this type of apparatus does not provide for a desired separation efficiency, because due to previous deflections the gas which passes through the upright conduit is given a whirling or rotary motion which it has as it issues from the upper open end of the conduit. The additional onesided deflection imparted to this gas stream and the en trained particles therein, thus creates in the chamber into which the gas stream and the particles issue flow conditions which disadvantageously influence the separation of dried and as yet undried particles.
Another type of prior-art construction utilizes a chamber which is round and is concentric with reference to the upper open end of the upright conduit. The separation takes place radially in all directions. The coarser particles are separated from the finer particles and the gas stream by venting the finer particles and the gas stream round deflecting baffles in upward direction, the intention being that the coarser particles should descend upon the influence of gravity through a collecting tube which surrounds the upright conduit with clearance. This construction, however, has the disadvantage that effected by the deflecting baffles, there will necessarily develope above the upper open end of the upright conduit a gas cushion which disadvantageously influences the separation of the lighter from the heavier particles. This causes uncontrolled eddies and these, in conjunction with the large ddiameter of the chamber which concentrically surrounds the open end of the conduit cause that much dry and fine material is deflected out of the intended path and allowed to enter into the outer conduit together with the heavier particles. It is then recirculated into the drying process which will necessarily be disadvantageously influenced in its efficiency by this fact. Moreover, the thus recirculated already dry fine material can become dried excessively and may actually be damaged.
Still another type of prior-art dryer withdraws the gas stream with both the fine and coarser particles from the chamber into which it issues out of the upright conduit, in downward direction. The separation takes place only later, in specific separating devices which, of course,
complicate the construction of the apparatus and increase its expense.
SUMMARY OF THE INVENTION According, it is a general object of the present invention to overcome the disadvantages of the prior art.
More particularly, it is an object of the present invention to provide a drying apparatus of the type in question which avoids the aforementioned disadvantages.
A further object of the invention is to provide such a drying apparatus which is highly efficient and inexpensive to construct and maintain.
Another object of the invention is to provide such a drying apparatus which is simple in its construction.
In keeping with these objects, and with others which will become apparent hereafter, one feature of the invention recites, in an apparatus for entraining and drying fluent materials, in a combination which comprises an upright first conduit having a first upper open end adapted to have hot gas and entrained material to be dried passed therethrough and out of the open end into an upwardly closed chamber. A second conduit surrounds the first conduit with clearance and has a second upper open end communicating with the chamber in the region of the first open end. A third conduit surrounds the second conduit with clearance and its wall communicates with the wall of the chamber and it serves as the outlet for the hot gases. Means is provided for varying the level of the second open end with reference to that of the first open end, to thereby influence gas and material flow conditions in the chamber.
With this construction, the issuing stream of gas and material forms in effect a fountain above the upper open end of the upright first conduit within the upper open end of the second conduit surpassing the first conduit and because the varying of the level of the second open end alters the height of the zone or area in which separation of the coarser particles can take place, the adjustment of the separation of dried fine and still moist coarse particles is greatly improved. The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic elevation, showing an embodiment of an apparatus according to the present invention; and
FIG. 2 is a diagrammatic fragmentary vertical section, on an enlarged scale, through a detail of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing the drawing in detail, wherein FIG. 1 shows the complete apparatus and FIG. 2 a detail of the apparatus, it will be seen that reference numeral 1 identifies an upright conduit through which a stream of hot gas produced in the gas generator 2 is drawn in upward direction by a ventilator or exhauster 3. Reference numeral 4 identifies a device which admixes the material to be dried, for instance in pulverulent, granular or similar form, with the stream of gas so that it is entrained by the same and advances with the same in upward direction through the conduit 1. A conduit 5 concentrically surrounds the conduit 1 with spacing therefrom, having a lower end which can be connected via a gating device 6 with the lower end of the conduit 1.
A further conduit 7 concentrically surrounds the conduit 5, also with clearance, and has an upper end which is closed (upwardly spaced from the upper open ends of the conduits 1 and 5) by means of a hood 8 which, together with the upper end portion of the conduit 7, defines a chamber 9. The lower end of the conduit 7 is connected with or merges into a conduit 10 which extends to a separator 11 with which it communicates.
In accordance with the present invention, the upper open end of the conduit 5 is provided with a collar or sleeve 12 which in the illustrated embodiment is configurated as a double-walled element of substantially U- shaped cross-section (see FIG. 2). The collar 12 straddles the upper open end of the conduit 5 so that one of its walls is located outside and its other wall is located inside the circumferential wall of the conduit 5. Reference numeral 13 identifies a tackle (rope or the like) or rod linkage which extends through the hood 8 and is connected with the collar 12. The element 13 is only diagrammatically illustrated, being well known to those skilled in the art. As indicated by the double-headed arrows in FIGS. 1 and 2, the element 13 can be used to raise and lower the collar 12 with reference to the stationary conduit 5 so that in effect the level of the upper open end of the conduit 5 is made to rise or descend, as the collar 12 (which acts as an extension of the upper end portion of the conduit 5) is raised or lowered. The finer and sufficiently dried material enters together with the hot gases into the conduit 7, and from there passes via the conduit 10 into the separator 11 (e.g., a cyclone) wherein it is separated from its entraining gas to issue through the discharge device 14, whereas the gas is vented via the chimney 15 in the direction of the associated arrow.
The material which is to be dried is admitted via the device 4 and is entrained by the gas stream flowing in the conduit 1, which lifts it therein. Within the conduit there will be a constant formation of eddies with the material rising at the center of the conduit 1 and descending with reference to the movement of gas at the center along the inner wall of the conduit 1. This significant turbulence causes the individual particles of material to be contacted again and again with fresh hot gas, so that a rapid heat exchange results in a rapid drying of the particles. The friction between the particles which is caused by the turbulence, and also between the particles and the wall of the conduit 1, and the stresses which develop in the interior of the particles due to formation of steam, aid in further fragmenting of the particles. The particles become lighter as they dry, and also as they become further fragmented, and finally issue at the upper open end of the conduit 1 into the chamber 9, to enter into the outer conduit 7 and from there into the separator 11.
The particles which are not yet sufficiently dried in the conduit 1, will rise at the center of the conduit and exit from the upper open end of the same. Due to the sudden increase of cross-section as the gas and the particles leave the conduit 1 and enter the space surrounded by the upper end of the conduit 5 formed by the collar 12 the gas flow speed will drop and the coarser not yet sufficiently dried particles will descend in the radially outer zone of this space and thus enter into the conduit 5 in which they will drop to the device 6 via which they can be returned into the conduit 1.
The collar 12 thus constitutes a larger-cross section extension of the conduit 1, in which conditions will develop analogous to those which obtain in the conduit 1 itself, and these conditions are not as in the prior art influenced by deflecting devices or the like. The stream of gas widens with its eddies in all directions as it enters from the conduit 1 into the space surrounded by the collar 12, and drops down. The higher the collar 12 is raised, the more the flow speed of the gas will be reduced and the more coarser and not sufficiently dried particles of the material to be dried will enter into the conduit 5 before the gas stream flows outwardly beyond the upper edge of the collar 12 and take along the lighter particles. Thus, a very precise separation of the particles into finer and coarser or heavier particles is possible without destroying the formation of a fountain above the upper open end of the conduit 1, which is so important for the efficiency and effectiveness of separation. Moreover, the degree of separation can be readily influenced,(i.e., the weight and size of the particles which are made to enter into the conduit 5 versus those which are made to enter into the conduit 7 can be varied) by raising or lowering the collar 12.
It will be appreciated that the collar 12 need not have the U-shaped cross section which has been illustrated, but could also be otherwise configurated.
It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the type described above.
While the invention as been illustrated and described as embodied in a drying apparatus, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:
1. In an apparatus for entraining and drying particulate materials including finer and coarser particles, a combination comprising an upright first conduit having a first upper open end and adapted to have hot gas and entrained material to be dried passed therethrough and out of said open end into an upwardly closed chamber; a second conduit surrounding said first conduit with clearance and having a second upper open end communicating with said chamber in the region of said first open end, and a lower end provided with an outlet for the coarser particles; a third conduit surrounding said second circuit with clearance and its wall communicating with the wall of said chamber and serving as the outlet in downward direction for said hot gas; and means for varying the extent to which the level of said second open end is higher than the level of said first 6 shaped cross-section, straddling said second open end and having an outer wall surrounding, and a concentric inner wall received within, said second conduit.
5. A combination as defined in claim 2, wherein said means further comprises a tackle for raising and lowering said collar.
6. A combination as defined in claim 2, wherein said means further comprises a rod linkage for raising and lowering said collar.