US 3927715 A
Apparatus for treating a material by indirect heat exchange comprising a plurality of decks along which the material is passed by transversely extending scrapper blades the ends of which are attached to conveyor chains, the decks comprising the tops of enclosed heat exchange chambers containing a heat exchange fluid. The material passes from one deck to another with the decks being vertically spaced so that material drops from one deck onto the next lower deck. Vapor emanating from the material is exhausted under a vacuum. The apparatus has particular utility for the drying of wet coal since the coal is maintained out of direct contact with the heating fluid and thus coal dust does not exhaust to the atmosphere in the heating fluid.
Claims available in
Description (OCR text may contain errors)
United States Patent 91 Castanoli [451 Dec. 23, 1975 MULTIPLE DECK DRYING APPARATUS  Filed: Aug. 16, 1974  Appl. No.: 498,029
 US. Cl. 165/120; 198/102; 34/20; 34/171  Int. Cl. F28F 7/00  Field of Search 62/63, 380; 165/120; 198/102, 168; 34/20, 171
Primary Examiner-Charles J. Myhre Assistant ExaminerTheophil W. Streule, Jr. Attorney, Agent, or Firm-Laurence, Stokes & Neilan [5 7] ABSTRACT Apparatus for treating a material by indirect heat exchange comprising a plurality of decks along which the material is passed by transversely extending scrapper blades the ends of which are attached to conveyor chains, the decks comprising the tops of enclosed heat exchange chambers containing a heat exchange fluid. The material passes from one deck to another with the decks being vertically spaced so that material drops from one deck onto the next lower deck. Vapor emanating from the material is exhausted under a vacuum. The apparatus has particular utility for the drying of wet coal since the coal is maintained out of direct contact with the heating fluid and thus coal dust does not exhaust to the atmosphere in the heating fluid.
VACUUM PRODUCER US. Patent 1360.23, 1975 Sheet2of2 3,927,715
comprises a deck which is the top of an enclosed heat exchange chamber, and conveying means for transporting the material along the upper surface of the deck in indirect heat exchange with a heat exchange fluid in the enclosed chamber. The apparatus is preferably maintained under vacuum so that when the material is being dried, the drying may be carried out at lower temperatures.
While the apparatus of the invention has many applications, for example, in food processing, desalination of water to obtain pure wate, and/or saltor bittern of any gravity for further treatment to produce magnesium chloride etc., and for drying of various particulate materials; the apparatus finds particular utility in the drying of wet coal. For illustration purposes, coal will in general be referred to as the material being dried throughout this description although it will be understood that this is merely for purpose of illustration.
As is well known, it is frequently necessary to dry wet coal. I-Ieretofore, prior art apparatus for this purpose have usually employed direct contact of the wet coal with a heating medium such as furnace gases or heated air. While this provides for intimate heat exchange, it is subject to the drawback that coal dust may be taken up by the heating gas and discharged to the atmosphere, even in installations in which dust collectors are employed. The dust laden steam and air emission may travel for miles and is a serious source of pollution.
When employing the apparatus of the subject invention, the coal or other material to be dried is not in direct contact with the gaseous heating medium. Therefore, atmospheric pollution is eliminated as is the need for dust collectors and the like. In addition, there is no contamination of the material being dried by the heat exchange fluid, which is essential in many applications. Since the drying is carried out under vacuum, the rate of moisture evaporation is far greater than at atmospheric pressure and in addition the chance of fire or scorching of the material being dried is minimized. In accordance with the invention, drying of coal takes place at temperatures considerably below the customarily 1000F. of prior art processes.
It will of course be appreciated that the apparatus is equally useful in cooling a material rather than heating the material.
Another object of the present invention is to provide an improved procedure for drying wet coal which substantially eliminates atmospheric pollution by coal dust and which substantially prevents fires and explosions while drying the coal.
Still another object of the invention is to provide a novel system for conveying wet material through a multiple deck treatment apparatus.
The above and other objects, features, and advantages of the invention will in part be obvious and will in part be pointed out as this description proceeds.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view of a presently preferred embodiment of the invention taken primarily in longitudinal, vertical cross-section.
FIG. 2 is a transverse vertical cross-section view of the apparatus of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, a presently preferred materal treating apparatus of the invention is shown which includes an air tight casing 10 having a pitched roof 12. Wet coal or other material to be treated enters an upper end of the casing 10 through an inlet duct 14 in which there is a star valve or other suitable metering device 16. Thecoal falls onto the right hand end of an upper metal deck 18 which constitutes the top of an enclosed heat exchange chamber 20. A partitioning device 24 may be utilized to split the incoming stream of coal and distribute it more evenly onto deck 18. There is an upper enclosed heat exchange chamber 26 which is spaced above the heat exchange chamber 20 and the coal on deck 18.
The coal is transported along deck 18 in a right to left direction by the upper pass of a first endless conveyor which comprises two endless chains 28 disposed adjacent the opposite longitudinal walls of casing 10. A plurality of metal scrapper blades 30 are attached to each of chains 28. The chains 28 are trained around two sprockets 32 at each end.
Beneath heat exchange chamber 20 there are three additional heat exchange chambers 34, 36, and 38 each having decks 40, 42, and 44 respectively. Each of the chambers and the four decks extend across substantially the full width of the casing 10. The lower pass of the first conveyor is between the heat exchange chambers 36 and 38 so that the scrapper blades 30 are in contact with the lowest deck 44 on the lower pass of the conveyor where the blades are moving from left to right.
A second smaller conveyor comprised of a pair of endless chains 46 and scrapper blades 48 is trained about a pair of small sprockets 50 at each end of the conveyor. As best seen in FIG. 1, the smaller conveyor is driven in the opposite direction to the larger conveyor and the upper pass of the small conveyor moves from left to right along the surface of deck 40. The lower pass of this conveyor movesfrom right to left across the surface of deck 42.
The path of the coal or other material being treated is thus from right to left along upper deck 18 to the end of this deck where it falls down the foreshortened inclined end 52 of chamber 20 onto the left end of deck 40. The upper pass of the smaller conveyor then transports the coal from left to right to the opposite end of the apparatus where the coal now falls down past end 54 of heat exchange chamber 34 onto deck 42. The lower pass of the small conveyor then transports the coal along deck 42 to the left until the coal falls past the end 56 of heat exchange chamber 36 onto the bottom deck 44. The lower pass of the first conveyor now pushes the nearly dried eoal along deck 44 to'the right hand end of the apparatus where the dried coal falls out through a discharge duct 58 to storage or if desired to another material treating unit identical to that described above for further drying, If necessary I It will of course be understood that conventional drive means for the two conveyors are provided. Such means are not illustrated since these details are hot important to the present invention and would unneees= saril complicate the drawin s. Preferably the two eon= Vejyors are driven at the same linear speed which can readil be accomplished by appropriately selecting the sizes of the sprockets, the number of teeth, and the rpms of the sprockets.
Preferably, one conveyor is driven by a motor at one end and the other conveyor is driven by a motor at the other end in order to simplify the drive arrangement.
Referring to FIG. 2, furnace gas or other suitable heat exchange medium in a duct 60 enters the apparatus through inlet 62 into the lower heat exchange chamber 38. At one side of the apparatus, there is a connecting duct 64 so that after the heat exchange medium has flown through the lower chamber 38 and cooled somewhat it enters the next higher heat exchange chamber, chamber 36. From chamber 36, the heat exchange medium goes through connecting duct 66 into heat exchange chamber 34. After transversing this chamber, the heat exchange medium flows through connecting duct 68 into heat exchange chamber 20 and then through connecting duct 70 into the upper heat exchange chamber 26. An exhaust fan 72 or the like draws the cooled heat exchange medium from upper chamber 26 out through discharge 74 into exhaust line 76. The heat exchange medium thus flows through the apparatusin the illustrated embodiment countercurrent to the flow of the coal or other material to be treated.
As shown in FIG. 2, there is a by-pass conduit 78 so that incoming furnace gas in line 60 may be by-passed by opening'valve 80 directly to the discharge duct 74.
Vapors, for example, water vapors, emanating from the coal is "drawn off into one of a plurality of vertically extending vapor exhaust conduits 82 at one or both sides of the casing 10. The upper ends of exhaust conduits 82 open into the portion of the casing above the upper heat exchange chamber 26 and below the roof 12. From this region, the vapors are withdrawn through a vapor discharge conduit 84 by suitable vacuum means (not shown). For example, the vacuum in this region may be in the order of inches of mercury. From the foregoing description, it is apparent that at no time is there direct contact between the coal and the heat exchange medium, and there is minimal movement of the coal and consequently minimal agitation of coal dust.
Although a presently preferred embodiment of the invention has been shown and described with particularity, it will be appreciated that many changes and modifications may readily suggest themselves to those of ordinary skill in the art upon being apprised of the present invention. It is intended to cover all such changes and modifications as fall within the scope and spirit of the appended claims.
1. Apparatus for subjecting a material to indirect heat exchange comprising an enclosed casing, means defining a plurality of closed chambers containing a heat exchange medium disposed in said casing and spaced in a vertical direction from each other, each of said chambers being defined in part by an upper impervious deck along which the material being treated moves, said decks preventing direct contact between the material thereon and the heat exchange medium in said chambers, endless conveyor means having an upper pass disposed adjacent to a deck of one of said chambers and having a lower pass disposed between and adjacent the upper deck of another of said chambers and a lower impervious bottom of the superadjacent chamber, said endless conveyor means including a plurality of transversely extending blades spaced therealong, said blades being positioned to move the material along said decks, means for introducing a material to be treated onto one end of the uppermost deck, means to transfer material from a deck onto the next lower deck, means to discharge treated material from the lower deck, and means for maintaining a vacuum in said casing to exhaust vapor emanating from said material.
2. Apparatus according to claim 1, further comprising connecting means interconnecting said chambers to enable heat exchange medium to flow from one chamber to another in sequence.
3. Apparatus according to claim 2, wherein said chambers and said decks extend substantially the full width of said casing.
4. Apparatus according to claim 1, wherein there are at least four decks, and wherein said endless conveyor means comprise a pair of endless conveyors each having two passes associated with different decks.
5. Apparatus according to claim 4, wherein said two conveyors comprise a large conveyor and a smaller conveyor, said large conveyor having its upper pass over the uppermost deck and having its lower pass over the lowermost deck, said smaller conveyor having its upper pass over the deck beneath the uppermost deck and its lower pass over the next deck below, said smaller conveyor being disposed between the upper and lower passes of said large conveyor, and means to drive said conveyors in opposite directions.