US3805406A

US3805406A - Interchangeable path drying apparatus

Info

Publication number: US3805406A
Application number: US00177624A
Authority: US
Inventors: A Castonoli
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-09-03
Filing date: 1971-09-03
Publication date: 1974-04-23
Anticipated expiration: 1991-04-23

Abstract

Apparatus for treating a material by indirect heat exchange in which the material is divided into two substantially equal amounts which pass through the apparatus in interchangeable paths. The apparatus includes a centrally disposed hollow conveyor screw which is positioned within a stationary inner heat exchange jacket to constitute an inner material flow path. A rotating drum which is disposed annularly around the inner heat exchange jacket and which has with an outer heat exchange jacket, constitutes an outer flow path for the material. At several points along the length of the apparatus provision is made to discharge the material from the inner flow path through a hole in the inner heat exchange jacket into the rotating drum and to allow the material initially in the outer flow path to fall through an opening in the inner heat exchange jacket into the inner flow path. Breaker means adjacent the inlet to the inner flow path prevent caking of wet material. The breaker means are disposed around the conveyor shaft and are acutated by a planetary gear arrangement. The apparatus has particular utility for the drying of wet coal since the coal is maintained out of direct contact with the heating fluid so that coal dust does not exhaust to the atomsphere, and the drying may be carried out under vacuum.

Description

United States Patent 91 Castonoli Apr. 23, 1974 INTERCHANGEABLE PATH DRYING APPARATUS Alder F. Castonoli, 1424 Fifteenth St., Huntington, W. Va. 25701 [22] Filed: Sept. 3, 1971 [21] Appl. No.: 177,624

[76] Inventor:

[52] US. Cl 34/109, 34/128, 34/142,

Primary Examiner-Albert W. Davis, Jr. Attorney, Agent, or Firm-Laurence, Laurence &

Neilan WET MATERIAL [5 7] ABSTRACT Apparatus for treating a material by indirect heat ex change in which the material is divided into two substantially equal amounts which pass through the apparatus in interchangeable paths. The apparatus includes a centrally disposed hollow conveyor screw which is positioned within a stationary inner heat exchange jacket to constitute an inner material flow path. A rotating drum which is disposed annularly around the inner heat exchange jacket and which has with an outer heat exchange jacket, constitutes an outer flow path for the material. At several points along the length of the apparatus provision is made to discharge the material from the inner flow path through a hole in the inner heat exchange jacket into the rotating drum and to allow the materialinitially in the outer flow path to fall through an opening in the inner heat exchange jacket into the inner flow path. Breaker means adjacent the inlet to the inner flow path prevent caking of wet material. The breaker means are disposed around the conveyor shaft and are acutated by a planetary gear arrangement. The apparatus has particular utility for the drying of wet coal since the coal is maintained out of direct contact with the heating fluid so that coal dust does not exhaust to the atomsphere, and the drying may be carried out under vacuum.

10 Claims, 6 Drawing Figures DRY COAL SHEHF 1 M 3 58s 8 L g i EEmEE E3 minnow mar:

' INVENTOR ALDER F. CA STANOLI STEPNO und NEILAN ATTORNEYS MEI H'EH 2* 11PM 2mm 3 @E 3:

FIG 4 INVENTOR ALDER F. CASTANO Ll STEPNO o'nd NEILANV ATTORNEYS INTERCHANGEABLE PATH DRYING APPARATUS The present invention relates to apparatus for subjecting material to indirect heat exchange and more particularly to apparatus which is adapted for drying the material being treated. The apparatus is characterized by having inner and outer material flow paths with the material in the respective paths interchanging from one path to another at spaced points along the length of the apparatus.

While the apparatus of the invention has many applications, for example, in food processing, desalination of water to obtain pure water, and/or salt or bittern of any gravity for further treatment to produce magnesium chloride, etc., and for cooling and drying of various particulate materials; the apparatus has special utility in the drying of wet coal. Thus, for purposes of illustration only, this specification will describe the apparatus as utilized in the drying of wet coal.

As is well known, it is frequently necessary to dry wet coal. Heretofore, 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 that at atmospheric pressure and in addition the chance of fire or scorching of the material being dried is minimized. In accordance with the instant invention, drying takes place considerably below the customarily l,OF. of 7 prior art processes.

It is a primary object of the present invention to provide improved apparatus for effecting heat exchange between a material and a heat exchange fluid by in'direct heat exchange.

Another object of the present invention is to provide an improved particulate material treating apparatus having a plurality of flow paths through the apparatus and with the material interchanging from one flow path to another at selected points along the length of the ap paratus.

A further object of this 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 dust.

Still another object of the present invention is to provide improved material treating apparatus having novel means for preventing caking of wet material being transported by a conveyor screw.

The above and other objects, features and advantages of this invention will become more apparent as this description proceeds.

In accordance with a presently preferred embodiment of the invention, wet coal is fed into one end of the apparatus by a centrally disposed conveyor screw having a hollow shaft and hollow screw flights through which a heat exchange medium may be passed. A portion of the material being treated falls through an opening in the casing surrounding the screw conveyor and drops into a rotating drum which is disposed annularly around the screw conveyor casing. The remainder of the material continues to be conveyed by the screw conveyor through the casing which is surrounded by an inner heat exchange jacket. The rotating annular drum is also provided with a heat exchange jacket. At the end of the first section of the casing, the material being transported by the screw conveyor falls down a chute into the annular drum while at the same time the material previously being treated in the annular drum is picked up by a bucket assembly and discharged into an opening in the inner casing so that this material is transported by the screw conveyor through the next casing section. In this fashion the material initially in the rotating drum in the first section of the apparatus interchanges its path with the material initially being conveyed through the inner casing. Preferably this interchange of paths is repeated several times along the length of the apparatus to insure a more uniform treatment of the material. Spaced exhaust pipes are provided in the jacket around the annular drum in order to exhaust vapor emanating from the coal being dried into stationary annular headers which are disposed around the drum. The headers are connected to a vacuum source so that the drying may be carried out at reduced pressures and hence at lower temperatures in order to eliminate or minimize the possibility of fire or explosion. The dried coal discharges from the discharge end of the apparatus, and the now cooled heat exchange medium is separately removed from the apparatus and may be vented to the atmosphere after additional heat recovery treatment if desired.

In the drawings:

FIG. 1 is a view taken primarily in longitudinal, vertical cross section of a presently preferred embodiment of the invention.

FIG. 2 is a longitudinal cross sectional view of a portion of the apparatus on an enlarged scale showing planetary gear actuated breaker means for preventing caking of material in the apparatus.

FIG. 3 is a transverse vertical cross sectional view taken along the line 3-3 of FIG. 1.

FIG. 4 is a transverse vertical cross sectional view taken on the line 44 of FIG. 1.

FIG. 5 is a transverse vertical cross sectional view taken on theline 5-5 of FIG. 1.

FIG. 6 is a view of a portion of the jacketed inner casing illustrating the arrangement for flow of material both out of and into the inner casing whereby the streams of material interchange flow paths.

Referring now to the drawings and more particularly to FIG. 1, wet coal or other material to be treated enters the apparatus at a regulated rate through inletpipe 10 in which there are a pair of star valves 12. The lower end of pipe 10 passes through a stationary housing 14 and discharges the coal into a longitudinally extending casing 16. A hollow screw conveyor 18 extends the length of the casing 16. Rotation of the screw conveyor by motor 20, speed reducer 22 and shaft 24 causes the material from the inlet pipe 10 to be conveyed through casing 16.

After traversing the first portion of casing 16, some of the coal falls through an opening 26 in the bottom of the casing into a rotating drum 28 which is surrounded by an outer heat exchange jacket 30. The opening 26 is of a size such that approximately one-half of the incoming coal falls into the drum, i.e.. the amount of coal which continues to be conveyed along by the screw conveyor beyond the opening 26 is approximately the same as the amount of coal which falls into the rotating drum 28.

Referring now to FIG. 2, breaker means are provided to prevent caking of the wet coal adjacent the inlet end of casing 16. The breaker means comprise a plurality of paddles 32 on rotating rods 34 which extend through bearings provided in holes in the hollow screw flights of conveyor 18. The rods 34 are rotated by a planetary gear arrangement which comprises an annular stationary sun gear 36 which is disposed coaxially around shaft 24 and is connected to the stationary casing 16 and a plurality of planetary gears 38 fixed to the ends of rods 34. The rotation of the paddles 32 about the axes of rods 34 combined with the movement caused by rotation of the rods 34 due to rotation of the screw conveyor breaks up and prevents an accumulation of wet coal which might form within the casing 16. While for some installations such breaker means may be provided throughout the entire apparatus, in general, the breaker means are necessary only at the inlet end of the casing 16 where the material being treated is wet.

Hot furnace gas or other suitable heat exchange medium enters the apparatus through inlet duct 40 in which there is a thermostatically controlled damper 42. The furnace gas moves in the direction of the arrows into housing 14 where the gas flow divides with a portion of the furnace gas entering the hollow shaft 44 of the screw conveyor and the hollow screw flights. Part of the remaining furnace gas flows to the right hand end of housing 14 through openings 46 into the outer heat exchange jacket 30. The remaining furnace gas flows from the upper section of the annulus between casing 16 and housing 14 into an annular inner heat exchange jacket 27 which is supported upon the casing 16. The heat of the furnace gas in inner jacket 27 and in outer jacket 30 are utilized to dry the wet coal during its passage through the apparatus as will be explained more fully hereinafter.

The rotating drum 28 and the outer heat exchange jacket 30 are rigidly connected to one another by spaced support members 48 or other suitable means. The lower, outer surface of jacket 30 is rotatably supported upon two pairs of roller bearings 50 which are mounted on supports 52 as best seen in FIGS. 1 and 4. Rotation is imparted to drum 28 and the outer jacket 30 by means of a driven gear 54 which is driven by a suitable means (not shown) which is in meshed engage ment with a ring gear 56 fixed to the left hand end of jacket 30 so that the outer, jacket and the drum 28 are caused to rotate about casing 16. The drum 28 has internally projecting hollow conveyor blades 58 which preferably have a slight helical twist to cause the coal to be conveyed through the drum. A slight downward inclination of the rotating drum will also cause such movement of the coal longitudinally within the drum.

At several points along the length of the apparatus the coal within the casing 16 changes places with the coal in the drum 28. For purposes of illustration only,

three such interchanges are illustrated in FIG. 1. The coal which has passed through the initial section of the casing 16 falls through an opening 60 in the lower section of casing 16 down a chute 62 into the rotating drum 28. At the same time, the coal which was initially in the rotating drum is picked up by a series of scoops 64 attached to a ring 66 which is integrally connected to the rotating drum 28 as best seen in FIG. 3. The scoops pick up the coal in the bottom region of the drum. When the scoops reach the upper region of the drum, the scoops due to their configuration are tilted so that the coal falls out of the scoops and through an inlet passage 68 in the inner heat exchange jacket 27 into the casing 16. The coal which falls through the inlet passage 68 is then transported by the conveyor screw 18 through the next section of the casing 16 to the next place where the material flow streams interchange, i.e., the next opening 60, inlet passage 68 and associated structure.

In order to preclude mixing of the coal streams in the regions of the path interchange, the opening 60 in the bottom of the casing 16 is spaced slightly upstream of the adjacent ring 66 and associated scoops 64. Since the opening 60 and the inlet passage 68 are offset in a longitudinal direction, the coal which falls out of scoops 64 into the casing 16 cannot fall out of the casing 16 through the associated opening 60. In order to prevent a portion of the coal which falls through the opening 60 in the bottom of the casing from immediately being picked up by the scoops 64 and returned to the inner casing rather than flow through the drum 28; the bottom end of chute 62 projects into the annular ring 66 above the position of the scoops at the bottom of the apparatus. In this fashion the coal falling down chute 62 falls into the drum 28 downstream of the point that the coal is picked up by the scoops 64.

In the illustrated embodiment there are four annular rings 66 and associated scoops. At the first three rings there are interchanges of the coal flow paths. The fourth ring, i.e., the one at the right hand side of the apparatus as seen in FIG. 1 there is no opening 60 or chute 62. Thus, the dried coal in this section of casing 16 remains in the casing and is united with the dried coal picked up by the scope of the fourth ring 66 which falls through the passage 68. The combined coal streams are now conveyed by the conveyor 18 to the discharge end of the apparatus and out through a discharge conduit 70 in which there are a pair of star valves 72 to a suitable conveyor for transporting the dried coal to a point of use or storage. At the discharge end of the apparatus the expended heat exchange gas from the inner heat exchange jacket 27 flow into an annular header 74 to merge with the expended heat exchange gas coming from the outer heat exchange jacket 30 through discharge apertures 76. The combined heat exchange gasses then enter duct 78 for discharge either to the atmosphere or for further heat recovery from these gasses.

As the wet coal is heated by indirect heat exchange, water vapor emanates from the coal. Water vapor from the coal within casing 16 escapes from the casing through a plurality of small diameter tubes 80 which are disposed at spaced intervals along the length of the apparatus and form openings from within the casing 16 communicating with the interior of the rotating drum 28. Within drum 28 water vapor coming from either casing 16 or from the coal drying in the rotating drum 28 flows around the heads of slidable valves 84 into vent pipes 82 which extend through the outer heat exchange jacket 30 into stationary annular headers 86. As best seen in FIG. 5, the valves 84 have enlarged heads 88 which entirely cover the openings to pipes 82 while in the lower sector of the arc of rotation of the drum so that coal does not enter the pipes. At each valve 84 in turn moves upwardly above the horizontal center line of the drum, the valve begins to slide so that the valve head 88 moves downwardly until the abutment member 90 which may be in the form of a cross or the like contacts the outsideperiphery of heat exchange jacket 30. In this position vapors may flow behind valve heads 88 into pipes 82 and into the respective annular header. From the annular headers '86 the vapors flow upwardly through conduits 92 into collection conduit 94 and then into a conduit 96 which leads to a suitable source of vacuum (not shown).

In the foregoing description a presently preferred embodiment of the invention has been shown and described with particularity. However, 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 encompass all such changes and modifications as fall within the scope and spirit of the appended claims.

What is claimed is:

1. Apparatus for subjecting a material to indirect heat exchange comprising an inner casing, an inner heat exchange jacket disposed around said casing, a screw conveyor disposed within said casing, means for introducing a material to be treated into an annulus provided between the screw conveyor and said casing, an annular drum mounted coaxially with said casing and disposed to rotate relative to said casing, means for subjecting material within said drum to indirect heat exchange, drive means for rotating said drum, said casing being provided with an opening to enable a portion of the material to flow through said casing into said drum, at least one group of scoops rigidly connected to said drum around the periphery thereof at at least one point along the length of the apparatus to lift up material from within the rotating drum and to deposit the material through an aperture provided at the top of said casing whereby this material is subsequently carried along within said casing by said screw conveyor, said casing being provided with a discharge opening at the bottom thereof and a communicating chute to enable material initially in said casing to pass beyond said plurality of scoops into said drum, means to collect vapors emanating from the material being treated, and means to discharge treated material from the apparatus.

2. Apparatus according to claim 1, further comprising breaker means provided adjacent the inlet end of said inner casing and including a plurality of longitudinally extending rotatable rods disposed in the annulus between the shaft of said screw conveyor and the inner surface of said casing, and planetary gear means for rotating said rods. r

3. Apparatus according to claim 2, further comprising a plurality of paddle members attached to said rods, and said planetary gear means including an annular sta tionary sun gear, and a plurality of planetary gears rotating about said sun gear and connected to the ends of said rods.

4. Apparatus according to claim 1, further comprising at least one annular ring member secured to the inner periphery of said drum, said scoops being connected to said ring member, and hollow conveyor flights provided in the inner periphery of said drum.

5. Apparatus according to claim 1, wherein said screw conveyor has a hollow shaft and hollow screw flights, and means to introduce a heat exchange medium into said shaft and said screw flights.

6. Apparatus according to claim 1, wherein said means for subjecting material within said drum to indirect heat exchange comprises an outer heat exchange jacket integrally connected to said drum.

7. Apparatus according to claim 6, further comprising bearing support members supporting the lower surface of said outer heat exchange jacket, and wherein said drive means include a ring gear operatively connected to said drum and a drive gear in toothed engagement with said ring gear.

8. Apparatus according to claim 7, further comprising a plurality of small diameter vapor vents extending through said inner heat exchange jacket to enable vapors emanating from the material in said casing to pass into said drum.

9. Apparatus according to claiml'8, further comprising a plurality of valved vapor vent passages provided extending through said outer heat. exchange jacket to enable flow of vapors from within said drum into a stationary annular header provided around said outer heat exchange jacket, a source of vacuum, and conduit means to connect said vacuum source to said annular header.

10. Apparatus according to claim 9, further comprising means to supply a heat exchange gas into said inner and outer heat exchange jackets.

Claims

2. Apparatus according to claim 1, further comprising breaker means provided adjacent the inlet end of said inner casing and including a plurality of longitudinally extending rotatable rods disposed in the annulus between the shaft of said screw conveyor and the inner surface of said casing, and planetary gear means for rotating said rods.

3. Apparatus according to claim 2, further comprising a plurality of paddle members attached to said rods, and said planetary gear means including an annular stationary sun gear, and a plurality of planetary gears rotating about said sun gear and connected to the ends of said rods.

9. Apparatus according to claim 8, further comprising a plurality of valved vapor vent passages provided extending through said outer heat exchange jacket to enable flow of vapors from within said drum into a stationary annular header provided around said outer heat exchange jacket, a source of vacuum, and conduit means to connect said vacuum source to said annular header.