US2134229A - Apparatus for drying vegetable fiber such as bagasse and the like - Google Patents

Description

Oct. 25, 1938. G, J, UPSCOMB 2,134,229

APPARATUS FOR DRYING VEGETABLE FIBER SUCH AS BAGASSE AND THE LIKE Filed Oct. 20, 1934 [via MW Patented Oct. 25, 1938 UNITED STATES PATENT OFFICE APPARATUS FOR DRYING,VEGETABLE FI- BER- SUCH AS BAGASSE AND THE LIKE Gaston J. Lipscomb, Montclair, N. J. Application October 20, 1934, Serial No. 749,258

1 Claim.

The present invention relates to the apparatus for drying vegetable fiber such as bagasse, and aims generally to improve existing methods and apparatus for that purpose.

More particularly, the present invention aims to improve the method and apparatus for drying vegetable fiber as is disclosed in my copending application Serial No. 738,112, filed August 2, 1934, by providing a new method and apparatus which will substantially dry bagasse to a dryness of approximately 7% in a minimum of time and under materially reduced fire hazards.

One of the principal aims and objects of the invention is to provide an improved method and apparatus for drying ,bagasse which will give As in the case of my prior application Serial No. 738,112, above referred to, the wet bagasse containing from to .of moisture, is delivered to a drier casing through which hot air is circulated, the bagasse being fed to successive tiers during its progress through the drier casing. According to the present invention, the wet bagasse is delivered to a feeding box, I 0, which may be a circular sheet mounted above the drier casing I3. Rotatably mounted with the feeding box It is a vertical shaft I4 carrying a feeding cone l5 upon which the bagasse is delivered from a plurality of feed spouts It on either side of' the feed cone so as to more uniformly distribute the bagasse upon the rotating'feed cone. The feed cone may carry a plurality of radially disposed rabble arms for spreading the bagasse into the openings of a stationary distributing plate l8. Mounted immediately below and closely adjacent to the plate l8-is an adjustable plate I! having openings corresponding to the openings in. the distributing plate, the plate I! being adjustable around the shaft I! so that it may-be adjusted with reference to the plate It and thus vary the size, of the openings in the distributing plate I l to variably control the feeding of bagasse into the drier. v I i Below the distributing plate I. is a plurality of drying tiers 20 similar to those of my copending application, each tier comprising alternate reticulated sections 2| and open spaces 22, the reticulated sections of each tier being immediately below an open space in the tier above it 5 so that as the bagasse is brushed off the section 2| of one tier by a rotating rabble arm 23, it will be brushed into an adjacent opening 22 and fall directly upon a reticulated support 22 below. The number and size of the tiers, as well as the number of rabble arms for each tier will, of course, vary according to the capacity of the plant and the degree of dryness to be desired.

According to the present invention, the drying is effected by moving the wet bagasse for a sub- 15 stantial distance in a current of very hot air or flue gas, preferably at a temperature of about 800 to 1000 F. to extract a substantial amount of moisture from the material and then com-- pleting the drying of the bagasse-by moving it in 2 a counter-current of hot air at a temperature of between 250. and 400 F.

The hot flue gases and heated air may be supplied from a suitable source, as for example, a Dutch oven 25 having a cook's furnace 26 adapted to burn a.quantity of bagasse which advantageously may be a percentage of the bagasse dried in the drier. The cook's furnace of the oven 25 may be supplied with a forced draft-in the usual manner anda secondary combustion chamber 21 as is usual. The products of combustion of the furnace are advantageously divided and may be variably controlled as by damper 21*, a major portion of the gas being passed through flue 28 to an annular air inlet 29 surrounding the feed box I II and directed inwardly-to the'interior of the feed box, by means of radial openings or nozzles 20 so that the applicatiomof the hot flue gases to the wet bagasse will be as uniform as possible circumferentially of the drier.

The balance-of the products of combustion 3g; from the Dutch oven are passed through'a heat exchanger 3] which may advantageously be of any suitable design by means of which air, culated by fanJ-2 may be heated to a suitable 45 degree, the flow of.flue gases through theflieat exchanger II, and hence the temperature of air heated thereby, being controlled by valve 33.

The air heated by the heat exchanger" passes through conduit 34 to an annular hotair inlet 5o 35 surroundingthe drier casing 12 at its lower end, the hot air being admitted to the interior of the casing II by means of openings or nozzles 36 so that the appllcationof heated air tothebagasewlllbeuniformcircumferentiauyu' pressure from the plunger 43.

of the drier. Obviously the temperature of the hot flue gases entering the feed box III may be variably controlled by suitable means, as for example, a damper regulating the admission of air to the secondary combustion chamber 21 of the oven 26.

A fan- 38 is preferably provided to draw off the dust and moisture laden air and gases from the drier casing and preferably this fan is connected to the casing intermediate the flue gas inlet at the upper end of the drier and the hot air inlet and the lower end of the drier. Preferably the exhaust fan 38 is connected to the drier by means of an annular outlet or exhaust chamber 39, and the fan advantageously delivers the dust laden air and gases to a suitable dust collector which may be of the cyclone type. The fan 38 is of sufficient capacity as to produce a negative pressure with the casing I3.

It is important that the drying take place within an enclosed chamber and in the absence of air, except the hot air and gases which are circulated through the drier, and hence it is advantageous to provide an air lock both at the feeding and discharge end of the. drier. This may be satisfactorily accomplished by means of the star wheel mechanism disclosed in my copending application, but in connection with the discharge I find the more satisfactory air lock is obtained according to the present invention.

Accordingly, the lower end of the casing l3 may comprise downwardly and inwardly inclined walls-forming a discharge cone 4|, the cone terminating at its lower end in a horizontal tube 42. The lower end of the shaft may be provided with a stirrer or scraper 43 to prevent bridging of the dried bagasse in the cone, and to permit a normal flow of dried material to the tube 42. A plunger 44 reciprocated by any suitable means, as for example, a crank 45 and connecting rod 46 is mounted within the tube to discharge the bagasse from the discharge cone 4|, the number of strokes of the plunger 44 as well as the diameter of the tube 42 being proportioned and designed so as to progressively discharge bagasse in accordance with the capacity of the drier and the rate of feeding material to the feed box II).

In order to provide an air lock against the admission of atmospheric air into the drier at the discharge cone, the tube 42 preferably terminates in reduced discharge tube 41 effective to retard the flow of dried bagasse except under The cooperating action of the plunger 43 and the reduced discharge tube efiect a compacting. of the bagasse fibers in the discharge tube effective to seal the tube 45 against the entrance of air and also to deliver the dried bagasse in partially compressed batches, which are more advantageously baled in baling presses than when. the material is loose and flocculent;

The shaft I 4 advantageously extends longitudinally of the full height of the drier and may be advantageously driven by suitable speed reduction gearing 48 at the upper end.

Advantages of my present invention over the method and apparatus disclosed in my copending application Serial No. 738,112 are that a more complete dryingv of the bagasse may be effected in a shorter time and hence the capacity of the drier may be increased without serious liability to fires occuring in the drier. By first subjecting the wet bagasse to the hot flue gases which may be as hot as 800 to 1000 F. to partially dry them, and -then finally drying the bagasse in a current of air at from 250 to 400 F.,

' I am able to dry bagasse to a high degree of dryness (with a moisture content as low as 7%) in a relatively shorter time than was possible with the method disclosed .in my copending application. For example, the drying may be completed according to the present invention, in 15 minutes, and preferably the exhaust or discharge outlet 39 isso located that bagasse is subjected to the hot flue gases for 60% of the drying time, and to the counter flow ofhot air for approximately of the drying time. This I find is an extremely efiicient drying method and enables me to reduce the number of drying tiers I .over my prior method.

I claim:

Apparatus for drying loose vegetable fibers such as bagasse, comprising a closed vertical casing, a vertical shaft rotatably mounted in said casing, a conical distributor connected to the upper end of the shaft, means for introducing fibers into the casing and upon said distributor, a plurality of reticulated tiers spaced throughout the length of the casing, means for progressively conveying the fiber material from one tier to the next lower tier, an auxiliary furnace, means for conveying hot flue gasesof approximately 750 F. from said furnace and introducing them into the top of said chamber in contact with the fibrous material, a heat exchanger heated by said furnace, means for circulating drying air through said heat exchanger and induring the first operation of drying period, and

a current of cooler drying air moving in a counter direction to the movement of the fibrous material during the latter portion of the drying period.

GASTON J. LIPSCOMIB.

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