US1766843A - Drying of moist material - Google Patents

Description

June 24, 1930. o, so R u El AL 1,766,843

DRYING OF MOIST MATERIAL Original Filedbct. s. 1927 g "a I O 1 1.- f E Y P 9? \h I 00000 f i 1 o z y j 1 b b b Patented June 24, 1930 UNITED STATES PATEN oLor SGDERLUND AND rnomas exam, or LoNno ENGLAND, AssIeNoBs 'ro 'rncHNo- CHEMICAL LABORATORIES, LIMITED, or LoNnoN, ENGLAND DRYING or moIsr MATERIAL Original application filed October 3, 1927, Serial No. 223,750, and in Great Britain October 7, 1926. Divided and thisapplication filed October 11, 1929. Seral No. 899,013.

This application is a continuation in part of our applications Serial No. 223,750 hlcd 3d October, 1927, and Serial No. 272,264,

filed 23d April, 1928.

This invention relates to the drying of materials while suspended in and carried by a gaseous medium adjacent to heated surfaces.

In such arrangements it has been proposed to blow air through one or more tubes which are situated in the region of a furnace and its adjacent flues' or passages for the products of combustion, while disintegrated material which is to be dried. is fed into the stream of air at the highest temperature region, the whole passing therefrom into a drying chamber.

pension The object of the present invention is to provide for the drying-of certain-substances such as coal dust, peat, lignite, brewers grain, grass or fodder crops or other materials having small particles or particles with at least one small dimension at a rea-' sonable speed "and by the use of comparatively small quantities of heat at a moderate temperature.

The present invention consists in a method of dr ing material While carried in susby a gaseous medium through -one or more conduits having heated walls according to which the carrying medium fully charged with the material is spread laterally to extended form preferably while moving in an upward direction to secure uni The invention further consists in a method according to the preceding paragraph in which spreading is effected as by changing the conduit section from one large passage to a plurality of small tubes or passages of other form presenting large wall contour in relation to cross-sectional area of long tubes or one or more flat narrow conduits of considerable length disposed in a tortuous and preferably'up-an'd-down direction.

The invention further consists in a method in accordance with any of the preceding paragraphs in which-a liquid and/or the substantially saturated vapour thereofas for example Water and steam are employed to heat the walls of the drying conduits.

The invention also consists in improvements in the drying of moist materiaP as hereinafterdescribed.

F igure 1 shows apparatus for operating in accordance with the invention, thedrawmg representing only the two ends of the apparatus which will be of any desirable iength for performing the necessary funcions; Figure 2 is a plan view showing the heatmg vessel and arrangement of tubes therein. In the apparatus for carrying the method into efiect illustrated by way of example a cylindrical chamber a is fitted with tube plates a a at the top and bottom and filled with groupsof vertical tubes which are of smallvdiameter inorder that none'of the material may be far from the surrounding heated wall of the drying conduit and a large contour of wall surface may be presented for a of conduit. f the six groups b, If, b", I) and b the combined cross section of any two similar groups constitute the area of thedrying conduit and the groups are connected to one another by the common headers d'-', d at the bottom and by individual return bends d, d at the top.

The conduit 9 is fitted with a charging device 6 having a hopper e and a distributor e for introducing the material of the kind indicated and which may be disintegrated into the carrying medium and the bend (Z forms the inlet to the large wall surface drying conduit formed b the tube groups. The outlet d from t e last two groups is taken to the inlet 7 of the cyclone f which is provided with the discharge f at the bottom for the dried material.

The outlet f from the cyclone is connected ably disposed of.

'- materialpossible for its velocity and upon entering the drier from the bend d the ma-.

Heat is supplied to the tubes by means of a heating fluid, for instance hot water or condensing steam, which is admitted by the pipe a and flows inside the chamber a betweenthe tubes while the condensate leaves by the pipe 0 Steam previousl put to other uses forms an economical heating medium which is particularly suited for operating in accordance with the present method and the heating of the drying conduit is substantially uniform and is as shown carried as near as practicable to the point Where the material is separated from the carrying medium to prevent condensation of the vapour permeating the medium on the material as according to the invention the carrying medium only transmits heat the very short distance from the walls' to the material which is all closely adjacent thereto and there is practically no storing of heat in the carrying medium to be imparted to material which it may subsequently meet.

A carrying medium such as air is drawn into the apparatus through the pipe g, the uantity being controlled by a damper (not s own) at any convenient position and the velocity being sufiicient to carry the material which is to be dried. The material in regulated proportion to the air is added at the charging device 0.

The air and material are so proportioned that the air carries the maximum amount'of terial-laden air is spread out so as to contact with an extended contour of wall surface for example as shown by being divided up into a large number of small diameter tubes.

The spreading laterally of the materialladen air 'from compact to attenuated, dispersed, se arated or other extended crosssectional orm takes place at the bottoms of the extended contour regions or lengths of tubes and this is essential to ensure uniform distribution which is thus accomplished owin to the fact that if the material tends to cofiect together to a greater extent in one section than another of the total conduit area the velocity of the air will be checked in this section and, therefore, more air will tend to pass through other sections withthe result that a greater amount of material will be carried to the other sections and uniformity of distribution will beuautomatically maintained.

The material-laden air passes by way of the plurality of tubes forming the total area of the drying conduit and at the top one set of tubes 1) is returned in one direction and the other set of tubes 5 in the other direction, each tube being here provided with an Individual bend so that all the material that passes up 'a tube must return down the continuation of the same tube and no variation of the distribution can occur due to y the downward movement.

At the bottoms of the tubes 12' b all of the material-laden air enters a common return bend d or d and when returning in the upward direction the material-laden air is a ain spread out or divided into a plurality of small tubes at the bottoms of the groups and 11 The tube. groups will be of considerable length, portions only at each end being shown in the drawing.

In Figure 2 the arrangement of the groups of tubes is indicated but the em- -ployment of a plurality of tubes is not essential and each row or line of tubes may be replaced by a narrow conduit of a width corresponding with the length of the row, the conduit being divided into parallel compartments by ribs or divisions if desired.

Any other arrangement adapted to provide a considerable length of wall contour or perimeter in relation to the cross-sectional area of the drying conduit or passage may also be employed if desired.

In the event of the design leading to an inconvenient length of the tubes or to the gases having to How upwards and downwards an excessive number of times, the flow may be modified so that the gases, after passing through one upward and downward group of tubes, are again directed by a fan through the same group by suitable pipes and return bends.

The apparatus illustrated provides a substantially uniform wall temperature throughout the drying conduit and heating medium of an inexpensive na re is conveniently employed therein. Tl wall temperature may, however, be progressively increased along the conduit with advantage as by counterflow if convenient.

Having now described our invention, what we claim as new and desire to secure by Letters Patent is 1.-The method of evaporating moisturefrom divided material comprising charging material in particles having at least one small dimension into a compact moving stream of gaseous carrying medium, increasing the length of the wall perimeter of thecross section of said stream without sub-:

finally separating the material from the stream of medium.

2. The method of evaporating moisture from divided material comprising charging material in particles having at least one small dimension into a compact moving stream of air, upwardly directing and attenuating said stream without substantially altering the cross-sectional area thereof, conducting said stream a considerable distance in an attenuated condition while heating the containin walls and finally separating ile material rom thestream.

3. The method of evaporating moisture from divided material comprising charging material in particles into a compact ovi stream of gaseous carrying medium, divi if ing said stream into a pluralit of smaller streams, conducting said plura 'ty of small streams a considerable distance while heating the walls confining the same, reuniting said small streams and finall separatingthe material from the stream 0 medium.

4. The method of evaporating moisture from divided material comprising charging material in particles into a compact moving stream o air, dividing said stream into a plurality of smaller streams while up-- wardl directing the same, conducting said plura ity of small streams a considerable distance while heating the walls confinin the same, reuniting said small streams and finally separating the material from the stream. v p

5. The method of evaporating moisture from divided material comprising chargingmaterial in particles into a com act movin stream of gaseous carrying me um, divi ing said stream into a plurality of smaller streams while upwardly directing the same, conducting said plurality of small streams a considerable distance in an upward and downward direction while moderately heating the walls confining the same, reuniting said small streams and finall separating the material from the stream 0 medium.

6. The method of evaporating moisture from divided material comprising charging material in'particles into a compact moving stream of air, dividing said stream -into a plurality of smaller streams while uipwardl directing the same, conducting sai plura ity of small streams a considerable dlstance in an upward and downward direction while heating the walls confining the same with hot water or the vapour thereof, reuniting said small streams and finally separating the material from the stream.

7. The method of rapidly drying divided material at comparatively low temperatures comprising charging material in particles having at least one small dimension into a compact moving stream of gaseous carrying medium, increasing the length of the wall ing said charged stream, conducting said stream a considerable distance upward and then downward in regions ofsimilar perimeter, altering the increased perimeter con ditions and reinstating them whilethe stream. is again directed upwards, heating the walls of all the increased perimeter regions with hot aqueous material and finally separating the material from the, stream of medium.

8. The method of rapidl drying divided materlal at. comparatively ow temperatures comprising charging material in particles havlng at least one small dimension into a compact moving stream of gaseous carrying medium, dividmg said stream into a plurality of smaller streams while u wardl directing the same, conducting sai plura ity of small streams a considerable distance upwards and then downwards without substantial alteration of cross section, reuniting a number of said streams and again separating them while moving upwards, heatin the walls confining the small streams with ot aqueous mater1al, reuniting said small streams and finally separating the material' from the stream of medium.

In testimony whereof we have signed our names to this specification.

OLOF SODERLUND. THOMAS GRAM- perimeter of the cross section of said stream 7 without substantially altering the cross-sectional area thereof while upwardly direct-

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