US2075506A - Drying apparatus - Google Patents

Description

March 30, 1937. J. CRITES ET AL DRYING APPARATUS Filed June 15, 1935 3 Sheets-Sheet l March 30, 1937. c ns ET AL 2,075,506

DRYING APPARATUS Filed June 15, 1955 3 Sheets-Sheet 2 Ira/enfdiu and 4700 7155 March 30, 1937. J c ans 2,075,506

DRYING APPARATUS Filed June 13, 1955 s Sheets-Sheet 5 i atenteri Mar. 30, 1937 2,075,506 DRYING APPARATUS Joe Crites, Evanston, and Richard F. OMara,

Chicago, Ill.,

assignors to The Raymond Brothers Impact Pulverizer Company, Chicago, 111., a corporation of Illinois Application June 13, 1935, Serial No. 26,423

2 Claims.

This invention relates to certain new and useful improvements in a drying apparatus, more particularly to an improved apparatus for efficiently disintegrating and removing water from materials of initially high moisture content.

A great variety of wet materials may be dried by means of this improved apparatus, for example, it may be used for treating sludge, that is the semi-fluid material which remains after sewage has been screened and filtered. This sludge may have a very high moisture content, for example, about 65% to 80% by weight. Before being introduced into the drying apparatus hereinafter described, the percentage of moisture in such a material is preferably reduced by mixing with the material a desired proportion of previously dried and pulverized or disintegrated material so that the resulting mixture (while still being very wet) is such that it may be handled in the apparatus without clogging the mechanism. The resultant mixture contains various grades of wet material, some parts being very finely divided or pulverized while other portions are larger and heavier and contain a greater percentage of unexposed moisture. In other words, the material to be handled by this improved apparatus is usually a conglomerate of smaller and larger particles, all in an extremely wet condition.

Briefly described, the apparatus comprises a plurality or series of drying units through which a hot air or gas stream of initially very high temperature is successively passed. The moisture from the material is taken up by the hot gas stream, the temperature of the gas stream'being thereby lowered as it advances through the driers. The material to be dried is introduced into the first drier and is advanced through the driers mainly by the force of the gas stream. It will be apparent that the smaller and lighter materials will be advanced more rapidly and the larger and heavier particles, which are more diflicult to dry, will be advanced more slowly until they are broken up so as to be more eiTectively dried. The F main drying element is a mill or disintegrator wherein the material is, for the most part, reduced to a very finely divided condition. The initial temperature of the gas stream is preferably quite high, higher than can be used in the mill without injury to the apparatus, but before reaching this disintegrator the material and gases are passed through one or more preliminary drying units, here shown as a drying tower and a rather long horizontal drying conduit, in which preliminary drying steps or stages are carried out and the temperature of the gas stream is reduced to such a degree that it may be safely introduced into the mill. After leaving the disintegrator the material and gas stream is passed through a second long horizontal drying conduit and subjected to a final drying operation. The complete drying apparatus used in any particular situation may consist of any one or more or all of the drying units hereinabove briefly described, as the nature of the material being handled may require.

The principal object of this invention is to provide an improved drying apparatus of the type briefly described hereinabove and disclosed more in detail in the specifications which follow.

Another object is to provide a drying apparatus of this type in which hot gases are held in intimate contact with the materials throughout the disintegrating and drying processes.

Another object is to provide an improved form' of disintegrating apparatus.

Another object is to provide an improved form of drying conduit.

Another object is to provide a drying apparatus in which the materials are advanced almost entirely by the force of the heated gas stream.

Another object is to provide a drying apparatus in which very highly heated gases may be used without injury to the disintegrating mechanism.

Another object is to provide a drying apparatus including improved means for distributing or spreading the material so as to provide more intimate contact with the heated gases. Other objects and advantages of this invention will be more apparent from the following detailed description of certain approved forms of mechanism constructed and operating according to the principles of this invention.

In the accompanying drawings:

Fig. 1 is a side elevation of the drying assembly, partially broken away and partially in central vertical section.

Fig. 2 is a top or plan view of the right hand portion of the mechanism shown in Fig. 1.

Fig. 3 is an end view looking from the left at Fig. 1, with portions of the apparatus broken away.

Fig. 4 is an end view looking from the right at Figs. 1 and 2, but showing a different form of discharge opening from the disintegrator.

Fig. 5 is a longitudinal vertical section, taken substantially on the line 5-5 of Fig. 2 but on a larger scale.

Fig. 6 is a transverse vertical section taken substantially on the line 6-6 of Fig. 5.

The assembly consists in general of a drying tower A into which the hot gas stream and the materials to be dried are first introduced, a long horizontal drying conduit B, through which the material is rather slowly advanced, the disintegrator C, and the horizontal discharge conduit D in which the final drying operation takes place.

The drying tower A is an upright conduit of considerable length closed at its upper end and communicating at its lower discharge end 2 with the inlet end of the horizontal drier B. The materials to be dried are fed into the upper end portion of this tower through the mixing conduit 3 provided with screw conveyor 4. These materials to be dried and disintegrated consist of an agglomerate of very wet particles of various sizes, for example, sludge, that is the residue from sewage which has been filtered to remove as much as possible of the free water and screened to remove the larger pieces of garbage. A sumcient quantity of previously dried and pulverized material has been mixed with this sludge so as to reduce to some extent the total moisture content of. the mixture. The stream of heated gases, which may be air or combustion gases, is fed into the upper portion of tower A through conduit 5 under pressure so that the gas stream will flow with considerable velocity downwardly through the drying tower A and then through the driers B, C and D, as hereinafter described. In order to most effectively carry out this drying process, it is desirable to introduce these heated gases at a very high temperature (for example 1500 Fahrenheit) but it would be impossible to introduce a gas stream of this temperature directly into the disintegrator C (hereinafter described) without injury to this mill or disintegrator unless this mill or disintegrator were specially constructed of suitable heat resisting metals. However, by passing this gas stream first through the driers A and B, in which preliminary drying stages are carried out, the temperature of this gas stream has been reduced to, for example, 500

to 700 Fahrenheit, so that the gases may be introduced safely into the disntegrator C.

The materials are dispersed and partially dried as they fall downwardly through tower A in contact with the hot gases flowing therethrough. These materials and the gases are deflected at the lower end of tower A into the inlet end of conduit B.

The inlet conduit B is positioned substantially horizontally and communicates at its discharge end with the inlet opening of mill or disintegrator C. This conduit B is of tubular or hollow cylindrical form and will usually be of considerable length, the length depending upon the extent of the drying operation that is to take place therein. This conduit has been intermediately broken away in the drawings -to facilitate the disclosure. Extending axially lengthwise of conduit D is a shaft 6 which is slowly rotated in any suitable manner, for example, by the small motor 1 through chain gearing 8. A plurality of rather narrow lifting bars 9, which extend longitudinally of conduit B parallel with shaft 6, are supported and rotated from shaft 6 by means of the spider constructions comprising the radial arms l0 and connecting and spacing rings These spiders are so constructed as to not materially impede the progress of the gases and partially dried material through the conduit.

The heavier materials will accumulate in the lower portion of conduit B but will be carried up by the lifting bars 9 which revolve in close proximity to the inner wall of the conduit. As these lifting bars reach the upper portion of the conduit this material will fall back through the stream of heated gases flowing through the conduit so that the materials will be dispersed and partially dried, and the lighter and more finely divided particles will tend to be carried forward in suspension in the gas stream. The heavier particles or masses of the wet material will fall back through the gas stream onto the lower portion of the conduit. It will thus be apparent that the lighter particles which dry more rapidly are advanced through the conduit at a greater rate than the heavier particles which are subjected for a longer timeto the heat of the gas stream flowing through the conduit. The rotating lifter bars 9 also tend to break up the heavier masses of material, and as such masses are dispersed and partially dried, they become lighter and are carried more rapidly through the conduit.

The disintegrator C comprises a substantially closed, preferably cylindrical casing consisting of spaced apart vertical end walls I2 and I3. connected by the outer peripheral wall l4. Within this casing are mounted two oppositely rotating cages or disintegrating structures indicated generally at E and F. The assembly for supporting and rotating these cages comprises a substantiallyhorizontal hollow-shaft l5 which is rotatably supported in bearings l6 and I! carried by the supporting structure l8. An inner shaft I9 is rotatable in suitable bearings 20 and 2| within the hollow shaft I5. A head 22 keyed on the inner end of hollow shaft l5 projects through the end wall I2 of the casing and terminates in an outwardly extending plate or disc 23 positioned adjacent the wall l2 and supporting the cage structure E. This cage structure comprises an outer circular series of spaced apart breaker bars 24 secured at one end in the disc 23 and extending horizontally substantially parallel to the peripheral wall H of the casing. These bars are here shown as of circular crosssection, although they might'be given a different cross-sectional configuration if desired. The opposite ends of the several breaker bars 24 of this circular series are connected by a ring 25. A second circular series of breaker bars 26 are also mounted at one end in disc 23 and connected at the other end by a ring 21. The bars 26 may be in all respects the same as the bars 24, but the circular series is of lesser diameter.

A head 28 is keyed on the reduced inner end portion of the inner shaft l9, and the supporting plate or disc 29 for the second cage structure F extends radially outward from head 28. This second cage or disintegrating structure F comprises two circular series of breaker bars 30 and 3| which may be similar in all respects to the breaker bars 24 and 26 except for the fact that the circular series are of different diameters. The inner circular series of bars 30 is secured at one end in disc 29. The opposite ends of the several bars 30 are secured in and support an annular disc 32 which projects beyond and overlaps the ring 21 and is substantially Vertically aligned with the ring of cage E. The circular series of breaker bars 3| is mounted at one end in disc 32, the opposite ends of the several bars 3| being connected by a ring 33.

It will be noted that the space within the cages is substantially closed at one end by disc 23 and at the other end by the disc 32 and ring 25 so that the material delivered centrally within the cages must pass radially outward between the several breaker bars before it reaches the peripheral wall I4 of the casing. Preferably the 5 several inner edges of the discs and rings are beveled inwardly, as indicated at 34, so as to tend to direct the material toward the center of the mill (that is away from the side walls I2 and i3) thus preventing clogging of the cage structure and tending to prevent an accumulation of material on the side walls of the casing.

Similar gears or sprockets 35 and 36 are secured respectively on the outer ends of the shafts i5 and I9, these gears being rotated through the belts or chains 31 and 38 from the similar motors 39 and 40 positioned at opposite sides of the shaft assembly. The motors 39 and 40 will rotate in opposite directions so as to rotate the shafts l5 and I5 and the cages E and F, respectively carried thereby, in opposite directions. Al-

ternatively a single motor could be used with reversing gearing between this motor and one of the shafts, or reversing gearing could be interposed between one of the motors 35 or at and the shaft driven thereby, in which case both motors might rotate in the same direction. In any event it is preferable to rotate the two cages E and F in opposite directions within the mill housing. It will be noted that each circular series of breaker bars rotates in a direction opposed to the direction of rotation of the next adjacent or overlapping series of bars so as to thoroughly disintegrate the material passing outwardl'y through the cage structures. The two cage structures might be rotated in the same direction but at different speeds (by making obvious changes in the driving gearing) and in some installations only a single cage structure may be sufficient. In the example here shown, each dis- 40 integrating structure is provided with two circular series of breaker bars, but it is to be under stood that each cage might be provided with one or a plurality of series of these bars as may be found necessary.

A rotary scraper, indicated generally at G, is

preferably used for dislodging the dried and partially dried material which is thrown out against the inner peripheral wall I4 of the casing. This scraper may consist of one or a plurality of transverse scraper bars 4| supported by side struts 42 from the outermost cage structure E so that the bar or bars 4! will rotate in close proximity to the inner surface of peripheral wall l4 of the casing.

The heated gas stream and the partially dried materials from conduit B are discharged into the central portion of disintegrator C through inlet opening 43 in wall l3, substantially in line with the axis of rotation of the rotating elements. (30 Since there is a tendency for these materials to be projected against the opposite wall of the easing, a spreader indicated generally at H is mounted on the head 28 carried by the inner rotary shaft I9. This spreader comprises a plurality r of vanes 44 carried by a conical flange 45 which projects inwardly of the casing away from the wall l2 and also outwardly toward the peripheral wall l4. These spreader vanes counteract the tendency of the material to be projected against the elements adjacent the wall l2, and also project or deflect the materials outwardly toward the central portions of the rotating cage structures E and F. The solid and liquid materials are drawn outwardly by the whirling air currents created by To the centrifugal action of the rotating cages between the several series of rapidly rotating breaker bars so that the solid materials are disintegrated or finely divided and eventually thrown outwardly against the outer peripheral wall M of the casing. The hot gases are also drawn outwardly by the centrifugal action of the rotating cages so as to remain in intimate contact with the solid and liquid materials throughout the space within the casing. The moisture is vaporized and absorbed or carried in suspension by the heated gases. The disintegrated and'dr'iedsolid materials are partially carried in suspension in the gases and partially accumulate against the outer peripheral wall of the casing, from which they are removed by the scraper G, and directed toward and through the outlet opening in the peripheral wall of the casing.

Preferably, if the fourth drying unit D is to be used, the outlet opening 48 will be positioned in the lower portion of the casing so that the materials may fall therethrough if not projected outwardly through the opening by the centrifugal action of the cages or if not carried in suspension in the gas stream. Alternatively, the outlet opening may be positioned as indicated at 41 in Fig. 4, in the upper portion of the peripheral wall 14, in which case any material discharged from the disintegrator must be sufficiently finely divided to be carried out in suspension in the gas stream, or projected through this opening by centrifugal force. The gases and suspended particles will be subsequently passed through a separator wherein the gases are relieved of the suspended dried and pulverized material.

In the preferred form shown in Figs. 1, 3 and 5, the disintegrated materials and gases from the disintegrator C are discharged through the bottom opening 46 into the inlet end of a second horizontal drying conduit D which may be much the same as the first drying conduit B, already described. This drier D is provided with a slowly rotating internal lifter similar to the one used in the drier B. The materials discharged from the disintegrator C into drier D will be rather finely broken up or divided, but will still be of various grades, that is, some of the particles will be larger than others. The finer particles, which will be most thoroughly dried, will be carried in suspension by the gas stream so as to pass rather quickly through the drying conduit D. The heavier particles will tend to fall to the bottom of the conduit D but will be lifted up and dropped back through the gas stream by the rotary lifting bars 9 so as to be further advanced through the conduit by the flowing gases. As the result, the heavier particles which are not as thoroughly dried as the more finely pulverized material, will pass more slowly through this conduit D and be subjected to a further drying operation. As a result, all of the material will be dried to the desired extent before emerging from the conduit D. These materials may pass into a collector or may be transported in suspension into a separator or grader.

A drying apparatus of this type may be used for drying very wet materials, and gases which are initially very highly heated may be used in order to expedite and make most effective the drying process. The temperature of these gases is reduced in the drying tower A and subsequently in the drying conduit B so that the temperatures will not be excessive in the disintegrating'apparatus C but the gases will still be sufiiciently hot to carry out a final drying operation in the conduit D after the pulverized materials are discharged from the mill or disintegrator. In any case, although there will be a considerable drop in the temperature of the gas stream as it passes through the various elements of the drying ap- 5 paratus, these gases will still remain at a sumciently high temperature when they emerge from the drying apparatus to carry out the water in vapor form.

It will be understood that the final drying unit D may be omitted, if not found to be necessary, in any particular installation. Also either one or both of the preliminary driers A and B can be used to perform the preliminary drying stage or stages before the materials and gases are fed into the disintegrator C. However, the complete apparatus as hereinabove described is desirable for thoroughly drying materials having a very high moisture content, since this complete apparatus permits the use of gases which have a very high initial temperature, thus permitting a most efficient and expeditious drying operation.

In some installations where the use of the final drying conduit D is not required, it may be more desirable to use an upper discharge outlet, such as indicated at 41 in Fig. 4. In this form of the apparatus the mill or disintegrator will act somewhat as a fan and the resistance through the apparatus will be decreased. This form of apparatus will also have certainadvantages in economizing space, where the use of a bottom discharge outlet and drying conduit B would be inconvenient or impracticable.

We claim: 1. In an apparatus for drying materials of high moisture content, a disintegrator comprising a substantially cylindrical closed casing, disintegrating structures rotatable therein and means for rotating these structures, an outlet passage leading from a peripheral portion of the casing,

a long substantially'horizontal inlet conduit communicating at its discharge end with a central portion of the casing, means rotatable within this conduit for lifting material and dropping it back through the conduit without positively advancing the material through the conduit toward the disintegrator, means for introdi'rolng material to be dried into the inlet end of the conduit, and means for directing a stream of highly heated gases successively through the conduit, the disintegrator and the outlet passage whereby the material is dried in two stages, the first stage within the conduit and the second stage within the distintegrator.

2. In an apparatus for drying materials of high moisture content, a disintegrator comprising a substantially cylindrical closed casing, disintegrating structures rotatable therein and means for rotating these structures, an outlet passage leading from a peripheral portion of the casing, a long substantially horizontal inlet conduit communicating at its discharge end with a central portion of the casing, means rotatable within this conduit for lifting material and dropping it back through the conduit without positively advancing the material through the conduit toward the disintegrator, a drying tower discharging at its lower end into the inlet end of the conduit, means for feeding material to be dried into the upper portion of the tower, and means for directing a stream of highly heated gases successively through the tower, the conduit, the disintegrator, and the outlet passage whereby the material is dried in three stages, the first stage within the tower, the second stage within the conduit and the third stage within the disintegrator.

JOE CRITES. RICHARD F. OMARA.

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