US2028395A

US2028395A - Apparatus for drying sludge

Info

Publication number: US2028395A
Application number: US661513A
Authority: US
Inventors: Laurence M Keoughan
Original assignee: Individual
Current assignee: Individual
Priority date: 1933-03-18
Filing date: 1933-03-18
Publication date: 1936-01-21
Anticipated expiration: 1953-01-21

Description

Jan. 2l, 1936.

' l.. M. KEoUGl-IAN' APPARATUS FOR-'DRYING SLUDGE Filed March 18, 1935 6 Sheets-Sheet l Jan. 2.1, 1936. L.' M. KEouGl-AN 2,028,395.

l I APPARATUS .FOR DRYING SLUDGE Filed March 18, I1933 e sheets-sheet 2 Jan. 21, 1936. l M` KEOUGHAN 2,028,395

AIQPARATUS FOR DRYING SLUDGE F1`ed March 18, 1933 Y 6 Sheets-Sheet 5 gg fa? ff! Jan- 21, 1936- L, M. KEOUGHAN v APPARATUS FOR DRYING SLUDGE e sheets-sheet 4 Filed March 18, 193s Jan. 2l, 1936. L. M. KEouGHAN APPARATUS FOR DHYING SLUDGE Filed March 18, 1955 6 Sheets-Sheet 5 v au felzce/fozgg/ azz I Jan. 2l, 1936. V I L M, KEQUGHAN 2,028,395

APPARATUS FOR DRYING SLUDGE Filed March 18, 1953 6 Sheets-Sheet 6 fnl/@milch Laurence/ff feozgy/zczfz,

Patented Jan.. 21, 19,36l

s PATENT OFFICE APPARATUS Fon DRYING SLUDGE Laurence Keoughan, Berwyn, Ill.

Application March 1s, 1933, sei-:a1 No. 661,513

The invention relates to a method and apparatus for drying domestic, industrial and similar sewage sludges as well as other material having similar characteristics.

More particularly, the invention relates to a method and apparatus adapted for drying sludges and similar material under vacuum at low temperatures.

The apparatus may be generally described as a dryer composed of a plurality of tubes and headers, to which steam or similar heating medium is supplied, positioned in a tank wherein a vacuum is maintained.

The material to be dried is distributed around and among the tubes and vaporization of-its water content takes place at the saturation temperature corresponding to the vacuum in the tank while steam in the tubes condenses at the relativelyA higher saturation temperature corresponding to the pressure maintained therein. A substantial temperature difference is 'thus maintained between the inside and outside surfaces of the tubes, thereby effecting a rapid heat transfer from the steam to the sludge or material being dried.l

i In drying sludge by ordinary methods or at atmospheric pressure with any degree of rapidity and economy, relatively high temperatures must n. be used. This tendsto scorch the sludge and drive off and waste valuable volatile constituents and produce gaseous compounds having pene- .trating and obnoxious cdors.

In drying the sludge at low temperatures under vacuum, wherein the maximum temperature to which the sludge may be subjected can be denitely controlled, the reductionv ofv gases and obnoxious odors may be reduced to a minimum and the valuable volatile constituents of the product are retained.

The moisture content of the sludge having been vaporized at low temperature in the vacuum tank is evacuated by a barometric jet'condenser or the equivalent. Of the small amount of gases produced at these relatively low temperatures, the greater portion will go into solution and be y carried out with the condensed water vapor and of vaporization of the steam in the tubes. More-` over, the temperature of the steam in the tubes being relatively low, comparatively low exhaust pressures from back pressure or exhaust, turbines may be used. Unusual economies maythus be obtained by the combination of this method of drying with the generation of power from high temperature, high pressure steam wherein the 5 majo'` portion of the total available energy is used lor power while'thelow grade and otherwise largely waste energy is utilized for drying. The 'exhaust steam being confined in the drier tubes, free from contamination by the' sludge or 10 vapors in the tank is thereby adapted to be returned as feed water to the highpressure boilers.v It also occurs when drying sludge by other methods, particularly by hot gas driers that a large waste of the product occurs due to :line dust par- 15 ticles being carried out by the exhaust gases. Moreover, the product itself tends to liberate large amounts of dust when being handled, thereby producing a serious explosion hazard. In drying sludge at low temperatures under vacuum, the various oils and greases are retained in the dry product substantially in their original forms so that the tendency of the product to break up into fine dust particles and the dust explosion 4hazard is reduced to a minimum or 25 rendered negligible.

Among the objects'of the invention is the provision of improved apparatus for utilizing the heat energy of steam to uniformly dry wet sludge without scorching, to a point where the sludge 30 retains its various oil and grease constituents in substantially their original form, thereby adapting the sludge so dried for use as fuel or fertilizer with a negligible disseminationthrough the surrounding atmosphere of dust particles or 35 unpleasant and unhealthful odoriferous gases.

Another object of the invention is the provision of apparatus for drying wet sludge. in a vacuum tank and improved means for preliminary heating and intermittent delivery of the 40 sludge'into the vacuum tank under conditions i whereby the sludge is explosively spread over the top of a drying pan.

Among the further objects of the invention is the provision of apparatus of the kind described which is simple in construction, adapted to be economically manufactured, and in its construction, assembly andi'ruse provides .improvements and conveniences adapted to practice methods not heretofore employed in the art for the same closure given. llili To this end, my invention consists in the novel construction, arrangement and combination of parts herein shown and described, and more particularly pointed out in the appended claims.

In the drawings, wherein like reference characters indicate like or corresponding parts:

Fig. 1 is an elevational view of lapparatus embodying the principles of the invention;

Fig. 2 is a sectional view along the line 2-2 of Fig. 1 drawn to a larger scale;

Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2 drawn to a larger scale;

Fig. 4 is a view along the line 4-4 of Fig. 1 drawn to a larger scale;

Fig. 5 is a sectional view ofthe upper end of a tank and a positive feed device connected therewith;

Fig. 6 is a detail sectional view -of one of a plurality of members providing bottoms for pans and devices for controlling the passage of sludge therethrough;

Fig. I is a side view of the device as shown in Fig. 6; Fig. 8 is a sectional view valong line 8-,8 of Fig. 2 drawn to a larger scale;

Fig. 9 isa view along line 3-9 of Fig. 2 drawn to. a larger scale;

Fig. 10 is a perspective viewof fragmentary portions of a plurality of movable coils comprising a heating device for the sludge;

Fig. 11 is a' perspective view of fragmentary portions of a plurality of stationary coils comprising the heatingdevice and providing a pan in which the movable coils are reciprocatedvertically;

Fig. 12 is a diagrammatic view of means for actuating the movable coils; and

Fig. 13 is a detail view showing a round or fillet connection oi the tubes with the headers forming the drying elements.

Referring now more particularly to the drawings, the numeral It! generally designates a closed housing providing a vacuum tank into which sludge is fed at the top and after passing through a drying apparatus is discharged in any desired degree ofl desiccation. The degree of desiccation may be such that the material is suitable for use as fuel under a boiler, as iertiliz ing material, or for a variety of other purposes.

. The. tank I0 is supported by a. framework comprising a plurality of vertical posts II resting upon a. floor or pedestals i3. The Vposts ii are connected by a plurality of angle members I2 with which the material comprising the tank I0 is connected by welding or by any other suitable means. A tank' I4, positioned above the tank Ill, is open at the'top to the atmosphere and has its bottom converging to form a pair of .hoppers IS, the tank Ill and the hoppers I5 providing-containers foi` the sludge or other material to be deliveredintothe tank I for drying. Steam jackets 42 .on the sides of the hoppers I5 provide Ameans for heating the contents of the hoppers prior to admission to the vacuum I8 in register with apertures 8i in the too of the v upper stem portions of the members 20 comprise pipes 2-I positioned in' register with the apertures 6I. A pair of rotors 21, mounted on a shaft 29 and fastened thereto by means of keys 30 are positioned one in each of the members 20. A pair of bearings. each comprising a pair of members 23 and enclosing packing 4I, are mounted on opposite sides of the tank I0 to provide supports for the projecting ends of the shait'23. The packing 4I seals the members 23 against flow of air` into the vacuum tank I0 around the shaft 29.

The rotors 21 are each apertured to provide `three longitudinally extending equally spaced troughs 28 each preferably covering about sixty degrees of arc. The downwardly and outwardly extending A.arms of the members 28 each form a pipe section 24 connected with conduits 25 and fastened thereto by a pair oi.' collars 2t. The pipe sections 24 are so positioned that any two of the troughs 28 may be brought into registry therethrough one of the pipe sections 2li. The lower troughs 28 in register with the pipes 2t will at the same time be moved to positions where one will Y register with the pipe'zi and the other with the other pipe 26.' Actuation of the rotors 2l in the opposite direction through one hundred and twenty degrees will repeat the trough filling and discharging operation with the diierence that the discharge of sludge will be through the other pipe 23. -A clearance space is provided between the rotors 21 and the members 2Q for ease of operation. The sludge contents of the pipes i8 and 20 provide a seal preventing the entrance of air through the space surrounding the rotors 2l.

The rotors 21 are oscillated through an angle of one hundred and twenty degrees as described by means of a motor 32. Step-down gear mechanism (not shown) and mounted in a housing 33 is operatively connected with the shaft of the motor 32 whereby a shaft 3ft connected with the step-down gear mechanism is revolved at a relatively slow rate. side of the housing 33 and provides a mounting for a sheave 31 operatively connected with the sheave 38 by a belt drive 39. The sheave 38 is flxedly mounted on a stud shaft 36 on which a disk -35 is similarly mounted. A link l0 connects the disk 35 with the outer end of an arm 3i mounted -upon the rotor shaft 28 in a manner whereby one completerevolution of the disk 35 actuates thearm to move the shaft 29 and rotors 2l back and forth through one hundred and twenty degrees. The rate of oscillation of the rotors 21 can be controlled, by the speed of the `motor 32 or otherwise, to suit the particular installation and in practice, it is found that six oscillations back and forth per minute are in general satisfactory. I

Complete dischargel of the sludge material A shaft 3Q projects from one from the troughs 26 is accomplished by reason of the sludge having been preheated in the hoppers i6 to a higher temperature than the saturation given to the sludge discharged in the manner described, together with the breaking up of the sludge particles due to its internal expansion, results in relatively wide distribution of the sludge over a drier pan 46 located immediately underneath the outletends oi.' the conduis 25.

The side walls of the pan 46 comprise a plurality of verticaly flat stationary coils or headers' 5I, 52 and 53. arranged in closely spaced edge relation to provide a rectangular enclosure open at its upper end. The upper ends of the vertical headersll, 52 and 56 are connected with horizontal headers 51 having a plurality of inclined' lugs 65 mounted thereon. A plate 561s' fastened to the lugs 65 in any suitable manner to provide an outwardly inclined flange for the pan. The

vheaders I are oppositely positioned on two sides of the pan and the headers 52 are positioned on the remaining sides. The headers 53 are angular in shape, as best shown in Fig. 11, to provide closed comers for the pan. A plurality of transversely extending ilat tubes 54 arranged in vertical tiersl are connected at their ends with the vertical headers 5|. The

headers

5I, 52 and 53 are connected at their lower ends with a round header 56. The connections of the tubes 54 with the headers 5i and of the

tubes

16 and 11 with the

headers

16 and 19, respectively, are curved to present fibrous material from accumulating atV A pressure reducing valve 14 is provided in the l pipe 66 to control the temperature and pressure of the steam in the coils and headers forming the pan 46. The steam thus admitted to the tubes and headers forming the pan 46 is discharged-as condensate through ya branch pipe'66 after giving on its heat energy in drying the sludge. The branch pipe 66 is connected with a main steam discharge pipe 69 and with a steam trap 65. The pan 46 is supported by a pair of I-beams 56 extending alongside the headers 52 and connectedl therewith by angles 55 by welding, or the like.

A drier pan 49 is positioned underneath the pan 4.6 to receive the sludge which has been passed through-.and partially dried inthe upper pan. The pan 49 is similar in construction and details to the pan 46 and is provided with an upper header 56similar to the upper header51 ot the pan 46 and is also provided with a lower header 66 similar to the lower header 56 of the pan 46. Exhaust steam is admitted into the pan .49 through a branch pipe 1i connected with an inlet pipe 16, the latter being controlled by a pressure reducing valve 14 and connected with the same the pan 49 is discharged as condensate through a branch pipe 12 into'a main discharge pipe 12 and a steam trapA 15. The pan 49 is supported by a pair of Ifbeams 56 and angle irons 55 in a manner similar to those providing a support for the pan 46.

'The vertical tiers of transverse tubes 54 positioned in the pan 46 are in alignment with the corresponding vertical tiers of tubes 54 positioned 'in the lower pan 49, and a plurality oi' movable heating elements are positioned between-the tubes 54 in each oi' the

pans

46 and 49.. The movable heating elements include a plurality of tubes 16 and '11 arranged in vertical tiers in the spaces between the tiers of tubes 54. The tubes 16 are positioned in alternate spaces between the tubes 54 and are connected at their ends by headers 16. The tubes 11 are likewise arranged in vertical tiers in the remaining spaces between the tubes 54 and are connected at their ends by lheaders 19. The upper ends of the headers-16 in the pan 46 are connected with a round header 66 and the headers 19 in the pan 46 are similarly connected with a round header 6I. The lower ends of the

headers

16 and 19 in the'pan 46 open into

round headers

65 and 66, respectively. The headers 66 and 6i are respectively connected with the inlet pipe 66 through flexible pipes 62 and 63 and elements through

flexible outlet pipes

61 and 66, the latter being respectively connected at one end with the

headers

65 and 86 and at the other end with a branch discharge pipe 69 opening into the main discharge pipe 69. i

The described movable heating elements, positioned in and in juxtaposition to the upper pan 46, are supported by vertically movable members in a manner that the tubes 16 and headers 16 are reciprocated vertically a predetermined amount and the tubes 11 and the headers 19 are likewise reciprocated vertically, the latter beingV moved upwardly while the former are being moved downwardly and vice versa. For'this purpose, the headers 66 are fastened to the vertical leg of a lhorizontally extending. angle 96 by means of bolts and bars forming clamps 9| and the header 6I is similarly fastened to the vertical legs of the horizontally extending angles 92 by bolts and bars forming clamps 93. A pair oi vertically extending channels 95 are fastened at their lower ends to the angles 96 and at their upper ends, the channels are fastened to the ends of'a pair of spaced apart channels 96. The channels 96 are oscillated vertically, in a manner hereinafter described, t'o impart oscillatory movement to the tubes 16, headers 16I and headers 65 positioned in and in juxtaposition to the upper pan 49. The middle portions of the horizontal legs of the angles 92 are fastened to the ends oi a pair of spaced apart channels 94 which are similarly oscillated vertically but in the opposite direction to the channels 96 as hereinafter described to correspondingly scillate the tubes 11, headers f 19 and headers 66.

The lower. pan 49 is similarly provided with tubes 1 6 arranged in vertical tiers in alignment with the tiers of tubes 16 in the upper pan 46 and similarly connected at their ends with headers 16. A plurality of vert-ical tiers of tubes 11 connected at their ends with headers 19 are similarly positioned in the pan 49 in alignment with the corresponding `tiers of tubes 11 in the upper pan 46. The upper ends of kthe headers 16in the pan 59 are connected with horizontally extending round headers |20 and the upper ends of the headers 19 positioned in the lower pan 49 are correspondingly connected with horizontal headers-I I9. The upper headers |20 are xedly fastened;to the lower headers .85 of the movable elements in the upper pan 48 by plates |2| and v clamp bolts |3|. The headers |I9 are also clonnected `with the lower headers 86 of the movable members ofthe upper pan 48 by clamp plates lilll and bolts |3|. The described connection of the corresponding movable elements of the pans and 49 causes the movable elements of the two pans to be reciprocated in unison and in the same manner.

The

vertical headers

18 and 19 positioned in the lower pan 49 are connected at their lower ends. with horizontal headers |25 and |24, respectively.

Steam is admitted into the pan i9 through the movable headers ||9 and |20 which are respectively connected by flexible pipes |22 and` |23 with the pipe 10 throughs. branch pipe 84 similar to that shown as connected with the steam inlet pipe 66?` The exhaust steam admitted into the lower movable elements through the exible pipes |22 and |23 condenses in the movable elements positioned in the lower tank and the condensate is discharged from the lower horizontal headers |24 and |25 through exible outlet pipes |26 and |21, respectively. The pipes |26 and |21 are connected with the condensate discharge pipe'13 and a steam trap 15 through a branch pipe 89 similar vto that shown in Fig. 4 as connected with the discharge pipe 69. The described steam inlet and condensate outlet connections for the movable elements of both the upper pan 48 and the lower pan 49 adapt the movable elements to be heated by exhaust steam in the same manner and from the same source as the stationary elements comprising the'respective pans are heated, the flexible elements being so arranged as to permit vertical reciprocatory movement of the movable. heatingelements, 1

The bottoms of the upper pan 48 and of the lower pan 49 each comprise a plurality of elements adapted'for oscillation to control the discharge 'of sludge from the pans. Each of the oscillatory elements comprise an angular pate |31 xedly fastened on a rod |36 extending parallel to the stationary tubes 54 and tothe movable'tubes 16'and'11. The rods |36 in the bottom of the pan 48 are rotatably mounted von the vertical legs oi'angles |35, the angles being fastened to the bottom flanges of`theI-beams 50 forming a support for the pan. The rods |36 are held against longitudinal movement by pins |38 andv washers |39 positioned between the pins and the vertical legs of the angles |35. -The movable elements comprising the bottom of the pan 49 are similarly rotatably mounted on a pair of plates |28 fastened to the bottoms of the I-beams 50 which provide supports for the pan.

Transverse or lateral movement of the movable heating elements and supports therefor is prevented or made negligible by spaced apart vertically extending angles |29 fastened to the plates |28, with the stems of Ts |30, which are clamped to the horizontal headers |24 and |25, projecting between the outstanding legs or the Aangles as' best shown in Fig. 8. 'I'he angles|29 thereby provide runways permittingvertical movement or the Ts |30 along with 'the movable heating elements to which they are attached and hold such elements against movement horizontally.-

` The movable elements in the upper portion of the device are likewise held against horizontal movement by a plurality of bolts 99 having their lower ends extending through the horizontal legs of the angles-90 and 92, the latter being apertured to permit vertical movement of the angles. The bolts 99 are arranged in groups of four and are supported in xed position by pairs of plates 98, mounted on opposite flanges of I-beams 91, the bolts being arranged to clamp the plates in contact with the beams. The described runways underneath the pan 49 and the bolts 99 positioned above the top of the pan 48 cooperate to permit vertical and to prevent horizontal movement of the vertically movable elements and thereby maintainthe alternately arranged tiers [of movable tubes 1B and 11 in uniform spaced apart relation to the adjacent tiersoi dat stationary tubes 54 between which the movable tubes are positioned.

Any suitable mechanism may be used for raising and lowering the movable heating elements positioned in the

pans

48 and 49. Equal and opposite vertical reciprocation of the tubes 16 and' 11 is accomplished by fluid pressure actuated means illustrated in the drawings as positioned at the upper end of the vacuum tank |0.- A block l|0| mounted on a pair of spaced apart I-beams |00 Y provides a support for the duid actuated means. Ihe-I-beams100 are arranged in spaced apart relation tofthe I-beams 91 and are preferably symmetrical relative to the vertical center line through the tank l0 and the

pans

48 and 49. The actuating means comprises an upper cylinder |02 and a lower cylinder |03 respectively mounted on the upper and lower sides of the block |0|. The cylinder |02 contains ai piston |04 having a. rod |05 projecting from the upper end of the'cylinder between the channels 96. The rod |05 is operatively connected with the channels 96 by a pin |08, the webs of the channels providing bars for the ends of the pin. 'A plate ||5 and a block |09, positioned on opposite sides 'of the channel webs, provide additional bearings for the pin |08. 'I'he lower cylinder |03 contains a piston |06 and a piston rod |01, the latter being connected by a pin |08 with the spaced apart vchannels 94 in a manner similar to the connection of the rod |05 with the channels 96.

Movement of the piston |04 upwardly from the position shown in Fig. 5 will correspondingly elevate the channels 96 and the movable elements suspended therefrom, including the vertical tiers of tubes 16 positioned in vertical alignment in alternate spaces between the at tubesv 54 in the

pans

48 and 49. Movement of the piston |06 downwardly from the position shown in Fig. 5 depresses the channels 94 and similarly moves downwardly all of the movable elements suspended from such channels, including the vertically` aligned tiers of tubes 11 positioned in alternate spaces between the :dat tubes 54 in the

pans

48 and 49. The described movement of the

channels

94 and 96 causes oppositevertical movement of all of the tubes-16 and 11 positioned in the

pans

48 and 49. Inward movement of the pistons |04 and |06 in their respective cylinders |02 and |03 will correspondingly move the

tubes

16 and 11 vertically in the opposite direction from that produced by the outward movement of the pistons.

Fig. 12 diagrammatically illustrates means for simultaneously equally actuating the pistons |04 and |06 in opposite directions. A cylinder |33 is shown as connected with the cylinders |02 and |03 by pipes ||2 and respectively. The cylinders |02, |03 and |33 and the pipes conthereby simultaneously v necting the cylinders are` illled with any suitable iiquid. The cylinder |33,contains a piston ||1 connected by a piston rod ||8 with any suitable means (not shown) for reciprocating the piston ||1. Movement of the piston ||1 downwardly from the position shown will force the liquid out of the cylinder |33 through the pipe into the cylinder |03, thereby lowering the piston |06. Downward'movement of the piston |06 inthe cylinder |03 will force liquid out of the cylinder |03 and into the lower end of the cylinder |02, resulting in lifting the piston |04. Upward movement of the piston |04 will force liquid from the upper end of the cylinder |02', through the pipe |I2, into the cylinder |33 above the piston ||1. Upward movement of the piston ||1 will result in ilow of the liquidI in a directionv opposite to that described, with the result that the piston |04 will be moved downwardly and the piston |06 will be moved upwardly. The cylinders |02 and |03 are of equal diameters and as a result, the described reciprocating movements of the pistons |04 and |06 are equal.

As showniin Fig. 4, the cylinders 02 and |03 are not concentric, the upper cylinder |02 being arranged at one side of the center of the tank in such a manner that it is concentric with a vertical line through the center of gravity of the movable elements carried by the channels 96. Similarly, the cylinder |03' is positioned at one side of the vertical center line of the tank I0 so as to coincide with the vertical line of the center of gravity of the movable elements suspended from the channels 94.

Sulciently low vacuum is maintained in the tank I0 to permit the described transmission of heat to the sludge from the low pressure and temperature steam in the verticaland stationary tubes forming the

pans

discharges the condenser water and'condensed steam into any suitable receptacle, reservoir, or the like, providing a water seal |49. The condenser |4| and the ejector |43 are shown diagrammatically only and may be any devices respectively suitable for functioning as a condenser and as an ejector.

The sludge fed as described by the feed device through the conduits 25 into the pan 48 tends to move by gravity downwardly through the spaces between the vertical tiers of fiat tubes 64, such downward movement being acc'elerated by the vertical reciprocation ofthe

tubes

16 and 11 as described. The lower edges of the tubes 1B and 11 provide a fiat curve of a width such that there is a space between the adjacent sides of the tubes and the ,stationary flat tubesl 64,

I'he tubes

16 and 11 converge towards their top edges so that as they are moved upwardly, there is only a slight tendency to lift the downwardly moving sludge while the surface presented by the wider lower edges' of the tubes tends to force the sludge deposits.

downwardly as the tubes descend. The drying of the sludge in contact with and contiguous to both the stationary and movable tubes tends to cause a decrease in the rate of heat transfer from the tubes to the sludge as the sludge moves downwardly. The movement of the

tubes

16 and 11 relative to the tubes 14 is such as to' prevent adhesion of sludge to any particular tube for a period long enough to cake or dry thereon and thereby avoidsthe formation of heat insulating The described movement and spacing of the tubes not only moves the sludge downwardly but also to a certain degree forces the sludge through the spaces between adjacent tubes of the same vertical tiers, thereby effecting complete movement of sludge that might otherwise collect and form objectionable heat insulating deposits. The tapering upper` edges of the movable tubes present a pointed surface also' preventing the sludge from collecting on the top thereof. rIhe drying effect resulting from the contiguity and contact of the sludge with both the movable and stationary tubes is progressive downwardly. By control of the temperature of the steam and the rate of the movable elements and the sludge,

the latter may be delivered from the bottom of the pan 48 at any desired degree of desiccation.

The sludge partially dried as described duringV quantity of the sludge is thereby discharged Upon elevation ofthe tubes 16 and the simultaneous depression of the tubes 11, the lowermost of the tubes 11 will'similarly contact with the opposite edges of the plates |31 from those shown as depressed in Fig. 6 and will correspondingly force a more or less definite amount of the partially dried sludge through the bottom of the pan. 'In the interim wherein nonekof thetubes 16 and 11 are in contact with the plates |31, the latter will be moved by gravity back to their .normally closed position. The vertical reciprocatlon of the

tubes

16 and 11 thereby causes the lowermost tubes to discharge the sludge through the bottom of the pan 48 into the lower pan 49 where theI same process is repeated as described for the pan 48. i q

While a single pan of the kind described may be satisfactorily used to dry the sludge to any desired degree, I preferably use a plurality of y pans through which the sludge is progressively fed as the partially dried sludge may thereby be subjected to higher temperature gradients as the dryinglprogresses.` The rapidity of drying for a lgiven temperature gradient decreases with the each pan at a higher pressure than in the panimmediately above with .the result that the saturation temperature of the steam in the pans is progressively increased in accordance with the diminished moisture content of the sludge. The

requisite differential of steam pressures in the respective pans may be maintained solely by ma-f nipulation of the control valves 14 when both pans 48 and 49 are connected Vwith the same source of The sludge is discharged from the pan 49 into the downwardly converging bottom of the tank Ill having an outlet controlled by a valve 4B, adapted for manual operation to remove the dry sludge, the valve being of any suitable form to` provide a seal preventing access of air intothe tank. l

` The condenser MI is adapted to maintain a vacuum of 2E to 2 inches of mercury in the tank I0 at which vacuum wet sludge is rapidly dried by the steam in the tubes and headers comprising the

pans

48 and 49. Steam having as low a pressure as ve pounds gauge may be used and steam at a pressure of one hundred pounds gauge may be used without scorching the sludge or releasing odoriferous or volatile constituents of the sludge. Thus, it Will be seen that I have provided a novel method and apparatus for drying wet sludge and similar materials under vacuum, whereby low temperature and pressure steam not otherwise Iavailable for power can be utilized for rapidly drying the sludge without scorching the sludge or driving off valuable volatile constituents or the producing of gaseous compounds having penetrating and obnoxious odors. y

Having thus described the invention, it is obvious that various immaterial modications may be resorted to without departing from the spirit of the invention; hence I do not wish to be limited to the exact form, construction and arrangement of parts herein shown and described, or uses mentioned.

What I claim as new and desire to secure by Letters Patent is:

ll. In apparatus of the kind described, a tank, exhauster mechanism operable to maintain less than atmospheric pressurev in the tank, a plurality .of horizontally extending tubes positioned in the tank, said tubes beingA arranged in spaced apart vertical tiers, alternate rows of said tiers being stationary and the remaining tiers being movable, means operable to vertically reciprocate said movable tiers of tubes, means operable to deliver sludge into the tank'above said tiers in a manner whereby the .sludge is distributed between the uppermost tubes of said tiers, and

means adapted to deliver steam -into said tubes' `at selected pressures and corresponding temperatures.

2. In apparatus of the kind described, a tank, exhauster mechanism operable-to maintain less than atmospheric pressure in the tank, a plurality of horizontally extending tubes positioned in the tank and arranged in spaced apart vertical tiers with the tubes comprising each ticrspaced apart vertically, alternate rows of said tiersy of tubes being stationary and the remaining tiers of tubes being movable, means operable to vertically reciprocate said movable tiers of tubes in amanner whereby alternate ones of said movable tiers are caused to ascend as the remaining movable tiers are caused to descend, means werablel to deliver sludge into the tank in a manner whereby it is distributed between the uppermost tubes of said tiers, and means adapted to deliver steam into said tubes at selected pressures and corresponding temperatures.

3.-In`apparatus of the kind described, a tank, exhauster mechanism operable to maintain less than atmospheric pressure in the tank, a drier pan positioned in the tank, said pan comprising a ed to deliver steam into said headers and tubes v at selected pressures and corresponding temperatures.

4. In apparatus of the kind described, a tank, exhauster mechanism operable to maintain less than atmospheric pressure in said tank, a drier pan positioned in the tank, said pan comprising a plurality of vertically extending headers forming the side walls of said pan, a plurality of horizontally extending tubes connected with said headers and arranged in spaced apart vertical tiers, a plurality of horizontally extending' movable tubes arranged in vertical'tiers between said rst mentioned tiers, means operableto vertically reciprocate said movable tiers of tubes in a manner whereby alternate ones of said movable tiers are caused to ascend as the remaining ones of said movable tiers are caused to descend, means operable to deliver sludge into the tank and to.

distribute the sludge over the top of said pan, a plurality of plates extending parallel to said tubes and forming the bottom of the pan, individual mounting members adapting said plates /for limited oscillation about a longitudinal axis',

5; In apparatus of the kind described, a tank,v

exhauster mechanism operable to maintain less than-atmospheric pressure in said tank, a plurality of horizontally extending tubes positioned in the tank and arranged in groups spaced apart vertically, the tubes of each group being arranged in spaced apart vertical tiers, alternate ones of said tiers in each group being stationary and the remaining tiers being movable, means operable to simultaneously vertically reciprocate the movable tiers of each group, means operable to deliver sludge into the tank above the upper group of tubes, and means adapted to deliver steam into eachof said groups of tubes at selected pressures and corresponding temperatures.

6. In apparatus of the kind described, a tank. exhauster mechanism operable to maintain less than atmospheric pressure in said tank, a plurality of drier pans arranged in the tank in spaced apart vertical relation, each of said pans comprising a plurality of 'vertically extending headers forming side Walls for the pan, a plurality of horizontally extending tubes positioned in each pan connected with said headers and arranged -in spaced apart vertical tiers, a plurality of longitudinally extending movable tubes arranged in vertical tiers between said tiers of stationary tubes, means operable to vertically reciprocate delivering steam to the headers and tubes com-v prising the respective pans being adapted to deliver steam at relatively low pressures andcorresponding temperatures and to deliver steam to each next lower pan at successively higher pressures and corresponding temperatures.

JI. Apparatus for drying material of the kind described comprising a tank, exhauster means adapted to maintain less than atmospheric pressure in the tank, a plurality of stationary tubes arranged in spaced apart relation in the tank, a plurality of tubesreciprocally movable in the spaces between said tubes and operable thereby -to rub the advancing material over the adjacent surfaces of said stationary tubes, and means adapted to deliver steam into said tubes at selected pressures and corresponding temperatures.

8. Apparatus for drying material ofthe kind described comprising a tank, exhauster means adapted to maintain less than atmospheric pressure in the tank, a plurality .of stationary tubes arranged in the tank in spaced apart tiers, means operable to deliver material between said' tubes, a plurality of tubes reciprocally movable between said tiers, the reciprocation of said tubes adapted to advance and 'rub the material over the adjacent surfaces of the tubes, and means adapted to, deliver steam into said tubes at,selected pressures and saturation temperatures.

9. Drying apparatus of the kind described comprising a tank, exhauster means adapted to maintain less than atmospheric pressure in the tank.`

a plurality of tubes in the tank arranged in spaced apart vertical tiers, a plurality of elements reciprocally movable between said tiers adapted to rub the advancing material over the adjacent surfaces of the tubes, a hopper positioned on the tank above said tubes and providing a container for material to be dried, means operable to intermittently move material from the hopper into the tank above said tubes, and means adapted to heat the hopper contents to a temperature such that its internal pressure explosively spreads the material over the spaces above said tubes.

10. In apparatus for drying material of the kind described, a heating device comprising a plurality of stationary tubes arranged in spaced apart vertical tiers, a plurality oftubes reciprocably movable between said tiers, the reciprocation of said tubes being adapted to advance and rub the material over the adjacent surfaces of the tubes, means operable to reciprocate said movable tubes, and means adaptedl to deliver a heating iluid into said tubes at selected pressures ones of the movable tiers are caused to ascend as the remaining movable tiers are caused to descend, and means adapted to deliver a heating iiuid into said tubes at selected pressures and corresponding temperatures.

12. In apparatus for drying material of the kind described, a heating device comprising a plurality of stationary, elongated hollow members arranged in spaced apart relation, a hollow member positioned between said stationary members, means operable to deliver material between said stationary members, means .operable to reciprocate said movable member in contact with said stationary members and adapted thereby to rub and advance said material over the adjacent surfaces of said members, and means adapted to deliver heating iluid into said members at selected pressures and corresponding temperatures.

13. In apparatus of the kind described, a tank, a drier pan positioned in the tank, said pan comprising a plurality of vertically extending headers forming the side walls of said pan, a plurality of horizontally extending tubes connected with said headers and arranged in spaced apart vertical tiers, a plurality of horizontally extending movable tubes arranged in vertical tiersrbetween said first mentioned tiers, means operable to vertically reciprocate said movable tiers, means operable to deliver sludge into the tank and to` dis-Y of horizontally extending tubes connected withr said headers and arranged in spaced apart vertical tiers, a plurality of horizontally extending movable tubes arranged in vertical tiers between said rst mentioned tiers, means operable to vertically reciprocate said movable tiers of tubes in a manner whereby alternate ones of said movable tiers are caused to ascend as the remaining ones of said movable tiers are caused to descend, means operable to deliver sludge into the tank and to distribute the sludge over the top of said pan, a plurality of plates extending parallel to said tubes and forming the bottom of the pan,

individual mounting members adapting said' plates for limited oscillation about a longitudinal axis, the edges of said plates being in the path` of the lowermost of the tubes forming said movable tiers whereby downward movement of each tierforces contiguous edges of adjacent plates downwardly, and means adapted to deliver steam into said headers and tubes at selected pressures and corresponding temperatines.y

15. In apparatus oi the kind described, a tank,

a pluralityv of drier pans arranged in the tank in -spaced apart vertical relation, each oi' said pans comprising a plurality of vertically extend.- ing headers forming side walls for the pan, a plurality of horizontally extending tubes positioned in each pan connected with said headers and arranged in spaced apart vertical tiers, a plurality of longitudinally extending movable tubes arranged in vertical tiers between said tiers of stationary tubes, means operable to vertically reciprocate the movable tiers in each lpan in a manner 'whereby alternate ones oi' said movable tiers are caused to ascend as the remaining movable tiers are caused to descend, means operable to'deliver sludge into the tank and to distribute the sludge over the top of the upper pan, a plurality 'of plates forming the bottom of each pan,

`said plates extending parallel to said tubes, individual mounting members adapting said plates for limited oscillation about a longitudinal axis,

the edges of said plates being in the path of ther` lowermost of the tubes forming said movable tiers in each pan whereby downward movement of each tier forces contiguous edges of adjacent "lo plates downwardly, and individual means sevs being, adapted to deliver steam at relatively low pressures and corresponding temperatures and to deliver steam to each next lower pan at successively higher pressures and corresponding temperatures.

' LAURENCE M. KEOUGHAN.