US2883162A

US2883162A - Condenser with rotary scraper

Info

Publication number: US2883162A
Application number: US552951A
Authority: US
Inventors: Rapson Bryan
Original assignee: Aluminium Laboratories Ltd
Current assignee: Alcan Research and Development Ltd
Priority date: 1955-12-13
Filing date: 1955-12-13
Publication date: 1959-04-21
Anticipated expiration: 1976-04-21
Also published as: DE1078540B; CH363012A; GB800486A; FR1167095A

Description

Filed Dec. 13; 1955 April 21, 1959 B. RAPSON 2,883,162

CONDENSER WITH ROTARY SCRAPER 2 Sheets-Sheet 1 0\ E II 20 INVENTOR. Bryan Rapson Afro/nay B. RAPSQN CONDENSER WITH ROTARY SCRAPER April 21, 1959 Filed Dec. 13, 1955 2 Sheets-Sheet 2 INVENTOR.

Bryan Rapson Men: 9. W

A f lomey CONDENSER WITH ROTARY SCRAPER Bryan Rapson, Arvida, Quebec, Canada, assignor to Aluminium Laboratories Limited, Quebec, 'Quebec, Canada, a corporation of Canada Application December 13, 1955, Serial No. 552,951

7 Claims. (Cl. 257-10) This invention relates to condensers, and particularly to apparatus providing surfaces upon which solid material is to be deposited from a passing fluid. The invention is especially related to condensers, having extensive cooled surfaces, for use with gaseous fluids which condense to the solid state, and to that end, certain presently preferred embodiments have been particularly intended for use in the condensation of aluminum chloride from posed to displace such coatings by means of mechanical scrapers and by various types "of impact mechanisms, e.g., loose chains, to pound and pulverize the coating so that it breaks loose from the condenser surface.

In the condensers of the prior art, where such scraper or impact devices are used, the condensed material may tend to condense on the surface of the scraping or impact mechanism. In such cases, the efiiciency of the scraping or pounding operation is impaired so that the apparatus must be shut down periodically to clean the scraper or cleaning apparatus. Indeed, accumulation of solids on the removal device, whether by condensation or by being caught in falling from the condenser wall,

e.g., as sometimes occurs with helical scrapers, may even become such as to block the movement of the device completely.

An object of the present invention is to provide a condenser of the type described with scrapers which not only clean the cooled condenser surfaces, but which also clean the scraper surfaces, so that the apparatus can run continuously for long periods without being shut down for cleaning the scrapers.

Another object is to provide improved scraper structure for a condenser of the type described.

Further objects are to provide improved gas inlet structure for a scraper of the type described, and to afford other structural improvements, in the support and arrangement of the scraping means, for reliability of operation and especially for the free, non-interfering removal, and ready collection, of dislodged condensate.

The foregoing objects are attained in the apparatus described herein, by providing a condenser arrangement comprising an upright, e.g., vertical or substantially vertical, shell having a cross-sectional contour defined by the external portions of a plurality of intersecting circles, together with vertically elongated scraper elements rotating on upright axes concentric with the circles and each having a lenticular shape in cross-section, arranged ICE for jointly affording a scraping or sweeping of the interior surface of the shell and of the surfaces of the rotating elements. More specifically, an effective and simple device of the invention comprises, in combination with means for directing gas (from which material is to be condensed) vertically lengthwise in the shell on all sides of the scrapers, and in combination with receptacle means at the bottom of the shell for collecting the solid material which falls as it is removed by the scrapers, a vertical condenser shell having a horizontal cross-section in the shape of two abutting generally circular segments, each segment being greater than a semi-circle. Within the shell, two scrapers are mounted for rotation about vertical axes, the two axes being at the centers of the two segments. Each of the scrapers has a horizontal cross-section which is generally lensshaped, and is defined by two arcs having radii approximately equal to the distance between the centers ofthe segments and having centers of curvature at diametrically opposite points onor-approximately on the circumference of the surface of the segment within which the given scraper turns. The two scrapers are connected to a common drive for rotation in the same direction and are spaced angularly by 90 about their respective axes.

termittently scrapes the surfaces of the otherscraper, so

sides of the scrapers.

.that nocondensed material may build up within the shell,

either on the shell surface or on the scraper surfaces.

Cooling jackets or' equivalent means are provided on the outside of the shell, so that material tends to condense on the inside. The scraper elements can be made longer than the shell cooling jackets, i.e., if such arrangement is desirable, to make sure there is no condensation of material at any pointon the shell not covered by a scraper. i I

An inlet for gaseous material to be condensed is located adjacent the upper end of the condenser and passage means is provided for distributing the entering gas to all parts of the shell cross-section, thereby avoiding the building up of pressure differences on the opposite A heater jacket may advantageously be placed around the condenser shell adjacent'the inlet, in order to prevent condensation in or adjacent to the inlet passage and the fluid distributing passages.

Other objects andadvantages of the invention will becomeapparent from a consideration of the following description and claims, taken together with the accompanying drawings.

In the drawings:

Fig. l is a view partly in section on line 1-1 of Fig. 2

and partly in elevation, and with certain portions broken away, of a condenser including a scraper mechanism constructed in accordance with the invention;

Fig. 2 is a plan view of the condenser of Fig. 1;

Fig. 3 is a sectional view taken on the line III-III of Fig. 1;

taken on the line IVIV cordance with the invention;

Fig. 7 is an elevational view, with portions broken away, showing a complete scraper constructed in accordance with the invention;

.Fig. 8 is; a plan view of the scraper of Fig. 7;

Fig. 9 is a verticalsectionalview taken on the line Patented Apr. 21, 1959 IXIX of Fig. 8, showing the details of construction of one section of the scraper of Fig. 8;

Fig. is a diagrammatic view similar to Fig. 5, il-

lustrating the geometry. involvedv in determiningcertainr dimension of. actual physical apparatus, with. .clears ances;.and

Fig. 11. is, a diagrammatic viewsimilar. to.. Fig 1.0,,il+

lustrating the geometry involved in. connection: with another. clearance. requirement. .Referring ,to. the drawings, there is shown in Fig. 1. a complete. condenser includinga shell 1, whose .cross-.

section, as. bestseen in Figs. 3} and. 4, is. in the. shape of.

. 4. vided two jackets 16 and heating jackets, being supplied with heating fluid through an inlet pipe 18, an outlet pipe 19 and a U-shaped connecting pipe 20 which connects the front ends of the two jackets. The inlet pipe 18 is supplied with a heating fluid which may be, for. example, superheated steam or a eutectic mixture of diphenyl and diphenyl oxide,

which is: commercially available'under. the: name- Dowtwo. abutting, generally. circular segmentsv 1a. and. 1lz.

The. shell. 1 extends vertically. The upper end. of, the

shell has. a .flange or ring,2 welded. toitsperiphery, A/

coverplate. 3.is.mounted'on the. flange 2. by anysuitable means, such. as bolts 4. The cover plate.- 3. supports,

by. means of a bearing structure. to. be. described. more completely below, two; vertically extendingshafts. :5. and.

6, which. extend downwardly throughoutthe. length of the shell .1.

Fixed on.the shafts, 5 and 6 are a. pairof,scrapers.7 and.8. Each scraper hasagenerally. lens-shapedcrosssection,as shown in Figs. 3 and 4. I

The geometry of the cross-sections of the scrapers. 7. ands is-describedmore completely below in; connection. with Fig, 5,. 'For the present, it isv consideredrsuificient. topoint outthat each of. thescrapers 7. and 8.hasa.cr,oss sectiondefined by two arcs whose radii are; equalto the.

distance between. the centers of. theshafts 5 and 6,.said.

arcs, for each scraper; having centers of curvature at.

diametrically opposite points. on the circumference. of

the. circle which definesthatone of the segments laand 1b withwhich the axisof rotation of the scraper is ..co.- axial. The angular position of scraper 7. within the segment 1a of. the shell is spaced 90 from the. angular. position of scraper 8 withinthe segment: 1b. of the. shell.

The

shafts

5 and 6 extend upwardly, through the plate 3 and through another supporting plate 9.. Above,

therplate 9., the

shafts

5 and 6 early gears 10 ands-11, respectively, both of which meshwith a driving gear 12. carried on. a drive shaft 13, which may be driven. from. any suitable source of power- Notev that drivingarrangement is such. that boththe shafts. 5;.andr

In consequence, no solid material deposited.

ple of such receptacleshown in theivdrawings iszalcon- The tr p densate trap; cylinder generally indicated at 14.. condenser can be. mounted at or 'on, the' top of the 14, by suitable means not shown.

The gas or.- vaporto becondensed. entersthe apparatus through an inlet conduit 15, best shown in Fig. 4-. and.

located at the rear of the apparatus as it is viewed in Fig. 1. The inlet condhitIS' opens into the middle of the rear side of the shell 1; At the l'evelLopposite the inlet conduit 15, the

scrapers

7 and 8 areprovided with Qpenings7a, 7b and 8a, 811'. See Figs. 4 and 7.

" and122, to makesure thatnocondensationtakes place on...

Theseopeningsallow'the entering-fluid to pass through the scrapers so that the fluid may pass downwardly" through the condenser on all sidesof the-rotating scrapers and no" pressure diif'erential is developed acrosseither of the scrapers. v I

Around the-peripheries of the two segments ofthe shell'l, at the l'evel'of the inlet conduit 15", thereare protherm. This heatingfluid is maintained at a temperature above the boiling, point. of the gaseous fluidenteringthe shell 1; The object ofthe heating of Ithe shellladjacent the inlet 15 is to prevent any condensation of the gaseous material on thesurface of'the inlet 15, around theupper ends of the scrapers, orin the passages 7a, 7b, 8a, 8b. If the heating were not employed, condensation might take place suificient to clog these passages.

It might be considered that, by virtue of the presence of the; heating jackets, the: scrapers: 7. and: 8 are unnecessary, adjacentth'e. inlet 15 andltheir'upper ends couldbee However, if sucha conterminated '1 below that point: struotion; is. used, there: might bev condensation om the shafts Srand 6;,-since:they. would beusomewhat separated fromthe heatingrinfluence'and theirremaining partsibeloware:in. efiect cooled. Since there is no; mechanism for cleaningtheupper endsnof thosefshafts, the condensation could build up on-them'until' it reached apoint where it would impede thfi'OPfiIHtiOHlQf. the: apparatus.

A: pair. of cooling :jackets 21; and-.22 are. locatedionzthe outsideof the shell ltwithatheiri upper ends. a;short;di's.- tancebelow the jackets 16 and 17 and extending. down:

wardlyto a point somewhat above theglower ends; of. the. scrapers17 and 8. The jaokets-21 and 22. are provided. with cooling fluid. inlets I and. 24 respectively at. their lower ends andiwithoutlets' 25 andl26pat their: upper.- ends:. The jackets 21 and 221 are COIlStI'llCtGduiH'. sections," the. sections being hseparated byreinfiorcingplates 27.. Small. by pass conduits 28 extend. through the reinforcingplates: outside the main jacketstructure; -soas: toprovide :a con-p tinuouspath forcooling'fluid through the:jackets:v Any suitable cooling fiuidzmaybe used, for example, water.

- It.is-important.that thescrapers- 7-andr8 extendto and preferably. below the bottoms of the cooling jackets 21 any- -unscrapedsurface on the inside; of the shell 1. To.

the:- same end, it.- is: desirable that the. scrapers extend.

above the tops of the cooling jackets.

The shafts 5 and. 6'- Which carry thescrapers extend;

through. the. end. plate 3 and thence through a ,pair of.

sleeves

28 and 29 1 and; are journaled in the bearing plate.- 9-by means of balLbearings 30. Above the-.balhbearings 3.0,;the. shaftsS and-6 carry the gears-mend 11 by which. the shafts are driven from the gear 12 on the drive shaft: 13.

The bearings 30.-are" combined guidexand thrush-bean ings andsupport the entire weight ofthe shaftsS and :6. andtheir associated scrapers 7and'8; The shaftsS and- 6:.ar.e also guidedxby. guide bearings 31 located intheend plate 3 and by lower guide bearings 32.which,-aremounted:

on. a crossbar 33 fixed. on a bar 34 which spans the cylinder 14 below the

scrapers

7 and 8... Lower guide bearingsfil .are surmounted by suitable. gas=tight rotary seals, suchas the one. generally indicated at- 31a.-

The. condensatetrap 14 is. provided with an outlet .pipe 4 35.. leading to.a.pump 3.6 by.means-of. which the uncondensed vapor or gas is drawn-oil. The. trap 14 may be. provided :witha. suitable door 37' for the purpose of. removing the condensate material.

It.is, desirable. tornake thecondenser rather long, par-- ticularly where the. vaporized material: enters at a. very high temperature and. must. be.v cooled substantially be.

fore it leaves the apparatus in order to condense substan-.-

tially all the available material. In such an. elongated condenser itisd'esirable. for manufacturing purposes to make the scrapers in a sectional arrangement, as'illustrated" in*Figs'.. Tand9: As there shown, the-scraper Tcomprises 17. These jackets, serve. as.

three sections 7c, one of which is shown in longitudinal,

section in Fig. 9. Each section is a casting having a central cored passage 38 to receive the shaft and cored side passages 39 and 40. In the two lower sections 7c,

openings 7a and 7b.

Figure 5 The geometry of the profile of the

scrapers

7 and 8 is illustrated in Fig. 5. Each of the scrapers has two arcuate surfaces. The radius of curvature R of each arcuate surface is equal to the distance D between the axes of rotation :of the

scrapers

7 and 8. On each scraper, the

centers of the curvature of the two arcuate surfaces are r located diametrically opposite each other, and (HI/[116 periphery of the circle defined by the path of rotationv of the edges of the scrapers.

The diameter :or major axis a of each scraper profile V is equal to R /2 The thickness b or minor. axis of each scraper is equalto /2 l)a or 0.4l42a. The distance D equals half the sum of the major and minor axes, viz.,

/2 (a+b) As indicated, R is equal to D and by geometry, 30

also equal to The inside radius of each circular segment of the casing 35 or shell is by theory salsa If these relationships are followed, the edgesof the scrapers will effectively scrape the interior surfaces of the shell 1 and will also scrape the exterior surfaces of each other. i

Figure 6 This figure illustrates a scraper 42 having a slightly different profile fromthe

scrapers

7 and 8. This scraper 42 has a notch or curved recesses 42a in the leading face of each of its scraping edges. This arrangement in effect sharpens the leading edges of the scrapers, reducing any tendency to crush the condensed material instead of scraping it, and thereby reducing the power requirements of the condenser. There may be some slight tendency for condensate to accumulate in the notches 42a, but in general it is swept out effectively by solid condensate particles which break off in front of the advancing scraper edge. Note that a scraper having the profile shown in Fig. 6 may be used only in one direction of rotation, as indicated by the arrow. The more general scraper profile shown in Fig. 5 may be rotated in either direction, as long as both of the scrapers rotate in the same direction.

It will be noted that with the basic design of Fig. 5, the angle of contact between the tip of one scraper and the condensate layer on the other scraper ranges between 0 and 90 twice for every complete revolution of the scraper. The angle of contact between the scraper tip and the cooled condensing surface of the shell is a constant 45. At no point, however, in either path of the scraper tip is there any tendency to compress the condensate, and effective removal of condensate is achieved at all localities, by a combination of shearing and wedging eifects. Although the scraper shape of Figs. 1 to 5 has been found satisfactory, the structure of Fig. 6 has (as explained above) certainadvantages, including some reduction in power requirements to turn the scrapers through some regions where the contact angle between Tests have beenmade with apparatus of the type described in Figs. 1 to 5 with the scrapers rotating alternately in opposite directions, i.e., both first in one direction and then in the other, reversing the scrapers every two minutes. Tests have also been made successfully with the scrapers operatingcontinuously in one direction.

In one test the direction of rotation of the two scrapers was reversed every two minutes with an off-period of five seconds. The condenser and scrapers effectively condensed and converted to powder form aluminum chloride vapor (i.e. aluminum trichloride, AlCl at the rate of pounds per hour for 6.5 hours, 200 pounds per hour for 5.8 hours and 300 pounds per hour for 4.3 hours, all at an absolute pressure of 100 mm. of mercury.

In a second test, the scrapers were operated continu-' ously in one direction condensing 200 pounds of aluminum chloride per hour for 4.3 hours and 300 pounds per hour for 4.3 hours. the two scrapers while condensing300 pounds per hour of aluminum chloride at 100 mm. absolute pressure ranged from 1.2 to 1.4 kilowatts. After these tests only a light scale of. aluminum chloride was observed to cover the scrapers and the inside of the condenser shell. The product appeared to be entirely powder form. The scrapers were free to move and were easily set in motion by hand or by the motor drive. Operation of the scrapers was smoother when reversing direction of rotation every two minutes as compared to. continuous rotation in one direction only.

It will be understood that the dimensions of the condenser and of the scraper elements may vary considerably with requirements of use. It is particularly desirable, however, that the condenser be of relatively elongated shape, for example such that the vertical length of each scraper is equal toat least several times (for instance, six to twelve times) its major transverse axis. By way of example, the condenser utilized in the above tests, which Was essentially as shown in the drawings, had a shell in which the inside diameter of each segment was ten inches and the total length of each scraper was approximately 7 feet 8 inches, being constructed of three endwise-abutted sections of equal length.

Although the theoretic proportioning of the scrapers and the enclosing shell is as shown in Fig. 5 and mathematically defined hereinabove, it is preferable to provide a small clearance between the scrapers and between each scraper and the shell. For example, in the specific device described above, the centers of the shafts upon which the scrapers were mounted were separated by a distance of approximately inch greater than half the sum of the major and minor transverse axes a and b of the scrapers, while the internal diameter of each of the cylindrical segments of the shell was about A.- inch greater than the major transverse axis a of the scraper.

It may also be noted that where appropriate clearances are afforded, as of the order stated, it is permissible and even advantageous because of the clearance, to adopt a slight departure of the scraper contour from the precise mathematical relationships above. Thus in the described embodiment of the equipment, the major transverse axis a of each scraper was 9.842 inches and the minor transverse axis b had a length of 4.532 inches. While the spacing of the shafts, which was 7.25 inches, represented a distance equal to half the sum of the transverse scraper axes increased by inch clearance, it will be noted that the length of the minor axis, relative to the major axis, is slightly larger than the theoretical formula requires. venient to design the scraper sides with a radius of curvature of 6.477 inches, which is a little shorter than would .bederived by theory from the value of the major axis a.

These values nevertheless represent substantial compliance with the defined proportions, varying only a minor The power input required to drive.

By the same token, it was found conway and "for structural or operating convenience in minorrespects. As the tests showed, moreover, the clearances actuallyfembodied in the device were in no way detriv These-figures illustrate diagrammatically, a method of determining those dimensions. of the scrapers which establish the clearances between the scrapers, and between each.

scraper. and the condenser wall.

By selectingthree clearances more orless arbitrarily, all other dimensions of the scrapers may be determined; Those three clearances are: C the clearance between the tip of each scraper blade and the cylinder wall (Fig. 10);

C the clearance between the edge of oneblade and the middle of one side of the other atthe time when the majorv axis of the one. blade is aligned with theminor axis of the other (Fig. 10); and C the clearance between the edgesof the blades when'both blades are at an angle of I 45 with respect to the line between the. blade centers (Fig- 11.).

In a condenser having an, inside diameter. of 10.000 inches,thefollowingclarances were selected:

C =0.0781 in. C2=O.62'5 in; C =0.288 in.

Considering the dimensions a, b, D and R, defined in connection with Fig; 5 above, as being, the theoretical (no:

clearance) dimensions, the respectively corresponding-actualdimensions, a, b, D and R, .may then be deter-; mined fromthose theoretical dimensions and the clearances selected, accordingto .the following equations:

These equations may be derived mathematically from the geometrical relationships illustrated in Figs. 5, and 11.

While I have shown and described a preferred embodi ment of my invention, other modifications thereof will readily occur to those skilled in the art, and I therefore intend my invention to be limited only by the appended claims.

Iclaim:

l. A condenser for fluids which'condense' to the solid state, comprising a vertically elongated shell having a cross-section in the shape of a pluralityofi abutting generally circular segments, each segment being greater than a-serni-circle, a corresponding plurality of vertically elongated scrapers,-eachconcentric with-one of said segments andextending lengthwise of said shell, each scraper being defined by two curved surfaces extending vertically throughout the full' length of each scraper; and each scraper having a cross-section whose contour is generally lens-shaped-and is defined by two-arcs having radii approximately equal to the distance between the centers of said segmentsand having centers of curvature at diametrically opposite points approximately on the circumference of the circles of said segments, means connecting said scrapers in an angular relationship suchthat the major axes of the cross-sections of the scrapers intersect at an angle of 90. in space, means for rot'ati'ngsaid scrapers in the same direction, .the edges ofeach scraper contacting the vertical inner surfaces of the shell and the vertical surfacesof the other scrapers and being effective during such rotationto scrape the inside of its associatedshell segment and the vertical surfaces of the other scrapers,

- to remove condensed material from the shell and'the scrapers, fluid inlet means adjacent the upper end of the saidshell for admitting fluid to the parts of the shelllon bothsides of each scraper, heating jacket means on the outside of the shell adjacent the fluid inlet means and effective to maintain the temperature of the fluid in the shell adjacent said inlet means above the boiling. point of the entering fluid and thereby inhibit deposit of condensed material in the inlet means, cooling jacket means,

on the outside of the shell below the inlet means and the heating jacket means and effective to cause condensation on the inside surfaces of the shell, fluidoutlet means adjacent the bottom of the shell and below said'cooling" 3. A condenser as defined in claim 1, in which said scrapers extend above said inlet means, and'said inlet. means comprisesmeans defining apertures in the shell,

and means defining apertures extending through said scrapers at the levelof said shell apertures, said heating.

jacket means being effective to inhibit deposit of condensed'material in all said apertures.

4. A condenser as defined in claim 1, including shafts for supporting said scrapers, each said scraper comprising a plurality of aligned sections separately attached to said shaft.

5,. A condenser for fluids which condense to a solid state comprising a vertically elongated shell having a cross-section in the shape of two abutting generally circular segments, each segment being greater than a semicircle, two vertically elongated scrapers, each concentric with one of said segments and extending lengthwise of said shell, each scraper being defined by two curved surfaces. extending vertically throughout the full length of;

each scraper, and each scraper having a cross-section whose contour is generally lens-shaped and is defined by two arcs having radii approximately equal to the distance between the centers of said segments, each said scraper cross-section having a major axis approximately equal to the square root of 2 times said distance-and a minor axis approximately equal to the square root'of2 minus 1 times said distance, means connecting said.

scrapers in an angular relationship such that the major axes of the cross-sections of the scrapers intersect at an angle of in space, means for rotating said scrapers in the same direction, the edges of eachscraper contacting the vertical inner surfaces of the shell and the vertical surfaces of the other scraper and being effective during.

suchrotation to scrape the inside of its associated shell segments and the vertical surfaces of the other scraper, to remove condensed material from the shell and the scrapers, fluid inlet means adjacent the upper end of said shell for admitting fluidto the parts of the. tube on both.

sides. of both scrapers, heating jacket means on the outside of the shell adjacent the fluid inlet means and eflective to. maintain the temperature of the fluid in the shell adjacent surfaces'of theshell, fluid outlet means adjacent the shottomof the shell and below said cool-ingjacket meansand a condensate trap at the bottom of the shell.

6. A condenser for fluids which condense to the solid state, comprising shell means having vertically elongated upright condensing surfaces cross-sectionally definedin general by. the external portions of a plurality of intersecting circles having center spacing equal approximately to the circular radius multiplied by the square root of two, upright vertically elongated scrapers having a cross-sectionally lenticular shape and defined by two curved surfaces extending vertically throughout the full length of said scrapers and disposed in the shell means to rotate on central axes substantially at the centers of the circles, means mounting the scrapers for simultaneous rotation in the same direction and in an angular relationship such that the major axes of the cross-sections of the scrapers intersect at an angle of 90, said scrapers being shaped so that their edges contact the vertical inner surfaces of the shell and the vertical surfaces of the other scrapers and collectively scrape all said condensing surfaces and all upright surfaces of each other during rotation, inlet means for directing fluid from which solid is to be condensed vertically lengthwise in the shell means on all sides of the scrapers, heating jacket means on the outside of the shell adjacent the fluid inlet means and effective to maintain the temperature of the flud in the shell adjacent said inlet means above the boiling point of the entering fluid and thereby inhibit deposit of condensed material in the inlet means, cooling jacket means on the outside of the shell below the inlet means and the heating jacket means and effective to cause condensation on the inside surfaces of the shell, and collecting means 'for receiving condensed solid material removed and falling from the aforesaid condensing and scraper surfaces.

7. A condenser for fluids which condense to the solid state, comprising an upright vertically elongated shell having a cross-sectionalcontour generally defined by the external portions of a plurality of intersecting circles, a corresponding plurality of vertically elongated scraper elements disposed to rotate on upright axes substantially concentric with said circles, each scraper having a generally lenticular shape in cross-section, constituted by two curved surfaces extending vertically throughout the full length of said scrapers and intersecting to provide substan- 10 tially diametrically opposed scraping edges, the cross-section of each scraper having a major axis from edge to edge and a minor axis perpendicular thereto, the radius of each circle of the shell contour being approximately equal to half the major axis of the corresponding scraper, and the centers of the said circles being spaced by approximately one half the sum of the major and minor scraper axes, means mounting the scrapers for simultaneous rotation in an angular relationship such that the major axes of the cross-sections of the scrapers intersect at an angle of said scrapers being shaped so that their edges contact the vertical inner surfaces of the shell and the vertical surfaces of the other scrapers and collectively scrape all upright scraper andv inside shell surfaces during rotation, inlet means for directing fluid from which solid material is to be condensed vertically lengthwise in the shell on all sides of the scrapers, heating jacket means on the outside of the shell adjacent the fluid inlet means and effective to maintain the temperature of the fluid in the shell adjacent said inlet means above the boiling point of the entering fluid and thereby inhibit deposit of condensed material in the inlet means, cooling jacket means on the outside of the shell below the inlet means and the heating jacket means and effective to cause condensation on the inside surfaces of the shell, and means at the foot of the shell for receiving condensed solid material removed from the scraper and shell surfaces.

References Cited in the file of this patent UNITED STATES PATENTS 410,356 Fakes Sept. 3, 1889 1,412,115 Hippenmeyer et al. Apr. 11, 1922 1,868,671 Nelson July 26, 1932 2,159,463 Voorheis May 23, 1939 2,472,362 Barnebey et a1 June 7, 1949 Read July 19, 1955