US2168362A - Evaporating apparatus and method - Google Patents

Description

Aug. 1939.l

QEVAPORATI'NG APPARATUS ANDy METHODv Filed Jan. 29, 195s ATTORNEY.

D; p. PEBLES ET AL`- 21,168,352

, UNITED-STAT .Patented Aug. 8, 1939 VThis invention Vrelatesgenerally toV apparatus e andlrnethods for the concentration fo! various liquid materials. containing one or more vaporiz-` able` components. in `tvvo Vorf more evaporating l Vveffects. or ystages It particular application "where the quid material t0' be evaporated. Goni:

tains organic` ingredients. such as or products, fruit juicer and the like'.

'16 .apparatus and.. ,method o!" Vthe above `\cha`.'ractex `Vwhich `will' be characterized vby" emcient evapora-- tion in a second or subsequent evaporating 'effectaf q irrespective of the fact that thev liquid niaterial ingfhandled' is more concentratedfjthan the l! `liquid fed into the iirst eilect. l l h Another object f the'invention iste-provide a multiple effect evaporator ofthe vapor-@mist.u type, whichmaintains the .desired character o!l .evaporating action as the liquid beconies incre Npconcentrated.. Y

Another 4object of theinvention i'sto provideA an evaporating apparatus and mthod'whiclr will; be characterizedbytheexistence of a relatively smallamount of liquid'being' concentrated in the*` systemat' any onetime This charaeteristic'is vof advantage in handling inaterial such asmillr products or fruit juiceawhich are aptto beinf Jured by prolonged heating. l

Another rbject of theinventlon is to provide a .N multiple eect evaporator in which a'single pass of -the liquid through the `diflkreiit, eilectsfwill suiiice to produce a relatively high degree of concentration.- I

. `Further objects oftheLinve'ntion will I vi'rom the following description, in whichfthe pre- Ierred embodiment or theinventionhas been set forth in detail in coniunction with the accom- L panting vThe"apparatus*illustrated in the .40 affords two evaporatingaeilects'or stages,` each of which utilizes evaporating "tubes: through `which t the liquid material being evaporated iscaused to.` pass. A vapor-mist type of" evaporation is utilized, such as is disclosedinour coe-pendingapplill cation Serial No.`14,300.-ledApril 2, 1935. The

iirst eiect utilizes oneheater I. while the second 1eilect utilizes the .two heaters 2gand 2b. f

t Heater I consists o! a plurality oi*r evaporating tubes l, vwhich. have their ends secured to the I -upperand lowertube sheets-I and'v. "'Thel tubes 1. f or substantially .theirentire length; are surrounded by the jacket 6.1 Within' the jacket l the'tubes 3 are surrounded by a conduit l forming in effect a cylindrical baille.` Thel lower annulmena4 wan ser the :geheten attacnedto conduit Land a lower extension of they conduit is'att'ached tothe 'tubesheet E LTh'e upper annun larend wall! of the-steamjacke'tpis shown at- ,l

,tached'to-an extension III; -whiclr in :turn: is se whereby"steaniintroduced intofthe jacket iiows Y v upwardly through thespace I hand then jdown- AIt is an lobject .ofthe invention to provide an thel upper .ends .of .the evaporatirigA tubes I. Pipe Il is shown for introducing liquidto be evapor- ,atedvinto the headz'l2, andis shown connected to ll the outletof apreheater -Ila."y

` The 'mist of liquidand vapor discharged from l the loweruends of `the evaporatingytubes Us delivered intoA a separating 'and i. collecting receiver I 4.0 Depending -conduit` I 6, `which extends-downf. n

wardlyfrom the lower tube sheet Ifserves to conf neet this receiver withthe heater I Immediately below the lower. end ofconduit` lthere is an inclined entrainmenttray I'Lwhich aids-in elIect-` ing `separation `between'liquid audyapcqr.v Vapor s similar tothe heater I described above. However.v -for reasons to be presently explained,`the crosssectional .-iiow area. affordedby the tubes-lais p made substantially lessftha'ri the erom-sectional tlovv areaof the tubesl` torheater I.l This can be donefby utilizingtubes lof 4the saine` internal diameters for'fboth'lieaters, with ya substantially fewer 4number of-'tubes la? so that the combined cross-sectional iiow area will besubstantially less. -40 f Itcan alsobe'accomplishedby using substantially the same-number `of tubes as compared with the number ottubes for heater I but with `the-tubes lo fbeing otfasubstantially'smalier internal diamete'r.` connection, good resultshave 46 been securednby making the total cross-sectional iiow area afforded by tubes Saabout 60%y ofthe crossfsection ow area afforded 'by the'tubes I mr the njrst heater. Heater 2b can be a duplicate of'heate'r 2d.' Becausefof thesmaller cross-sec-` 50 tional flowv areaaordedbyl the `tubes la and .3b

of these two heaters. Ait is evident that lthe remaining parts of these heaterscan be ot reduced size,as comparedzwiththeheater I.

IInstead `ot providin separatecollecting and separating receivers for the two heaters 2a and 2b, a single receiver 2'2 is`provided. This re-` ceiverreceives liquid and vapor from the two heaters, through the conduits Ila and `lllaand is 5 provided with entrainment trays Ila and IIb.

Baile plates 2Ia and 2lb are also shown, to prevent entrainment of liquid particles with the vapor withdrawn through conduit 23,.y A baille 2| segregates -liquid collectedcin the lower part of receiver 22, whereby the liquid components vdischarged from the tubes la and lb are not allowed to intermix, but are 'separately collected and separately withdrawn through the pipes, and 26. Y Y uA The additional equipment and connections ,il-

lustrated in the drawing are las followsz-Steam is admitted to the jacketv l of:k the iirst yheater I through pipe 21. Where it is desiredtoutilize -steam from a high pressure source, with admisn sion of ysteam tothe heater-I at a relatively lower pressure, a de-superheater 28 is employed, which is connected-toga high-pressure steam f pipe 2l,

f to suitable pressure reducing means.. Condensate is shown beingwithdra'wnfrom the llrst heaterk I through pipe and-condensate Dump 3l. A v

part of this condensate can be sprayed intothe de-superheater 21, as indicated by Pipe I2.` Pipe Il, which' receivesliquid from the receiver Il,... is shown. connected to the inlet side of a pump l so 22 which has its` discharge side connected by pipe Il to the headV I2a of heater 2a. Conduit Il,V

through which vapor is withdrawnirom the receiver Il, is shown connected to the Jackets offthetwo. heaters 2a `and 2b. Thus theV 3s supply vapor to the" heaters 2a and 2b` is vapor evolvedfrom the liquid `being evaporated in the-nrstellect, and is vapor underlike temperature and pressure conditions. Such an ar- Vrangement can be termed parallel heating, oi' the 40 second eilect heaters.'

VPipe 2l, through which liquid collected from the heater 2a is'withdrawn, is shown connected to the inlet side of a pump Il, the discharge side ofwhlch isconnected-,by pipe- 36 to the vhead I2b g of heater 2b. Pipe 2l, which receives liquid discharged i'rom"heater' 2b, connects Lto the inlet side of a pump l21,?the discharge side of which connects with a pipe Il for final delivery. 'Con' Vvdesate from both the heaters2a and 2b is shown "w being withdrawnthrough pipe-,29 and 4| to the condensate pump 42. Pipe `is shown communicating with all oftheheatcrs I, 2aand2b, and leads tol suitable evacuating means for the removal of non-condensables;` Vapor conduit 23 which connects to the'receiver 22, -leads to a suitable condensing apparatus whereby ,a desired degree ofrvacuum can bemaintained.` Y

Operation 'oi the apparatus described above, and the carrying outof the method involved, are

"n as follows--The liquidv tobe evaporated, after being heatedto a predetermined temperature,

is conveyed through pipe Il to the head I2 of the first heater I. In passing through this headand into tubes 3 thel preheatedliquid is converted 'u by a primary evaporation, dueto the maintenance inheaterl of apressure lower than the vapor pressure of the liquid,into fa .highly dispersed highly dispersed mist through the length of the tubes is enected by the primary flash evaporation and by the continued evaporation in the tubes by the transfer of heatl therein to the primarily formed vapor-liquid mixture in whichthe volume 5 of the vapor is suillciently large compared to the volume of liquid to hold the liquid mist particles in dispersion. It will be evident that the dlscharge 'from -the lower ends of tubes l3 will consist of vapor vand entrained mlstparticles of 10 liquid.

'Ihe partially evaporated liquid separated outfr in the receiver Il is delivered by pump 33 to the heaterl 2a of the second eect. In flowing down- 31 it is of the concentration 'desired'.-

Dueto the concentration occurring inthe ilrst eiect, it is` evident that the liquid supplied to the y second effect is considerably smaller in volume" vand in most instances it is of higher viscosity'lf Il", such partially concentrated liquid werel passed f through a single heateriormi'ngthe second effect,

having .tubes aiording 4the lsame cross-sectional ilow area as inthe heater of the ilrst v ellect, itwould not `be possible to attain'the'degreeolhigh concentration desired, without decreasing the volume otliquid supplied tosuch a low point, in 35 comparison with 'the cross-sectionaly flow area aftordedbythe ,evaporating tubes, that incrustation ofthe tubes would result and the rate of heat transmission j to the liquidl would be lowered.

However, with two heaters such as described, each 40' having a considerablysmaller number oi tubesV v than the heater of the'ilrst effect, to afford less aggregate cross-sectional ilow area, a greater quan'- tity of liquid is caused to pass through'eachti'ibeA It has been found 'that `as the liquid: material 45 becomes more concentrated, more elcient evaporationl is obtained without incrustation, when the quantity of liquid `supplied to each tube is in| creased. .This can be better explained by pointing out that in general as the liquid material becomes: more concentrated, its surface tension I and viscosity increases, and more energy is required to disrupt the' liquid into kline mist par` ticles.. 'Such mistA particles are desired inorder to afford a high rate ot heat transmission ands to' 5g" avoid yincrustation. Suchy iactc'rsare taken in account in the presentinvention by avoiding a decrease in the amount. oi.liquid in any; oneftube of ,the second eflect,; for a given instant, below a minimum value suchv as Vwill be found to, cause l11n-,'00A

set of conditions presented'. Because of the'man- 7o ner vin which evaporation ,is`conducted, and particularlybecause ofthe manner in vwhich concentrated liquid x'riateriall is'1 handled inthe second eilect, a hi'ghrdegree of concentration is ob- I tained in @minimum number of eects and with- '75 aeoondlop firewire vnone'lifn rete eiieotive to mnintain the pressure thereinflover l'unjin said vlo 6.,'In e'prooeu tor'he oofuoentntionot liouids; f the(` Item A'intwducinz the liquid to .be into d :one oi-llower pressure than nponpreesure oi' thelliqu'id whereby thee-liquid in converted into a les-liquid mix-l ture.V fusing mici mixture n heating none in which further ehpontionfof the'li'qmd'takes Piece; xnixhxreinto 'nf-second low mue oi' lowerpresure thin the 5first mue.V the'. liquidirom'kthe the separated juquid: nhrouzna A:mecum: neming v zone in whichfurther evapont'ion of the liquid takesrplaoe, returning themixture-of liquid and vspor thereby produoedto said secondlowpressure zone,-sepa`ratin. the liquid yfrom* thevaporj in-nid'seoond low pressurezonef-removinz seid liquid sepmtely from imeftirsi;l liquid and from the vapor,|.nd removing the vapor from: secondvlow. lpressure zoneat `s. .rate

than in said first low 'pressure zone.

e 'nAvm DIPEEBLES.' n .Munn v. miNNmG. l n

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