US1004686A - Apparatus for multiple-effect vacuum evaporation. - Google Patents

Description

H. H. DOW. APPARATUS FOR MULTIPLE EFFECT VACUUM EVAPORATION. APPLICATION FILED DBO. 26,1907

1 94,686. Patented Oct. 5, 1911 2 SHEETS-SHEBT 1.

H. H. DOW. APPARATUS FOR MULTIPLE EFFECT VACUUM EVAPORATION APPLICATION FILED DEC. 26, 1907.

1,004,686, Patented Oct. 3, 1911.

Z SHEETSSHEET Z.

kg" 992241? f/ ill @TllEi's HERBERT H. DOW, OF MIDLAND, MICHIGAN, MIDLAND, MICHIGAN, A

COMPANY, OF

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ASSIGNOR TO THE DOW CHEMICAL con-Pokemon or MICHIGAN:

APPARATUS FOR MULTIPLE EFFECT VACUUM EVAPORATION.

rooaeee.

Specification of Letters Patent.

Patented Oct. 3, 1911.

Application filed December 26, 1907. Serial No. 408,179.

'Midland, county of Midland. State of Michigan, have invented a-new and useful Improvement in Apparatus for Multiple- Ellect Vacuum Evaporation, of which the following is a specification, the principle of the invention being herein explained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

As indicated, my invention relates to apparatus for evaporation by vacuum process.

Said invention has more particular regard to the improvement of apparatus of the above class known as multiple ctlect vacuum apparatus, in which the steam arising from the evaporation of a quantityccf solution thus held under reducedpressure, is employed to heat an additional quantity of the solution, the object of the invention being the provision ofapparatus of this sort that will be simple and economical in operation, utilizing a single pump in the production of a vacuum in a plurality of chambers.

To the accomplishment of this and related ends said invention, then. consists of the means hereinafter fully described and particularly pointed out in the claims.

The annexed drawings and the following description set forth in detail certain niechanism embodying the invention, such dis: closed means constituting, however. but one of various mechanical forms in which the principle of the invention may be used.

In said annexed drawings: Figure 1 represents in more or less diagrammatic form, portions appearing in cross section, a plant for double elfectvacuum evaporation embodying the several improvements comprelumdcd in my invention: and Fig. 2 similarly shows apparatus designed for triple clleot. evaporation.

The apparatus thus chosen for illustrative PUIPUSQS is primaril designed for the evaporation of salt brine. but may be used equally well, either in its present or in slightly modified form. for the evaporation of sugar syrup or anv other solution from which it is desired to so] rate the solid, or for the concentration of liquors from which the Hilld does not separate on concentration. The illustrated apparatus is furthermoredesigned to carry out an improved process in the making of crystals from. solutions, particle:

larly salt brine, that forms the subject- Inatter of a co-pending application filed by me November 11. 1907, Serial No. 401,580. Such apparatus, then, consists essentially of a plurality of open evaporting pans A A, there being two here shown, tho-"second of which is elevated slightly above-the first so that its liquid contents may be passed on to said first pan by gravity. The process of making crystals above referred to involves, .in addition to such flow of the brine, a transfer of the salt separated from the more highly concentrated solution, in the first pan to the less highly concentrated solution in the second pan. To this end the \vall (a of such first pan A. contiguous to the second A is inclined and a conveyer a provided to gather the salt as it settles onto the bottom and carry the same up such inclined side whence it is deposited or dropped into the second pan to be carried through the latter by a corresponding conveyor (L2 operating in such pan. The latter pan has also an inclined discharge end either connected with the succeeding! pan or with conveying means (not shown). for removing the product to any desired point. Suitable connections (1? a respectively provide for a supply of fresh hrinc to pan A, a flow from such second pan to the first pan A. and a discharge thence oi the highly concentrated solution or mother liquor. The heating of the brine in the respective pans is had by mea ns of steam coils u (2 consisting of sections of pipe disposed longitudinally of the pan and having' their ends suitably connected together. -Steam is supplied to the coils in.

the first pan from any convenient source'in the usual manner; but for the heating of the second coil the steam derived from the evaporation of the contents or" the first pan under vacuum is utilized by means now to be described.

Elevated above the respective evaporating pans are vacuum chambers ll B, which have ascending pipes 7) 5 for drawing the con-- tents from the corrcspoiuliat, pans, and descending pipes b o for discharging separated crystals. In the apparatusillustrated such discharge is had directly into the pan again. but obviously this is immaterial, and, it found desirable such discharge may be, made into a separate receptacle. as in my Patent No. 554,916. February 18, 1896. A pipe :3 conducts the steam from vacuum charnher B to the steam coil a of the second 1Q gree of vacuum, while a check valve 7) pre vents any back aid or downward movement in pipe 7). It will be observed that the lower ends of pipe 7) and 7f dip below the level of the water in the pans, as does also the lower end of pipe 7) below the level of the water in the tank I). Such pipe 6", it will be understood, is intended todrain 'away from the coil Zfithe condensation formed therein, such tank D forming a water seal and trap, since the length o't pipe 7) below the coils is made sufficient so that the vacuum therein may not draw the water in said tank I) up into the coils, but leave them free to drain into said pipe 7).

llaving thus described with what it is thought, sutlicientdetail the structure embodied in my improved'type of vacuum apparatus, its method of operation may be 'briefly set forth. Vhen the apparatus 3O started and during, its operation, brine is supplied through connection a to .pan it" and thence by connection a to pan A, the rate of such supply being so controlled, havmg, due regard to the rapidity of the evaporation, as to leave the mother liquor escaping from discharge pip'c' a of the desiredconcent 'ation. Steam is at the same time admitted into the coils at in the first pan the temperature of the brine therein being 40 raised and held a few degrees above'the boi'ling point referred to the vacuum maintained in chamber B. The exhaust pump C is now set in operation, the valve?) between the ascending pipes 7) b ofthe second vacuum chamber B'- being temporarily open. Thev immediate effect of such suction accordingly is the production ofv a vacuum in chamber 13 corresponding to theheight'ofthe column of liquid from the! point of junction of pipe 7) with pipe 7) to the level of the brine'in -pan 1\. Further pumping, by increasing i the vacuum' in chamber B, serves to raise the-c mtents of the pan A into said chamber-B without,however,varying the vacuum in chamber 13,, as will taxevidcnlt'. The level of vessel 1) being sulficiently depressed, a

counter-balancing column of liquid will rise in pipe 7) at the same time that the vacuum is produced in chamber B in the n'mnncr ust 6 set forth.

'Ttwvill be understood of course that pipe 7) constitutes in ctl'ect a barometric columnhthe'height to which the brine rlses ..in such pipe aneasurnug the degree ot vacuum in chamber it. If a series of This steam coil is furthermore c0n-' vacuum gages were connected to this pipe at intervals, the one at the top would show the highest vacuum, that at the bottom would show the lowest, and those between woulgL; show intermediate degrees of vacuum. For this reason, if the pipe b (and in the case of Fig. 2 this remark applies also to pipe If) be tapped into this barometric column at. any height, the vacuum in said pipe 6", or 71 as the case may be, will correspond in degree to that in the barometric column at the point tapped. This will be evident when it is considered that the brine in pipe 7) above the junction therewith of said pipe U rests upon such point of junction and diminishes by its weight the total vacuum in pipe 7). so that the higher-such point of junction with pipe 7), the greater the degree of vacuum in pipe 79,- and conversely.thc lower the point otcntrance. the lower the degree of vacuum in such pipe 71". As a result of the vacuum maintained in heating coils a of the second evaporating pan A. the steam "from the low vacuum chamber B is drawn therein where it heats the brine in such second pan, the water of condensation escaping into the pipe 7). V I

The height of the vacuum chamber B and the degree of vacuum maintained therein is chosen. both as to its absolute value and its relation to the height of the chamber 3 and the vacuum maintained therein, so that the temperature of the vapor coming from B will be sutiicieut to raise the temperature of the brine in A to above its boiling point under vacuum in: B.

I do notascribenovelty to the utilization of steam derived in this manner to heat the second cvapo 'ating vessel, but it will be noted that by means of my apparatus I am enabled to maintain the desired vacuum in such 'firsti system without the employment of an additional pump, or a reducingvalve, as has always been the case heretofore, so fat as I am aware. In other words a single pump connected with the high-vacuum chan'iber is, effective in maintaining" the vacuunr not merely in such chamber, but also in the low-. vacuum chamber corresponding with the first evaporating pan without the introduction of a mechanically operated reducing valve. The simplification. and cheapening ot operationthusaccomplished need not be further dwelt upon. At the. Same time it will he ol iserved-that aconstant vacuum is may vary within reasonable limits without harm so long at is. does not thus ati ect the vacuum in such first chamber. As explained in m.v Patent No. 554,916 l'iefore'referred to. the How of brine during the operation of pipe 7) up to the point of its I the vacuum evaporator B is up the pipe b and down Z).

In starting the system, I open valve 5 admitting the air and vapor from If to the ascending column of brine, by which itis delivered to the chamber B whence it is drawn out. by the pump. In order to lessen the work of the pump after the system has attained its normal working condition, I open the valve Zrgat the same time closing valve (1 thus admitting thesaid air and vapor from 1) into pipe I), where it is en trained by the descending column ot brine and is carried down into the pan and discharged to the atmosphere by bubblingup through the brine contained therein.

It should be plainly evident. without fur- -ther delineation than that shown in Fig.

1, how the double ettcct there illustrated can be extended to triple and higher multiple effects by suitable adaptation of parts. It has been deemed advisable. however. to illustrate one such modification, Fig. 2, wherein a triple etl'ect vacuum evapomtion is had. To this end merely a third open heating pan A together with a third vacuum chamber B require to be employed, these being joined with each other and with the pre ceding pan A and chamber B of the series by connections corresponding with those previously described as joining such pan A and chamber B with pan A and chamber I3. These connections have accordingly had applied to them the same reference characters and their identification thus rendered possible without further description. In this apparatus as theother,

one pump C will sutlice to maintain vacua in all of the evaporator-s, the. degree of vacuum in each being controlled by the corresponding heights at which the pipes 0" if are connected into pipes b b and 5 In the same. manner additiona effects ma y be securedas desired or found advisable. A.

In this specification, and the claims which follow, the term open as applied to the heating" vessels is employed to denote that the same are operated under atmospheric, or substantially atmospheric, pressure, in contradistinction to the prevailing practic in which the liquid being heated is subjected to reduced pressure during the heating.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the mcansstatcd by any one of the following claims or the equivalent of such stated means be employed.

l therct'ore particularly point out and distinctly claim as my invention 1* l. In apparatus ofthe class described, the combination of two open heating vessels;

vacuum chambers respectively adapted to receive the contents of said vessels; and'an exhausting device connected with the second of said chambers for maintaining the desired degree of vacuum therein, said second chamber being connected with said firstchamber so as simultaneously to maintain a vacuum therein. I

In apparatus of the class described, the combination of two open heating vessels; 'acuum chambers res )ect-ively adapted to receive the contents oi said vessels; an exhausting device connected with the second of said chambers for maintaining the desired degree of vacuum therein; and 0011-, nections between said two chambers, said connections being so arranged and constructed as simultaneously to maintain a vacuum in said first chamber, but of a lower degree.

3. In apparatus of the class described, the

combination with two open evaporating pans, steam heating devices for said pans,

and vacuum chambers respectively adapted I to receive the contentsfiof said pans, the heating device of the second pan being con-- nected to receive steam from the chamber attached to the first pan; of a pump corr nected with the chamber attached'to said second pan for maintaining the desired degree of vacuum therein, said second chaniher being connected with such heating de vice so as simultaneously to maintain a vacuum therein.

I. In apparatus of the class described, the combination with two open evaporating pans, steam heating devices for said pans, and vacuum chambers respectively adapted to receive the contents of said pans, the heating device of the second pan being connected to receive steam from the chamber attached to the first pan; of'a pump connected with the chamber attached to said second pan for maintaining the desired de-. gree of vacuum therein; and connections between said last named chamber and such heating device, said connections being so arranged and constructed sin'iultaneously to maintain a vacuum in said first named chamber, but of a lower degree.

5. In apparatus of the class described, the combination of two open evaporating pans; steam heating coils therein; an. elevated vacuum chamber for each of said pans, eachof said. chambers having an ascending pipe for drawing the contents from the corresponding pan and a descei iding pipe for discharging separated crystals, tin-: heating coils of the second pan beingiconnia' ted to receive steam from the chamber correspond ingr with the first pan; and a single exhaustinn" device adapted simultaneously to create a vacuum in such coils and in the chamber corresponding with said second pan.

(5. In apparatus of the class described, the

&

combination of two open evaporating pans; steam .heating coils therein; an elevated vacuum chamber for each of said pans, each of said chambers having an ascending pipe for drawing the contents from the corresponding pan and a descending pipe for discharging separated crystals, the heating coils of the second pan being connected to receive steam from the chamber corresponding with the first pan; a connection between such coils and theascending pipe of the chamber corresponding with said second pan; and a pump connected with said last named chamber for maintaining a vacuum therein.

7. In apparatus of the class described, the combination of two open evaporating pans; steam heating coils therein; an elevated vacuum chamber for each of said pans, each of said chambers having an ascending pipe for drawing the contents from the corresponding pan and a descending pipe for discharging separated crystals, the heating CO1lS ot the second pan being connectedto receive steam from the chamber correspond? ing w th the first pan; a connection between such coils and the ascending pipe of the chamber corres 'iondin'g with said second pan; a valve-controlled pipe adapted. to connect the descending pipe of said last named chamber with such coils; and a pump connected with said last named chamber for maintaining a vacuum therein.

8. In apparatus of the class described; the combination of two open evaporating pans; steam heating coils therein; an elevated vacuum chamber for each of said pans, each otsaid chambers having an ascending pipe .for drawing the contents from the' corre-' sponding pan and a descending pipe for discharging separated crystals, the heating cons of the second pan being connected to receive steam from the, chamber corresponding with the first pan a connection be I tween such coils-and the ascending-pipe of the chamber correspond ng with sa d second pan; a valve-controlled pipe adapted to con:

ncct the descending pipe of said last named chamber with such coils; another connection between such coils .and a receptacle. de-

pump connected with said lastlnamed chamber for maintaining a vacuum therein.

9. In apparatus of the class described, the combination'of a seriesof open heating yes- 7 sels; vacuum chambers respectively adapted to receive the contents ot said vessels;

an'd'an exhausting device connected with the last of said .clunnbers for mainta ning the desired degree ot' vacuum therein, said last chamber being connected with the remaining chambers in the series seas simultaneously to maintain a vacuum there n.

- Attcsted by- 10. In apparatus of the class described, the combination of a series of open heating vessels; vacuum chambers respectively adapted to'receive the contents of said vessels; and an exhausting device connected with the last of said ,-han'1bers for maintaining the desired degree of vacuum therein, said last chamber being connected with the remaining chambers in the series, the connections between said chambers being so arranged and; constructed as siu'mltaneously to maintain vacua therein but of lower degree in each succeeding chamber. I

llnIn apparatus of the class described, the combination with a series of open heating vessels having steam heating devices for said vessels; of a corre 'ponding series or vacuum chambers respectively connected to receive the contents of said vessels; a pump connected to the last of Sand chambers and adapted to maintain the desired :lcgrce of vacuum therein; of connections adapted to lead steam from each chamber. except the last, to the next succeeding heating device and of connections between each chamber, except the first, and the heating device corresponding thereto, said last connections being. so arranged. and constructed as to reduce in a predetermined manner the degree of vacuum in each succeeding chamber.

12. In apparatus of the c assdescribed, the combination of a series of open heating vessels ha-ving steam heating elements therein;'a corresponding series of vacliumchambers placed at serially increasing elevations respectively above the said vessels directly related thereto; connecting p'ipes adaptedto lead steam from each said chamber into the heating element of the said vessel directly related to the next higher chamber; an ex- 'liausting 1 device higher, chambgi connected tothe last and and; adapted to maintain therein thedes'red degree of vacuum; circulat-ing pipes connecting the directly relatedchambers and vessels respectively'andf adapted to circulate, the contents of the latter-through the former; watersealed drip pipes adapted to discharge the water of condensation fronrthe heatingelements' when Working under vacuum;-and valve control led pipes connecting the respective heating elements with the responding vessels as cally reduce the initial vacuum in the highest chamber to vacua of lower degree in eachsucceeding lower' chamber.

:nnnnnar it, now."

[ S-i'gnediby me this 25' day of November,

- Tno'sa G inswonn, E. O. B'Aas'row.

, directly related circulating pipes at such elevations above their corthereby .toautomatt

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