US2488598A - Flash evaporator - Google Patents

Description

Nov. 22, 1949 c. J. LocKMAN FLASH EVAPORATOR Filed Oct. 3l, 1945 Patented Nov. 22, 1949 FLASH EVAPORATOR Carl Johan Lockman, Enebyberg, Sweden, as-

signor to Aktiebolaget Rosenblads Patenter,

Stockholm, Sweden Application October 31, 1945-, Serial No. 625,783 In Sweden September 20, 1943 The present invention refers to evaporating apparatus and more particularly to such apparatus as the ash evaporating type working with circulation of the liquor to be evaporated through a heat exchanger and a ash chamber, and in which the heat exchanger is so operated for cleaning purposes that the liquor and a heating medium are passed alternately through changed channel systems.

In this kind of apparatus it is important that the change of the liquor stream from one to the other channel system of the heat exchanger does not cause any loss f the liquor body which is contained in the liquor-conducting channel system 'before the change but that all the liquor should be carried in circulation also after. the change and that this should be'secured by suitable measures for the change.

With this in viewfit is the chief object of the invention to provide arrangements whereby it is rendered possible to force the liquor remainingin one or the other channel system of the heat exchanger when a change is desired to be passed back towards the flash chamber the same way as previously entered therefrom so that also this liquor body may then be included in the circulating flow through the changed channel system.

By way of example one embodiment of an apparatus according to the invention is illustrated in the accompanying drawing which more or less diagrammatically shows a side view of such apparatus.

In the drawing I is a flash chamber and 2 a heat exchanger of the plate type comprising two separate channel systems 2a and 2b with inor outlet pipes a and aa, b and bb, respectively. Further, there is provided supply means for liquor as by the pipe 3 and its branches 3a and 3b with valves a3 and b3, respectively, which are connected with the bottom ends of the channel systems 2a and 2b, respectively, over inor outlet pipes a and bb, respectively. Similarly the 2 Claims. (Cl. 159-22) top ends of the channel systems are connected through in'- or outlet pipes aa and b with discharge means for liquor as by valves a4 and b4, respectively, in branches 4a and 4b, respectively, of pipe 4. On the other hand the liquor supvply and discharge pipes 3 and 4, respectively, are connected with' the flash chamber I so as to form a circulating path for the liquor which may thus be passed. from the flash chamber through pipe 3 and either of its branches 3a or 3b through channel system 2a or 2b, respec- 2 pipe 4a or 4b, respectively, and pipe 4 back to the flash chamber again. Likewise heating steam may be fed to any one of the channel systems by means of a corresponding supply and discharge system comprising pipe 5 with branches 5a and 5b and valves a5 and b5, respectively, for supplying steam to the top inor outlet pipes aa or b, respectively, of channel sysstems 2a and 2b, respectively, as desired, and branches 6a and 6b with valves a6 and h6, respectively, of pipe 6 in connection with the bottom inor o utlet pipes a and bb, respectively, for discharging condensate from channel sysstem 2a or 2b as the case may be. In addition there is a pipe 1 with a shut-off valve 'Iv Y connected with the steam supply pipe 5 between a shut-off valve 5v in that pipe and the branch' pipe valves in order to admit the introduction of compressed air or gas and the like in the channel systems'of the heat exchanger, if desired.

Now, as indicated in the drawing by arrows it is assumed that the liquor to be evaporated circulates from the flash chamber through pipe 3 and branch 3a, valve a3 being open and valve b3 being closed, and thence through pipe a to the channel system 2a in heat exchange Valve a6 being closed. From channel system 2a the liquor flows through pipe aa and branch 4a, valve a4 being open and valve a5 being closed, and thence through pipe 4 back to the the evaporator, valve b4 being closed. At the ,same time steam is fed through pipe 5 and the open branch 5b to the channel system 2b in the heat exchanger, from which channel system the condensate is discharged through the open branch 6b and pipe 6. Thus, in the heat exchanger the liquor is heated by heat transmission from the steam and this occurs under higher pressure than prevails in the flash chamber, and therein the pressure is relieved so that eva-poration of the liquor will take place, the vapours escaping to .the top to be withdrawn by a discharge pipe therefrom and the liquor forming a pool in the bottom space from which it is circulated again.

When it is desired to effect interchange of4 media between the channel systems this may conveniently be carried out in the following manner. First valve b5 is closed to shut oil the steam supply to the channel system 2b. Valve a5 is opened in order to direct the steam to the channel system 2a and valve a4 is closed to prevent the steam flowing directly to the evaporatoi` I. Since the steam ofcourse has a somewhat higherV pressure than the liquor in that channel,

tively, as desired, and through either branch the steam tends to force the liquor out of the /ing body as desired, the invention eens for an arrangement which includes a suitable positioning of the heat exchanger relative the flash chamber whereby such a relation between the counteracting pressures referred` to is estab- 1. In an evaporating system, a surface heat exchanger having a wall separating two fiuidpassages in heat exchange relation with each other. .a flash chamber disposed at a higher elevation .than said heat exchanger, a first conduit connected to said ash chamber, branch conduits connecting said first conduit'with one end of each of said passages, a second conduit connected i to said iiash chamber, branch conduits connectlished so that the liquor level will be caused to fall below the liquor in-let'to the channel system 2a. Generally, the heat exchanger should be positioned at the lowest suitable level so that circulation is facilitated as much-as possible.

However, sometimes local conditions or other considerations may' not allow such positioning of the heat exchanger-as proposed and in that case,

there may be needed a medium of higher pressure than the heating steam to displace the liquor from the respective 'channel system in the manner described. To this end the invention provides. for introduction of compressed air, gas or thelike of suitable pressure into the channel system through pipe 'I by opening valve 1v, after closing valve 5v, for displacing the liquor before the heating steam is admitted to same channel system. Y

After the liquor in the channel system 2a has been displaced by the heating steam, valve a3 is manner described', the heat exchanger will be' kept practically clean while in uninterrupted operation and continually maintained at very high eiliciency.L i l It is understood that various changes may be made in the apparatus shown and methods described without deviating from thel scope of the invention which is not limited otherwise than by the appended claims. l What I claim and desire to secure by Letters Patent is: y

ing said second conduit with the opposite end of `each of said passages, a third conduit for supplying-a heated iluid medium under pressure, branch conduits connecting said third conduit to said opposite end of each of said passages, a fourth conduit for discharging cooled heating medium, branch conduits connecting said fourth conduit ,to said one end of each of said passages, and a valve disposed in each of the aforesaid branch conduits and operable to permit flow of fluid from said flash chamber through either of said passages and back to said chamber while permitting flow of heating medium from said third conduit through the other of said passages and to said fourth conduit, said valves also being operable to permit owof fluid under pressure from said third conduit into the opposite end of the same passage whichis connected to said ilash chamber by said first conduit, whereby fluid is forced back from said same passage to the higher elevation in said flash chamber.

2. An evaporating system as defined in claim 1 including a fth conduit for supplying a gas under pressure, and a valved connection between said fourth and fth conduits whereby the pressure of said gas is utilized to force the fluid back from said same passage to the higher elevation in said flash chamber.

CARL JOHAN LOCKMAN.

i REFERENCES CITED,

The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,006,197 Frasch Oct. 17, 1911 1,819,517 Lichtenthaeler Aug. 18, 1931 1,997,980 Smith Apr. 16, 1935 FOREIGN PATENTS Number Country Date 363,116 Great Britain Dec. 4, 1930

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