US2257531A - Evaporating apparatus and method - Google Patents

Description

Sept. 30, 1941. D. D. PEEBLES 2,257,531

EVAPORATING APPARATUS AND METHOD Filed Aug. 8, 1938 2 Sheets-Sheet l INVENTOR mwa a. pff-5.1.55

ATTORNEY.

Sept' 30, 1941- D. D. PEr-:BLl-:s 2,257,531

EVAFORATING APPARATUS AND METHOD Filed Aug. 8, 1958 2 Sheets-Sheet 2 INVENTOR aA wa a. Punts ATTORNEY.

Patented Sept. 30, 1941 UNITED vspares PATENT oFF ICE 2,257,531 EvAPonA'rING APPARATUS AND ME'rnon David D. Peebles, Berkeley, Calif. Application August 8, 1938, Serial No. 223,683

9 Claims.

This invention relates generally to apparatus and methods for the concentration of various liquid materials containing one or more vaporizable components In Peebles and Manning Patent No. 2,090,985, there is disclosed an evaporating apparatus and method 'of the vapor-mist type. The evaporating tubes in that instance are arranged so that their upper ends receive the material to 'be evaporated, and the evaporating cycle is such that evolved vapor together with dispersed liquid particles ilow at high velocities through the evaporating tubes. Such an evaporator is particularly suited to the handling of organic materials sensitive to heat treatment, because it makes possible rapid concentration by evaporation, with a minimum volume of the material within the evaporating cycle at any one time, and with a minimum time period of heat treatment.

I have found that when certain organic pulps containing suspended solids of a brous nature, like tomato juice, are to be reduced to paste-like concentrates, the evaporator as specifically disclosed in said Patent No. 2,090,985, may not be entirely satisfactory, particularly for the higher concentrations. This is attributed tothe viscosity of such materials, particularly when concentrated, which makes it diiiicult to distribute the material into the various evaporating tubes, and which tends to cause the material to plaster upon certain walls of the apparatus instead of continuing to progress through the evaporating cycle.

It is an object of the present invention to provide an improved evaporating apparatusV and method, which can be successfully employed for the concentration of materials like tomato pulps, and which will afford relatively high efficiency, and high capacity, with a minimum amount of impairment of heat sensitive properties, and with equipment of simple construction. While the apparatus and method has been devised in connection with the evaporation of materials like tomato pulp, it can be used successfully upon a wide variety of materials including substances such as black liquor.

Further objects of the invention will appear from the following description in which the preferred embodiments of the invention have been set forth in detail in conjunction with the accompanying drawings.

'Referring to the drawings:

Fig.' 1 is a side elevational view, in cross-section, illustrating evaporating apparatus incorporating the present invention.

Fig. 2 is a cross-sectional detail, on an enlarged scale, taken along the line 2 2 of Fig. 1.

Fig. 3 ls a side elevational view, showing a multiple eil'ect evaporating apparatus, making use of two units of the type shown in Fig. 1.

Fig. 4 is a cross-sectional detail showing a suitable construction for the distributing or plenum chamber.

Referring rst to that embodiment illustrated in Figs. 1 and 2, it consists of two groups of upright evaporating tubes A ends of these tubes are attached to tube `sheet I0, and the lower ends to the tube sheet I I. Surrounding the evaporating tubes A and B, there is a heater jacket I2, into which steam can be ntroduced through the pipe" connection I3. Pipe I5 serves to remove non-condensible gases from the upper portion of the jacket.

Extending upwardly within the steam jacket I2, there is a conduit or shroud I4 which surrounds the two groups of evaporating tubes. Steam introduced through pipe I3 ows upwardly within the conduit vHI and the outer walls of the jacket I2, before contacting the evaporating tubes, after which the steam ilows` downwardly about the evaporatng tubes to a point near the lower end of these tubes, where condensate is drained away through pipe I 6. Below the tube sheet II there is a separating chamber I1, which serves to `receive material discharged from the lower end of the evaporating tubes B. Pipe I8 is a vapor outlet from chamber I1, and a pipe I9 at the lower end of chamber I'I, is for the purpose of draining away concentrate. Chamber 2I is suitably secured to the lower side of tube sheet II and communicates with the inner group of evaporating tubes A. The liquid to be concentrated is introduced into chamber 2|, throughpipe 22. A baille wall 23 extends within the chamber l1, and facilitates separation of liquor from vapor.

Above the tube sheet I0 and communicating with `the upper ends of all of the evaporating tubes, there `is a chamber 24, which can be termed a plenum chamber. The purpose of this chamber is to transfer and distribute material discharged from the uplow4 evaporating tubes A, to the downfiow tubes B. This chamber 24 is of substantial height whereby the top wall 25 is considerably elevated above the upper ends of the evaporating tubes. The purpose of this proportioning is to prevent plastering of the upper Wall 25 with material discharged from tubes A,

and B. The upper terial..

since it has beenfound that such-plastering, if it is permitted to occur, prevents proper operation of the evaporator, particularly in that it makes for uneven distribution of the liquid material into the downow tubes B, and because the accumulation of such material upon the mesh wire, such as a screen of 1A; inch mesh.

These screens act in effect as a break to check 257,531 Y v l n win be'v noted from nig.v 2 that a. iarge number of downow tubes B are employed, in proportion to the number of upfiow tubes A. While the precise ratio employed can vary in practice,

it is'desirable that the cross sectional iiowarea for the downflow tubes B be 'at-least twice that afforded by the upilow tubes, because o f the large amount of evolved vapor which must pass downwardly through the tubes B.-=

In the multiple effect evaporatorV of Fig. 3, separate units similar tothe equipment described with reference to Fig. 1, are connected together to discharged material, and in addition they insure uniform distribution of droplets of liquid 'to the downilow tubes B. i

The equipment described above can be operated as a single unit at atmospheric pressures, or under vacuum. Assuming atmospheric pres-- sure, pipe I3 is connected to a suitable source.

of steam, and pipe connection I8 is permitted to discharge vapor at atmospheric pressure. 'Ihe concentrate pipe I9 is connected to some suitable means for removing the concentrate, as for example a suitable Vform of pump which will remove the liquid material substantially as fast as collected in chamber II. The material to be concentrated, suchvas tomato pulp, is preheated and then supplied to pipe 22 by a suitable pump.v

When operating under vacuum the temperature to which the liquid material is supplied'to chamlform a double effect vacuum evaporator." Thus the downfiow tubes B ofthe unit I discharge into a separator 28, similar tothe separator Il of Fig. 1. Vapor or steam from a suitable Source is supplied to the jacket of unit I, through pipe I3, while the jacket of unit `2- is supplied with vapor through the pipe connection 29, from separator 28. The liquid material to be concentrated is supplied to the unit I through pipe 3I and the v' liquid material collected in separator 28 is drained ber 2| can be such that at the pressure existing in chamber 2|, there is some immediate expansion, with evolution of vapor, although such operation is not essential. As the liquid material, together with any vapor evolved in chamber 2I, passes into the lower ends of pipes A, evolution of vapor occurs due to heat absorption through the walls of the evaporating tubes, and as a result vapor togetherf with dispersed liquid material flows upwardly at high velocities through tubes A, to be discharged into the lower part of chamber 24.

Within the chamber 24 the material jetted or blown from the upper ends of tubes A is checked by screens 26,'so that there is no plastering of the top wall 25, or of the adjacent side walls of the chamber 24. In fact the liquid material discharged from tubes A remains in more or less dispersed state, or in the form of droplets.. and immediately after discharge into chamber 24,

both the vapor and liquid components are deV livered downwardly into the tubes B. If any material is caught upon the side walls above the screens it is immediately picked up by the vapor and re-distributed into the down iiowV tubes. Within tubes B the liquid material is again subjected to evaporation to be finally discharged as a concentrate into the separator I'I.

The size o'f the evaporating equipment de-l scribed above can vary in accordance with the capacities required, and the type of material to be concentrated. In the evaporation Yof tomato pulp I have employed evaporating ,tubes about 11/4 inch inside diameter, and about 20 fe-et in length. For such an evaporatorthe chamber 24 can vary in height from say 12 to 24 inches. For any particular material to be handled one .should Amake the chamber 24 suiliciently high to avoid plastering the top wall 25 with the liquid. ma-

the pipesA of unit 2. VThe separator 34 which receives concentrate from unit 2, has. a vapor pipe connection 36 leading to a suitable condenser, while the liquid connection 31 can be connected to a suitable pump, for removing the liquid concentrate.

The multiple effect evaporator of Fig. 3' operates substantially the same as the single effect evaporator of Figs. 1 and 2. The vacuum to be maintained upon the two units is dependent upon the vacuum applied to the connection 36, and is somewhat dependent upon the type of material being treated. The chamber 24 for the two units I and 2 nmay vary somewhat in dimensions, butvin any event they are dimensloned in such a manner as to prevent plastering of the top wall 25.

In order to facilitate cleaning the top chamber I 24 structural details can be employed as shown in Fig ,4. In this instance the chamber is formed by a. cylindrical -s'hell 4I having a removable cover 42. The wire screens 43 are secured to a ring 44, whereby the screen assembly can be readily removed after removing the cover 42. Ring 4.4 may rest 'upon lugs 46 which may be positioned at-a desired elevation.

1.- In evaporating apparatus, two sets of generally upright evaporating tubes, means for introducing liquid material to be evaporated into the lower end of one set of tubes, means for receiving evaporated material and evolved vapor from the lower end of the second set of tubes, and a chamber serving to transfer evolved vapor and dispersed liquid from the upper end of the iirst set of tubes to the upper end of the second set of tubes, and a diffusion screen through which vapor and liquid is caused to pass within said chamber, said screen being disposed above the upper open ends of both said sets of tubes.

2. In evaporating apparatus, two sets of generally upright evaporating tubes, a common heating jacket for said tubes, a chamber communieating with the upper end of all of said tubes, means for introducing liquid material to be evaporated into the lower end of the first set of tubes, whereby evolved vapor and dispersed liquid owing upwardly through the rst set of tubes is discharged into said chamber and whereby all o f the liquid and evolved vapor discharged into .said chamber is immediately thereafter caused to enter the upper ends of the Second set of tubes, and a diffusion screen extending across said chamber above the upper ends of said tubes, said screen serving to check the discharge of material from the upper ends of the first set of tubes, and aiding the distribution of vapor and liquid into the second set of tubes.

3. In evaporating apparatus, two sets of generally upright evaporating tubes, a common heating jacket for said tubes, a chamber communieating with the upper end of all of said tubes, means for introducing liquid material to be evaporated into the lower end of the first set of tubes, whereby evolved vapor and dispersed liquid flowing upwardly through the first. set of tubes is discharged into said chamber and whereby all of the liquid and evolved vapor discharged into said chamber is immediately thereafter caused to enter the upper yends of the second set of tubes, and a diffusion screen extending across said chamber above the upper ends of said tubes, said screen serving to check the discharge of material from the upper ends of the first set of tubes, and aiding the distribution of vapor and liquid into the second set of tubes, the second set of tubes in comparison with the first set having at least substantially twice the effective cross-sectional flow area.

4. In an evaporating method for the concentration of pulp-like liquid materials containing suspended solids, wherein the material to be evaporated is passed at high velocities through two sets of upright heated evaporating tubes, with one set of tubes having its upper end connected to a plenum chamber which also connects with the upper ends of the second set of tubes and with the top wall of the plenum chamber overlying the upper ends of both sets of tubes; the improvement comprising causing liquid material interspersed with evolved vapor to. pass rapidly upwardly through the one set of evaporating tubes whereby a mixture of vapor and liquid material jets from the upper end of the nrst set of tubes, causing the liquid material in the Jetting mixture to lose its upward velocity before contact of the same with the top wall of the chamber, and then immediately transferring a mixture of evolved vapor and liquid material from the chamber into the upper end of the second set of tubes.

5. In an evaporating method for the concentration of liquid materials to form paste-like concentrates wherein the liquid material to be evaporated is passed at high velocities through two sets of upright heated evaporating tubes, with the one set of tubes having its upper end connected to a plenum chamber which also connects with the upper end of the second set of tubes and with the top wall of the plenum chamber extending over the upper ends of both sets of tubes; the improvement comprising causing liquid material interspersed with evolved vapor to pass rapidly upwardly through the one set of evaporating tubes and to Jet from the upper end of the tubes, checking and diffusing the jetting vmixture thereby preventing liquid material of the same from being propelled into contact with the top Wall ofthe chamber, and then causing evolved vapor together with particles of the liquid material diffused through the same to pass downwardly through the second set of tubes.

6. In evaporating apparatus, two sets of generally upright evaporating tubes, means for introducing liquid material to be evaporated into the lower end of one set of tubes, means for receiving evaporated material and evolved vapor from the lower end of the second set of tubes, a chamber serving to transfer evolved vapor and dispersed liquid from the upper end of the first set of tubes to the upper end of the second set of tubes, and means in said chamber disposed above the upper open end of the first set of tubes for diffusing and checking the ow of material discharging therefrom.

7. In evaporating apparatus, two sets of generally upright evaporating tubes, means for introducing liquid material to be evaporated into the lower end of one set of tubes, means for receiving evaporated material and evolved vapor from the other end of the second set of tubes, a chamber serving to transfer evolved vapor and dispersed liquid from the upper end of the ilrst set of tubes to the upper end of the second set of tubes, and means within the chamber disposed above the upper open ends of both sets of tubes for diffusing liquid material being transferred through said chamber and for checking material discharged from the upper end of the first set of tubes.

8. In evaporating apparatus, two sets of generally upright evaporating tubes, means for introducing liquid material to be evaporated into the lower end of one set of tubes, means for receivingV evaporated material and evolved vapor from the lower end of the second set of tubes, a chamber serving to transfer evolved vapor and dispersedliquid from the upper end of the first set of tubes to the upper end of the second set of tubes, and a diffusion screen through which vapor and liquid is caused to pass within said chamber, said screen being disposed above the upper open end of said first .set of tubes.

9. In evaporating apparatus, two sets of generally upright evaporating tubes, means for in- I troducing liquid material to be evaporated into the lower end of one set of tubes, means for receiving evaporated material and evolved vapor from the lower end of the second set of tubes, a chamber serving to transfer evolved vapor and dispersed liquid from the upper end of the first set of tubes to the upper end of the second set of tubes, and a diusion screen through which vapor and liquid is caused to pass within said chamber, said screen being disposed above the upper open end of said second set of tubes.

DAVID D. PEEBLES.

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