US3720586A - Multiple expansion flash evaporator comprising a continuous casing with a central evaporation chamber - Google Patents

Abstract

A multiple expansion flash evaporator comprising a continuous casing, with vertical longitudinal baffles dividing the casing into a central evaporation zone and two side condensation zones in communication with the central zone, a number of vertical transverse baffles dividing the evaporator into a succession of expansion chambers with flow openings between them, and a multi-tube heat exchanger running the length of each condensation zone.

Description

March 13, 1973 B. DIEGO ETAL MULTIPLE EXPANSION FLASH EVAPORATOR COMPRSISING A CONTINUOUS CASING WITH A CENTRAL EVAPORATT N CHAMBER Filed April 15, 1970 3 Sheets-Sheet 1 H, 1973 DIEGQ EI'AL 3,720,586 v MULTIPLE EXPANSION FLASH EVAPORATOR COMPRSISING A. CONTINUOUS CASING WITH A CENTRAL EVAPORATION CHAMBER Filed April 15, 1970 3 Sheets-Sheet 2 Filed April 15, 1970 13, 1973, B. DIEGO 1ETAI- I 3,720,586

MULTIPLE EXPANSION FLASH EVAPORATOR COMPRSISING A CONTINUOUS CASING WITH A CENTRAL EVAPORATION CHAMBER 3 Sheets-Sheet 3 3,720,586 MULTIPLE EXPANSION FLASH EVAPORATOR COMPRISING A CONTINUOUS CASING WITH A CENTRAL EVAPORATION CHAMBER Diego Barba, Candide DAgostino, and Giuseppe LlllZZO, Rome, Italy, assiguors to Societa Italiana Resine S.p.A., Milan, Italy Filed Apr. 15, 1970, Ser- No. 28,827 Int. Cl. B01d 3/02, 3/06 US. Cl. 202-473 2 Claims ABSTRACT OF THE DISCLOSURE A multiple expansion flash evaporator comprising a continuous casing, with vertical longitudinal bafiles dividing the casing into a central evaporation zone and two side condensation zones in communication with the central zone, a number of vertical transverse baffles dividing the evaporator into a succession of expansion chambers with flow openings between them, and a multi-tube heat exchanger running the length of each condensation zone.

This invention relates to plant for the desalination of sea or other water and more particularly to multi-expansion flash evaporators.

As is well known, multi-expansion flash evaporators consist of a number of expansion chambers arranged in series, through which flows the water that is to be evaporated. During the desalination process, the chambers are maintained at a pressure which decreases in the direction of flow of the saline solution in course of evaporation.

The shape of the expansion chambers in such equipment is highly important, as it can affect both the speed of evaporation and the purity of the product. Economy in construction is also important, in view of the size of equipment of this type, intended for the conversion of considerable quantities of salt water into fresh water.

One object of the present invention is therefore the provision of a flash evaporator of such shape and proportions as to combine high speed of operation with a high degree of purity in the distillate obtained by the evaporation of seawater, and also simple construction with easy maintenance.

The invention provides a multiple expansion flash evaporator comprising a continuous casing, vertical longitudinal baffles dividing the casing into a central evaporation zone and two side condensation zones in communication with the central zone, a number of vertical transverse bafiles dividing the evaporator into a succession of expansion chambers with flow openings between them, and a multi-tube heat exchanger running the length of each condensation zone.

To be more precise, the evaporator with which the invention is concerned may comprise:

A continuous casing running horizontally, which consists of a flat bottom, two side Walls at right angles to the bottom, and a fiat top joined to the side walls;

Two vertical baflies running the full length of the casing and enclosing a central evaporation zone and two symmetrical side condensation zones, with these baflies, which connect the bottom of the casing to the top, containing a discontinuity in which filters are fitted to trap droplets while allowing the water vapour to pass from the evaporation zone to the condensation zones;

A number of vertical baffies running transversely to the casing so as to divide it into several chambers, the lower part of these baffles in each case containing a submerged opening, the width of which does not exceed that of the evaporation zone, to permit the flow of water from chamber to chamber;

nited States Patent 3,72,586 Patented Mar. 13, 1973 Two heat exchangers consisting of a multiplicity of tubes running the entire length of the casing, arranged symmetrically in the condensation zones.

The invention is illustrated in the accompanying drawings in which:

FIG. 1 is a diagrammatic cross-sectional view of an expansion chamber;

FIG. 2 is a diagrammatic longitudinal sectional view of the chamber along the line A--A in FIG. 1; and

FIG. 3 is a mixed or composite diagrammatic longitudinal section of a three-chambered evaporator, the upper part showing the condensation zone and the lower part of the evaporation zone.

In FIG. 1, the numeral 1 indicates the continuous casing, 2 the vertical baflles enclosing the central evaporation zone, 7, and two size zones, 8, for condensation. The filters for trapping the droplets are numbered 3, while 4 is the opening through which the saline solution passes.

In the condensation zone, the nests of tubes are numbered 5 and collectors for the non-condensable components are shown at 6.

In FIG. 2, 4(1) is the flow opening, 3(2) is the filter and 10(3) the level-sill.

FIG. 3 shows the evaporator in longitudinal section and brings out, in particular, details of one of the two nests of tubes 5(1), and entry 11(2) for the solution that is to be evaporated and an outlet 12 (3) for the concentrated solution after evaporation.

For seawater desalination, the saline solution enters the chamber through an opening or fitting 11, which may also be of the sluicegate type, to enable the opening to be varied according to the duty required of the plant.

The water vapour evolved passes into the central zone 7 of the chamber, passes through the droplet filter and condenses on the nests of tubes, collecting in the bottom of the side passages or condensation zones 8.

The shape of the expansion chamber has the advantage of improving the elfectiveness of the filter separators, apparently due to a considerable reduction in the amount carried over in consequence of the particular path of the vapour, which results in entrained material being dropped when the vapour impinges against the top of the chamber.

It is therefore possible to reduce the thickness of the filters 3, thereby naturally reducing pressure losses, while continuing to obtain a distillate of remarkable purity.

The shape of the evaporator according to the subject invention offers various constructional advantages. Thus, for example, the special arrangement of the nests of tubes results in a reduction in the supporting system required and also enables their weight to be taken directly by the oor.

Moveover, it is possible to eliminate the suspended ducts for condensate collection used in various evaporators in the present state of the art, with further reduction and simplification of the interior load-bearing structures.

In this way, the cost of the plant is reduced.

Furthermore, elimination of the suspended ducts for condensate collection also makes it possible to eliminate loss of product, such as occurred in evaporators known hitherto by reason of overflowing into the saline solution below, especially during certain periods.

Finally, the particular ease of access to the heat exchanger tubes makes for ease of maintenance of the plant.

What we claim is:

1. A flash evaporator having a plurality of expansion chambers, said expansion chambers being connected in series, each of said chambers being provided with a central evaporation zone and two separate condensation 4 zones positioned laterally on each side of said central said heat exchangers symmetrically arranged in each evaporation zone, comprising: of said condensation zones.

a closed horizontal casing, said casing consisting of a 2. A flash evaporator as claimed in claim 1, further flat bottom, two vertical side walls and a top, said comprising a plurality of sills positioned vertically within top being generally flat in its central portion and said casing on the bottom thereof, each of said sills excurved at the edges joining said side walls; tending transversely of said casing in a separate chamber two vertical baffles positioned within and extending and positioned within each chamber midway between along the length of said casing in spaced-apart relasaid transverse batfies, the top of said sills being positionship with each other, said vertical bafiies defining tioned at a height greater than the height of the top of said central evaporation zone therebetween and said the opening formed in the bottom of said tnansverse two lateral condensation ones equal to and symbattles to maintain the liquid level at a height greater metrical with each other between said two vertical than he height Of the top of said opening.

baflles and said side walls of said casing, said bafiies having a discontinuity at the top thereof, said dis- References Cited continuilty haviliig an oplening theretgroiugh1 and ac- UNITED STATES PATENTS commo ating orizonta y positione rop et separating filters, said droplet separating filters positioned g ggfgg "2" horizontally above said central evaporation zone for 3186924 6/1965 Williamsi: a 202 173 permitting the flow of vapor from said evaporation 3216910 11/1965 Lan er et a1 202 173 zone to both of said condensation zones; 3431179 3/1969 Stulfner 202:173 a plurality of transverse bafiles positioned vertically 3488260 V1970 Gilbert within said casing in spaced-apart relationship With 3:197:387 7/1965 Lawranc; 202 197 each other, said transverse bafiles subdividing the 3,393,059 8/1968 Cane et a1 interior of said easing into a plurality of chambers, 3 413 214 12 19 Cane 202 197 each of said transverse fi s ha i g an p i 3,580,816 5/1971 Tidball et al. 1:: 202-173 therethrough adjacent the bottom of said casing for allowing liquid to flow from one chamber to an- WILBUR L. BASCOMB, J Pr mary EXaminer other; two heat exchangers comprising a plurality of tubes extending along the length of said casing, each of 202-197, 186; 20311, 40, 88

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