US3488260A - Flash evaporators - Google Patents

Description

Jan. 6, 1970 F. w. GlLBERT 3,48,260

FLASH EVAPORATORS Filed March 23, 1966 PEG. 2

INVENTOR.

F'RE DERIC K WALTER GILBERT A 0mm United States Patent U.S. Cl. 202-172 4 Claims ABSTRACT OF THE DISCLOSURE Evaporator construction comprising a plurality of serially arranged flash chambers discharging vapor into a common condenser.

This invention relates in general to distillation apparatus and, more particularly, to a particular configuration for a flash evaporator chamber, group of such chambers and their application in flash evaporation plants.

In the copending applications, U.S. Ser. Nos. 440,439; 440,846; 440,494 and 440,539, there is disclosed various multi-stage flash evaporator devices and methods of operations which have increased the efliciency, effect and capacity of flash evaporator plants. In U.S. Ser. No. 440,493, also copending, there is particularly disclosed a construction of a single flash evaporator chamber designed for use in the devices and with the methods disclosed in the other aforementioned applications. The concept of the invention stated in this latter application is the provision of an evaginated venturi entrant orifice for the efflcient flow and control of brine so as to prevent steam blowby and create stable, efiicient operation over a wide range of conditions.

It is the prime object of the present invention to make use of this concept in a new configuration which will greatly increase, above the previously known, the efliciency of individual flash stages or chambers.

It is another object of the present invention to provide a flash stage or chamber considerably smaller (by a multiple factor) than those previously known and which can be combined with others in a novel arrangement which would also reduce the overall size of a completeevaporator installation (again, by a multiple factor,) while simultaneously increasing its efiiciency and/or capacity.

In the aforementioned patent applications, there has been discussed techniques for combining into one plant operation multiple stages in numbers such as 64, 100 or even greater. With the individual stage units known in the prior art, or even disclosed in U.S. Ser. No. 449,493, all of which range in length from 30 feet, a 64 stage evaporator might be 600-1000 feet in length.

We have found that with the present invention, a 64 stage flash evaporator device would be no more than 300 feet in length.

Furthermore, in the prior art construction, the achievement of high lip loadings or flow rate per inch of lip (entrance) in a flash device was also hampered by the restrictions placed on size of the chambers and configuration of the chamber openings thus limiting the 3,488,260 Patented Jan. 6, 1970 ice actual capacity of the device. According to the present invention, lip load can be materially increased with plants of the same overall size or more efficiently used in smaller plants in order to obtain increased capacities.

In accordance with the present invention, each individual flash chamber is constructed of such size, that upon entry of the liquid through an evaginated venturi, the liquid would forcibly impinge on the opposing -wall of the chamber. The steam/ water mixture, comprising the liquid, will then be most efficiently separated. We have found that, dependent upon flow rates, pressure head, etc., the total length of each stage need be only within the range of 3-6 feet.

Furthermore, in accordance with the present invention, we arrange a plurality of chambers into a sequentially oriented section or effect so that the distillate vapor can be made to enter a common condenser unit. Further, we also stack multiple sections of such sequentially arranged stages in a vertical manner about a common condenser and thereby obtain greater capacity and efliciency in the same floor space and operating area. Combining these techniques with those shown in the aforementioned patent applications will greatly reduce the present size of flash evaporator plants and make a material reduction in costs.

These and other objects, advantages and distinctions over the prior art will become clearly apparent from the following description and from the appended drawings in which:

FIG. 1 is a side elevation view of a single flash chamber or stage showing the application of the present invention, and

FIG. 2 is a perspective view of a number of stages shown in FIG. 1 combined further in accordance with the present invention, and

FIG. 3 is a side elevation view of a stack of single stages as shown in FIG. 2.

With reference to FIG. 1, there is shown a flash chamber or single stage comprising a substantially rectangular shell 10 having a front wall 12, a rear or target wall 14, bottom wall 16, top wall 18, and side walls 20, of which only one is shown. The front and rear walls 12 and 14 are provided with openings 22 and 24, extending the entire width of the chamber and forming, respectively, liquid interstage entrant and exit orifices. An evaginated venturi entrance such as shown in U.S. Ser. No. 440,493 is formed by an inclined but generally upstanding plate 26 and a top plate 28 which is provided with a downwardly bent lip 30. Plate 26 extends upwardly from the floor 16 and top plate 28 and lip 30 extends completely across the width of the shell 10.

As brine passes through the evaginated venturi, it flashes into steam in the manner described in the aforementioned application Ser. No. 440,493. This steam exhausts or is withdrawin through an opening 32 formed in the side wall 20 after passing through a mesh filter 34 supported by angle frame 36 provided to separate small brine particles from the vapor.

Of critical importance in the present invention is the depth or distance between the front and fear walls 12 and 14. We have found that the limits defined in Ser. No.

440,493 are not nearly as critical as indicated there if the distance between walls 12 and 14 is kept to a reasonable minimum so that the incoming fluid is forced or impinged upon the rear wall 14. In order for this to occur, it is necessary that the rear wall 14 be brought closer to the front wall 12 than was ever contemplated in US. Ser. No. 440,493 which, if reference is made to FIG. 3 of that application and the attendant description, the liquid is impinged, if it impinges at all, only on the bottom wall 16. In practice, we have found that with, taking of variations in head, flow rate, position in the effect of the stage, etc., this distance lies between 3 to 6 feet and at an average of feet.

We have found that when the incoming liquid (jetisoned in by the venturi) hurls itself upon the rear wall, the force needed to bring the liquid to a zero velocity also acts to separate the vapor from the water molecules. This separation, in somewhat turbulent action, facilitates the flash of the liquid producing considerably more flash per unit of length of chamber.

At the present time, we are not fully aware of the limits of incoming velocity and the distance to be traveled to bring the flash to an optimum but we are convinced that the incoming fluid must be of such a velocity that its forward motion is violently stopped by the rear wall. Therefore, the velocity of the liquid and the distance of the rear wall are the relative factors to be considered.

In practice, we have also found that the individual chambers need be about 3-4 feet in length and 4-5 feet in width.

FIGS. 2 and 3 show a configuration or application which employs a multiplicity of the small but eflicient chambers shown in FIG. 1 in parallel feeding of a common long tube distillate condenser. The application shown here is a direct consequence of the high efficiency of the smaller unit and its modular construction.

A plurality of flash chambers 10 are arranged in sequential order to form a complete section 40. A section 40 would in practice contain a number of chambers equal to the desired stage capacity, i.e., for a 64 stage plant a section 40 would contain 64 chambers 10. These stages need not be physically consecutive and may be in separate effects; however, even if they were physically consecutive, it is obvious that with a maximum length of 6 feet per chamber, a 64 stage plant would only be 384 feet.

Taking only one section 40 of multiple chambers, it will be seen that the entrant and exit orifices 22 and 24 are in sequence and that the flow of liquid will be serially from front to rear. Furthermore, each of the vapor orifices 32 is facing in the same direction. These vapor orifices 32 exhaust distillate vapor on to or into a common distillate condenser 42. The distillate condenser can be economically fabricated from long tube stock 44, as shown, or by U tubes or other well known methods. The feeding of the condenser tube bundle can be made by the forward flow of the brine before entry into the high end of section 40.

Certain obvious advantages of even so elemental a structure as one section 40 and a distillate condenser of equal height are readily apparent. First, since there is more than one vapor entrance to the distillate condenser (heat exchanger) there occurs a minimum vapor loss in the tube bundle. Second, there is a common collection point for all vapor and condensate facilitating the collection and run of the distillate.

A further advantage will be apparent from FIGS. 2 and 3. In these figures, there is actually shown a vertically sectionalized construction of a multi-stage plant. Three sections 40 of multi-stages 10 are arranged on either side of a long tube bundle condenser 40, each stage similarly oriented and each section oriented so that the vapor orifices 32 all open into the condenser. The condenser 40, of course, is preferably of the same height as the combined vertical stack sections. While each of the stack sections flows brine independently of the other, they may be arranged physically and to flow brine in any one of the manners suggested in the aforementioned applications. The condenser collant may be circulated as noted above with split return to each of the six stacks or in any known manner.

In addition to the advantages noted above, this construction of vertically stacked sections has an advantage readily apparent. The combined flow of brine or capacity of the plant can actually be divided into the number of sections 40 provided. In the application noted, the intake would thus be divided by 6, one-sixth going through the 64 stages of each of the sections 40. Consequently, the lip loading is geometrically increased as is the time efiiciency. More capacity per size and energy input can be obtained. A second additional advantage is obvious; in

view of the modular construction, the single condenser and the proximity of all stages, lower heat and energy requirements are necessitated thus considerably lowering the plants initial and operational costs.

It is to be noted that in the construction shown in FIG. 2, the overall dimensions of a 64 stage evaporator (i.e., 64- stage in 6 sections) would be approximately 12 feet x 15 feet x 300 feet.

The use of an interstage flash device 46 on the distillate side of the condenser system may be had if desired. Such a device would tend to minimize tube corrosion. Such a device would also be in a multi-million gallon per day plant where a river has to be transferred between stages at low pressure differences.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efliciently attained. Certain changes may 'be made in carrying out the above method and in the composition set forth without departing from the scope of the invention and it is intended that all matter contained in the above description be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An evaporator section comprising a distillate condenser, a plurality of evaporator sections each having an inlet and an outlet for the flow of liquid therethrough and a vapor discharge means, an evaginated venturi having a continuous elongated orifice along the extent through which the liquid is jetisoned, said jet means located at said inlet for forcibly injecting liquid into said section and to impinge said liquid against a wall in which said outlet is located, said sections being arranged ad seriatim for the continuous flow of liquid therethrough, each of said sections being further arranged so that their vapor discharge means are similarly faced, said discharge vapor means discharging the vapor directly into said distillate condenser.

2. The evaporator according to claim 1 in which said condenser comprises long tube distillate means and said sections being vertically disposed one upon another in two stacks, said stacks being arranged on opposite sides of said condenser so that the vapor discharge means face said condenser, and discharge distillate at various levels directly into said condenser.

3. The evaporator according to claim 2 including liquid supply means for feeding liquid to be evaporated, and means for dividing the flow of liquid into equal parts dependent upon the number of sections forming said evaporator and means for feeding the respective parts to said sections.

4. The evaporator according to claim 2 in which each of said evaporator sections comprises a substantially rectangular box having side walls, top and bottom walls and front and rear walls, said front wall having jet means for forcibly injecting liquid into said chamber, said rear wall having an exit opening for unevaporated liquid be ing spaced therefrom in position to have said liquid impinge thereon, to decrease the forward velocity of said' fluid to zero, and one of said side walls having the vapor discharge means.

(References on following page) References Cited UNITED STATES PATENTS Woodward .1- 202173 Wilson et a1. 202173 XR Hammond 202173 Worthen et a1. 20388 Worthen et a1 202173 Worthen et a1. 202173 Lawrance 202173 Kingma 202-173 3,228,859 1/1966 Frankel et a1. 202-173 3,259,552 7/1966 Goeldner 202-173 FOREIGN PATENTS 831,478 3/ 1960 Great Britain.

WILBUR L. BASCOMB, JR., Primary Examiner DAVID EDWARDS, Assistant Examiner US. Cl. X.R. 202173, 186; 20311, 88, 73

Images