Evaporation element and process using same

Abstract

A process for production of minerals using an evaporation unit comprising an evaporation element for exposing thereof to the atmosphere for evaporation of a liquid solution therefrom. The evaporation element comprises an evaporation surface and a texture for deflecting the solution during movement along the surface, leaving minerals on the surface as a result of evaporation of the solution. The texture allows the minerals to detach from the element under the sole influence of normal forces of nature before the minerals reach a weight capable of damaging the evaporation unit. The process includes wetting the element with the solution, which at least partially evaporates and forms precipitated minerals, at least some of which are left on the surface; and letting the minerals detach from the surface solely under the influence of normal forces of nature before the minerals on the surface reach a weight capable of damaging the unit.

Claims

1. A process for production of minerals, the process comprising: providing an evaporation element for exposing thereof to an atmosphere for evaporation of a liquid solution therefrom, the evaporation element including an evaporation surface oriented for allowing movement of the liquid solution therealong under influence of gravity and having a texture configured for deflecting the liquid solution during the movement along the evaporation surface, leaving minerals on the evaporation surface produced as a result of evaporation of the liquid solution, and further configured for allowing the minerals to detach from the evaporation element under the sole influence of gravity and/or winds of up to 60 km/h, before the minerals on the evaporation element reach a weight capable of damaging the evaporation element; mounting the evaporation element so that the evaporation surface forms an angle between 0 to 30 degrees with an imaginary vertical axis; wetting the evaporation element with the liquid solution, which at least partially evaporates and forms precipitated minerals, at least some of which are left on the evaporation surface; and letting the minerals detach from the evaporation surface solely under the sole influence of gravity and/or winds of up to 60 km/h, before the minerals on the evaporation surface reach a weight capable of damaging the evaporation element.

2. The process of claim 1, further comprising collecting at least some of the precipitated minerals.

3. The process of claim 2, wherein the precipitated minerals collected have detached from the evaporation surface.

4. The process of claim 2, wherein the precipitated minerals collected were not left on the evaporation surface.

5. The process of claim 2, wherein collecting at least some of the precipitated minerals includes collecting all precipitated minerals.

6. The process of claim 1, further comprising collecting the liquid solution that has not evaporated.

7. The process of claim 6, further including collecting any precipitated minerals that are in the liquid solution that has not evaporated.

8. The process of claim 1, wherein the texture of the evaporation surface is rough or irregular or comprises a pattern or comprises projections extending in a direction away from the surface or is formed with grooves or is formed with facets.

9. The process of claim 1, wherein the evaporation surface is wettable by liquid.

10. The process of claim 1, wherein the evaporation surface is wettable by liquid by adsorbing hydrophilic polymers onto the evaporation surface or by chemically grafting hydrophilic groups on the evaporation surface.

11. The process of claim 1, wherein the evaporation surface is hydrophilic.

12. The process of claim 1, wherein the texture of the evaporation surface is free of an anchoring configuration.

13. The process of claim 1, wherein the texture of the evaporation surface has a majority thereof free of pores, or is formed only with pores that are spaced at least 10 cm apart from each other, or is free of undercuts.

14. The process of claim 1, wherein the texture of the evaporation surface is free of through holes.

15. The process of claim 1, wherein the evaporation surface of the evaporation element and/or the evaporation element is made of at least one material selected from the group consisting of polyolefins, high density polyethylene, polypropylene, halogenated aliphatics, PVDF, PVC, polyacetate, ABS, PPO, fiberglass, Polyether ether ketone (PEEK), and nylon.

16. The process of claim 1, wherein the evaporation element is substantially rigid.

17. The process of claim 1, wherein the evaporation element is a building block of an evaporation unit configured to bear the load of other evaporation elements.

18. The process of claim 1, wherein the evaporation element is free of depressions extending from the evaporation surface into interior of the evaporation element, which have within the interior a larger linear dimension parallel to the evaporation surface than their corresponding dimension at the evaporation surface.

19. The process of claim 1, further including providing a liquid solution reservoir with a slit at a bottom thereof, configured to receive therein an upper portion of the evaporation element, the evaporation element having two substantially parallel surfaces and the slit having substantially parallel walls formed with periodically spaced vertical ribs, the ribs being configured to be in such close proximity to the evaporation surfaces of the evaporation element as to keep constant a distance between the evaporation element and the walls of the slit at those areas of the walls that are free of said ribs, defining thereby a flow channel on each side of evaporation element.

20. An evaporation unit, comprising: an evaporation element for exposing thereof to an atmosphere for evaporation of a liquid solution therefrom, the evaporation element including: an evaporation surface oriented for allowing movement of the liquid solution therealong under the influence of gravity, the evaporation surface having a texture which is free of an anchoring configuration and which is configured for deflecting the liquid solution during the movement along the evaporation surface, leaving minerals on the evaporation surface produced as a result of evaporation of the liquid solution, the texture of the evaporation surface further configured for allowing the minerals to detach from the evaporation element under the sole influence of gravity and/or winds of up to 60 km/h, before the minerals on the evaporation element reach a weight capable of damaging the evaporation unit; and a mounting arrangement for mounting the evaporation element so that the evaporation surface forms an angle between 0 to 30 degrees with an imaginary vertical axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to understand the subject matter of the present application and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic front view of a portion of an evaporation unit;

(3) FIG. 2 is a schematic side view of the portion of the evaporation unit in FIG. 1;

(4) FIG. 3 is a schematic front view of a portion of another evaporation element;

(5) FIG. 4 is a schematic front view of a portion of yet another evaporation element;

(6) FIG. 5 is a schematic side view of still another evaporation element;

(7) FIG. 6 is a schematic side view a further evaporation element;

(8) FIG. 7A is a schematic front view a further evaporation element;

(9) FIG. 7B is a schematic front view of yet a further evaporation element;

(10) FIG. 8 is a schematic side view of a portion of another evaporation unit;

(11) FIG. 9 is a schematic side view of a portion of an evaporation element with a solid deposit anchored thereto;

(12) FIG. 10A illustrate a different evaporation unit;

(13) FIGS. 10B and 10C are cross-sectional views of the evaporation unit of FIG. 10A taken along the respective planes B-B and C-C in FIG. 10A; and

(14) FIG. 11 illustrate the manner in which the evaporation element of the evaporation unit of FIG. 10 can be held.

DETAILED DESCRIPTION

(15) In a comparative experiment, two evaporation elements were prepared, one a porous netting and the other a fiberglass board.

(16) The fiberglass board was prepared using a redox pair of potassium persulfate/potassium metabisulfite to generate radicals, using Hydroxyethylmethacrylate (HEMA) as a hydrophilic monomer to be grafted onto a surface of the fiberglass board by in-situ grafting.

(17) After one hour of exposure to the reaction mixture, the surface of the fiberglass board was shown to be hydrophilic by inspection as water spread thereon instead of beading up as normally occurs with a similar board which has not undergone the treatment above.

(18) The evaporation elements were mounted in a lab-scale outdoor evaporation unit. The evaporation unit was fed with a mineral brine containing 25-28% total dissolved solids (TDS) including mixed chlorides, and operated for over one month.

(19) At the end of the time of operation, it was seen that solids deposited on the fiberglass board detached and fell away from the surface thereof solely due to gravitational forces. The solids deposited on the porous netting did not detach from the surface thereof.

(20) Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout several views, there is shown in FIGS. 1 and 2, a portion of an evaporation unit, generally designated by the numeral 10, for increasing evaporation from a surface of a body of liquid (not shown). To aid understanding, an imaginary horizontal plane X and an imaginary vertical axis Y, are shown. The liquid source in the present example is a brine reservoir, and thus the evaporation unit 10 is used for brine volume reduction of highly saturated mineral brines.

(21) The evaporation unit 10 is mounted above a horizontal surface 12 of a bank adjacent the body of liquid.

(22) It will be understood that the evaporation unit can also be mounted directly above a body of liquid (not shown).

(23) The evaporation unit 10 comprises, and suspends above the surface 12, an evaporation element, generally designated as 14, and a fluid distribution system including pipes (16A, 16B) for wetting the evaporation element 14 with fluid 18 from the body of liquid. In the present example the evaporation unit 10 holds the evaporation element 14 in an orientation slightly slanted with respect to a vertical axis, as indicated by an acute angle .

(24) The angle can be between 0 to 30 degrees from the imaginary vertical axis Y, and in this case is 30 degrees.

(25) The evaporation element 14 is formed with a sheet-like shape having two opposite evaporation surfaces (20A, 20B).

(26) The evaporation element 14 comprises three layers, a first outer layer 22A, a second outer layer 22B and a central layer 22C extending between the first and second outer layers (22A, 22B). A thickness of the evaporation element 14, including the three layers (22A, 22b, 22C) is designated as T.

(27) The first outer layer 22A constitutes one of the evaporation surfaces 20A, and the second outer layer 22B constitutes the other evaporation surfaces 20B.

(28) In the present example the central layer 22C is made of fiberglass.

(29) It will be appreciated that the evaporation element, or the central layer thereof, can be made of high density polyethylene sheet with or without reinforcement, PVC, or any other polymer with sufficient mechanical strength to maintain the form of a sheet.

(30) The outer layers (22A, 22B) constituting the evaporation surfaces (20A, 20B) are each hydrophilic coatings on the central layer 22C.

(31) The evaporation surfaces (20A, 20B) are formed with horizontal elements (24) projecting horizontally outwardly therefrom and arranged in a regular pattern.

(32) The pipes (16A, 16B) are formed with apertures (26A, 26B) configured to project liquid 18 on the evaporation surfaces (20A, 20B) drawn using pumps (not shown) from the body of liquid (not shown).

(33) During operation, the liquid 18 seeps out of the apertures (26A,26B) of the pipes (16A, 16B) and falls by gravity on the evaporation surfaces (20A, 20B).

(34) As can be seen in FIG. 1, the texture of the evaporation surface 20A, which includes the horizontal elements 24, causes the liquid 16 to diverge from a single liquid path 28A into a plurality of liquid paths 28B, forcing the liquid to move sideways as well as downwards. The plurality of liquid paths 28B, each being non-linear due to repeated sideways deflection of the liquid moving along the evaporation surface caused by the presence of the horizontal elements 24.

(35) The liquid on the evaporation surfaces (20A, 20B) is also exposed to wind (not shown) causing evaporation thereof.

(36) Minerals 29 produced by evaporation of the liquid 18, fall to the horizontal surface 12 of the bank, as a result of gravitational and wind forces thereon.

(37) Referring now to FIG. 3, it will be appreciated that divergence of a liquid path into multiple paths (not shown) can also be caused by use of an evaporation element, generally designated as 30, comprising a random pattern of elements 32 projecting from an evaporation surface 34 thereof.

(38) Other examples of evaporation elements having a suitable texture are shown in FIGS. 4 to 6. FIGS. 4 and 5 illustrating evaporation elements (36A, 38A) which have evaporation surfaces (36B, 38B) formed with differently oriented facets (36C, 38C), and FIG. 6, illustrates an evaporation element 40A formed with a corrugated shape.

(39) Evaporation elements such as those described above and below may be used with evaporation units such as those described in U.S. Pat. No. 7,166,188, the detailed description of which, as far as the use of the evaporation units is concerned, is incorporated herein by reference.

(40) Referring FIGS. 7A and 7B, there is shown further examples of evaporation elements (42, 44). Evaporation element 42 differs from evaporation element 44, in that it comprises projections following a horizontal pattern. That is to say that it is formed with a plurality of horizontal ribs 46. By contrast, evaporation element 44 is formed with vertical ribs 48.

(41) It is believed that the evaporation element 42 can have greater efficiency as it further obstructs or at least lengthens the downward flow path of liquid solution thereon.

(42) FIG. 8 shows a portion of an evaporation unit, similar to the evaporation unit shown in FIGS. 1 and 2. Notable differences are that the evaporation element 14 is parallel with the imaginary vertical axis Y, a distribution pipe 16B is disposed directly above the evaporation element 14, and one of the distribution pipes is connected by a netting or fabric (16C) that guides movement of liquid solution from the apertures (26A, 26B) down to the evaporation element 14.

(43) It will be understood that each of the notable differences mentioned above are only shown in a single figure for the purposes of convenience, and that an evaporation unit may have a distribution pipe at any convenient location, such netting or fabric is optional and that the orientation of an evaporation element can be chosen per the design criteria for a given application.

(44) For the purpose of understanding anchorage of minerals to evaporation elements, drawing attention to FIG. 9, there is shown an example of a portion of an evaporation element 70, formed with a pore 74 (through hole) extending from a first evaporation surface 76 to an opposite evaporation surface 78 thereof. Also shown is a mineral solid deposit 80 which has accumulated on the evaporation element 70 and is anchored thereto the via the pore 74. The solid deposit 80 comprises a first portion 82 adjacent the first evaporation surface 76, a second portion 84 adjacent the other evaporation surface 78, and a bridging portion 86 extending through the pore 74 and connecting the first and second portions (82, 84).

(45) As in the present example, the evaporation element 70 is flexible, wind forces applied to thereto cause the evaporation element 70 to bend, which can break the typically brittle solid deposit 80, at the bridging portion 86 thereof, causing the first and second portions (82,84) to fall from the evaporation element 70.

(46) However, if there were additional pores (not shown) disposed in close proximity to pore 74 (e.g. less than 10 cm distance between them), additional bridging portions connecting the first and second portions (82,84) could be present, reinforcing the connection therebetween such that even when the evaporation element 70 is bent by normal wind forces the bridging portions would be able to maintain connection between the first and second portions (82,84), preventing their detachment from the evaporation element 70.

(47) Similarly, the detachment of a mineral solid deposit from the pore 74 would be prevented if the pore would have within the interior of the evaporation element a larger linear dimension parallel to the evaporation surface than its dimension at the evaporation surface.

(48) FIGS. 10A to 10C illustrate an example of an evaporation unit comprising an evaporation element and a feed trough rather than a pipe as shown in FIGS. 1 and 2, for containing a mineral solution to be used for wetting the evaporation element.

(49) In particular, FIGS. 10A to 11 show such evaporation unit including an evaporation element 100 in the form of a thin sheet made of any material as described above or any other suitable material, and a feed trough 104 containing a mineral solution and formed with a slit 101, which is in fluid communication with the interior of the feed trough 104. The slit 101 is configured for receiving therein an upper portion of the evaporation element 100 so as to provide a steady flow of the mineral solution over each evaporation surface of the evaporation element 100 disposed below the slit 101, by the force of gravity that generates a pressure head due to the height of the mineral solution above the slit 101.

(50) As illustrated in FIG. 10C, a flow channel obtained on each side of the evaporation element 100 within the slit 101, has a thickness, which is defined by a distance designated as 2B, between the corresponding side of the evaporation element 100 and the inner surface 103 of the slit 101. This distance is maintained by a series of vertical ribs 102 protruding a distance 2B from the inner surface 103 of the slit 101, as illustrated in FIG. 10B.

(51) In the above arrangement, a mass flow rate, {dot over (m)}, down through the flow channel obtained on each side of the evaporation element 100 is governed by the equation for laminar flow in a slit given by:

(52) $\stackrel{.}{m}=\frac{2P\left(W-{\mathrm{nw}}_r\right)B^3}{3L}$

(53) where: P is given by g(L+a), where L is the length of the flow channel, a is the height of mineral solution above the flow channel, is the density of the mineral solution and g is the gravity force, B is the half thickness of the flow channel on each side of the evaporation element, W is the width of the flow channel, n is the number of vertical ribs 102 of the slit wall 103, w.sub.r is the width of each vertical rib in the slit wall, and is the viscosity of the mineral solution.

(54) FIG. 11 illustrates one example of a manner, in which the evaporation element 100 can be fixed with respect to the feed trough 104 by means of a support structure including two vertical structural elements 107 configured for attaching thereto the evaporation element 100 along its side edges, and two horizontal structural elements 108 configured for attaching thereto the evaporation element along its top and bottom edges. Only one of the horizontal structural elements 108 is shown in FIG. 11, i.e. the one to which the bottom of the evaporation element is attached, whilst the other horizontal element (not shown) can be disposed within or above the trough 104.

(55) In this example, the evaporation element 100 is formed along its side, top and bottom edges with reinforced eyelets 105, and the structural elements are formed with corresponding perforations. The eyelets 105 can be formed directly in the body of the evaporation element 100 or can be provided by attaching to this body, along each edge thereof, a strip of material other than that of the evaporation element, in which the eyelets 105 are formed.

(56) With the above arrangement, the evaporation element 100 is fixed to the structural elements 107 and 108 by connecting its eyelets 105 and the corresponding perforations in the structural elements 107 and 108 using loops 106 made of a non-extendible material that is strong enough to withstand the operational conditions of the evaporation element. For example, this material can be in the form of cords, wires or ropes. Alternatively for top and bottom edges of evaporation element 100 can each have a sleeve of strong fabric extending therealong and configured to receive therein the horizontal structural elements 108.

(57) In the above described example, when the evaporation element 100 is fixed to the support structure 107, 108, its upper portion can protrude upwardly from the slit 101 into the trough 104 if one of the horizontal structural elements 108 is disposed within or above the trough, or it can pass through the trough and protrude upwardly therefrom, if the corresponding horizontal element 108 is mounted above the trough and is spaced therefrom. Alternatively, the loops 106 connecting the upper portion of the evaporation element 100 with the corresponding horizontal structural element 108 (not shown) can protrude from the upper portion of the evaporation element into the trough 104 if one of the horizontal structural elements 108 is disposed within or above the trough, or can protrude upwardly from the trough 104, if the corresponding horizontal element 108 is mounted above the trough.