ES2340452A1 - Device and procedure for desalination of branches provided by solvent water detachers with a solvent solvent with water. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Device and process for desalting brines from saline desalination plants with a solvent miscible with water, which comprises adding to a brine feed the amount of at least one solvent c 1 -c 5 miscible with the water necessary to form a brine-solvent mixture in the range of 9: 1 to 1: 4; separating the precipitated salts obtaining a stream of brine with a reduced salt content; distilling said stream, recovering the solvent that can be returned to the solvent tank or burned to produce heat and/or electricity and obtaining a second stream of brine with a reduced salt content, which is subjected to reverse osmosis and then to a new one distillation stage, obtaining a deposit of precipitated salts and a stream of pure water. (Machine-translation by Google Translate, not legally binding)

Description

Desalination device and procedure of brines from brackish water desalination plants with a solvent miscible with water.

Field of the Invention

The present invention relates to a device and a procedure for brine desalination, preferably from brackish water desalination plants using at least one solvent miscible with water, preferably ethanol, methanol, acetone or acetonitrile and more preferably bioethanol from the fermentation of matter organic, with the aim of eliminating brine emissions from these types of plants and therefore reduce their environmental impact to zero. The use of bioethanol waste as an energy source to produce the demands of the process and the fact that it comes from a renewable source, eliminate the other negative impact that they have these plants and help meet the objectives on the replacement of fossil fuels with those from renewable sources, finding new uses for this type of fuels

Background of the invention

The problem of fresh water shortages in populations is an increasingly pressing problem, especially in some countries like Spain, where rainfall is Few The increasingly incontestable evidence of a change Global climate stresses this problem, and therefore converts the provision of solutions for obtaining fresh water in a first order priority.

One of the existing solutions for the provision of fresh water are desalination plants that obtain fresh water from springs or brackish water aquifers. This process produces a residue that has to be disposed of and called brine, which are currently being returned to the sea or the reservoir from which it comes, generating a significant environmental impact. However, brackish water desalination plants have two serious problems:

a) They have to purify waters that are very rich in salts (sulfates, carbonates, bicarbonates, nitrates ...) of cations divalent (Ca, Mg, Ba ...). These salts precipitate easily during the osmosis process if you try to concentrate too much, so the performance of this process is lower than it would be expected to prevent the membranes from deteriorating. The process of concentration should be stopped with 30 g / l of total solids when in seawater easily reaches 60 and forces substances to be added that avoid precipitation;

b) Being located inside, the Brine evacuation is complicated, since it involves construction of expensive brine products or to be reintegrated into aquifer, which leads to its depletion. This factor is sometimes the limiting factor to make desalination plants.

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A mass balance for a water desalination plant Typical brackish might be as follows:

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Entrance: 23,000 m 3 / day of water brackish containing 368 tons. of salts;

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Departure: 14,960 m3 / day of fresh water which contains 7 tons. of salt, plus 8,040 m 3 / day of brine than contains 361 tons. of salts

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At present, these 8,040 m3 / day of the brine resulting from the process is poured into the sea, through a expensive driving, which results in a negative environmental impact, since despite having less salinity than seawater, it has a salt composition very different from that of the sea.

The existence of an installation would be desirable and a process that solved the problem of what to do with brines from desalination of brackish waters, obtaining from them products with commercial value and avoid environmental impact it currently has.

On the other hand, there are factories to obtain of ethanol from the fermentation of organic matter rich in carbohydrates (which is known, due to its origin, as "bioethanol"). While these procedures result in a renewable fuel, and therefore desirable from the point of view environmental, however in its production there is a consumption of energy that can sometimes be higher than what you get from your use and that is the undesirable side of the process, not having developed up to now efficient systems to their use, which can compromise the development of these systems. Therefore, to optimize the environmental profitability of using this biofuel, it is essential to make the most of your energy capacity

The present invention comes to provide a solution to both problems simultaneously by providing a brackish water brine desalination plant that it transforms these into fresh water, completely avoiding spills. This process is done by treating the brine from desalination with at least one solvent C_ {1} -C_ {5} miscible with water, preferably ethanol, methanol, acetone, or acetonitrile, and more preferably bioethanol, or mixtures thereof in any proportion. The solvent residue consumed in this process is used to produce the thermal and electrical energy consumed in it, taking advantage of almost 100% of the energy that It has the molecule. In addition, the procedure allows recovering the water produced during the combustion of the solvent, increasing System efficiency

Ethanol (CH 3 -CH 2 OH) It is a molecule that after complete combustion (+3 molecules of O2) produces 3 molecules of H2O and 2 of CO2. In the This invention is intended to take advantage of everything: energy and water; he CO2 that is poured into the atmosphere, coming from a source Renewable, it is less harmful. Throughout the process the thermal energy that is generated in the different processes by heat exchangers, mainly in the phases of generation and distillation. Thus, ethanol serves to precipitate the salts, produce thermal and electrical energy and produce water.

Consequently, a first aspect of the invention relates to a process for water desalination Brackish according to claim 1.

A second aspect of the invention relates to a device or installation for desalination of brines from brackish water as defined in claim 12.

Through this installation and procedure We get the following advantages:

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eliminate any type of spillage from brackish water desalination plants and thus reduce enormously the environmental impact of desalination;

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increase the yield of obtaining fresh water, up to 120% of treated brine, when used even the water produced during the combustion of bioethanol;

-

value the desalination residue, obtaining salts with a commercial value,

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reduce CO2 emissions to global level, and

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harness all the energy of the bioethanol molecule in the form of electrical energy (of the order of 35%) and heat energy (of the order of 65%), making profitable Energetically the process.

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Figures

Figure 1 shows the general scheme of operation of the procedure and installation for desalination of brackish waters of the invention. Note that the process of invention begins with the brine, not with the desalination plant.

Detailed description of the invention

In general, the solvents usable in the apparatus and method of the invention (referred to herein as memory "the solvent" in a generic way) will be all those solvents that have a number of atoms in their molecule carbon less than or equal to 5 (that is, C_ {1} -C_ {5}) and that they are miscible with water, or mixtures thereof. These solvents are preferably select from the group consisting of ethanol, methanol, acetone or acetonitrile or mixtures thereof in any proportion, more preferably it is ethanol, and most preferable is ethanol obtained from the fermentation of organic matter or "bioethanol."

A preferred embodiment of the installation for desalination of brines from a desalination plant of brackish water according to the invention comprises the following stages:

to)

Brine Feed Inlet coming from desalination plants. In the present example, this brine It has an approximate salt content of 30 g / l.

b)

Solvent tank

C)

Mixer solvent-brine with tank decanting

d)

Mixing supply pipe solvent-brine

and)

Salt Filtration precipitates

F)

Supply pipe solvent-brine (partially desalted in the stage f)

g)

Solvent distillation

h)

Solvent supply pipe distilled

i)

Osmosis

j)

Water with salts from the osmosis process

k)

Water pure from the osmosis process

l)

Water supply pipe pure

m)

Pure water tank.

n)

Power generation from solvent

or)

Condensation of the water produced in the solvent combustion

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And the procedure for water desalination Brackish of the invention is therefore as follows (Figure 1):

First, the brine from the desalination plant is received in (1). This brine has a content approximate in salts, in the present embodiment, of 30 g / l. To brine is added, from the tank (2), the appropriate amount of solvent to form a mixture of 9: 1 to 1: 4 of Brine: solvent. This mixture passes through the mixer (3) plus a decanter tank and then through the pipe (4) until reaching the decanter tank and filtration system (5), where retain salts that have precipitated as a result of the addition from solvent to brine. These salts are fundamentally sulfates, carbonates, bicarbonates and nitrates, mostly of divalent cations and their precipitation can be done in a way fractional if desired; for this it is played with the proportions of brine: solvent that can range from 9: 1 to 1: 4 according to the objectives and dissolved salts. This filtration stage can be done by different filter media, such as a drum filter, of disks or a hydrocyclone, among others. Then the mixture of brine and solvent (partially desalted) continue through the pipe (6) to the distillation stage (7a). Distillation in This stage is performed under vacuum, at a pressure of 175 mbar and 50 ° C. In This stage is distilled off the solvent, which follows by the pipe (8), and the water with the remaining salts, which follows the pipe (9). The contribution of heat energy to this stage of distillation (7 a) can be done by the heat generated in the plant of combustion of the solvent (15), as will be seen later. For the therefore, as a result of the distillation stage (7a) a solvent that passes through the pipe (8) and can either go to feed the solvent tank (2), whereby the solvent is recovered back to start the desalination process again, or else feed the solvent combustion plant (15), or else split between both processes in any proportion, according to agree. On the other hand, the distillation stage (7a) is obtained also a quantity of water that still has some salts dissolved not precipitated in the previous step; in the example, 15 g / l, mainly of chlorides and salts of monovalent cations. This water is conducted through the pipe (9) to the reverse osmosis stage (10) from which it is obtained:

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a substantially pure amount of water, which approximately up to 75% of the amount of water entering the stage of reverse osmosis (10), and that is conducted through the pipe (12) up to a reservoir of pure water (14); Y

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a amount of water enriched in salts, which approximately supposes up to 25% of the amount of water entering the osmosis stage inverse, which contains approximately 60 g / l (10), and which is conducted through the pipe (11) to a new distillation stage (7b).

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The realization of this new distillation process (7b) of the salt water gives rise to a second stage of collecting salts, mainly chlorides, and a new water supply distilled, which is supplied to the tank of pure water (14) by means of pipe (13). In the same way as in the distillation stage (7a), in distillation stage (7b) heat for distillation can obtained from the combustion of the solvent that is carried out in the stage (fifteen).

An optional feature of the present invention is that the steps (7a) and (10) are interchangeable, of so that the distillation stage (7a) can be carried out at continuation of the reverse osmosis stage (10), always in function of the chemical characteristics of water and the type of membrane of Osmosis used in each case.

Finally, in step (15) the combustion of the solvent from the pipe (8), and that it comes in greater or lesser proportion from the distillation stage occurred in (7a). In this combustion stage the solvent, obtaining water by-products as combustion pure (which also preferably targets the deposit of accumulation of pure water (14)), electricity (which can be routed to other channels for sale), and heat (which can be used in distillation steps (7a) and (7b)). This combustion stage of solvent can be performed by any means known in the technique to carry out this type of combustion, such as a combustion boiler

The distribution of the solvent produced in the distillation stage (7a), and coming out of the pipe (8), can be carried out in any proportion, according to the interests and convenience of the process. For example, if what you want is conserve as much of the solvent as possible for recirculation to the desalination process, the solvent outlet of step (7a) will be directed mostly to the deposit (2). Yes, for on the contrary, it is not necessary to conserve the solvent since there is a sufficient external solvent supply (e.g. from of a bioethanol production plant), part or all solvent from the distillation stage (7a) to the combustion plant (15), obtaining heat, electricity and an additional amount of pure water from the own solvent combustion. This way you can maximize, in case necessary, the production of pure water, so that for a brine amount of 12,000 m 3 / day can be obtained a amount of pure water of up to about 24,000 m3 / day.

In the procedure and device of the invention, the brine can come from feeds coming of industrial plants, with high cation salt content divalent, likely to be purified by this process, or of solutions with high content in salts of divalent cations, likely to be precipitated and exploited by this process. However, they preferably come from desalination plants of any type and most preferably brackish water desalination plants.

In summary, thanks to the invention, from supply of brackish water from desalination plant, and without more product addition than a solvent input such as ethanol, the quantity of which can be chosen at will according to convenience, the aforementioned advantages of the invention are obtained, to know: eliminate any type of discharge from desalination plants, thus greatly reducing the environmental impact of the desalination; increase the yield of obtaining fresh water; Y valorize the desalination residue, obtaining salts with a value commercial. On the other hand, as the proportion of solvent is chosen which is distributed between recirculation to the process or combustion, we obtain, respectively:

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a self-feeding of the solvent to the circuit, of so that there is no net consumption of this product, or,

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yes there is a convenient external solvent supply such as the from a bioethanol production plant, a production additional of:

\ circ

\ vtcortauna electric power, which can be commercialized;

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\ vtcortauna heat energy, which can be used in the distillation stages of the process, thus reducing the consumption of electrical energy in the plant; Y

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\ vtcortauna pure water, adding to that already produced in the other stages of the process.

Claims (16)

1. Procedure for desalting brines that It comprises the stages of:

to)

add to a feed (1) of brine the amount of at least one solvent C_ {1} -C_ {5} miscible with the water needed to form a brine: solvent mixture in the range of 9: 1 to 1: 4;

b)

do Pass the brine mixture: solvent through a mixer / decanter (3);

C)

filter the mixture of brine: solvent from the mixer / decanter (3) for about filtration means (5), whereby the salts that have been collected are collected precipitate as a result of the solvent addition, obtaining a liquid stream (6) containing a mixture of solvent and water with the salts that remain in dissolution;

d)

distill the solvent and water mixture with the salts that remain in solution (6) resulting from the stage (c) in a distillation stage (7a), obtaining a solvent stream (8) and a stream of water with salts that remain in solution (9);

and)

submit the water stream with the salts that remain in solution (9) from step (d) a a reverse osmosis stage (10), obtaining a current of substantially pure water (12) that is conducted to a reservoir of substantially pure water (14) and a stream of enriched water in salts (11) which is conducted to a second distillation stage (7b);

F)

submit the water stream enriched in salts (11) from stage (e) to a second distillation stage (7b), by which salts are collected precipitates as a result of distillation, obtaining a second stream of distilled water (13) that leads to a pure water tank (14).

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2. The method according to claim 1, wherein the distilled solvent (8) from the stage of distillation (7a) is directed to either recharge the tank of solvent (2), whereby the solvent is recovered back to start the desalination process again, or else feed a solvent combustion stage (15), or is divided between Both processes in any proportion. 3. The method of claim 1 or 2, wherein the distilled solvent (8) from the stage of distillation (7a) is burned in step (15), obtaining as combustion products substantially pure water that is conducted to the tank of pure water (14), electricity and heat. 4. The method according to claim 2, in which the heat generated in the combustion of the solvent is transmits at least one of the distillation stages (7a) or (7b) for use in them. 5. The procedure of any one of the claims 2-4, wherein the water substantially pure obtained from the distillation stage (7b), of the reverse osmosis stage (12) or the combustion stage of solvent (15) is led to the water accumulation tank pure (14). 6. The procedure of any one of the previous claims, wherein the filtration by means Filtration (5) is performed through a drum filter, of discs or a hydrocyclone. 7. The procedure of any one of the previous claims which includes the additional step of selectively precipitate the retained salts in the media filtration (5). 8. The procedure of any one of the previous claims wherein the distillation steps (7a) and reverse osmosis (10) are interchanged. 9. The procedure of any one of the previous claims, wherein the at least one solvent C_ {1} -C_ {5} miscible with water is selected from the group consisting of ethanol, methanol, acetone, acetonitrile and mixtures thereof in any proportion. 10. The procedure of any of the claims 1-9 above, wherein the Solvent is bioethanol. 11. Device for the implementation of the method of any one of the claims 1-10 above, comprising:

to)

a input (1) for brine-based feed from brackish water desalination plants;

b)

a tank (2) for the solvent;

C)

a mixer / decanter (3) to mix the solvent with the brine feed plus a tank for the decantation of precipitated salts;

d)

some filtration means (5) to filter and separate the salts precipitates as a result of the addition of solvent to the brine;

and)

some first distillation means (7a) to distill the mixture of solvent and water with the salts that remain in solution (6) obtaining a solvent stream (8) and a stream of water with salts that remain in solution (9);

F)

some reverse osmosis means (10) to perform reverse osmosis of the water with the salts that remain in solution (9) from distillation means (7a), resulting in a stream of water substantially pure (12) and a stream of water enriched in salts (11);

g)

some second distillation means (7b) to distill the current of salt-enriched water (11) from osmosis media inverse (10), obtaining a stream of distilled water (13) and separating a second amount of precipitated salts at consequence of distillation; Y

h)

a substantially pure water tank (14).

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12. Device according to claim 11 above, which also includes combustion means of solvent (15) to burn at least part of the solvent from of the first distillation media (7a). 13. Device according to any one of the claims 11 or 12, comprising means for distributing the solvent stream (8) obtained in the first means of distillation (7a) or to solvent combustion means (15), either back to the solvent tank (2), or between Both in any proportion. 14. Device according to any one of the claims 11-13 above, wherein filtration means (5) are a drum, disc filter or a hydrocyclone 15. Device according to any one of the claims 11-14 above, wherein solvent combustion means (15) is a boiler or turbine of solvent combustion. 16. Device according to any one of the claims 11-15 above, wherein Stages (7a) and (10) are interchangeable.