ES2350141A1 - Procedure for the elimination of boro of water and equipment to carry out such procedure (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Procedure for removing boron from water and equipment to carry out said procedure. The present invention relates to a process for removing boron from water comprising performing a first step of reverse osmosis by feeding brackish water into a container of reverse osmosis membranes comprising a plurality of membranes interconnected in series, and between two of these membranes is placed a blind interconnector that separates the permeate flows in two sections of membranes, those that are before the blind interconnection and those that are after the blind interconnector, respectively defining two stages and performing a second reverse osmosis step comprising membranes of low pressure and high flow or medium flow and medium pressure and that is fed with a part or all of the water coming from the permeate of the membranes of the first step that are before the blind interconnector, ie the first stage of the first step . (Machine-translation by Google Translate, not legally binding)

Description

Water boron removal procedure and equipment to carry out said procedure.

Object of the invention

The present invention falls within the Procedures for the elimination of seawater boron and equipment to carry out these procedures.

Technical Field of the Invention

The present invention has application in the water desalination industry, more precisely applicable in the purification and desalination of seawater.

State of the art prior to the invention

Currently the procedures of Boron removal from seawater is done by the use of reverse osmosis membranes and combined systems of ion exchange polymeric membranes and resins.

Boron content in seawater ranges between 3.5 and 5.5 parts per million (hereinafter ppm). As a rule In general, seawater membranes have a low rejection of boron and therefore the content of said element in permeated water does not comply with the current regulations of 1 ppm for drinking water human and for some agricultural applications. Moreover, the World Health Organization (hereinafter WHO) recommends that the Boron content in water does not exceed 1 ppm and in the future this level is expected to fall to 0.5 ppm of boron.

Therefore, very technical techniques were developed. specialized to eliminate seawater boron and reach contents established by the regulations in treated waters by reverse osmosis membranes.

Thus, the most used technique for elimination of water boron for human and agricultural consumption, based on water of sea, consists of the use of plants equipped with two reverse osmosis steps with membranes, where a first step is performed with seawater membranes and a second step is performed with brackish water membranes.

Thus, seawater is treated by the first passage of reverse osmosis membranes at high pressure, where they eliminate most of salts and also some percent of boron. As a rule, a concentration of boron is usually obtained of the treated water (hereinafter permeated water) that oscillates, depending on at water temperature, between 0.7 and 1.5 ppm of this element. It should also be noted that reverse osmosis membranes lose, over time and with the successive cleanings to which they are subjected, its ability to eliminate salts and boron.

Experience shows that the content of Boron in permeated water may exceed the current limit of 1 ppm.

In addition, as already mentioned, it is expected that the regulations are modified in this regard, to reduce the content boron allowed in drinking water at 0.5 ppm.

Thus, it is possible to obtain a procedure of elimination of boron that guarantees from the beginning that the boron content in permeated water never exceeds the current limit of 1 ppm and that allows to obtain the desirable limit for the WHO of 0.5 ppm. This procedure ensures that the content obtained do not vary with the operating time, or with the successive chemical cleaning of desalination plants.

To do this, plants are designed with a second passage of reverse osmosis membranes of low pressure brackish water and high workflow. This solution consists in taking part of the permeated water, obtained from the first passage of osmosis membranes Inverse at high pressure, increase the pH to values of 10-11 by adding sodium hydroxide or other strong base and then pump it to a second step. The waters perneadas obtained in the first step and the second step are mixed in appropriate proportions, to minimize the content of boron in the water resulting from the treatment. This system is detailed in figure 1.

Through these systems, all or part of the water coming from the first step of reverse osmosis membranes is treated by the second step of reverse osmosis membranes, after be previously pumped from the first to the second step.

Additionally, it should be borne in mind that in reverse osmosis plants, there are many containers of pressure used to accommodate the membranes, which are connected in series through interconnects. Such containers of pressure can have 6, 7, 8 or more membranes connected in Serie. In addition, in a reverse osmosis plant there are many containers mounted in parallel and that make up what is called membrane frame.

Seawater is fed by one of the faces of the pressure vessel collecting water concentrated in you go out the back of the container and collecting the water with low salt content and low boron content in the center of the container and coming from all the membranes, which are interconnected in series by its central tube.

Thus, the total boron content corresponds to the mixture of the contents of this element of the flows permeated water independent of each membrane located in the pressure container And the concentration of boron in the water Permeate is increasing from the first to the last membrane. In the Figure 2 shows a conventional scheme of a container of pressure of a first step in a conventional system like the one above described

In short, in today's systems pumps the permeated water from the first step, which is a mixture of the permeated from all membranes of that step, to the second step. In addition, in all reverse osmosis, the salinities of the permeate of the membranes increase as their position in the tube increases or pressure container. This makes the working pressures of the second step, be somewhat higher than what you would expect for a low salt water.

It was desirable, therefore, to obtain a procedure of elimination of seawater boron that will prevent the use of a pump in the second step feed, particularly of a booster pump or booster pump.

Description of the invention

The present invention, therefore, seeks avoid using a pump in the second power supply passage, particularly of a pressure booster pump or pump booster That is, the present invention manages to carry out a process for the elimination of seawater boron by means of a reverse osmosis system, which avoids the use of a pump in the second step feed. These systems work taking a percentage of total permeate flow rate from the first step, which is treated in a second step of brackish water membranes, in instead of one hundred percent of the permeate flow rate of the first step.

For this purpose, it is arranged inside the container pressure (or permeate duct) of the first step, of a blind interconnector, also called "blind split", which can place in different positions between two of the membranes existing within each pressure vessel, so separate permeate flows. In this way, the container of pressure works as if it were in two stages, thus obtaining two streams of water permeated at both ends of the container pressure with different boron contents.

Therefore, having an interconnector blind, allows to separate permeate flow rates from the first step to try, later, any of them, in a second step of reverse osmosis membranes.

Once the position of the blind interconnector inside the permeate duct of the first step, permeate flows may be considered to be divided as If it were two stages.

This separation of the membranes by Blind interconnector, will depend on the flow rate, the permeate pressure and of the boron content required in said permeate.

Additionally, the workflow of the flow permeate of each section of membranes can be regulated, if it is requires, exerting a back pressure that may be different value, by means of valves installed in each part of the duct permeated

The second passage of membranes, feeds, like this, with the pressure itself offered by the permeate stream of the First stage, from the first step.

The second step is composed of membranes of Low pressure and high flow.

In a particular embodiment, the interconnector blind is placed between the membranes that occupy positions 3 and 4 and the part or stage of the membrane tube that a minor throws Boron content is between the membranes of positions preferably 1 to 3 of the first step.

In a second particular embodiment, the Blind interconnect is placed between the membranes that occupy the positions 4 and 5 and the part or stage of the membrane tube that throws a lower boron content is that between the membranes of positions preferably 1 to 4 of the first step.

The flow of this stage is the one that will be used to feed the second step of reverse osmosis without the need for intermediate feed pump of the second step, ie without Pump need to increase pressure or booster pump.

Optionally, sodium hydroxide, or a strong base, can be dosed in the feed water of the second step, to raise its pH to values, preferably 10 and 11, since the boron of the permeated water is in the form of boric acid . Alkalinization is convenient to convert boric acid into borate ion, which is best rejected by brackish water membranes. In this way, a better elimination of boron is obtained. Likewise, an antifouling-dispersant compound is dosed to avoid possible scale formation.
nes.

Thus, as stated above, the The present invention relates firstly to a process of elimination of boron from water, preferably from seawater that It is characterized because it comprises:

- perform a first step of reverse osmosis by feeding seawater or brackish water inside a permeate conduit or membrane container comprising a plurality of interconnected membranes in series to work at high or low pressures, depending on the application for seawater or brackish, and between two of these membranes an interconnector is placed blind that separates permeate flow rates into two sections of membranes, those that are before the blind interconnector and those that are after the blind interconnector, defining respectively two stages;

- perform a second reverse osmosis step comprising low pressure and high flow or medium pressure membranes and medium flow and that is fed with a part of the water coming of the permeate of the membranes of the first step that are before Blind interconnector, that is the first stage of the first step.

In addition, inside the membrane container they can place 6, 7 or 8 membranes and the blind interconnector can be placed between any two membranes, preferably between 3-4, 4-5 or the one require.

In a particular embodiment, they are arranged up to 8 membranes inside the permeate duct and the blind interconnector it is placed between the membranes that occupy the positions 3-4 or 4-5.

The membranes that remain before the interconnector blind are the ones that give the highest flow of treated water, very low salinity with respect to the mixture that would be obtained with 7 or 8 membranes For this reason, it is possible to feed the second step without Need for intermediate pump to increase pressure.

Additionally, the flow of work of the permeate flow in the first passage of membranes through the use of flow control valves permeate of both sections separated by the blind interconnector. These valves are installed on each side of the permeate duct to effect a back pressure on the permeate conduction of the membranes of both the first and the second stage of the first He passed. In this way two effects are achieved: acting on the conversion (ratio between permeate water flow and water at treat in the feeding of the membrane duct) of the second step and control the workflow of the first membranes of the First step, that is, those that remain before the interconnector.

Thus, thanks to this regulation of the flow of work by valves, the flow of the first is regulated membranes, that is, those that remain before the blind interconnector and, at the same time, the conversion of permeated water of both is regulated First step stages.

As indicated above, the following procedure stage is optional and involves adding sodium hydroxide, or a strong alkalizing agent, or an alkalizing agent strong and antifouling to a feed stream of the second step, said current coming from the membranes of The first stage of the first step. This is done to increase the pH preferably between 10 and 11, to obtain a better elimination of boron and avoid possible scale formation.

In a second variant of the procedure of boron removal of water described above, when performing second step of reverse osmosis this is fed with the part of the water from the permeate of the membranes of the first step that they are after the blind interconnector, that is the water of the Second stage of the first step.

This second variant involves a stage additional transfer of the residual pressure existing in the permeate water from the first stage of the first step to the permeate of The second stage of the first step. This pressure transfer is performs by means of a hydraulic exchanger device pressures that are sandwiched before feeding the second He passed.

In a third variant of the procedure of removal of boron from the water described above, the supply pressure of the second step by means of a pump very low energy consumption, installed bypass or bypass, to continuation of the hydraulic pressure exchanger device and before feeding the second step.

Additionally, the following is contemplated alternative solution to the procedure described above, to ensure a boron concentration of less than 0.5 ppm in water permeated

In the second embodiment, the water that is sent to the second passage of membranes is that produced by the second stage of the first step. For this a device is used hydraulic pressure transfer, such that the residual pressure in the permeate of the first stage of the first step is transferred to the permeate of the second stage of the first He passed.

The procedure described above, in its Three variants, can be used in all types of water that requires boron elimination, but has been preferably designed for treats seawater or brackish water and preferably will be used to desalinate seawater.

The present invention also relates to a equipment to carry out a boron removal procedure of water as defined above, characterized in that includes at least:

-

a reverse osmosis membrane container comprising a plurality of interconnected membranes in series, the low pressure membranes (low energy consumption) and high flow to work with low pressures, or medium flow membranes and medium pressure;

-

a blind interconnector that is arranged between two membranes of each membrane container, such that said interconnector separate permeate flows from two membrane sections or stages; Y

-

to the minus two flow control valves installed on each side of the permeate duct of the first step.

In a particular embodiment of the equipment, They have up to 8 membranes inside each membrane container (permeate conduit) and the blind interconnector is disposed between the membranes that occupy positions 3-4 or 4-5.

In a first variant, the team up described further comprises a hydraulic transfer device of pressures interspersed in the feeding of the second step, just before the start of it.

In a second variant, the team up described also includes the hydraulic device mentioned in the first variant, a low energy pump, installed bypass or bypass, following said device hydraulic pressure transfer and before the start of second step.

Brief description of the figures

The present invention will be completely included on the basis of the brief description given to continuation and accompanying drawings presented, by way of example only and, in this way, they are not restrictive within the present invention where:

Figure 1 shows a flow chart of a conventional two-step system, existing in the art previous,

Figure 2 shows a flow chart of the first step of a conventional flow distribution system in a 7 'membrane tube, existing in the prior art

Figure 3 shows a scheme of the system of boron removal of the present invention with blind interconnector (2),

Figure 4 shows a scheme of the system of boron removal of the present invention in its first variant, which includes a hydraulic transfer device (12) pressures, and

Figure 5 shows a scheme of the system of boron elimination of the present invention in its second variant, which includes a hydraulic transfer device (12) pressures and a pump (13).

Embodiment of the invention

In order to reach a better understanding of the object and functionality of this patent, and without understanding as restrictive solutions as well

Figure 1 shows a flow chart of a conventional two-step system (10 'and 4'), existing in the prior art, in which you can observe the route that makes the permeate obtained in the first stage of the first step (1 '), the feed pump (2 ') to the second step and dosage optional sodium hydroxide (3 '), or other strong base and antifouling (9 '), before the start of the second step (4'). It also shows the final rejection of the second step (5 ') that joins the rejection of the first step (6') and that is redirected to the first step feed (7 '). On the other hand, and simultaneously, the permeate is obtained at the end of the second step total (8 ') to which the permeate from the first step is attached (one').

Figure 2 shows a flow chart and membrane distribution of the first step of a conventional system in two steps, existing in the prior art in which it is observed the position of the plurality of membranes (A1 ', A2', A3 ', A4', A5 ', A6 'and Al') arranged in the pressure container (9 '). It is noted, also, the place of the water supply (7 ') and the direction of the currents produced, of which the current that crosses the first membranes gives rise to the permeate of the first step (1``), which happens to feed the second step of the procedure and the rejection water of the first step (6 ').

Figure 3 shows a scheme of the system boron removal described by the present invention, wherein You can observe the route that the permeate (1) obtained in the first stage (a) of the first step (I), the position of the plurality of membranes (A1, A2, A3, A4, A5, A6 and A7) arranged in the pressure container or membrane container (9) and the blind interconnector (2) located in the preferred position, between A3 and A4 position membranes. Thus, the current of the membranes at other side of the interconnector gives rise to the permeate (4) of the second step (b) and a rejection (3) of the first step (I). Said rejection (3) of the first step (I) it can either be partially recycled to the entrance of the first step, or evacuate as brine to the sea, as required.

You can see, therefore, the distribution of flows of permeate of the first step of reverse osmosis of seawater with blind interconnector (2).

The part of the membrane container (9) that throws a higher flow rate is, in this particular embodiment where the Blind interconnector (2) is located between the position membranes A3 and A4, the one between the membranes of positions A1 to A3, this flow (1) is the one that will be used to feed the second reverse osmosis step (II) without pressure booster pump (pump booster) intermediate, which works with low membranes pressure and high flow or medium flow and low pressure membranes. Part of the rejection (14) of the second step will be sent to the header of the reverse osmosis plant.

As advantages of the process of the invention The following are indicated:

- the non-use of a booster pump for feed the permeated water (1) from the first step (I) to the second step (II) and its consequent energy savings;

- obtaining boron content values of the total permeate less than 1 ppm, starting from a initial concentration of boron in seawater between 3.5 and 5.5 ppm, and at any seawater temperature;

- the back pressure, necessary to obtain a good membrane performance, is carried out by means of valves rejection (5) located on both sides of the first step (I), of this way is achieved: act on the conversion of the second step and control the workflow of position membranes by example A1 to A3 or A1 to A4 of the different embodiments suggested particulars of the first step; Y

- the permeated water of the first step (4) and the two stages of the second step (6 and 7), are mixed properly until boron concentrations are always lower than 1 ppm.

By the procedure described by the present invention the appropriate mixtures of each can be made permeate current of both the first step and the second step, to obtain a low overall concentration of boron in the water of utilization.

In addition, when working with low membranes pressure and high flow or medium flow and average pressure in the second step, you can work with very low pressures in that step what which avoids installing a booster pump in the supply, with the consequent energy saving.

An additional advantage of working with membranes Low pressure and high flow or medium flow and medium pressure both in the first step as in the second step, is that you get the adequate back pressure in the permeate stream of the first step and of the position membranes preferably A1 to A3, that is the that are located before the blind interconnector (2) in one of the particular embodiments described.

When working with a blind interconnector (2) or "blind split" between position membranes A3-A4 or A4-A5, of the first step and treat the permeated water coming from these membranes the water Permeate is of very low salinity, that is, of low osmotic pressure bringing the working pressure in the second step described In this procedure it is equally very low.

When working without a booster pump in the feed from the second step, a boron elimination process is achieved by reverse osmosis of low energy cost.

The fact that everyone rejection water flows from the second step are sent and mixed with the seawater feed rate at the first step, decreasing the osmotic pressure and therefore the pressure of work, with the consequent energy saving.

Claims (14)

1. Water boron removal procedure characterized in that it comprises: - perform a first step (I) of reverse osmosis by feeding brackish water (8) into a container of reverse osmosis membranes (9) comprising a plurality of membranes (A1, A2, A3, A4, A5, A6 and A7) interconnected in series, and a blind interconnector is placed between two of said membranes (2) which separates the permeate flow rates into two membrane sections, those that are before (a) the blind interconnector (2) and those that are then (b) of the blind interconnector (2), defining respectively two stages (a and b); - perform a second step (II) of osmosis reverse comprising low pressure and high flow or flow membranes medium and medium pressure and that is fed with a part or with the all of the water from the permeate (1) of the membranes of the first step (I) that are before (a) the blind interconnector (2), is say the first stage (a) of the first step (I). 2. Boron water removal method according to claim 1, characterized in that in the first step 6, 7 or 8 membranes are placed in the membrane container (9). 3. Water boron removal method according to claim 1, characterized in that in the first step (I), within the membrane container (9), 7 membranes (A1, A2, A3, A4, A5, A6 and A7) and the blind interconnector (2) is placed between the membranes that occupy the A3-A4 or A4-A5 positions. 4. Water boron elimination process according to claim 1, characterized in that in the first step (I) the workflow of the permeate flow is regulated by means of flow regulation valves (5), installed on each side of the membrane container (9). 5. Boron removal process of water according to claim 1, characterized in that in the second step (II) sodium hydroxide (10), or a strong alkalizing agent, or a strong alkalizing and antifouling (11) is added to a feed stream (1) of said step, said current (1) being from the membranes of the first step to increase the pH. 6. Procedure for eliminating water boron according to claim 1, characterized in that the water to be treated (8) is sea water or brackish water. 7. Boron water removal method according to claim 1, characterized in that when performing the second step (II) of reverse osmosis it is fed with the part of the water from the permeate of the membranes of the first step that are after the blind interconnector (2), that is the water of the second stage of the first step (4). 8. Water boron removal process according to claim 7, characterized in that the residual pressure existing in the permeate water of the first stage (4) of the first step (I) is transferred to the permeate of the second stage of the first step by means of a hydraulic pressure exchanger device (12) that is sandwiched before feeding the second step. 9. Water boron removal method according to claim 8, characterized in that the supply pressure of the second passage is reinforced by means of a low energy consumption pump (13) which is installed after the hydraulic exchanger device (12) pressures and before feeding the second step. 10. Equipment for carrying out a water boron removal process as defined in claim 1, characterized in that it comprises at least:

-

a reverse osmosis membrane container (9) comprising a plurality of membranes (A1, A2, A3, A4, A5, A6 and A7) interconnected in series, the membranes being low pressure and high flow or medium pressure and medium flow;

-

a blind interconnector (2) that is disposed between two membranes of said membrane container (9), such that said interconnector (2) separate permeate flow rates from two membrane sections or stages (a and b); Y

-

to the minus two flow control valves (5) installed in each side of the membrane container (9) of the first step (I).

11. Water boron removal equipment according to claim 10, characterized in that the membrane container has 6, 7 or 8 membranes. 12. Equipment for boron removal according to claim 10, characterized in that 7 or 8 membranes are arranged in the membrane container (9) and the blind interconnector (2) is disposed between the membranes occupying the A3-A4 or A4- positions. TO 5. 13. Equipment for carrying out a water boron removal process as defined in claim 8, characterized in that it comprises at least:

-

a reverse osmosis membrane container (9) comprising a plurality of membranes (A1, A2, A3, A4, A5, A6 and A7) interconnected in series, the membranes being low pressure and high flow or medium pressure and medium flow;

-

a blind interconnector (2) that is disposed between two membranes of said membrane container (9), such that said interconnector (2) separate permeate flow rates from two membrane sections or stages (a and b);

-

to the minus two flow control valves (5) installed in each side of the membrane container (9) of the first step (I); Y

It also includes at least:

-

a hydraulic pressure transfer device (12) interspersed in the feeding of the second step (II).

14. Boron elimination equipment according to claim 13, characterized in that it further comprises a low energy consumption pump (13) installed bypass or bypass, following the hydraulic pressure transfer device (12) and before the start of the second step (II).