• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    Energy recovery process with mixing of reverse osmosis streams from a two-step reverse osmosis operation of a seawater desalination facility, comprising the stages of selecting a first stream (3) of high salinity, selection of a second low salinity current (4), feeding a reverse electrodialysis (EDR) cell (1) with both currents and generating electrical energy in the EDR cell (1) from the saline gradient between both currents, achieving a high energy recovery that can be used to power the desalination plant itself. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2814028A1
    申请号:ES201930824
    申请日:2019-09-24
    公开日:2021-03-25
    发明作者:Mallén Olga Ferrer；Sánchez Jorge Juan Malfeito；Uribe Inmaculada Ortiz；Mendizabal Raquel Ibáñez；Sanz De Aja Alfredo Ortiz
    申请人:Acciona Agua SA；
    IPC主号:
    专利说明:

    [0004] OBJECT OF THE INVENTION
    [0006] The object of the present invention is related to the production of energy from the salinity gradient existing between the reverse osmosis rejection currents in a seawater desalination installation.
    [0008] BACKGROUND OF THE INVENTION
    [0010] The desalination of seawater or brackish water is carried out by two main procedures, the evaporation of water and subsequent condensation of the water vapor, or by means of membrane systems, as in the case of desalination by reverse osmosis, which is carried out at through semi-permeable membranes.
    [0012] Desalination by reverse osmosis is used to produce drinking water for population supply, agricultural irrigation or mainly for industrial purposes.
    [0014] More specifically, in the case of two-step reverse osmosis, a stream of water to be desalinated is subjected to the osmosis process, obtaining water of a lower salinity (permeate) and a first rejection stream, of a high salinity . In the second step, the water of lower salinity obtained in the previous reverse osmosis step (permeate), is again subjected to the reverse osmosis process, resulting in higher quality desalinated water and a second rejection stream.
    [0016] Both in this type of two-step desalination, as in the case of one-step desalination, the passage of sea or brackish water must be forced through membranes, applying a hydraulic pressure higher than the osmotic pressure of the water to be desalinated. , which entail significant energy consumption.
    [0017] To try to reduce energy consumption by these facilities, energy recovery from the salinity gradient has been proposed.
    [0019] The energy contained in the saline gradient (EGS) is a renewable energy obtained by mixing two streams of water with different salinity, which causes the release of energy caused by the difference in chemical potential between both streams.
    [0021] The EGS does not generate greenhouse gases, in addition to having a continuous supply of raw materials, and it does not produce a rise in temperature or waste.
    [0023] One of the main technologies to take advantage of EGS is reverse electrodialysis (EDR). This technology is based on the use of ion exchange membrane pairs that allow the selective passage of ions.
    [0025] In the state of the art it is possible to find different combinations of currents of different salinity that are used to generate energy in an EDR cell, such as those coming from the river and sea, river and effluent from a treatment plant or sea and brine.
    [0027] These currents make it possible to recover part of the energy invested in the reverse osmosis process or in auxiliary systems, reducing the energy consumption of desalination stations.
    [0029] DESCRIPTION OF THE INVENTION
    [0031] The object of the present invention is an energy recovery process with mixed reverse osmosis streams, which come from a two-step reverse osmosis operation.
    [0033] In the first step of said osmosis operation, a first high salinity rejection current is generated, and in the second step a second rejection current is generated, which in this case is low salinity. When both streams understand different salinities, a salinity gradient exists between them.
    [0034] Specifically, the process object of the invention comprises the steps of:
    [0035] - selection of the first high salinity stream from the rejection of the first step of the reverse osmosis operation,
    [0036] - selection of the second low salinity stream from the rejection of the second step of the reverse osmosis operation,
    [0037] - feeding a reverse electrodialysis cell (EDR) with the first current and the second current, and
    [0038] - generation of electrical energy in the EDR cell from the salinity gradient existing between the first high salinity stream and the second low salinity stream.
    [0040] The first stream and the second stream preferably come from a two-step reverse osmosis operation of a seawater desalination facility (IDAM).
    [0042] To maximize energy recovery in the EDR cell, the high salinity stream can have a total solution solids (TDS) concentration between 50,000 and 65,000 ppm and the low salinity stream between 1,500 and 3,500 ppm. Figure 1 shows the power generated in an EDR cell for various combinations of currents of different salinities, and it can be seen that the one that obtains the greatest power generation is the one that results from the rejection currents of the first and second reverse osmosis pass .
    [0044] Specifically, as seen in said figure 1, the ratio of the first high salinity current (Ce) 1M NaCI and the second low salinity current (Cd) 0.02M NaCI and 1M-0.04M NaCI offers maximum powers of 0.93W and 0.80W approximately, higher than other mixes.
    [0046] In addition to achieving superior energy production, the method of the invention also has a number of additional advantages.
    [0048] First, the fouling that occurs in the EDR cell when using reverse osmosis reject currents is lower than when using other currents. As the level of fouling is lower, the decrease in potential energy over time is also lower. Therefore, fewer cell cleanings and easier maintenance are required.
    [0050] As can be seen in figure 2, during fifty days of operation working in recirculation, only three cleanings are necessary. The last two cleanings, which in this case are carried out with warm water at 350C, allow the loss of pressure to be recovered. It is, therefore, as indicated, a low fouling rate and, furthermore, a fouling that can be easily removed, without the need to add chemicals or use aggressive conditions.
    [0052] Another advantage of this procedure is logistics, since the currents used are currents that are produced in the seawater desalination facility itself, and that if not used would be discarded, unlike in other cases, in which Streams of water have to be transported from the sea or from a river to enter the EDR cell.
    [0054] Furthermore, these are pre-treated streams in the seawater desalination facility itself, so no additional pre-conditioning is required. Lastly, as they are reject streams, their pressure can be adjusted to that required in the EDR cell, avoiding the use of supplementary pumping.
    [0056] Finally, since seawater is of a stable composition, the rejection currents that occur in reverse osmosis have a composition that is also stable. This feature facilitates the operation of the EDR cell.
    [0058] Therefore, the process object of the invention achieves energy recovery, by using the rejection currents of the first and second pass of reverse osmosis, which is higher than that obtained with the use of other combinations of currents. Furthermore, the use of these specific currents provides the additional advantages of low EDR cell fouling, as well as the fact that the currents are generated in the facility itself, without the need to transport them from different locations or carry out additional pretreatments.
    [0059] To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, according to a preferred example of a practical embodiment thereof, a set of drawings is attached as an integral part of said description. where, with an illustrative and non-limiting nature, the following has been represented:
    [0061] Figure 1.- Shows a graph of the power generated for different combinations of currents of different salinity (NaCI).
    [0063] Figure 2.- Shows a graph with the evolution of the pressure drop in the EDR cell.
    [0065] Figure 3.- Shows an example of the composition of the rejection currents of the first and second reverse osmosis pass.
    [0067] Figure 4.- Shows a diagram of an EDR cell in which currents of different salinity are introduced to reject reverse osmosis.
    [0069] PREFERRED EMBODIMENT OF THE INVENTION
    [0071] In view of the figures described above, an example of an embodiment of the energy recovery process can be seen with a mixture of reverse osmosis currents, said currents proceeding from a two-step reverse osmosis operation.
    [0073] In the first step of the reverse osmosis operation a first high salinity rejection stream is generated and in the second step a second low salinity rejection stream is generated. When both streams understand different salinities, there is a salinity gradient between them.
    [0075] The process object of the invention comprises a first stage of selection of the first high salinity stream (3) from the rejection of the first step of the reverse osmosis operation, and a second stage of selection of the second low salinity stream (4) from the rejection of the second step of the reverse osmosis operation.
    [0076] These currents come from a two-step reverse osmosis operation of a Seawater Desalination Facility (IDAM).
    [0078] The third step of the procedure is the feeding of a EDR cell (1), which is shown in figure 4 with the first high salinity stream (3) and the second low salinity stream (4).
    [0080] The final step of the procedure is the generation of electrical energy in the EDR cell (1) from the salinity gradient existing between the first stream (3) and the second stream (4).
    [0082] For this, the EDR cell (1) comprises cationic / anionic membranes and electrodes (7). The ions contained in each of the currents migrate towards the cell's electrodes, generating an electric current, which can be used.
    [0084] In order to maximize energy recovery, as seen in Figure 1, the high salinity stream has a total dissolved solids (TDS) concentration between 50,000 and 65,000 ppm and the low salinity stream between 1,500 and 3,500 ppm. Figure 3 shows an example of the specific composition of both streams at a temperature of 25 ° C.
    [0086] The optimal flow ratio in cell (1) is that corresponding to Qd / Qc = 1 when working at the maximum flow rate allowed by the manufacturer, with Qd and Qc being the flow rates of the second low salinity stream (4) and the first high salinity stream (3), respectively.
    [0088] The speed of the currents is in the range of 1-3 cm / s of linear speed, imposed, together with the pressure requirements, by the manufacturer of the EDR cell (1). For example, for a cell (1) with a membrane area of 200 cm2, differential pressure limits of 0.2 bar are established between compartments and between 0.2 and 1 bar between the inlet (5) and the outlet (6 ) of each stream.
    [0090] Knowing the flow of the first stream (3) and the second stream (4), with the values of the parameters indicated above (Qd / Qc = 1 and speed 1 - 3 cm / s), the power capable of being delivered by currents (2.2 - 2.5 W / m2), and the boundary conditions to be considered (maximum pressures), the surface of the cell membranes can be determined (1) EDR, and consequently, the specific EDR cell to be selected, as well as the combinations of the membranes in it if applicable (place them in series / parallel), and the total power that can be obtained.
    [0092] To carry out the necessary cleanings of the EDR cell (1), when required by the pressure limits previously described, it will be necessary to carry out a countercurrent cleaning using low salinity water and a recommended temperature close to 350C at flow rates between those of work and double this value (as long as it does not exceed the maximum speed recommended by the manufacturer). Figure 2 shows a graph that reflects the evolution of the pressure drop in cell (1) EDR during fifty days.
    [0094] Regarding the characteristics of the electrodes (7) of the EDR cell (1), a composition of 0.05 MK 3 Fe (CN) 6 , 0.05 MK 4 Fe (CN) 6 , and 0.25 M NaCI. They are replaced every 24 hours.
    权利要求:
    Claims (5)
    [1]
    1. - Energy recovery procedure with a mixture of reverse osmosis currents from a two-step reverse osmosis operation, in which a first high salinity rejection current (3) is generated in the first step and in the second A second low salinity rejection stream (4) passed, with a salinity gradient between the streams, the procedure being characterized by the steps of:
    - selection of the first high salinity stream (3) from the rejection of the first step of the reverse osmosis operation,
    - selection of the second low salinity stream (4) from the rejection of the second step of the reverse osmosis operation,
    - feeding a cell (1) for reverse electrodialysis (EDR) with the first current (3) and the second current (4), and
    - generation of electrical energy in EDR cell (1) from the salinity gradient existing between the first high salinity stream (3) and the second low salinity stream (4).
    [2]
    2. - The method of claim 1, in which the first stream (3) and the second stream (4) come from a two-step reverse osmosis operation of a Seawater Desalination Facility (IDAM).
    [3]
    3. - The process of claim 1, wherein the first high salinity stream (3) has a concentration of total dissolved solids (TDS) between 50,000 and 65,000 ppm.
    [4]
    4. - The process of claim 1, wherein the second low salinity stream (4) has a concentration of total dissolved solids (TDS) between 1,500 and 3,500 ppm.
    [5]
    5. - The method of claim 1, further comprising a cleaning step of the EDR cell (1).
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    同族专利:
    公开号 | 公开日
    ES2814028B2|2021-08-04|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    EP1746680A1|2005-07-20|2007-01-24|Vlaamse Instelling Voor Technologisch Onderzoek |Combination of a desalination plant and a salinity gradient power reverse electrodialysis plant and use thereof|
    US20110044824A1|2009-08-18|2011-02-24|Maher Isaac Kelada|Induced symbiotic osmosis [iso] for salinity power generation|
    WO2012070468A1|2010-11-22|2012-05-31|三菱重工環境・化学エンジニアリング株式会社|Seawater electrolysis system and seawater electrolysis method|
    CN106630359A|2017-02-10|2017-05-10|碧海舟（北京）节能环保装备有限公司|Clean energy seawater desalination and salt making system|
    法律状态:
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