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    • 专利摘要:
    The present invention relates to a novel multistage membrane process technology that enables producing a potable water product from saline water feed at a high water recovery, reduced osmotic pressure differential and competitive net specific energy consumption (SECnet) while simultaneously reducing the boron concentration to the level recommended for both human consumption and crop irrigation.
    公开号:ES2672787A2
    申请号:ES201890008
    申请日:2016-10-19
    公开日:2018-06-18
    发明作者:William Bernard Krantz；Sadiye VELIOGLU；Suer KURKLU；Mehmet Goktug AHUNBAY；Serife Birgul ERSOLMAZ
    申请人:Istanbul Teknik Univ Rektorlugu；ISTANBUL TEKNIK UNIVERSITESI REKTORLUGU；
    IPC主号:
    专利说明:

    image 1 DESCRIPTION
    Concurrent procedure for desalination and boron withdrawal (CDBR). Technical Field of the Invention
    The present invention relates to a new membrane process technology
    5 multistage that allows to produce a drinking water product of saline water feeding with a high water recovery, reduced osmotic pressure differential and competitive net specific energy consumption (SECnet) simultaneously reducing the concentration of boron to the recommended level both for consumption human as for crop irrigation. 10 Prior art of the invention
    There is a continuing need to improve efficiency and reduce the cost of drinking water supply due to the pressures of an expanding world population, demographic changes and global climate change. Nearly 700 million people in the world lack access to safe drinking water. In January 2015, the World Economic Forum
    15 announced that the water crisis is the main global risk based on the impact on society. The irrigation of crops associated with the food sector of the world economy uses 70% of the world's fresh water. Additional sources need to be used to meet the growing demand for water for both human consumption and crop irrigation.
    20 Oceans that contain 97% of the water on earth are a great resource. However, ocean water can contain as much as 50,000 parts per million (ppm) of salt (sodium chloride) and other low molecular weight solutes that make it inappropriate for human consumption or irrigation without treatment. Reverse osmosis (RO) has become an important technology for the production of drinking water from
    25 seawater, as well as in brackish inland waters that have a salt content ranging from 500 ppm to 30,000 ppm. RO uses a high pressure salt rejection membrane to force water to penetrate through the membrane while rejecting salt and other solutes. Conventional RO technology requires a very high pressure, typically 50 bar or more, which contributes significantly to the cost of desalination of the
    30 water In addition, conventional RO technology has a limited potable water recovery, typically 50%, due to the very high pressures required to achieve greater water recoveries. As a result, the specific energy consumption (SEC) to produce drinking water from saline water is quite high. To reduce a salt concentration of 35,000 ppm in seawater to 350 ppm in the processed water, the conventional single stage reverse osmosis (SSRO) operating at a pressure of 55.5 bar and a 50% water recovery using A membrane with a salt rejection of 0.990 requires a net SEC of 2,242 kWh / m3 (kilowatt hours of energy per cubic meter of processed water). For this reason, the cost of water obtained via desalination is more than double the cost of water obtained from freshwater sources.
    image2
    A concurrent problem is that typical seawater contains 10 ppm or more of boron. The World Health Organization (WHO) has recommended that the maximum concentration of boron in water for human consumption should be below 2.4 ppm and for irrigation should be below 0.5 ppm, especially for Citrus and peel orchards. Boron is present in seawater as boric acid, which is only slightly larger than clusters of hydrogen-bound water molecules. Accordingly, conventional RO membranes have relatively low boron rejections, typically less than 90%, and therefore cannot reduce the boron concentration via conventional desalination technologies to a concentration of 0.5 ppm. Higher boron rejections with current RO membranes are possible if the pH (logarithm of the hydrogen ion concentration) of the feed solution to the membrane process is increased above the pK (logarithm of the dissociation constant) of 9, 14 for the ionization of boric acid to borate ions, which when hydrated are sufficiently larger than hydrogen bound water molecules to allow adequate rejection via commercial RO membranes. However, this procedure is expensive since it requires reducing the highly alkaline pH after boron removal. Boron removal from seawater is usually performed as a post-treatment procedure after desalination. However, this is also expensive since large volumes of water must be processed twice, once for desalination and again for boron removal. Concurrent boron desalination and desalination (CDBR) is attractive but challenging due to poor rejections of commercially available RO membranes.
    The prior art patents related to the present invention are listed below;
    . The US Provisional Patent Application No. 61 / 972,718 describes the energy efficient reverse osmosis (EERO) procedure. Although the new CDBR invention described here incorporates the energy-saving features of the EERO process, it is substantially different in that it uses an additional low pressure membrane (LPMS) stage to produce a filtering current with a very low boron concentration. which is mixed with the filtering current of the CMCR to achieve the desired boron concentration.
    image3
    . U.S. Pat. 9108865 describes a treatment method for boron-containing water that involves two serial procedures: the first procedure uses evaporation to concentrate the boron; the second uses different inorganic hydroxides to further reduce boron by adsorption. This procedure is mainly used to reduce very high concentrations of aqueous boron (typically 1x106 ppm) to a lower concentration (typically ~ 1x105 ppm). While boron withdrawal is 85.7% for a feed concentration of 1x106 ppm, it decreases to 68.3% for a feed concentration of 2.5x105 ppm. Therefore, this procedure would have a very low boron removal for typical seawater, whose concentration of boron is 10 ppm and, therefore, could not achieve the target product concentration of 0.5 ppm.
    . U.S. Pat. 9090491 first involves reducing the concentration of boron in seawater to less than 0.2 ppm by increasing the pH between 8.5 and 10 using an alkaline product in an NF membrane stage. The filtrate of this stage is mixed with that of a high pressure RO stage (82 bar) that both desalinates the water and reduces the concentration of boron to less than 1 ppm so that the boron in the mixed filtrate has a concentration less than 0.2 ppm. This procedure involves series instead of desalination and withdrawal of concurrent boron. It requires adding alkaline chemicals to increase the pH that must be reduced again to an almost neutral pH in the final product. In addition, the RO part of this two-stage procedure requires a very high pressure. The invention of CDBR concurrently removes salt and boron without the addition of any chemical and operates at a considerably lower pressure.
    . U.S. Patents UU. 9073763 and 8617398 involve a series of two stages, a high pressure RO stage and an ion exchange stage. Alkaline chemicals are added to the feed to increase its pH to as high as 11 to improve membrane boron rejection in the RO stage. Additional boron removal is achieved via an ion exchange stage. In contrast to the invention of CDBR described here, this procedure does not achieve desalination and removal of concurrent boron, requires the addition and subsequent removal of chemicals to change the pH, and requires high pressure operation at the RO stage. In addition, This procedure requires the regeneration of the ion exchange resin.
    image4
    -US Patent UU. 8999171 uses ultrafiltration, air extraction, nanofiltration and addition of chemicals to obtain a pH between 9.5 and 10 as a pretreatment for a low pressure RO salt water feed followed by electrodialysis to achieve 0.5 ppm of boron in the processed water This procedure is much more complex than the invention of CDBR. In particular, it does not imply desalination and removal of concurrent boron and also requires adjusting the pH.
    -The U.S. Patent 8357300 describes the serial assembly of RO and ultrafiltration (UF) in which the complexation of the boron with micelles allows the appropriate rejection to achieve very low concentrations of boron. In contrast to the CDBR invention described herein, this procedure does not involve desalination and concurrent boron removal and also requires higher pressure operation due to the RO stage. It also requires regeneration of micelles.
    -US Patent 7618538 describes an RO membrane procedure that uses one or more metals together with at least one anti-scale dispersing agent for desalination and boron removal from seawater. Use an alkalizing agent to increase the pH to between 8 and 9.5. This procedure requires readjusting the pH again to almost neutral levels to obtain satisfactory processed water. Since it implies conventional RO, it will necessarily work at higher pressures. The invention of CDBR does not require any chemical addition or pH adjustment and can operate at substantially lower pressures than conventional RO.
    -US Patent 7442309 also uses RO for desalination and boron removal that is facilitated by the addition of chemical to increase the pH to as high as 9.5. The pH should be reduced after boron removal to obtain a satisfactory processed water. Since this procedure involves conventional RO, it will necessarily work at higher pressures. The invention of CDBR does not require the addition of any chemical for pH adjustment and can achieve desalination at substantially lower pressures than conventional reverse osmosis.
    -US Patent 7368058 describes a procedure that involves RO and adsorption steps to achieve desalination and boron removal. Requires regeneration of the adsorbent. Since it implies conventional RO, it will necessarily work at high pressures. The invention of CDBR achieves the desalination and removal of concurrent boron at substantially lower pressure than conventional RO and does not require the use of an adsorbent.
    image5
    -US Patent 7264737 involves the serial assembly of two RO stages or an RO stage and an electrodialysis stage to achieve desalination and boron removal. Since it implies conventional RO, it must necessarily operate at high pressure. Series mounting in this way necessarily reduces the total water recovery since the feed to the second stage is the filtering of the first stage. The invention of CDBR described here achieves a higher total water recovery by processing both the filtrate and the retained fraction of the first RO stage. In addition, the invention of CDBR operates at a considerably lower pressure.
    -US Patent 7097769 uses multistage RO separation for desalination and concurrent boron removal. The alkaline chemicals are added in the second stage of RO to increase the pH above 9. As such, the pH of the processed water of this multistage process has to be adjusted down again to an almost neutral pH. In addition, since it uses conventional RO, it must operate at high pressure. The CDBR invention described herein does not require the addition of any chemical to adjust the pH and operates at a considerably reduced pressure.
    -US Patent No. 5833846 describes a high purity water production apparatus that reduces the concentration of boron to less than 10 ppt. However, it is a complex procedure that involves a dual step RO stage unit and another stage that involves electrodialysis or distillation individually or in combination. This procedure has a complex design that does not imply simultaneous desalination and boron removal. In addition, the use of conventional RO necessarily requires higher pressure operation. The CDBR invention described herein involves a relatively simple procedure design that allows concurrent desalination and boron removal and allows operation at substantially lower pressure.
    -US Patent 5250185 uses the addition of alkaline chemicals to raise the pH in order to increase boron rejection in a RO membrane stage. Chemicals added to increase the pH should be removed in the processed water of this procedure. Since this procedure uses conventional single stage RO, it necessarily works at higher pressure. The invention of CDBR does not require the addition of any chemical and allows operation at substantially lower pressure.
    image6
    -US Patent 4755298 describes a continuous cyclic process for the removal of boron ions from aqueous streams via absorption and binding to a chelating agent. Polymers having N-alkylglucamine as branching or its derivatives serve as chelating agents to bind to boron which can subsequently be released by treatment with a dilute aqueous mineral acid. While this procedure can effectively reduce the concentration of boron, it does not address concurrent desalination. To achieve desalination and boron removal, this procedure would have to be used in series with conventional RO or some other separation technology to reduce salt concentration. The invention of CDBR achieves the desalination and removal of boron concurrently.
    No prior patent involves a procedure to concurrently carry out the desalination and removal of boron to achieve concentrations of processed water of less than 350 ppm of salt and 0.5 ppm of boron and that require only multistage membrane separations at a significantly reduced pressure while not require the addition of chemicals to increase the pH.
    This invention is a new membrane technology called a concurrent boron desalination and desalination process (CDBR). The invention of CDBR allows water desalination and boron removal to be carried out at the same time using membrane technology to achieve the desired concentrations in the processed water. The SEC for conventional RO procedure technology is high due to the large osmotic pressure differential (OPD) between a concentrated salt solution and almost pure water and because the water recovery is relatively low. This CDBR invention takes advantage of the energy efficient reverse osmosis (EERO) method of recent invention. The EERO procedure reduces OPD and increases water recovery through a judicious combination of one-stage reverse osmosis (SSRO) and a countercurrent membrane cascade with recycled (CMCR). However, the EERO procedure cannot reduce the typical concentration of boron in seawater to an acceptable level in processed water. Brief description and objectives of the invention
    The present invention uses membrane technology to concurrently desalinate a salt water feed and reduce the boron concentration to 0.5 ppm or less at lower operating pressures, greater water recovery and lower specific energy consumption. The prior art involves desalination followed by boron removal or requires the addition of chemicals to increase the pH (logarithm of the hydrogen ion concentration) to allow proper removal of the boron.
    image7
    5 Any chemical added to increase the pH should be removed in the processed water. The prior art using conventional reverse osmosis necessarily works at higher pressures than this new CDBR invention.
    In fact; The present invention makes use of the characteristics of the EERO process that allows it to reduce OPD and increase water recovery, but also makes a substantial addition to the process technology to allow concurrent boron removal to an acceptable level using membranes. RO currently commercially available. In an embodiment of this new CDBR invention, the retained fraction product of the high pressure side of an SSRO stage is optimally introduced at a point between two stages in a CMCR. The filtering of the 15 SSRO stage is sent as feed to a low pressure membrane (LPMS) stage to achieve more boron removal. The CMCR filtrate is mixed with the LPMS filtrate to achieve the desired boron concentration in the drinking water product. This new procedure configuration achieves the desired concentration of boron in a stream of drinking water product at a significantly reduced OPD 20, high water recovery and competitive SEC. Get this
    (i) introducing the retained fraction of the SSRO stage optimally as a feed to the CMCR; (ii) the countercurrent flow of fraction retained and filtered in the CMCR; (iii) recycle the filtrate next to the fraction retained in the CMCR; (iv) self-recycle the retained fraction in at least one of the membrane stages in the CMCR; (v) 25 introducing the filtering of the SSRO stage as feeding to an LPMS; and (vi) mixing the filtration streams of CMCR and LPMS to achieve the desired concentrations in the water product. Filtering recycling involves sending the filtering current of a stage to the side of the retained fraction (high pressure) of the stage immediately downstream of it (that is, in the direction of the filtrate flow). The self-recycling of the retained fraction 30 involves sending part of the retained fraction to the filtrate side of the same stage; This can be done using a nanofiltration (NF) membrane whose salt rejection is considerably less than that of an RO membrane. The configuration of the CDBR procedure is energy efficient because (i) the SSRO in combination with the CMCR reduces the OPD; (ii) the LPMS works at very low
    35 pressure relative to an RO stage; and (iii) the mixing of the LPMS and CMCR filtering products minimizes the amount of water that must pass through the LPMS to reduce the boron concentration.
    image8 Definition of the figures describing the invention
    Figure 1. The scheme of the 4-stage embodiment of the CDBR invention whereby the
    5 high pressure retained fraction of stage 1, an RO stage, is the feed to a CMCR consisting of stage 2, an NF stage and stage 3, an RO stage and filtering is the feed for stage 4 , an LPMS. The CMCR employs recycle filtering from stage 2 to the high pressure side of stage 3 and recycling the retained fraction from the high to low pressure side of stage 2 via an NF membrane. The currents of
    10 filtered from stage 3 and stage 4 are mixed to achieve the desired concentrations of salt and boron.
    Figure 2. (a) Osmotic pressure difference and (b) Specific net energy consumption in the CDBR invention as a function of total water recovery values ranging from 50% to 75%. These results are for a diet that contains 35,000
    15 ppm of salt and 10 ppm of boron and a drinking water product that contains no more than 350 ppm of salt and 0.5 ppm of boron. The values are compared with those of the conventional SSRO for desalination that cannot reduce the boron concentration to 0.5 ppm.
    Figure 3a. The scheme of an alternative embodiment of the CDBR invention: CDBR-B,
    20 in which the filtering current of Stage 1 is divided into two fractions by means of a flow divider, and one fraction is fed to Stage 4, while the other fraction circles Stage 4 to mix with the streams of filtered leaving Stage 4 and Stage 3.
    Figure 3b The scheme of an alternative embodiment of the invention CDBR-B: CDBR-BR,
    25 in which the retained fraction of Stage 4 is totally or partially recycled as feed to Stage 1.
    Figure 4. The scheme of an alternative embodiment of the invention of CDBR with two stages of SSRO in which the salt water feed is introduced into the high pressure side of the first stage of SSRO and the retained fraction of the first stage of SSRO
    30 is introduced on the high pressure side of the second stage of SSRO while the retained fraction of the second stage of SSRO is introduced into the CMCR unit.
    Detailed description of the invention
    image9
    The present invention involves an SSRO stage (stage 1) whose retained fraction stream serves as the feed to a two stage CMCR (stages 2 and 3) and whose filtering stream serves as a feed to an LPMS (stage 4). Figure 1 is a diagram showing the 4-stage embodiment of this CDBR invention. Step 5 10 on the right in Figure 1) and the direction of the filtrate flow in the CMCR is called downstream direction (on the left in Figure 1). In Figure 1, the current of the retained fraction (high pressure) of stage 1 is introduced between stages 2 and 3 in the CMCR. In another embodiment of the CDBR invention, the CMCR could involve more than two stages in which case the retained fraction stream of stage 1 would be optimally introduced between two stages in the CMCR. The optimum point is that in which the concentration of the current of the retained fraction of stage 1 that serves as feed to the CMCR is the closest to that of the retained fraction of the stage immediately downstream and the recycle stream of filtered immediately upstream of the point where the feed is introduced. In the 4-stage embodiment of this invention shown in Figure 1, the CMCR operates at the same pressure as the retained fraction stream of stage 1, which implies that a pressure lift pump is not required for the power to the CMCR. When more than two stages are used in the CMCR, all stages can be operated at the same pressure, which means that no pumping between stages is required on the high pressure side of the CMCR. Alternatively, the pressure can be reduced between successive stages in the direction of the flow of the fraction retained in the CMCR to reduce the OPD at the expense of reduced water recovery. The filtering current of step 1 is introduced as the feed to an LPMS (step 4) in order to reduce its boron concentration. Step 4 can be carried out at a pressure only slightly higher than the ambient pressure, since there is very little difference in the salt concentration between the feed and the filtering sides of the membrane at this stage. The concentration of boron in the filtrate from step 4 will be well below 0.5 ppm. Therefore, to achieve the desired concentration of boron in the product stream, the filtrate from step 4 is mixed with the filtrate from step 3 in the CMCR whose boron concentration 35 is usually greater than 0.5 ppm for a feed of typical saline water that
    It contains 10 ppm of boron.
    image10
    The way in which this CDBR invention reduces SEC while reducing OPD, increasing water recovery, and achieving the desired salt and boron concentrations will first be explained in qualitative terms, after which the realization of this invention shown in the Figure 1 will be analyzed quantitatively. 5 Note that the analysis performed here is for the operation of stage 1 and the CMCR stages at the thermodynamic limit. However, the thermodynamic limit is not relevant for stage 4 for which the required pressure difference is determined from the volumetric flow of the filtrate and the membrane permeability coefficient at this stage. The design at the thermodynamic limit implies that the pressure is just equal to that required to overcome the OPD due to the difference in concentration between the high and low pressure sides of the membrane. Small pressure losses in the conduits leading to and from the membrane stages or within the membrane modules on the high pressure side or to cause filtration through the membranes are not taken into account. This is a standard practice for
    15 determine the efficiency of a membrane procedure and will be used to evaluate the performance of this CDBR invention for concurrent desalination and boron removal, as well as to determine the performance of conventional SSRO for desalination in the absence of boron removal, which is used as the basis for comparison.
    This CDBR invention combines SSRO with a CMCR by sending the current of the retained fraction of the SSRO as the power of the CMCR. In Figure 1, the current of the retained fraction of stage 1 is introduced as feed between stages 2 and 3 of the CMCR. By introducing the retained fraction of stage 1 as a feed for the CMCR, more water can be recovered, which contributes to reducing the
    25 SEC. This can be done without increasing the OPD to minimize the pumping costs that contribute to the SEC. Therefore, an embodiment of this invention of CDBR involves operating the CMCR at the same pressure as the current of the retained fraction of stage 1 and not employing pumping between stages on the high pressure side (retained fraction) of the CMCR . Since the retained fraction of the SSRO has a salt concentration
    30 higher than that of the saline water supply to the SSRO, the operation of the CMCR without any pumping between stages requires the reduction of the OPD in the CMCR. This is done by recycling the filtrate from stage 2 to the high pressure side of stage 3 in the CMCR, while at the same time a membrane is used in stage 2 that lets in more salt than the highly rejecting membrane used in the
    35 stage 3. The recycling combination of the filtrate from stage 2 to the high pressure side of
    image11
    stage 3 and some salt filtering from the high pressure side to the membrane filtering side in stage 2 reduces the difference in concentration across the membranes in both stages 2 and 3, thereby allowing high water recovery without the need to increase the pressure beyond that of the current of the retained fraction of step 1. Another embodiment of this invention of CDBR would allow a decrease or increase in pressure of the point at which the feed is introduced into the direction of the flow of the retained fraction, which is to the right in Figure 1. In particular, lowering or increasing the pressure can be used to decrease or increase the recovery in step 2 to compensate for not being able to obtain a NF membrane with optimal salt rejection. The concentration of boron in the CMCR filtrate will usually be greater than 0.5 ppm since the CMCR is processing the retained fraction of stage 1, whose boron concentration will be much higher than that of saline water fed to this stage. Accordingly, to achieve the desired boron concentration, the filtrate of stage 1, whose concentration of boron is already significantly reduced from the feed to this stage, serves as feed to stage 4, an LPMS. The latter employs a membrane with a boron rejection similar to that of the membrane in step 1 and, therefore, reduces the concentration of boron well below 0.5 ppm. The filtrate of stage 4 is mixed in the appropriate proportion with that of stage 3 in the CMCR in order to achieve the desired boron concentration
    20 in the mixed product stream. This configuration in the CDBR concurrently achieves desalination and boron withdrawal, while minimizing the amount of water that is sent to stage 4.
    To quantitatively demonstrate that this invention of CDBR can achieve a boron withdrawal of up to 0.5 ppm concurrently with the desalination of water of 25 sea to produce a drinking water product having a salt concentration of less than 350 ppm with a high water recovery, reduced OPD and competitive SEC, the mathematical equations that describe the interrelation between the volumetric flows denoted by Qi in Figure 1, and the salt and boron concentrations expressed as mass per unit volume and denoted by Csi and Cbi, respectively, in Figure 1,
    30 in which the subscript 'i' denotes the location of the particular current or concentration, will be solved analytically. The solution to this system of algebraic equations will allow to determine the recovery, OPD, SEC, and salt and boron rejections initially not specified in each stage of the CDBR and LPMS.
    The analysis of this 4-stage CDBR invention involves solving the overall balances of material and solute for each of the four stages and at the two mixing points.
    image12
    The balances in stage 1 constitute 3 equations that involve 9 unknowns (Qf, Cfs, Cfb, Q0, C0s, C0b, Q1, C1s, C1b). The balances in stage 2 constitute 3 equations that involve 9 unknowns (Q2, C2s, C2b, Q4, C4s, C4b, Q6, C6s, C6b). The balances in stage 3 constitute 3 equations that involve 6 unknowns (Q3, C3s, C3b, Q5, C5s, C5b). The 5 balances in stage 4 constitute 3 equations with 6 unknowns (Q7, C7s, C7b, Q8, C8s, C8b). The balances at the mixing point between stages 2 and 3 constitute 3 equations and 0 unknowns. The balances at the mixing point where the filtering currents of stages 3 and 4 are mixed constitute 3 equations with 3 unknowns (Q9, C9s, C9b). This adds up to 18 equations that involve 33 unknowns. This implies 15 degrees of freedom
    10 to solve the equations for this 4-stage CDBR procedure.
    The 15 degrees of freedom were met by specifying the following amounts shown in the previous figure:
    one. Qf, saline water feed rate to stage 1
    2. Cfs, salt concentration in the feed to stage 1
    15 3. Cfb, concentration of boron in the feed to stage 1
    Four. C9b, boron concentration in the mixed filtering streams of stages 3 and 4
    5. C0s = C3s required to have the OPD in the CMCR equal to the OPD in stage 1
    6. Δπ1, OPD in stage 1
    7. Δπ1 = Δπ3, equal OPDs in stages 2 and 3 of the CMCR
    20 8. Y2, recovery in stage 2
    9. Y3, recovery in stage 3
    10. Y4, recovery in stage 4
    eleven. σ1s, salt rejection in stage 1
    12. σ1b, boron rejection in stage 1 (in proportion to salt rejection in stage 25 1)
    13. σ2b, boron rejection in stage 2 (in proportion to salt rejection in stage 2)
    14. σ3b, boron rejection in stage 3 (in proportion to salt rejection in stage 3)
    fifteen. σ4s, salt rejection in stage 4 (in proportion to boron rejection in stage 4)
    image13
    The specification of the 15 quantities is not unique. You could specify the values of other input parameters.
    5 Total and solute mass balances for stage 1 are given by the following:
    Qf = Q0 + Q1 (1) QfCfs = Q0C0s + Q1C1s (2) QfCfb = Q0C0b + Q1C1b (3)
    The total and solute mass balances for stage 2 are given by the following:
    10 Q6 = Q2 + Q4 (4) Q6C6s = Q2C2s + Q4C4s (5) Q6C6b = Q2C2b + Q4C4b (6)
    The total and solute mass balances for stage 3 are given by the following:
    Q4 = Q3 + Q5 (7)
    15 Q4C4s = Q3C3s + Q5C5s (8) Q4C4b = Q3C3b + Q5C5b (9)
    The total and solute mass balances for stage 4 are given by the following:
    Q0 = Q7 + Q8 (10) Q0C0s = Q7C7s + Q8C8s (11) 20 Q0C0b = Q7C7b + Q8C8b (12)
    The total and solute mass balances at the mixing point between stages 2 and 3 are given by the following:
    Q6 = Q1 + Q5 (13) Q6C6s = Q1C1s + Q5C5s (14) 25 Q6C6b = Q1C1b + Q5C5b (15)
    The total and solute mass balances at the point where the filtering currents of stages 3 and 4 are mixed are given by the following:
    Q9 = Q3 + Q7 (16) Q9C9s = Q3C3s + Q7C7s (17) 30 Q9C9b = Q3C3b + Q7C7b (18)
    image14
    The additional equations that relate the volumetric flows and concentrations are given by the following: Δπ1 = K (C1s - C0s) the OPD is specified in stage 1 (19) Δπ1 = Δπ3ΩC2s - C4s = C5s - C3s the OPDs set equal in the CMCR (20)
    image15
    Solving these equations gives the following for volumetric flows:
    image16
    Solve for salt concentrations gives the following:
    image17
    image18
    Solve for boron concentrations gives the following:
    image19
    image20
    The pressure required in stage 4 is given by the following:
    image21
    in which P4 is the membrane permeability coefficient in stage 4. The total water recovery of that 4-stage CDBR procedure is given by the following:
    Y = Q9 (59)
    The specific net energy consumption (SEC) net, which is the energy required per unit of water produced allowing the recovery of the pressure energy in the fraction retained via an energy recovery device (ERD), is given by the following:
    image22
    in which ηp is the efficiency of the pumps and ηERD is the efficiency of the ERD.
    The predictions of equations (29) - (60) will be used to establish the proof of concept for this CDBR invention. The performance of the CDBR invention will be evaluated in terms of OPD and SECnet required to produce a water product.
    15 containing 0.5 ppm of boron and not more than 350 ppm of salt from a salt water feed containing 35,000 ppm of salt and 10 ppm of boron. Fractional water recovery values for stages 2 and 3 are input parameters to solve the model equations, which were chosen to be 0.3 and 0.7, respectively.
    20 The execution of stage 2 at a lower recovery increases the safety factor (flow ratio of fraction retained to filtered) at this stage, thereby helping to mitigate concentration polarization and clogging at this stage that has a feed that It contains a high concentration of divalent salts. It is possible to execute stage 3 to a greater recovery since the feeding to this stage has gone through both the
    25 stage 1 as per stage 2, thereby removing all divalent salts that could cause scale. The feed to stage 4 is almost pure water since it has gone through stage 1, an RO stage; therefore, the OPD in step 4 is insignificant. In addition, the colmatants have been removed in the feed to stage 4.
    image23
    Therefore, step 4 can be executed at a very high water recovery or equivalent to a very low safety factor. The only requirement is that there is sufficient flow of retained fraction to remove the small amount of boron rejected by the membrane in step 4. Accordingly, it is assumed that step 4 has a 95% water recovery. Pumping and ERD efficiencies of 85% and 90%, respectively, are assumed, which are consistent with commercially available devices. The performance of the CDBR invention will be evaluated in terms of OPD and SECnet required to achieve the specified boron and salt concentrations in the processed water for a variety of total water recoveries. The implications in the invention of CDBR of using membranes having a salt rejection interval and a boron rejection interval will also be evaluated. While salt and boron rejections are input parameters specified for stage 1, salt rejections are predicted amounts in stages 2 and 3, and boron rejection is a predicted amount in stage 4. For stages 2 and 3 the boron rejection is provided to the predicted salt rejection, while in step 4 the salt rejection is provided to the predicted boron rejection; that is, it is assumed that the relationship between boron rejection and salt rejection is the same as that which can be achieved through commercially available membranes that can achieve rejections of 90.0% and 99.7% for boron and salt, respectively.
    The OPD is a specified input parameter used to solve equations (1) through (28) for volumetric flows and concentrations in the invention of CDBR. Total water recovery is determined from equation (59) using the volumetric flows determined from equations (29) through (38). Figure 2 shows a graph of OPD and SECnet as a function of total water recovery ranging from 50% to 75%; These predictions are to achieve a processed water with a salt concentration equal to or less than 350 ppm and a boron concentration of 0.5 ppm, which both meet the WHO recommendations for drinking and irrigation water. The salt and boron rejections of the membranes for stages 1 to 4 and the recovery in stage 2 are summarized in Table 1. Figure 2 also shows the OPD and the SEC for SSRO that cannot achieve 0.5 ppm of Boron concentration in processed water.
    Table 1. Required salt and boron rejections and recovery in stage 2 in the CDBR invention for both desalination and boron removal that produces a water product with a salt concentration equal to 350 ppm and a boron concentration 0.5 ppm.


    Recovery σ1sσ2sσ3sσ4sσ1bσ2bσ3bσ4bY2
    fifty% 0.9970.8330.9900.5450.9000.7520.8940.4920.165
    65% 0.9970.6600.9960.6450.9000.5960.8990.5820.339
    75% 0.9960.5430.9970.7310.8990.4900.9000.6600.456
    It is of interest to determine the minimum value of boron rejection required for the invention of CDBR to produce processed water containing no more than 350 ppm of salt and a specified boron concentration of 0.5 ppm and determine the implications for the invention of CDBR if membranes with boron rejections greater than 90% could be obtained. Figure 3 shows a graph of the boron rejection of the membrane in stage 4 as a function of the specified boron rejection of the membrane in Stage 1 required to achieve a processed water containing no more than 350 ppm of salt and a concentration of specified boron of 0.5 ppm for total water recovery values of 50%, 65% and 75%. Table 2 indicates that the specified water product concentrations can be achieved even with a membrane having a boron rejection as low as 0.804, 0.834 and 0.851 for total water recovery values of 50%, 65% and 75%, respectively. These boron rejections are well below the 0.90 boron rejection achievable via RO membranes
    15 commercials currently available.
    Table 2. Minimum boron rejections in the invention of CDBR for total water recovery values of 50%, 65% and 75% required to produce a water product having a salt concentration equal to or less than 350 ppm and a concentration of specified boron of 0.5 ppm.
    Recovery σ1bσ2bσ3bσ4b
    fifty% 0.8040.6720.7980.803
    65% 0.8340.5520.8330.833
    75% 0.8500.4640.8510.851
    Table 3 compares the OPD and the SECnet for conventional SSRO for desalination only and the new invention of CDBR to achieve a water product that
    twenty
    image24
    It has a salt concentration of 350 ppm and a boron concentration of 0.5 ppm for total water recoveries of 50%, 65% and 75%. Note that conventional SSRO cannot reduce the concentration of boron to 0.5 ppm for a typical salt water feed that contains 10 ppm of boron using commercially available RO 5 membranes. The invention of CDBR can achieve the same total water recovery as conventional SSRO at a substantially reduced OPD. The invention of CDBR reduces the OPD required for desalination only via SSRO by 10%, 18% and 20% to total water recovery values of 50%, 65% and 75%, respectively. The invention of CDBR results in an increase in SECnet of 8%, 4% and 2% for the total water recovery values of 50%, 65% and 75%, respectively, in relation to the use of conventional SSRO for desalination only. Since the invention of CDBR can desalinate and reduce the concentration of boron to 0.5 ppm at a substantially reduced OPD, it will result in a significant reduction in fixed costs for pumps, pipes and vessels.
    15 pressure in relation to the use of SSRO for desalination only. In addition, lower pressure operation via the CDBR invention will reduce maintenance costs for desalination and boron removal.
    Table 3. Comparison of OPD and SECnet for desalination using SSRO and the invention of CDBR for both desalination and boron removal
    20 producing a water product with a salt concentration equal to or less than 350 ppm and a boron concentration of 0.5 ppm.
    Process 50% recovery65% recovery75% recovery
    OPD (bar) SECnet (kWh / m3) OPD (bar)SECnet (kWh / m3) OPD (bar)SECnet (kWh / m3)
    SSRO 55.52,24279.32,9221113,915
    CDBR 50.22,42064.93,03388.93,990
    The proof of concept for the invention of CDBR has been shown in detail for the realization of four stages which involves sending the retained fraction from a 25-stage SSRO to a 2-stage CMCR and sending the filtering of the SSRO stage to an LPMS after which the filtering streams of CMCR and LPMS are mixed to achieve the desired concentrations of salt and boron. It has been shown that the invention of CDBR
    5
    10
    fifteen
    twenty
    25
    30
    35


    It is capable of producing a water product that has a salt concentration equal to or less than 350 ppm and a specified boron concentration of 0.5 ppm, which meets the WHO recommendations for drinking and irrigation water. It has been shown that the invention of CDBR achieves the specified water product concentrations at substantially lower pressures than those required for desalination alone via conventional SSRO for the same total water recovery. In addition, the invention of CDBR can achieve the specified water product concentrations at a SECnet only slightly higher than for desalination alone via conventional SSRO at moderate recoveries of 50% and almost the same values as conventional SSRO for recoveries of 65% and 75%. Since the invention of CDBR substantially reduces the pressure required for desalination and concurrent boron removal, it will reduce the fixed construction costs associated with pumps, pipes and pressure vessels and reduce maintenance costs associated with continuous high-pressure operation. . These additional cost reductions are not included in the proof of concept analysis.
    The proof of concept for this CDBR invention has been shown based on the maintenance of the same OPD in stages 1, 2 and 3. This embodiment of the EERO invention is advantageous since it avoids any pumping between stages on the high pressure side. of the CMCR. However, another embodiment of this CDBR invention is to allow a reduced OPD in one or more of the stages in the CMCR while at the same time avoiding any pumping between stages on the high pressure side of the CMCR membrane cascade. . This will reduce pumping costs at the expense of reduced recovery of drinking water. For some applications, this embodiment of the CDBR invention may be desirable. The invention of CDBR can also be implemented in two additional embodiments illustrated in Figure 3:
    a) The filtering current of Stage 1 can be divided into two fractions by means of a flow divider, in which one fraction is fed to Stage 4 as in the case of the original invention, while the other fraction circles Stage 4 to mix with the filtering currents leaving Stage 4 and Stage 3. This embodiment is called CDBR-B and introduces a new input parameter, the division ratio (S) that is defined as the ratio of the flow rate of the current that surrounds Stage 4 to the flow rate of the filtering current leaving Stage 1. When S = 0, the original CDBR invention is recovered. Having a flow divider that affects the concentrations in the final product could also be an advantage, since it provides a simple way to compensate for any change in the system elsewhere, such as changes in permeability due to clogging or polarization by concentration, membrane aging, etc.
    image25
    b) The retained fraction of Stage 4 can be totally or partially recycled as feed to Stage 1. This embodiment is called CDBR-BR. Since the salt concentration of the retained fraction of Stage 4 is lower than that of the seawater feed to Stage 1, which could well be, it will dilute the feed and, therefore, should reduce the OPD required in the Stages 1, 2 and 3. Increasing the feed flow to Stage 1 by recycling the retained fraction of Stage 4 would also increase the safety factor (that is, the fraction flow ratio
    10 retained at filtrate flow rate) and would allow Stage 1 to perform a greater recovery.
    The process conditions for the invention of CDBR-B to produce a processed water containing no more than 350 ppm of salt and a specified boron concentration of 0.5 ppm are summarized in Table 4. Produces OPD and SECnet lower than the SSRO for all recoveries.
    15 Table 4. Comparison of OPD and SECnet for desalination using the SSRO and the invention of CDBR-B for both desalination and boron removal that produces a water product with a salt concentration equal to or less than 350 ppm and a boron concentration of 0.5 ppm.
    Recovery Y2Sσ1sσ4sσ1bσ4bOPD (bar)SECnet (kWh / m3)
    fifty% 0.3920.300.9960.9970.8990.90088.73.81
    65% 0.2950.370.9970.9970.9000.90065.02.92
    75% 0,1500.440.9970.9970.9000.90049.82.35
    twenty
    It is also of interest to determine the performance of the proposed invention only for desalination. It would be possible to obtain a water product with 0.350 ppm salt concentration at lower OPD and SECnet values when using the CDBR-BR invention. In Table 5, the performance of the invention of CDBR-BR with a ratio of
    The division of 0.95 and a complete recycling of the retained fraction of Stage 4 is compared with that of the SSRO for desalination for water recoveries of 65% and 75%.
    Table 5. Comparison of OPD and SECnet for desalination using the SSRO and the invention of CDBR-BR that produces a water product with a salt concentration equal to 350 ppm.
    image26
    Process 65% recovery75% recovery
    OPD (bar) SECnet (kWh / m3) OPD (bar)SECnet (kWh / m3)
    SSRO 79.32,9221113,915
    CDBR-BR 61.02,71879.33,387
    In addition, instead of the SSRO stage in the embodiments described in Figures 1,
    5 3a and 3b, two or more SSRO stages can be used, in which the salt water feed is introduced on the high pressure side of the SSRO stage and the retained fraction of each SSRO stage is introduced on the side High pressure of the subsequent SSRO stage while the retained fraction of the last SSRO stage is introduced into the CMCR unit. The filtering of all stages of SSRO is introduced into the LMPS.
    In this embodiment, the OPD can be gradually increased between the first and last SSRO stage, and the last SSRO stage operates at the same OPD as the CMCR unit, which results in a lower SECnet compared to the original embodiment. As an example, in one embodiment of the invention of CDBR with two stages of SSRO, described in Figure 4; for 75% water recovery, the first stage of SSRO
    15 can operate at an OPD of 52.8 bar while the second stage of SSRO and the rest of the CDBR unit operates at an OPD of 100 bar, resulting in a SECnet of 3,117 kWh / m3, while for recovery of 65% water, the first stage of SSRO can operate at an OPD of 43.1 bar while the second stage of SSRO and the rest of the CDBR unit operates at an OPD of 66.8 bar, giving as
    A SECnet of 2,606 kWh / m3 resulted to produce a water product with a salt concentration equal to or less than 350 ppm and a boron concentration of 0.5 ppm.
    权利要求:
    Claims (18)
    [1]
    image 1
    1. A system for the concurrent boron desalination and desalination procedure (CDBR), characterized in that the system combines one or more inverse osmosis modules 5 (RO) connected in series, which is called single stage reverse osmosis (SSRO) , or two or more of these stages of SSRO in series, with a cascade of membranes in countercurrent with recycled (CMCR) that has at least two stages and a low pressure membrane stage (LPMS) where the retained fraction of the stage of SSRO is the power to the CMCR and the filtering of the SSRO stage is the
    10 feed to the LPMS and where the filtration currents of the CMCR and LPMS are mixed to achieve the concentrations of boron and / or salt specified in the processed water.
    [2]
    2. A system according to claim 1, wherein each step in the SSRO, CMCR and LPMS consists of one or more membrane modules connected in parallel.
    3. A system according to claim 1, wherein the system supplies a water product having a salt concentration equal to or less than 350 ppm.
    [4]
    Four. A system according to claim 1, wherein the system supplies a water product having a boron concentration equal to or less than 0.5 ppm.
    [5]
    5. A system according to claim 1, wherein the SSRO stage and the stage of
    20 CMCRs operate at the same osmotic pressure differential (OPD), ignoring small losses due to the pressure drop required for flow through the conduits and the membrane modules or to cause filtration in the membrane modules.
    [6]
    6. A system according to claim 1, wherein the system supplies the removal of
    Desired boron with greater water recovery at a lower OPD and at a reduced specific energy consumption (SEC) with respect to the conventional SSRO for a saline water or an aqueous feed containing solutes of relatively low molecular weight.
    [7]
    7. A system according to claim 1, wherein the system supplies the removal of
    A desired salt with greater water recovery at a lower OPD and at a reduced SEC relative to the conventional SSRO for a saline water or an aqueous feed containing relatively low molecular weight solutes.
    25
    image2
    [8]
    8. A system according to claim 1, characterized in that it comprises one or more CMCR stages, wherein the OPD is reduced in one or more of said CMCR stages relative to the OPD in the SSRO stage.
    [9]
    9. A system according to claim 1, characterized in that it comprises one or more CMCR stages, wherein the OPD is increased in one or more of said CMCR stages relative to the OPD in the SSRO stage.
    [10]
    10. Concurrent procedure for desalination and boron removal (CDBR) for the production of drinking water and irrigation, characterized by comprising the following stages:
    -introduce the retained fraction of an SSRO stage or a series of SSRO stages optimally as feeding to the CMCR;
    - counter current of retained fraction and filtration flow in the CMCR;
    -recycling filtering on the side of the fraction retained in the CMCR;
    - self-recycling of the fraction retained in at least one of the membrane stages in the CMCR;
    -introduce the filtering of the step (s) of the SSRO as feed in an LPMS; Y
    -mix the filtration currents of the CMCR and LPMS to achieve the desired concentrations in the water product.
    [11]
    eleven. A method according to claim 10, wherein the retained fraction of the SSRO stage is the feed to the stage in the CMCR in which its concentration is closer to that of the other currents entering this stage.
    [12]
    12. A method according to claim 10, wherein the salt rejection of the membrane stages in the CMCR decreases in the direction of the product of the retained fraction to allow some filtration of salt or other low molecular weight solutes from the high pressure side at the bottom of the membranes to reduce OPD.
    [13]
    13. A method according to claim 10, wherein the effective rejection at each stage of the CMCR is achieved by decreasing or increasing the pressure of this stage.
    [14]
    14. A method according to claim 10, wherein a portion of the retained fraction of one or more stages is recycled back to the same stage feed to increase recovery.
    [15]
    fifteen. A method according to claim 10, wherein the one-stage safety factor, which is the flow ratio of fraction retained to filtered in the stage, is allowed to be less than one due to the removal of poorly soluble clogging agents in a or more stages that precede this stage in the direction of the flow of the
    26
    image3
    5 fraction retained.
    [16]
    16. A method according to claim 10, wherein the recovery of water in the LPMS is optimized to reduce the specific energy consumption.
    [17]
    17. A process according to claim 10, wherein the concentrations of boron and / or salt can be reduced in seawater or brackish water to produce drinking water and / or
    10 irrigation using conventional RO and NF membranes and high-flow membranes of the latest generation.
    [18]
    18. Use of a system according to claim 1 for the production of drinking water.
    [19]
    19. Use of a system according to claim 1 for the production of irrigation water.
    27
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    同族专利:
    公开号 | 公开日
    ES2672787B1|2019-02-07|
    ES2672787R1|2018-07-11|
    IL257497D0|2018-06-28|
    US20200289986A1|2020-09-17|
    IL257497A|2021-12-01|
    WO2018074984A1|2018-04-26|
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