Concentration System

Abstract

To provide a concentration system which uses brine concentration (BC), and in which appropriate management can be implemented during operation of the concentration system.SOLUTION: A concentration system is provided, comprising a semi-permeable membrane module which has a semi-permeable membrane and a first chamber and a second chamber partitioned by the semi-permeable membrane, wherein the semi-permeable membrane module flows first object liquid to the first chamber at prescribed pressure, and flows second object liquid to the second chamber at pressure lower than the prescribed pressure, accordingly, causes water included in the first object liquid inside the first chamber to transfer to the second object liquid in the second chamber via the semi-permeable membrane, and discharges concentrated liquid from the first chamber, and discharges diluted liquid from the second chamber. The concentration system further comprises a monitoring device monitoring at least one parameter related to the operation of the concentration system.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a concentration system. [Background technology]

[0002] For example, with the aim of reducing the energy required for desalination treatment using reverse osmosis (RO), a membrane separation method (brine concentration) has been considered in which a high-pressure target liquid is passed through a first chamber of a semipermeable membrane module, a low-pressure target liquid is passed through a second chamber, and water contained in the target liquid in the first chamber is transferred through the semipermeable membrane to the target liquid in the second chamber, thereby discharging a concentrated target liquid from the first chamber and a diluted target liquid from the second chamber (see, for example, Patent Document 1: JP 2018-1110 A). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-1110 A Summary of the Invention [Problem to be solved by the invention]

[0004] In semipermeable membrane modules used in brine concentration (BC), impurities such as turbidity (e.g., fine particles, microorganisms, scale components) adhere to the surface of the semipermeable membrane over time depending on the membrane separation processing volume of the target liquid, causing problems such as a decrease in separation performance (filtration efficiency). For this reason, it is desirable to wash the semipermeable membrane of the semipermeable membrane module at an appropriate frequency and for an appropriate time depending on the degree of impurity adhesion.

[0005] In addition, the water permeability of the semipermeable membrane changes depending on parameters such as concentration (osmotic pressure), temperature, and pH. Such changes in water permeability may increase the adhesion of impurities, such as scale precipitation, to the semipermeable membrane. For example, if the water permeability becomes larger than expected, the increase in permeated water may increase the concentration rate, making it easier for scale precipitation to occur. For this reason, it is desirable to carry out process management taking the above parameters into consideration.

[0006] Thus, when operating an enrichment system using BC, it is desirable to carry out appropriate management according to various factors.

[0007] Therefore, an object of the present invention is to provide a concentration system using brine concentration (BC) that can perform appropriate management during operation of the concentration system. [Means for solving the problem]

[0008] (1) A concentration system including a semipermeable membrane module, the system having a first chamber and a second chamber separated by the semipermeable membrane, the system causing a first target liquid to flow through the first chamber at a predetermined pressure and a second target liquid to flow through the second chamber at a pressure lower than the predetermined pressure, thereby transferring water contained in the first target liquid in the first chamber through the semipermeable membrane to the second target liquid in the second chamber, discharging a concentrated liquid from the first chamber, and discharging a diluted liquid from the second chamber, the system comprising: The concentration system further comprises a monitoring device that monitors at least one parameter related to the operation of the concentration system.

[0009] (2) The concentration system according to (1), comprising a plurality of the semipermeable membrane modules.

[0010] (3) The concentration system according to (1) or (2), wherein the parameters include a flow rate and a pressure of at least one of the first target liquid and the second target liquid in the semipermeable membrane module.

[0011] (4) The concentration system described in any one of (1) to (3), further comprising a control mechanism that controls operation of the concentration system based on the at least one parameter monitored by the monitoring device.

[0012] (5) A reverse osmosis module is further provided, which separates and recovers water from the raw liquid pressurized to a predetermined pressure through a reverse osmosis membrane, and discharges a concentrated raw liquid, which is the concentrated raw liquid; The concentration system according to any one of (1) to (4), wherein the concentrated stock solution is caused to flow as the first target liquid into the first chamber at a predetermined pressure. Effect of the Invention

[0013] In the present invention, a concentration system using brine concentration (BC) can be provided, which can perform appropriate management during operation of the concentration system by monitoring various parameters in the concentration system. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a concentration system of the first embodiment. [Diagram 2] FIG. 1 is a schematic diagram showing a concentration system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals represent the same or corresponding parts. In addition, the dimensional relationships of the length, width, thickness, depth, etc. have been appropriately changed for the purpose of clarifying and simplifying the drawings, and do not represent the actual dimensional relationships.

[0016] <Embodiment 1> With reference to FIG. 1, the concentration system of this embodiment includes a semipermeable membrane module 1 and a monitoring device 3. The semipermeable membrane module 1 has a semipermeable membrane 10 and a first chamber 11 and a second chamber 12 separated by the semipermeable membrane, and by flowing a concentrated undiluted liquid as a first target liquid into the first chamber 11 at a predetermined pressure and flowing a second target liquid into the second chamber 12 at a pressure lower than a predetermined pressure (the pressure of the first liquid), water contained in the first target liquid in the first chamber 11 is transferred to the second target liquid in the second chamber 12 via the semipermeable membrane, and the concentrated liquid is discharged from the first chamber 11 and the diluted liquid is discharged from the second chamber 12. The monitoring device 3 monitors at least one parameter related to the operation of the concentration system.

[0017] [Semipermeable membrane module] The multiple semipermeable membrane modules 1 each have a semipermeable membrane 10 and a first chamber 11 and a second chamber 12 separated by the semipermeable membrane 10 .

[0018] The number of semipermeable membrane modules 1 is not particularly limited. However, when the concentration system includes a plurality of semipermeable membrane modules 1 as shown in FIG. 1, the fluid flowing between the modules flows at high pressure, and because of this, the number of flow paths that can be opened is small, making sampling and the like difficult. Therefore, it is particularly effective to install sensors in advance in each flow path and monitor various parameters obtained from the sensors to perform process control.

[0019] The first target liquid flows into the first chamber 11 at a predetermined pressure, and the second target liquid flows into the second chamber 12 at a pressure lower than the predetermined pressure. As a result, water contained in the first target liquid in the first chamber 11 transfers to the second target liquid in the second chamber 12 through the semipermeable membrane 10, and the concentrated liquid (concentrated first target liquid) is discharged from the first chamber 11, and the diluted liquid (diluted second target liquid) is discharged from the second chamber 12.

[0020] The first target liquid and the second target liquid may be the same liquid. For example, as shown in Fig. 1, a part of the first target liquid having a predetermined pressure may be passed through a pressure reducing device 4 to flow into the second chamber at a pressure lower than the predetermined pressure.

[0021] Examples of the pressure reducing device 4 include a dividing valve, a pressure reducer, or an energy recovery device that can divide the first target liquid having a predetermined pressure into a flow path to the second chamber 12 of the semipermeable membrane module and another flow path. Here, the pressure reducing device 4 (dividing valve) has a function of reducing the pressure of the target liquid to be flowed into the second chamber 12 to a pressure lower than a predetermined pressure. Note that the use of such a pressure reducing device has the advantage that only one flow path for the target liquid on the upstream side of the semipermeable membrane module is required, for example.

[0022] 1, the target liquid flowing into the first chamber 11 and the second chamber 12 of the semipermeable membrane module (each of the semipermeable membrane modules 1) is the same liquid, and therefore has essentially the same osmotic pressure. For this reason, unlike the RO method, high pressure is not required to cause reverse osmosis against the high osmotic pressure difference between the target liquid (high osmotic pressure liquid) and fresh water, and membrane separation of the target liquid can be performed by applying a relatively low pressure (a portion of the target liquid can be diluted and another portion of the target liquid can be concentrated).

[0023] However, in this embodiment, the second target liquid supplied to the second chamber 12 of the semipermeable membrane module may be a liquid independent of the first target liquid supplied to the first chamber 11.

[0024] Even if the first target liquid flowing into the first chamber 11 and the second target liquid flowing into the second chamber 12 are different liquids and have different concentrations, membrane separation by BC is theoretically possible as long as the osmotic pressure difference (absolute value) is smaller than the pressure of the first target liquid supplied to the first chamber 11. In this case, it is preferable that the difference between the osmotic pressure of the first target liquid flowing into the first chamber 11 (high pressure side) and the osmotic pressure of the second target liquid supplied to the second chamber 12 (low pressure side) is 30% or less of the predetermined pressure of the first target liquid supplied to the first chamber 11.

[0025] In addition, the BC process using the semipermeable membrane module 1 is preferably a multi-stage process using a plurality of semipermeable membrane modules (connected in series) as shown in FIG. 1, but may also be a single-stage process using one semipermeable membrane module.

[0026] In the brine concentration (BC) which is a membrane separation process in a semipermeable membrane module, in order to transfer water from the first chamber 11 to the second chamber 12 through the semipermeable membrane 10 of the semipermeable membrane module, the pressure of the first target liquid supplied to the first chamber 11 needs to be greater than the osmotic pressure difference between the first target liquid and the second target liquid flowing on both sides of the semipermeable membrane 10. For this reason, in order to highly concentrate the first target liquid in a single step (one semipermeable membrane module), it is necessary to supply it at a correspondingly high pressure, which has the disadvantage of increasing the energy cost for operating the pump. For this reason, BC may be performed by a multi-step process using multiple semipermeable membrane modules in order to perform the concentration step in stages and reduce the pressure required for BC. Such BC by a multi-step process is disclosed, for example, in JP 2018-069198 A.

[0027] Examples of the semipermeable membrane include semipermeable membranes called reverse osmosis (RO) membranes, forward osmosis (FO) membranes, and nanofiltration (NF) membranes. When a reverse osmosis membrane, forward osmosis membrane, or nanofiltration membrane is used as the semipermeable membrane, the pressure of the first object liquid supplied to the first chamber 11 is preferably 6 to 10 MPa.

[0028] Typically, the pore size of RO and FO membranes is about 2 nm or less, and the pore size of UF membranes is about 2 to 100 nm. Among RO membranes, NF membranes have a relatively low rejection rate for ions and salts, and typically, the pore size of NF membranes is about 1 to 2 nm. When an RO membrane, FO membrane, or NF membrane is used as the semipermeable membrane, the salt rejection rate of the RO membrane, FO membrane, or NF membrane is preferably 90% or more.

[0029] The material constituting the semipermeable membrane is not particularly limited, but examples thereof include cellulose-based resins, polysulfone-based resins, polyamide-based resins, etc. The semipermeable membrane is preferably composed of a material containing at least one of a cellulose-based resin and a polysulfone-based resin.

[0030] The cellulose-based resin is preferably a cellulose acetate-based resin. The cellulose acetate-based resin has a characteristic of being resistant to chlorine, which is a bactericide, and capable of suppressing the growth of microorganisms. The cellulose acetate-based resin is preferably cellulose acetate, and from the viewpoint of durability, more preferably cellulose triacetate.

[0031] The polysulfone-based resin is preferably a polyethersulfone-based resin.The polyethersulfone-based resin is preferably a sulfonated polyethersulfone.

[0032] The shape of the semipermeable membrane 10 (and the above-mentioned reverse osmosis membrane 20) is not particularly limited, but examples thereof include a flat membrane and a hollow fiber membrane. Although FIG. 1 shows a simplified flat membrane as the semipermeable membrane 10, the shape is not particularly limited to this. A hollow fiber membrane (hollow fiber type semipermeable membrane) is advantageous in that it can increase the membrane area per module compared to a spiral type semipermeable membrane and the like, thereby increasing the permeation efficiency.

[0033] The form of the semipermeable membrane module (and the above-mentioned reverse osmosis module 2) is not particularly limited, but when hollow fiber membranes are used, examples include a module in which the hollow fiber membranes are arranged in a straight line, a cross-wound type module in which the hollow fiber membranes are wound around a core tube, etc. When flat membranes are used, examples include a laminated type module in which flat membranes are stacked, and a spiral type module in which flat membranes are wrapped around a core tube in an envelope shape.

[0034] A specific example of the hollow fiber membrane is a membrane with a single layer structure entirely made of a cellulose-based resin. However, the single layer structure does not necessarily have to be a uniform membrane throughout, and it is preferable that the membrane has a dense layer near the outer peripheral surface, and that this dense layer is a separation active layer that substantially determines the pore size of the hollow fiber membrane, as disclosed in JP 2012-115835 A.

[0035] Another specific example of the hollow fiber membrane is a two-layer membrane having a dense layer of polyphenylene resin (e.g., sulfonated polyethersulfone) on the outer peripheral surface of a support layer (e.g., a layer made of polyphenylene oxide). Another example is a two-layer membrane having a dense layer of polyamide resin on the outer peripheral surface of a support layer (e.g., a layer made of polysulfone or polyethersulfone).

[0036] In a semipermeable membrane module using hollow fiber membranes, the outside of the hollow fiber membrane is usually the first chamber. This is because even if the fluid flowing inside the hollow fiber membrane (hollow portion) is pressurized, the pressure loss becomes large and the pressurization does not work sufficiently.

[0037] [Monitoring device] The monitoring device 3 monitors at least one parameter related to the operation of the concentration system.

[0038] The monitoring device 3 is configured, for example, to be able to acquire information on various parameters (measured values) acquired by at least one sensor 5. For example, the monitoring device 3 is able to communicate with the sensor 5 via wired communication or wireless communication.

[0039] The sensor 5 is provided, for example, in a flow path that constitutes the concentration system. The sensor 5 is preferably installed in the flow path on the inlet side and / or the outlet side of at least the first chamber 11 and / or the second chamber 12 of the semipermeable membrane module 1 used in BC.

[0040] Parameters to be monitored include, for example, flow rate, pressure, differential pressure, temperature, TDS (total dissolved solids), electrical conductivity, TOC (total organic carbon), COD (chemical oxygen demand), BOD (biochemical oxygen demand), SS (suspended solids), DO (dissolved oxygen), residual chlorine concentration, ORP (oxidation-reduction potential), pH, hardness, alkalinity, etc. Examples of the sensor 5 include measuring devices for these parameters.

[0041] The parameters preferably include the flow rate and pressure of at least one of the first target liquid and the second target liquid in the semipermeable membrane module 1. The flow rate and pressure of the first target liquid are preferably the flow rate and pressure of the inlet side (inlet) and the outlet side (outlet) of the first chamber 11. The flow rate of the second target liquid is preferably the flow rate and pressure of the inlet side (inlet) and the outlet side (outlet) of the second chamber 12.

[0042] The monitoring device 3, for example, periodically or continuously acquires parameters (measured values) obtained by these sensors 5 (measuring instruments).

[0043] By monitoring various parameters in the concentration system using the monitoring device 3, appropriate management can be performed during operation of the concentration system using brine concentration (BC).

[0044] By monitoring various parameters in the concentration system, it becomes possible to efficiently carry out processes such as cleaning and sterilization, to determine or predict problems, and to respond to problems promptly, thereby enabling the concentration system to be operated stably.

[0045] <Embodiment 2> Referring to FIG. 2, the concentration system of this embodiment further includes a control mechanism 6.

[0046] [Control Mechanism] The control mechanism 6 controls the operation of the concentration system based on the at least one parameter monitored by the monitoring device 3. The control mechanism 6 preferably controls, for example, the flow rate and pressure of at least one of the first target liquid and the second target liquid in the semipermeable membrane module 1.

[0047] The control performed by the control mechanism 6 includes, for example, feedback control, trouble detection, and the like.

[0048] An example of feedback control is a control unit that uses physical quantities (parameters) within the concentration system to calculate the optimal drive frequency of a pump (pump 1a, high-pressure pump 2a, etc.) so that the flow rate of the permeate reaches a preset target flow rate value, and outputs a value signal to the pump inverter to control the drive frequency of the pump.

[0049] Also, for example, the flow rates, pressures, etc. of the first and second target liquids may be controlled to adjust the concentration ratio, i.e., the flow rate of the permeated water ([flow rate at the inlet of the first chamber 11]-[flow rate at the outlet of the first chamber 11]), so that the scale components (calcium bicarbonate, etc.) do not exceed an allowable concentration in the first target liquid concentrated in the first chamber 11 of the semipermeable membrane module 1. The allowable concentration of the scale components in the first target liquid (the maximum concentration within the range in which scale such as calcium carbonate does not precipitate) can be calculated based on, for example, parameter information such as the pH, hardness, alkalinity, and temperature of the first target liquid, the solubility of scale (calcium carbonate, etc.), and various scale precipitation determination equations.

[0050] An example of the detection of a problem is a control that issues a warning when a sudden change in a parameter due to damage to the semipermeable membrane module 1 and the RO module 2, such as a break in the semipermeable membrane 10 and the RO membrane 20, is detected. Another example is the control of the frequency, time, degree, etc. of cleaning based on a parameter that is an index of the degree of contamination of the semipermeable membrane of the semipermeable membrane module.

[0051] [RO+BC] As a concentration system using BC, as shown in Figure 2, a concentration system is being considered in which the concentrated raw liquid discharged from a reverse osmosis (RO) module 2 is passed through the first chamber of a semipermeable membrane module that can be operated at even higher pressure, and the concentrated raw liquid is further concentrated by the above-mentioned brine concentration (BC) under ultra-high pressure conditions higher than those of the RO method.

[0052] The reverse osmosis module 2 separates and recovers water from the raw liquid pressurized to a predetermined pressure via the reverse osmosis membrane 20, and discharges a concentrated raw liquid, which is the concentrated raw liquid.

[0053] 2, a high-pressure pump 2a is provided upstream of a reverse osmosis (RO) module 2. The high-pressure pump 2a pressurizes the raw liquid to a predetermined pressure and supplies it to a first chamber 21 of the RO module 2. The RO module 2 separates water (permeate) from the raw liquid pressurized to the predetermined pressure via a reverse osmosis (RO) membrane 20 and sends it to a second chamber 22, thereby discharging the concentrated raw liquid, which is the concentrated raw liquid, from the first chamber 21 and discharging water from the second chamber 22.

[0054] In this specification, the "raw liquid" is not particularly limited as long as it is a liquid containing water to be supplied to the RO module 2, and may be either a solution or a suspension. Examples of the raw liquid include seawater, river water, brackish water, and wastewater. Examples of the wastewater include industrial wastewater, domestic wastewater, and wastewater from oil or gas fields.

[0055] In addition, a pretreatment device (not shown) may be provided upstream of the high-pressure pump 2a to remove turbid matter (fine particles, microorganisms, scale components, etc.) contained in the raw liquid. Examples of the pretreatment device include a sand filter, a filtration device using a UF (Ultrafiltration) membrane, an MF (Microfiltration) membrane, etc., an addition device for chlorine, sodium hypochlorite, a coagulant, a scale inhibitor, etc., and a pH adjustment device. The scale inhibitor is an additive that has the effect of preventing or suppressing the precipitation of scale components in the liquid as scale. Examples of the scale inhibitor include polyphosphoric acid-based, phosphonic acid-based, phosphinic acid-based, polycarboxylic acid-based compounds, etc.

[0056] In this embodiment, the semipermeable membrane module 1 is connected downstream of the RO module 2 (first chamber 21). The first target liquid supplied to the first chamber 11 of the semipermeable membrane module (each of the semipermeable membrane modules 1) is the concentrated stock solution discharged from the first chamber 21 of the RO module 2. The concentrated stock solution discharged from the RO module 2 has a high pressure and is therefore sent to the semipermeable membrane module side by that pressure.

[0057] In a concentration system that combines the RO and BC processes as shown in Figure 2, concentration is performed at a high concentration rate, which means that impurities such as scale deposition are likely to adhere to the surface of the semipermeable membrane. Therefore, it is particularly effective to monitor various parameters and perform process control.

[0058] In this embodiment, the concentration system may further include an energy recovery device 7. When the energy recovery device 7 is installed as shown in Fig. 2, the pressure energy of the liquid (concentrated first target liquid) discharged from the first chamber 11 of the semipermeable membrane module 1 is recovered and applied to the raw liquid supplied to the RO module 2, thereby reducing the energy required for the high-pressure pump 2a.

[0059] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0060] 1 Semipermeable membrane module, 1a pump, 10 Semipermeable membrane, 11 First chamber, 12 Second chamber, 2 Reverse osmosis (RO) module, 2a High pressure pump, 20 Reverse osmosis (RO) membrane, 21 First chamber, 22 Second chamber, 3 Monitoring device, 4 Pressure drop device, 5 Sensor, 6 Control mechanism, 7 Energy recovery device.

Claims

1. A concentration system including a semipermeable membrane module, the semipermeable membrane module having a first chamber and a second chamber separated by the semipermeable membrane, the semipermeable membrane module causing a first target liquid to flow through the first chamber at a predetermined pressure and a second target liquid to flow through the second chamber at a pressure lower than the predetermined pressure, thereby transferring water contained in the first target liquid in the first chamber through the semipermeable membrane to the second target liquid in the second chamber, discharging a concentrated liquid from the first chamber, and discharging a diluted liquid from the second chamber, The apparatus further includes a reverse osmosis module that separates and recovers water from the stock solution pressurized to a predetermined pressure through a reverse osmosis membrane, and discharges a concentrated stock solution, which is the concentrated stock solution; The concentrated stock solution is flowed as the first target liquid into the first chamber at a predetermined pressure, a monitoring device for monitoring at least one parameter related to the operation of the concentration system; a control mechanism for controlling operation of the concentration system based on the at least one parameter monitored by the monitoring device; The parameter is at least one of a temperature, a pH, a hardness, and an alkalinity of at least one of the first target liquid and the second target liquid in the semipermeable membrane module; The control mechanism controls the flow rates and pressures of the first target liquid and the second target liquid so that the concentration of scale components does not exceed an allowable concentration, which is the maximum concentration in the range in which scale does not precipitate.

2. The concentration system according to claim 1 , comprising a plurality of said semipermeable membrane modules.

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