JP2011147894A - Seawater desalination apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seawater desalination apparatus capable of economically obtaining treated water having boron concentration not more than a reference value by adequately regulating the water temperature. <P>SOLUTION: The seawater desalination apparatus carrying out a filtration treatment using a reverse osmosis membrane includes a water temperature regulator 12 disposed on the upper stream side of the reverse osmosis membrane for changing the seawater temperature, a boron concentration measuring means 20 for measuring the boron concentration of the treated water after the filtration, and a controller 24 for operating the water temperature regulator by determining the operation amount thereof on the basis of the boron concentration of the treated water and the target boron concentration given in advance. Alternatively, the seawater desalination apparatus includes a treated water boron concentration forecasting means 40 for calculating the anticipated boron concentration of the treated water after the filtration from the boron concentration of the seawater, and a controller for operating the water temperature regulator by determining the operation amount thereof on the basis of the anticipated boron concentration of the treated water and the target boron concentration given in advance. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a seawater desalination apparatus using a reverse osmosis membrane for obtaining fresh water from seawater, in particular, a seawater desalination apparatus in which the concentration of boron in treated water obtained as a result of seawater desalination satisfies a reference value. About.

  In recent years, seawater desalination apparatuses using a filtration process using a reverse osmosis membrane tend to increase. The reverse osmosis membrane is made of a material such as cellulose or polyamide, and fresh water with suppressed permeation of salt can be obtained by applying a pressure of at least twice the osmotic pressure of seawater to the membrane. This pressure reaches from 50 MPa to 80 MPa in some cases, which increases the power cost of the high-pressure pump.

  Moreover, since the boron concentration contained in seawater is 4.5 to 5 mg / L, the water quality standard value of WHO drinking water is 0.5 mg / L, so the necessary boron rejection is about 90%. However, the blocking rate of boron in one general reverse osmosis membrane module is 50 to 70%, which requires two-step treatment of high pressure reverse osmosis membrane and low pressure reverse osmosis membrane, increasing initial cost and running cost To do. In order to reduce running costs as much as possible, there are two systems for producing one-stage treated water and two-stage treated water, and two-stage treated water and two-stage treated water are used so that the boron concentration in the treated water is slightly lower than the reference value. Although blending staged water has been practiced, the feasible scope of such a method is limited.

  In order to reduce the power cost of a high-pressure pump, for example, Patent Document 1 discloses a reverse osmosis membrane seawater freshwater that heats seawater using heat generated by waste incineration as a heat source and supplies the seawater to a seawater desalination apparatus to obtain freshwater. An apparatus is disclosed. Here, since the viscosity resistance of water changes with temperature, the amount of fresh water increases by 3% each time the temperature of the supplied seawater is increased by 1 ° C, so the operation with a high recovery rate and the number of reverse osmosis membrane modules are reduced. Further, it is described that highly efficient operation can be achieved economically without newly consuming fuel.

  Patent Document 2 is based on a filtration device that uses a reverse osmosis membrane, a temperature adjustment unit that adjusts the temperature of raw water, a measurement unit that measures the concentration of treated water obtained by the filtration device, and a measured concentration. Disclosed is a desalting process including a control unit that controls the temperature adjustment unit. However, here, the measurement unit is a conductivity meter that measures the salt concentration (ion concentration) of the treated water, and does not focus on the boron concentration.

  Patent Document 3 discloses a membrane pretreatment device comprising a hollow fiber membrane, a first pH adjusting device, a decarbonation gas tower, a second pH adjusting device, a first reverse osmosis membrane device, a second reverse osmosis membrane device, Disclosed is an ultrapure water production apparatus comprising a flat plate heat exchanger and a mixed bed ion exchange apparatus. And here, it is described that the temperature of the water to be treated is controlled to 20 ° C. or less, but the water to be treated that is passed through the mixed bed ion exchange device is the target, and the mixed bed ion exchange It is an invention that requires the use of a device.

  Patent Document 4 discloses a fresh water producing apparatus that removes boron contained in seawater using a reverse osmosis membrane (semi-permeable membrane). However, here, pretreatment such as a filter for pretreatment of raw water (seawater), a first semipermeable membrane unit for treating pretreatment water, an intermediate water tank for temporarily storing primary permeate, and intermediate water A second semipermeable membrane unit for treating the primary permeated water stored in the tank, a high-pressure pump provided in the previous stage of the first semipermeable membrane unit, and provided in the previous stage of the second semipermeable membrane unit. In addition to the booster pump, the first alkali addition means provided in the previous stage of the high pressure pump, the second alkali addition means for increasing the pH of the primary permeate in the intermediate water tank, and the secondary permeate a fresh water producing apparatus comprising an acid addition means for lowering the pH. In short, by utilizing the fact that the removal rate of components such as boron varies depending on the pH, the fresh water is efficiently produced by controlling the pH. Is.

Japanese Patent Laid-Open No. 9-085059 JP-A-2005-144301 JP 2005-177564 A JP 2006-187719 A

  In the technique of Patent Document 1, since the boron rejection rate of the reverse osmosis membrane decreases as the water temperature increases, it is necessary to treat all the water in two stages. The operating cost of the osmotic membrane is increased, and further, the boron concentration may still exceed the reference value even after the two-stage treatment.

  In addition, the techniques of Patent Documents 2 to 4 are required to improve economic efficiency such as a complicated apparatus and a high running cost.

  The objective of this invention is providing the seawater desalination apparatus which solves the subject of the prior art mentioned above, and can obtain the treated water of the boron concentration which does not exceed a reference value economically by adjusting water temperature appropriately. .

  In order to achieve the above object, the seawater desalination apparatus of the present invention is a seawater desalination apparatus using a filtration process using a reverse osmosis membrane, and is arranged on the upstream side of the reverse osmosis membrane to adjust the water temperature of the seawater. The operation amount of the water temperature adjusting device is determined based on the apparatus, the boron concentration measuring means for measuring the boron concentration of the treated water after the filtration treatment, the boron concentration information of the treated water and the target boron concentration information given in advance And a control device which operates.

  Further, the seawater desalination apparatus of the present invention is a seawater desalination apparatus using filtration treatment with a reverse osmosis membrane, a water temperature adjusting device arranged upstream of the reverse osmosis membrane to change the temperature of seawater, and boron of seawater Boron concentration measuring means for measuring the concentration, treated water boron concentration predicting means for calculating the boron concentration prediction information of the treated water after the filtration treatment from the boron concentration of the seawater, boron concentration prediction information of the treated water, and given in advance And a control device that operates by determining the operation amount of the water temperature adjusting device based on the obtained target boron concentration information.

  According to the present invention, since the boron concentration contained in the treated water of the seawater desalination apparatus can be suppressed to a reference value or less, it is possible to supply water having no problem even if it is drunk and to ensure high safety. Furthermore, since the operation cost can be minimized while satisfying the water quality standard value, it is economically advantageous.

It is a schematic diagram which shows the structure of the seawater desalination apparatus of Example 1 of this invention. It is a schematic diagram which shows the relationship between the water temperature about a general high-pressure reverse osmosis membrane, and a boron rejection. It is a schematic diagram which shows the structure of the seawater desalination apparatus of Example 2 of this invention. It is a schematic diagram which shows the structure of the seawater desalination apparatus of Example 3 of this invention. It is a schematic diagram which shows the structure of the seawater desalination apparatus of Example 4 of this invention. It is a schematic diagram which shows the structure of the seawater desalination apparatus of Example 5 of this invention.

  Examples of embodiments of the present invention will be described below. In addition, the same code | symbol has shown the structural block which has the fundamentally same or equivalent function in each apparatus through each figure which shows each Example.

[Example 1]
FIG. 1: shows the structure of the seawater desalination apparatus of Example 1 of this invention with a block diagram. The water temperature of the seawater 10 is adjusted by a water temperature adjusting device 12 to become water temperature adjusted seawater 14. Although not shown in FIG. 1, when the pretreatment is provided in the previous stage of the reverse osmosis membrane filtration process 16, the water temperature adjusting device 12 may be in the former stage or the latter stage of the pretreatment. When this pretreatment is, for example, UF membrane filtration and the seawater 10 is heated, a water temperature adjusting device 12 may be provided at the front stage of the UF membrane filtration in order to reduce pump power for the UF membrane filtration. preferable.

  The water temperature-adjusted seawater 14 is desalted by reverse osmosis membrane filtration 16 to become treated water 18. The boron concentration contained in the treated water 18 is measured by the treated water boron concentration measuring means 20 and output as a treated water boron concentration measured value 22. The treated water boron concentration measurement value 22 is given to the control device 24 together with the target boron concentration information 36. The control device 24 outputs a water temperature adjusting device operation signal 26 to the water temperature adjusting device 12 based on the target boron concentration information 36 and the treated water boron concentration measured value 22.

  The water temperature adjustment device 12 changes the water temperature adjustment amount of the seawater 10 according to the water temperature adjustment device operation signal 26. Here, the water temperature adjusting device may have only one of the heating function and the cooling function, but may have both. In order to adjust the water temperature, when a power generation facility is additionally provided, the exhaust heat or steam may be used. Natural energy such as solar heat may be used for heating or cooling.

  Moreover, since the water temperature of seawater changes with water depths, you may make it heat using the seawater near the water surface rather than the seawater which carries out reverse osmosis membrane filtration, or you may make it cool using deeper water. In addition, when using seawater with different water temperatures, they may be mixed, but seawater near the water surface may be contaminated by organic matter or oil spills. Since there is a possibility that there are many silica components that are one of the components of the scale adhering to the water, it is preferable to avoid these mixing and indirectly exchange heat with seawater to be subjected to reverse osmosis membrane filtration with a heat exchanger.

  In addition, if there is both a seawater desalination device A that treats deep seawater and a seawater desalination device B that treats seawater taken from a general water depth (about 10-20m), the seawater desalination device The temperature of the seawater taken by the seawater desalination apparatus B may be adjusted by effectively using the cold heat of the concentrated water after treatment. The reverse osmosis membrane filtration treatment 16 may be a treatment using only a high-pressure reverse osmosis membrane, a treatment comprising a low-pressure reverse osmosis membrane downstream of the high-pressure reverse osmosis membrane, or treatment comprising both of these systems. .

  The operation of the device having the above configuration will be described below. When the boron concentration in seawater is 5 mg / L, a boron rejection rate of 90% or more is required to satisfy the water quality standard value of 0.5 mg / L for WHO drinking water. Currently, there exists a reverse osmosis membrane of high boron rejection type with a boron rejection rate exceeding 90% at a water temperature of 25 ° C. If this rejection rate falls below 90%, the water quality standard will be exceeded, and conversely if it exceeds 90%, the water quality standard will be exceeded.

  FIG. 2 shows the relationship between water temperature and boron rejection for a general high-pressure reverse osmosis membrane. As shown in FIG. 2, the boron rejection rate decreases as the water temperature increases, and the boron rejection rate increases as the water temperature decreases. This relationship is considered to be the same not only in a general high-pressure reverse osmosis membrane but also in a boron high-blocking reverse osmosis membrane.

  For example, in the case of a membrane with a rejection rate of 90% at a water temperature of 25 ° C, the rejection rate may decrease to about 80% when the water temperature reaches 35 ° C. It reaches 1mg / L and greatly exceeds the WHO standard. Conversely, when the water temperature drops to 15 ° C, the rejection rate is improved, and the rejection rate is expected to approach 100%. Actually, since the temperature of seawater fluctuates in summer and winter, the quality of treated water obtained also fluctuates.

  In the present invention, it is possible to reduce the fluctuation of the treated water quality. That is, the boron concentration of treated water is measured, and when the measured value exceeds the reference value or exceeds the voluntary reference value, the water temperature is lowered by the water temperature adjusting device to improve the boron removal rate. It is desirable to set the amount of decrease in the water temperature within a range where the scale component does not precipitate. Conversely, when the boron concentration of the treated water is significantly lower than the standard value or voluntary standard value, the water temperature is raised with a water temperature adjustment device using exhaust heat, etc., and the high pressure filtration used in the reverse osmosis membrane filtration treatment 16 Reduce the power of the pump power. The amount of increase in the water temperature is preferably set within a range that does not damage the material of the film and that does not cause the scale component to precipitate. In seawater, the boron concentration also fluctuates due to fluctuations in water temperature, but stable water temperature adjustment control that can cope with disturbances can be realized using the feedback control described above.

  According to the first embodiment, it is possible to realize an operation in which the concentration of boron contained in the treated water does not exceed the water quality standard value or the voluntary standard value. Moreover, the operation | movement which reduces the motive power of the high pressure filtration pump used by the reverse osmosis membrane filtration process 16 can be implement | achieved, making the boron density | concentration contained in a treated water not exceed water quality reference value or a voluntary reference value. As a result, it is possible to supply safe treated water, and it is possible to reduce operating costs and environmental loads.

[Example 2]
FIG. 3 is a block diagram showing the configuration of the seawater desalination apparatus according to the second embodiment of the present invention. The boron concentration contained in the seawater 10 is measured by the seawater boron concentration measuring means 38, and is output as a seawater boron concentration measurement value 44 therefrom. Then, the seawater 10 is adjusted to a water temperature by a water temperature adjusting device 12 to become a water temperature adjusted seawater 14. The water temperature-adjusted seawater 14 is desalted by reverse osmosis membrane filtration 16 to become treated water 18. The seawater boron concentration measuring means 38 may be installed after the water temperature adjusting device 12 and before the reverse osmosis membrane filtration process 16.

  The seawater boron concentration measurement value 44 is given to the treated water boron concentration prediction means 40. The treated water boron concentration predicting means 40 predicts and calculates the boron concentration in the treated water treated in the reverse osmosis membrane filtration treatment 16 based on past performance data or a physical model. The treated water boron concentration predicted value information 42, which is the output of this calculation, is given to the control device 24 together with the target boron concentration information 36.

  The control device 24 outputs a water temperature adjusting device operation signal 26 to the water temperature adjusting device 12 based on the target boron concentration information 36 and the treated water boron concentration predicted value information 42.

  The water temperature adjustment device 12 changes the water temperature adjustment amount of the seawater 10 according to the water temperature adjustment device operation signal 26. Here, the water temperature adjusting device 12 may have only one of the heating function and the cooling function, or may have both. The reverse osmosis membrane filtration process 16 can be a system using only a high-pressure reverse osmosis membrane, a system including a low-pressure reverse osmosis membrane after the high-pressure reverse osmosis membrane, or a process including both of these systems. Good.

  According to the second embodiment, as in the first embodiment, the water temperature adjusting device 12 is controlled so that the boron concentration of the treated water does not exceed the water quality reference value, the voluntary reference value, or the target boron concentration and does not greatly decrease. As a result, fresh water can be obtained more safely and at low cost. While the first embodiment is feedback control, the second embodiment is characterized in that the water temperature adjusting device 12 is controlled in a feed-forward manner. Therefore, in the second embodiment, the concentration of boron contained in the seawater 10 is particularly high. There is an advantage that a rapid change can be dealt with quickly so as to suppress the influence as much as possible.

  Note that the feedforward control of the water temperature adjustment described above may be combined with feedback control.

[Example 3]
FIG. 4 is a block diagram showing the configuration of the seawater desalination apparatus according to Embodiment 3 of the present invention. The water temperature of the seawater 10 is adjusted by a water temperature adjusting device 12 to become water temperature adjusted seawater 14. The water temperature-adjusted seawater 14 is desalted by reverse osmosis membrane filtration 16 to become treated water 18. The boron concentration contained in the treated water 18 is measured by the treated water boron concentration measuring means 20 and output as a treated water boron concentration measured value 22.

  The filtration pump power cost calculating means 28 calculates the power cost of the filtration pump determined by the water temperature and the operation history. As an input to the filtration pump power cost calculating means 28, it is preferable that information on the water temperature in the reverse osmosis membrane filtration process 16 is always given online. Moreover, as the information of the film differential pressure that changes depending on the operation history, either actual data or a physical model may be used.

  The filtration pump power cost information 30 is given to the control device 24 together with the treated water boron concentration measurement value 22 and the target boron concentration information 36. The control device 24 outputs a water temperature adjustment device operation signal 26 to the water temperature adjustment device 12 based on the target boron concentration information 36, the treated water boron concentration measurement value 22, and the filtration pump power cost information 30.

  The water temperature adjustment device 12 changes the water temperature adjustment amount of the seawater 10 according to the water temperature adjustment device operation signal 26. Here, the water temperature adjusting device may have only one of the heating function and the cooling function, or may have both. The reverse osmosis membrane filtration process 16 can be a system using only a high-pressure reverse osmosis membrane, a system including a low-pressure reverse osmosis membrane after the high-pressure reverse osmosis membrane, or a process including both of these systems. Good.

  According to the third embodiment, as in the first embodiment, the control device 24 outputs the water temperature adjusting device operation signal 26. However, as a basis for determining the value, the power cost of the filtration pump is also taken into account. This is the third feature. If boron does not meet the water quality standard value or voluntary standard value, it is necessary to lower the water temperature of seawater 10 and increase the boron rejection rate regardless of the cost, but if it is achieved In order to minimize the operation cost, it is effective to raise the water temperature.

[Example 4]
FIG. 5 is a block diagram showing the configuration of a seawater desalination apparatus according to Embodiment 4 of the present invention. The fourth embodiment is an example in which the filtration pump power cost calculating means 28 shown in the third embodiment is incorporated into the feedforward control example shown in the second embodiment.

[Example 5]
FIG. 6: shows the structure of the seawater desalination apparatus by Example 5 of this invention with a block diagram. The water temperature of the seawater 10 is adjusted by a water temperature adjusting device 12 to become water temperature adjusted seawater 14. The water temperature-adjusted seawater 14 is desalted by reverse osmosis membrane filtration 16 to become treated water 18. The boron concentration contained in the treated water 18 is measured by the treated water boron concentration measuring means 20 and output as a treated water boron concentration measured value 22.

  The filtration pump power cost calculating means 28 calculates the power cost of the filtration pump determined by the water temperature and the operation history. As an input to the filtration pump power cost calculation means 28, it is preferable that information on the water temperature in the reverse osmosis membrane filtration process 16 is always given online. Moreover, as the information of the film differential pressure that changes depending on the operation history, either actual data or a physical model may be used.

  The water temperature adjusting device operating cost calculating means 32 calculates the operating cost of the water temperature adjusting device determined by the adjustment amount. The output water temperature adjusting device operating cost information 34 is output to the control device 24 together with the filtration pump power cost information 30, the treated water boron concentration measurement value 22, and the target boron concentration information 36.

  The control device 24 outputs a water temperature adjustment device operation signal 26 to the water temperature adjustment device 12 based on the target boron concentration information 36, the treated water boron concentration measurement value 22, and the filtration pump power cost information 30. The water temperature adjustment device 12 changes the water temperature adjustment amount of the seawater 10 according to the water temperature adjustment device operation signal 26. Here, the water temperature adjusting device may have only one of the heating function and the cooling function, or may have both. The reverse osmosis membrane filtration process 16 can be a system using only a high-pressure reverse osmosis membrane, a system including a low-pressure reverse osmosis membrane after the high-pressure reverse osmosis membrane, or a process including both of these systems. Good.

  According to the fifth embodiment, the control device 24 outputs the water temperature adjusting device operation signal 26, but considers the trade-off between the power cost of the filtration pump and the operation cost of the water temperature adjusting device as the basis for determining the value. When boron cannot achieve the water quality standard value or the voluntary standard value, it is necessary to decrease the water temperature of the seawater 10 and increase the boron rejection rate regardless of the cost. For example, the operation amount of the water temperature adjustment device that minimizes the sum of the filtration pump power cost and the operation cost of the water temperature adjustment device while satisfying the condition that the boron concentration of the treated water is equal to or less than the target boron concentration given in advance is determined. A control method of driving is preferred.

  When the heat source of the water temperature adjusting device 12 is exhaust heat having pressure and it does not cost, it is effective to raise the water temperature in order to minimize the operation cost. However, when using devices that require cost such as heaters, absorption chillers, pumps, blowers, etc. for heating and cooling the water temperature adjusting device 12, the amount of change in the water temperature is reduced or not changed. It can be good. By taking the form of the fifth embodiment, the cost as a whole can be minimized and more efficient operation can be achieved.

  As mentioned above, “seawater” in each embodiment means seawater that has undergone pretreatment for passing water taken from the sea to the filtration step using a reverse osmosis membrane.

  10 ... seawater, 12 ... water temperature adjusting device, 14 ... water temperature adjusting seawater, 16 ... reverse osmosis membrane filtration treatment, 18 ... treated water, 20 ... treated water boron concentration measuring means, 22 ... Measured value of treated water boron concentration, 24 ... Control device, 26 ... Water temperature adjusting device operation signal, 28 ... Filter pump power cost calculation means, 30 ... Filter pump power cost information, 32・ ・ ・ Water temperature adjusting device operating cost calculation means 34… Water temperature adjusting device operating cost information 36 36 Target boron concentration information 38 38 Seawater boron concentration measuring means 40 40 Processed water boron concentration prediction Means 42 ... Processed boron concentration prediction value information 44 ... Seawater boron concentration measurement value

Claims (10)

In seawater desalination equipment using filtration by reverse osmosis membranes,
A water temperature adjustment device arranged upstream of the reverse osmosis membrane to change the temperature of the seawater;
Boron concentration measuring means for measuring the boron concentration of the treated water after the filtration treatment;
A control device configured to determine and operate an operation amount of the water temperature adjusting device based on the boron concentration information of the treated water and target boron concentration information given in advance; In the seawater desalination apparatus according to claim 1,
Filtration pump power cost calculating means for calculating filtration pump power cost information based on the water temperature of seawater after the water temperature adjustment by the water temperature adjusting device;
The apparatus further comprising: a control device that operates by determining an operation amount of the water temperature adjustment device based on the boron concentration information of the treated water, the target boron concentration information given in advance, and the filtration pump power cost information. In seawater desalination equipment using filtration by reverse osmosis membranes,
A water temperature adjustment device arranged upstream of the reverse osmosis membrane to change the temperature of the seawater;
Boron concentration measuring means for measuring boron concentration in seawater;
Treated water boron concentration prediction means for calculating the boron concentration prediction information of the treated water after the filtration treatment from the boron concentration of the seawater;
The said control apparatus provided with the control apparatus which determines and operates the operating amount of the said water temperature adjusting apparatus based on the boron concentration prediction information of the said treated water, and the target boron concentration information given beforehand. In the seawater desalination apparatus according to claim 3,
Filtration pump power cost calculating means for calculating filtration pump power cost information based on the water temperature of seawater after the water temperature adjustment by the water temperature adjusting device;
A control device for determining and operating the operation amount of the water temperature adjusting device based on the boron concentration prediction information of the treated water and the target boron concentration information given in advance and the filtration pump power cost information;
The apparatus further comprising: In seawater desalination equipment using filtration by reverse osmosis membranes,
A water temperature adjustment device arranged upstream of the reverse osmosis membrane to change the temperature of the seawater;
Boron concentration measuring means for measuring the boron concentration of the treated water after the filtration treatment;
Filtration pump power cost calculating means for calculating the filter pump power cost based on the water temperature of the seawater after the water temperature adjustment by the water temperature adjusting device;
A water temperature adjusting device operating cost calculating means for calculating an operating cost of the water temperature adjusting device;
A control device that operates by determining an operation amount of the water temperature adjusting device based on values of boron concentration of the treated water, preliminarily provided target boron concentration information, the filtration pump power cost, and the operating cost of the water temperature adjusting device; The apparatus comprising: In the seawater desalination apparatus according to claim 5,
The water temperature adjustment so as to minimize the sum of the filtration pump power cost information and the operation cost information of the water temperature adjustment device while satisfying the condition that the boron concentration information of the treated water is equal to or less than a predetermined target boron concentration information. And a control device for determining and operating the amount of operation of the device. In the seawater desalination apparatus according to claim 1,
The apparatus, wherein the water temperature adjusting device has at least a cooling function. The seawater desalination apparatus according to claim 1,
The said apparatus which uses the seawater taken from the location different from the said seawater to filter as a heat source of the said water temperature adjustment apparatus. In the seawater desalination apparatus according to claim 8,
The said apparatus whose seawater taken in from the said different location is seawater deep water or its concentrated water. The seawater desalination apparatus according to claim 1,
The apparatus, wherein the water temperature adjusting device includes at least a heat source, and uses exhaust heat of power generation equipment as the heat source.

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