TW201834737A - Reverse osmosis treatment method and device - Google Patents

Abstract

Raw water is supplied from piping 1 to a heat exchanger 2 and heated, and then water vapor from piping 3 is supplied to a heat exchanger 4 and further heated, after which the water vapor is supplied to a reverse osmosis (RO) device 6. Permeated water from the RO device 6 is taken out from piping 7 as treatment water, and concentrated water flows out to piping 8 and passes to an evaporator 11 of a heat pump 10 as a heat source fluid of the heat pump 10. Medium water heated by a condenser 13 of the heat pump 10 is circulated in a heat source fluid flow path in the heat exchanger 2.

Description

Reverse osmosis treatment method and device

[0001] The present invention relates to a reverse osmosis treatment method for treating water using a reverse osmosis membrane device, and more particularly to a reverse osmosis treatment method and apparatus for heating a feed water for a reverse osmosis membrane device with a heat pump.

[0002] Regarding the reverse osmosis membrane device (hereinafter referred to as the RO device), it is necessary to maintain the amount of treated water (the flux due to the decrease in viscosity of water is increased, and the recovery due to the increase in saturated solubility of cerium oxide) The rate is increased, and the feed water temperature is raised to about 25 °C. The heating of this water supply uses steam, warm water, electric heaters, etc., and will consume energy. [0003] In the seventh application of the Japanese Patent Application Laid-Open No. 2012-91118, it is described that the water supply of the RO device is heated to 23 to 25 ° C by a heat pump, and the heat source of the heat pump is not specifically described in the publication. [PRIOR ART DOCUMENT] [Patent Document 1] [Patent Document 1] Japanese Laid-Open Patent Publication No. 2012-91118 [0005] When the water supply of the RO device is heated by steam, warm water, an electric heater or the like, the heating cost is high. . Further, the energy source that is heated by the feed water is discarded together with the concentrated water, and it is an energy loss. [0006] Although the raw water can be exchanged with the concentrated water and the concentrated water is heat-recovered, since the temperature difference is small, it is necessary to increase the heat transfer area of the heat exchanger, so that the heat exchanger costs are increased. Moreover, since the temperature difference is necessary, it is impossible to recover the entire amount of the heating portion. [0007] In the case where the heat of the different devices (refrigerator, compressor, etc.) is set as the heat source, the piping with the RO device will become longer, so that the work cost is increased. Also, there is a case where the timing of the operation cannot be matched. [0008] In the case where the feed water of the RO device is heated by a heat pump, the heat source of the heat pump may consider concentrated water (hereinafter, referred to as RO concentrated water) or treated water of the RO device. However, since the concentration of the scale component (for example, hardness components such as cerium oxide and calcium) of the RO concentrated water is higher than the concentration of other salts and the concentration of the organic matter, the evaporator of the heat pump is likely to cause scale, slime, and the like. dirt.

[Problem to be Solved by the Invention] [0009] An object of the present invention is to reduce heating costs by heating a feed water for an RO device using a heat pump using RO concentrated water as a heat source. Further, in one aspect of the present invention, the object of the present invention is to prevent or suppress the scale, slime, and the like of the evaporator, the RO device, and the like of the heat pump. [Means for Solving the Problem] [0010] The reverse osmosis treatment method of the present invention is a method in which a raw water is heated by a heat pump, and a membrane separation treatment is performed by a reverse osmosis membrane device, wherein at least a part of the heat source fluid of the heat pump is used. Concentrated water from a reverse osmosis membrane unit. [0011] In one aspect of the present invention, the concentration of cerium oxide in the concentrated water of the heat source fluid outlet of the evaporator of the heat pump is less than the cerium oxide scale deposition concentration and/or the Langelier's index. In a method of 0 or less, at least one of the recovery rate of the reverse osmosis membrane device and the temperature of the raw water is adjusted. [0012] In one aspect of the invention, the raw water system is made alkaline at a specific pH or higher, or is acidic at a specific pH or lower. [0013] In one aspect of the present invention, a scale inhibitor and/or a slime inhibitor are added to the raw water. [0014] The reverse osmosis treatment apparatus of the present invention is characterized in that after the raw water is heated by a heat pump, the membrane separation treatment is performed by a reverse osmosis membrane device, wherein at least a part of the heat source fluid of the heat pump is provided with concentrated water of the reverse osmosis membrane device. Circulating waterway. [Effects of the Invention] According to the present invention, by heating a feed water for an RO device using a heat pump using RO concentrated water as a heat source, the heating cost can be reduced. Further, by using the RO concentrated water as a heat source, the apparatus of the present invention can be constructed only by piping work in the vicinity of the RO apparatus. [0016] By using a heat pump, the temperature difference from the raw water can be increased, and heat recovery can be performed with a small heat transfer area. According to one aspect of the present invention, RO concentrated water which is difficult to use as a heat source of a heat pump based on a high concentration of cerium oxide and a salt concentration can be directly used as a heat pump heat source.

[0019] Hereinafter, embodiments of the present invention will be described with reference to Fig. 1 . The RO-treated raw water is supplied from the pipe 1 to the heat exchanger 2, heated, and then supplied from the pipe 3 to the heat exchanger 4, and further heated, and then supplied to the RO device 6. The permeated water of the RO device 6 is taken out as the treated water from the pipe 7, and the concentrated water flows out to the pipe 8, and flows as a heat source fluid of the heat pump 10 to the evaporator 11 of the heat pump 10. [0021] In the heat source fluid flow path of the heat exchanger 2, medium water (water as a heat transfer medium) heated by the condenser 13 of the heat pump 10 is circulated and circulated. [0022] The heat pump 10 is configured to compress a heat medium such as a chlorofluorocarbon substitute or the like from the evaporator 11 by a compressor 12 and introduce it into a condenser 13, and the heat medium from the condenser 13 is introduced to the heat medium via the expansion valve 14. Evaporator 11. [0023] The medium water from the heat exchanger 2 is introduced into the condenser 13 via the pipe 15 and the pump 17, and the medium water heated by the condenser 13 is sent to the heat exchanger 2 via the pipe 16. [0024] In the heat source fluid flow path of the evaporator 11, the concentrated water from the RO device 6 is introduced from the pipe 8. The concentrated water cooled by the heat exchange is discharged through the piping 9. [0025] In the heat source fluid flow path of the heat exchanger 4, steam is supplied. [0026] The concentration of the scale component of the concentrated water of the RO device 6 and the concentration of the organic matter are higher than that of the raw water, so that the fouling of the evaporator 11 and the pipes 8 and 9 of the heat pump 10 and the occurrence of slime are high, so that it is prevented. Or suppression (hereinafter referred to as prevention). Further, in the RO device 6, it is also necessary to prevent the occurrence of scale and slime. [0027] In this embodiment, in order to prevent fouling and slime of the evaporator 11, the RO device 6, and the pipes 8, 9, the following measures i), ii) or iii) are carried out. [0028] i) the concentration of cerium oxide in the concentrated water flowing through the heat source fluid outlet 11a of the evaporator 11 does not exceed the concentration of the cerium oxide scale deposition, and/or the Langerial index becomes 0 or less. Adjust one or both of the RO recovery rate and the raw water temperature. [0029] That is, [the cerium oxide concentration of the heat pump evaporator outlet 11a] is lower than [the cerium oxide saturation solubility], and/or [the heat pump evaporator outlet 11a of the Langella index] becomes [ In the case of 0 or less, one or both of the RO recovery rate and the raw water temperature are increased. [0030] The Langeriya index (LSI) of the RO concentrated water and the evaporator outlet is generally obtained by the following formula (1). In the formula (1), the pH of the pH-based concentrated water or the evaporator outlet. The theoretical pH value in the case where the pHs are concentrated water or the calcium carbonate in the evaporator is in an equilibrium state of neither dissolution nor precipitation, can be obtained by the following formula (2). (2) In the formula (2), the A value is a correction value determined based on the concentration of the evaporation residue. The concentration of the evaporation residue is related to the conductivity, so the evaporation residue concentration can be obtained from the conductivity using a specific conversion formula. The B value is a correction value determined by the water temperature. The C value is a correction value determined by the hardness of the calcium. The D value is the correction value determined by the total alkalinity. [0031] One of the RO permeated water may be added to the RO concentrated water to form a water quality suitable for circulation to the heat pump evaporator. That is, the addition of RO to a portion of the water to the RO concentrated water is also included in the "reduced recovery rate". [0032] If, by reducing the recovery rate or increasing the temperature of the raw water, the concentration of cerium oxide in the RO concentrated water and the Langerial index can be set as the non-occurring conditions of the scale. For example, by setting the concentration of cerium oxide in concentrated water at 23 to 25 ° C to 100 to 120 ppm or less, it is possible to prevent cerium oxide fouling. [0033] ii) The pH of the raw water is adjusted so that the scale of the raw water is not precipitated at the RO device 6 and the heat pump evaporator 11. Specifically, the pH is set to 9 or more (for example, 9 to 11) under the condition that the Ca hardness of the raw water is 5 mg/L or less. Alternatively, the pH of the raw water is set to 6 or less (for example, 4 to 6). By ionizing cerium oxide at a high pH, gelation can be suppressed, and scale deposition can be suppressed. Further, by setting the raw water to a low pH, the precipitation rate of cerium oxide can be lowered to suppress the scale formation of cerium oxide. [0034] iii) In order to prevent fouling and slime from being deposited in the RO device 6 and the heat pump evaporator 11, a chemical (a scale inhibitor, a slime inhibitor, etc.) is added to the raw water. The antifouling agent and the slime preventing agent are not particularly limited, and various products can be used. [0035] In order to set the Languelia index to 0 or less, the pH of the raw water may be 6 or less (for example, 4 to 6), or a softener may be provided in the front stage of the RO membrane to remove the hardness component. Further, the scale inhibitor for calcium deposits may be added to the raw water. In this case, the Langerial index may exceed zero. For example, depending on the performance of the scale inhibitor, the Langeriya index can be controlled to be 0.5 or less by using the organic polymer scale inhibitor. [0036] The raw water may be exemplified by industrial water (river water, lake water, etc.), ground water, tap water, treated water of various kinds of drainage, and the like, but is not limited thereto. [0037] According to the system of Fig. 1, the well water (18 ° C) is heated at 25 ° C and treated with RO at 20 m ³ /h, and the permeated water is at 25 ° C, 14 m ³ / h, and the concentrated water is 25 ° C, 6 m ³ /h for membrane separation, and when the heat pump is operated with COP (performance coefficient) 5, as shown in Fig. 1 to set the heat pump 10 and the heat exchanger 2, 4, the evaporator outlet 11a When the temperature of the concentrated water is 20 ° C, the amount of steam used in the heat exchanger 4 when the system is operated is equivalent to 101.8 kW. [0038] In the reverse osmosis membrane device with heat pump of the present invention, the cerium oxide and the hardness component (or Langjie) may be disposed at part or all of the inlet and outlet of the RO membrane and the heat source fluid inlet and outlet of the evaporator. a measurement device (sensor, calculation unit, etc.) such as water temperature, etc., based on the measured value of the machine, setting the RO membrane recovery rate, pH adjustment (control of the acid or alkali addition mechanism), and the drug A part or all of the control unit that is automatically controlled (addition mechanism of the scale inhibitor and the slime preventive agent) is added, and the entire apparatus is designed to be automatically operated. By providing the above-described measuring device at the heat source fluid outlet to control the operating conditions of the RO membrane, the reverse osmosis membrane device equipped with the heat pump can be stably operated as a whole. On the other hand, in the system of Fig. 1, when the heat exchanger 2 and the heat pump 10 are not provided, the amount of steam used in the heat exchanger 4 during the RO treatment under the same conditions is equivalent to 162.8 kW. [0040] The above embodiment is an example of the present invention, and the present invention may be formed in a form other than the drawings. The present invention has been described in detail with reference to the preferred embodiments of the present invention. It is to be understood that various modifications may be made without departing from the spirit and scope of the invention. The present application is based on Japanese Patent Application No. 2017-051091, filed on March 16, 2017, the entire content of which is hereby incorporated by reference.

[0042]

2, 4‧‧ ‧ heat exchanger

6‧‧‧RO device

10‧‧‧ heat pump

11‧‧‧Evaporator

12‧‧‧Compressor

13‧‧‧Condenser

14‧‧‧Expansion valve

1 is a block diagram of a reverse osmosis processing apparatus according to an embodiment of the present invention.

Claims (5)

A reverse osmosis treatment method is a membrane separation treatment using a reverse osmosis membrane device after heating raw water by a heat pump, wherein concentrated water of the reverse osmosis membrane device is used as at least a part of a heat source fluid of the heat pump. For example, in the reverse osmosis treatment method of claim 1, wherein the concentration of cerium oxide in the concentrated water of the heat source fluid outlet of the evaporator of the heat pump is less than the concentration of cerium oxide deposit and/or the Langeriya index. In a method of 0 or less, at least one of the recovery rate of the reverse osmosis membrane device and the temperature of the raw water is adjusted. The reverse osmosis treatment method according to claim 1 or 2, wherein the raw water system is made alkaline at a specific pH or higher, or is acidic at a specific pH or lower. The reverse osmosis treatment method according to any one of claims 1 to 3, wherein a scale inhibitor and/or a slime preventive agent are added to the raw water. A reverse osmosis treatment apparatus is a membrane separation treatment by heating a raw water by a heat pump and using a reverse osmosis membrane device, wherein at least a part of the heat source fluid of the heat pump is provided with a concentrated water of the reverse osmosis membrane device. Waterway.