Method for removing organic dissolved substance in water / vapor cycle

Abstract

A method for removing an organic dissolved substance in a water / vapor cycle in which an organic chemical is added upstream of a heat exchanger, said organic dissolved substance being removed by causing at least a portion of drain water of the heat exchanger to flow through a filtration device, said method being characterized in that a plurality of apparatuses of at least one type among ion exchange devices, activated carbon filtration devices, RO membrane devices, and NF membrane devices are arranged side by side as the filtration device, the drain water is made to flow through a portion of said apparatuses, and when, on the basis of the added quantity of the organic chemical or a water quality measured value from a sensor, it has been determined that the filtration performance has deteriorated, the water flow-through is switched to another of the apparatuses.

Description

Method for removing organic dissolved substances in water / steam cycles

[0001] The present invention relates to a method for removing organic dissolved substances in a water-steam cycle.

[0002] In recent years, there has been growing attention paid to the quality of steam used in factories. In particular, in the beverage and food industries, there is a need to reduce the impact of chemicals on the human body, and in semiconductor factories, there is a need to reduce impurities in humidified steam.

[0003] From the viewpoint of carbon neutrality, there is a high demand for efficient heat exchange, and in recent years, organic chemicals (droplet condensation promoters) that achieve dropwise condensation have been used. For example, chemicals such as polyamines are sometimes added to boiler feedwater or steam in order to improve the heating efficiency of steam-type heat exchangers (Patent Document 1).

[0004] Some of these chemicals are contained in the recovered drain water, which, together with the make-up water, becomes boiler feed water and circulates within the system.

[0005] In thermal power plants, two types of condensate treatment systems have been used: a standalone condensate demineralizer and a combination of a condensate pre-filter and a condensate demineralizer. These demineralization systems remove trace amounts of corrosion products and ions generated from the plant's constituent materials and present in the condensate, as well as seawater components in the event of a leak of seawater or freshwater used as cooling water for the condenser.

[0006] Japanese Patent Application Laid-Open No. 2019-56524

[0007] When a portion of the steam generated from a boiler is directly supplied to a location other than a heat exchanger where the steam is used, it is necessary to thoroughly remove the organic chemicals contained in the steam.

[0008] An object of the present invention is to provide a method for removing organic dissolved substances in a water-steam cycle, which can improve the efficiency of a heat exchanger by adding a dropwise condensation promoter or the like, and can also remove organic dissolved substances from the water-steam cycle system excluding the target heat exchanger.

[0009] The gist of the present invention is as follows.

[0010] [1] A method for removing organic dissolved substances in a water-steam cycle in which an organic chemical is added upstream of a heat exchanger, wherein at least a portion of the drain water from the heat exchanger is passed through a filtration device to remove the organic dissolved substances, wherein the filtration devices are a plurality of devices each consisting of at least one of an ion exchange device, an activated carbon filtration device, an RO membrane device, and an NF membrane device, arranged in parallel, and the drain water is passed through some of the devices, and when it is determined that the filtration performance of some of the devices has deteriorated based on the amount of chemical added or water quality measured by a sensor, the water passage is switched to another of the devices.

[0011] [2] The method for removing organic dissolved substances in a water-steam cycle according to [1], wherein the sensor is one or more of an electrical conductivity meter, a pH meter, a chemical concentration meter, and a quartz oscillator.

[0012] [3] The method for removing organic dissolved substances in a water-steam cycle according to [1], characterized in that the filtration device is switched based on either the threshold value or trend of the sensor.

[0013] [4] The method for removing organic dissolved substances in a water-steam cycle according to [1], characterized in that the filter material in the filtration device has a history of use in another facility, and the cartridge filled with the filter material or only the filter material can be replaced.

[0014] [5] The method for removing organic dissolved substances in a water-steam cycle according to [1], characterized in that a switching operation signal for the equipment is transmitted to the outside to prompt an operation manager to replace the filtration device.

[0015] [6] The method for removing organic dissolved substances in a water-steam cycle according to [1], characterized in that the filtration device is installed in the downstream of a heat exchanger to which a chemical is added immediately before.

[0016] [7] A method for removing organic dissolved substances in a water-steam cycle in which an organic chemical is added upstream of a heat exchanger, the method comprising passing at least a portion of the drain water from the heat exchanger through an electrodeionization device to remove the organic dissolved substances.

[0017] [8] The method for removing organic dissolved substances in a water-steam cycle according to any one of [1] to [7], wherein the organic chemical is a dropwise condensation promoter.

[0018] According to the method for removing organic dissolved substances in a water-steam cycle of the present invention, it is possible to improve the efficiency of a heat exchanger by adding a dropwise condensation promoter or the like, and to remove organic dissolved substances from a water-steam cycle system excluding a heat exchanger that is the target of dropwise condensation.

[0019] Furthermore, in one embodiment of the present invention, by using disposable materials as the standard rather than resin recycling, recycling equipment is not required, so the equipment size is small and the hurdle of introducing the equipment can be significantly reduced.

[0020] In one aspect of the present invention, organic chemicals intentionally added immediately before a specific heat exchanger are filtered through an outlet drain, preventing the organic chemicals from diffusing throughout the entire steam cycle system.

[0021] It is a flow diagram showing a method for removing organic dissolved substances in a water-steam cycle according to an embodiment. It is a flow diagram showing a method for removing organic dissolved substances in a water-steam cycle according to an embodiment. It is a flow diagram showing a method for removing organic dissolved substances in a water-steam cycle according to an embodiment. It is a flow diagram showing a method for removing organic dissolved substances in a water-steam cycle according to an embodiment. It is a flow diagram showing a method for removing organic dissolved substances in a water-steam cycle according to an embodiment.

[0022] An example of the method for removing organic dissolved substances in a water-steam cycle according to the present invention is shown in FIGS.

[0023] 1 to 3, steam generated in boiler 1 is sent to heat exchanger 3 through pipe 2. The steam is cooled in heat exchanger 3 and condensed to become drain water. This drain water flows from pipe 4 to pipe 6 or 7 via three-way valve 5, and then flows to filtration device (droplet-like condensation promoter removal device in this embodiment) A or B, where the droplet-like condensation promoter is removed. The treated water from which the droplet-like condensation promoter has been removed is returned to boiler 1 through pipe 8 or 9 and pipe 10. During this process, makeup water is supplied from makeup water pipe 11.

[0024] In the pipe 2, a dropwise condensation promoter is added as an organic dissolved substance by a dropwise condensation promoter adding device 20. The dropwise condensation promoter adding device 20 includes a chemical tank for storing a chemical solution, a chemical injection pump, a chemical addition line, and the like.

[0025] The three-way valve 5 is controlled by the controller 21 as follows.

[0026] In FIG. 1, the dropwise condensation promoter adding device 20 is provided with a mechanism for detecting the amount of chemical added.

[0027] At the start of operation, the three-way valve 5 first connects the pipes 4 and 6 so that water flows through one of the filtration devices, A. When the cumulative amount of chemical added approaches the preset upper limit of the chemical adsorption capacity of filtration device A, the three-way valve 5 is switched to allow water to flow through filtration device B. While water is flowing through filtration device B, the filter material of filtration device A is replaced. The water flow switching from filtration device B to filtration device A is also performed in the same way.

[0028] The amount of chemical to be added may be determined from the amount of chemical solution reduced in the chemical tank, or may be determined from the value detected by a flow meter provided in the chemical addition line or the operating time of the chemical injection pump.

[0029] Another embodiment of the present invention is shown in Fig. 2. In Fig. 2, a water quality sensor 22 is provided in the pipe 10 to detect the water quality such as the concentration of the dropwise condensation promoter.

[0030] This water quality sensor 22 continuously monitors the water quality, and when the sensor value corresponding to the organic chemical concentration exceeds a threshold value or when there is a predetermined trend fluctuation (fluctuation in time-series data) in the sensor value, it switches the three-way valve 5 and switches the filtration device through which water passes. As the water quality sensor 22, in addition to a chemical concentration meter, one or more of an electrical conductivity meter, a pH meter, a quartz oscillator, etc. can be used.

[0031] Yet another embodiment of the present invention is shown in Fig. 3. In Fig. 3, a concentration sensor 24 for detecting the concentration of the added chemical is provided in the pipe 4, and a flow meter 25 for detecting the drain flow rate is provided in the pipe 10. Note that the flow meter 25 may also be provided in the pipe 4.

[0032] The detected values ​​of the concentration sensor 24 and the drain flow meter 25 are input to the controller 21, and when the load (the integrated value over time of the product of the concentration and the flow rate) approaches the upper limit of the filtration device, the three-way valve 5 is switched. Note that instead of the drain flow meter 25, a steam flow meter in the upstream stage of the heat exchanger may be used to grasp the drain flow rate passing through the filtration device A or B.

[0033] Fig. 4 shows another embodiment of the present invention. In Fig. 4, drain from heat exchanger 3 is sent to electrodeionization device 30 via pipe 4, and deionized water is sent to boiler 1 via pipe 10. The rest of the configuration is the same as in Fig. 1.

[0034] In FIGS. 1 to 4, the steam generated in the boiler is sent only to the heat exchanger 3 to which a single organic chemical is added, but the present invention is not limited to this.

[0035] 1 to 4, the entire amount of drainage that has passed through the target heat exchanger is passed through a filtration device (a dropwise condensation promoter removal device in the drawings) or an electrodeionization device, but only a portion of the drainage may be passed through, or the drainage may be passed through together with steam and drainage from other systems. If the filtration device or electrodeionization device cannot process high-temperature drainage (e.g., 60°C or higher), the drainage may be passed through after being mixed with low-temperature water from other systems to lower the water temperature.

[0036] 1 to 3, two systems of filtration equipment are installed in parallel, but three or more systems may be installed in parallel and switched as needed.

[0037] The removal level of the organic dissolved substances may be complete removal or reduction, and the removal level may be determined depending on the required concentration, for example.

[0038] Examples of the filtration device (droplet-form condensation promoter removal device) used in FIGS. 1 to 3 include an ion exchange resin tower, an activated carbon tower, an RO membrane device, and an NF membrane device.

[0039] From an economical point of view, it is desirable to select an anion exchange resin, a cation exchange resin, or a mixed bed resin as the ion exchange resin depending on the type of organic chemical to be added.

[0040] For example, when the chemical to be added is a polyamine (specifically, OLDA (N-oleyl-1,3-propanediamine)), it is preferable to use a cation exchange resin, and when it is a sarcosine, it is preferable to use an anion exchange resin.

[0041] It is also desirable that the ion exchange resin is resistant to deterioration even in high-temperature drain water.

[0042] More preferably, the filtration device is an ion exchange resin tower using high-spec ion exchange resins that are used in facilities with high levels of pure water, or an RO membrane device, from the viewpoint of preventing elution of impurities.

[0043] In the present invention, a drain cooling heat exchanger for cooling the drain water may be installed upstream of the filtration device, allowing the container (vessel) of the filtration device containing the disposable filter media to be made of a non-metallic material, improving operability and economy.

[0044] When an RO membrane device or an NF membrane device is used as the filtration device, the embodiments shown in FIGS. 1 and 2 are applied.

[0045] [Example 1] <Experimental Conditions> In a water / steam cycle having the configuration shown in Figure 1, the boiler was operated at a steady-state steam generation rate of 10 t / hr and a normal operating pressure of 0.78 MPa. The steam was used in a direct steam injection facility at a rate of 1 t / hr, with the remaining 9 t / hr being used for a heat exchanger for heating. In addition, steam was diverted from pipe 2 and part of the steam was supplied to the direct steam injection facility.

[0046] The drain water from the heat exchanger is filtered by filtration device A or B, and then supplemented with makeup water to become boiler feed water again. Ion exchange towers are installed as filtration devices A and B. First, water is passed through removal device A.

[0047] As a dropwise condensation promoter, a chemical agent containing N-oleyl-1,3-propanediamine as a main component was added in an amount of 20 ppm relative to the amount of steam.

[0048] A level gauge is provided in the chemical tank of the dropwise condensation accelerator adding device 20, and a mechanism is provided to determine the amount of chemical to be dispensed from the tank based on the detected value of the level gauge and to send an output signal to the outside.

[0049] The value (threshold) at which the ion exchange resin breaks through is set to 80% of the value calculated from the theoretical value, and the three-way valve switching signal is sent when this threshold is exceeded.

[0050] The filtration devices A and B were filled with recycled high-grade ion exchange resin that had been used to produce ultrapure water at another plant.

[0051] <Results and Discussion> By continuously adding 20 ppm of chemical to the amount of steam, the expected improvement in heat transfer efficiency was achieved in heat exchanger 3. Furthermore, when drain water was sampled and analyzed in pipe 10, the concentration of organic matter derived from the chemical was zero, with no detection whatsoever. Furthermore, when the steam from the direct steam injection equipment was analyzed, the organic matter concentration was also zero.

[0052] Two months after water began flowing through filtration device A, three-way valve 5 was switched based on the cumulative amount of chemical used, and water was switched to flow through filtration device B. At the same time, a signal to replace the resin in filtration device A was sent to the outside.

[0053] 1, the three-way valve 5, the pipes 6, 7, 8, and 9, and the filtration devices A and B were omitted, and the pipes 4 and 10 were directly connected. Other than this, the test was carried out under the same conditions as in Example 1.

[0054] <Results and Discussion> The concentration of chemical components detected by the direct steam injection equipment was 0.14 mg / L, which did not meet the standard for steam quality that does not contain TOC components. The analysis of chemical components was performed after condensing the steam using a temporary heat exchanger (not shown) that cools the steam.

[0055] From the above, it was confirmed that by filtering and removing the organic chemicals added upstream of the heat exchanger 3 through the drain, the organic chemicals are prevented from diffusing throughout the entire steam cycle system.

[0056] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications are possible within the scope of the invention.

[0057] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications are possible within the scope of the effects of the invention. This application is based on Japanese Patent Application No. 2024-066945 filed on April 17, 2024, the entire contents of which are incorporated by reference.

[0058] REFERENCE SIGNS LIST 1 Boiler 3 Heat exchanger 5 Three-way valve 20 Droplet condensation promoter adding device 21 Controller 30 Electrodeionization device

Claims

1. A method for removing organic dissolved substances in a water-steam cycle in which an organic chemical is added upstream of a heat exchanger, wherein at least a portion of the drain water from the heat exchanger is passed through a filtration device to remove the organic dissolved substances, wherein the filtration device is a plurality of devices, each device being at least one of an ion exchange device, an activated carbon filtration device, an RO membrane device, and an NF membrane device, arranged in parallel, and wherein the drain water is passed through some of the devices, and when it is determined that the filtration performance of some of the devices has deteriorated based on the amount of chemical added or water quality measured by a sensor, the water passage is switched to another of the devices.

2. The method for removing organic dissolved substances in a water-steam cycle according to claim 1, wherein the sensor is one or more of an electrical conductivity meter, a pH meter, a chemical concentration meter, and a quartz oscillator.

3. The method for removing organic dissolved substances in a water-steam cycle according to claim 1, wherein the filtration device is switched on or off depending on either the threshold value or trend of the sensor.

4. The method for removing organic dissolved substances in a water-steam cycle according to claim 1, characterized in that the filter material in the filtration device has a history of use in another facility, and the cartridge filled with the filter material or just the filter material can be replaced.

5. A method for removing organic dissolved substances in a water-steam cycle according to claim 1, characterized in that a switching operation signal for said equipment is sent to the outside to prompt an operation manager to replace said filtration device.

6. The method for removing organic dissolved substances in a water-steam cycle according to claim 1, wherein the filtration device is installed in the downstream of a heat exchanger to which a chemical is added immediately before.

7. A method for removing organic dissolved substances in a water-steam cycle in which an organic chemical is added upstream of a heat exchanger, comprising passing at least a portion of the drain water from the heat exchanger through an electrodeionization device to remove the organic dissolved substances.

8. A method for removing organic dissolved substances in a water-steam cycle according to any one of claims 1 to 7, wherein the organic chemical is a dropwise condensation promoter.

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