Method for removing organic dissolved substances in water-steam cycles

Abstract

To provide a method for removing organic dissolved substances in water-steam cycle, which simultaneously achieves improved heat exchanger efficiency through the addition of droplet condensation promoters and the removal of organic dissolved substances from the water-steam cycle system excluding the target heat exchanger.SOLUTION: A method for removing organic dissolved substances in a water-steam cycle where organic chemicals are added upstream of a heat exchanger, the method for passing at least a part of the drain water from the heat exchanger through a filtration device to remove organic dissolved substances, in which the filtration device comprises a plurality of devices arranged in parallel, each comprising at least one of an ion exchange device, an activated carbon filtration apparatus, an RO membrane device, and an NF membrane device, arranged in parallel, a part of the drain water is passed through some of these devices, and when the filtration performance is determined to have decreased based on the amount of chemical added or water quality measurements from sensors, the water flow is switched to another device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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 need for efficient heat exchange, and in recent years, organic agents (droplet condensation promoters) that realize dropwise condensation have been used. For example, agents such as polyamines are sometimes added to boiler feedwater or steam in order to improve the heating efficiency of steam heat exchangers (Patent Document 1).

[0004] Some of these chemicals are contained in the recovered drain and circulate within the system together with the makeup water as boiler feed water.

[0005] In thermal power plants, two types of condensate treatment equipment have been used so far: 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-56524 Summary of the Invention [Problem to be solved by the invention]

[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] The present invention aims 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, In the method for removing organic dissolved substances by passing at least a portion of the drain water from the heat exchanger through a filtration device, The filtration device is 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; A method for removing organic dissolved substances in a water-steam cycle, characterized in that drain water is passed through some of the equipment, and when it is determined that the filtration performance has decreased based on the amount of chemicals added or the water quality measured by a sensor, the water is switched to passing through other equipment.

[0011] [2] The method for removing organic dissolved substances in a water-steam cycle according to [1], characterized in that 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 on or off depending 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 after a heat exchanger to which chemicals are added immediately before.

[0016] [7] In a method for removing organic dissolved substances in a water-steam cycle by adding an organic chemical upstream of a heat exchanger, The method for removing organic dissolved substances in a water-steam cycle comprises 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. [Effects of the Invention]

[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, etc., and to remove organic dissolved substances from a water-steam cycle system excluding the 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. [Brief explanation of the drawings]

[0021] [Figure 1]FIG. 1 is a flow diagram showing a method for removing organic dissolved substances in a water / steam cycle according to an embodiment. [Figure 2] FIG. 1 is a flow diagram showing a method for removing organic dissolved substances in a water / steam cycle according to an embodiment. [Figure 3] FIG. 1 is a flow diagram showing a method for removing organic dissolved substances in a water / steam cycle according to an embodiment. [Figure 4] FIG. 1 is a flow diagram showing a method for removing organic dissolved substances in a water / steam cycle according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0023] In Figures 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 piping 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 is equipped with 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, three-way valve 5 first connects pipes 4 and 6 so that water flows through one of filtration devices A. When the cumulative amount of chemical added approaches the preset upper limit of chemical absorption capacity of filtration device A, 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 same process is used to switch the flow of water from filtration device B to filtration device A.

[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 a pipe 10 to detect the water quality, such as the concentration of a 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 filter (shown as a dropwise condensation promoter removal device in the figure) or an electrodeionization device, but only a portion of the drainage may be passed through, or it may be passed through together with steam and drainage from other systems. If the filter or electrodeionization device cannot process high-temperature drainage (e.g., 60°C or higher), the water may be mixed with low-temperature water from other systems to lower the water temperature before being passed through.

[0036] In addition, in FIGS. 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 filtering device (droplet-form condensation promoter removing 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 perspective of preventing the 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. In this way, the container (vessel) of the filtration device containing the disposable filter media can 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 embodiment shown in Figs. [Example]

[0045] [Example 1] <Experimental conditions> In the water-steam cycle with 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. Steam was used for direct steam injection equipment, with 1 t / hr used, and the remaining 9 t / hr used for heating heat exchangers. In addition, steam was diverted from pipe 2 and part of the steam was supplied to the direct steam injection equipment.

[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, the water is passed through removal device A.

[0047] As a dropwise condensation promoter, a chemical agent mainly composed of N-oleyl-1,3-propanediamine was added at 20 ppm relative to the amount of steam.

[0048] In addition, a level gauge is provided in the chemical tank, and a mechanism is provided in which the amount of chemical dispensed from the tank is calculated from the detected value of the level gauge and an output signal is sent to the outside.

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

[0050] 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 / Discussion> By continuously adding 20 ppm of chemicals 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 chemicals was zero, with no organic matter detected at all. Furthermore, when the steam from the direct steam injection equipment was analyzed, the organic matter concentration was also found to be zero.

[0052] Two months after water began flowing through filtration device A, the three-way valve 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 was sent to the outside to replace the resin in filtration device A.

[0053] [Comparative Example 1] <Experimental conditions> 1, the three-way valve 5, the pipes 6, 7, 8, 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 / Discussion> The chemical component concentration detected by the direct steam injection equipment was 0.14 mg / L, which did not meet the steam quality standard of not containing TOC components.The chemical component analysis was performed after condensing the steam using a temporary heat exchanger (not shown) to cool it.

[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 not dispersed 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. [Explanation of symbols]

[0057] 1 boiler 3 Heat exchanger 5 Three-way valve 21 Controller 30 Electrodeionization equipment

Claims

1. A water-steam cycle in which a portion of steam from a boiler is supplied to a steam direct injection facility, the remainder of the steam from the boiler is supplied to a heat exchanger after adding a drop-like condensation promoter, and drain water from the heat exchanger is returned to the boiler, A method for removing a dropwise condensation promoter in a water-steam cycle, which comprises passing drain water from the heat exchanger through a filtration device to remove the dropwise condensation promoter, thereby preventing the dropwise condensation promoter from being contained in the steam supplied to the steam direct injection facility, comprising: The filtration device is 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; A method for removing droplets of condensation promoters in a water-steam cycle, characterized in that drain water is passed through some of the equipment, and when it is determined that the filtration performance has decreased based on the amount of chemicals added or the water quality measured by a sensor, the water is switched to passing through other of the equipment.

2. 2. The method for removing a drop-like condensation promoter 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. 2. The method for removing droplets of condensation promoter in a water-steam cycle according to claim 1, wherein the filter is switched on or off depending on either the threshold or trend of the sensor.

4. The method for removing droplets of condensation promoter 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 only the filter material can be replaced.

5. 2. The method for removing droplets of condensation promoter in a water-steam cycle according to claim 1, further comprising transmitting a switching operation signal for said equipment to an external device to prompt an operation manager to replace said filtering device.

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

7. A water-steam cycle in which a portion of steam from a boiler is supplied to a steam direct injection facility, the remainder of the steam from the boiler is supplied to a heat exchanger after adding a drop-like condensation promoter, and drain water from the heat exchanger is returned to the boiler, A method for removing dropwise condensation promoters in a water-steam cycle, characterized in that the drain water from the heat exchanger is passed through an electrodeionization device to remove the dropwise condensation promoters, thereby preventing the dropwise condensation promoters from being contained in the steam supplied to the steam direct injection facility.

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