JP7790466B2 - Method for removing organic dissolved substances in water/steam cycles - Google Patents

Description

The present invention relates to a method for removing organic dissolved substances from a water-steam cycle.

In recent years, there has been growing attention being 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.

From the perspective of carbon neutrality, there is a high need 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 to improve the heating efficiency of steam heat exchangers (Patent Document 1).

Some of these chemicals are trapped in the recovered drain and, together with the makeup water, are recirculated within the system as boiler feed water.

Conventionally, thermal power plants use two types of condensate treatment equipment: 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 by the plant's constituent materials and present in the condensate, as well as seawater components in the unlikely event of a leak of seawater or freshwater used as cooling water for the condenser.

Japanese Patent Application Laid-Open No. 2019-56524

If part of the steam generated by the boiler is directly supplied to a steam-using location other than a heat exchanger, it is necessary to thoroughly remove the organic chemicals contained in this steam.

The objective of the present invention is to provide a method for removing organic dissolved substances in a water-steam cycle that can simultaneously improve the efficiency of the heat exchanger by adding a dropwise condensation promoter, etc., and remove organic dissolved substances from the water-steam cycle system excluding the target heat exchanger.

The gist of the present invention is as follows:

[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, comprising:
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 of the equipment.

[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.

[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.

[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 just the filter material can be replaced.

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

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

[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:
A method for removing organic dissolved substances in a water-steam cycle, 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 [1] to [7], wherein the organic chemical is a dropwise condensation promoter.

The method for removing organic dissolved substances in a water-steam cycle of the present invention can simultaneously improve the efficiency of heat exchangers by adding a dropwise condensation promoter, etc., and remove organic dissolved substances from the water-steam cycle system, excluding heat exchangers that are subject to dropwise condensation.

Furthermore, in one aspect of the present invention, by focusing on disposable materials rather than resin recycling, recycling equipment is not required, so the equipment size is small and the hurdles to installing the equipment are significantly reduced.

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

FIG. 1 is a flow diagram showing a method for removing organic dissolved substances in a water/steam cycle according to an embodiment. FIG. 1 is a flow diagram showing a method for removing organic dissolved substances in a water/steam cycle according to an embodiment. FIG. 1 is a flow diagram showing a method for removing organic dissolved substances in a water/steam cycle according to an embodiment. FIG. 1 is a flow diagram showing a method for removing organic dissolved substances in a water/steam cycle according to an embodiment.

An example of the method for removing organic dissolved substances in a water-steam cycle of the present invention is shown in Figures 1 to 4.

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 condenses 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-shaped condensation promoter removal device in this embodiment) A or B, where the droplet-shaped condensation promoter is removed. The treated water from which the droplet-shaped condensation promoter has been removed is returned to boiler 1 through pipe 8 or 9 and pipe 10. Along the way, makeup water is supplied from makeup water pipe 11.

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 the chemical solution, a chemical injection pump, a chemical addition line, etc.

The three-way valve 5 is controlled by the controller 21 as follows:

In Figure 1, the dropwise condensation promoter addition device 20 is equipped with a mechanism for detecting the amount of chemical added.

When operation begins, three-way valve 5 first connects pipes 4 and 6 so that water flows through one of the filters, filter A. When the cumulative amount of chemical added approaches the preset upper limit for chemical absorption by filter A, three-way valve 5 switches and water flows through filter B. While water is flowing through filter B, the filter material in filter A is replaced. The same process is used to switch water flow from filter B to filter A.

The amount of chemical to be added may be determined from the amount of chemical liquid remaining in the chemical tank, or from the detection value of a flow meter installed in the chemical addition line or the operating time of the chemical injection pump.

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

This water quality sensor 22 continuously monitors 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. The water quality sensor 22 can be one or more of a chemical concentration meter, an electrical conductivity meter, a pH meter, a quartz oscillator, etc.

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

The detected values of the concentration sensor 24 and drain flow meter 25 are input to the controller 21, and when the load (the cumulative value of the product of concentration and flow rate over time) 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 upstream of the heat exchanger may be used to monitor the drain flow rate passing through filtration device A or B.

Figure 4 shows yet another embodiment of the present invention. In Figure 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 Figure 1.

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

In addition, in Figures 1 to 4, the entire amount of drainage that has passed through the target heat exchanger is passed through a filtration device (shown as a dropwise condensation promoter removal device in the figures) or an electrodeionization device, but only a portion of it may be passed through, or it 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), it may be passed through after being combined with low-temperature water from other systems to lower the water temperature.

In addition, while Figures 1 to 3 show two filtration systems installed in parallel, three or more systems may be installed in parallel and switched as needed.

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

The filtration devices (droplet condensation promoter removal devices) used in Figures 1 to 3 include ion exchange resin towers, activated carbon towers, RO membrane devices, and NF membrane devices.

From an economical standpoint, it is desirable to select anion exchange resin, cation exchange resin, or mixed bed resin as the ion exchange resin depending on the type of organic chemical being added.

For example, if 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 if it is a sarcosine, it is preferable to use an anion exchange resin.

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

More preferably, the filtration device is an ion exchange resin tower using high-spec ion exchange resins used in facilities with high levels of pure water purity, or an RO membrane device, from the perspective of preventing impurities from leaching out.

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

When an RO membrane device or NF membrane device is used as the filtration device, the embodiments shown in Figures 1 and 2 are applicable.

[Example 1]
<Experimental conditions>
In the 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. Steam was used in the direct steam injection facility at 1 t/hr, with the remaining 9 t/hr used for heating heat exchangers. Steam was also diverted from pipe 2, with a portion of the steam being supplied to the direct steam injection facility.

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. Filtration devices A and B are equipped with ion exchange towers. First, the water is passed through removal device A.

As a dropwise condensation promoter, a chemical based on N-oleyl-1,3-propanediamine was added at 20 ppm relative to the steam volume.

In addition, a level gauge is installed in the chemical tank, and a mechanism is in place to determine the amount of chemical dispensed from the tank from the detected value of this level gauge and send an output signal to the outside.

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 system is configured to send a three-way valve switching signal when this threshold is exceeded.

Filtration devices A and B are filled with recycled high-grade ion exchange resin that was previously used to produce ultrapure water at another plant.

<Results/Discussion>
By continuously adding 20 ppm of chemicals to the amount of steam, the expected improvement in heat transfer efficiency was achieved in the heat exchanger 3. Furthermore, when drain water was sampled and analyzed in the pipe 10, the concentration of organic matter derived from the chemicals was zero, meaning that no organic matter was detected at all. Furthermore, when the steam from the direct steam injection equipment was analyzed, the organic matter concentration was also zero.

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.

[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. Except for this, the test was carried out under the same conditions as in Example 1.

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

From the above, it was confirmed that by filtering and removing the organic chemicals added upstream of heat exchanger 3 through the drain, the organic chemicals do not diffuse throughout the entire steam cycle system.

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.

1 Boiler 3 Heat exchanger 5 Three-way valve 21 Controller 30 Electrodeionization device

Claims (7)

In 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. 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. 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. 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. 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. 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. In 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 .