JP2005349308A - Method and apparatus for recovering chemical in condensate circulating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for recovering a chemical in a condensate circulating system, by each of which the chemical to be discharged to the outside of the condensate circulating system is decreased, a bad influence to be exerted on the external environment is lessened and the running cost necessary for feeding the chemical is restrained from being raised. <P>SOLUTION: This apparatus for recovering the chemical in the condensate circulating system and the water to be discharged from the condensate circulating system is provided with a steam recovering means 413 for recovering steam, a condensing means 421 for condensing steam together with the chemical and a mixing means 431 for mixing water with a condensate so that the water mixed by the mixing means 431 is returned to the condensate circulating system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for recovering chemicals used for pH adjustment and the like to be introduced into a plant such as a secondary cooling system of a nuclear power plant, a thermal power plant, or a combined cycle turbine plant, and a recovery device using the recovery method.

  In plants such as nuclear power plant secondary cooling system (condensate system), thermal power plant, combined cycle turbine plant, etc., the pH of circulating water flowing through the plant is adjusted to prevent corrosion of pipes. Yes. For example, in the case of a secondary cooling system at a nuclear power plant, steam generated by a steam generator is depressurized by a high-pressure turbine and a low-pressure turbine, and then condensed by a condenser to form water. A condensate circulation system is formed that returns to the steam generator through the heater, deaerator, and high-pressure side heater (hereinafter, the condensate circulation system is referred to as a system). In addition, a condenser may be provided with a condensate recovery tank that recovers feed pump seal water used in the system.

  In the system, chemicals such as ammonia (NH3) and hydrazine (N2H4) are added to water circulating in the system (hereinafter referred to as circulating water) to adjust the quality of the circulating water. By adding chemicals and adjusting the pH of the circulating water, pipe corrosion is prevented.

In the condenser of the above system, in order to remove the non-condensable gas mixed in the water and steam flowing into the condenser, the air accumulated in the condenser is evacuated and exhausted. . At this time, a part of the vapor containing the chemicals is discharged together with the air. This steam-containing air is separated into gas and liquid in a separator tank and separated into air and water. The chemical-containing vapor is released into the atmosphere together with the chemical, and the separated water is drained after being treated with a wastewater treatment device. Yes.
JP 2001-318188 A JP 2003-19438 A

  However, chemicals (ammonia (NH3), hydrazine (N2H4)), etc. that are introduced into the circulating water circulating in the system are toxic. If air (steam) containing high-concentration chemicals is released to the atmosphere, it may cause environmental damage. It becomes.

  In particular, in recent years, there is a tendency to increase the pH of the circulating water in the system for operation, and the chemical concentration in the circulating water is increasing. In such a case, the chemical concentration in the exhaust gas from the condenser, and also the chemical concentration in the exhaust gas discharged from the separator tank to the atmosphere is higher than the conventional one, which is not preferable from the viewpoint of environmental problems. Moreover, chemicals, water, and the like are lost from the system due to atmospheric release, which increases running costs.

  In view of such problems, an object of the present invention is to reduce the outflow of chemicals to the outside of the system, to reduce adverse effects on the external environment, and to suppress an increase in running cost such as chemical injection.

  In order to achieve the above object, the present invention is a recovery method for recovering chemicals from the water discharged outside the system out of the circulating water flowing in the pipes provided in the system. A steam recovery process for recovering the discharged steam and drain water, a liquefaction process for liquefying the steam recovered in the steam recovery process together with a chemical contained in the steam, and a drain recovered in the steam recovery process A mixing step of mixing water and water liquefied in the liquefaction step, and a step of returning the water recovered in the steam recovery step and the water liquefied in the liquefaction step to the system as drain water It is characterized by that.

  According to this configuration, the circulating water in the system and / or the chemical dissolved in the water can be recovered, so that the amount of chemical released into the atmosphere can be reduced. In addition, since the recovered water and / or chemicals dissolved in the water are reused, the amount of water and chemicals supplied to the system can be reduced.

  Moreover, when the said system | strain requires, you may have the decarboxylation process which removes the carbonic acid dissolved in the drain water mixed at the mixing process of the said structure.

  Since the carbon dioxide can be removed by providing the decarboxylation step, the pH of the water in the system can be maintained, and the amount of chemical replenishment for maintaining the pH can be reduced. Moreover, the performance fall or change of the water quality monitoring instrument by containing carbon dioxide can be suppressed.

  In order to achieve the above object, the present invention provides a recovery device for recovering chemicals from the water discharged outside the system, wherein the steam recovery means recovers the steam and drain water discharged from the system. And liquefying means for liquefying the steam recovered in the steam recovery process together with chemicals contained in the steam, mixing the drain water recovered in the steam recovery process and water liquefied in the liquefaction process And a step of returning the drain water recovered by the steam recovery means and the water liquefied by the liquefaction means to the system as drain water.

  According to this configuration, circulating water flowing in the system and / or chemicals dissolved in the water can be recovered, and the amount of chemicals released into the atmosphere can be reduced. Also, since water and / or chemicals dissolved in the water are reused, the amount of water and chemicals supplied to the system can be reduced.

  Further, since it can be easily installed in an existing plant equipped with the above system, it is also effective as a countermeasure against environmental problems such as atmospheric release of chemicals generated by the operation of the existing plant.

  When the system requires, it may have a decarboxylation means for removing carbonic acid dissolved in the drain water mixed in the mixing means having the above configuration.

  In the above configuration, the liquefying means may be a scrubber. Pure water may be supplied to the scrubber, or spray water used in the scrubber may be circulated.

  By using a scrubber as the liquefaction means, the chemical contained in the steam can be absorbed and recovered in the spray water. The liquefaction means is not limited to a scrubber, and a method that can recover a chemical from a gas containing the chemical can be widely adopted.

  In the above configuration, when a chemical is supplied to the system, a chemical dilution unit for diluting the chemical may be provided, and drain water mixed by the mixing unit may be used for the chemical dilution unit.

  In the above configuration, having a chemical separation means for separating the chemical from the water mixed by the mixing means, and reusing the chemical separated by the chemical separation means as a chemical to be replenished to the system It is good.

  According to the present invention, discharge of chemicals out of the system can be reduced, and adverse effects on the environment can be reduced.

  According to the present invention, in order to adjust the quality of the circulating water flowing in the system, the running cost can be kept low by reducing the amount of chemicals and the amount of water to be replenished.

  The best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows an example of a layout diagram using the system of collecting chemicals according to the present invention. The system shown in FIG. 1 is a secondary system of a nuclear power generation facility.

  The system SC shown in FIG. 1 is a plant that generates power by driving a turbine with steam generated by a steam generator SG, and includes a steam generator SG, a high-pressure turbine 1, and a moisture separation heater 2 (MSR). The low-pressure turbine 3, the condenser 4, the demineralization equipment 5, and the deaerator 6 are configured. These devices are arranged in the above order. Further, water circulating through the system SC (hereinafter referred to as circulating water) is circulated inside the system by a circulation pump (not shown).

  Circulating water inside the system SC is heated inside the steam generator SG to become steam. The steam (main steam) generated by the steam generator SG is sent to the high-pressure turbine 1. The main steam drives the high-pressure turbine 1 and the pressure also decreases. Most of the steam that has driven the high-pressure turbine 1 is sent to the moisture separation heater 2.

  Excess water is separated from the main steam by the moisture separator 2. The main steam discharged from the moisture separator / heater 2 is sent to the low-pressure turbine 3 to drive the low-pressure turbine 3. The steam that has driven the low-pressure turbine 3 flows into the condenser 4. The condenser 4 is also provided with a condensate recovery tank 44 for temporarily storing circulating water such as gland steam for sealing the turbine and seal water for the feed water pump.

  In the condenser 4, it cools with water (for example, seawater (not shown)), and condenses a vapor | steam as circulating water. The condensed circulating water is sent to the desalinator 5. In the condenser 4, the inside is evacuated and non-condensable gas or the like in the condensate is discharged out of the system as a condenser exhaust. The circulating water condensed in the condenser 4 removes impurities in the desalination facility 5 and separates dissolved gas in the deaerator 6, and then is sent to the steam generator SG to become steam again.

  In the above-mentioned system, for example, a secondary system of a nuclear power plant, chemicals are introduced into the circulating water flowing in the pipe in order to prevent corrosion of the pipe. As the chemical, ammonia (NH 3), hydrazine (N 2 H 4) and the like are used, but are not limited to these. By introducing a predetermined amount of chemicals into the circulating water flowing in the system, the pH of the circulating water can be raised. By increasing the pH, corrosion can be prevented and stress corrosion cracking can also be prevented. Moreover, the amount of dissolved oxygen in the circulating water can be reduced by adding hydrazine.

  FIG. 2 shows an example of a layout diagram of a condensate treatment system provided with the chemical recovery apparatus of the system according to the present invention. The condensate treatment system shown in FIG. 2 shows the recovery system of the steam contained in the exhaust gas from the secondary condenser 4 shown in FIG. 1 and the chemicals mixed in the steam.

  The condensate treatment system shown in FIG. 2 includes a condenser vacuum pump equipment 41 that is a steam recovery means for evacuating the condenser 4 to discharge non-condensable gas, and a scrubber equipment 42 that is a liquefaction means. And a system recovery facility 43 having a mixing means. The condenser 4 is also provided with a condensate recovery tank 44 for temporarily storing circulating water such as gland steam for sealing the turbine and seal water for the feed water pump. Further, if necessary, a decarbonation facility 441 for separating carbon dioxide may be provided on the downstream side of the condensate recovery tank 44.

  The condenser vacuum pump facility 41 serving as the steam recovery means includes an ejector 411, a pump 412, and a separator tank 413. The condenser vacuum pump equipment 41 can evacuate the condenser 4 under a high vacuum by a combination of the ejector 411 and the pump 412 to discharge non-condensable gas and the like in the condensate. The steam discharged from the condenser 4 flows into the separator tank 413 together with the ejector driving air. The air and steam flowing into the separator tank 413 are separated into water and air by gas-liquid separation in the separator tank 413.

  The air containing the vapor separated by the separator tank 413 is sucked by the suction fan 412 and sent to the scrubber equipment 42. The scrubber equipment 42 as liquefaction means is composed of a suction fan 421, a scrubber 422, a spray nozzle 423, and a drain pipe 424.

  The scrubber 422 is open to the atmosphere at the top, and has a spray nozzle 423 and a deodorant filling layer 426 inside. The air containing the chemical-containing vapor sent from the separator tank 413 enters the lower part of the scrubber 422 and contacts the spray water sprayed by the spray nozzle 423 while passing through the deodorant filling layer 426. The chemical-containing vapor is absorbed in the spray water, and the deodorant-packed layer 426 adsorbs chemicals in the vapor, removes most of the chemical-containing vapor in the air, and air containing almost no chemicals, Air is released from the top of the scrubber 422. The deodorant filling layer 426 is filled with an adsorbent such as activated carbon and adsorbs chemicals such as ammonia. The water that has absorbed the chemical-containing vapor is sent as drain water to the system recovery equipment 43 through the drain pipe 424.

  The drain pipe 417 of the separator tank 413 and the drain pipe 424 of the scrubber 422 of the condensate vacuum pump equipment 41 are connected to the recovery tank 431, and water from the separator tank 413 and scrubber 422 is supplied to the recovery tank 431 as drain water. It is collected and drain water is mixed in the tank. The system recovery equipment 43 includes a recovery tank 431 having the mixing means, a control valve 433 and a drain pipe 435 that constitute means for returning drain water to the system. A water level measuring device LT for checking the water level in the tank is attached to the recovery tank 431.

  The collection tank 431 is an air release tank. In addition, an overflow pipe 434 is provided at a predetermined position, and the overflow pipe 434 is connected to a drainage facility outside the system. A drain pipe 435 installed in the recovery tank 431 is connected to the condenser 4. Since the recovery tank 431 is an air release tank, while the condenser 4 is operated under high vacuum, the drain water from the recovery tank 431 is drained by the pressure difference between the recovery tank 431 and the condenser 4. It flows down to the condenser 4 through 435 and is returned to the system. The drain pipe 435 is provided with a control valve 433.

  The condenser 4 is provided with a water level measuring device LT, and can measure the water level of the condenser. Further, a water supply conductivity measuring device 430 is provided at a predetermined position of the system, and the conductivity of the circulating water can be measured. Examples of the measurement location include, but are not limited to, a steam generator SG inlet and a deaerator 6 inlet. By measuring the conductivity, the pH of the circulating water can be determined.

  Based on the water level of the condenser 4 measured by the water level measuring device LT, the conductivity of the circulating water measured by the water supply conductivity measuring device 430 and the water level of the recovery tank 431 measured by the water level measuring device LT. The valve opening of the control valve 433 is controlled. Further, if necessary, a decarbonation facility 441 for separating carbon dioxide may be provided on the downstream side of the condensate recovery tank 44.

  If the system requires, a decarboxylation facility 432 may be provided upstream of the control valve 433 as shown in FIG. In the devices (scrubber 422, recovery tank 431) where the drain water and the atmosphere come into contact and the devices in the system, carbon dioxide contained in the air dissolves in the drain water and the circulating water. Therefore, when the amount of dissolved carbon dioxide is large, the pH may be lowered. In such a case, it is possible to prevent the pH of the drain water from being lowered by removing carbon dioxide from the drain water by the decarbonation facility 432.

  FIG. 4 shows a flowchart of the chemical recovery method for the condensate treatment system according to the present invention. In the method for recovering chemicals in the condensate treatment system, first, ejector drive air is blown into the ejector 411, and noncondensable gas and steam are sucked from the condenser 4 (steam recovery step: step S1). In the separator tank 413, gas-liquid separation is performed to separate water and air (steam recovery process: step S2). The steam contained in the air exiting the separator tank 413 is recovered by the scrubber 422 (steam recovery process: step S3).

  The chemical-containing vapor collected in the scrubber 422 is absorbed into the spray water and liquefied (liquefaction process: step S4). The water recovered in the steam recovery step S2 and the water liquefied in the liquefaction step S4 are recovered and mixed in the recovery tank 431 as drain water (mixing step: step S5). The drain water mixed in the recovery tank 431 in the mixing step S5 is sent to the condenser 4 via the drain pipe 435 and returned to the system (step S6).

  When the system needs to be decarboxylated as shown in FIG. 5, as shown in the flowchart of the chemical recovery method of the condensate treatment system shown in FIG. 5, decarboxylation from the recovery tank 431 via the drain pipe 435 is performed. The data is sent to the facility 432 (step S7). The drain water separates carbon dioxide from the drain water in the decarboxylation facility 432 (decarbonation step: step S8). The drain water from which carbon dioxide has been separated in the decarbonation step S8 is sent to the condenser 4 and returned to the system (step S9).

  In this way, by collecting the chemical and water and returning them to the system, the concentration of the chemical released into the atmosphere can be reduced, and adverse effects on the environment can be reduced. In addition, since chemicals and water are reused, consumption of chemicals and water can be reduced, and costs can be reduced.

  6A and 6B are schematic layout views of other embodiments of the system recovery equipment. The system recovery equipment 43A shown in FIG. 6 (A) shows a layout view in which drain water recovered in the recovery tank 431 is sent to the existing condensate recovery tank 44, sent from here to the condenser 4 and returned to the system. ing. Other configurations are the same as those in the condensate treatment system shown in FIG. 2, and substantially the same parts are denoted by the same reference numerals. Moreover, the system | strain collection equipment 43B shown to FIG. 6 (B) has shown the layout which returns the drain water collect | recovered by the collection | recovery tank 431 to the upstream of the desalination equipment 5 of the said system | strain.

  In the system recovery equipment 43A shown in FIG. 6A, a control valve 433 is attached to a drain pipe 435A extending from the recovery tank 431, and is connected to the condensate recovery tank 44 shown in FIG. doing. Control based on the water level of the condenser 4 measured by the water level measuring device attached to the condenser 4, the conductivity of the circulating water measured by the feed water conductivity measuring device 430, and the water level of the recovery tank 431. The valve opening degree of the valve 433 is controlled. The installation location of the water supply conductivity measuring device 430 is, for example, the inlet of the steam generator SG or the inlet side of the deaerator 6, but is not limited thereto.

  In the case of the system recovery facility 43A for returning drain water to the condensate recovery tank 44, a decarbonation facility 441 is provided downstream of the condensate recovery tank 44, so that no new decarbonation facility is required for the system recovery facility 43A. Thus, the pressure loss of the drain pipe 435A can be reduced. In addition, the equipment can be simplified and the cost can be reduced.

  In the system recovery equipment 43B shown in FIG. 6B, a drain pipe 435B extending from the recovery tank 431 is connected to the upstream side of the desalination equipment 5 constituting the system (secondary circulating water system). Other configurations are the same as those in the condensate treatment system shown in FIG. 2, and substantially the same parts are denoted by the same reference numerals.

  In the system recovery equipment 43B shown in FIG. 6B, a control valve 433 is attached to a drain pipe 435B extending from the recovery tank 431, and the condensate demineralization equipment 5 shown in FIG. Connected. The control valve 433 is based on the water level of the condenser 4 measured by a water level measuring device attached to the condenser 4, the conductivity of circulating water measured by a feed water conductivity measuring device, and the water level of the recovery tank 431. To control the valve opening. The conductivity measurement place is the same as that of the system recovery facility 43A.

  In the case of the system recovery equipment 43B, since the desalination equipment 5 also has a function of removing carbon dioxide in the system circulation water, no decarbonation equipment is arranged as in the system recovery equipment 43A shown in FIG. 6 (A). The pressure loss of the drain pipe 435B can be reduced. In addition, the equipment can be simplified and the cost can be reduced.

  FIG. 7 shows another schematic layout of the condensate treatment system equipped with the chemical recovery apparatus according to the present invention. The chemical recovery apparatus shown in FIG. 7 has a circulation circuit for circulating spray water in the scrubber 422C of the scrubber equipment 42C. Further, the drain water in the recovery tank 431 is sent via the drain pipe 435C to the dilution water tank 7 for diluting the chemical to be replenished and used as dilution water. Further, the drain water in the separator tank 413 is sent to the scrubber 422 via the drain pipe 417C. Other configurations are the same as those in the chemical recovery apparatus of the condensate treatment system shown in FIG. 2, and substantially the same parts are denoted by the same reference numerals.

  The scrubber 422C shown in FIG. 7 includes a spray water circulation system including a pump 425 and a circulation pipe 428, and the circulation pipe 428 is connected to the spray nozzle 423. By recirculating the spray water around the scrubber 422C, the gas-liquid contact efficiency between the air and the spray water inside the scrubber 422C can be increased, and the absorption efficiency of the chemical-containing vapor can be increased. As a supply source of spray water, it can be replenished separately from a pure water supply system. The pure water supply system includes a pure water pipe 427 and replenishes pure water according to the chemical concentration in the spray water or the circulation amount of the spray water.

  The scrubber 422C is attached with a water level measuring device LT, and the drain pipe 424C is provided with a control valve 429. The control valve 429 is controlled based on the water level of the scrubber 422C detected by the water level measuring device LT, and the amount of drain water sent to the recovery tank 431 is adjusted.

  The drain water recovered in the recovery tank 431 of the system recovery equipment 43C is sent to the dilution water tank 7 for diluting the supplementary chemicals via the drain pipe 435C and can be used as dilution water. In addition, a facility for extracting only the chemical from the drain water can be provided, and the collected chemical can be reused. In addition, the recovery efficiency of water and chemicals can be increased, the amount of pure water and chemicals to be replenished can be reduced, the generation of surplus water and the like can be suppressed as much as possible, and the running cost can be suppressed. In the above description, the use as dilution water for the dilution water tank 7 is described. However, as shown in FIGS. It may be returned to increase the recovery efficiency of the condensate.

  FIG. 8 is a layout view in which drain water generated in the separator tank 413 and the scrubber 422 is recovered in the condensate recovery tank 44. Although the drain pipes 417 and 424 are not connected to the recovery tank 431 but are connected to the condensate recovery tank 44 and the system recovery equipment 43 is omitted, the other configurations are the same as those in FIG. Therefore, the same number can be used. A control valve 433 is mounted on the downstream side of the condensate recovery tank 44, and is controlled by the water level of the condenser 4 measured by the water level measuring device LT to restrict the flow of drain water to the condenser 4. ing. By adopting such a configuration, the system recovery equipment 43 becomes unnecessary, and a significant cost reduction can be achieved.

  In the above embodiment, a condenser exhaust system is described as an example of a target facility that can solve environmental problems and improve running costs by collecting steam that has been conventionally released into the atmosphere. However, the present invention is not limited to this, and can be widely used for exhaust gas of steam such as a deaerator.

  Further, in each of the above embodiments, as an example of providing a chemical recovery method of the system and a recovery device using the method, a secondary condensate treatment system of a nuclear power plant is described as an example. However, the present invention is not limited to this, and can be widely used in plants, piping, systems, etc., in which chemicals are injected into the system and steam is discharged to the atmosphere.

It is an arrangement plan of an example using the medicine recovery device of the system concerning the present invention. It is an arrangement plan of an example of a condensate treatment system provided with the chemical recovery device of the system concerning the present invention. It is a layout view of another embodiment of the condensate treatment system provided with the chemical recovery apparatus of the system according to the present invention. It is a flowchart of an example of the chemical | medical agent collection | recovery method of the type | system | group concerning this invention. It is a flowchart of the other example of the chemical | medical agent collection | recovery method of the type | system | group concerning this invention. FIG. (A) is a schematic layout of another example of the system recovery facility, and FIG. (B) is a schematic layout of yet another example of the system recovery facility. It is a schematic layout of another example of a condensate treatment system equipped with a chemical recovery device of the system according to the present invention. FIG. 6 is a schematic layout diagram of still another example of a condensate treatment system including a chemical recovery device according to the present invention.

Explanation of symbols

1 High-pressure turbine 2 Moisture separation heater (MSR)
3 Low pressure turbine 4 Condenser 41 Condenser vacuum pump equipment 411 Ejector 412 Pump 413 Separator tank 417 Drain pipe 42 Scrubber equipment 421 Suction fan 422 Scrubber 423 Spray nozzle 424 Drain pipe 425 Pump 426 Deodorant filling layer 427 Pure water pipe 428 Circulation piping 429 Control valve 43 System recovery facility 430 Water supply conductivity measuring device 431 Recovery tank 432 Decarbonation facility 433 Control valve 434 Overflow piping 435 Drain piping 44 Condensate recovery tank 441 Decarbonation facility 5 Desalination facility 6 Deaerator 7 Dilution water tank SG Steam generator

Claims (9)

A recovery method for recovering chemicals from the water discharged outside the system among the circulating water flowing in the piping provided in the system,
A steam recovery step of recovering steam and drain water discharged from the system;
A liquefaction step of liquefying the vapor recovered in the vapor recovery step together with a chemical contained in the vapor;
A mixing step of mixing the drain water recovered in the steam recovery step and the water liquefied in the liquefaction step;
And a step of returning the water mixed in the mixing step to the system as drain water.   The method for recovering chemicals of a system according to claim 1, further comprising a decarboxylation step of removing carbonic acid dissolved in the water mixed in the mixing step. Of the circulating water flowing in the piping provided in the system, a recovery device that recovers chemicals from the water discharged outside the system,
Steam recovery means for recovering steam and drain water discharged from the system;
Liquefying means for liquefying the steam recovered in the steam recovery step together with chemicals contained in the steam;
A mixing means for mixing the drain water recovered in the steam recovery step and the drain water liquefied in the liquefaction step;
A system for collecting chemicals in a system, comprising means for returning water mixed by the mixing means to the system as drain water.   The system for recovering chemicals of a system according to claim 3, further comprising a decarboxylation means for removing carbonic acid dissolved in the water mixed by the mixing means.   The system for collecting chemicals in a system according to claim 3 or 4, wherein the liquefying means is a scrubber.   6. The system chemical recovery apparatus according to claim 5, wherein pure water is supplied to the scrubber.   The system of claim 5 or 6, wherein the scrubber water is circulated. Having a chemical dilution means for diluting the chemical when the chemical is introduced into the system;
The system for collecting chemicals in a system according to any one of claims 3 to 7, wherein the water mixed by the mixing means is introduced into the chemical dilution means. Having a chemical separation means for separating the chemical from the water mixed by the mixing means,
The system for collecting chemicals in a system according to any one of claims 3 to 7, wherein the chemicals separated by the chemical separation means are reused as chemicals to be charged into the system.

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