JP2006231197A - Water quality control method based on heater drain iron concentration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water quality control method based on heater drain iron concentration capable of controlling the iron concentration of an extremely low concentration at a boiler inlet even in the analysis sensitivity of the conventional iron concentration measuring device. <P>SOLUTION: In the water quality control method, a first reference value of iron concentration in feed water at the boiler 31 inlet is decided and a dilution contribution of a heater 7 arranged on the downstream side of a boiler 31 is determined with respect to the first reference value. By multiplying a reciprocal of the dilution contribution to the first reference value, a second reference value of iron concentration in a drain of the heater 7 is determined. The iron concentration in the drain of the heater 7 is measured and the iron concentration in the feed water is monitored so that the measured iron concentration becomes the second reference value or less. Thereby, the iron concentration at the boiler 31 inlet is controlled to be the first reference value or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water quality management method based on heater drain iron concentration, and more particularly to a water quality management method capable of managing iron concentration in boiler feed water by monitoring iron concentration in a heater drain of a thermal power plant or the like. .

  Conventionally, in thermal power and nuclear power plants, generated high-temperature and high-pressure steam is supplied to a turbine, and the turbine is driven by this steam to generate power. The steam after driving the turbine is cooled by the condenser and returned to the water state, then heated again, supplied to the boiler, the nuclear reactor, and the steam generator, and reused.

  As an exhaust gas boiler in a thermal power plant, one having a configuration as shown in FIG. 6 is known (see Patent Document 1). The exhaust gas boiler 100 includes a high-pressure turbine 1, an intermediate-pressure turbine 2, and a low-pressure turbine 3, and supplies make-up water from a make-up water tank 4 disposed downstream of the low-pressure turbine 3 from a condenser 30. It is circulated as water supply with condensate.

  A circulation path in which makeup water and condensate are mixed and circulated, that is, circulation system A is an economizer (a economizer) through an ejector 5, a low pressure heater 6, 7, a deaerator 8, a storage tank 9, and a high pressure heater 10. ) It is comprised by the system which supplies water to 11. Then, after water is supplied to the economizer 11, the economizer 11 is introduced into the high-pressure turbine 1 through the superheater 12. Further, the fluid exiting the high-pressure turbine 1 flows through the reheater 13 through the intermediate-pressure turbine 2 and the low-pressure turbine 3 in this order.

  By the way, about the feed water which flows through such a circulation system A, ie, the mixed water of condensate and make-up water, volatility by adding pH adjuster which consists of alkalis, such as ammonia water or a volatile amine, to this is added. Material treatment is performed. By such volatile substance treatment, it is specified that the pH value of the feed water is adjusted to 8.5 to 9.6, particularly at the inlet position B of the economizer 11, and a pH meter is provided at the inlet position B. 14 is arranged to detect the pH value here.

  Further, the feed water to the boiler 31 contains impurities mainly composed of iron oxide, and these impurities gradually adhere to the inner surface of the heat transfer tube of the boiler 31, and this deposit increases the differential pressure of the boiler 31. There is a case. As a result, the boiler 31 and the piping may be damaged. For this reason, by installing an iron-proof filter in the flow path through which the condensate of the water supply system flows, impurities mainly composed of iron oxide are removed (see Patent Document 2). In addition, various filters such as cartridges, hollow fibers, and electromagnetic filters have been proposed as methods for removing iron. However, since the iron oxide particles are extremely fine, the impurity removal performance of these filters is unstable and practical. (See Patent Document 3). Furthermore, the JIS standard defines that the iron concentration in the feed water at the inlet of the boiler 31 is 10 μg / l (ppb) or less (Non-Patent Document 1).

JP 2002-349804 A JP 2001-17983 A Japanese Patent Laid-Open No. 11-57416 JIS B8233 (Boiler water supply and boiler water quality), issued on November 20, 1999

  However, even if the water quality is controlled so that the iron concentration in the feed water at the inlet of the boiler 31 is 10 μg / l or less, the scale may adhere to the evaporation pipe or the like. Due to this scale, there is a possibility of causing a temperature rise or a breakage accident in the pipe member or the like, and it is necessary to further reduce the iron concentration standard in the feed water at the inlet of the boiler 31. However, the analytical sensitivity of the concentration measuring device for measuring the iron concentration is currently limited to about 5 μg / l, and it is difficult to control the water quality by directly measuring the iron concentration below 5 μg / l. was there.

  The present invention has been made in view of the above, and a water quality management method using a heater drain iron concentration capable of managing an extremely low iron concentration at the boiler inlet even in the analysis sensitivity of the current iron concentration measuring apparatus. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, the water quality management method according to the heater drain iron concentration according to claim 1 of the present invention is a heater drain iron concentration that monitors the iron concentration in the water supply system of a thermal power plant. A water quality management method according to claim 1, wherein a first reference value of iron concentration in feed water at a boiler inlet is determined, and a dilution contribution ratio of a heater disposed downstream of the boiler with respect to the first reference value A second reference value of the iron concentration at the drain of the heater is obtained by multiplying the first reference value by the reciprocal of the dilution contribution ratio, and the iron concentration at the drain of the heater is measured and measured. The iron concentration at the inlet of the boiler is controlled to be equal to or lower than the first reference value by monitoring the iron concentration in the feed water so that the iron concentration is equal to or lower than the second reference value.

  Moreover, in the water quality management method according to the heater drain iron concentration according to claim 2 of the present invention, the first reference value is characterized in that the iron concentration is in the range of 0.5 to 2 μg / l. To do.

  Moreover, in the water quality management method by heater drain iron concentration of Claim 3 of this invention, the dilution contribution rate exists in the range of 10-20%, It is characterized by the above-mentioned.

  Moreover, in the water quality management method by heater drain iron concentration of Claim 4 of this invention, the measurement of the iron concentration in the drain of a heater is performed using a turbidimeter.

  Moreover, in the water quality management method by heater drain iron concentration of Claim 5 of this invention, the measurement of the iron concentration in the drain of a heater is performed using a filter apparatus, It is characterized by the above-mentioned.

  In the water quality management method according to the heater drain iron concentration according to claim 6 of the present invention, a plurality of filter devices are provided as filter devices, and the plurality of filter devices are sequentially used.

  Moreover, in the water quality control method by heater drain iron concentration of Claim 7 of this invention, the result of an iron concentration measurement is calculated | required from the integrated value of iron, It is characterized by the above-mentioned.

  Moreover, in the water quality management method by heater drain iron concentration of Claim 8 of this invention, when the iron concentration in feed water is monitored and the measured iron concentration exceeds the said 2nd reference value, Is characterized by further comprising adding a pH adjuster to the water supply.

  The water quality management method according to the heater drain iron concentration according to the present invention is obtained by multiplying the first reference value of the iron concentration in the feed water at the inlet of the boiler by the reciprocal of the dilution contribution ratio of the heater to thereby determine the iron concentration in the heater drain. The second reference value is determined, and the higher reference value of the second reference value and the iron concentration measurement value of the heater drain are monitored, so that extremely low concentration iron at the inlet of the boiler, which is difficult to directly measure, is monitored. There is an effect that it can be easily managed.

  Hereinafter, an embodiment of a water quality management method based on heater drain iron concentration according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. Moreover, in each figure, the same code | symbol has shown the same or an equivalent part.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram showing an exhaust gas boiler of a thermal power plant to which a water quality management method based on heater drain iron concentration according to Embodiment 1 of the present invention is applied. In FIG. 1, an exhaust gas boiler 100 </ b> A has a high pressure turbine 1, an intermediate pressure turbine 2, and a low pressure turbine 3, and supplies makeup water from a makeup water tank 4 disposed downstream of the low pressure turbine 3 to a condenser. It is circulated as water supply with condensate from 30.

  A circulation path in which makeup water and condensate from the makeup water tank 4 are mixed and circulated, that is, the circulation system A includes an ejector 5, a low pressure heater 6, 7, a deaerator 8, a storage tank 9, and a high pressure heater 10. It is comprised by the system which supplies water to economizer (carving economizer) 11 via. Then, after water is supplied to the economizer 11, the economizer 11 is introduced into the high-pressure turbine 1 through the superheater 12. Further, the fluid exiting the high-pressure turbine 1 flows through the reheater 13 through the intermediate-pressure turbine 2 and the low-pressure turbine 3 in this order.

  Regarding the feed water flowing through the circulation system A, that is, the mixed water of condensate and make-up water, a volatile substance treatment is performed by adding a pH adjuster made of alkali water such as ammonia water or volatile amine thereto. Is made. By such volatile substance treatment, it is specified that the pH value of the feed water is adjusted to 8.5 to 9.6, particularly at the inlet position B of the economizer 11, and a pH meter is provided at the inlet position B. 14 is arranged to detect the pH value here.

  A turbidity meter 40 is provided on the outlet side of the drain tank 32 of the low-pressure heater 6 so that the iron concentration in the feed water can be measured as will be described later. Further, the measurement result of the iron concentration in the turbidimeter 40 is sent to the pH adjustment control unit 41. The pH adjustment control unit 41 performs control to reduce the iron concentration in the water supply by adding a pH adjusting agent 42 such as ammonia to the water supply as necessary and adjusting the pH.

  The feed water to the boiler 31 contains impurities mainly composed of iron oxide, and these impurities gradually adhere to the inner surface of the heat transfer tube of the boiler 31, and the differential pressure of the boiler 31 increases due to this deposit. There is. This deposit is a scale mainly composed of iron oxide. In order to prevent such a scale from adhering to the pipe, the iron concentration in the feed water at the inlet of the boiler 31 is 10 μg / l (ppb) or less. This is defined in the JIS standard described above. However, even if the water quality is controlled so that the iron concentration in the feed water at the inlet of the boiler 31 is 10 μg / l or less, the scale may adhere to the evaporation pipe or the like.

  The present invention provides a turbidimeter 40 as an iron concentration measuring device for the iron concentration of a water supply system in order to manage the water quality of an extremely low concentration of iron that is difficult to directly measure even with the analytical sensitivity of the current iron concentration measuring device. Is provided on the outlet side of the drain tank 32 of the low-pressure heater 6 having a high contribution rate. In the present invention, the iron concentration in the feed water at the inlet of the boiler 31 is set to 0.5 to 2 μg / l, preferably 1 μg / l or less as the first reference value. By adopting such a first reference value, scale in the water supply can be sufficiently prevented.

  In the present invention, a turbidimeter 40 is provided on the outlet side of the drain tank 32 of the low-pressure heater 6 as an iron concentration measuring device. In the drain tank 32 of the low-pressure heater 6, there is a dilution contribution ratio of about 10% in terms of the flow rate ratio with respect to the main water supply system at the inlet of the boiler 31. Here, the “dilution contribution ratio” is a ratio in which the feed water and the condensate are mixed in the feed water system, and finally the dilution ratio with respect to the feed water at the inlet of the boiler 31 is determined. This dilution contribution rate varies depending on the actual scale of the thermal power plant, the capacity of each device, the flow rate of water supply and condensate, and the like, and is determined in advance for each thermal power plant. The range of the dilution contribution rate is, for example, 10 to 20%. For example, when the dilution contribution ratio is 10%, the iron concentration in the feed water at the inlet of the boiler 31 becomes 1/10 of the iron concentration at the outlet side of the drain tank 32 of the low-pressure heater 6 by being diluted.

  Therefore, by multiplying the above-mentioned first reference value by the reciprocal of the dilution contribution rate, the reference value of the iron concentration on the outlet side of the drain tank 32 of the low-pressure heater 6 can be obtained, and this reference value is obtained as the second reference value. Value. That is, as an example, assuming that the first reference value of the iron concentration in the feed water at the inlet of the boiler 31 is 1 μg / l and the dilution contribution rate is 10% (hereinafter the same), the drain tank of the low-pressure heater 6 The second reference value of the iron concentration of the feed water at 32 is 10 μg / l. Therefore, by measuring the iron concentration at the outlet side of the drain tank 32 of the low-pressure heater 6 and monitoring the measured iron concentration to be equal to or lower than the second reference value, the iron concentration in the feed water at the boiler 31 inlet is changed to the first value. It becomes possible to manage below the reference value of 1.

  Next, in the present invention, the turbidimeter 40 is used as an iron concentration measuring device. Regarding the measurement of the iron concentration by the turbidimeter 40, as shown in an example in FIG. 2, a correlation is recognized between the index value (ppm) of the turbidimeter and the iron concentration (μg / l). Therefore, the iron concentration can be managed by measuring the turbidity. FIG. 3 is a diagram showing the change in turbidity over time at the drain tank 32 outlet side (graph A) and the economizer 11 inlet (graph B) of the low-pressure heater 6. As is apparent from FIG. 3, the drain tank 32 outlet side (graph A) of the low-pressure heater 6 shows higher turbidity than the economizer 11 inlet (graph B), and the iron concentration is also high. This is due to the dilution contribution rate described above.

  Moreover, as shown in the graph A, the turbidity may increase very much even within one day. Therefore, rather than measuring turbidity for a certain period of time, the measured value measured over a long period of time is managed as an integrated value, or the maximum or average value of turbidity is used to monitor the iron concentration. It is desirable. For example, when water quality management is performed with the integrated value of turbidity, the iron concentration in the feed water at the inlet of the boiler 31 is 1 μg / l or less by making the iron concentration in the turbidimeter 40 an average of 10 μg / l or less on a daily basis. It can be. By using the integrated value of turbidity, the measurement error can be minimized even when the turbidity increases rapidly in a certain time. In each thermal power plant, it is necessary to grasp the correlation between turbidity and iron concentration in advance.

  As described above, the measurement result of the iron concentration of the feed water at the outlet side of the drain tank 32 of the low-pressure heater 6 is sent to the pH adjustment control unit 41. If the iron concentration exceeds 10 μg / l, the pH adjustment control unit 41 performs control to add a pH adjusting agent 42, for example, ammonia to the feed water as necessary. By adjusting the pH of the feed water with the pH adjuster 42, control is performed to reduce the iron concentration in the feed water. That is, by elevating the pH of the feed water, elution of iron ions from piping and the like can be suppressed, and the iron concentration in the feed water can be reduced.

  By using the pH adjustment control unit 41, the iron concentration in the water supply can be automatically maintained at the second reference value. In addition, it is also possible to add the pH adjusting agent 42 to the water supply manually without using the pH adjustment control unit 41.

(Embodiment 2)
FIG. 4 is a schematic configuration diagram showing an exhaust gas boiler of a thermal power plant to which the water quality management method based on the heater drain iron concentration according to Embodiment 2 of the present invention is applied. In the second embodiment, a filter device 50 for measuring iron concentration is provided instead of the turbidimeter 40 in the first embodiment.

  In FIG. 4, a filter device 50 for measuring iron concentration is provided on the outlet side of the drain tank 32 of the low-pressure heater 6. By measuring the iron concentration in the water supply at the outlet side of the drain tank 32, water quality management can be performed as in the first embodiment. For example, the water supply can be passed through the filter device 50 for 24 hours, and then the filter device 50 is removed from the water supply channel, and the deposits remaining on the filter device 50 are dissolved with an acid solution, and the iron concentration can be quantitatively analyzed according to a conventional method. . At this time, it is desirable to use the integrated value for the evaluation of the iron concentration. For example, 10 μg / l as an average value for 24 hours can be used as the second reference value of the iron concentration at the outlet side of the drain tank 32. . By monitoring such a second reference value, the iron concentration in the feed water at the inlet of the boiler 31 can be managed to be 1 μg / l or less, which is the first reference value, based on the dilution contribution rate described above.

  FIGS. 5A and 5B are schematic diagrams illustrating a case where two filter devices are used and these are used by switching. In each of the following valves, a white valve is open and a black valve is closed. 5A, the water supply from the drain tank 32 (see FIG. 4) of the low-pressure heater 6 is performed by switching the first valve 61 and the second valve 62 to switch the first filter device 51 or the second filter 62. Guided to the filter device 52. That is, by opening the first valve 61, the water supply passes through the first filter device 51 and is guided to the low-pressure heater 7 (see FIG. 4).

  At this time, the pump 65 is operated, and the acid solution from the acid solution tank 53 can be led to the used second filter device 52 to perform back washing. The waste liquid that has undergone the reverse cleaning is discarded in the waste liquid reservoir 54. Next, the iron concentration in the deposit adhering to the first filter device 51 is quantitatively analyzed. Thereafter, as shown in FIG. 5B, by opening the second valve 62, the water supply passes through the second filter device 52 that has been cleaned, and is guided to the low-pressure heater 7 (see FIG. 4). . At this time, as in FIG. 5A, the pump 65 is operated, and the acid solution from the acid solution tank 53 can be led to the used second filter device 51 to perform back washing. As described above, by switching and using two filter devices, it is possible to monitor the iron concentration without removing the filter device from the pipe. Note that the number of filter devices is not limited to two, and a plurality of filter devices may be sequentially used by adding filter devices having configurations as shown in FIGS. 5A and 5B.

  In the first and second embodiments described above, the case where the iron concentration in the feed water at the outlet side of the drain tank 32 is measured using the turbidimeter 40 or the filter device 50, respectively, is limited to the present invention. For example, the iron concentration may be monitored using a laser particle monitor. Moreover, the case where the iron concentration was measured on the outlet side of the drain tank 32 of the low-pressure heater 6 was described. However, the present invention is not limited to this, and it is also possible to measure the iron concentration at other locations such as the low-pressure heater 7 and the high-pressure heater 8 by obtaining the dilution contribution ratio in advance.

  As described above, the water quality management method according to the heater drain iron concentration according to the present invention is useful for preventing the occurrence of scale in piping in a thermal power plant or the like, and is particularly difficult to measure directly. It is suitable for easily managing the iron concentration at the inlet of a low-concentration boiler.

It is a schematic block diagram which shows the exhaust gas boiler of the thermal power plant to which the water quality management method by heater drain iron concentration by Embodiment 1 of this invention is applied. It is a diagram which shows the relationship between the iron concentration in feed water, and a turbidimeter instruction value. It is a diagram which shows the time-dependent change of the turbidity in the drain tank 32 exit side (graph A) of a low voltage | pressure heater, and an economizer entrance (graph B). It is a schematic block diagram which shows the exhaust gas boiler of the thermal power plant to which the water quality management method by the heater drain iron concentration by Embodiment 2 of this invention is applied. It is a schematic block diagram of piping in the case of using two filter apparatuses. It is a schematic block diagram of piping in the case of using two filter apparatuses. It is a schematic block diagram which shows the exhaust gas boiler of the conventional thermal power plant.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High pressure turbine 2 Medium pressure turbine 3 Low pressure turbine 4 Supply water tank 5 Ejector 6 Low pressure heater 7 Low pressure heater 8 Deaerator 9 Storage tank 10 High pressure heater 11 Economizer 12 Superheater 13 Reheater 14 pH meter 20 pH meter 30 Condenser 31 Boiler 32 Drain tank 40 Turbidimeter 41 pH adjustment controller 42 pH adjuster 50 Filter device 51 First filter device 52 Second filter device 53 Acid solution tank 54 Waste water reservoir 61 First valve 62 First valve 62 Second valve 63 Third valve 64 Fourth valve 100A Exhaust gas boiler 100B Exhaust gas boiler

Claims (8)

It is a water quality management method by heater drain iron concentration that monitors the iron concentration in the water supply system of a thermal power plant,
A first reference value of iron concentration in feed water at the inlet of the boiler is determined, a dilution contribution rate of a heater disposed downstream of the boiler is obtained with respect to the first reference value, and the first reference value is obtained. By multiplying the value by the reciprocal of the dilution contribution rate, a second reference value of the iron concentration at the drain of the heater is obtained, the iron concentration at the drain of the heater is measured, and the measured iron concentration is the second A water quality management method based on a heater drain iron concentration, wherein the iron concentration at the inlet of the boiler is controlled to be equal to or lower than a first reference value by monitoring the iron concentration in the feed water so as to be equal to or lower than a reference value.   2. The water quality management method according to claim 1, wherein the first reference value has an iron concentration in a range of 0.5 to 2 μg / l.   The water dilution management method according to claim 1 or 2, wherein the dilution contribution ratio is in a range of 10 to 20%.   The water concentration management according to any one of claims 1 to 3, wherein the iron concentration in the drain of the heater is measured using a turbidimeter. Method.   The water quality management method according to any one of claims 1 to 3, wherein the iron concentration in the drain of the heater is measured using a filter device. .   The water quality management method according to claim 5, wherein a plurality of filter devices are provided as the filter device, and the plurality of filter devices are sequentially used.   The water quality management method according to any one of claims 4 to 6, wherein the iron concentration measurement result is obtained from an integrated value of iron.   The method further comprises monitoring the iron concentration in the water supply and adding a pH adjuster to the water supply when the measured iron concentration exceeds the second reference value. The water quality management method by the heater drain iron concentration of any one of Claims 7.

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