TWI586887B - Turbine equipment and heater drainage of water treatment methods - Google Patents

Description

Turbine equipment and heater drainage water treatment method

This invention relates to turbine equipment, and more particularly to turbine equipment having a mechanism for filtering the heater drain and allowing the water supply to be recovered. Furthermore, the present invention relates to a water treatment method for heater drainage of the turbine equipment.

In a thermal power plant, a nuclear power plant, or the like, the generated high-temperature and high-pressure steam is supplied to a turbine, and the steam is used to drive the turbine to generate electricity. The steam that has been driven by the turbine is returned to the water after being cooled by the rehydrator, and then heated and supplied to the boiler, the atomic furnace, and the steam generator, and can be reused.

In large-scale power generation equipment, most of the cases use high-pressure, low-pressure tandem multi-stage steam turbines. The turbine is rotated to rotate the generator by using high temperature and high pressure steam generated in a boiler or steam generator. During the expansion of the vapor, the entropy is reduced to become a wet vapor. In the state of wet steam, since the energy conversion efficiency of the turbine is lowered, it is necessary to perform pumping in a predetermined section of the turbine. The pumping retains a great energy including latent heat of vaporization. Therefore, based on the purpose of heat recovery, the pumping of the vapor extracted from a predetermined section of the turbine is introduced into the heat exchanger to perform indirect heat exchange with the reclaimed water. This is followed by heating of the rehydration. The heat exchanger heated by the high pressure turbine is referred to as a high pressure heater, and the heat exchanger heated by the low pressure turbine is referred to as a low pressure heater.

Pumping from low-pressure turbines, temperature and pressure are more than The high-pressure turbine has low pumping, so after the re-watering leaves the condenser, it is circulated through the low-pressure heater through the degasser, then the high-pressure heater, and the economizer (economizer). In addition, the high-pressure heater drain and the low-pressure heater drain generated by the high-pressure heater and the low-pressure heater are respectively introduced into the rehydration main pipe, and are recycled as the boiler water supply.

In the boiler, in order to prevent damage caused by corrosion of the heat transfer tube, water quality management of the water supply is very important. Conventionally, in order to maintain the pH of the boiler water supply alkaline, a nitrogen compound such as a volatile amine, hydrazine, or ammonia is used. Further, these pH adjusters also function as a reducing agent to form an oxide film of black magnetite (Fe ₃ O ₄ ) on the surface of the boiler tube to exhibit an anti-corrosion effect. This boiler water treatment method is called AVT (All Volatile Treatment) and has long been used as a benchmark for boiler water quality management.

If the magnetite coating is too thick, the heat transfer coefficient will decrease. this In addition, magnetite forms a corrugated oxide film on the surface of the boiler tube, which increases the water resistance of the boiler water, resulting in a decrease in total energy conversion efficiency. Therefore, in the power generation equipment, chemical cleaning is performed during the regular repair period every three to four years to suppress excessive growth of the magnetite oxide film, prevent corrosion of the boiler tube, and reduce heat transfer resistance and water resistance. .

About 20 years ago, boiler water quality management technology called CWT (Combined Water Treatment) was popularized in Europe and America. In this method, the water mixture obtained by mixing the reconstituted water and the makeup water is treated by a deaerator, and oxygen, an inert gas or the like is removed, and pure oxygen is added to control the oxygen concentration in the water supply to about 5 ppb. In the early stage of the transfer to CWT, the combined treatment of oxygen and ammonia was used as the mainstream. In recent years, oxygen-only treatment with oxygen has become the mainstream. With this oxygen treatment, a hematite (Fe ₂ O ₃ ) layer having a higher degree of oxidation than magnetite is formed on the surface of the boiler tube. The hematite layer is very dense and its surface is smoother than the magnetite layer, which does not increase the water resistance. In addition, the hematite layer is chemically stable and has a high anti-corrosion effect, which reduces the frequency of chemical cleaning compared to AVT. In this way, even in large thermal power plants in Japan, boilers treated with CWT have also increased.

As described above, the rehydration water sent from the turbine is heated by a water supply heater that uses suction as a heat source. The drainage from the water supply heater merges with the rehydration water and is recycled as a water supply.

For the turbine equipment after CWT treatment, the total iron concentration contained in the rehydration, high-pressure heater drainage and low-pressure heater drainage is measured. The iron concentration of the low-pressure heater drainage is significantly higher than other waters. The reason for the increase in iron concentration is the low pressure heater drain.

For the filter element unit in which the membrane filter elements having the effective filter pore diameters of 3, 1, 0.45, 0.2, and 0.1 μm are arranged in series, the low-pressure heater drain of the turbine equipment after the CWT treatment is passed through, and the iron oxide scale is found. More than 90% is captured by a membrane filter with an effective filter pore size of 3 μm. The filter element aperture of the present invention (also referred to as: effective filter aperture) It can express the absolute filtration pore diameter which removes the particle of the particle diameter of the object by the probability of 99% or more.

As a result of observation with an electron microscope, the iron oxide fine particles were needle crystals having a very large ratio (shape ratio) of the particle length to the cross-sectional diameter. After separating the iron oxide fine particles, the morphology of the particles was determined by Mesberg spectrometry, and the composite oxides of α-Fe ₂ O ₃ , γ-Fe ₂ O ₃ , and α-FeOOH accounted for more than 80%. It is formed into needle crystals.

In the CWT treatment, the dissolved oxygen in the water supply is consumed by the formation of the oxide film in the process of passing through the boiler tube, and the oxygen dissolution concentration is gradually lowered. The high temperature and high pressure steam generated by the boiler gradually decreases in temperature and pressure as it expands in the turbine. In the low pressure heater, the saturation temperature is below 130 °C. In the low-pressure heater, due to the condensation of the low-pressure turbine, the heater becomes a developed turbulent flow. Therefore, it is difficult to form a stable hematite film on the heat transfer surface of the low-pressure heater. Further, since the temperature of the low-pressure heater is lower than that of the boiler tube, the oxidation reaction rate of the heat transfer tube base material becomes small, and formation of the hematite oxide film becomes more difficult. As described above, in the heat transfer surface of the low-pressure heater, it is difficult to sufficiently progress the formation of the hematite oxide film from the viewpoint of physical properties and chemical properties. Therefore, iron from the base material is dissolved (corroded). This form of corrosion is called FAC (Flow Accelerated Corrosion).

The iron oxide fine particles in the low-pressure heater drainage are oxidized in a large amount of drainage, and are precipitated as hematite or goethite (FeOOH) particles having low solubility and stable chemical properties.

For the purpose of removing iron oxide particles from the boiler water supply Techniques have been proposed (Patent Documents 1 to 3).

It is described in Patent Document 1 that the use of rehydration has The membrane having a pore size of 0.01 to 0.3 μm was filtered. Patent Document 2 discloses that a reconstituted water is filtered using a membrane having a pore size of 1 μm. However, Patent Document 1 and 2 do not describe that the drainage of the low-pressure heater is subjected to filtration treatment.

It is described in Patent Document 3 that the low pressure heater is drained and filtered. The water treatment method for the heater drain water that is sent to the turbine equipment of the water supply system and the turbine equipment. In Patent Document 3, when the iron concentration of the drainage exceeds a predetermined concentration, the drainage is discharged to the outside of the system, and only when the iron concentration is low, the filter element is used for iron removal and used as a part of the boiler water supply. This is because, in the case of the drainage, the fine iron which cannot be filtered is contained, and in addition to the case where the iron concentration is equal to or lower than the predetermined concentration, the iron which exceeds the use limit of the boiler water supply is contained even if the filtration treatment is performed. According to the structure of the patent document 3, in addition to the problem of enlargement of equipment, since the discharge|cleaning of the drainage|draining of the water of a heater is low, and the discharge of the water of the heaters is low, and the discharge amount of the water is increased.

[Patent Document 1] Japanese Patent Laid-Open No. 9-206567

[Patent Document 2] Japanese Patent Laid-Open No. 2000-218110

[Patent Document 3] Japan Special Open 2008-25922

The object of the present invention is to provide a turbine device and The water treatment method of the heater drain of the turbine equipment can efficiently remove the scale of the iron oxide particles adhering to the inner surface of the boiler tube and causing heat transfer inhibition from the heater drainage.

A turbine apparatus according to the present invention includes: a boiler that generates steam by heat from a heat source; a steam turbine that operates by steam of the boiler; and a rehydrator that rehydrates steam from the steam turbine; The reconstituted water after the water is condensed is supplied to the water supply system on the boiler side as a water supply; and a part of the steam that is sent from the steam turbine to the reheater is extracted as the pumping system, and the water is used as the pumping unit. a water supply heater for supplying water and a filter device for filtering the heater discharged from the water supply heater and then sending it to the water supply system for recovery; wherein the filter device has a filter element having a hole diameter of 1 to 5 μm.

In the water treatment method for the heater drain of the turbine device of the present invention, the water supply from the boiler is evaporated and superheated by heat from the heat source, and the steam turbine is operated by the generated steam, and the steam discharged from the steam turbine is passed through the rehydrator. Condensed as a water supply, the water supply to the boiler side is supplied to the water supply, and a part of the steam sent from the steam turbine to the reheater is extracted and used as an air pump, and the water supply heater is used to heat the water supply heater. The heater generated by the above-described air-cooling is filtered to be drained by the water supply system, and the heater drain is filtered using a filter element having a hole diameter of 1 to 5 μm.

In the present invention, it is preferred to filter the full amount of the heater drain Send it to the water supply system. Preferably, the water supply heater that filters the drainage is a low-pressure water supply heater.

According to the present invention, by filtering the heater drain using a filter element having a pore diameter of 1 to 5 μm, the iron oxide fine particles can be efficiently removed from the heater drainage, and the iron oxide fine particles can be prevented from adhering to the inner surface of the boiler tube.

According to the present invention, the mechanism for measuring the iron concentration in the heater drain and changing the water supply target of the heater drain corresponding to the iron concentration becomes unnecessary.

According to the present invention, the entire amount of the heater drain can be filtered and sent to the water supply system to increase the water recovery rate.

Most of the iron oxide fine particles contained in the boiler water supply are caused by the low pressure heater drainage. For a typical filter element, there is an appropriate flow rate of water used. Then, the low-pressure heater drain is subjected to a filtration treatment, and only about one-tenth of the amount of treated water can be used as compared with the case where the re-watering is performed in a full amount. Therefore, it is possible to provide a small-sized filter device in which the number of filter elements installed in the filter device is reduced.

Most of the iron oxide fine particles generated by the low-pressure heater are needle-shaped crystals which can be trapped by a film having an effective filter pore size of 3 μm. Therefore, the filter element having an effective filter pore size of 1 to 5 μm can be sufficiently captured. Since the filter pore diameter is 1 to 5 μm and the shape of the fine particles is needle-like, the water pressure loss does not easily rise even if it is continuously used.

1‧‧‧Rehydrator

2‧‧‧Electromagnetic filter

3‧‧‧ pure water installation

4, 6, 18‧‧‧ pipeline

5‧‧‧Low-pressure water supply heater

7‧‧‧Deaerator

8‧‧‧High-pressure water supply heater

9‧‧‧Boiler

10‧‧‧Superheater

11, 13, 15‧‧‧Vapor lines

12‧‧‧High-pressure turbine

14‧‧‧Reheater

16‧‧‧Low-pressure turbine

17‧‧‧Exhaust line

19‧‧‧Filter

20‧‧‧Return line

Figure 1 is a block diagram of a turbine apparatus of an embodiment.

Figure 2 shows the experimental results.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

Fig. 1 shows a turbine device of an embodiment, in which water (rehydration and make-up water) in the rehydrator 1 is supplied to a low-pressure water supply through a pipe 4 through an electromagnetic filter 2, a pure water device 3 using an ion exchange resin. The device 5 is heated. The heated water is sent to the deaerator 7 through the line 6, and is subjected to a degassing treatment, and then heated by the high pressure water supply heater 8 to be sent to the boiler 9. The steam generated in the boiler 9 is superheated by the superheater 10, and then supplied to the high-pressure turbine 12 through the vapor line 11.

The vapor that has flowed out of the high-pressure turbine 12 is sent to the reheater 14 through the vapor line 13, is reheated, and then supplied to the low-pressure turbine 16 through the vapor line 15, and flows out of the vapor to return to the rehydrator 1.

The evacuation line 17 is branched from the vapor line 13, and the vapor from one portion of the line 17 is branched and supplied to the heat source side of the low-pressure water supply heater 5, and exchanges with water to become drain (low-pressure heater drain). The low-pressure heater is drained, sent to the filter 19 through the line 18, filtered, and supplied to the water side of the low-pressure water supply heater 5 through the return line 20. The return line 20 can also be connected to the inflow of the low pressure water supply heater 5 The line 4 on the side or the line 6 on the outflow side.

Filter element used in the above filter 19, aperture (effective The filter pore diameter is 1 to 5 μm, preferably 1 to 4 μm, more preferably 2 to 4 μm, and particularly preferably 2 to 3 μm. When the pore diameter of the filter element is smaller than 1 μm, the water pressure loss increases, and when it is larger than 5 μm, the trapping ability of the iron oxide microparticles is insufficient. The LV of the filter 19 is 0.2 to 1.2 m/Hr, more preferably about 0.3 to 1.0 m/Hr.

The material of the filter element is not particularly limited. However, due to low pressure The heater drain temperature is 80 to 130 ° C, preferably a material that is durable for at least one year at this temperature. Specifically, a nonwoven fabric composed of polyphenylene sulfide fibers or fluororesin fibers can be used. When the non-woven filter element is used alone, it may be caused by the accumulation of the filter residue and the flow of the filtered fluid, and the fiber layer may be displaced to obtain a predetermined filtration efficiency. Therefore, as the filter element, it is preferable to use a filter element having a three-layer structure, that is, both sides of the non-woven fabric are sandwiched by a spunbonded sheet having mechanical strength, and embossing is performed to integrate them.

According to this embodiment, oxygen can be drained from the low pressure heater Since the iron fine particles are sufficiently removed, it is possible to prevent (including suppression) adhesion of the iron oxide fine particles to the inner surface of the boiler tube. Since the full amount of the low-pressure heater drain is filtered, the water recovery rate is high, and the structure for allowing the filter 19 to pass water is also simple, and the cost can be reduced.

[Examples] Experimental example 1

For the effective filter pore size is 3, 1, 0.45, 0.2, 0.1 μm The first to fifth thin film filter elements are arranged in series, and the low-pressure heater of the turbine equipment after the CWT treatment in the thermal power generation is drained from the 3 μm film side at a line speed (LV) of 2.3 cm/min. 4Hr was passed through the water, and the distribution of the amount of iron oxide captured by the filter element of each pore diameter was measured. The results are shown in Table 1.

The total amount of iron oxide captured by the first to fifth thin film filters was divided by the cumulative flow rate of water to be converted into Fe (iron), and the result was 25 μg-Fe/L. The total iron concentration in the filtered water after passing through the first to fifth film filters was 1.4 μg-Fe/L.

Experimental example 2

A pleated filter element (effective filter pore size: 2 μm) having a diameter of 70 mm and an effective surface length of 25 mm is used. The pleated filter element is a non-woven spunbonded sheet composed of fine fibers of a polyphenylene sulfide which is spun by a melt blow method. The embossing was carried out to form an SMS sheet, and three pieces of SMS sheets were folded and formed. The pleated filter element was allowed to pass water at 580 mL/min at 125 ° C (pressure 0.25 MPa (G)). The total iron concentration of the influent water is 48 μg- Fe/L, the total iron concentration in the filtered water at the outlet of the pleated filter element is 2.0 μg-Fe/L.

As a result of measuring the particle size distribution of the filter residue obtained by continuously flowing water by an ultrasonic granulometer, as shown in Fig. 2, the average particle diameter of 50% by weight was 7 to 8 μm. The cumulative content of particles having a particle diameter of 1 μm or less and particles having a particle diameter of 5 μm or less is about 5% by weight and about 40% by weight, respectively. Thus, it was found that the use of a filter element having an effective filtration pore size of less than 1 μm could not improve the particle recruitment rate, and when the filter element having an effective filtration aperture larger than 5 μm was used, the particle recruitment ratio was poor.

Furthermore, in this state, even if the water flow for 120 days is continued, the differential pressure is only about 5 kPa, and even if the drainage water having a concentration of about 20 μg-Fe/L is passed through the water for one year, it will not hinder the water flow. The differential pressure rises.

The present invention has been described in detail with reference to the specific embodiments thereof, and various modifications can be made without departing from the spirit and scope of the invention.

In addition, this application is hereby incorporated by reference in its entirety by reference in its entirety in its entirety in the the the the the the the

1‧‧‧Rehydrator

2‧‧‧Electromagnetic filter

3‧‧‧ pure water installation

4, 6, 18‧‧‧ pipeline

5‧‧‧Low-pressure water supply heater

7‧‧‧Deaerator

8‧‧‧High-pressure water supply heater

9‧‧‧Boiler

10‧‧‧Superheater

11, 13, 15‧‧‧Vapor lines

12‧‧‧High-pressure turbine

14‧‧‧Reheater

16‧‧‧Low-pressure turbine

17‧‧‧Exhaust line

19‧‧‧Filter

20‧‧‧Return line

Claims (6)

A turbine apparatus comprising: a boiler that generates steam by heat from a heat source; a steam turbine that operates using steam of the boiler; and a rehydrator that rehydrates steam from the steam turbine; The reconstituted rehydrated water is supplied to the water supply system on the boiler side as a water supply; and a part of the steam that is sent from the steam turbine to the reheater is extracted as a pumping water, and the water supply is heated by the water supply system. a water supply heater; and a filter device that filters the heater drain discharged from the water heater and sends it to the water supply system for recovery; wherein the heater drain is a combined water treatment (CWT) turbine device The low-pressure heater is drained, and the filter device has a filter element having a pore diameter of 2 to 4 μm. The turbine apparatus according to claim 1, wherein the filtering device sends the entire amount of the heater drain to the water supply system. The turbine apparatus according to claim 1 or 2, wherein the filter element of the filtering device is an embossed product, which is a three-layer integrated filter element having a spunbonded/non-woven/spun bonded sheet. . Water treatment method for heater drainage of turbine equipment, The water supplied from the boiler is evaporated and superheated by heat from the heat source, and the steam turbine is operated by the generated steam, and the steam discharged from the steam turbine is condensed by the water separator to supply water, and the boiler side is supplied to the water supply. A part of the steam sent from the steam turbine to the reheater is extracted as air, and the water supply is heated by the water supply heater, and the heater drain generated by the air-cooling is filtered by the water supply heater. The water supply system recovers; characterized in that the heater drain is a low-pressure heater drain of a turbine device using a composite water treatment (CWT), and the heater drain is filtered using a filter element having a pore diameter of 2 to 4 μm. A method of treating a water for a heater drain of a turbine apparatus according to claim 4, wherein the entire amount of the heater drain is filtered using the filter element to collect the water supply system. The water treatment method for a heater drain of a turbine apparatus according to the fourth aspect of the invention, wherein the filter element of the filter device sandwiches both sides of the non-woven fabric with a spunbonded sheet and is integrated by embossing. The filter element of the three-layer structure.