JPS5815704A - Equipment for removing iron oxides from feed water of power plant - Google Patents

Abstract

PURPOSE:To efficiently remove iron oxides from feed water, by providing permanent magnets in the deaeration chamber of a deaerator to which drained water from a high-pressure feed water heater is returned. CONSTITUTION:A feed water pipe 21 connected to a low-pressure feed water heater and a drain pipe 18c for a high-pressure feed water heater are connected to the top of a deaerator 10. A heating steam pipe 25 coupled to a boiler is connected to the side of the deaerator 10. A plurality of permanent magnets 27 are provided at the bottom of a deaeration chamber 28. As a result, iron oxides are efficiently removed from the feed water system to obtain boiler feed water of good quality to heighten the operation efficiency of a thermal power plant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for effectively capturing and removing iron oxides in water of a water supply system of a thermal power plant and its pond.

In general, most of the main equipment, auxiliary equipment, piping, etc. in thermal power plants and other power plants are made of steel. Highly purified water is used as a circulating medium, and a small amount of anti-corrosion agent is added to control the iron concentration in the system water in order to prevent iron from leaching into the water from the iron materials it comes into contact with. . However, due to long-term cyclical use, it is unavoidable that iron from steel materials is eluted into water little by little, and the eluted iron components are composed of iron oxides (mainly ferromagnetic Fe3O4 and
) is accumulated in the plant system. These iron oxides are found on the inner walls of boilers, turbines, high-pressure feed water heaters,
If it adheres to or accumulates on the main water supply flow meter, boiler water supply adjustment valve, or other circulation pipes, it may cause overheating of the pipes, etc.
This causes various problems such as a decrease in turbine output, a pump overload due to an increase in differential pressure, and inappropriate flow rate instructions. In addition, in recent years, the difference in power demand between day and night has tended to widen rapidly, and thermal power plants in particular have been forced to shut down at night, operate at low load, operate at a reduced voltage, etc. in response to the widening power demand difference. Furthermore, complex and troublesome demand-response operations such as weekend shutdowns are carried out. Starting in such operation,
Repeated shutdowns or load changes cause stagnation of water supply and condensate, as well as sudden changes in flow rate, pressure, and temperature, and condensate adheres to or accumulates in equipment piping, etc., especially when starting up the plant or when the load increases. The peeling off and simultaneous flow of iron oxides causes a temporary increase in iron oxides in the feed and condensate.
When these iron oxides are delivered to each device and adhere to them, they are deposited abnormally in areas where they tend to accumulate, causing the aforementioned undesirable problems.

Therefore, removing iron oxides from the power plant system to the outside of the system is an extremely important requirement from the standpoint of safe and highly efficient operation of the power plant, in other words, improving reliability and increasing output.

In line with this demand, several methods have been proposed for removing iron oxides in thermal power plants. For example, Japanese Patent Application No. 48-49482 describes an electromagnetic filter A consisting of a cylindrical reactor water vessel having particles made of ferromagnetic material and an electric coil for generating a magnetic field. However, this method not only requires electric power to apply a current to the coil to generate a magnetic field, but also heats up the water reactor, so a means for cooling it is required.

Furthermore, a water reactor has been proposed in which a reactor material using a permanent magnet is attached to capture and remove magnetic substances in the fluid.

However, when this reactor water heater is installed in the water supply system of a power generation plant, there is a drawback that in addition to the reactor water heater itself, additional equipment must be newly installed. As mentioned above, there are several proposals, but since it is difficult to adopt any of them in practice, in reality, during periodic inspections and repairs, iron oxides deposited on equipment, piping, etc. must be manually removed. The inside of the system is being cleaned.

The purpose of the present invention is to solve these problems and provide a device that can remove iron oxides in water supply extremely efficiently by using a series of devices in a normal power plant system. be.

Before explaining the apparatus of the present invention, an overview of the system of a thermal power plant will first be explained with reference to FIG. 1 of the accompanying drawings. The water is supplied through a condenser 3, a condenser botwell 4, a condensate pipe 5, a condensate pump 6, and a condensate desalination device 7, and is removed from the low-pressure feed water heaters 9A to 9C by a condensate boost pump 8. Sent to air 1o. Furthermore, a deaerator water tank 11 and a water supply pipe 12
, the feedwater pump 13 and the high-pressure feedwater heaters 14A to 14C enter the boiler 15, where it becomes steam and flows into the steam pipe 16.
After passing through the turbine 1 to generate electricity 2, it returns to the condenser 3. In addition, 17A to 17C are low pressure feed water heater drain/pipes, 18A to 18C are high pressure feed water heater drain pipes, 19 is a drain pump, and 20A to 20F are air extraction pipes from the turbine. In the above-mentioned thermal power plant system, it is possible to analyze and measure the amount of iron in the main equipment and devices, and to examine the behavior of iron oxide in the water circulation. Various types of iron oxide removal equipment and their effective installation were determined by practical examination of the parts, and a permanent magnet was installed and built into the deaeration chamber of the deaeration chamber 10 where the drain water of the thermal power plant is refluxed. It was discovered that iron oxides in the system can be collected and removed extremely effectively. According to research conducted by the present inventors, iron in the system water decreases at the outlet of the condensate desalination device 7, increases until the outlet of the deaerator 10, and then decreases again at the inlet of the boiler 15. I understand. This trend was observed in different power plants to varying degrees. This decrease in iron is caused by the high-pressure feedwater heater drain water containing a large amount of iron entering the deaerator and reaching the boiler 15.
It is estimated that the iron oxides are deposited on the main water supply flowmeters and boiler water supply control valves of 4A to 14C1. Furthermore, the remaining leached iron is carried into the boiler and adheres to the boiler ice wall tubes as iron oxides, which is extremely disadvantageous. Therefore, an increase in the concentration of iron in water, especially in the water supply system, is a major factor that hinders the safe and efficient operation of thermal power plants, and in particular, a relatively large amount of iron is likely to be leached out from the high-pressure feedwater heater drain piping system. Focusing on the fact that iron oxide precipitation and deposition phenomena are noticeable in equipment from high-pressure feed water heaters to boiler feed water regulating valves, effective removal of iron oxides was pursued. As a result, it was found that if a permanent magnet is installed in the deaeration chamber of the deaerator 10, iron oxides in the water supply system water of a thermal power plant can be easily and efficiently collected and removed. .

The present invention has been made based on such findings, and provides a power generation system characterized in that a permanent magnet is provided in the deaeration chamber of a deaerator through which drain water from a high-pressure feedwater heater of a power generation plant is recycled. This is a device for removing iron oxides from water in water supply systems in plants.

Hereinafter, an explanation will be given based on FIG. 2 showing an embodiment of the present invention. In FIG. 2, the upper part of the deaerator 10 is connected with the water supply pipe 21 connected to the low pressure feed water heater 9 and the high pressure feed water heater drain pipe 18C, and the side of the deaerator 10 is connected with the boiler 15. A connecting heating steam pipe 25 is connected.

The deaeration chamber 28 of the deaerator 10 includes a tray 24 for deaeration of supplied water and a tray storage chamber 23 storing the tray. ) permanent magnets 27 are placed thereon. In addition, 11 in FIG. 2 is a deaerator water tank, 12 is a water supply pipe, 22 is a spray seat, and 26
is a manhole.

In FIG. 2, the high-pressure feed water heater drain water containing a large amount of iron is combined with the feed water introduced from the low-pressure feed water heater 9 and degassed. In the deaeration chamber 28 of the deaerator 10, the eluted iron brought in from the low pressure feed water heater 9 and the iron generated in the drain pipe 18 connected to the high pressure feed water heater 14 are captured and removed by the permanent magnet 27, and the iron is removed. Good quality boiler feed water can be obtained.

The permanent magnet 27 that has captured the iron oxide can be easily taken out from the manhole 26.

FIG. 3 shows another embodiment of the device of the present invention, in which five permanent magnets 27 are mounted within the deaeration chamber 28 of the deaerator. In this device, a part of the tray 24 in the tray storage chamber 23 installed in the deaeration chamber 28 of the deaerator 10 is replaced by a permanent magnet 27. Tray 24
are provided so that the heated steam evenly contacts the supplied water when the heated steam deaerates the supplied water that has been atomized by the spray seat 22. As shown in FIG. 3, the middle stage of the tray provided in three stages can be replaced with five permanent magnets 27. In the case of partial replacement as described above, the deaeration effect due to contact between the feed water and the heated steam does not substantially decrease.

Further, FIG. 4 shows still another embodiment of the device of the present invention in which a permanent magnet is installed in the deaeration chamber 28 of the deaerator.
In this example, all the trays attached to the spray seat 22 to uniformly bring the atomized feed water into contact with the heated steam are replaced by permanent magnets 27. In that case, it is desirable to select the shape of the permanent magnet so as to maximize the contact between the water supply and the heated steam, and the permanent magnet can be placed inside the tray storage chamber. Of course, it is also possible to replace not all the trays but most of the trays with permanent magnets and leave a small portion of the trays. The alternative use of such permanent magnets provides satisfactory contact between the feed water and the heated steam, substantial degassing is achieved, and a very high degree of iron separation is achieved in the feed water.

In general, magnets exhibit a so-called aging phenomenon in which the magnetic flux density decreases over time under certain conditions, but since this aging phenomenon has a linear relationship with the logarithm of time, it is used in the device of the present invention. In this case, there is no practical problem. In addition, demagnetization of the magnet occurs due to structural changes, impacts, mechanical distortion, vibrations, etc. of the permanent magnet, so when considering such demagnetization of the magnet, in the present invention, ferrite magnet permanent magnet Furthermore, since the temperature of the feed water in the deaeration chamber 28 of the deaerator IO is usually about 150C when it comes into contact with the heated steam, the temperature at which the magnet loses its magnetic properties, i.e. The Curie point of a permanent magnet must be higher than this, but since the Curie point of a ferrite magnet is 450C, demagnetization is extremely small at a temperature of around 1500C, and from this point of view as well, ferrite magnets are preferable.

Hereinafter, the present invention will be explained in more detail using experimental examples.

Experimental Example 1 Using a Gauss Ba-ferrite permanent magnet, iron oxide (main component Fe304) and Fe3O4 reagent collected from a high-pressure feed water heater of an actually operating thermal power plant were suspended in aqueous ammonia. The relationship between the iron removal rate and time was examined by making it cloudy. In the experiment, a water tank in which each of the above iron oxides was suspended at a concentration of 1101) p in ammonia water with a pH of 9.2 and the above permanent magnet-containing water tank were connected by a pump and a flow meter.

Each tank was equipped with a light and an illumination meter on the opposite side, and the iron removal rate was determined from the transparency of the liquid. The temperature of the liquid was maintained at 90 tll" by a heater and a temperature controller, and the liquid was circulated at an in-tube flow rate of 6 oz/h. The obtained results are shown graphically in FIG.

As is clear from the figure, Fe in the water tank containing Fe3O4 reagent
50. As shown by curve A in the figure, the removal rate increased over time and reached 100% in about 40 minutes. Further, as shown by curve B, the removal rate of iron oxides collected from a high-pressure feed water heater of a thermal power plant reaches 100% in about 15 minutes.

In other words, it can be seen that substantially all of the iron oxides are captured by magnetic force by circulating the liquid in 40 minutes for the Fe3O4 reagent and in 15 minutes for the iron oxides collected from the high-pressure feedwater heater at the power plant. . The reason why iron oxides collected from high-pressure feed water heaters at thermal power plants are more likely to adhere to and be captured by magnets than the reagent Fe3O4 is because iron oxides are generated by corrosion of steel materials under high-temperature, high-pressure conditions. , main component Fe, 0
It is presumed that this is because, in addition to 4, a small amount of easily magnetized substance such as nickel is mixed in.

Experimental Examples 2 to 4 and Comparative Example 1 As shown in FIGS. 2 to 4 above, a permanent magnet was installed in the deaeration chamber 28 of the deaerator 10 in a thermal power plant in operation, and each removal device was Deaerator 1 when using
The iron concentration in the feed water at the outlet of 0 was measured over an extended period of time. The results are shown in Table 1 below. For comparison, the iron concentration in the feed water at the deaerator outlet when no firing magnet is attached, that is, when the device of the present invention is not used, is also shown.

Table 1 According to Table 1, in Examples 2 to 4, the iron concentration in the feed water at the outlet of the deaerator 10 was significantly reduced, and iron oxides were captured extremely efficiently by the permanent magnet 27. You can see that it has been removed.

As described above, with the device of the present invention, iron oxides in the water supply system of a power generation plant can be effectively removed and desirable boiler feed water of high quality can be obtained, so that the operating efficiency of the thermal power plant can be improved. and can be easily put into practical use.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a thermal power plant; FIGS. 2, 3, and 4 are schematic cross-sectional views of a device of the present invention with a built-in deaerator, with permanent magnets installed in different states; The figure shows Fe
It is a graph showing the relationship between the removal rate of 3O4 reagent and iron oxide collected from a high-pressure feed water heater of a thermal power plant using a permanent magnet and time. DESCRIPTION OF SYMBOLS 1... Turbine, 3... Condenser, 7... Condensate desalination device, 9A-9C... Low pressure feed water heater, 10... Deaerator, 11... Deaerator Water tank, 24...tray, 2
7...Permanent magnet, /7(. Kaya ZC 1 3rd item

Claims (1)

[Claims] 1. Iron oxidation in water in a water supply system in a power generation plant, characterized in that a permanent magnet is provided in the deaeration chamber of a deaerator through which drain water from a high-pressure feed water heater of the power generation plant is recycled. Object removal device. 2. An apparatus for removing iron oxides from water in a water supply system in a power plant, as set forth in claim 1, wherein the permanent magnet is provided at the bottom of the degassing chamber. 3. In claim 1, the permanent magnet is
A device for removing iron oxides from water in a water supply system in a power generation plant, characterized in that the device is installed in place of at least a portion of the tray in the deaeration chamber.