JPS6120761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning up a thermal power plant. FIG. 1 shows a cleanup system of a conventional thermal power plant, where 1 is a condenser, 2 is a pipe whose one end is connected to the lower part of the condenser 1 via a condensate pump 3, and 4 is the pipe. A condensate demineralizer 5 whose inlet side is connected to the other end of the channel 2 has one end connected to the condensate demineralizer 4 via the low pressure feed water heater 6 and the other end connected to the inlet side of the deaerator 7. 8 is a pipe connected to the deaerator 7 from a steam source such as a boiler (not shown); 9 is a deaerator water storage tank;
0 connects one end to the lower part of the deaerator water tank 9,
A pipe line in which a water supply booster pump 11, a valve 12, a water supply pump 13, and a valve 14 are incorporated, 1
6 is a bypass pipe line of the water supply pump 13, with one end connected to the outlet side of the water booster pump 11, a valve 15 installed in the middle, and the other end connected to the outlet side of the water supply pump 13 and valve 14; Valve 18 on the way
This is a minimum flow pipe line of the water feed pump 13, with one end connected to the outlet side pipe line of the water feed pump 13 and the other end connected to the deaerator water tank 9.

19 has one end connected to the outlet side valve 1 of the water supply pump 13.
4, a high-pressure feed water heater 20 is installed in the middle, and the outlet side valve 2 of the high-pressure feed water heater 20 is connected to the other end.
The pipe 19 is connected to the pipe to the boiler. 22 is a preboiler cleaning pipe, one end of which is connected to the valve 21 and the high pressure feed water heater 2.
The condensate is connected to the pipe line 19 between 0 and 0, with a valve 23 installed on the way, and the other end connected to the blow pipe 25 via the valve 24, and furthermore with a valve 27 installed on the way. connected to device 1.

In the above configuration, the conventional clean-up method in a high-pressure preboiler system of a thermal power plant is explained as follows: condenser 1, pipe line 2, and pipe line 5, then low-pressure feedwater heater 6, and the pipe line 5 on the downstream side.
After pure water is passed through the so-called low-pressure preboiler system of the deaerator 7 and the deaerator water tank 9 for cleaning, cleanup of the high-pressure preboiler system is started in the following order.

First, using the water in the deaerator water tank 9 that stores pure water sent from the low-pressure preboiler system, the water supply booster pump 11 is used to drain the pipes 10, 16, 1.
9. After water flushing has been performed on the high-pressure feed water heater 20, the pipe line 22, and the plow pipe 25, the high-pressure preboiler system is cleaned up while circulating water through the low-pressure preboiler system and the high-pressure preboiler system. It can be done. The water circulation system at this time is as follows.

Condenser 1 → Pipe 2 → Condensate pump 3 → Condensate desalination device 4 → Pipe 5 → Low pressure feed water heater 6 → Deaerator 7 → Deaerator water tank 9 → Pipe 10 → Water supply booster pump 1
1 → Pipe line 16 → Pipe line 19 → High pressure feed water heater 20 →
Pipe 22 → Pipe 26 → Condenser 1 This circulating water is heated in the deaerator 7 by steam supplied from a steam source (not shown) via the pipe 8. In addition, the above circulating water is purified by the condensate pump 3.
However, the conventional clean-up method described above has the following drawbacks.

(a) Clean-up of thermal power plants is carried out to remove iron rust, sludge, dust, and other foreign substances in the system to satisfy the water quality conditions of the boiler water supply. Usually, clean-up involves reducing iron content. It is the rate-limiting factor in the process. In order to quickly remove iron rust and prevent iron from leaching from equipment made of steel, the temperature of the clean-up water should be adjusted in the clean-up of the high-pressure preboiler system.
It would be desirable to raise the temperature to around 150°C, but with conventional methods it is approximately 50°C, and even in plants with sufficient heating steam sources, it is extremely difficult to raise the temperature to over 100°C.

(b) When cleaning up a conventional high-pressure preboiler system, the temperature of the cleanup water should be kept at the normal temperature.
Deaerator 7 was able to only heat around 50℃.
This is because the water heated by the steam supplied from the pipe line 8 is cooled by the condenser 1 in the circulation system, and the water temperature drops to room temperature. In addition, in the conventional method, heating of clean-up water must be done while circulating the water in the above-mentioned circulation system that includes condenser 1, so cooling in condenser 1 was an unavoidable problem. .

(c) Even if cleanup is performed with water at about 50℃, it is not very effective in removing minute iron rust in the system, and on the other hand, corrosion of steel materials in the system will progress to a certain extent. Iron content could not be removed smoothly, resulting in a prolonged clean-up process for the high-pressure preboiler system.

The purpose of the present invention is to provide a clean-up method using high-temperature water in the clean-up of a high-pressure preboiler system in order to effectively and quickly clean-up a thermal power plant.To achieve this purpose, the following (a) Methods from ) to (c) are adopted.

(a) a water pump 13 that was not used in the conventional cleanup method described in connection with FIG. 1;
The temperature of pure water added with hydrazine in the deaerator water tank 9 is controlled using the minimum flow pipe 17.
Raise the temperature of high-temperature water to 100-180℃ (target about 150℃).

(b) Transfer this high-temperature water to the high-pressure preboiler system, i.e.
In the figure, the pipe 19 and the high-pressure water heater 20 are filled with water. The coagulation effect of this high-temperature water containing hydrazine makes it easier to remove fine rust within the system, and also turns the film formed on the surface of the steel material within the system into a stable black rust, which also suppresses the elution of iron. Do it like this.

(c) Repeat the operations in (a) and (b) above to clean up the inside of the system by pumping and extruding high-temperature water into the high-pressure preboiler system.

The cleanup method of the present invention will be explained with reference to FIGS. 1 and 2. Condenser 1, pipe line 2, condensate pump 3, condensate desalination device 4, pipe line 5, low pressure feed water heater 6, deaerator 7, deaerator in the clean-up system of the thermal power plant shown in Fig. 1 When the clean-up of the system in the deaerator water tank 9 is completed, pure water containing hydrazine is poured into the deaerator water tank 9 to the upper limit water level. Then, pipe line 10 → water booster pump 11
→Valve 12→Water pump 13→Valve 14→Pipeline 17→
A circulation system of valve 18 → deaerator water tank 9 is configured,
The water booster pump 11 and the water pump 13 are driven to circulate water (hydrazine-containing pure water) in the system. In this case, the outlet valve 21 of the high-pressure feed water heater 20 and the inlet valve 23 of the preboiler cleaning pipe line 22 are in a closed state. In the above circulation, under the flow conditions in the water booster pump 11 and the water supply pump 13, the temperature of the circulating water gradually increases, and the water temperature in the circulation system including the deaerator water tank 9 rises to around 150°C. After that, the circulation is stopped.

Next, the inlet valve 23 and blow valve 24 of the preboiler cleaning pipe line 22 are opened, and the valves 12, 14, 18,
Close the valve 27 and move the deaerator water tank 9 → line 10 → water booster pump 11 → bypass line 16 → valve 1
5 → Pipe line 19 → High pressure feed water heater 20 → Pipe line 22 →
After establishing the water flow system of valve 23 → valve 24 → blow pipe 25, start the water supply booster pump 11 to fill the high-pressure preboiler system with high-temperature water, and when the water level of the deaerator water tank 9 reaches the lower limit. , stop water filling. Thereafter, the iron content in the system is reduced by repeating the operations of filling the deaerator water tank 9 with water, raising the temperature of the stored water, and pumping high-temperature water into the high-pressure preboiler system.

Figure 2 shows a comparison of the cleanup results of a conventional method and the method of the present invention (using high-temperature water around 150°C) for cleanup of a high-pressure preboiler system in a thermal power plant. It is.

In the figure, the curve shows typical cleanup results according to the conventional method. According to the curve, the cleanup completion standard value for the high-pressure preboiler system is determined by the iron concentration at the outlet of the high-pressure feed water heater 20. While it is less than 50PPb,
The cleanup time required is approximately 250 hours. Furthermore, the characteristic of the iron content reduction curve according to the above conventional method is that the iron content reaches around 100 PPb about 50 hours after the start of cleanup, but after that there is an extremely gradual decreasing trend.

On the other hand, the curve shows the case when the cleanup method of the present invention is used, and after reducing the iron content by the conventional method from the start of cleanup to point a,
The points between the dots show the results of cleanup using high temperature water of around 150° C. according to the method of the present invention. The iron concentration at point a is 100PPb, the cleanup time is about 70 hours, and the iron concentration from point a is 100PPb.
The time required to reduce to 50 PPb was about 30 hours, and the total cleanup time was short, about 100 hours. That is, the iron content reduction curve according to the method of the present invention is characterized by a rapid decrease in iron content;
The achieved concentration of iron is extremely lower than that of conventional methods;
And the time required for cleanup is 1/2 compared to the conventional method.
This has been reduced to 5.

In the clean-up according to the method of the present invention shown in Figure 2, high-temperature water of around 150°C was used, but from the standpoint of suppressing the increase in iron content due to corrosion during clean-up, the temperature of 100°C is theoretically low. As a result, corrosion acceleration due to dissolved oxygen is completely reduced to zero, so some effects can be expected. In addition, when considering complete safety of the steel surface film, a water temperature of 200°C or higher is desirable, but considering the design conditions of the current deaerator water tank, an upper temperature limit of about 180°C is appropriate. Therefore, the cleanup temperature according to the present invention is set at 100 to 180°C, with a target of around 150°C.

In short, in a thermal power plant, the present invention allows pure water containing hydrazine in a deaerator water tank 9 to flow through a minimum flow pipe 17 that returns the pure water flowing out from the water tank to the water tank by driving the water supply pump 13. This is a clean-up method for thermal power plants, which is characterized by raising the temperature to 100 to 180 degrees Celsius by circulating the water, and cleaning up the high-pressure preboiler system using this high-temperature water. As explained with reference to the figure, according to the method of the present invention, the iron content decreases more rapidly than in the conventional method, and the final concentration of iron content is extremely low. Iron concentration from 100PPb
The time required to reduce the amount to about 50PPb has been shortened to about 30 hours, and the total time required for cleanup is therefore about 100 hours, which is 1/2.5 of the conventional method.

[Brief explanation of the drawing]

Figure 1 shows a diagram of a clean-up system for a thermal power plant to explain the disadvantages of the conventional method and the method of the present invention, and Figure 2 shows the results of the conventional method for clean-up of a high-pressure preboiler system of a thermal power plant. FIG. 3 is a comparative curve diagram of results obtained by the method of the invention. In the figure, 1... condenser, 4... condensate desalination device,
6...Low pressure feed water heater, 7...Deaerator, 9...Deaerator water tank, 13...Water pump, 17...Minimum flow pipe line, 20...High pressure feed water heater.

Claims (1)

[Claims] 1. In a thermal power plant, pure water to which hydrazine has been added in a deaerator water tank is circulated by passing it through a minimum flow pipe that returns the pure water that flows out of the water tank to the water tank by driving a water supply pump.
A method for cleaning up a thermal power plant, characterized by raising the temperature to 100-180°C and cleaning up a high-pressure preboiler system using this high-temperature water.