JPS63150504A - water treatment equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a water treatment device and a water treatment method for a steam power generation plant, and more particularly to a device for adjusting pH suitable for plant constituent materials.

[Conventional technology]

Conventionally, both steel and steel materials have been generally used in steam power generation plants, and studies have been made to determine what the pH of the 5-system water should be from the viewpoint of corrosion and elution of both materials. One of them is Rennosuke Okamoto [Results of water treatment characteristics test of Taketoyo Thermal Power Station Unit 1], Thermal Power Generation Vo111.20
．． NQ5. As stated in May 1969, p. 498-517, increasing the pH of system water reduces the amount of iron leached from steel, but since copper alloys are used in the condenser and low-pressure water heater, On the contrary, the IkJpH of this plant is assumed to be 9.4 because the amount of steel eluted increases significantly.

In addition, Japanese Industrial Standards (JIS B8223-1977
According to ``Boiler feed water and boiler water quality,'' the standard pH value of feed water for thermal power plants with high-pressure boilers is 8.8 to 9.5. It is desirable to keep it at a high level.

Furthermore, for the same reasons as mentioned above, the pH value of the secondary system water of pressurized water nuclear power plants, which use the same constituent materials and implement the same water quality management as thermal power plants, is also 8.5 to 9.
．． It is set at 5.

[Problem that the invention seeks to solve]

In the above conventional technology, the entire condensate, water supply, and steam systems in which steel and steel materials are mixed are managed at one pH value, so the pH value is a compromise for both materials, and their corrosion and elution It was also considered to be unavoidable to some extent. These corrosion products adhere to boilers, turbines, and the like, causing problems such as boiler overheating and reduced turbine efficiency. For this reason, there is a problem in that it is necessary to periodically perform acid cleaning of deposits that requires many hands and chemicals, jet cleaning that uses high-pressure water, and the like.

- The purpose of the present invention is to solve the above-mentioned problems of conventional steam power plants, and to provide a water treatment system that can separately manage the pH values of the system where the amount of corrosion and elution of steel materials is the highest and the other systems that contain steel materials. The objective is to provide a water treatment method that manages the pH value optimal for each system.

[Means for solving the problem] Fig. 2 shows the relationship between the pH of system water and the iron concentration at each point in the plant in a plant where the pipe materials of the low-pressure water heater and the high-pressure water heater are made of carbon steel. From this figure, the largest amount of iron is eluted between the condensate booster pump outlet and the deaerator inlet, that is, on the low-pressure feed water heater water supply side, and the iron elutes between the deaerator outlet and the main steam. That is, it can be seen that it adheres to the high-pressure water supply heater water supply side and the boiler. Also from the same figure.

It can be seen that when the pH of the system water is set to 9.6 or higher, the amount of iron eluted from the water supply side of the low-pressure water supply heater becomes extremely small.

Figure 3 shows a plant where the condenser is made of copper alloy pipes. The relationship between the pH of system water and the copper concentration at the condensate pump outlet is shown. This figure shows that copper elution increases rapidly when pH exceeds 9.5.

From the above study results, in plants with copper alloy pipe condensers and carbon steel pipe low-pressure water heaters, the pH of the system on the water supply side of the low-pressure water heater should be set to 9.6 or higher, and the pH of other systems including the condenser should be set to 9.6 or higher. It was found that the amount of iron and copper leached from the entire plant can be minimized by adjusting the pH to 9.5 or less.

In order to carry out such water treatment, ammonia, ammonia,
Injecting an alkaline agent such as hydrazine, and installing a new cation exchange tower and its bypass system at the outlet of the low-pressure feed water heater.
Therefore, a portion of the alkaline agent may be removed.

[Effect]

The cation exchange column is filled with a hydrogen-type cation exchange resin, which removes ammonia, hydrazine, etc., which are alkaline agents injected to raise the pH. The heat resistance temperature of the cation exchange resin is about 150°C, whereas the outlet temperature of the low pressure water heater is about 130°C, so there is no problem in terms of ion exchange performance even if a cation exchange tower is installed here.

Since the pH after the cation exchange tower exit needs to be maintained at a certain value, a bypass system for the cation exchange tower is installed to bypass a portion of the feed water and combine it with the feed water that has passed through the cation exchange tower. Afterward, by providing a pH meter or an electrical conductivity meter and adjusting the opening degree of the bypass valve according to the signal, the pH value after merging can be controlled to be constant.

Since the resin in the cation exchange column reaches a break point after being used for a predetermined period of time, it must be regenerated with sulfuric acid or hydrochloric acid before reuse. The regenerator can also be used for the cation exchange resin in the condensate desalination device.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

, In Figure 1, the system water flows as follows.

Copper alloy pipe condenser 2 → condensate piping 3 → condensate pump 4 → condensate desalination device 5 → condensate boost pump 6 → carbon Si pipe low pressure feed water heater 7 → hydrogen type cation exchange tower 2° and The bypass pipe 2 and bypass valve 22 → depressurizer 8 → water supply pipe 9 → water supply pump 10 → high pressure water heater 11 → boiler economizer 12
→ Boiler water wall 13 → Main steam pipe 14 → Turbine 1 → Condenser 2° In this flow, the system water is converted into steam by the boiler economizer 12 and the boiler water wall 13, and then flows into the turbine 1. and work. A part of the steam that has entered the turbine 1 is sent to the high pressure water heater 11 via oil and air pipes 15A and 15B.
and the low-pressure water supply heater 7, the water supply is heated and becomes condensed water (drain), and the water supply heater drain piping 16A and 1
6B. Mixed into the water supply through the low pressure water heater drain pump 17.

According to the example in Figure 1, in order to prevent corrosion of each equipment and piping,
Using the chemical injection device 18, an alkaline agent is injected into the water supply downstream of the condensate desalination device 5. As the alkali agent, a volatile chemical such as ammonia or hydrazine is used. In order to maintain the pH of the feed water at a constant value after injection of the alkaline agent, a PH meter or electrical conductivity meter 19A is installed downstream of the condensate boost pump 6.
The injection pump of the chemical liquid injection device 18 is automatically controlled based on the signal. By keeping the pH of the water supplied to the low-pressure water supply heater 7 at 9.6 or higher using the alkali agent injected in this manner, corrosion and elution of steel materials in this system can be suppressed.

In FIG. 1, the water supply that has flowed out of the low-pressure water supply heater 7 is
A portion of the water is passed through the cation exchange column 20 to remove ammonia in the feed water, and the remainder passes through the bypass pipe 21 and the bypass valve 22, and then these are combined. pH after confluence
A meter or electrical conductivity meter 19B is provided, and the opening degree of the bypass valve 22 is adjusted according to the signal, and the pH after merging is adjusted to 9.5.
It can be kept at the following constant value. After that, a deaerator 8 degrees high pressure water heater 11. Boiler economizer 12. Boiler water wall13. While passing through the turbine 1 etc., the pH hardly changes and the water flows into the condenser 2.

FIG. 4 shows the relationship between the pH of the low-pressure feedwater heater outlet feedwater, the boiler coal-saving inlet feedwater pH, and the water passage rate of the cation exchange tower in one embodiment of the present invention.

Accordingly, by determining the set values of the pH value on the water supply side of the low-pressure water supply heater and the pH value of the feed water at the inlet of the energy saver, the water flow rate of the cation exchange tower can be determined, and the cation exchange tower can be designed.

For example, if the pH value of the water supply side of the low-pressure water supply heater is designed to be 9.7° and the pH value of the feed water at the inlet of the economizer is designed to be 9.4, the water flow rate of the cation exchange tower is designed to be 67%.

The embodiments described above are for supercritical pressure thermal power plants, but they can also be applied to subcritical thermal power plants and pressurized water type source/pre-power generation plant secondary systems, in which the condenser is a copper alloy pipe used to supply low-pressure water. The present invention can be applied when the heater includes a carbon steel pipe.

〔Effect of the invention〕

According to the present invention, it is possible to achieve corrosion protection for the equipment and piping of a steam power plant that has a low-pressure water heater including a copper alloy tube condenser and a carbon steel tube, and metal impurities in the system water can be reduced to about half or less. 1) Significantly longer acid cleaning intervals to remove corrosion products, (2) Reduced wastewater treatment costs, (3)
It has the following effects: jet cleaning of the high-pressure water heater becomes unnecessary; and (4) performance and efficiency are greatly improved because scale adhesion is eliminated.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a thermal power plant showing an embodiment of the present invention; Fig. 2 is a diagram showing changes in pH value and total iron in a plant where the low-pressure feed water heater and high-pressure feed water heater are carbon steel pipes; The figure shows PH in a plant where the condenser is a copper alloy pipe.
FIG. 4 is a diagram showing the relationship between the pH value of the feed water and the water flow rate of the cation exchange tower in one embodiment of the present invention shown in FIG. 1. 1... Turbine, 2... Condenser, 3... Condensate piping, 4... Condensate pump, 5... Condensate desalination device, 6...
・Condensate boost pump, 7...Low pressure water heater, 8...
Deaerator, 9... Water supply piping, 10... Water supply pump, 1
1... High pressure water heater, 12... Boiler economizer, 1
3... Boiler water wall, 14... Main steam piping, 15.
...Bleed air piping, 16...Water supply heater drain piping, 17
...Low pressure water supply heater drain pump, 18...Chemical liquid injection device.

Claims (1)

[Claims] 1. In a steam power generation plant equipped with a condenser made of a material containing copper, a low-pressure feed water heater made of a material containing carbon steel, and a chemical injection device to the water supply inlet of the low-pressure feed water heater, low-pressure water supply A water treatment device characterized in that a hydrogen type cation exchange tower and its bypass system are provided at the water supply outlet of the heater.