JPS61138808A - Anticorrosive device for thermal power plant - Google Patents

Abstract

PURPOSE:To aim at the promotion of longevity in service life and improvements in efficiency, by injecting drain water out of a high pressure feed water heater into a deaerator, while feeding this drain water and the upstream side of a low pressure feed water heater with a water treater and thereby making a pH-value of the drain water higher than that of the feed water. CONSTITUTION:A water treater is injected in feed water at the upstream side of a low pressure feed water heater 8A from a water treater injector 20. In addition, a second water treater is injected into a drain pipe line 18C of a high pressure feed water heater 13C from a water treater injection pipe line 21. Thus, a pH-value in drain water is made higher than that in feed water flowing in each of high pressure feed water heaters 13A-13C. On the other hand, the pH-value in the feed water further goes down as being heated yet higher in temperature at a boiler 15, whereby at a condenser 2, it comes to such a degree of the pH-value that a copper system material is usable for a pipe group. Therefore, reduction in a corrosive product generated out of a heating pipe of the feed water heater or a drain pipe line is well promotable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to protection for a thermal power plant, and particularly to something that reduces corrosion products generated in equipment, piping, etc. within the plant.

[Background of the invention]

Thermal power plants in recent years are supercritical thermal power plants (steam condition 5) where the steam conditions are high temperature and high pressure to improve power generation efficiency.
Progress has been made in the development of thermal power plants with a capacity of 38 C, 246 to 4/cm" or higher.

In such plants, corrosion products that adhere to plant equipment, piping, etc. are a major hindrance to plant operation, and this is due to the materials used, such as iron, copper, chrome, and nickel. .

In addition, the corrosion i depends on the pH of the feed and condensate water.

Conventionally, as a countermeasure against the problem 7, pH was controlled by injecting a water quality treatment agent into the upstream side of the low-pressure feed water heater, as in the device described in Japanese Patent Publication No. 127089/1989. Prevention has already been achieved. However, firepower 1
The occurrence of corrosion products in the feed and condensate water of plants was studied based on water quality survey results and actual data from actual plants.
Currently, a large amount of gas is generated from the heating pipes and drain piping of feed water heaters. To explain the conventional system with reference to FIG. Although attempts are made to reduce the amount of corrosion products i from metal members that come into contact with the water supply, it is not possible to prevent corrosion products from being generated on the heated steam side of the high-pressure feed water heater 13, that is, in the drain system. This is because the water quality treatment agent is injected into the water supply into the high-pressure feedwater heater 13 and boiler 15.
Even if the extracted steam from the turbine 1 is injected into the high-pressure feed water heater 13 from the extracted piping 19, the water quality treatment agent contained in this extracted steam is extremely small and the water quality treatment agent is decomposed at high pressure. It is not possible to increase the pH of the drain water of the feed water heater, and it is not possible to reduce the corrosion products generated from the heating tube of the high pressure feed water heater 13 or the drain pipe 18. If using this method, in order to make the drain water of the high-pressure feedwater heater have a high pI4, a large amount of water treatment agent must be introduced upstream of the low-pressure feedwater heater 8, and the condenser 2
Since the condensate flowing through the condensate also has a high pH, it is possible to reduce the Fe concentration, but conversely, at a high pH, the amount of copper and nickel leached from the condenser 2 tube group increases, and the condenser tube group A disadvantage arises in that copper-based materials cannot be used in the group.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a device that can reduce corrosion products generated in equipment, piping, etc. of a thermal power plant, while using a copper-based material for a condenser tube group.

[Summary of the invention]

The features of the present invention include a condenser that condenses steam flowing out of a turbine, a pump that sends out this condensate, a low-pressure feed water heater that heats this condensate, a high-pressure feed water heater that A thermal power plant comprising: a boiler that evaporates feedwater flowing out of a high-pressure feedwater heater and supplies steam to the turbine; and a means for supplying extracted steam from the turbine to the high-pressure feedwater heater. means for injecting drain water of the container into a deaerator provided between the low pressure feed water heater and the high pressure feed water heater, and supplying a first water quality treatment agent to the upstream side of the low pressure feed water heater. and a means for supplying a mackerel 2 water quality treatment agent to the drain system, so that the pH of the drain water is higher than that of the feed water flowing through the low-pressure feed water heater.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to FIG.

Figure 1 is a system diagram of a thermal power plant. Steam discharged from a turbine 1 is condensed in a condenser 2, passes through a condenser hot well 3, condensate piping 4t'', and is condensed by a condensate pump 5. The water is sent to the water desalination device 6 and further condensate pressure boost pump 7
The water is pressurized at 7'C@ and heated by low-pressure water heaters 8 to 8D, and the heated water is passed through a deaerator 9 equipped with a water storage tack 10 and passed through the water supply piping 12 to supply water. The pump 12 enters the high-pressure feed water heaters 13A to 13C, and the feed water flowing out from the high-pressure feed water heaters passes through the energy saver 14, becomes steam in the boiler 15, and reaches the turbine 1 through the steam pipe 16. It forms a closed loop.

In addition, the drain system 17A of the low pressure water heater
Drain systems 117A to 17D of the 17D1 high-pressure feedwater heater are provided, and drain water of the high-pressure feedwater heater is recovered to the deaerator 9. In addition, the water treatment agent is supplied from the injection device 20 to the water supply upstream of the eight low-pressure feed water heaters and to the water treatment agent injection pipe 21t-.
The water is then injected into the drain water of the high-pressure feed water heater. In this embodiment, the high-pressure feed water heater includes three heaters 13A to 13Ct.
- The water treatment agent is connected in series, and the water treatment agent is the drain pipe 18 of the heater 13C located closest to the boiler.
CK is injected. As another example, the water treatment agent may be injected directly into the body of the high pressure feed water heater 130.

The amount of the first water treatment agent injected into the upstream side of the low-pressure feed water heater and the second water treatment agent injected into the drain system of the high-pressure feed water heater are both at low pressure. Kp4 so that the pH of the feed water of the feed water heater is also a high value.
! I'm doing it. In other words, the water treatment agent is injected into the water supply upstream of the eight low-pressure feedwater heaters, and the feedwater enters the deaerator 9 and mixes with the drain water of the high-pressure feedwater heater. At this time, since the flow from the low pressure feed water heater side is larger than the flow rate from the drain of the high pressure feed water heater, even if the pH of the drain water of the high pressure feed water heater is high, the flow from the high pressure feed water heater 13A to The pH of the feed water flowing through 13C can be lowered to a lower value than the pH of the drain water of the high-pressure feed water heater.The temperature is raised in the boiler and turbine, the water treatment agent is decomposed, the pH value further decreases, and the pH value of the drain water of the high-pressure feed water heater can be lowered. In vessel 2, the pH value is such that copper-based materials can be used for the tube group.

In addition, the pH of the steam extracted from the turbine is low, and corrosion products are generated from the heating pipes and drain pipes 18A to 18C of the high-pressure feedwater heater, so a second water treatment agent is injected into the drain water of the high-pressure feedwater heater. , the pH is high to prevent corrosion products from forming. The drain pipe 18C of the high-pressure feed water heater 13C on the side closer to the high-temperature side spoiler is suitable as the injection point for the second water treatment agent. The drain of drain pipe 18C is
Since it flows sequentially to the high-pressure feedwater heaters 13B and 13A, the amount of corrosion products in these high-pressure feedwater heaters can be reduced. Also, as water treatment agents, NH40H, N2
Hz etc. are injected.

With this configuration, the pH of condensate can be lowered,
The pH of the drain water of the high-pressure feed water heater can be made relatively high, copper-based materials can be used for the condenser tube group, and the water generated from the heating pipes and drain piping of the high-pressure feed water heater can be made relatively high. corrosion products can be reduced.

Furthermore, it is known that stainless steel materials (for example, 5US304) are generally used as a means to reduce the generation of Fe9, and if all the heating tubes of the feed water heater are made of stainless steel, the generation of PE can be reduced. You can, but
Making the heating tube of the high-pressure water heater made of stainless steel means
Since the working internal pressure is high, the wall thickness of the heating tube must be increased, which poses technical and economical problems. In the embodiment of the present invention, by using stainless steel for the low-pressure feed water heater, which has a low working internal pressure, it was possible to reduce the amount of PE generated from the heating tube of the low-pressure feed water heater.

Figure 3 (a) shows a change in Fe concentration in a thermal power plant using a conventional device, and Figure 3 (b) shows a diagram of changes in Fe concentration in a thermal power plant using a conventional device. It is a graph of Fe concentration change when the present invention is used, using stainless steel (8U8304) for the heater and carbon steel (8TB35) 11- for the high-pressure feed water heater.

As can be seen from FIG. 3(b), according to the present invention, the concentration of pe could be reduced to s, zppb at the inlet of the economizer.

〔Effect of the invention〕

According to the present invention, in a thermal power plant, it is possible to reduce corrosion products generated from the heating pipes and drain pipes of the feed water heater, within the range where copper-based materials can be used for the pipe group of the condenser. , the lifespan of plant equipment can be extended, and the efficiency of power generation plants can be increased.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention. Figure 2 shows the conventional device.
FIG. 3(a) shows a change in concentration of Fe according to a conventional example, and FIG. 3(b) shows a change in concentration of F6 according to an embodiment of the present invention. 1...Turbine, 2...Condenser, 88~8D...
Low pressure feed water heater, 9... deaerator, 13A-13C...
・High pressure water heater, 15...boiler, 18A to 18C
...High pressure water heater drain system, 20...Water quality treatment agent injection device.

Claims (1)

[Claims] 1. A condenser that condenses steam flowing out of a turbine, a pump that sends out this condensate, a low-pressure feedwater heater that heats this condensate, a high-pressure feedwater heater, and this high-pressure A thermal power plant comprising: a boiler that evaporates feedwater preheated by a feedwater heater and supplies steam to the turbine; and a means for supplying steam extracted from the turbine to the feedwater heater, wherein the high-pressure feedwater heater means for injecting drain water between the low pressure feed water heater and the high pressure feed water heater;
A means for supplying a first water treatment agent to the upstream side of the low pressure feed water heater, and a means for supplying a second water treatment agent to the drain system, the pH of the drain water being controlled by the low pressure feed water heater. A corrosion prevention device for a thermal power plant, characterized in that the pH value is higher than that of flowing feed water. 2. In claim 1, the high-pressure feedwater heater is composed of a plurality of heaters connected in series, and the means for supplying the second water treatment agent is located on the boiler side. A thermal power generation plant characterized by being connected to the drain system piping of the heater. 3. The corrosion prevention device for a thermal power plant according to claim 2, wherein the means for supplying the second water treatment agent is connected to the body side of the heater located on the boiler side. . 4. The corrosion prevention device for a thermal power plant according to claim 1, characterized in that ammonia is used as the first and second water treatment agents. 5. In claim 1, the heating tubes of the low-pressure feed water heater are made of stainless steel, the heating tubes of the high-pressure feed water heater are made of carbon steel, and the tube group of the condenser is made of copper or titanium. A corrosion prevention device for a thermal power plant, which is characterized by: 6. The thermal power plant according to claims 1 to 5 has steam conditions of (538°C, 246 kg/cm
^2) A corrosion prevention device for a thermal power plant, characterized in that it is a supercritical pressure thermal power plant or a thermal power plant in which steam conditions are further increased in temperature and pressure.