JPH06129604A - Method for water supplying processing of heat power plant - Google Patents

Abstract

PURPOSE:To prevent a concentration of resolved oxygen kept within boiler supplied water from being increased in a water supplying and processing method for feeding oxygen in the boiler supplied water and processing oxygen processing. CONSTITUTION:A lower part of a deaerator 7 to which condensed water got from a condenser 1 is provided with a deaerator water storing tank 9. Oxygen for use in oxygen processing is fed from an oxygen feeding device 17 into the condensed water at a location where oxygen is out of a desalting device 4. A resolved oxygen meter 21 is connected to a water supplying pipe 10 at an outlet port of the exhausting device water storing tank 9 by a sample collecting pipe 20. Concentration of resolved oxygen measured by the meter is converted into an electrical signal by a converter 22 and sent to a system for controlling a degree of opening of a vent valve 8 of the deaerator 7. The vent valve 8 of the deaerator 7 is opened when the concentration of resolved oxygen measured by the resolved oxygen meter 21 is increased more than a certain predetermined value and in tune the vent valve 8 is closed when the concentration of the resolved oxygen is decreased lower than the predetermined value by a predetermined value. With such an arrangement as above, the concentration of the resolved oxygen in the supplied water is kept at the desired value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed water treatment method for treating feed water with oxygen in a thermal power plant.

[0002]

2. Description of the Related Art In oxygen treatment, which is one of the methods of water supply treatment for thermal power plants, oxygen is injected in order to protect the equipment and pipes that make up the system from corrosion and to reduce the corrosion products carried into the boiler. ing. A conventional water supply treatment method using oxygen treatment will be described with reference to FIG.

In FIG. 2, reference numeral 1 is a condenser, and a turbine (not shown) is installed above the condenser. One side of the condenser pipe 2 is connected to the lower part of the condenser 1, and the condenser pipe 3 is connected to the condenser pipe 2 in this order from the condenser 1 side.
The condensate booster pump 5 and the low-pressure heater 6 are arranged, and the other side of the condensate pipe 2 is connected to the deaerator 7.

A deaerator vent valve 8 for releasing the deaerated gas into the atmosphere is installed above the deaerator 7. A deaerator water storage tank 9 is connected below the deaerator 7. One side of the water supply pipe 10 is connected to the lower part of the deaerator water tank 9,
A water supply pump 11 and a high-pressure heater 12 are arranged in the water supply pipe 10, and the other side of the water supply pipe 10 is connected to a boiler 14 via a economizer 13.

The steam extracted from a turbine system (not shown) is introduced into the high-pressure heater 12 by a high-pressure extraction pipe 15, and the steam heat-exchanged with the feed water flowing through the water supply pipe 10 in the high-pressure heater 12 is drained, and the high-pressure heater 12 is discharged. Is collected in the deaerator water storage tank 9 by the high-pressure heater drain pipe 16 connected between the deaeration water storage tank 9.

As the water supply treatment facility, the oxygen injection pipe 1 is connected to the condensate pipe 2 on the outlet side of the desalination device 4 from the oxygen injection device 17.
8 is connected. The adjustment of the oxygen injection amount from the oxygen injection pipe 18 is controlled by the oxygen injection control valve 19 provided in this pipe line, and a predetermined amount of oxygen is supplied to the system.

[0007]

In the water supply treatment apparatus configured as described above, when the water supply treatment by oxygen treatment is performed as the water supply treatment, the amount of oxygen to be injected depends on the effect of the present water treatment method. It is necessary to keep the dissolved oxygen concentration in the inlet water supply of the economizer 13 within the range of 20 to 200 μg / liter of the reference value. For this reason, a control method of adjusting the opening of the oxygen injection control valve 19 in proportion to the feed water flow rate is usually adopted as a means for adjusting the oxygen injection amount.

As a method of using the deaerator 7, the deaerator is used so that the oxygen injected for the oxygen treatment is not deaerated by the deaerator 7 and released from the deaerator vent valve 8 to the atmosphere. The vent valve 7 is fully closed and the water quality is controlled so that the appropriate amount of dissolved oxygen described above exists in the feed water and the boiler water on the downstream side from the deaerator water storage tank 9.

However, in this oxygen injection amount adjusting system, the internal pressure and temperature of the deaerator 7 and the deaerator water tank 9 are changed when the operating state of the plant changes from the rated load operation to the low load operation. The oxygen partial pressure in the vessel changes due to the decrease, and the dissolved oxygen concentration in the liquid phase side, that is, the outlet feed water of the deaerator water storage tank 9 rises, and it becomes impossible to maintain it within the range of the reference value. Become.

Further, in each load operation, the amount of high-pressure heater drain collected in the deaerator water storage tank 9 changes,
In the low load operation in which the flow rate decreases, this is a factor that accelerates the phenomenon of increasing the dissolved oxygen concentration of the outlet feed water of the deaerator water storage tank 9 and makes the dissolved oxygen concentration increase remarkable.

In order to prevent the phenomenon of rising dissolved oxygen concentration, the method of adjusting the amount of oxygen at the injection point is such that the oxygen injection is intermittent or the dissolved oxygen in the condensate system falls below the lower limit value. However, in the conventional oxygen injection control system, it is impossible to properly inject oxygen in response to load fluctuations in the plant.

It is an object of the present invention to provide a feed water treatment method for a thermal power plant that does not have the above-mentioned problems found in conventional methods.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a water treatment method for a thermal power plant for injecting oxygen into a boiler feedwater flowing through a water supply system including a deaerator and a deaerator water storage tank to perform oxygen treatment. In order to solve the above problem, the dissolved oxygen concentration in the feed water exiting the deaerator water storage tank is detected, and the vent valve of the deaerator is opened and closed according to the detected concentration to maintain the detected concentration at a predetermined value. Adopt the method of doing.

[0014]

Since the method described above is adopted in the oxygen treatment of the present invention, the vent valve of the deaerator is controlled by the dissolved oxygen concentration detected by the dissolved oxygen meter installed in the water supply pipe on the outlet side of the deaerator water tank. The dissolved oxygen concentration of the feed water can be adjusted within a predetermined range by automatically controlling the opening.

As one of the automatic control methods of the deaerator vent valve, the vent valve of the deaerator is opened when the oxygen concentration detected by the dissolved oxygen meter exceeds a predetermined first value. ,
The vent valve is controlled to close when the detected concentration reaches a predetermined second value smaller than the first value.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the embodiment shown in FIG. Note that, in FIG. 1, the same reference numerals are given to the equipment and piping portions common to those shown in FIG. 2 used to describe the conventional water supply treatment method in a thermal power plant, and the description thereof will be omitted. In FIG. 1, a sampling pipe 20 is connected to the water supply pipe 10 on the outlet side of the deaerator water storage tank 9, and a dissolved oxygen meter 21 is connected to the sampling pipe 20.

The dissolved oxygen meter 21 contains a converter 22 for converting the measured dissolved oxygen concentration into an electric signal. The electrical signal thus detected and converted is sent to the opening control system of the deaerator vent valve 8 by the conductor 23.

That is, the opening degree of the deaerator vent valve 8 in the normal operation is fully closed to prevent the oxygen supplied from the oxygen injection device 17 and separated in the deaerator 7 from being released to the atmosphere. However, due to the above factors when the load drops,
When the dissolved oxygen concentration of the outlet feed water of the deaerator water storage tank 9 rises, it is detected by the dissolved oxygen meter 21, and the deaerator vent valve 8 is automatically opened via the converter 22 to open the deaerator. Oxygen in the gas phase portion 7 is released to the atmosphere.

When the dissolved oxygen concentration of the outlet feed water of the deaerator water storage tank 9 is lowered by this operation, the deaerator vent valve 8 is closed in the same manner to adjust the dissolved oxygen concentration in the feed water within the range of the reference value. To do.

The reference value of dissolved oxygen in the feed water in the oxygen treatment is 20 to 200 μg / liter, but when the present invention is applied so as not to deviate from this range, for example, a deaerator vent valve with a dissolved oxygen concentration of 100 μg / liter. Open 8 and 50μ
The dissolved oxygen meter 21 is operated with a set value for control that is closed at g / liter, and the dissolved oxygen concentration of the outlet feed water of the deaerator water storage tank 9 is within the standard value range even if the load changes significantly. It is now possible to hold.

Although the water supply treatment method according to the present invention has been specifically described above, it goes without saying that the present invention is not limited to this. The point is to detect the dissolved oxygen concentration in the feed water leaving the deaerator water storage tank and control the opening / closing of the vent valve of the deaerator so that the concentration falls within a predetermined value.

[0022]

As described above, the method for controlling the dissolved oxygen concentration of feed water in the oxygen treatment of the present invention is a method for adjusting the dissolved oxygen of feed water of a thermal power plant in which load fluctuations are frequent and whose fluctuation range is large. , The dissolved oxygen concentration of the feedwater at the outlet of the deaerator water tank is continuously detected and monitored by a dissolved oxygen meter, and the opening of the deaerator vent valve is automatically adjusted according to the detected concentration, so that the feedwater is always dissolved It is possible to keep the oxygen concentration within an appropriate range and achieve the intended purpose.

[Brief description of drawings]

FIG. 1 is a flow sheet diagram showing a water supply treatment method for a thermal power plant according to the present invention.

FIG. 2 is a flow sheet diagram showing a water supply treatment method in a conventional thermal power plant.

[Explanation of symbols]

 1 Condenser 2 Condensate Pipe 7 Deaerator 8 Deaerator Vent Valve 9 Deaerator Water Tank 10 Water Supply Pipe 17 Oxygen Injector 18 Oxygen Injector 20 Sampling Pipe 21 Dissolved Oxygen Meter 22 Converter

Claims (1)

[Claims] 1. A feedwater treatment method for a thermal power plant that injects oxygen into a boiler feedwater flowing in a water supply system including a deaerator and a deaerator water storage tank to perform oxygen treatment, and exits the deaerator water storage tank. A method for treating feedwater in a thermal power plant, which detects a dissolved oxygen concentration in feedwater and holds the detected concentration at a predetermined value by opening and closing a vent valve of the deaerator according to the detected concentration.