JPH0694208A - Water level controller for deaerator - Google Patents

Abstract

PURPOSE:To obtain a water level controller for a deaerator in which a water level of a storage tank can be held in a suitable range even if there is an abrupt load change by providing a subtracter for calculating to compare a temperature of a water level of the tank of the deaerator with condensate flowing to the deaerator, and a calculator for operating an auxiliary steam regulating valve. CONSTITUTION:A temperature of a water level of a storage tank 8 of a deaerator 6 is calculated to be compared with a temperature of condensate flowing to the deaerator 6 thereby to operate an auxiliary steam regulating valve 15 by using a PI calculator 17. That is, when a temperature of the tank 8 of an initial stage in which a variation in a water level of the tank 8 with evaporation in the tank 8 occurring when a rated load is transferred to a predetermined independently operating load as a starting point occurs at the time of evaporation and a temperature of condensate flowing to a deaeration chamber 7 are detected by a condensate temperature detector 13, calculated to be compared to obtain a change rate and the rate becomes a standard value or more, a deaerator temperature valve 15 is operated. Thus, even if there is an abrupt load change, a water level of the tank can be held in a suitable range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deaerator water level control device in a power plant or the like.

[0002]

2. Description of the Related Art Generally, in a steam turbine plant, the materials of equipment constituting the plant are made of carbon steel, low alloy steel or alloy steel, and non-condensable gases such as oxygen and carbon gas remain dissolved in the condensate. If so, it causes secondary damage due to equipment corrosion, damage, or corrosion products. These corrosion,
A deaerator is installed to prevent damage and removes non-condensable gases such as oxygen and carbon gas. The structure of a general deaerator is shown in FIG.

The deaerator is composed of a deaeration chamber and a water storage tank, and the condensate flowing in the deaeration chamber is sprayed and atomized by a spray valve 18. Diffusion degassing is performed by heat exchange by direct contact with turbine bleed air or auxiliary steam that flows into the sprayed and atomized condensate from the steam inlet. Further, the condensate is distributed by the distribution box 19 and the distribution tray 20 and flows down while meandering. At this time, the second deaeration is performed by being agitated by the steam flowing in and rising from the steam inlet. The non-condensed gas degassed in this way is continuously discharged to the atmosphere from the vent 21 in the upper part of the degassing chamber.

The water storage tank is a container for storing condensed water degassed in the degassing chamber, and is connected to the degassing chamber by a downcomer pipe and a pressure equalizing connecting pipe to constantly mix degassed condensate water with water in the water storage tank. It is in equilibrium and is maintained at the relaxation temperature of the deaeration chamber pressure.

Further, the water storage tank stores an equivalent amount of the total water supply for 3 to 5 minutes with respect to the pump installed on the downstream side so that stable water supply can be performed at the time of fluctuation of the water supply flow rate or emergency stop of the plant. .

Further, a water level control device for controlling the water level of the water storage tank and a temperature control device for controlling the temperature of the deaeration chamber are provided. Deaerator water level control (water tank water level control) adjusts the condensate flow rate flowing into the deaeration chamber by opening and closing the deaerator water level control valve installed in the condensate line according to the water level signal of the water tank. It is done by.

The deaerator temperature control (deaeration chamber temperature control) is performed by opening and closing a deaerator temperature control valve installed in the turbine extraction or auxiliary steam line according to the temperature signal of the deaeration chamber. This is done by adjusting the amount of steam flowing into. Fig. 2 shows a general system of condensate, water supply, steam system including deaerator and pump, deaerator water level control, and deaerator temperature control system. The steam that has finished its work in the steam turbine 1 is guided to the condenser 2 and becomes condensed water.

This condensate is boosted by a condensate pump 3 installed on the outlet side of the condenser 2, and passes through a deaerator water level control valve 4 and a low pressure feed water heater 5 to a deaerator deaeration chamber 7 (hereinafter Water is sent to the deaeration chamber). In the degassing chamber 7, as described above, the condensate is heated and degassed, the non-condensed gas is released to the atmosphere, and stored in the deaerator water tank (hereinafter referred to as the water tank) as water supply. The stored water supply is sent to the boiler 11 via the water supply pump 9 and the high-pressure water supply heater 10.

The steam for heating deaeration extracts a part of the steam of the turbine, and when the turbine is stopped, the extracted steam cannot be used. Therefore, a steam source is supplied from a separate auxiliary steam line to the deaerator temperature control valve 15 Is supplied via.

In the system constructed as described above, the deaerator water level control is a controller for correcting the ratio between the detection signal from the temperature detector 13 attached to the water tank 8 and the condensate temperature detected by the condensate temperature detector 12. This is performed by sending a calculation signal from 14 and operating the deaerator temperature control valve 15 according to the calculation signal to adjust the auxiliary steam flowing into the low pressure feed water heater 5.

In such a system, when the load of the turbine is lowered from the rated load to the in-house isolated operation load due to a transmission line accident or the like, the steam amount of the turbine extraction air that is the heating steam source of the deaerator 7 is also reduced, and Will not be supplied. (The low-pressure feed water heater 5 is also not supplied.) Therefore, the diffusion deaeration by steam and the second deaeration by the distribution box and the distribution tray are also not performed, and the low-pressure water supply heater 5 is not supplied with steam either. The condensate temperature flowing into 7 gradually decreases, and cold condensate enters and the temperature of the deaeration chamber 7 decreases. On the other hand, the water tank 8 stores the supply water in which the pressure of the degassing chamber 7 is saturated before the load is lowered.

Therefore, the water supply in the water storage tank 8 evaporates until it becomes equilibrium with the pressure in the degassing chamber 7. (The pressure changes moment by moment, but it takes time because the temperature changes due to self-evaporation.)

The vapor thus evaporated flows into the deaeration chamber 7 through the pressure equalization connecting pipe and tries to maintain a pressure equilibrium state with the water storage tank 8. However, when the amount of steam increases, the vapor flows into the deaeration chamber 7 through the pressure equalization connecting pipe. The flow rate is changed to the choke flow state, and the pressure equilibrium state between the deaeration chamber 7 and the water storage tank 8 is further deteriorated, and the pressure of the deaeration chamber 7 becomes smaller than the pressure in the water storage tank 8. Therefore, the water supply to the deaeration chamber 7 temporarily stops flowing from the downcomer pipe to the water tank 8. The water supply to the water storage tank 8 is boosted by a water supply pump 9 installed downstream and is sent to the boiler every second.

As a result, the water level in the water storage tank 8 begins to drop, but when this water level drop is detected by the deaerator water level detector and falls below the standard water level, the deaerator water level control valve 4 is opened to perform deaeration and deaeration. The condensate flow rate flowing into the chamber 7 is increased.

Condensate flowing into the deaeration chamber 7 tries to flow from the downcomer pipe to the water storage tank 8 through the distribution box and the distribution tray, but the degassing chamber 7 and the water storage tank 8 are in a pressure unbalanced state. The water does not flow to the water tank 8 while it is in the water. Since there is no condensate inflow, the water level in the water storage tank 8 does not return to the standard water level, the deaerator water level control valve 4 is further closed, and the condensate flow rate increases.

When the deaeration chamber 7 is increasingly filled with water, the water level in the deaeration chamber 7 rises and the pressures in the deaeration chamber 7 and the water tank 8 are returning to an equilibrium state, the deaeration chamber 7 is supplied with water. It suddenly flows into the water tank 8 due to a natural head, and the water level of the water tank 8 rises.

This rise in water level causes a large rise in water level exceeding the standard water level in the water tank 8 and the high alarm water level. The water level in the water tank 8 generates a high alarm and the deaerator water level control valve 4 is fully closed. Condensed water may not be passed through the low-pressure feed water heater 5, which may damage the equipment.

[0018]

However, the following problems remain in the conventional water level control.

Due to a sudden change in load, the water supply in the water storage tank evaporates in order to maintain a pressure equilibrium state with the deaeration chamber, whereby the pressure equalizing connecting pipe becomes a choke flow state, and condensed water accumulates in the deaeration chamber and flows into the water storage tank. Without it, the water level in the water tank will drop. After that, when the pressures of the deaeration chamber and the water storage tank are about to return to the equilibrium state, the water supply accumulated in the deaeration room suddenly flows into the water storage tank by a natural drop, and the water level of the water storage tank rises rapidly.

As a result, the water level of the water storage tank gives a high alarm, the deaerator water level control valve is fully closed, and condensate is not passed through the low pressure feed water heater, which may damage the equipment. An object of the present invention is to obtain a deaerator water level control device that can keep the water level of a water tank in an appropriate range even when there is a sudden load change.

[0021]

The deaerator water level control device of the present invention is used as a deaerator water level control device in a power plant or the like to control the temperature of the deaerator water tank and the condensate temperature flowing into the deaerator. It has both a subtracter for performing a comparison operation and a calculator for operating the auxiliary steam control valve by this.

[0022]

As a result, the water level in the water tank can be maintained within an appropriate range even if there is a sudden change in load.

[0023]

FIG. 1 is a block diagram showing an embodiment of the present invention. 12 is a condensate temperature detector, 13 is a deaerator condensate temperature detector, 14 is a control device, 15 is a deaerator temperature control valve, 16 is a subtractor, and 17 is a PI calculator.

When the choke flow occurs in the pressure-equalizing connecting pipe, the water level of the water storage tank decreases, so the temperature change rates of the condensate temperature and the water storage tank temperature flowing into the degassing chamber are detected and calculated, and the change rate becomes a standard value or more. If so, the deaerator temperature control valve is operated to control the auxiliary steam flowing into the low-pressure feed water heater to change the temperature of the condensate and to control the rapid fluctuation of the water level in the water tank appropriately.

According to the configuration of the present invention, the fluctuation of the water level in the water storage tank caused by the evaporation phenomenon inside the water storage tank that occurs when the load shifts (falls) from the rated load to the in-house isolated operation load occurs during the evaporation phenomenon. The temperature of the water storage tank at the initial stage and the temperature of the condensate flowing into the degassing chamber are detected, and a comparison calculation is performed, and if the rate of change exceeds the standard value, the deaerator temperature control valve is operated to activate the degassing chamber and the water storage tank. It is possible to control the water level properly by keeping the pressure equilibrium state and suppressing the abrupt change of the water level in the water tank that occurs from the pressure unbalanced state.

[0026]

As described above, according to the present invention, the water level in the water storage tank can be maintained within an appropriate range even if there is a sudden load change.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional example.

FIG. 3 is an explanatory diagram of a deaerator.

[Explanation of symbols]

 1 Turbine 2 Condenser 3 Condensate Pump 4 Deaerator Water Level Control Valve 5 Low Pressure Water Heater 6 Deaerator 7 Deaeration Chamber 8 Deaeration Tank 9 Water Pump 10 High Pressure Water Heater 11 Boiler 12 Condensate Temperature Detector 13 Condensate temperature detector in deaerator 14 Controller 15 Deaerator temperature control valve 16 Subtractor 17 PI calculator

Claims (1)

[Claims] 1. As a deaerator water level control device in a power plant or the like, a subtractor for comparing and calculating the temperature of the deaerator water tank and the condensate temperature flowing into the deaerator, and an auxiliary steam control valve thereby A deaerator water level control device characterized in that it also has a computing unit to operate.