JPH06257964A - Condensed water flow rate controller - Google Patents

Abstract

PURPOSE:To improve controllability by a method wherein a condensed water flow rate control loop, which controls the flow rate distribution of condensed water passed through a low-pressure feed water heater and a low-pressure gas heater, a deaerator water level control loop, and a spillover control loop are controlled so as never to interfer to each other. CONSTITUTION:In a thermal power plant, a deaerator 1 is connected to the outlet port side of a low-pressure feed water heater 2. In this case, a condensed water flow rate controller 7 controls the sum of a plurality of flow rates of condensed water, passing through respective condensed water flow rate regulating valves 4, 5 related to the low-pressure feed water heater 2 and the low-pressure gas feed water heater 3, based on a deaerator water level (d) to keep the water level of the deaerator 1 in constant. Further, the plurality of distributing amounts of feed water for the low- pressure feed water heater 2 and the low-pressure gas feed water heater 3 are determined by a distributing amount determining process (e) and opening degree commands (a, b), which are outputted to respective condensed water flow rate regulating valves 4, 5, are outputted. In this case, the spillover regulating valve 6 of the low-pressure gas feed water heater 3 is controlled by a spillover controller 8, which has no relation directly to the control of steam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condensate flow controller for a thermal power plant.

[0002]

2. Description of the Related Art A conventional condensate flow rate control will be described with reference to FIG.

In a thermal power plant, a low pressure feed water heater 2
It is customary to install a deaerator water level control valve (LV-22) 20 at the inlet of and to control the condensate flow rate so as to keep the water level of the deaerator 1 constant.

In such a system, only the total amount of the condensate flow rate flowing into the deaerator 1 is controlled, and there is no means for performing distribution control when devices are connected in parallel to the low pressure feed water heater 2. .

[0005]

However, the conventional system as described above is a system for keeping the deaerator water level constant by controlling the total amount of condensate flow. It does not consider the condensate flow distribution control with the feed water heater and the spillover control of the low-pressure gas feed water heater.

An object of the present invention is to favorably perform condensate flow rate distribution control and low-pressure gas feed water heater spillover control without impairing the deaerator water level control function by controlling the total amount of condensate flow rate. The purpose is to obtain a condensate flow rate control device.

[0007]

The condensate flow rate control device of the present invention comprises a low-pressure feed water heater for exchanging heat between bleed air and condensate, and a low-pressure gas feed water heater for exchanging heat between boiler exhaust gas and condensate. Are connected in parallel, the condensate heat-exchanged by both is joined, then in a thermal power plant having a system that flows into the deaerator, and a spillover system of the low-pressure gas feed water heater,
The control loop that controls the flow rate distribution of condensate flowing through the low-pressure feed water heater and the low-pressure gas heater by the plant process amount, the control loop that keeps the deaerator water level constant, and the control loop that performs spillover control interfere with each other. The feature is that the control is performed in a coordinated manner without performing the above.

[0008]

As a result, the distribution control, the deaerator water level control, and the low pressure gas feed water heater spillover control can be satisfactorily controlled without interfering with each other.

[0009]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a plant system diagram showing an embodiment of the present invention.

The low-pressure feed water heater condensate flow rate control valve 4, the low-pressure gas feed water heater condensate flow rate control valve 5, and the low-pressure gas feed water heater spillover control valve 6 are arranged in such a manner that a plurality of control valves are not in series. Make sure that the movement of the control valve does not restrict others. In order to keep the water level of the deaerator 1 constant, it is necessary to control the total amount of the condensate flow rate flowing into the deaerator 1 by the deaerator water level d. Therefore, the sum of the condensate flow rates passing through the low pressure feed water heater condensate flow rate control valve 4 and the low pressure gas feed water heater condensate flow rate control valve 5 is controlled by the deaerator water level d.

On the other hand, the low-pressure feed water heater 2 and the low-pressure gas feed water heater 3 are determined by the process value e (specifically, load signal, outlet condensate temperature of the low-pressure gas feed water heater 3, etc.) for determining the distribution amount.
Determine the amount of condensate to be distributed.

From the above, by the condensate flow rate control device 7,
The low pressure feed water heater condensate flow rate control valve opening command a and the low pressure gas feed water condensate flow rate control valve opening command b are calculated and controlled.

The spillover flow rate of the low pressure gas feed water heater 3 is controlled by the low pressure gas feed water heater spillover controller 8 which is not directly related to the above control. The specific control target is the temperature of the boiler exhaust gas 9, the low-pressure gas feed water heater 3
It is the outlet condensate temperature.

The low-pressure feed water heater condensate flow rate control valve 4 and the low-pressure gas feed water heater condensate flow rate control valve 5 can be cooperatively controlled by the deaerator water level signal d and the distribution amount determining process value e. Enabled, water level of deaerator 1 and low pressure feed water heater 2
It is possible to satisfactorily control the distribution of the condensate flowing through the low pressure gas feed water heater 3 and the control of the spillover flow rate of the low pressure gas feed water heater 3 without interfering with each other. FIG. 2 is a system diagram in which the condensate flow control device according to one embodiment of the present invention is applied to a plant system. The low-pressure feed water heater condensate flow rate control valve 4 sets the deaerator water level g to N.V. W. The control is performed by the control loop 11 that keeps L.

The low-pressure gas feed water heater condensate flow rate control valve 5 is
The water level of the deaerator is g. W. The control loop 12 for keeping L + ε and the condensate temperature h at the outlet of the low-pressure gas feed water heater are set to the deaerator water tank temperature f.
The output of the control loop 10 for controlling the temperature lower by α ° C. is selected by the low value selection circuit 15 and the control is performed.

Low pressure gas feed water heater spillover control valve 6
Is the output of the control loop 13 that controls the low-pressure gas feed water heater outlet condensate temperature h to a temperature that is β ° C. (β <α) lower than the deaerator water tank temperature f and the rise suppression loop 14 of the boiler exhaust gas temperature i. The high value selection circuit 16 selects and controls.

In this embodiment, in a normal state, the control loop controls the condensate temperature h at the outlet of the low-pressure gas feedwater heater with a set value which is a temperature of the water tank temperature f of the deaerator 1 reduced by α ° C. 10, and drive the low pressure gas feed water heater condensate flow rate control valve 5.

If the water level in the deaerator 1 rises for some reason, the control loop 12 causes the low pressure gas feed water heater condensate flow rate control valve 5 to change the deaerator water level to N.V. W. It is controlled so as to be L + ε. Since this control valve normally performs the temperature control described above, the output of each control loop is set to the low value selection circuit 15
Select by.

At this time, the amount of water passing through the low pressure gas feed water heater 3 decreases and the outlet condensate temperature rises. In this case, the control loop 13 degass the outlet condensate temperature of the low pressure gas feed water heater 3. The low-pressure gas feed water heater spillover control valve 6 is controlled so that the temperature is kept at β ° C. lower than the tank storage tank temperature f. Since this control valve controls the increase in the temperature i of the boiler exhaust gas 9, the output of each control loop is set to the high value selection circuit.
Select by 16.

According to this embodiment, the deaerator water level control, the efficient distribution control of the condensate, and the spillover control of the low pressure gas feed water heater can be realized as a coordinated system without mutual interference. The temperature control loop 10 shown in FIG. 2 can also be used as a control loop 17 for calculating the control valve opening from the load signal as shown in FIG.

Further, as shown in FIG. 4, the low-pressure feed water heater 2
A deaerator water level control valve 18 is installed between the confluence point of the condensate pipe through which the low pressure gas feed water heater 3 has passed and the deaerator 1, and the low pressure feed water heater condensate flow rate control valve 4 and the low pressure gas It is also possible to determine the condensate flow distribution ratio by the control loop 19 with the two control valves of the feed water heater condensate flow control valve 5 and keep the water level of the deaerator 1 constant by the deaerator water level control valve 18. Is. Control loop of Figure 4
In 19, the condensate distribution ratio is determined by the outlet temperature h of the low-pressure gas feed water heater, but it is also possible to use a load element.

[0022]

As described above, according to the invention, the distribution control of the condensate water flow amount between the low pressure feed water heater and the low pressure gas feed water heater, the deaerator water level control, and the low pressure gas feed water heater spillover control are performed. It becomes possible for the three parties to satisfactorily control without interfering with each other, and operation control of a plant having the piping system shown in the present invention, such as an exhaust gas reburn type combined cycle plant and a pressurized fluidized bed boiler type combined cycle plant, can be realized. .

[Brief description of drawings]

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

FIG. 2 is a system diagram in which a condensate flow control device according to an embodiment of the present invention is applied to a plant system.

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

FIG. 4 is a system diagram showing another embodiment of the present invention.

FIG. 5 is a system diagram showing a conventional example.

[Explanation of symbols]

1 ... Deaerator, 2 ... Low pressure feed water heater, 3 ... Low pressure gas feed water heater, 4 ... Low pressure feed water heater Condensate flow rate control valve, 5 ... Low pressure gas feed water heater Condensate flow rate control valve, 6 ... Low pressure gas Feed water heater spillover control valve, 7 ... Condensate flow rate control valve, 8 ... Low pressure gas feedwater heater spillover control device, 9 ... Boiler exhaust gas, 10 ... Low pressure gas feedwater outlet condensate temperature control group, 11 ... Deaerator Control group, 12 ... Deaerator control group (backup at high water level), 13 ... Low pressure gas feed water heater outlet condensate temperature control group, 14 ... Boiler exhaust gas temperature rise suppression control group, 15 ... Low value selection circuit, 16 ... High value selection circuit, 17 ... Low pressure gas feed water heater condensate flow control valve control group, 18 ... Deaerator water level control valve, 19 ... Condensate flow distribution control group, 20 ... Deaerator transition control valve.

Claims (2)

[Claims] 1. A low-pressure feed water heater for exchanging heat of condensate with extracted air and a low-pressure gas feed water heater for exchanging heat of condensate with boiler exhaust gas are connected in parallel, and condensate heat-exchanged by both is In a thermal power plant with a system that flows into a deaerator after merging and a spillover system of a low-pressure gas feedwater heater, control that performs flow rate distribution control of condensate passing through the low-pressure feedwater heater and low-pressure gas heater by plant process amount A condensate flow control device characterized in that a loop, a control loop for keeping a deaerator water level constant, and a control loop for performing spillover control cooperate with each other without interfering with each other. 2. The low-pressure feed water heater does not have a control valve on the primary side of the branch point of the condensate pipe between the low-pressure feed water heater and the low-pressure feed water heater, and the low-pressure feed water heater is A control valve for controlling the condensate flow rate is placed between the branch point of both feed water heaters and the confluence point, and on the low pressure gas feed water heater side, between the branch point of the spillover system and the confluence point of both feed water heaters. A condensate flow control device characterized by the above.