JPH0539282Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a variable pressure boiler having a vertical tube water cooling wall, and is particularly applicable to a variable pressure boiler having a vertical pipe water-cooled wall.
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[Conventional technology]

In recent years, large-capacity thermal power plants have been constructed to meet the rapidly increasing demand for electricity, but these boilers operate at variable pressure from ultra-supercritical pressure to subcritical pressure in order to obtain high power generation efficiency even at partial loads. That is required.

This is a feature of recent electricity demand, as nuclear power generation has grown and nuclear power generation has become more stable. Nuclear power generation is always operated at full load and is used for base load, while thermal power generation is meeting the demand for electricity. In response, there is a shift to thermal power plants that handle intermediate loads.

Thermal power plants that handle this intermediate load are rarely operated at full load;
The so-called daily start/stop operation is performed, such as increasing and decreasing the load to % load, 50% load, and 25% load, or stopping operation.

In this way, when thermal power generation is operated at partial load, the pressure is changed according to the load.
By using a variable pressure boiler that operates in the so-called ultra-supercritical pressure region at full load and in the subcritical pressure region at partial load, the power generation efficiency at partial load can be improved by several percent.

FIG. 3 is a water supply system diagram in a conventional constant pressure boiler.

In Figure 3, 1 is a water supply main pipe that leads water supply to the boiler, and this water supply main pipe 1 includes a water supply control valve 2 that adjusts the water supply amount to the boiler, a water supply flow meter 3 that measures the water supply amount, and an orifice valve in front of the water supply main pipe 1. A pressure gauge 4 is arranged.

The water supply further passes through water-cooled wall distribution pipes 5a-5n, manual orifice valves 6a-6n, pressure gauges 7a-7n after the orifice valves, and flows into water-cooled pipes 10a-10n to the inlets of water-cooled walls 8a-8n and pipes 9a-9n, To the outlet tubes 11a to 11n, connecting pipes 12a to 12n
flows to. Note that 13a to 13n are water-cooled wall metal thermometers.

However, since the conventional constant pressure boiler operates in a subcritical pressure region or a supercritical pressure region, manual orifice valves 6a to 6 installed in the water cooling wall distribution pipes 5a to 5n are required.
It was also possible to deal with n. However, in a variable boiler that changes from the subcritical pressure region to the ultra-supercritical pressure region,
Especially in the subcritical pressure region, the difference in the specific volume of steam and saturated water is large, and even if a small amount of steam is mixed in, the water cooling wall 8a~
The water cooling wall 8a~ inhibits the flow of internal fluid within 8n.
Increase the metal temperature of 8n. For this reason, manual orifice valves 6a to 6n for water cooling wall distribution pipes 5a to 5n.
The flow rate is adjusted by means of orifice valves 6a to 6.
With n, it takes time to finely adjust the internal imbalance, and at the same time, it is not possible to follow changes in state quantities that change moment by moment. At the same time, unstable flow occurs in the subcritical pressure region, and the opening degrees of the manual orifice valves 6a to 6n are adjusted in this state, but if high load operation is performed in the ultrasupercritical pressure region, the Although this solves the problem of balance, it has the disadvantage of causing more pressure loss than necessary.

In addition, in conventional constant pressure boilers in the subcritical pressure region or supercritical pressure region, manual orifice valves 6a to 6 are used to optimize the metal temperature of the water-cooled wall tubes 10a to 10n.
However, in a vertical water-cooled wall boiler with a wide range of pressure change, it is almost impossible to use manual orifice valves 6a to 6n.

[Problem that the invention attempts to solve]

The present invention attempts to eliminate such conventional drawbacks, and its purpose is to be able to adjust the water supply flow rate by following the changes in state quantities that change from moment to moment even during DSS operation. The objective is to obtain a boiler device that can maintain the water-cooled wall metal temperature appropriately.

[Means for solving problems]

In order to achieve the above-mentioned purpose, the present invention installs an automatic orifice valve in the water cooling wall distribution pipe of the vertical water cooling wall,
In addition to the water supply flow rate distribution signal from the water supply flow rate command that opens and closes this automatic orifice valve, there is also a water supply amount correction signal based on the flow rate difference from the orifice valve differential pressure detection circuit and the orifice valve opening degree detection circuit, and the load detection circuit and water cooling wall metal temperature. The water supply amount correction signal based on the temperature difference from the detection circuit is added to open and close the automatic orifice valve.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a water supply system diagram according to an embodiment of the present invention, and FIG. 2 is a typical control system diagram of the water supply system.

In FIG. 1, numerals 1 to 4 and numerals 6 to 13 indicate the same parts as the conventional ones.

14a to 14n are automatic orifice valves provided in the water cooling wall water pipes 5a to 5n, 15 is a water supply flow rate distribution signal from a water supply flow rate command, 16 is an orifice valve differential pressure detection circuit, 17 is an orifice valve opening detection circuit, 18
19 is a load detection circuit, 20 is a water-cooled wall metal temperature detection circuit, and 21 is a load detection circuit 19 and a water-cooled wall. A water supply flow rate correction signal based on the temperature difference is sent from the metal temperature detection circuit 20, and 22 is an orifice valve opening setting circuit.

In such a configuration, the flow of water from the main water supply pipe 1 is the same as that shown in FIG.

The feature of the present invention is that the flow coefficient (determined by the opening characteristic of the orifice valve) CV value of each automatic orifice valve 14a to 14n in the circuit of the boiler water cooling wall 8a to 8n is also the resistance value of the entire circuit. automatically controlled by linking it with the water supply flow rate. When distributing the total water supply flow rate to each circuit, the opening degree of each automatic orifice valve 14a to 14n is set while balancing all the circuits in order to ensure an appropriate temperature of the water cooling wall metal. That is, the total water supply amount is distributed according to the degree of circuit necessity of each of the water cooling walls 8a to 8n (so that the outlet temperature of each water cooling wall is within the target temperature). In other words, if the water supply flow rate decreases as a whole, it becomes easier to flow only to a specific circuit, but in this case, the opening degrees of the automatic orifice valves 14a to 14n of all circuits are adjusted slightly to compensate for the decreased water supply flow rate. I moved it to the open position and balanced each circuit in that state.

That is, the automatic orifice valves 14a to 14n are set by the orifice valve setting circuit 22 by adding the water supply flow rate correction signal 18 based on the flow rate difference and the water supply flow rate correction signal 21 based on the temperature difference to the water supply flow rate distribution signal 15. It was designed so that it could be opened and closed.

As a result, the vertical water cooling wall 8a of the transformer boiler
The metal temperature of 8n can also be properly kept within the target value.

Hereinafter, a representative example of the control system will be explained using FIG. 2.

The water supply flow rate signal 24 from the water supply command 23 is a total water supply flow rate signal flowing through the circuits of each water wall, and this water supply flow rate signal 24 is converted through a multiplier 25 into a water supply flow rate distribution signal 15 for each circuit. The converted water supply amount distribution signal 15 is output as an automatic orifice valve opening signal 27 through a function generator 26, and is transmitted via an adder 28 to the automatic orifice valves 14a to 14n. On the other hand, the generator output command signal 29 from the load detection circuit 19 is passed through a function generator 30 to create a temperature target signal 31 for each water wall circuit, and the water cooling wall metal temperature detection circuit 20 generates a temperature target signal 31 for each water wall circuit.
The difference between the measured metal temperature signal 32 and the measured metal temperature signal 32 is transmitted to the adder 28 through the deviation proportional integrator 33 as the water supply flow rate correction signal 21 based on the temperature difference.

The automatic orifice valve front and rear differential pressure actual measured signal 34 detected by the orifice valve differential pressure detection circuit 16 passes through the square root calculation unit 35, and then the automatic orifice valve front and rear differential pressure square root signal 36 and the orifice valve opening degree detection circuit 17
The automatic orifice valve opening signal 37 from the multiplier 3
8 to calculate the amount of water passing through each circuit. This automatic orifice valve passing water supply amount calculation signal 39 and the water supply flow rate distribution signal 1 from the multiplier 25
5 is obtained from the calculator 40, and this flow rate difference signal 4
1 is passed through the multiplier 42 as the water supply amount correction signal 18 based on the flow rate difference, and is transmitted to the adder 28.

In this way, in order to add the water supply flow rate correction signal 21 based on the temperature difference and the water supply amount correction signal 18 based on the flow rate difference to the automatic orifice valve opening signal 27 to obtain the control signal 43, water is supplied by the automatic orifice valves 14a to 14n. The amount is automatically corrected, and the optimal water supply is always distributed even during DSS operation, so the metal temperature of the water cooling wall becomes uniform.

[Effect of the invention]

This invention installs an automatic orifice valve in the water cooling wall distribution piping of a vertical water cooling wall, and receives the water supply flow rate distribution signal from the water supply flow rate command that opens and closes this automatic orifice valve from an orifice valve differential pressure detection circuit and an orifice valve opening degree detection circuit. The water supply amount correction signal based on the flow rate difference between Even if the variable pressure boiler changes, the water supply flow rate can be adjusted accordingly, and the temperature of the water-cooled wall metal can always be maintained at an appropriate level.

In a variable pressure operating boiler as in the present invention, especially when the load is partial (low load), the flow rate passing through the water-cooled pipes and the boiler differential pressure decrease, and as a result, the flow state of water in the pipes becomes unstable. Furthermore, due to the balance of heat absorption characteristics within the furnace, including variations in the state of adhesion of air bubbles on the inner surface of each water-cooled tube, the metal temperature of the water-cooled tube at a specific location may rise abnormally, causing a phenomenon that exceeds the strength of the tube. Occur.

Furthermore, due to an imbalance in heat absorption characteristics, a temperature difference occurs between adjacent water-cooled pipes, which may result in damage due to stress or the like.

Therefore, the present invention aims to reduce the local temperature rise due to the difference in the distribution of heat absorption within the furnace, as well as the temperature rise due to the unbalanced flow of water in the pipes.
Suppression is achieved by adding a water supply amount correction signal based on the temperature difference from the load detection circuit and water cooling wall metal temperature sensor to the original water supply flow rate distribution signal for each water cooling pipe, and controlling the automatic orifice valve. It is something.

[Brief explanation of the drawing]

Fig. 1 is a water supply system diagram of a variable pressure boiler according to an embodiment of the present invention, Fig. 2 is a typical control system diagram of the water supply system of Fig. 1, and Fig. 3 is a water supply system diagram of a conventional constant pressure boiler. . 8a to 8n...Vertical water cooling wall, 14a to 14n...
...Automatic orifice valve, 15... Water supply flow rate distribution signal, 16... Orifice valve differential pressure detection circuit, 17...
... Orifice valve opening detection circuit, 18 ... Water supply amount correction signal, 19 ... Load detection circuit, 20 ... Water cooling wall metal temperature detection circuit, 21 ... Water supply amount correction signal.

Claims (1)

[Scope of utility model registration request] In a variable pressure boiler with a vertical pipe water-cooled wall that operates in a subcritical pressure region to an ultra-supercritical pressure region,
An automatic orifice valve is provided in the water cooling wall distribution pipe of the vertical water cooling wall, and the flow rate from the orifice valve differential pressure detection circuit and the orifice valve opening degree detection circuit is applied to the water supply flow rate distribution signal from the water supply flow rate command that opens and closes the automatic orifice valve. A transformer boiler device characterized in that an automatic orifice valve is opened and closed by adding a water supply amount correction signal based on the difference and a water supply amount correction signal based on the temperature difference from a load detection circuit and a water-cooled wall metal temperature detector.