JPH0224882Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a control device for a multi-stage mixed pressure steam turbine.

[Technical background and problems of the invention]

A multi-stage mixed-pressure steam turbine is a steam turbine in which several types of surplus process steam lines with different steam conditions are connected to an intermediate stage of the steam turbine so that thermal energy of the mixed-pressure steam line can be effectively recovered.
In this type of mixed pressure steam turbine, in order to recover all of the excess steam, no steam control valve is installed on the pipe of the mixed pressure steam line to adjust the steam flow rate, and in case of an emergency, the steam to the steam turbine is Only a stop valve is provided to stop the flow.

Figure 2 shows a conventional example of this type of multi-stage mixed pressure steam turbine. Main steam generated from a boiler is introduced into the inlet of a steam turbine 2 via a main steam pipe 1, and the turbine rotor is rotated. Afterwards, it flows out from the exhaust pipe 3. A steam control valve 4 is installed on the main steam pipe 1, and its opening degree is controlled by a speed governor 5. Further, process steam lines 6, 7, 8 are provided in the intermediate stage of the steam turbine 2.
are connected, and a stop valve 9, is installed on each line.
10 and 11 are incorporated. In this way, the main steam supplied through the main steam pipe 1 and the mixed pressure steam supplied through the process steam lines 6, 7, and 8 rotate the driven machine 12, such as a generator, and generate output.

By the way, since the mixed pressure steam is surplus steam in the process steam line, it is desirable to recover all the surplus to the steam turbine from the viewpoint of improving the thermal coefficient of motion.

On the other hand, the flow rate of mixed pressure steam may fluctuate from moment to moment, and in such a case, the speed governor 5 senses the fluctuation and controls the opening/closing of the steam control valve 4 to direct the main steam to the steam turbine 2. The output of the steam turbine 2 is controlled by adjusting the amount of inflow. In other words, the entire amount of energy contained in the mixed pressure steam is recovered, and the deficit is made up by the main steam to adjust the output.

By the way, when lowering the load in order to stop the steam turbine, when the load drops to the output that can be produced only by mixed pressure steam, the steam control valve 4 will be fully closed, and below that, the steam turbine will be in an uncontrolled state. This creates a dangerous driving situation. Therefore, conventionally, when the load drops to a certain point, the stop valves 9, 10, 11 on the mixed pressure steam line are forcibly fully closed and the operation is switched to only control the steam control valve 4.
The steam control valve 4 further reduces the load so that it can be stopped safely.

In addition, when starting a steam turbine, the load is increased by first operating only the steam control valve 4, and when a certain load is reached, the stop valves 6, 7, and 8 of the mixed pressure steam line are manually operated. It has been fully opened and is transitioning to combined operation with main steam and mixed pressure steam.

However, when the stop valves of the mixed pressure steam line are manually controlled, the more the multi-stage mixed pressure turbine becomes, the more troublesome the operation of gradually opening and closing each stop valve becomes. If the manual operation speed is too fast, the load on the steam turbine will change suddenly. As described above, the control of a mixed pressure steam turbine tends to cause disturbances, and as a result, abnormalities in the steam line occur due to sudden changes in pressure on the process side. Also,
On the turbine side, there is a problem in that sudden changes in load cause severe fluctuations in the thermal stress of the casing, leading to fatigue failure of the casing. Additionally, if the required load on the steam turbine decreases without the operator noticing, and the required load drops below the output value that can be output using only mixed pressure steam, the steam control valve will be fully closed and the steam turbine will be in an uncontrolled state. It is dangerous.

[Purpose of invention]

Therefore, the purpose of this invention is to smoothly start and stop a multi-stage mixed-pressure steam turbine, and also to automatically control the mixed-pressure steam line without causing disturbance in response to changes in the required load on the steam turbine. An object of the present invention is to provide a control device for a multi-stage mixed pressure turbine that enables the control of a multi-stage mixed pressure turbine.

[Summary of the idea]

In order to achieve the above object, the present invention provides a multi-stage mixed pressure steam turbine in which the stop valve has its valve body spring-loaded in the valve closing direction by the spring force of a closing spring, and the stop valve is placed on the side opposing this spring force. A pressure oil supply line is connected, and a first three-way switching valve and an orifice are installed on this pressure oil supply line.
The three-way switching valve receives the comparator output signal, and operates so that the stop valve opens slowly in a region where the opening degree of the main steam regulating valve is larger than the set opening degree; In the region where the opening degree is smaller than the set opening degree, the switch is switched to the drain side and the stop valve operates to slowly close.Furthermore, a relay trip valve is installed between the stop valve and the first three-way switching valve. A second three-way switching valve is installed on the other pressure oil supply line that communicates with the relay trip valve, and when the trip or load is interrupted, the relay trip valve is switched to the drain side and the stop valve is quickly closed. It is characterized by this.

[Example of idea]

Hereinafter, an embodiment of a control device for a multi-stage mixed pressure steam turbine according to the present invention will be described with reference to FIG.

FIG. 1 shows an example in which the present invention is applied to a stop valve 9 of one of the process steam lines 6, 7 and 8. It goes without saying that the remaining stop valves 10 and 11 are similarly constructed. In this case, continuous and smooth load control is possible by gradually changing and setting the adjusting valve threshold value in the comparators provided in the stop valves 9, 10, and 11 of each line.

The stop valve 9 has a valve box 15 in which a valve port 14 is formed.
The valve port 14 is opened and closed by a valve body 16. A valve rod 17 is directly connected to the valve body 16, and a piston 18 at the end thereof is connected to the cylinder chamber 2 of a hydraulic cylinder 19.
It is contained within 0. A closing spring 21 is installed in the cylinder chamber above the piston 18, and its spring force always acts to push the valve body 16 down toward the valve port 14. Note that a detection rod 22 is directly connected to the piston 18,
The fully open position and fully closed position of the valve body 16 can be detected by microswitches 23 and 24.

An inlet port a is formed in the side wall of the cylinder 19 and opens into the cylinder chamber 20 below the piston 18.

In FIG. 1, reference numeral 25 indicates a relay trip valve, and this relay trip valve 25 is connected to the cylinder 26.
and a spool 28 which is spring-loaded to the right in the figure by a spring 27. A pressure oil supply line 30 from a pressure oil source 29 is connected to the inlet port b of the cylinder 26, while an outlet port c
and the inlet port a of the cylinder 19 are the pipe line 31
has been contacted. A first three-way switching valve 31 is installed on the pressure oil supply line 30, and ports d,
e and f can be selectively switched.
The first three-way switching valve 31 compares the set opening 32 and the actual opening 33 of the steam control valve 4 with a comparator 34, and sends the output signal to the pilot section 36 of the three-way switching valve 31 through a signal line 35. I'm starting to convey it. When the actual opening degree 33 of the steam control valve 4 is larger than the set opening degree 32, the three-way switching valve 31
ports d and e are in communication with each other, and pressure oil is supplied to port b of the relay trip valve 25 through the pressure oil supply line 30, and introduced from port c to port a through the pipe line 31, and the piston 18 is connected to the closing spring 2.
The piston 18 is pushed up against the spring force of 1, and the valve body 16 is moved in the valve opening direction.

On the other hand, an emergency oil line 38 is connected to port g of the relay trip valve 25, and pressure oil from a pressure oil source 39 is supplied through a second three-way switching valve 40. The second three-way switching valve 40 has three ports h, i, and j, and can communicate with the ports h and i by inputting either a trip signal 41 or a load shedding signal 42.

An orifice 44 is installed immediately before the inlet port d of the first three-way switching valve 31, while an orifice 46 is installed in the drain line 45. These orifices 44, 46 slow the flow of pressure oil on this pressure oil supply line.

Next, the mode of operation of the control device configured as described above will be explained in each case.

When starting a steam turbine: First, when the steam turbine is reset, hydraulic pressure is generated in the emergency oil line 38, and the three-way solenoid valve 4 is activated.
Relay trip valve 25 through ports h and i of 0
Pressure oil is supplied to port g, and the spool 28 is moved against the spring 27 to connect ports b and c. At this time, since the steam control valve 4 is closed, the signal from the comparator 34 is transmitted to the pilot section 36 of the three-way switching valve 31 through the signal line 35, thereby communicating ports e and f. Therefore, the pressure oil in the cylinder 19 is transferred to the pipe line 30, ports c and b, the pressure oil line 30 and the drain line 45.
The valve body 16 is discharged through the closing spring 21.
The fully closed state is maintained by the spring force.

Next, the steam control valve 4 begins to open, the steam turbine 2 is started, and the load is gradually increased, and when the valve opening of the steam control valve 4 exceeds the set degree, the comparator 3
The output signal from 4 disappears, and the three-way switching valve 31 connects ports d and e. Then, due to the throttling effect of the inlet orifice 44, pressure oil gradually flows into the cylinder chamber 20 from the port a through the pressure oil line 30, ports b and c, and the pipe line 31, and the piston 18
Push up to separate the valve body 16 from the valve port 14 and slowly open the valve fully. Therefore, steam is supplied from the process steam line 9 to the turbine intermediate stage without causing any disturbance.

When reducing the load on the steam turbine: When the steam control valve 4 begins to close and the valve opening reaches the set opening, a signal is output from the comparator 34 and ports e and f of the three-way switching valve 31 are brought into communication. Therefore, the pressure oil in the cylinder chamber 20 is
Orifice 4 of pipe line 31, ports c, b, pressure oil line 30, ports e, f, and drain line 45
It is gradually discharged through 6. As a result, valve body 1
6 is closed under the action of the spring force of the closing spring 21, the flow of mixed pressure steam into the turbine is gradually cut off, and thereafter the operation is shifted to only by controlling the opening of the steam control valve 4.

When a load interruption occurs In contrast to the gentle load fluctuation control by the first three-way switching valve 31, the second three-way switching valve 4 in an emergency
The operation of 0 is shown below. A load breakage signal 42 is input to the second three-way switching valve 40, causing ports i and j to communicate with each other, and the hydraulic pressure acting on the spool 28 disappears, causing ports c and k to communicate with each other. Then, the pressure oil in the cylinder chamber 20 is quickly discharged through the port a pipe line 31 and ports c and k, and the valve body 16 of the stop valve 9 is suddenly closed, stopping the introduction of mixed pressure steam. Note that when the turbine trip signal 41 is input to the three-way switching valve 40, the stop valve 9 is fully closed in the same manner.

[Effect of idea]

As is clear from the above description, according to the present invention, the first three-way switching valve is installed on the pressure oil supply line that opens the stop valve, and the valve opening degree of the steam control valve is in a region exceeding a set value. When the load increases, steam can be supplied from the process steam line to the intermediate stage of the turbine without causing disturbance, while the first three-way switching valve is automatically activated when the valve opening of the steam control valve is below the set value. By switching to the drain line, it is possible to slowly close the stop valve in the small opening range of the steam regulating valve and automatically switch to operation using only the valve opening control of the steam regulating valve without causing any disturbance. .

Further, even if the required load drops without the operator noticing, it is possible to smoothly shift to operation of only the steam control valve. Furthermore, by incorporating a relay trip valve and a second three-way switching valve, the stop valve can be automatically disconnected in the event of load interruption or turbine trip, thereby safely controlling the operation of the mixed pressure turbine. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a control device for a multi-stage mixed pressure steam turbine according to the present invention, and FIG. 2 is a diagram showing the multi-stage mixed pressure steam turbine. 1...Main steam pipe, 2...Steam turbine, 4...
Steam control valve, 6, 7, 8... Process steam line, 9, 10, 11... Stop valve, 16... Valve body,
19...Hydraulic cylinder, 20...Cylinder chamber, 2
1... Closing spring, 25... Relay trip valve.

Claims (1)

[Claims for Utility Model Registration] Main steam whose flow rate is controlled through a steam control valve on the main steam pipe is supplied to the inlet of the steam turbine, while steam under different steam conditions is supplied through a stop valve on the process steam line. In a multi-stage mixed pressure steam turbine configured to supply process steam to an intermediate stage of the steam turbine; A pressure oil supply line is connected to the side opposite to the pressure oil supply line, and a first three-way switching valve and an orifice are installed on this pressure oil supply line, and the first three-way switching valve receives the comparator output signal and In the region where the opening degree of the main steam control valve is larger than the set opening degree, the stop valve operates to open slowly, while in the region where the opening degree of the main steam control valve is smaller than the set opening degree, it opens to the drain side. The switched stop valve operates to close slowly,
Further, a relay trip valve is installed between the stop valve and the first three-way switching valve, and a second three-way switching valve is installed on the other pressure oil supply line communicating with the relay trip valve, so that when the stop valve is tripped or 1. A control device for a multi-stage mixed pressure steam turbine, characterized in that a relay trip valve is switched to the drain side at the time of cooling, and a stop valve is rapidly closed.