JP2011236806A - Steam power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam power generator having a function capable of suppressing a thrust in the opposing direction generated during the emergency stop without considerably reexamining a turbine structure.SOLUTION: The steam power generator includes a displacement type turbine 2 to be rotated with steam, a feed pipe 10 and an exhaust pipe 11 connected to the displacement type turbine 2, and an emergency shutoff valve 4 mounted on the feed pipe 10. The steam power generator has an exhaust steam return pipe 12 which is branched from the exhaust pipe 11 and connected to the feed pipe 10 between the emergency shutoff valve 4 and the displacement type turbine 2, a first check valve 5 mounted on the exhaust steam return pipe 12, and a solenoid valve 7 mounted on a steam release pipe 13 branched from the exhaust pipe 11. When the supply side pressure is dropped by the operation of the emergency shutoff valve 4, the first check valve 5 is opened, and steam is returned from the exhaust pipe 11 to the feed pipe 10 between the emergency shutoff valve 4 and the displacement type turbine 2.

Description

  The present invention relates to a steam prime mover that converts steam energy into mechanical energy (power). In particular, the present invention relates to a steam prime mover including a positive displacement turbine.

  Steam is widely used as a general heating source, but depending on the system, it may be discharged to the atmosphere or condensate circulation without using heat. Also, when steam is used in various production processes, the pressure difference energy at the time of decompression is not effectively used because the steam pressure is controlled by the decompression valve. In order to effectively use these unused steam energy, the applicant of the present application has developed a steam generator that recovers power with high efficiency using steam energy as mechanical energy (power). In order to recover steam energy as mechanical energy (power) with high efficiency, a positive displacement turbine is used instead of a speed turbine.

  Here, as a technique related to the steam generator that recovers steam energy as mechanical energy (power) and generates electric power, both are related to the steam generator including a speed turbine. There are techniques described.

  In Patent Document 1, a small steam turbine (steam prime mover) and a generator are prevented from reaching an overspeed when the generator is disconnected from the system load (electrically disconnected) during an emergency stop. Therefore, a technique is described in which the control valve 15 on the turbine exhaust side is closed to increase the exhaust side pressure.

  Further, in Patent Document 2, in order to prevent the radial turbine (steam prime mover) from becoming an overspeed at the time of stop, the supply side pressure is set by discharging the steam remaining in the supply pipe from the discharge valve 17. The technique of reducing is described.

JP 2008-101489 A JP-A-7-158406

  As described above, the techniques described in Patent Documents 1 and 2 all relate to a steam generator including a speed turbine that is currently widely used. On the other hand, it has been found that a steam generator (steam prime mover) having a positive displacement turbine has the following problems to be solved.

  In a steam prime mover including a positive displacement turbine, when an emergency shut-off valve provided on the upstream side of the turbine is closed during an emergency stop, the turbine continues to supply air for a certain period of time due to the inertial force of the rotor constituting the turbine. Thereby, the pressure in the supply pipe between the emergency shutoff valve and the turbine decreases. For this reason, the pressure before and after the turbine is higher in the supply side pressure than in the exhaust side during normal operation.However, during an emergency stop, both pressures are reversed and a thrust force in the opposite direction to that during normal operation occurs. Acts on the rotor. When the rotor receives a thrust force in the opposite direction, the rotor may move to the supply side, and the rotor and the casing may come into contact with each other. Although it may be possible to prevent the rotor from moving to the supply side by reviewing the bearing structure, etc., it is not preferable because it requires a significant review of the turbine structure, weight, and manufacturing costs. .

  The present invention has been made in view of the above circumstances, and the object thereof is to provide a function capable of suppressing the reverse thrust force generated at the time of emergency stop without making a major review of the turbine structure. Is to provide a steam prime mover.

  As a result of intensive studies to solve the above-described problems, the present inventors have established a check valve between the air supply pipe between the emergency shutoff valve and the positive displacement turbine and the exhaust pipe located on the downstream side of the turbine. By connecting with the exhaust return pipe and making the steam on the exhaust side return to the supply side when the supply side pressure drops due to the operation of the emergency shut-off valve, the turbine will be at an overspeed. The above-mentioned problems could be solved while preventing. Based on this finding, the present invention has been completed.

  That is, the present invention includes a positive displacement turbine that is rotationally driven by steam, an air supply pipe and an exhaust pipe connected to the positive displacement turbine, an emergency shutoff valve attached to the air supply pipe, the emergency shutoff valve, and the An exhaust return pipe branched from the exhaust pipe and connected to the intake pipe between the positive displacement turbine and an automatic valve attached to the exhaust return pipe, and an air supply side is provided by operating the emergency shut-off valve. A steam prime mover characterized in that when the pressure decreases, the automatic valve opens and steam is returned from the exhaust pipe to the air supply pipe between the emergency shutoff valve and the positive displacement turbine. .

  According to this configuration, when the supply side pressure decreases due to the operation of the emergency cutoff valve, the steam is returned to the supply pipe between the emergency cutoff valve and the positive displacement turbine, so that the supply side pressure and the exhaust pressure are reduced. The pressure difference from the side pressure is almost eliminated, and the generation of thrust force in the reverse direction can be suppressed.

  In the present invention, the automatic valve is a check valve, and further includes an automatic air release valve attached to an air discharge pipe branched from the exhaust pipe, and a control unit that controls opening and closing of the automatic air release valve. When the air supply side pressure decreases due to the operation of the emergency shutoff valve, before the check valve is opened, the automatic release valve is opened by the control unit, and steam is discharged from the discharge pipe. It is preferred that

  Here, when the exhaust side pressure is high, when the air supply side pressure decreases due to the operation of the emergency shutoff valve, the reverse direction is maintained even if the air supply side pressure is still higher than the exhaust side pressure. Thrust force may occur.

  According to this configuration, the automatic discharge valve is opened before the check valve is opened and the exhaust side pressure is reduced, so that it is possible to prevent generation of a reverse thrust force that may occur before the check valve is opened.

  Furthermore, in the present invention, the positive displacement turbine preferably has a screw rotor. According to the screw type, energy conversion efficiency can be further increased because the pressure difference becomes the rotational force as it is.

  According to a second aspect of the present invention, there is provided a positive displacement turbine driven by steam, a supply pipe and an exhaust pipe connected to the positive displacement turbine, and an emergency shutoff valve attached to the supply pipe. And an automatic air release valve attached to an air discharge pipe branched from the exhaust pipe, and a control unit that controls opening and closing of the automatic air release valve, and the supply side pressure is reduced by the operation of the emergency shut-off valve In the steam prime mover, the automatic release valve is opened by the control unit and the steam is discharged from the exhaust pipe so that the supply side pressure is equal to or greater than the exhaust side pressure. is there.

  According to this configuration, when the supply side pressure decreases due to the operation of the emergency shut-off valve, the vapor pressure in the exhaust pipe is controlled so that the supply side pressure is always equal to or greater than the exhaust side pressure. Thereby, generation | occurrence | production of the thrust force of a reverse direction can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the reverse direction thrust force produced at the time of an emergency stop can be suppressed in a steam prime mover provided with a positive displacement turbine, without carrying out the substantial review of a turbine structure.

It is a block diagram which shows the steam generator which comprises the steam prime mover which concerns on one Embodiment of this invention. It is a time chart which shows the behavior of the screw rotor rotation speed at the time of the emergency shut-off valve operation, the air supply side pressure, and the exhaust side pressure when the exhaust side pressure is relatively low. 6 is a time chart showing the behavior of the screw rotor rotation speed, the supply side pressure, and the exhaust side pressure when the emergency shutoff valve is operated when the exhaust side pressure is relatively high. 6 is a time chart showing the behavior of the screw rotor rotation speed, the supply side pressure, and the exhaust side pressure when the emergency shutoff valve is operated when the exhaust side pressure is relatively high.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following description, the steam prime mover according to the present invention is exemplified as the steam prime mover driving the generator, but the steam prime mover according to the present invention may be used as a prime mover driving a device other than the generator such as a compressor. Can be used.

(Configuration of steam generator with steam prime mover)
As shown in FIG. 1, the steam generator 1 includes a positive displacement turbine 2 and a generator G connected to the positive displacement turbine 2 as main devices. The positive displacement turbine 2 and the generator G are housed in the unit cover 14 together with other attached devices (the control panel 3 and the like will be described in detail later). A steam prime mover having a positive displacement turbine 2 as a main device is constituted by a device group excluding the generator G among a plurality of devices constituting the steam generator 1.

  The positive displacement turbine 2 includes a pair of screw rotors 8 and a screw casing 9 that accommodates the screw rotor 8. An air supply pipe 10 and an exhaust pipe 11 are connected to the screw casing 9. When steam flows from the air supply pipe 10 into the screw casing 9, the steam passes through the screw rotor 8 while expanding and exits from the exhaust pipe 11.

  Note that a positive displacement turbine having a single screw rotor (single rotor) may be used instead of the pair of screw rotors 8 (double rotor). According to the screw type as in the present embodiment, the pressure difference before and after the screw rotor becomes the rotational force of the screw rotor 8 as it is, so that the energy conversion efficiency can be further increased. Examples of positive displacement turbines other than the screw type include rotary type, scroll type, and root type type turbines.

  An emergency shutoff valve 4 is attached to the air supply pipe 10. The emergency shut-off valve 4 is often an electromagnetic valve, but may be an air operated valve or the like. A pressure gauge P <b> 1 is attached to the air supply pipe 10 between the emergency shutoff valve 4 and the positive displacement turbine 2. The pressure gauge P <b> 1 is an instrument for measuring the supply air pressure of the positive displacement turbine 2.

  A pressure gauge P <b> 2 is attached to the exhaust pipe 11 near the outlet of the positive displacement turbine 2. The pressure gauge P2 is an instrument for measuring the exhaust pressure of the positive displacement turbine 2.

  Here, an air supply pipe 10 between the pressure gauge P1 and the positive displacement turbine 2 and an exhaust pipe 11 between the positive displacement turbine 2 and the pressure gauge P2 are connected by an exhaust return pipe 12. A first check valve 5 is attached to the exhaust return pipe 12. The first check valve 5 is attached in a direction to return steam from the exhaust pipe 11 to the air supply pipe 10 (no steam flows from the air supply pipe 10 to the exhaust pipe 11). When the air supply side pressure of the positive displacement turbine 2 <the exhaust side pressure of the positive displacement turbine 2, the first check valve 5 automatically opens due to the pressure difference, and the exhaust side steam flows to the supply side. The first check valve 5 corresponds to an automatic valve attached to the exhaust return pipe according to the present invention.

  In the exhaust return pipe 12, the branch point from the exhaust pipe 11 may be downstream of the pressure gauge P2. Further, in the exhaust return pipe 12, the connection point to the air supply pipe 10 may be upstream of the pressure gauge P1 (between the emergency shutoff valve 4 and the pressure gauge P1).

  A second check valve 6 is attached to the downstream portion of the exhaust pipe 11. In the present embodiment, the downstream end of the exhaust pipe 11 is connected to the process equipment 50. Here, the process device 50 is a device for heating and sterilizing, for example, using steam. There are various process equipment 50, that is, the vapor pressure used in the process equipment 50 is 0.2 MPa to 0.9 MPa, for example, and the vapor pressure used varies depending on the process equipment 50. The second check valve 6 is a valve for preventing the backflow of steam from the process equipment 50.

  Further, an exhaust pipe 13 branched from the exhaust pipe 11 between the positive displacement turbine 2 and the second check valve 6 is provided in the exhaust pipe 11, and the electromagnetic valve 7 is attached to the exhaust pipe 13. The electromagnetic valve 7 corresponds to an automatic air release valve according to the present invention. An air operation valve or the like may be used as the automatic air release valve.

  Next, as indicated by a dotted line in FIG. 1, signals from the pressure gauge P <b> 1 and the pressure gauge P <b> 2 are input to the control panel 3 of the steam generator 1. The emergency shutoff valve 4 and the electromagnetic valve 7 are inputted with an open / close signal from the control panel 3. The control panel 3 corresponds to a control unit according to the present invention.

(Control during emergency stop)
For example, when an accident occurs in the factory where the steam generator 1 is installed, the generator G is disconnected from the system load (the private power system that supplies power to the equipment in the factory) by a signal from the control panel 3. In addition, the emergency shutoff valve 4 is closed and the supply of steam to the positive displacement turbine 2 is stopped immediately. The reason for closing the emergency shut-off valve 4 is to prevent the screw rotor 8 from reaching an excessive rotation speed due to the absence of the load.

  Hereinafter, the control of the steam generator 1 at the time of emergency stop will be described separately for a case where the exhaust side pressure during normal operation is about 0.2 MPa and a case where the exhaust side pressure during normal operation is about 0.5 MPa. To do. Note that the supply side pressure during normal operation (the pressure of the steam supplied to the positive displacement turbine 2) is, for example, about 0.8 MPa to 2 MPa.

(When the exhaust side pressure is relatively low at about 0.2 MPa)
FIG. 2 is a time chart showing the behavior of the screw rotor rotation speed, the supply side pressure, and the exhaust side pressure when the emergency shutoff valve is operated when the exhaust side pressure is relatively low at about 0.2 MPa. FIG. 2A is a time chart in the prior art in which the exhaust return pipe 12, the first check valve 5 and the electromagnetic valve 7 are not provided, and FIG. 2B is the steam generator 1 of the present embodiment. It is a time chart in. In both time charts shown in FIGS. 2A and 2B, the emergency shutoff valve is closed at time T1. 2 is the steam pressure (detected by the pressure gauge P1) in the air supply pipe between the emergency shutoff valve and the positive displacement turbine, and the exhaust pressure is the positive displacement turbine. And the second check valve 6 in the exhaust pipe (detected by the pressure gauge P2).

  First, the problems in the prior art will be described with reference to FIG. In a steam prime mover including a positive displacement turbine, when an emergency shut-off valve provided on the upstream side of the turbine is closed during an emergency stop, the turbine continues to supply air for a certain period of time due to the inertial force of the rotor constituting the turbine. Thereby, as shown to Fig.2 (a), the air supply pipe pressure between the emergency shutoff valve and a turbine falls rapidly. For this reason, the pressure before and after the turbine is higher in the supply side pressure than in the exhaust side during normal operation.However, during an emergency stop, both pressures are reversed and a thrust force in the opposite direction to that during normal operation occurs. There is a time zone that acts on the rotor. When the rotor receives a thrust force in the opposite direction, the rotor may move to the supply side, and the rotor and the casing may come into contact with each other.

  However, as shown in FIG. 2 (b), in the case of the steam generator 1 of the present embodiment, when the supply side pressure decreases due to the operation of the emergency shutoff valve 4, the supply side pressure < When the exhaust side pressure is reached, the first check valve 5 opens and the steam returns from the exhaust pipe 11 to the air supply pipe 10 between the emergency shutoff valve 4 and the positive displacement turbine 2. Thereby, there is almost no pressure difference between the air supply side pressure and the exhaust side pressure, and as a result, generation of a thrust force in the opposite direction can be suppressed. That is, contact between the screw rotor 8 and the screw casing 9 can be prevented. Further, by making the air supply pipe 10 and the exhaust pipe 11 between the emergency shutoff valve 4 and the positive displacement turbine 2 communicate with each other via the first check valve 5, it is possible to suppress the generation of reverse thrust force. According to the present invention, no significant review of the turbine structure such as the bearing portion is required.

  As described above, when the air supply side pressure decreases due to the operation of the emergency shutoff valve 4, the first check valve 5 opens due to the differential pressure when the air supply side pressure <the exhaust side pressure. Therefore, there is no control of opening the first check valve 5 with a signal from the outside. On the other hand, an electromagnetic valve may be provided in the exhaust return pipe 12 instead of the first check valve 5 (check valve). In this case, for example, the solenoid valve is opened by a signal from the control panel 3 at a timing when the supply side pressure and the exhaust side pressure become equal. Thereby, generation | occurrence | production of the thrust force of a reverse direction can be suppressed. The supply side pressure is monitored by the pressure gauge P1, and the exhaust side pressure is monitored by the pressure gauge P2. Note that it is preferable to use a check valve as an automatic valve rather than a solenoid valve from the viewpoint of reliability (small failure) and the need to control fewer valves.

(When the exhaust side pressure is relatively high, about 0.5 MPa)
FIG. 3 is a time chart showing the behavior of the screw rotor rotation speed, the supply side pressure, and the exhaust side pressure when the emergency shutoff valve is operated when the exhaust side pressure is relatively high at about 0.5 MPa. FIG. 3A is a time chart in the prior art in which the exhaust return pipe 12, the first check valve 5, the electromagnetic valve 7 and the like are not provided, and FIG. 3B is the steam generator 1 of the present embodiment. It is a time chart in. In both time charts shown in FIGS. 3A and 3B, the emergency shutoff valve is closed at time T1. Note that the difference in conditions between FIG. 2 and FIG. 3 is only the value of the exhaust side pressure.

  First, the problems in the prior art will be described with reference to FIG. In a steam prime mover equipped with a positive displacement turbine, when the exhaust side pressure is high, the supply side pressure is still higher than the exhaust side pressure when the supply side pressure decreases due to the operation of the emergency shutoff valve. However, a reverse thrust force may occur. Specifically, a reverse thrust force may be generated at point A shown in FIG. 3A (the supply-side pressure is slightly higher than the exhaust-side pressure).

  Therefore, in the steam generator 1 of this embodiment, the electromagnetic valve 7 is opened by the signal from the control panel 3 after the emergency shut-off valve 4 is closed and before the first check valve 5 is opened. . And if the exhaust side pressure falls to about 0.2 MPa, for example, the solenoid valve 7 is closed. The change in the exhaust side pressure at that time is as shown in FIG. By opening the electromagnetic valve 7, the vapor | steam of the exhaust pipe 11 is discharged | emitted from the exhaust pipe 13, and an exhaust side pressure falls. Thereafter, when the first check valve 5 is opened when the supply side pressure <the exhaust side pressure, the pressure difference between the supply side pressure and the exhaust side pressure hardly occurs, and the reverse thrust force is Does not occur.

  According to this embodiment, the reverse thrust force that can be generated before the first check valve 5 is opened by opening the electromagnetic valve 7 and lowering the exhaust side pressure before the first check valve 5 is opened. Occurrence can be prevented.

  If the solenoid valve 7 is opened at the same time as closing the emergency shut-off valve 4, the differential pressure across the positive displacement turbine 2 may increase momentarily, and the rotational speed of the screw rotor 8 may become an overspeed. The reason why the electromagnetic valve 7 is opened after the emergency shut-off valve 4 is closed and before the first check valve 5 is opened is to prevent the rotational speed of the screw rotor 8 from becoming an excessive rotational speed. But there is. The reason why the solenoid valve 7 is closed when the exhaust side pressure is reduced to, for example, about 0.2 MPa is to prevent the rotational speed of the screw rotor 8 from becoming an excessive rotational speed. That is, according to the present embodiment, the turbine can be stopped during an emergency stop without increasing the turbine rotational speed more than necessary and while preventing the generation of the reverse thrust force.

  As described above, the supply side pressure is monitored by the pressure gauge P1, and the exhaust side pressure is monitored by the pressure gauge P2. Opening the electromagnetic valve 7 before the first check valve 5 is opened means that the electromagnetic valve 7 is opened before the detected value by the pressure gauge P1 is equal to the detected value by the pressure gauge P2. . That is, whether or not it is time to open the solenoid valve 7 is determined by the difference between the detected value by the pressure gauge P1 and the detected value by the pressure gauge P2. Therefore, when the difference between the detected value by the pressure gauge P1 and the detected value by the pressure gauge P2 falls to a predetermined threshold value, the electromagnetic valve 7 is opened.

(First modification)
In the steam generator 1 (steam prime mover) shown in FIG. 1, the first check valve 5 and the exhaust return pipe 12 may be omitted. In this case, when the supply side pressure decreases due to the operation of the emergency shutoff valve 4, the solenoid valve 7 is opened by a signal from the control panel 3 so that the supply side pressure ≥ the exhaust side pressure is always satisfied. Opening control is performed. Specifically, for example, when the difference between the detected value by the pressure gauge P1 and the detected value by the pressure gauge P2 decreases to a predetermined threshold value, the solenoid valve 7 is opened, and the threshold value (difference is maintained until the exhaust side pressure becomes zero. The opening degree of the electromagnetic valve 7 is controlled so that the pressure value is maintained constant. The behavior such as the exhaust side pressure at this time is shown in FIG.

  Note that it is not always necessary to control the opening degree of the electromagnetic valve 7 so that the threshold value (differential pressure value) is kept constant. After the electromagnetic valve 7 is opened to the predetermined threshold value, at least air supply By maintaining the state of side pressure ≧ exhaust side pressure, it is possible to suppress the generation of thrust force in the reverse direction. As described above, by maintaining the threshold value (differential pressure value) almost constant, generation of reverse thrust force can be suppressed, and the rotational speed of the screw rotor 8 can be further prevented from becoming an excessive rotational speed. can do.

  The steam prime mover shown in FIG. 1 and the steam prime mover (first modified example) in which the first check valve 5 and the exhaust return pipe 12 are omitted so as to maintain the state of the supply side pressure ≧ the exhaust side pressure. It is common in that it is configured.

(Second modification)
Moreover, in the steam generator 1 (steam prime mover) shown in FIG. 1, the vent pipe 13 and the electromagnetic valve 7 (automatic vent valve) may be omitted. When the exhaust steam usage conditions are limited only to relatively low conditions (when the exhaust side pressure during normal operation is limited to only relatively low conditions such as about 0.2 MPa), the structure of the positive displacement turbine (suction volume, Depending on the discharge volume or the like, the air release pipe 13 and the electromagnetic valve 7 (automatic air release valve) may be omitted.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

  For example, the connection destination of the exhaust pipe 11 is not limited to various process devices 50, and the exhaust pipe 11 may be connected to a chimney or the like.

1: Steam generator 2: Positive displacement turbine (screw type)
3: Control panel (control unit)
4: Emergency shut-off valve 5: First check valve (automatic valve)
7: Solenoid valve (automatic air release valve)
8: Screw rotor 9: Screw casing 10: Supply pipe 11: Exhaust pipe 12: Exhaust return pipe 13: Exhaust pipe G: Generator

Claims (4)

A positive displacement turbine that is rotationally driven by steam;
An intake pipe and an exhaust pipe connected to the positive displacement turbine;
An emergency shut-off valve attached to the air supply pipe;
An exhaust return pipe branched from the exhaust pipe and connected to the air supply pipe between the emergency shutoff valve and the positive displacement turbine;
An automatic valve attached to the exhaust return pipe;
With
When the supply side pressure decreases due to the operation of the emergency shut-off valve, the automatic valve opens and steam is returned from the exhaust pipe to the supply pipe between the emergency shut-off valve and the positive displacement turbine. Steam prime mover, characterized by The steam generator according to claim 1,
The automatic valve is a check valve;
An automatic air release valve attached to an air discharge pipe branched from the exhaust pipe;
A control unit for controlling opening and closing of the automatic air release valve;
Further comprising
When the air supply side pressure decreases due to the operation of the emergency shut-off valve, the automatic release valve is opened by the control unit before the check valve is opened, and steam is discharged from the discharge pipe. A steam prime mover characterized by A positive displacement turbine that is rotationally driven by steam;
An intake pipe and an exhaust pipe connected to the positive displacement turbine;
An emergency shut-off valve attached to the air supply pipe;
An automatic air release valve attached to an air discharge pipe branched from the exhaust pipe;
A control unit for controlling opening and closing of the automatic air release valve;
With
When the air supply side pressure decreases due to the operation of the emergency shut-off valve, the control unit opens the automatic air release valve so that the air supply side pressure is equal to or greater than the exhaust side pressure. Steam prime mover characterized in that steam is discharged. The steam motor according to any one of claims 1 to 3,
The positive displacement turbine has a screw rotor, and is a steam prime mover.

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