JP5568517B2 - Steam-driven compressor - Google Patents

Description

  The present invention relates to a steam-driven compression device.

  In a plant that uses steam generated in a boiler, the medium pressure (for example, 1.2 to 1.6 MPa) steam generated by the boiler is decompressed by a pressure reducing valve, and the low pressure (for example, 0.8 to 0.9 MPa) steam is used. Is generally supplied to demand equipment. When the pressure of the steam is reduced by the pressure reducing valve, the pressure difference energy of the steam is discarded, and it is desired to recover the energy.

  In Patent Document 1, by driving a screw steam expander (“steam motor” or “steam end”) with steam, the pressure energy of the steam is converted into rotational force and recovered, and the rotation of the steam expander is further recovered. A steam-driven compressor that drives a screw compressor by force to compress air is described.

  In a screw compressor driven by an electric motor, when the pressure (load) of a reservoir (or piping) that stores compressed air discharged by the screw compressor reaches a set value, a suction adjustment valve provided in the suction flow path of the screw compressor A load / unload mechanism that closes the valve and opens the suction regulating valve again when the pressure in the reservoir falls below a set value is widely adopted. Since the compression work (torque) necessary to compress the gas is proportional to the gas pressure, the screw compressor is reduced by closing the suction adjustment valve by the load / unload mechanism and lowering the suction pressure of the screw compressor. It is known that the load (braking torque generated by the screw compressor) can be reduced to about 20% of the total load.

  When the screw compressor is driven by the steam expander, the rotation speed of the steam expander and the screw compressor is a rotation speed that balances the driving torque generated in the steam expander and the braking torque of the screw compressor. Therefore, when the braking torque of the screw compressor decreases, the rotation speed of the steam expander increases. That is, when the load / unload mechanism is employed in the steam-driven compressor, there is a problem that the steam expander rapidly accelerates during unloading.

  In the steam-driven compression device of Patent Document 1, a control valve is provided in a flow path for supplying steam to the steam expander, and this control valve is PID controlled so as to keep the pressure in the discharge flow path of the screw compressor constant. Thus, the rotation speed of the steam expander is controlled. In such a configuration, the rotational speed of the screw compressor becomes very low when the load is small. Then, the compressed air on the discharge side leaks back to the suction side from the gap of the screw rotor. As the compressed air leaks back, heat generated by the compression is transferred to the suction side, causing a problem that the temperature of the compressed air to be discharged gradually rises.

JP 2009-250196 A

  In view of the above problems, an object of the present invention is to provide a steam-driven compression device in which the rotation speed of the steam expander does not change suddenly.

  In order to solve the above problems, a steam-driven compression device according to the present invention includes a steam expander that converts an expansion force of steam into a rotational force, a compressor that is driven by the steam expander and compresses a target gas, The target gas compressed from the compressor is discharged, a discharge flow path having a check valve, a branch from the discharge flow path on the upstream side of the check valve, and opened to the outside through a discharge valve A discharge pressure detector for detecting the pressure of the discharge flow path on the upstream side of the check valve, and a control pressure for detecting the pressure of the discharge flow path on the downstream side of the check valve A detector, a rotational speed detector for detecting the rotational speed of the steam expander, a steam control valve capable of controlling the flow rate of the steam of the steam expander, and a detection value of the control pressure detector set to a predetermined value Adjust the opening of the steam control valve to achieve pressure When the detection value of the main controller and the rotation speed detector is equal to or lower than a predetermined lower limit rotation speed, the air discharge valve opens the air discharge valve so that the detection value of the discharge pressure detector becomes the set pressure. And a control device.

  According to this configuration, the opening degree of the steam control valve is adjusted according to the detection value of the control pressure detector that varies according to the balance between the demand load and the supply amount of compressed air. Thereby, the supply amount of compressed air is balanced with the demand amount by controlling the driving torque of the steam expander and adjusting the rotation speed of the steam compressor. In addition, when the rotation speed of the steam compressor drops to the lower limit value, the rotation speed of the steam compressor is made lower than the lower limit rotation speed by opening the vent valve and forcibly reducing the supply amount of compressed air. Avoid getting smaller. Thereby, in the compressor, it is possible to prevent the target gas from leaking from the discharge side (high pressure side) to the suction side (low pressure side), thereby increasing the suction temperature of the target gas and thus the discharge temperature.

  Moreover, the steam drive type compressor of this invention WHEREIN: The said air discharge control apparatus may be able to adjust the opening degree of the said air discharge valve continuously.

  According to this configuration, since the air discharge amount can be continuously adjusted, the supply amount of the compressed air can be smoothly changed, a sudden load fluctuation can be suppressed, and a stable operation can be performed.

  In the steam-driven compressor according to the present invention, the discharge channel includes a plurality of branch channels each including the discharge valve, and the discharge controller controls the detection value of the discharge pressure detector. Accordingly, the number of the vent valves to be opened may be adjusted.

  According to this configuration, since the air discharge amount is adjusted by controlling the number of air discharge valves, it is possible to reduce the torque fluctuation of the compressor and perform smooth operation.

  In the steam driven compressor of the present invention, a silencer may be provided on the downstream side of the vent valve.

  According to this configuration, noise due to wind discharge is reduced.

It is a lineblock diagram of the steam drive type compression device of a 1st embodiment of the present invention. It is a block diagram of the vapor | steam drive-type compression apparatus of 2nd Embodiment of this invention. It is a block diagram of the vapor | steam drive-type compression apparatus of 3rd Embodiment of this invention. It is a block diagram of the vapor | steam drive-type compression apparatus of 4th Embodiment of this invention.

  Embodiments of the present invention will now be described with reference to the drawings. First, FIG. 1 shows a steam-driven compression device 1 according to a first embodiment of the present invention. The steam-driven compression device 1 is a compressed air production device that uses air as a target gas to be compressed.

  The steam-driven compressor 1 includes a steam expander 2 that converts steam expansion force into rotational force, a first stage compressor 4 and a second compressor that are driven by the steam expander 2 via a gear 3 and compress air. A stage compressor 5. The steam expander 2 is a screw expander that houses a pair of male and female screw rotors in a housing and rotates the screw rotor by expanding steam in a sealed space in the tooth groove of the screw rotor. The first-stage compressor 4 and the second-stage compressor 5 house a pair of male and female screw rotors in a housing. By rotating the screw rotor, air is supplied in a sealed space in the tooth groove of the screw rotor. It is a screw compressor that compresses.

  In the steam driven compressor 1, the first stage compressor 4 and the second stage compressor 5 are connected in series via an intercooler 6. That is, the air compressed and discharged by the first stage compressor 4 is cooled by the intercooler 6 and then further compressed by the second stage compressor 5. The compressed air discharged from the second stage compressor 5 is sent to a reservoir (not shown) through a discharge passage 9 in which an aftercooler 7 and a check valve 8 are interposed, and is supplied from the reservoir to a demand destination. Another air compression device may be connected in parallel to the reservoir.

  Further, the steam-driven compressor 1 has an air discharge passage 12 that branches from the discharge passage 9 between the aftercooler 7 and the check valve 8 and is connected to the silencer 11 through the air discharge valve 10. That is, the end of the discharge channel 12 provided with the silencer 11 is open to the atmosphere.

  Further, the discharge flow path 9 has an upstream side of the check valve 8, more specifically, a discharge pressure detector 13 that detects the pressure Pd of compressed air between the aftercooler 7 and the air discharge flow path 12, and a check. A control pressure detector 14 for detecting the pressure Pc of the compressed air on the downstream side of the valve 8.

  Further, the steam-driven compressor 1 is provided with a steam control valve 15 that can control the flow rate of the steam by adjusting the opening degree in the flow path for supplying the steam to the steam expander 2. A rotation speed detector 16 for detecting the rotation speed RI is provided.

  The steam-driven compressor 1 receives the detection value Pc of the control pressure detector 14 so that the detection value of the control pressure detector 14 becomes a predetermined set pressure Pset (for example, 0.7 MPa). Based on the detected value Pd of the discharge pressure detector 13 and the detected value RI of the rotation speed detector 16, the opening of the discharge valve 10 is adjusted based on the main control device 17 that adjusts the opening of the steam control valve 15. And an air discharge control device 18 for adjusting. The main control device 17 and the air discharge control device 18 may be realized by the same control device such as a computer.

  When the rotational speed RI of the steam expander 2 exceeds a predetermined lower limit value RL (for example, 40% of the rated rotational speed), the ventilating control device 18 keeps the ventilating valve 10 in a fully closed state, and the rotational speed. Only when RI is equal to or lower than the lower limit value RL, the air discharge valve 10 is programmed to be opened. Then, the air discharge control device 18 opens the air discharge valve 10 by, for example, PID control so that the detection value Pd of the discharge pressure detector 13 becomes the set pressure Pset based on the detection value Pd of the discharge pressure detector 13. Adjust the degree.

  The lower limit value RL of the rotational speed RI is such that the discharge side air once compressed in the first stage compressor 4 or the second stage compressor 5 leaks back to the suction side from the gap of the screw rotor, and the temperature of the compressed air rises. Therefore, the number of rotations is set to the number of rotations with a margin for safety added to the number of rotations where the occurrence of a malfunction is a concern.

  In the steam-driven compressor 1, when the demand for compressed air is large, the pressure of the reservoir, that is, the detection value Pc of the control pressure detector 14 decreases. Then, the main controller 17 increases the opening of the steam control valve 15 and increases the amount of steam supplied to the steam expander 2. Thereby, the drive torque of the steam expander 2 increases, the rotation speed of the 1st stage compressor 4 and the 2nd stage compressor 5 is raised, and the discharge amount of compressed air is increased.

  On the contrary, when the demand for compressed air is small, the compressed air is excessively supplied from the steam-driven compressor 1 to the reservoir, so that the detection value Pc of the control pressure detector 14 increases. Then, the main controller 17 reduces the opening of the steam control valve 15 and decreases the amount of steam supplied to the steam expander 2. As a result, the driving torque of the steam expander 2 is lowered, the rotational speeds of the first stage compressor 4 and the second stage compressor 5 are lowered, and the discharge amount of the compressed air is reduced.

  When the demand for compressed air further decreases and the rotational speed RI of the steam expander 2 decreases to the lower limit value RL, the air discharge control device 18 starts adjusting the opening degree of the air discharge valve 10. When the main controller 17 attempts to further reduce the opening of the steam control valve 15, that is, when the detected value Pc of the control pressure detector 14 is greater than the set pressure Pset, the compression from the steam-driven compressor 1 Since the supply of air is prevailing, the detection value Pd of the discharge pressure detector 13 is substantially equal to the detection value Pc. Therefore, the air discharge control device 18 opens the air discharge valve 10 to release compressed air from the upstream side of the check valve 8 of the discharge flow path 9, and decreases the detection value Pc of the control pressure detector 14.

  That is, the air discharge control device 18 makes the pressure Pd on the upstream side of the check valve 8 in the discharge passage 9 lower than the pressure Pc on the downstream side of the check valve 8 by adjusting the opening degree of the air discharge valve 10. Then, the supply of compressed air from the steam-driven compressor 1 to the reservoir is stopped. The detection value Pc of the control pressure detector 14 on the downstream side of the check valve 8 is subsequently lowered by the consumption of the compressed air in the reservoir by the demand facility.

  When the compressed air in the reservoir is further consumed and the detected value Pc of the control pressure detector 14 becomes smaller than the set pressure Pset, the main controller 17 increases the opening of the steam control valve 15 and the steam expander 2 Increase the number of revolutions. Thereby, since the rotation speed RI of the steam expander 2 becomes larger than the lower limit value RL, the air discharge control device 18 closes the air discharge valve 10.

  As described above, in the steam driven compressor 1, when the rotational speed RI of the steam expander 2 is reduced to the lower limit value RL, the air discharge control device 18 releases the compressed air from the air discharge channel 12 to the atmosphere. The detection value Pc of the control pressure detector 14 is lowered to prevent further reduction in the rotational speed RI of the steam expander 2. Accordingly, in the first stage compressor 4 and the second stage compressor 5, the compressed air is prevented from leaking back from the discharge side to the suction side, so that the first stage compressor 4 and the second stage compressor due to overheating of the compressed air are prevented. There is no trouble such as damage to the stage compressor 5.

  In FIG. 2, the vapor | steam drive type compression apparatus 1 which is 2nd Embodiment of this invention is shown. In the following embodiments, the same constituent elements as those in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the steam-driven compression device 1 of the present embodiment, each of the discharge channels 12 includes a discharge valve 10a that can be selected to be either fully closed or fully open, and has a plurality of branches provided with silencers 11 at the ends that are open to the atmosphere. A flow path 19 is provided. The air discharge control device 18 opens the air release valve 10a so that the detection value Pd of the discharge pressure detector 13 becomes the set pressure Pset when the detection value RI of the rotation speed detector 16 is equal to or lower than the lower limit value RL. Control the number of. That is, when the detection value Pd of the discharge pressure detector 13 is increasing, the air discharge control device 18 increases the number of open air discharge valves 10a and the detection value Pd of the discharge pressure detector 13 is increased. When the airflow has decreased, the air discharge control device 18 decreases the number of open air discharge valves 10a.

  Even with such a configuration of the air discharge flow path 12, an appropriate amount of compressed air can be discharged to the atmosphere, and further reduction in the rotational speed RI of the steam expander 2 can be prevented.

  FIG. 3 shows a steam driven compression apparatus 1 according to a third embodiment of the present invention. The steam-driven compressor 1 of the present embodiment is a single-stage compressor that has the first stage compressor 4 but does not have the second stage compressor. As the present embodiment shows, the present invention can be applied regardless of the number of stages of the compressor.

  In the drive type compressor 1 of this embodiment, the steam control valve 15 is provided on the exhaust side of the steam expander 3. Thus, the steam control valve 15 may be arranged in any way as long as it can adjust the driving torque generated by the steam expander 2.

  In FIG. 4, the vapor | steam drive type compression apparatus 1 which is 4th Embodiment of this invention is shown. In the steam-driven compression device 1 according to the present embodiment, the discharge channel 12 is branched from the discharge channel 9 upstream of the aftercooler 7. In the present embodiment, since the compressed air released from the atmosphere through the discharge channel 12 does not pass through the aftercooler 7, the load on the aftercooler 7 is small. Further, as shown in the present embodiment, the discharge channel 12 in the present invention may be branched from anywhere in the discharge channel 9 as long as it is upstream of the check valve 8.

DESCRIPTION OF SYMBOLS 1 ... Steam drive type compressor 2 ... Steam expander 4 ... 1st stage compressor 5 ... 2nd stage compressor 8 ... Check valve 9 ... Discharge flow path 10, 10a ... Air discharge valve 11 ... Silencer 12 ... Air discharge flow Path 13 ... Discharge pressure detector 14 ... Control pressure detector 15 ... Steam control valve 16 ... Rotational speed detector 17 ... Main controller 18 ... Air discharge controller 19 ... Branch flow path

Claims (4)

A steam expander that converts the expansion force of steam into rotational force;
A compressor driven by the steam expander to compress the target gas;
The target gas compressed from the compressor is discharged, and a discharge flow path including a check valve;
An air discharge passage that branches off from the discharge passage on the upstream side of the check valve and is opened to the outside through the air discharge valve;
A discharge pressure detector for detecting the pressure of the discharge flow path upstream of the check valve;
A control pressure detector for detecting the pressure of the discharge flow path downstream of the check valve;
A rotational speed detector for detecting the rotational speed of the steam expander;
A steam control valve capable of controlling the flow rate of the steam of the steam expander;
A main controller that adjusts the opening of the steam control valve so that the detection value of the control pressure detector becomes a predetermined set pressure;
An air discharge control device that opens the air discharge valve so that the detection value of the discharge pressure detector becomes the set pressure when the detection value of the rotation speed detector is equal to or lower than a predetermined lower limit rotation speed; A steam-driven compression device.   The steam-driven compression device according to claim 1, wherein the air discharge control device is capable of continuously adjusting an opening degree of the air discharge valve. The discharge channel includes a plurality of branch channels each including the discharge valve,
The steam-driven compression device according to claim 1, wherein the air discharge control device adjusts the number of the air discharge valves to be opened according to a detection value of the discharge pressure detector.   The steam-driven compressor according to any one of claims 1 to 3, further comprising a silencer on a downstream side of the discharge valve.

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