JP2009257119A - Steam expander driven air compression apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steam expander driven air compression apparatus capable of stably recovering pressure difference energy irrespective of the amount of steam used. <P>SOLUTION: The steam expander driven air compression apparatus 1 includes a displacement type steam expander 2, a displacement type air compressor 3 driven by the displacement type steam expander 2, a capacity regulation valve 6 which can regulate the air intake amount of the displacement type steam expander 2, and a control device 12 for controlling the opening degree of the capacity regulation valve 6 so that the pressure on the discharge side of the displacement type air compressor 3 may be constant. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steam expander driven air compressor.

  In a plant that uses steam generated in a boiler, high pressure (for example, 1.2 to 1.6 MPa) steam generated by the boiler is reduced by a pressure reducing valve, and low pressure (for example, 0.8 to 0.9 MPa) steam is demanded. It is common to supply 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 this energy.

  As in Patent Document 1, an apparatus that recovers steam pressure difference energy as electric energy by driving a generator with a screw-type steam expander has been proposed. Generally, the generator needs to be operated at a constant speed, but if the speed of the screw-type steam expander is kept constant, the steam pressure on the low pressure side will fluctuate.

  As described in Patent Document 1, the speed control of the screw-type steam expander generally controls the opening degree of the flow rate adjusting valve provided on the suction side so that the discharge pressure becomes constant. . Therefore, it is possible to cope with a change in the amount of steam used by controlling the discharge pressure of the screw-type steam expander to be constant by using a generator that can respond to the speed change.

  However, since the amount of steam used is unstable in a small-scale plant, if the pressure on the discharge side of the screw-type steam expander is kept constant, the fluctuation of the rotational speed of the screw-type steam expander becomes very large. . For this reason, when the amount of steam used decreases, the output torque of the screw steam expander may be insufficient and the generator may not be driven.

  Patent Document 2 describes an apparatus that compresses air by driving a screw-type air compressor with a screw-type steam expander. However, if the amount of steam used and the amount of compressed air consumed are not proportional, keeping the pressure on the discharge side of the screw-type steam expander constant prevents the amount of compressed air generated from being controlled. There is a problem that the pressure of the compressed air fluctuates due to excess or deficiency.

However,
JP 2007-16614 A Japanese Patent Laid-Open No. 63-50692

  In view of the above problems, an object of the present invention is to provide a steam expander-driven air compressor that can stably recover pressure difference energy regardless of the amount of steam used.

  In order to solve the above problems, a steam expander-driven air compressor according to the present invention includes a positive displacement steam expander, a positive displacement air compressor driven by the positive displacement steam expander, and the positive displacement steam expansion valve. And a control device for controlling the opening degree of the capacity adjusting valve so that the pressure on the discharge side of the positive displacement air compressor is constant.

  According to this configuration, since the amount of steam corresponding to the drive torque required for the positive displacement air compressor is supplied to the positive displacement steam expander by the capacity adjustment valve, the positive displacement air compressor can be driven stably.

  The steam expander-driven air compressor of the present invention has a pressure detector that detects the pressure on the discharge side of the positive displacement air compressor, and the control device is based on a detection signal of the pressure detector. The PID control may be performed on the opening of the capacity adjustment valve.

  According to this configuration, a widely distributed PID controller can be used, the configuration is simple, and the cost is low.

  In the steam expander-driven air compressor of the present invention, the positive displacement steam expander may drive the positive displacement air compressor via a speed reducer.

  According to this structure, mechanical efficiency becomes high by selecting the reduction ratio of a reduction gear according to the load torque of a positive displacement air compressor.

  In the steam expander-driven air compressor according to the present invention, the positive displacement steam expander may be a screw expander, and the positive displacement air compressor may be a screw compressor.

  According to this configuration, since the torque fluctuation of the screw expander and the screw compressor is small, the operable pressure range is wide and stable operation can be performed.

  In the steam expander-driven air compressor of the present invention, the upstream side of the capacity adjustment valve and the discharge side of the positive displacement steam expander may be connected via a pressure reducing valve.

  According to this configuration, when the amount of steam used is large, it is possible to supply necessary steam to the demand facility by bypassing the steam expander-driven air compression device via the pressure reducing valve.

  According to the present invention, the capacity provided on the suction side of the positive displacement steam expander so as to drive the positive displacement air compressor with the positive displacement steam expander and keep the pressure on the discharge side of the positive displacement air compressor constant. Since the opening degree of the regulating valve is adjusted, the differential pressure energy between the supply pressure of steam and the operating pressure can be stably recovered as pneumatic energy.

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1: shows the outline | summary of the steam expander drive air compression apparatus 1 of one Embodiment of this invention. The steam expander-driven air compressor 1 has a screw expander (expander) 2 that is a positive displacement steam expander and a screw compressor 3 that is a positive displacement air compressor, and an output shaft of the screw expander 2. And an input shaft of the screw compressor 3 are connected via a speed reducer 4.

  The screw expander 2 is supplied with high-pressure steam from a boiler (not shown) via a steam trap 5 and a capacity adjustment valve 6. The screw expander 2 converts the expansion force of the inhaled steam into a rotational force, and supplies low-pressure steam decompressed by expansion to a demand facility (not shown). The steam expander-driven air compressor 1 can supply high-pressure steam to the low pressure side via the pressure reducing valve 7 and not via the screw expander 2.

  The screw compressor 3 sucks air through the air filter 8, compresses it, and discharges it. The compressed air discharged from the screw compressor 3 is separated from the lubricating oil by the oil separator 9, cooled by the aftercooler 10, and supplied to the demand facility.

  The steam expander-driven air compressor 1 is provided with a pressure detector 11 at the outlet pipe of the oil separator 9 so that the PID controller 12 can detect the pressure detected by the pressure detector 11 at a predetermined set pressure. The opening degree of the regulating valve 6 is PID controlled.

  The lubricating oil separated by the oil separator 9 is supplied to the bearing portion of the screw expander 2 and the rotor chamber of the screw compressor 3 via the automatic temperature control valve 13, the oil cooler 14, and the oil filter 15. Moreover, when the screw expander 2 stops, the solenoid valve 16 is arrange | positioned so that supply of the lubricating oil to the bearing part of the screw expander 2 can be stopped immediately. Furthermore, the lubricating oil supplied to the bearing portion of the screw expander 2 flows into the speed reducer 4 to lubricate the speed reducer 4, and the lubricating oil flowing out of the speed reducer 4 is screw-compressed via the check valve 17. It is supplied to the rotor chamber of the machine 3.

  In the steam expander-driven air compressor 1 of the present embodiment, when the demand for compressed air is small, the pressure detected by the pressure detector 11, that is, the air pressure on the discharge side of the screw compressor 3 increases, so the PID control device 12. Thus, the opening degree of the capacity adjustment valve 6 for suction of the screw expander 2 is limited, and the amount of steam supplied to the screw expander 2 is reduced. As a result, the rotational speed of the screw expander 2 decreases and the discharge pressure of the screw compressor 3 also decreases, so the pressure on the discharge side of the screw compressor 3 (supply pressure to the demand facility of compressed air) decreases. Recover to the preset pressure.

  In addition, when the demand for compressed air is high, the pressure on the discharge side of the screw compressor 3 decreases, so the PID control device 12 opens the suction capacity adjustment valve 6 of the screw expander 2 widely. As a result, the rotational speed of the screw expander 2 increases and the discharge pressure of the screw compressor 3 also increases, so that the supply pressure of the compressed air increases and the set pressure is restored.

  More specifically, the output torque of the screw expander 2 that is a positive displacement steam expander is determined by the difference between the suction pressure and the discharge pressure. Similarly, the driving torque of the screw compressor 3, which is a positive displacement air compressor, is determined by the differential pressure between the intake pressure and the discharge pressure. For this reason, by adjusting the opening degree of the capacity adjusting valve 6 in accordance with the torque required for driving the screw compressor 3, the substantial intake pressure of the screw expander 2 is reduced. The output can be controlled to generate the desired pressure of compressed air.

  Thus, in this embodiment, since the steam flow rate of the screw expander 2 is adjusted according to the pressure of the compressed air, the differential pressure energy between the high-pressure steam supplied from the boiler and the low-pressure steam used in the regular equipment. Can be stably recovered as pneumatic energy, and compressed air with a constant pressure can be supplied.

  Further, in the present embodiment, the speed reducer 4 is configured so that the output of the screw expander 2 when the screw expander 2 is operated under an optimal condition is an optimum torque for compressing air by the screw compressor 3. Has slowed down. This optimizes the mechanical efficiency of the entire steam expander-driven air compressor 1 and increases the energy recovery efficiency.

  In the present embodiment, when the demand for steam is greater than the demand for compressed air, the steam can be supplied to the steam demand facility via the pressure reducing valve 7.

  The steam expander-driven air compressor of the present invention has a larger capacity steam expander and air compressor, particularly a rotary type that vibrates (during rotation) compared to a speed-type device such as a steam turbine. By using a screw expander and a screw compressor that have a small torque fluctuation due to the phase of the compressor, stable operation is possible regardless of fluctuations in demand for compressed air.

  In the present invention, the control based on the pressure on the discharge side of the air compressor of the capacity adjustment valve on the intake side of the steam expander is not limited to PID control, and any control may be used.

1 is a schematic diagram of a steam expander-driven air compression device according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Steam expander drive air compressor 2 ... Screw expander (volume type steam expander)
3 ... Screw compressor (displacement type air compressor)
DESCRIPTION OF SYMBOLS 4 ... Reducer 6 ... Flow control valve 7 ... Pressure reducing valve 11 ... Pressure detector 12 ... PID control apparatus

Claims (5)

A positive displacement steam expander;
A positive displacement air compressor driven by the positive displacement steam expander;
A capacity adjustment valve capable of adjusting an intake amount of the positive displacement steam expander;
A steam expander-driven air compressor, comprising: a controller that controls an opening of the capacity adjustment valve so that a pressure on a discharge side of the positive displacement air compressor is constant. A pressure detector for detecting the pressure on the discharge side of the positive displacement air compressor;
2. The steam expander-driven air compressor according to claim 1, wherein the control device performs PID control of an opening of the capacity adjustment valve based on a detection signal of the pressure detector.   The steam expander-driven air compressor according to claim 1 or 2, wherein the positive displacement steam expander drives the positive displacement air compressor via a speed reducer.   4. The steam expander-driven air compressor according to claim 1, wherein the positive displacement steam expander is a screw expander, and the positive displacement air compressor is a screw compressor. 5. .   5. The steam expander-driven air compressor according to claim 1, wherein an upstream side of the capacity adjustment valve and a discharge side of the positive displacement steam expander are connected via a pressure reducing valve.

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