JP6720802B2 - Water addition start method of water addition type compressor - Google Patents

Description

The present invention relates to a water addition start method used for a water addition type compressor.

Conventionally, a water-added compressor that compresses air to which water is added is known. Patent Document 1 discloses a water-added compressor of this type. Patent Document 1 describes a configuration of a orbiting scroll compressor in which water is injected into a compression path, in which water injection is started after operation of a drive device is started.

JP, 2011-163219, A

When water is added, the performance of the compressor is improved due to the sealing effect, and the amount of compressed air discharged is increased, so a sudden torque may be applied at the moment of adding water, and the drive of the compressor may become unstable. Further, even when the discharge valve arranged on the discharge side of the compressor is closed, the compressor is loaded and the rotation speed is reduced. Patent Document 1 describes a control in which a non-water injection operation is performed in a state where the electromagnetic air release valve and the water injection control valve are closed, and the water injection control valve is opened to shift to the water injection operation after a predetermined time has elapsed, but the operation is started. Since the electromagnetic release valve is sometimes closed, a load is applied to the drive of the compressor at the start of operation. There is room for improvement in the conventional technology in that the rotational speed is stably increased from the start of operation.

It is an object of the present invention to provide a water addition start method that realizes stable start-up of a water addition compressor by adjusting the timing of the load on the compressor at the start of operation.

The present invention is a method for starting water addition of a water-added type compressor, in which a discharge valve is opened so that compressed air of the compressor is discharged from a drive source in a state of being opened to the atmosphere. To the compressor after the drive start step of starting the drive of the compressor by the drive force, after the drive start step, the exhaust valve closing step of closing the exhaust valve, and the exhaust valve closing step. And a step of supplying additional water for starting the supply of additional water.

In the added water supply step, it is preferable to start the supply of added water after a preset set time has elapsed.

In the added water supply step, it is preferable that the drive torque information indicating the drive torque of the compressor is acquired and the supply of the added water is started when it can be determined that the drive torque exceeds a predetermined value.

In the air release valve closing step, it is preferable that the rotation speed information indicating the drive rotation speed of the compressor be acquired and the air release valve be closed when it can be determined that the drive rotation speed exceeds a predetermined value.

According to the water addition start method for a compressor of the present invention, stable start of the water addition compressor can be realized by adjusting the timing of the load applied to the compressor at the start of operation.

1 is a schematic diagram of an air compression system to which a water addition starting method according to an embodiment of the present invention is applied.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the "line" in this specification is a general term for lines through which a fluid can flow, such as a flow path, a route, and a pipeline.

FIG. 1 is a schematic diagram of an air compression system 1 to which a water addition start method according to an embodiment of the present invention is applied. As shown in FIG. 1, an air compression system 1 according to the present embodiment includes a water-added compressor 2, an electric motor 20 as a prime mover of the compressor 2, and a compressed-air compressed water discharged from the compressor 2. The separator tank 3 that performs the separation, the aftercooler 34 that cools the compressed air separated in the separator tank 3, and the control unit 90 that performs various controls are provided as main components.

<Compressor>
The compressor 2 is a water addition type air compressor. The compressor 2 of the present embodiment is configured as a scroll type, and by rotating the orbiting scroll with respect to a fixed scroll (neither of which is shown), air is compressed and compressed air containing added water is discharged. In the present embodiment, a scroll fluid machine is used in which orbiting wraps are provided on both sides of the orbiting scroll, and a pair of fixed scrolls are arranged so as to sandwich the orbiting scroll. The compressor 2 may be other than the scroll type, for example, a screw type compressor.

An electric motor 20 is used as a drive source of the compressor 2 of this embodiment. The rotation speed of the electric motor 20 is controlled by the drive frequency output from the inverter 21. It should be noted that a drive source other than the electric motor 20, for example, a steam engine driven by steam (for example, a scroll type expander) can be used.

Air is supplied to the compressor 2 as a fluid to be compressed from the air supply line L1. An air filter 22 is arranged in the air supply line L1, and the clean air that has passed through the air filter 22 is supplied to the compressor 2.

A water supply line L2 and a return line L3 are connected to the air supply line L1 downstream of the air filter 22. Both the water supply line L2 and the return line L3 are lines for supplying the additive water to the compressor 2.

The water supply line L2 has an upstream end connected to a water supply source (not shown), and supplies supplementary supplemental water from the water supply source to the air supply line L1. A water supply valve 24 is arranged in the water supply line L2. The water supply valve 24 is a solenoid valve that operates according to a command from the control unit 90, and controls the supply, stop, and flow rate of the added water to the compressor 2 through the water supply line L2.

The return line L3 is connected to the liquid phase portion of the separator tank 3, and the separated water generated by the air-water separation of the separator tank 3 is supplied to the air supply line L1 through the return line L3 and added to the compressor 2 as added water. Will be reused in. In the return line L3, a water cooler 25, a water filter 23, and an added water valve 30 are arranged in this order from the upstream side. The water flowing out of the separator tank 3 and flowing through the return line L3 is cooled by the water cooler 25, filtered by the water filter 23, and sent to the air supply line L1. The added water valve 30 is a solenoid valve that operates according to a command from the control unit 90, and controls the supply, stop, and flow rate of the added water to the compressor 2 through the return line L3.

The additive water valve 30 is opened during the operation of the compressor 2, and the water supply valve 24 is opened during the operation of the compressor 2 when the water reduction in the separator tank 3 is detected. Then, the air added with the water supplied from the return line L3 (or both the return line L3 and the water supply line L2) is supplied to the air suction port of the compressor 2 through the air supply line L1 and sent into the compression chamber. .. The water-added compressor 2 can also be referred to as a water-lubricated compressor or a water-injected compressor, and these compressors 2 are also included.

<Separator tank>
The separator tank 3 is a steam separator that separates water from compressed air. Compressed air containing water is sent from the compressor 2 to the separator tank 3 through the discharge line L4 in which the check valve 31 is arranged, and is separated into compressed air and water in the separator tank 3. The inside of the separator tank 3 is divided into an upper gas phase part and a lower liquid phase part by separating water and water. In addition, the discharge line L4 of the present embodiment serves as a path for taking out compressed air from each of the scroll mechanisms on both sides of the compressor 2 and joining the compressed air to the separator tank 3, and the check valve 31 joins the compressed air. Is located downstream of.

After being separated into water and water in the separator tank 3, the compressed air is sent to the device using compressed air (not shown) through the compressed air delivery line L5 connected to the gas phase portion of the separator tank 3. A primary pressure adjusting valve 33, an aftercooler 34, and a pressure sensor 37 are arranged in this order from the upstream side in the compressed air delivery line L5. The internal pressure of the separator tank 3 is maintained at a set pressure or higher by the primary pressure adjusting valve 33. The compressed air flowing through the compressed air delivery line L5 is cooled by the aftercooler 34 and then sent to the device using compressed air. The pressure sensor 37 detects the discharge pressure of the compressed air and sends the discharge pressure information to the control unit 90.

An air discharge line L6 is connected to the gas phase portion of the separator tank 3. An air discharge valve 40 that opens the inside of the separator tank 3 to the atmosphere (outside) is arranged in the air discharge line 6. The air release valve 40 is a solenoid valve that operates according to a command from the control unit 90, and when the air release valve 40 opens, the inside of the separator tank 3 is opened to the atmosphere. That is, the discharge side of the compressor 2 is opened to the atmosphere through the separator tank 3 and the discharge line L4. During operation of the compressor 2 (after transition to a steady state), the air discharge valve 40 is controlled to be in a closed state.

In the discharge line L6 of the present embodiment, a pressure sensor 41 as a pressure detection unit that detects the pressure inside the separator tank 3 and a safety valve 42 that operates when the internal pressure of the separator tank 3 becomes a predetermined value or more are arranged. The pressure information detected by the pressure sensor 41 is transmitted to the control unit 90.

A water level detector 32 for detecting the water level inside is disposed in the separator tank 3. The water level detector 32 detects the water level inside the separator tank 3 and transmits water level information to the control unit 90. The configuration of the water level detector 32 is not particularly limited, and a float type or electrode type level switch, a capacitance type level sensor, or the like is used. In this embodiment, the water level detector 32 that can detect a low water level, a medium water level, and a high water level is used.

A drain line L7 is connected to the liquid phase portion of the separator tank 3. A drain valve 50 is arranged in the drain line L7. The drain valve 50 is a solenoid valve that operates according to a command from the control unit 90, and when the drain valve 50 opens, the water inside the separator tank 3 is discharged to the outside through the drain line L7.

<After cooler; water cooler>
The aftercooler 34 is a heat exchanger that is disposed in the compressed air delivery line L5 and cools the compressed air that passes through the compressed air delivery line L5. Cooling water is supplied to the aftercooler 34 as a cooling medium through a cooling water line L8. A motor valve 35 is arranged in the cooling water line L8, and the supply of cooling water is controlled by the motor valve 35. The flow path of the cooling water inside the aftercooler 34 and the flow path of the compressed air are separate, and heat exchange is performed without the cooling water and the compressed air being mixed with each other. The compressed air is cooled by the heat exchange and the cooling water is heated.

The cooling water sent through the cooling water line L8 exits the after cooler 34 and is then sent to the water cooler 25. The flow path of the cooling water inside the water cooler 25 and the flow path of the water returned from the return line L3 are separate, and the heat exchange is performed without the cooling water and the water flowing through the return line L3 being mixed. As a result, the added water flowing through the return line L6 is cooled by the cooling water, and the cooling water becomes hot water. This hot water is used as, for example, water supply for a steam boiler (not shown), or used in various hot water-using devices (not shown).

<Control part>
The control unit 90 is electrically connected to each sensor, each solenoid valve, and the like, and performs various controls of the air compression system 1 based on information of the sensor or the like and a command signal input by a user or the like.

The main configuration of the air compression system 1 of this embodiment is as described above. During operation of the compressor 2, the control unit 90 drives the electric motor 20 via the inverter 21 and air added with water by the compressor 2 through the return line L3 (or both the return line L3 and the water supply line L2). Compress. The compressed air containing water discharged from the compressor 2 is separated into compressed air and water in the separator tank 3. The compressed air separated by the separator tank 3 is cooled by the aftercooler 34 and then sent to the device using compressed air. The control unit 90 controls the drive of the electric motor 20 while monitoring the pressure detected by the pressure sensor 37. The water separated in the separator tank 3 is cooled in the return line L3 by the water cooler 25, filtered by the water filter 23, and then reused in the compressor 2 through the air supply line L1.

<Water addition start control>
Next, the control at the time of starting the compressor 2 will be described. In the present embodiment, when the compressor 2 is started, the addition of water to the compressor 2 is started by following the steps of the drive start step, the air release valve closing step, and the added water supply step.

When the control unit 90 receives the operation start command of the compressor 2, it controls the air release valve 40 to the open state and sends a command signal to the inverter 21, and the inverter 21 drives the electric motor 20 by frequency control based on the command signal. The process proceeds to the drive start step for driving.

In the drive start step, the drive of the electric motor 20 is started with the separator tank 3 (discharge side) being open to the atmosphere. As a result, compared with the case where the electric motor 20 (motor) is driven in a state where the discharge valve 40 is closed and the pressure on the discharge side of the compressor 2 is high, the load applied to the rotation of the compressor 2 is increased. Is reduced and the rotation speed can be increased smoothly. After this driving start step, the flow proceeds to the air release valve closing step.

In the air release valve closing step, the control unit 90 monitors the drive frequency of the inverter 21 as drive rotation speed information indicating the drive rotation speed of the compressor 2. After determining that the drive rotation speed of the compressor 2 has exceeded the predetermined rotation speed set in advance based on the drive frequency, the control unit 90 controls the discharge valve 40 to the closed state. The predetermined rotation speed is theoretically or empirically set to a rotation speed at which the drive is not stopped by the load of the discharge valve 40 even when the discharge valve 40 is closed. After this air release valve closing step, the process proceeds to the water addition and supply step. It is also possible to dispose a revolution counter in the compressor 2 and use the detected revolution speed of the revolution counter as the drive revolution information.

In the water addition supply step, the control unit 90 controls the addition water valve 30 to be in the open state and opens the path of the return line L3 after the set time has elapsed after closing the discharge valve 40. As a result, the stored water in the separator tank 3 is introduced into the compressor 2 as added water.

The set time is set as a time that can secure a torque that can withstand the load caused by the addition of water, and is set by calculation or an actual measurement value according to the device configuration, specifications, and the like. As the set time elapses, the torque rises to a value that can withstand the load caused by water addition. After the water addition is started in the water addition supply step, the compressor 2 shifts to a steady state. The air that has been compressed together with the added water in the compressor 2 is separated into steam and water in the separator tank 3, then cooled in the aftercooler 34 and sent to a device using compressed air (not shown).

According to this embodiment described above, the following effects are achieved.
The water addition start method of the water addition type compressor 2 of the present embodiment is an electric power source as a drive source in a state where the discharge valve 40 is opened and the discharge side of the compressor 2 from which compressed air is discharged is open to the atmosphere. A drive start step of starting the drive of the compressor 2 by the drive force transmitted from the motor 20, a release valve closing step of closing the release valve 40 after the drive start step, and a compression step after the release valve closing step. An additional water supply step of starting the supply of the additional water to the machine 2.

As a result, the rotational speed of the compressor 2 can be smoothly increased without being affected by the load due to the closing of the discharge valve 40 in the initial stage of startup. Moreover, since the closing of the air release valve 40 that applies a load to the rotation of the compressor 2 and the start of water addition are not performed at the same time, it is possible to prevent a situation in which the rotation speed greatly stalls and becomes unstable. In the present embodiment, since water with a large load is added after closing the air discharge valve 40, the torque has risen to a sufficient value at the time of starting the water addition, and the rotation speed sharply drops due to the load of water addition. You can definitely avoid the situation. In the initial stage of driving the electric motor 20 (or the steam engine) as a drive source, the rotation speed is increased in a no-load state, and the timing of the exhaust valve 40, which serves as a brake for torque, is closed and water is added in stages. By shifting, the water-added compressor 2 can be stably and efficiently started.

In addition, in the added water supply step of the present embodiment, the supply of added water is started after a preset set time has elapsed.

With this, by setting the set time based on the device specifications and the like, it is possible to stabilize the startup of the compressor 2 by a simple process without performing complicated control.

Further, in the air release valve closing step of the present embodiment, the frequency information of the inverter 21 is acquired as the rotation speed information indicating the drive rotation speed of the compressor 2, and it is determined from the frequency information that the drive rotation speed exceeds the predetermined value. The air release valve 40 is closed when possible.

As a result, the rotation speed of the compressor 2 can be reliably increased to the target value before the air release valve 40 is closed, and the startup of the compressor 2 can be further stabilized.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be modified as appropriate.

In the added water supply step of the above embodiment, the method of supplying the added water to the compressor 2 after the set time has elapsed after closing the air release valve 40 is adopted, but the trigger for starting the water addition is limited to this. Not done. Next, a modified example in which the timing of starting the supply of the added water in the added water supply step is different from that of the above embodiment will be described. The system configuration itself is the same as in the above embodiment.

In the modified water supply step of the modification, the driving torque information indicating the driving torque of the compressor 2 is acquired, and the supply of the additional water is started when it can be determined that the driving torque exceeds the predetermined value.

As a result, the drive torque of the compressor 2 that is actually operating is reflected, so that the timing of starting the supply of water addition can be made more accurate.

As the driving torque information, for example, the following can be used. That is, the torque information may be calculated based on the drive frequency of the inverter 21, the rotational speed information of the compressor 2 by the rotational speed meter, and the pressure detected by the pressure sensor 41. Alternatively, a torque sensor may be arranged to directly detect the torque. In addition, the change in the current value of the electric motor 20 may be used for calculating the rotation speed and the torque, and when a steam engine using steam as an energy source is used as the drive source of the compressor 2, the differential pressure of the steam is changed. A method of calculating torque using information or the like may be used.

In this way, the drive rotation speed and drive torque of the compressor 2 can be calculated and acquired by an appropriate method according to the circumstances.

Further, the present invention is not limited to the configuration of the air compression system 1 described in the above embodiment, and can be applied to various water-added compressors. For example, the present invention can be applied to a system in which a pre-separator tank is arranged before the separator tank and a heat exchanger is arranged between the separator tank and the pre-separator tank.

2 compressor 20 electric motor (driving source)
30 addition water valve 40 release valve

Claims (4)

A method of starting water addition of a water addition type compressor,
A driving start step of starting driving of the compressor by a driving force transmitted from a driving source in a state in which a discharge valve is opened to open a discharge side of the compressed air of the compressor to the atmosphere,
An exhaust valve closing step of closing the exhaust valve after the drive starting step;
And a step of supplying additional water to the compressor after the step of closing the air release valve. In the additive water supply step,
The water addition start method according to claim 1, wherein the supply of the added water is started after a preset set time has elapsed. In the additive water supply step,
The water addition start method according to claim 1, wherein the driving torque information indicating the driving torque of the compressor is acquired, and the supply of the added water is started when it can be determined that the driving torque exceeds a predetermined value. In the air release valve closing step, rotation speed information indicating a drive rotation speed of the compressor is acquired, and the air release valve is closed when it can be determined that the drive rotation speed exceeds a predetermined value. The method for starting water addition according to any one of 1.

Images