JPH1162886A - Gas supplying system to plant and method for controlling it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas supplying system to a plant and a method for controlling it, capable saving power by effectively using gas wastefully discharged to the atmosphere instead of discharging the gas to the atmosphere. SOLUTION: In a gas supplying system to a plant, in which gas controlled by a suction valve 4 is supplied from a compressor 1 to a plant 5, and gas used in the plant 5 is guided to a gas expander 2 linked to the compressor 1 and discharged to the outside, a bypass line 6 for bypassing the plant 5 is provided on the downstream side of the compressor 1 and on the upstream side of the gas expander 2, an expander recovery valve 7 is interposed in the bypass line 6, the expander recovery valve 7 is opened, and discharged gas from the compressor 1 is partially guided to the gas expander 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for supplying gas to a plant having a compressor driven by both a gas expander and another driving device such as an electric motor and a steam turbine, and a control method thereof. .

[0002]

2. Description of the Related Art FIG. 4 is a piping diagram of a main part showing a conventional gas supply system for a plant, FIG. 5 is a characteristic diagram of a compressor used in the gas supply system, and FIG. It is a figure showing a control method of a suction valve and a blow-off valve. In this gas supply system, FIG.
As shown in FIG.
And another driving device 53 such as an electric motor and a steam turbine. Then, the gas discharged from the compressor 51 is supplied to the plant 54, and the gas that has completed work in the plant 54 is guided to the gas expander 52, and is discharged to the outside after being used for driving the compressor 51. . Further, in this gas supply system, the flow rate of gas flowing into the compressor 51 is controlled by the suction valve 55 to maintain a constant discharge pressure.

[0003]

In the gas supply system described above, when the amount of gas used in the plant 54 decreases, the discharge pressure of the compressor 51 is adjusted by the controller 5.
6, the discharge air volume of the compressor 51 is reduced by narrowing the suction valve 55 based on the discharge pressure. However, when the suction valve 55 is throttled, the surging pressure also decreases as is apparent from FIG. Then, when the discharge pressure rises to the surging pressure and the compressor 51 starts surging, the pressure and the flow rate fluctuate so strongly that the operation cannot be performed. In order to operate the compressor 51 near the rated pressure, the minimum opening of the suction valve 55 cannot be less than a predetermined value (minimum opening D). That is, it is necessary to lock the suction valve 55 so as not to be closed below a certain opening degree, and to operate while securing a minimum air volume that allows a sufficient margin between the operating pressure and the surging pressure. Therefore, if the gas consumption of the plant 54 further decreases while the opening of the suction valve 55 is at the minimum opening D, the controller 5
6, the blow-off valve 57 is opened to release a part of the gas discharged from the compressor 51 to the atmosphere as shown in FIG. 6, thereby preventing the compressor 51 from surging. Therefore, in the above gas supply system, the compressor power corresponding to the amount of air released was wasted.

[0004] The present invention has been made in view of such circumstances, and an object of the present invention is to make effective use of the gas that was wasted to the atmosphere by the conventional method without releasing it to the atmosphere. It is an object of the present invention to provide a gas supply system for a plant that saves power and a control method thereof.

[0005]

According to the present invention, a gas controlled by a suction valve is supplied from a compressor to a plant, and gas used in the plant is supplied to the compressor. In a gas supply system to a plant that guides to a linked expander and discharges the gas to the outside, a bypass line that bypasses the plant is provided downstream of the compressor and upstream of the expander, and the expander is collected in the bypass line. By interposing a valve and opening the expander recovery valve, a part of the gas discharged from the compressor is guided to the gas expander.

Further, according to the present invention, in the above configuration,
When the gas usage of the plant decreases, the suction valve is controlled in accordance with the gas usage to maintain the discharge side pressure of the compressor constant, and the gas usage of the plant is maintained at the minimum opening of the suction valve. Is further reduced, the expander recovery valve is controlled to open.

According to the present invention, when the gas usage of the plant fluctuates, the opening of the suction valve is controlled correspondingly,
This keeps the pressure on the discharge side of the compressor constant. When the gas usage of the plant decreases, the opening of the suction valve is reduced, but locked at a predetermined opening (minimum opening) to prevent surging. In addition, when the gas usage of the plant decreases, the expander recovery valve is opened,
Excess gas is led to the gas expander and used for driving the gas expander.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a piping diagram of a main part showing a gas supply system to a plant according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of a compressor used in the gas supply system,
FIG. 3 is a diagram showing a control method of a suction valve and an expander recovery valve used in the gas supply system.

In this gas supply system, as shown in FIG. 1, a compressor 1 includes a gas expander 2 and an electric motor,
It is designed to be driven by both other driving devices 3 such as a steam turbine. The gas is sucked into the compressor 1 with the flow rate controlled by the suction valve 4 as described later, and is compressed and discharged by the compressor 1. The discharged gas is sent to the plant 5, where the gas that has finished its work is led to the gas expander 2, where the gas expander 2
Drive. This gas expander 2 is a compressor 1
And assists the driving of the compressor 1. The gas after work is discharged to the outside.

On the other hand, in this gas supply system, a bypass line 6 for bypassing the plant 5 is provided downstream of the compressor 1 and upstream of the gas expander 2.
An expander recovery valve 7 is interposed in the bypass line 6, and an air release valve 8 is provided between the downstream side of the compressor 1 and the upstream of the plant 5. The suction valve 4, the expander recovery valve 7 and the blow-off valve 8 are controlled by the controller 9 based on the pressure on the discharge side of the compressor 1 as follows.

In this gas supply system, as shown in FIG. 1, a pressure on the discharge side of the compressor 1 is input to a controller 9 from a pressure detection line 10. Then, the detected pressure value is compared with a set value preset in the controller 9. Here, when the detected pressure value is equal to the set value (the point in FIG. 2), the current opening A of the suction valve 4 is maintained. When the detected pressure value is larger than the set value (the point in FIG. 2), the suction valve 4 is throttled from the current opening A to the opening B, whereby the compressor 1
The discharge pressure is reduced to the rated pressure (point in FIG. 2). On the other hand, when the detected pressure value is smaller than the set value (the point in FIG. 2),
The suction valve 4 is opened from the current opening degree A to the opening degree C, thereby increasing the amount of gas sucked into the compressor 1 and increasing the discharge pressure to the rated pressure (point in FIG. 2). In this way, the discharge pressure of the compressor 1 is maintained at a constant (rated pressure), but the amount of gas used in the plant 5 is greatly reduced, and the opening of the suction valve 4 is reduced to the minimum opening D accordingly. In that case, the opening of the suction valve 4 is locked there.

Here, when the opening of the suction valve 4 is at the minimum opening D and the gas usage of the plant 5 further decreases, that is, when the discharge pressure increases, the compressor 1
When the detected pressure value on the discharge side of the discharge reaches the preset value set in the controller 9, the expander recovery valve 7 is opened corresponding to the discharge pressure as shown in FIG.
A part of the gas discharged from the compressor 1 is guided to the gas expander 2 via Therefore, compressor 1
, The pressure on the discharge side of the compressor 1 is reduced, and surging of the compressor 1 is prevented. The gas expander 2 in this state is driven by gas directly guided from the compressor 1 via the recovery valve 7 and gas discharged from the plant 5.

If the control cannot follow the rapid fluctuation of the flow rate and the discharge pressure rises to the surging prevention unloader line, the blow-off valve 8 is opened by a command from the controller 9. The blow-off valve 8 is opened and blows off only when it is unavoidable to protect the compressor 1. In other cases, the blow-off valve 8 is operated without discharging to the atmosphere by the suction valve 4 and the expander recovery valve 7. Is done.

The above embodiment shows one form of control. For example, the control of the suction valve 4 and / or the expander recovery valve 7 can be performed in a stepwise or continuous manner. Various changes can be made without departing from the scope of the present invention.

[0016]

As described above, in the system for supplying gas to a plant and the method for controlling the same according to the present invention, the gas expander does not discharge the excess gas, which was wasted to the atmosphere by the conventional method, to the gas expander. Power recovery. Therefore,
The power of other driving machines can be reduced, and the power can be saved as a whole.

[Brief description of the drawings]

FIG. 1 is a main part piping diagram showing a gas supply system to a plant according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a compressor used in a system for supplying gas to a plant according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a control method of a suction valve and an expander recovery valve used in a system for supplying gas to a plant according to an embodiment of the present invention.

FIG. 4 is a main part piping diagram showing a conventional gas supply system to a plant.

FIG. 5 is a characteristic diagram of a compressor used in a conventional gas supply system for a plant.

FIG. 6 is a diagram showing a control method of a suction valve and a blow-off valve used in a conventional gas supply system for a plant.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Gas expander 3 Other drive machine 4 Suction valve 5 Plant 6 Bypass line 7 Expander recovery valve 8 Blow-off valve 9 Controller 10 Pressure detection line

Claims (2)

[Claims] In a gas supply system for a plant, a gas controlled by a suction valve is supplied from a compressor to a plant, and gas used in the plant is guided to a gas expander associated with the compressor and discharged to the outside. By providing a bypass line that bypasses the plant on the downstream side of the compressor and on the upstream side of the gas expander, providing an expander recovery valve in the bypass line, and opening the expander recovery valve. A gas supply system for a plant, wherein a part of the discharge gas of the gas is guided to the gas expander. 2. A gas supply system for a plant, wherein a gas controlled by a suction valve is supplied from a compressor to a plant, and gas used in the plant is guided to a gas expander associated with the compressor and discharged to the outside. By providing a bypass line that bypasses the plant downstream of the compressor and upstream of the gas expander, interposing an expander recovery valve in the bypass line, and opening the expander recovery valve, In a gas supply system to a plant that guides a part of the discharge gas from a compressor to the gas expander, when the gas usage of the plant decreases, the suction valve is controlled according to the gas usage to control the suction valve. Keep the discharge side pressure constant, and further increase the gas usage of the plant with the minimum opening of the suction valve. A method for controlling a gas supply system to a plant, wherein the expander recovery valve is opened when the gas supply amount decreases.