JP2724816B2 - Capacity control device of screw compressor for gas lift pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a screw compressor for a gas lift pump capable of controlling the capacity of a compressor. [Background of the Invention] The principle of a gas lift pump used for collecting natural gas is exactly the same as that of an air lift pump. A discharge pipe is inserted into a pumping pipe arranged in a well, and a compressor is inserted from the tip of the discharge pipe. The compressed gas compressed in the well is blown out into the well, and the well water containing natural gas is blown up in the pumping pipe, natural gas is separated and collected in the above-ground water tank, and a part of the natural gas is compressed by the compressor. It is sent to the discharge pipe in the well,
Currently, most natural gas is collected by gas lift pumps. By the way, reciprocating compressors are used as compressors for gas lift pumps, but as reciprocating compressors are well known, they have large vibrations and noises. It has an adverse effect. [Problems to be Solved by the Invention] In order to reduce vibration and noise which have been a problem in the compressor of the above gas lift pump, it is conceivable to use a screw compressor, but in the conventional screw compressor, However, there were the following problems. When natural gas is sampled by a gas lift pump, the natural water level of the well water in the pumping pipe is high for about 30 minutes after the start, so it is necessary to increase the capacity of the compressed gas sent to the discharge pipe in order to pump up the well water. And about after starting
After 30 minutes, the water level of the well water, the so-called operating water level, becomes low, and the well water spouts by its own injection and rises in the pumping pipe, so that it is almost unnecessary to send compressed gas to the discharge pipe. Therefore, it is desirable to control the capacity of the screw compressor with the passage of time. However, it is more difficult to control the capacity of the screw compressor as compared with a reciprocating compressor in which the discharge pressure of the compressed gas changes with clearance. Therefore, in order to apply the screw compressor to the gas lift pump, it is necessary to set the capacity of the screw compressor large in advance so as to be able to cope with the start of the gas lift pump. If the capacity of the screw compressor is constant and large, the high-pressure compressed gas is wastefully fed into the discharge pipe even when the well water has a low operating water level, which is extremely uneconomical. Met. An object of the present invention is to provide a capacity control device of a screw compressor for a gas lift pump that can control the capacity of the screw compressor according to a change in the water level of well water. [Means for Solving the Problems] In order to achieve the above object, a capacity control device for a screw compressor for a gas lift pump according to the present invention includes a compressor body having a built-in screw rotor for injecting oil and compressing gas. A screw compressor having an oil separator that separates oil from oil and compressed gas discharged from the compressor body and sends out compressed gas to the well, and natural gas pumped from the well by the compressed gas introduced from the screw compressor A gas well device that receives well water containing, separates water and sends out natural gas, a gas-liquid separator that removes moisture contained in the natural gas from a part of the natural gas sent from the gas well device, A gas lift pon consisting of a suction filter that filters the natural gas introduced from this gas-liquid separator and sends it to the compressor body In a displacement control device for a screw compressor for a pump, a control valve is provided in a suction pipe for communicating between a suction filter and a compressor body and opens and closes a flow passage in the suction pipe, and the control valve is operated by a pressure of a compressed gas. An actuator to be operated, a communication circuit between the actuator and the oil separator, a starting circuit for operating the actuator so as to open the control valve when the screw compressor is started, and a pressure regulating valve for high pressure which is connected between the actuator and the oil separator. A high-pressure circuit, a low-pressure circuit in which an actuator and an oil separator communicate with each other, and a low-pressure pressure-regulating valve, and a high-pressure circuit when the pressure of the compressed gas in the oil separator is high due to pumping of well water. By switching to a low pressure circuit when the pressure of the compressed gas is By switching it should do pressure regulating valve, in which the pressure regulating valve switching mechanism for operating the actuator to close the respective control valve, the provided. Then, in the capacity control device of the screw compressor for the gas lift pump, the pressure adjusting valve switching mechanism sets the time from the start of the operation of the screw compressor to the self-injection of the well water by the compressed gas from the data obtained in advance, for the high pressure. It is preferable to operate with a timer for switching from the pressure regulating valve to the low pressure regulating valve. Alternatively, the pressure regulating valve switching mechanism may operate the high pressure regulating valve and the low pressure regulating valve by a high pressure switch and a low pressure switch provided in the oil separator, respectively.
Alternatively, the pressure regulating valve switching mechanism may operate the high pressure regulating valve and the low pressure regulating valve based on a predetermined high detection value and a low detection value of the current sensor of the motor driving the compressor body, respectively. . [Operation] According to the above-described configuration, at the time of starting the screw compressor, first, by a starting circuit, the actuator is operated so that the control valve is opened, and as at the time of starting the screw compressor,
When the well water level of the gas well system is high and high-pressure compressed gas needs to be sent to the gas well system, it is switched to a high-pressure circuit by a pressure regulating valve switching mechanism, and the high-pressure compressed gas introduced into the actuator is used for high-pressure. When the pressure exceeds the high setting value of the pressure regulating valve, the actuator operates to close the suction pipe by the control valve, and the supply of gas to the compressor body stops. When a certain time has elapsed after the start of the screw compressor and the water level of the well water has dropped and the pressure of the compressed gas sent to the gas well device can be low, the pressure is switched to a low pressure circuit by a pressure regulating valve mechanism, and the low pressure When the compressed gas exceeds the high set value of the low-pressure pressure regulating valve, the actuator operates to close the suction pipe by the control valve, and the unload operation of the screw compressor is performed in the well water self-injection state. [Examples] Hereinafter, the present invention will be described based on examples shown in the drawings. The gas lift pump 1 includes a screw compressor 2, a gas well device 3 to which compressed gas is supplied from the compressor 2, and a cyclone separator 4 as an example of a gas-liquid separator that separates moisture from natural gas ejected from the gas well device 3. And a suction filter 5 for filtering gas supplied from the cyclone separator 4, and a capacity control device 6 for controlling supply or stoppage of gas introduced from the suction filter to the screw compressor 2. The screw compressor 2 generally includes a compressor body 8, an oil separator 10 for separating oil contained in gas discharged from the compressor body 8, and an oil cleaner 11 for removing dust from the oil separated by the oil separator 10. Oil cooler that cools the oil purified by the oil cleaner 11
It has 12 and. The compressor body 8 has a gas inlet 13
A, a discharge port 14 for compressed gas, and an injection hole 15 for injecting cooled oil into the compressor body 8 are formed therein, and male and female screw rotors 16 are rotatably provided therein. It is arranged. The screw rotor 16 is a motor 18
When rotated by, the gas sucked in from the suction port 13A is compressed by the screw rotor 16, and is discharged together with the oil injected from the injection hole 15 toward the screw rotor 16.
Discharged from 14. The oil separator 10 is connected to the compressor body 8 by a pipe 20A.
The oil is separated from the compressed gas and the oil introduced through the pipe 20A by a separate element 21 disposed above the oil separator 10. The bottom of the oil separator 10 is
The pipe 20B communicates with the injection hole 15 of the compressor body 8. The oil cleaner 11 is provided in the middle of the pipe 20B, and removes dust in oil. The oil cooler 12 communicates with a lower portion of the oil separator 10 and a branch pipe 22A branched from the pipe 20B. The oil stored at the bottom of the oil separator 10 is injected from the injection hole 15 toward the screw rotor 16 through the oil cleaner 11 and the oil cooler 12. 23A is a discharge temperature relay arranged on the pipe 20A, 24A
Is a temperature control valve disposed on the branch pipe 22A. The gas well device 3 includes a pumping pipe 28 buried in a well 26.
And the separate element 21 inserted into the pumping pipe 18.
And a well chamber 30 communicating with a pumping pipe 28 protruding above the ground, and the pipe 20C extends to near the bottom of the well. A pressure regulating valve 31 and a discharge temperature relay 23B are provided in the pipe 20C. The cyclone separator 4 is connected to the well room 30 by the pipe 20D.
, And separates the water of the well water contained in the gas pumped into the well chamber 30, for example, methane gas. The suction filter 5 is a suction case 3 connected to the cyclone separator 4 by a pipe 20E.
4 and the piping 20E is connected to the suction case 34.
The methane gas introduced through is filtered. Piping from well room 30 to cyclone separator
A branch pipe 22B branched from 20D communicates with a pipe 20C from the oil separator 10 to the pumping pipe 28 via a safety valve 35. The displacement control device 6 includes a control valve 36, a cylinder mechanism 38 as an example of an actuator, a low pressure circuit 39 and a high pressure circuit 40.
And a pressure regulating valve switching mechanism 41 (FIG. 2). The control valve 36 is disposed in a suction pipe 43 that communicates the suction filter 5 with the compressor body 8, and a suction port 13B formed at one end of the suction pipe 43 communicates with the suction filter 5 through a pipe 20F. The other end is the suction port 13A of the compressor body 8.
Is in communication with The control valve 36 adjusts the opening of the suction port 13B to control the volume of the gas drawn into the suction port 13A of the compressor body 8. The cylinder mechanism 38 includes a cylinder case 45 and a piston 46.
The piston 46 is slidably fitted in a cylinder chamber 48 formed in the cylinder case 45, and a piston rod 50 is integrally formed. Cylinder chamber 48
A control valve 36 is fixed to the tip of a piston rod 50 that protrudes outward, and a compression spring 51 is loosely fitted to the piston rod 50 and interposed between the control valve 36 and the outer wall of the cylinder chamber 48, and the compression valve The control valve 36 is urged in the direction of arrow A by the spring 51. The low pressure circuit 39 and the high pressure circuit 40
Is disposed in parallel with a branch pipe 22C branched from the pipe 20C on the gas outlet side, and communicates via a communication hole 52 with a left cylinder chamber 48A divided by a piston 46. Also low voltage circuit 3
9, a low-pressure solenoid valve 64 and a low-pressure output adjusting valve 53 are sequentially arranged from the pipe 20C side.
A high-pressure solenoid valve 54 and a high-pressure control valve 54 are provided sequentially from the 20C side. Further, the unloading solenoid valve 5 is sequentially provided from the upstream side to the branch pipe 22E further branched from the branch pipe 22C.
6, the pressure reducing valve 58 is provided, the branch pipe 22E is a piston
The right cylinder chamber 48B divided by 46 is communicated through a communication hole 60. The pressure regulating valve switching mechanism 41 includes, for example, a timer 61 as shown in FIG. 2. The solenoid valve 65 of the high voltage circuit 40 is connected to the timer contact 62A, and the low voltage circuit 39 is connected to the timer contact 62B.
The solenoid valve 64 is operated to switch between the high-pressure control valve 54 and the low-pressure control valve 53. In FIG. 1, reference numeral 66 denotes an air discharge solenoid valve which is opened when the screw compressor 2 stops, and discharges the compressed gas in the cylinder chamber 48 to the upstream side of the suction filter 5. Reference numeral 68 denotes a stop solenoid valve which is opened when the screw compressor 2 stops, so that oil supplied to the compressor body 8 does not flow into the suction pipe 43. That is,
When the screw compressor 2 is stopped, since the gas pressure in the oil separator 10 downstream of the compressor body 8 is high, the oil stored at the bottom of the oil separator 10 is removed by an oil cleaner.
11, flows backward to the compressor 8 through the oil cooler 12, and further flows into the suction pipe 43. In order to prevent this backflow, a high gas pressure in the oil separator 10 is applied to the downstream side of the check valve 80 disposed between the oil cooler 12 and the compressor body 8 through the solenoid valve 68. The screw compressor 2 and the capacity control device 6 are covered with a soundproof cover 70 and are shielded from the outside. Next, the operation of the embodiment of the present invention will be described. When the screw compressor 2 starts, the unload solenoid valve 56 opens, and from the valve 56, through the pressure reducing valve 58 to the cylinder chamber 48B,
The compressed gas from the screw compressor 2 is introduced, and the control valve 36 moves to a position having a sufficient gap with the suction port 13B due to the balance between the gas pressure and the spring force of the compression spring 51. Here, the branch pipe including the unload solenoid valve 56 and the pressure reducing valve 58 functions as a starting circuit. The screw rotor 16 is rotated by the motor 18 and the discharge port
The discharge pressure of the compressed gas discharged from 14 rises to 4.5 kgf / c
When the pressure exceeds m ² g, the pressure regulating valve 31 downstream of the gas from the oil separator 10 opens, and the compressed gas passes through the pipe 20C to the well 26.
Ejects from near the bottom. Then, the discharge pressure gradually increases, and after a certain period of time, for example, 30 minutes, becomes 15 kgf / cm ² g, and the natural water level head of the well water in the pumping tube 28 rises to WH. While the gas pressure rises from 4.5 kgf / cm ² g to 15 kgf / cm ² g, the timer contact of the high-pressure solenoid valve 65
Since 62A is ON, the high-pressure solenoid valve 65 is energized and opened, and the gas circuit between the high-pressure circuit 40 and the high-pressure pressure regulating valve 54 communicates via the high-pressure solenoid valve 65, and the high-pressure Gas pressure is applied to the regulating valve 54. At this time, since the timer contact 62B of the low-pressure solenoid valve 64 is OFF, the low-pressure solenoid valve 64 is non-conductive and closed, and the gas circuit between the low-pressure circuit 39 and the low-pressure pressure regulating valve 53 is shut off. Is done. Therefore, for about 30 minutes from the start of the screw compressor 2,
The high pressure control valve 54 of the high pressure circuit 65 does not operate, and the control valve 36
When the discharge pressure reaches 15 kgf / cm ² g, the high-pressure regulating valve 54 is opened and the compressed gas introduced into the left cylinder chamber 48A is opened. As a result, the piston 46 is pressed in the direction of arrow A, the control valve 36 closes the suction port 13B, and the supply of gas to the screw rotor 16 is stopped. When the well water is pumped after about 30 minutes from the start of the screw compressor 2, the well water head drops to the operating water level WL, so that the pressure of the oil separator 10 naturally drops to 10 kgf /
It stabilizes at cm ² g and becomes well water spouting. Then, the operation of the timer 61 causes the timer contact 62B of the low-pressure solenoid valve 64 to operate.
Is turned ON, the low-pressure solenoid valve 64 is energized and opened, and the gas circuit of the low-pressure circuit 39 and the low-pressure pressure regulating valve 53 communicates,
When the gas pressure becomes equal to or more than the set value of the low-pressure regulating valve 53 (10 kgf / cm ² g), the low-pressure regulating valve 53 is opened, and the control valve 36 closes the suction port 13B. At this time, since the timer contact 62A of the high-pressure solenoid valve 65 is OFF, the high-pressure solenoid valve 65 is not energized and closed, and the gas circuit between the high-pressure circuit 40 and the high-pressure pressure adjustment valve 54 is Will be shut off. Therefore, 30 minutes after the start of the screw compressor 2,
When the well water is self-injected at a stable discharge pressure of 10 kgf / cm ² g of the screw compressor 2, the capacity of the screw compressor 2 is controlled by the low-pressure pressure regulating valve 53, and the left cylinder chamber
The piston 46 is moved by the arrow A due to the compressed gas introduced into 48A.
, The suction port 13B is closed by the control valve 36, the supply of gas to the screw rotor 16 is stopped,
A no-load operation of the screw compressor 2, that is, an unload operation is performed. FIGS. 3 and 4 show an embodiment in which a pressure switch is used for the pressure regulating valve switching mechanism 41.
A pressure switch 71 for high pressure, a solenoid valve 72 for pressure switch, and a pressure switch 73 for low pressure are disposed in this order from the upstream side.The pressure switch 71 for high pressure has a gas pressure of 15 kgf / cm ² g.
As described above, it is turned off, the high pressure regulating valve 54 (FIG. 1) is opened, and the control valve 36 is closed via the actuator 38. On the other hand, it is turned on at 15 kgf / cm ² g or less, The setting is such that the control valve 36 is opened while the pressure regulating valve 54 is closed. The low pressure switch 73 has a gas pressure of 10 kgf / cm
^It turns ON at ² g or more, turns off at 10 kgf / cm ² g or less, and closes the low-pressure pressure regulating valve 53 so that the low-pressure pressure regulating valve 53 (FIG. 1) opens and the control valve 36 closes. The control valve 36 is set to open. The relays 75 and 76 shown in FIG.
It corresponds to each electromagnetic coil of the high-pressure solenoid valve 65 and the low-pressure solenoid valve 64 shown in the figure. Therefore, as described in FIGS. 1 and 2, the gas pressure is 15 kgf / cm ² g or less until the well water rises to the natural water level head WH after the screw compressor 2 is started, and Since the contact of the pressure switch 71 is ON, the high-pressure solenoid valve 65 is energized and opened by the relay 75, and the high-pressure circuit 40 and the high-pressure pressure regulating valve 54 communicate with each other to connect to the high-pressure pressure regulating valve 54. Gas pressure is applied, gas pressure is 15kgf / cm ² g
When this occurs, the high pressure control valve 54 opens and the high pressure circuit
From 40, compressed gas is introduced into the left cylinder chamber 48A and the control valve 3
6 closes the inlet 13B. During the period from the start of the screw compressor 2 until the gas pressure reaches 15 kgf / cm ² g, the solenoid valve 72 for the pressure switch is closed without electricity and the gas circuit with the pressure switch 73 for the low pressure is shut off. Thirty minutes after the start of the screw compressor 2, the well water head drops to the operating water level WL as described above, and the gas pressure in the oil separator 10 also drops to about 10 kg.
Stable at f / cm ² g. During this time, the high pressure switch 71 is turned off at a gas pressure of 15 kgf / cm ² g.
When 5 is cut off, the high-pressure solenoid valve 65 is closed without electricity, and the communication between the high-pressure control valve 54 and the high-pressure circuit 40 is cut off. On the other hand, the pressure switch solenoid valve 72 is energized and opened, and the gas circuit of the branch pipe 22C and the low-pressure pressure switch 73 communicates.At first, since the gas pressure is 15 kgf / cm ² g, the instantaneous low-pressure pressure switch 73 Turns ON. Then, the relay 76 is activated, and the low-voltage solenoid valve 64 is energized and opened, and the low-voltage circuit 39 is opened.
And the low-pressure control valve 53 communicate with each other so that the low-pressure control valve 53
When the gas pressure is 10 kgf / cm ² g or more, the low pressure regulating valve 53 is opened, the compressed gas is introduced from the low pressure circuit 39 into the left cylinder chamber 48A, and the control valve 36 closes the suction port 13B. At the time of the well water self-injection, the unload operation of the screw compressor 2 is easily performed in the same manner as described with reference to FIGS. Further, a current sensor that detects the current of a motor that drives the screw compressor 2 may be used as the pressure adjustment valve switching device 41. In this case, the maximum current (gas pressure 15 kgf / cm ²⁾ until the well water is pumped up. Until g) is detected, the high-pressure solenoid valve 65 is opened. After this, the pressure inside the oil separator 10 becomes 10
Since the pressure drops to kgf / cm ² g, this decrease in current is detected, the high-pressure solenoid valve 65 is closed, and the low-pressure solenoid valve 64 is opened instead, and the same control as described above is performed. [Effects of the Invention] As described above, according to the present invention, when the self-injection of well water occurs when the gas lift pump is stable, the unloading operation can be easily performed. It can be greatly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram of a gas lift pump, FIG. 2 is a sequence control diagram of a solenoid valve switching device using a timer, and FIG. 3 is a gas lift pump using a pressure switch in the solenoid valve switching device. FIG. 4 is a sequence control diagram of the solenoid valve switching device shown in FIG. 1 ... Gas lift pump, 2 ... Screw compressor, 3
... gas well device, 4 ... cyclone separator as an example of gas-liquid separator, 5 ... suction filter, 6 ... capacity control device, 8 ...
... Compressor body, 10 ... Oil separator, 16 ... Screw rotor, 36 ... Control valve, 38 ... Cylinder mechanism as an example of actuator, 39 ... Low pressure circuit, 40 ... High pressure circuit, 41 ... Pressure adjustment Valve switching mechanism, 43… Suction pipe, 53… Pressure adjusting valve for low pressure, 54… Pressure adjusting valve for high pressure, 61
… Timer, 71… Pressure switch for high pressure, 73… Pressure switch for low pressure.

Claims (1)

(57) [Claims] Oil is injected, a screw compressor having a compressor body having a built-in screw rotor for compressing gas, and an oil separator that separates oil from oil and compressed gas discharged from the compressor body and sends compressed gas to a well. Receiving well water containing natural gas pumped from the well by the compressed gas introduced from the screw compressor,
A gas well device that separates water and sends out natural gas, a gas-liquid separator that removes moisture contained in the natural gas from a part of the natural gas sent from the gas well device, and a gas-liquid separator that is introduced from the gas-liquid separator. A capacity control device for a screw compressor for a gas lift pump, comprising a suction filter for filtering natural gas that has been filtered and sending the natural gas to the compressor body, wherein the suction device is disposed in a suction pipe for communicating between the suction filter and the compressor body. A control valve for opening and closing the pipe flow path, an actuator for operating the control valve by the pressure of the compressed gas, and a communication between the actuator and the oil separator so that the control valve is opened when the screw compressor starts. A starting circuit for operating the actuator, and a high-pressure circuit for communicating between the actuator and the oil separator. A high pressure circuit for force control valve is disposed,
A low-pressure circuit in which the actuator and the oil separator are communicated with each other and a low-pressure pressure regulating valve is provided; By switching to the low-pressure circuit when the pressure of the well water is low in the self-injection state of the well water, a pressure regulating valve switching mechanism that switches the pressure regulating valve to be operated and operates the actuator to close the control valve, respectively. A capacity control device for a screw compressor for a gas lift pump, which is provided. 2. A timer for setting the time from the start of operation of the screw compressor to the self-injection of well water by compressed gas from the data obtained in advance and switching the pressure regulating valve switching mechanism from the high pressure regulating valve to the low pressure regulating valve. 2. The displacement control device for a screw compressor for a gas lift pump according to claim 1, wherein the displacement control device is operated by the following. 3. The pressure regulating valve switching mechanism operates the high pressure regulating valve and the low pressure regulating valve by a high pressure switch and a low pressure switch provided in the oil separator, respectively. 3. The capacity control device for a screw compressor for a gas lift pump according to claim 1. 4. The pressure regulating valve switching mechanism operates the high pressure regulating valve and the low pressure regulating valve based on a predetermined high detection value and a low detection value of a current sensor of a motor that drives the compressor body, respectively. The capacity control device for a screw compressor for a gas lift pump according to claim 1, characterized in that: