JP4852003B2 - Reciprocating compressor capacity adjustment method - Google Patents

Description

  The present invention relates to a capacity adjustment method for a reciprocating compressor, and more specifically, a reciprocation capable of realizing stepwise capacity adjustment from 0% to 100% without a head end unloader (clearance pocket). The present invention relates to a capacity adjustment method for a dynamic compressor.

  A reciprocating compressor capable of responding to fluctuations in the amount of generated BOG is generally used as a compressor used to compress BOG (boil-off gas) accompanying evaporation of LNG (liquefied natural gas). An outline of a reciprocating compressor and a capacity adjustment method will be described with reference to FIGS. FIG. 5 is a schematic view for explaining an opposed balanced two-stage compressor which is a kind of reciprocating compressor, and FIG. 6 is a partial detailed cross-sectional view showing details of a Y portion in FIG. This counter-balanced two-stage compressor includes a crank mechanism 20 that converts a rotational motion by the drive motor M into a reciprocating motion, and first-stage reciprocating compressors 21A and 21B that are coupled to the crank mechanism 20 and compress gas. It is comprised by 2nd-stage reciprocating compressor 22A, 22B.

  Then, the pistons of the two pairs of reciprocating compressors 21A, 22A and 21B, 22B are driven to oppose each other by the crank mechanism 20, and the gas compressed by the pistons 23 of the first stage compressors 21A, 21B, Furthermore, it is configured to obtain a high pressure by being compressed by the piston 23 of the second stage compressor 22A, 22B. Such a multistage reciprocating compressor has a pressure of about 1 MPa to 1.5 MPa in the case of a two-stage compressor as shown in FIG. 5 and a high-pressure compressed gas of about 2 to 4 MPa in the case of a three-stage compressor. can get.

  Each of the cylinders 24a, 24b and 25a, 25b of the two-stage reciprocating compressor according to the conventional example has two gas compression chambers (hereinafter also referred to as compression chambers), that is, a gas compression chamber on the head end side. The gas compression chamber CE on the HE and crank end side is provided, and loading / unloading of each compression chamber HE, CE is switched by opening / closing of a suction valve unloader 27 provided in each compression chamber HE, CE. The

  As shown in FIG. 6, the suction valve unloader 27 drives the spider 32 by an actuator 31 using air pressure, the tip of a finger 32a attached to the spider 32 advances, and pushes and restrains the valve plate 27a. The suction side space 100 and the gas compression chamber communicate with each other to unload the compression chamber HE and / or CE (either HE or CE, or both). On the other hand, the finger 32a moves backward, and the valve plate 27a opens and closes by a differential pressure between the front and rear (a differential pressure between the suction side space 100 and the gas compression chamber), thereby causing the compression chamber HE and / or CE (HE , CE, or both) is loaded.

  Further, a clearance pocket 28 is provided in the head of each compression chamber HE as shown in FIG. 5, and the clearance pocket 28 is opened and closed by a plug 29 a connected to the piston 30 of the head end unloader 29. The capacity of the compression chamber HE is adjusted by increasing / decreasing the compression volume of the chamber HE.

  Next, the operation method of the two-stage reciprocating compressor according to the conventional example will be described with reference to FIGS. FIG. 7 is a schematic diagram for explaining an operation method of a two-stage reciprocating compressor according to a conventional example. FIG. 7 (a) is at 0% load, FIG. 7 (b) is at 25% load, and FIG. Shows a state at 50% load, FIG. 4D shows a state at 75% load, and FIG. Table 1 shows the states of the suction valve unloader and the head end unloader of the compression chambers HE and CE in each load operation.

  That is, at 75% load, the 21A and 22A cylinders can be 100% load, the 21B and 22B cylinders can be 50% load (and vice versa), and the clearance pocket 28 can be used. On the other hand, when the load is 25%, the plug 29a of the head end unloader 29 is opened to load the clearance pocket 38 as well. Therefore, the head end unloader is indispensable during the 25% load operation of the two-stage reciprocating compressor according to the conventional example. However, since it is structurally attached to the tip of the cylinder, it is desirable that the head end unloader is not present from the viewpoint of vibration or the like.

  Further, the movement amount L1 of the head end unloader 29 when the plug 29a is opened / closed is about 50 mm, whereas the pressing amount L2 of the valve plate 27a of the suction valve unloader 27 is at most several mm, so when the load is switched. When the suction valve unloader 27 and the head end unloader 29 are operated simultaneously, a difference occurs in the switching timing.

  For example, when switching from 0% load (unload) to 50% load, switching from CE load to HE load by the suction valve unloader 27 of the cylinders 22A, 22B and clearance pocket 28 by opening the plug 29a of the head end unloader 29 are performed. When switching between two types of unloaders such as switching to a load, there is a difference in load switching between the cylinders 21A and 21B and the cylinders 22A and 22B due to the difference in time required for the switching.

On the other hand, as a method for adjusting the capacity of a reciprocating compressor according to another conventional example, a pole switching induction motor having two or more independent windings is used for an electric motor that drives the reciprocating compressor, and a high-speed rotation is performed. The high-speed output torque by the winding for the winding is set to be at least partially larger than the low-speed output torque by the low-speed winding that rotates at a low speed, and the torque difference when switching the number of poles is larger than the load torque. Energize the low-speed winding to accelerate until the difference in low-speed output torque is greater than the load torque, then energize the high-speed winding while energizing the low-speed winding. In some cases, the number of poles is switched by turning off the energization (see Patent Document 1).
Japanese Patent No. 3801702

  However, in the capacity adjustment method by switching the number of poles, it is necessary to energize the motor with overcurrent due to overlapping energization, so this overlapping energization time is limited, and due to malfunctions or operational errors, etc. In such a case, there is a problem that the electric motor is damaged such as seizure.

  Therefore, an object of the present invention is to realize stepwise capacity adjustment from 0% to 100% without a head end unloader, for example, 25% load and the like, and to produce a difference in switching timing at load switching. Another object of the present invention is to provide a capacity adjustment method for a reciprocating compressor capable of switching loads without load.

In order to achieve the above object, the means adopted by the capacity adjustment method of the reciprocating compressor according to claim 1 of the present invention includes a plurality of reciprocating compressors, and each of the plurality of reciprocating compressors includes Each cylinder is provided with two cylinders, each cylinder having two compression chambers separated by a piston accommodated in each cylinder, and each compression chamber is loaded / unloaded for each compression chamber. In the capacity adjustment method for a reciprocating compressor having a suction valve unloader capable of switching between, the plurality of reciprocating compressors are accommodated in at least a piston accommodated in a low-stage cylinder and a high-stage cylinder. a piston be one that is constituted by connecting in a crank mechanism, according to a preset time, the low-stage cylinder and the high-stage compressor of each in the load state in the cylinder of, one header End side of the compression chamber, so that the other is the compression chamber of the crank end side, switches the load state and the unloaded state of the compression chambers, the low-stage compression chamber of the compression chamber head end side is a load condition of the cylinder The compression chamber that is in a loaded state of the high-stage cylinder is a compression chamber on the crank end side .

  The means adopted by the capacity adjustment method of the reciprocating compressor according to claim 2 of the present invention is the capacity adjustment method of the reciprocating compressor according to claim 1, wherein the time is a fixed time interval. To do.

  The capacity of the reciprocating compressor capacity adjusting method according to claim 3 of the present invention is the capacity adjusting method of the reciprocating compressor according to claim 1 or 2, wherein the suction valve provided in each of the compression chambers. The unloader is actuated by actuators using pneumatic pressure, and a part of the solenoid valves for controlling the opening and closing of the air supply to these actuators is connected to the series, and these solenoid valves are opened and closed by the time signal. To do.

According to the capacity adjustment method of the reciprocating compressor according to claim 1 of the present invention, the stepwise capacity (load) from 0% to 100%, for example, 100%, 75%, 50%, 25% , 0% adjustment of each load can be realized without a head end unloader and clearance pocket. Furthermore, it is possible to reduce torque fluctuations associated with the rotation of the crank mechanism, and it is possible to reduce the load on shaft sealing means such as rod packing provided on the piston.

  According to the capacity adjustment method for a reciprocating compressor according to claim 2 of the present invention, the cylinder overheating at 0% load (no load) is achieved by setting the load switching interval of each compression chamber to an appropriate time. It is possible to prevent damage to the ring material due to

Furthermore, according to the capacity adjustment method for a reciprocating compressor according to claim 3 of the present invention, the number of pressure detectors for detecting 0% load can be reduced to two .

  First, the configuration of a reciprocating compressor according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a system diagram for explaining the configuration of a two-stage reciprocating compressor according to Embodiment 1 of the present invention. The two-stage reciprocating compressor according to the first embodiment of the present invention includes a crank mechanism 4 that converts rotational motion by the drive motor M into reciprocating motion, and a first-stage reciprocating motion that is coupled to the crank mechanism 4 and compresses gas. It is comprised by dynamic compressor 1A, 1B and 2nd-stage reciprocating compressor 2A, 2B. The first-stage reciprocating compressors 1A and 1B are respectively provided with cylinders 5a and 5b, and the second-stage reciprocating compressors 2A and 2B are respectively provided with cylinders 6a and 6b. It can be said that two cylinders are provided for each stage.

  Then, the pistons of the two pairs of reciprocating compressors 1A, 2A and 1B, 2B facing each other by the crank mechanism 4 are driven to face each other, and the gas compressed by the pistons 3 of the first stage compressors 1A, 1B is driven. Further, the compressor is configured to be compressed by the piston 3 of the second stage compressors 2A and 2B to obtain high-pressure compressed air. Each cylinder 5a, 5b and 6a, 6b of such a two-stage reciprocating compressor has two gas compression chambers, that is, a gas compression chamber HE on the head end side and a gas compression chamber CE on the connecting rod end side. is doing.

  Accordingly, each of the cylinders 5a, 5b, 6a, 6b has two compression chambers separated by the piston 3 accommodated for each cylinder. The multistage (second stage) reciprocating compressor is housed in the piston 3 housed in the lower (first stage) cylinders 5a and 5b and in the higher stage (second stage) cylinders 6a and 6b. It can be said that the piston 3 is connected by a crank mechanism 4. The loading / unloading of the compression chambers HE, CE is switched by opening / closing the suction valve unloader 7 provided in each of the compression chambers HE, CE.

  The suction valve unloader 7 drives the spider 32 by an actuator 31 using air pressure, and the finger 32a attached to the spider 32 moves forward in the same manner as the conventional suction valve unloader shown in FIG. The compression chamber HE is unloaded by pushing and restraining the plate 27a and communicating with the suction side, and the valve plate 27a is opened and closed by a differential pressure between the front and rear by the retraction of the finger 32a, thereby loading the compression chamber HE. It is configured to make it.

  The reciprocating compressor according to the first embodiment of the present invention is configured to load / unload the suction valve unloader 7 according to a time signal set in the controller 8 in advance, that is, according to a preset time. The compression chambers HE and CE can be switched between a loaded state and an unloaded state. In other words, each actuator that drives the suction valve unloader 7 from a compressed air source is connected by a compressed air pipe 10 in which electromagnetic valves 9a, 9b, 9c, 9d are interposed, and these electromagnetic valves 9a, 9b, 9c, 9d. 9a, 9b, 9c are connected in series (series), and the remaining solenoid valve 9d is connected to the compressed air pipe 10 independently.

  The suction valve unloaders 73a and 74a are opened and closed by opening and closing the solenoid valve 9a, the suction valve unloaders 71b and 72b are opened and closed by opening and closing the solenoid valve 9c, and the suction valve unloaders 71a and 72a are opened and closed. The suction valve unloaders 73b and 73b can be switched between loading and unloading by opening and closing the electromagnetic valve 9d.

  These solenoid valves 9a, 9b, 9c, 9d are opened and closed according to a preset time signal command in the controller 8, that is, according to a preset time, and the solenoid valves 9a, 9b, 9c, 9d The actuators respectively connected to the wakes are operated to switch loading / unloading of the suction valve unloader corresponding to any one of the suction valve unloaders 71a to 74a and 71b to 74b.

  That is, when one of the solenoid valves 9a to 9d is opened and pressurized air is supplied to the suction valve unloader 7, the valve plate is pushed in by the corresponding actuator so that the compression chamber HE or / and CE is on the suction side. Conversely, when any of the solenoid valves is closed and the compressed air is shut off in an unloaded state communicating with the system, the valve plate is unconstrained by the corresponding actuator, and the valve is opened and closed with a differential pressure before and after, The compression chamber HE or / and CE is loaded.

  By connecting 9a, 9b, and 9c of the solenoid valves in series (in series), the number of pressure detectors 11 for determining 0% load can be reduced to two. The reason why only the solenoid valve 9d is connected and connected is that it is preferable to alternately switch the solenoid valves 9c and 9d at 25% load as will be described later.

  Next, an operation method of such a two-stage reciprocating compressor according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 2 is a schematic diagram for explaining a load operation method of the reciprocating compressor according to Embodiment 1 of the present invention. FIG. 2 (a) is at 0% load, FIG. 2 (b) is at 25% load, Fig. (C) shows the state at 50% load, Fig. (D) shows the state at 75% load, and Fig. (E) shows the state at 100% load. FIG. 3 is a schematic diagram for explaining another operation method at 25% load in FIG. Table 2 shows the load state of each cylinder in the operation method of the two-stage reciprocating compressor according to the embodiment of the present invention.

  In the operation method of the two-stage reciprocating compressor according to Embodiment 1 of the present invention, the operation can be performed by increasing the compression chamber by one for each stage where the load increases by 25% from the 0% load operation. It becomes possible. That is, at the time of 25% load operation, the opposing reciprocating compressors 1A and 2A operate without load, while in the other opposing reciprocating compressors 1B and 2B, the compression chamber HE of the cylinder of the reciprocating compressor 1B. In addition, by performing load operation only on the compression chamber CE of the cylinder of the reciprocating compressor 2B, one of the four compression chambers is loaded on each stage, and (1/4) × 100 = 25%. Road operation can be realized.

  However, as described above, if only the opposed reciprocating compressors 1A and 2A are continuously operated for a long time, the ring material is damaged due to overheating of the cylinders of the reciprocating compressors 1A and 2A. Such a 25% load operation is performed only in the compression chamber HE of the cylinder of the reciprocating compressor 1A and the compression chamber CE of the cylinder of the reciprocating compressor 2A instead of the reciprocating compressors 1B and 2B, as shown in FIG. This can also be achieved by load operation or other methods in which one of the four compression chambers of the cylinder of each stage is loaded. Therefore, loading / unloading of the compression chambers of the cylinders of the reciprocating compressors 1A, 2A and 1B, 2B is switched at a preset time in the controller 8, that is, at intervals of about 5 to 10 minutes. Is preferred.

  Further, at the time of 50% load operation, the compression chamber HE of the cylinder of the low stage (first stage) reciprocating compressor 1A, 1B and the cylinder of the high stage (second stage) reciprocating compressor 2A, 2B On the other hand, in the 75% load operation, the reciprocating compressors 1A and 2A are 100% loaded, and the compression chamber HE of the cylinder of the reciprocating compressor 1B and the reciprocating compressor 2B are realized. This can be realized by performing a load operation only on the compression chamber CE of the cylinder.

  Note that the 50% load operation is performed between the compression chamber CE of the cylinders of the low-stage (first stage) reciprocating compressors 1A and 1B and the cylinders of the high-stage (second stage) reciprocating compressors 2A and 2B. It is also possible to perform a load operation on any one of the two compression chambers of each cylinder, such as a load operation with the compression chamber HE. The 75% load operation is also performed by the reciprocating compressor 1A. Only the compression chamber HE of the cylinder and the compression chamber CE of the cylinder of the reciprocating compressor 2A are loaded and the cylinders 1B and 2B of the opposing reciprocating compressor are 100% loaded, etc. This can be realized by load-operating any three of the four chambers.

  By the way, in the example shown in FIG. 7 as the prior art, when switching from 0% load to 50% load is attempted, the compression chamber CE of the cylinder of the high stage (second stage) reciprocating compressor 2A, 2B. Can be immediately loaded, but the compression chamber HE of the cylinders of the low-stage (first stage) reciprocating compressors 1A and 1B pushes the head unloader and requires a predetermined time to enter the loaded state. In addition, a “shift” of switching to the load state occurs between the high-stage cylinder and the low-stage cylinder.

  This “shift” in switching to the load state means that the state where the balance of the intermediate pressure is lost continues for a predetermined time. However, in the present invention, since the head unloader is not provided in the first place, there is an advantage that the “shift” to the load state as described above and the state in which the balance of the intermediate pressure is not lost are not generated.

  In the pair of opposed cylinders, the piston is pushed out at the same timing, and the force exerted on the crank mechanism is the sum of the reaction forces of the pistons of the opposed cylinder. Therefore, as described above, one of the compression chambers in the loaded state in the cylinder of the reciprocating compressor on the lower stage side and the cylinder of the reciprocating compressor on the higher stage side is the compression chamber HE on the head end side, and the other By switching the loading state / unloading state of each compression chamber so that the compression chamber CE becomes the crank end side, the phase of the reaction force of the piston of the opposing cylinder is shifted (by 180 degrees). The total value of the reaction force is not excessive.

  As a result, it is possible to reduce torque fluctuations accompanying the rotation of the crank mechanism, and hence the load on the drive motor. Furthermore, the compression chamber in the loaded state of the cylinder of the low-stage reciprocating compressor is referred to as a compression chamber HE on the head end side, and the compression chamber in the loaded state of the cylinder of the high-stage reciprocating compressor is cranked. By adopting the compression chamber CE on the end side, it is possible to reduce the load applied to the shaft sealing means such as the rod packing provided at the portion where the piston rod penetrates the compression chamber CE. Has been found.

  Next, a capacity adjustment method for a reciprocating compressor according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 4 is a partial detailed cross-sectional view showing details of a portion X in FIG. 1 according to the second embodiment of the present invention. However, the difference between the second embodiment of the present invention and the first embodiment is that the suction valve unloader is different in configuration, and the other configuration is exactly the same as in the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and different points will be described below.

  That is, when the solenoid valve is opened and the compressed air is supplied to the suction valve unloader of the first embodiment, the corresponding actuator moves forward, the valve plate is pushed in, and the compression chamber communicates with the system on the suction side. On the other hand, when the solenoid valve is closed and the compressed air is shut off, the corresponding actuator is retracted, and the valve plate is opened / closed by the differential pressure between the front and rear, that is, the load state.

  On the other hand, in the suction valve unloader 7 (74a) of the second embodiment, when the electromagnetic valve 9a is opened and the compressed air is supplied to the corresponding actuator 13, the piston 13a is pushed back to the actuator 13 side, and the spider 12 When the tip of the finger 12a is separated from the valve plate 14 and is opened / closed by a differential pressure across the valve plate 14, that is, in a load state, conversely, when the electromagnetic valve is closed and the compressed air is shut off from the corresponding actuator 13, the actuator The piston 13a is pushed into the compression chamber HE side by the spring 13b housed in the valve 13, the valve plate 14 is closed, and the compression chamber HE is in an unloaded state communicating with the suction side system.

  As described above, according to the capacity adjustment method for a reciprocating compressor according to the present invention, the reciprocating compressor of a plurality of stages is provided, and the reciprocating compressor of the plurality of stages includes two cylinders at each stage, The cylinder includes two compression chambers separated by a piston accommodated in each cylinder, and each of the compression chambers includes a suction valve unloader capable of switching between a load state and an unload state for each compression chamber. In the method of adjusting the capacity of the dynamic compressor, the load state / unload state of the compression chamber is switched according to a preset time, so the capacity (load) from 0% to 100%, specifically 100%, 75% , 50%, 25%, and 0% of load can be adjusted without a head end unloader and clearance pocket.

  According to the capacity adjustment method for a reciprocating compressor according to the present invention, the time is assumed to be a constant time interval, and the constant time interval, that is, the load switching interval of each compression chamber is set to an appropriate time. Thus, it is possible to prevent damage to the ring material due to cylinder overheating at 0% load.

It is a systematic diagram for demonstrating the structure of the two-stage reciprocating compressor which concerns on Embodiment 1 of this invention. It is a schematic diagram for demonstrating the load driving | running method of the two-stage reciprocating compressor which concerns on Embodiment 1 of this invention, a figure (a) at the time of 0% load, a figure (b) at the time of 25% load, (C) shows a state at 50% load, FIG. (D) shows a state at 75% load, and (e) shows a state at 100% load. It is a schematic diagram for demonstrating the other driving | running method of 25% load driving | operation in FIG.2 (b). FIG. 4 is a partial detailed cross-sectional view illustrating details of a portion X in FIG. 1 according to the second embodiment of the present invention. It is a schematic diagram for demonstrating the counter balance type | mold 2 stage compressor which is a kind of reciprocating compressor which concerns on a prior art example. It is a fragmentary detailed sectional view which shows the Y section detail of FIG. It is a schematic diagram for demonstrating the operating method of the two-stage reciprocating compressor which concerns on a prior art example, a figure (a) at the time of 0% load, the figure (b) at the time of 25% load, and the figure (c) at 50%. At the time of loading, FIG. (D) shows the state at 75% load, and FIG. (E) shows the state at 100% load.

Explanation of symbols

HE: Gas compression chamber on the head end side,
CE: Gas compression chamber on the connecting rod end side,
M: drive motor,
1A, 1B: first stage reciprocating compressor (first stage compressor),
2A, 2B: Second stage reciprocating compressor (second stage compressor),
3: piston, 4: crank mechanism,
5a, 5b, 6a, 6b: cylinder,
7, 71a-74a, 71b-74b: Suction valve unloader,
8: Controller,
9a to 9d: solenoid valves,
10: compressed air piping, 11: pressure detector,
12: Spider, 12a: Finger,
13: Actuator, 13a: Piston, 13b: Spring,
14: Valve plate

Claims (3)

Equipped with a multistage reciprocating compressor,
The multi-stage reciprocating compressor includes two cylinders for each stage,
Each cylinder includes two compression chambers separated by a piston accommodated in each cylinder,
In each compression chamber, the capacity adjustment method for a reciprocating compressor provided with a suction valve unloader capable of switching between loading and unloading for each compression chamber,
The multi-stage reciprocating compressor is configured by connecting at least a piston housed in a low-stage cylinder and a piston housed in a high-stage cylinder by a crank mechanism,
According to a preset time , each of the compressors in the loaded state in the low-stage cylinder and the high-stage cylinder is such that one is a compression chamber on the head end side and the other is a compression chamber on the crank end side. Switch the loading / unloading status of each compression chamber ,
The reciprocating compression is characterized in that the compression chamber in the loaded state of the lower stage cylinder is a compression chamber on the head end side, and the compression chamber in the loaded state of the higher stage cylinder is a compression chamber on the crank end side. How to adjust the capacity of the machine.   The capacity adjustment method for a reciprocating compressor according to claim 1, wherein the time is a constant time interval.   A suction valve unloader provided in each of the compression chambers is operated by an actuator using air pressure, and a part of an electromagnetic valve for controlling opening and closing of air supply to these actuators is connected to a series, and these are also indicated by the time signal. 3. The capacity adjustment method for a reciprocating compressor according to claim 1, wherein the electromagnetic valve is opened and closed.

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