Reciprocating compressor with gas recirculation from leak to aspiration and method for operating said compressor

Abstract

The invention discloses a compressor (1) comprising at least a gas leak recirculation duct (R1) connected between the packing (9) and the aspiration of the compressor (17), preferably several ducts (R2, R3, R4) recirculation the leaks from the several compartments (81, 82, 83) of the compressor (1) towards the aspiration (17) of the compressor (1). Thus, possible gas leaks in the compressor (1) are sent to the admission. Further, this compressor (1) comprises a crankcase (7) lubrication system through which an ionic liquid (LI) flows instead of oil (A), and the crankcase (7) is maintained pressurized, that is, essentially airtight.

Description

Object of the invention

[0001] The present invention belongs to the field of gas compression systems.

[0002] A first aspect of the present invention is directed to a new compressor having means for recirculating leaked gases towards the aspiration of the compressor, that maintains the crankcase pressurized and also carries out the lubrication using ionic liquids.

[0003] A second aspect of the present invention is directed to a method for operating the abovementioned compressor.State of the art

[0004] A reciprocating compressor is a positive displacement equipment where the compression is achieved by means of the displacement of a piston moving linearly to and fro inside a cylinder. This process alternatively reduces the volume of one or the other side of the chamber, which is the place where the gas is placed, thereby increasing the pressure until achieving the discharge pressure. The piston is actuated by means of a crankshaft moved by an axle normally connected to an actuation motor.

[0005] Fig. 1 shows a schematic longitudinal cross-section of a double-effect reciprocating compressor (CR). This compressor has a casing formed by several parts connected ones to the others inside which a rod (V) moves longitudinally according to a reciprocating motion. The right end of the rod (V) according to the orientation of the figure is coupled to a piston (P), while the left end of the rod (V) according to the figure is connected, through a connecting rod (B), to a crankshaft (CG) housed within the crankcase (C). The right end of the connecting rod (B) is connected to a guide (G) which, in turn, is connected to the end of the rod (V). Although not shown in this figure, a motor rotates the crankshaft (CG) to cause the reciprocating motion of the rod (V), which is transmitted to the piston (P), that moves along the interior of the cylinder (CI). The crankcase (C) housing the mechanism formed mainly by the connecting rod (B) and the crankshaft (CG) is partially filled with oil (A) to ensure the lubrication of these elements. This oil (A) enters the crankcase through one or more inlet ducts to ensure lubrication of all parts, and is extracted through one or more outlet ducts only to be recirculated again towards the inlet by means of a pump or the like.

[0006] The cylinder (CI) has two pairs of inlet / outlet ports provided respectively adjacent each of its ends. That is, at the left side of the cylinder (CI) there is a first inlet port (PE1) and a first outlet port (PS1), while at the right side of the cylinder (CI) there is a second inlet port (PE2) and a second outlet port (PS2). During the displacement, the piston (P) alternatively compresses the gas at one or the other side of the cylinder (CI), and a suitable coordination of the opening and closing moments of the inlet (PE1, PE2) and outlet (PS1, PS2) ports allows for the aspiration and discharge phases to take place. The inlet ports (PE1, PE2) are in communication with an admission duct (AD) connected to the gas source, and the outlet ports (PS1, PS2) are connected to an outlet duct (SA) through which the compress fluid exits.

[0007] In this context, it is known that gas leaks from the cylinder (CI) through the several joints and connection of the compressor (CR) take place. The leaks are particularly important when the gas is hydrogen, since hydrogen has a low viscosity and molecular weight that make it particularly prone to leaks.

[0008] The main point where the leaks of a reciprocating compressor (CR) take place is the packing (E). The packing (E) is the sealing provided between the rod (V) and the end wall of the cylinder (CI), that is, the wall of the cylinder (CI) through which the rod (V) enters said cylinder (CI). The packing (E) is formed normally by a plurality of sealing units provided one after the other in the longitudinal direction. After passing through the packing (E), the leaked gas may pass through the inner cavities (CA1, CA2, CA3) and reach the crankcase (C).

[0009] Nowadays, it is generally accepted that the packing (E) cannot achieve a completely airtight sealing, such that all compressors (CR) of this type have, to a greater or lesser extent, gas leaks. These leaks eventually reach the crankcase (C), which is accordingly provided with outlets to evacuate this gas.

[0010] In conclusion, there still exists in this field the need for a solution to this problem.Brief disclosure of the invention

[0011] The inventors of the present invention have solved the above-mentioned drawbacks by means of a compressor that captures possible gas leaks through the packing to send them to the admission. Furthermore, according to the invention the oil in the crankcase is replaced by an ionic liquid, thereby preventing the gas from being contaminated with the oil.

[0012] Now, the object of the invention is disclosed in greater detail.First aspect: compressor

[0013] The first aspect of the present invention is directed to a compressor, normally a reciprocating compressor. Note that the present invention is equally applicable to a simple-effect and to a double-effect reciprocating compressor.

[0014] The compressor comprises a casing along which a rod moves. One end of the rod is connected to a piston and an opposite end of the rod is joined to a connecting rod connected to a crankshaft. The casing comprises at a first end a cylinder within which the piston moves and, in a second end opposite the first, a crankcase housing the connecting rod and the crankcase. The casing further comprises at least an intermediate cavity between the cylinder and the crankcase, where said at least one intermediate cavity is separated from the cylinder by means of a packing.

[0015] Until this point, the general configuration of a conventional reciprocating compressor is disclosed. The compressor of the invention, however, differs from said conventional compressor by comprising at least a first duct for recirculating gas leaks connected between the packing and a compressor gas aspiration container. This first duct sends to the aspiration of the compressor possible gas leaks taking place through the packing.

[0016] The compressor of the invention may further comprise additional recirculation ducts to extract gas leaks from other cavities of the compressor. For example, according to a preferred embodiment, the compressor further comprises at least a second additional gas leak recirculation duct connected between a cavity of the casing and the compressor gas aspiration container. In another preferred embodiment, the compressor may comprise another additional gas leak recirculation duct connected between the crankcase and the compressor gas aspiration container.

[0017] Furthermore, the compressor of the invention comprises a crankcase lubrication system through which an ionic liquid flows instead of oil. Since oil is dispensed with for lubrication, the recirculated gas passing through the compressor and crankcase is prevented from being contaminated with oil particles. The ionic liquid does not interact with the gas, and therefore the properties of the compressed fluid remain intact. The passing of the gas through the airtight crankcase will cause a pressure increase for which the crankcase is structurally dimensioned.

[0018] In principle, the ionic liquid can be recirculated through the crankcase provided a suitable lubrication of the components housed within the crankcase is ensured. For example, in a preferred embodiment of the invention, the crankcase lubrication system by an ionic liquid comprises a pump whose pressure port is connected to an inlet duct connected to the crankcase and whose suction port is connected to an outlet port connected to the bottom of the crankcase. For example, the same ducts conventionally used for lubrication with oil can be employed.

[0019] More preferably, the crankcase lubrication system further comprises a separator configured to separate the ionic liquid from possible gas rests present in the crankcase. This separation is carried out only when necessary, since in most cases the ionic liquid and the gas will be immiscible.Second aspect: method for operating the compressor

[0020] The second aspect of the present invention is directed to a method for operating a compressor as the one disclosed above.

[0021] This method mainly comprises the following steps: 1. Recirculating gas leaks through the packing towards the compressor aspiration container by means of a first recirculation duct. The first recirculation duct can connect an inner area of the packing with the compressor aspiration container through which the gas is introduced in the cylinder to be compressed. 2. Maintaining the crankcase pressurized. 3. Lubricating the crankcase using an ionic liquid instead of oil.

[0022] The method of the invention may further comprise the recirculation of leaks taking place at other locations of the compressor, such as for example the cavities of the casing and the crankcase. Thus, in a particularly preferred embodiment the method further comprises the step of recirculating gas leaks from a cavity of the casing towards the compressor aspiration container by means of at least a second recirculation duct. In another preferred embodiment, the method further comprises recirculating gas leaks from the crankcase towards the compressor aspiration container by means of yet another recirculation duct.

[0023] Preferably, the step of lubricating the crankcase comprises pumping ionic liquid through the inlet duct connected to the crankcase and aspirating said ionic liquid through the outlet duct connected to the bottom of the crankcase.

[0024] Although, in principle, in may cases the ionic liquid and the gas are immiscible, when needed the method preferably further comprises separating the ionic liquid from the recirculated gas.Brief disclosure of the figures

[0025] The details of the invention are shown in the accompanying figures, which are not intended to limit the scope of the invention: Fig. 1 shows a schematic longitudinal section view of a conventional compressor. Fig. 2 shows a schematic longitudinal section view of a compressor according to the present invention. Descripción detallada de la invención

[0026] An example of the present invention is disclosed now with specific reference to Fig. 2, which shows a double-effect compressor (1). In any case, as mentioned earlier, the invention would be equally applicable to a simple-effect compressor. Further, in this example the gas is specifically hydrogen, although the invention is applicable to any other gas.

[0027] As shown, the compressor (1) comprises an external housing or casing along whose interior a rod (2) follows an alternative motion. According to the position of the figure, the rod (2) has a right end connected to a piston (3), and a left end connected to a guide (12) moving along a cylindrical cavity (83). The guide (12), in turn, is connected to a connecting rod (4) joined to a crankshaft (5). Although not shown in the figure, the crankshaft (5) is moved by a combustion engine or the like, and the disclosed mechanism causes the rod (2), and therefore also the piston (3), to move according to an alternative or reciprocating motion. The piston (3) is housed inside a chamber or cylinder (6), and upon moving alternatively though it compresses, also in an alternative manner, the hydrogen present at one or the other side of the cylinder (3). This hydrogen is introduced in a coordinated manner through two inlet ports (13, 14) provided at opposite sides of the cylinder (3), and it is extracted also in a coordinated manner through two outlet ports (15, 16) also provided at opposite sides of the cylinder (3) and in diametrically opposite positions with respect to the inlet ports (13, 14). The hydrogen is supplied to the inlet ports (13, 14) through an aspiration container (17), and it is extracted from the outlet ports (15, 16) through an outlet duct (18).

[0028] The casing is formed by a plurality of parts connected ones to the others; inside these parts there are walls separating a number of cavities. From right to left, the cavities of this casing are the following: first there is the cylinder (6), through which interior the piston (3) moves; then, separated from the cylinder (6) by the wall making up the base of said cylinder (6) and the packing (9), there is a first cavity (81); then, separated from the first cavity (81) by another wall, there is a second cavity (82) similar to the previous one; next, also separated from the second cavity (82) by another wall, there is a third cavity (83), which is the cavity along which the guide (12) slides; and finally, separated from the third cavity (83) by the guide (12) itself, the crankcase (7) is provided.

[0029] According to the present invention, a hydrogen leak recuperation system is provided that passes through the packing (9). As shown, this system is mainly formed by a first recirculation duct (R1) connecting the packing (9) with the aspiration container (17) of the compressor (1). Thus, any gas passing through the packing (9) is suctioned by the sub-pressure present in the aspiration container (17) of the compressor (1), thereby returning to the cylinder (6) to be compressed.

[0030] In this example, the compressor (1) also has several additional recirculation ducts (R2, R3, R4) that recover gas leaked to other cavities (82, 83, 84) of the casing. In the specific case illustrated herein, a second recirculation duct (R2) connects the cavity (82) with the aspiration container (17) of the compressor (1), a third recirculation duct (R3) connects the cavity (83) with the aspiration container (17) of the compressor (1), and a fourth recirculation duct (R4) connects the crankcase (7) with the aspiration container (17) of the compressor (1). This system allows for recovering all of the possible gas leaks.

[0031] In combination with the above, in the compressor (1) of the invention the oil (A) usually used to lubricate the crankcase (7) is replaced by an ionic liquid (LI). Thereto, an ionic liquid (LI) inlet duct (10) to the crankcase (7) is provided. This inlet duct (10) may divide in a number of inner ducts directed to those parts of the mechanism that need lubrication. The ionic liquid (10) emitted or sprayed lubricates the mechanical connections, for example, between the crankshaft (5) and the connecting rod (4) and accumulates at the bottom of the crankcase (7). From the bottom of the carter (7) emerges an outlet duct (11) to recover that accumulated ionic liquid (LI) and to recirculate it. Although not shown in the figure, a pump receives the ionic liquid (LI) extracted through the outlet duct (11) and pushes it towards the inlet duct (10). Other necessary elements may be provided in this recirculation system, such as e.g. a separator, a cooler, a filter, or the like.

[0032] Additionally, since the lubricant fluid is now an ionic liquid (LI) instead of oil, risk of contamination of the process gas is eliminated. The gas, processed, recirculated and compressed, will maintain its properties intact after passing through the compressor (1), since the ionic liquid (LI) is immiscible with the gas. The crankcase (7), in addition, is completely airtight.

Claims

1. Reciprocating compressor (1) with gas recirculation from leak to aspiration, comprising a casing along which a rod (2) moves, where an end of the rod (2) is connected to a piston (3) and an opposite end of the rod (2) is joined to a connecting rod (4) connected to a crankshaft (5), where the casing comprises at a first end a cylinder (6) along whose interior the piston (3) moves and at a second end opposite the first a crankcase (7) housing the connecting rod (4) and the crankshaft (5), the casing further comprising at least an intermediate cavity (81, 82, 83) between the cylinder (6) and the crankcase (7), where said intermediate cavity (81) is separated from the cylinder (6) by a packing (9), characterized by comprising at least a first gas leak recirculation duct (R1) connected between the packing (9) and an aspiration container (17) of the compressor (1), to send to the aspiration of the compressor possible gas leaks through the packing (9); and further by comprising a crankcase (7) lubrication system through which an ionic liquid (LI) flows instead of oil (A), where the crankcase (7) is pressurized.

2. Compressor (1) according to claim 1, further comprising at least a second gas leak additional recirculation duct (R2, R3) connected between a cavity (81, 82) of the casing and the aspiration container (17) of the compressor (1).

3. Compressor (1) according to any of the previous claims, further comprising a fourth gas leak additional recirculation duct (R4) connected between the crankcase (7) and the aspiration container (17) of the compressor (1).

4. Compressor (1) according to any of the previous claims, where the crankcase (7) lubrication system by means of an ionic liquid (LI) comprises a pump whose pressure port is connected to an inlet duct (10) connected to the crankcase (7), and whose suction port is connected to an outlet duct (11) connected to a bottom of the crankcase (7).

5. Compressor (1) according to claim 4, where the crankcase 87) lubrication system further comprises a separator configured to separate the ionic liquid (LI) from possible gas rest that may have entered the crankcase (7).

6. Method for lubricating the compressor according to any of the previous claims with an ionic liquid, characterized by comprising: - recirculating gas leaks through the packing (9) towards the aspiration container (17) of the compressor by means of a first recirculation duct (R1); - maintaining the crankcase (7) pressurized; and - lubricating the crankcase (7) using an ionic liquid (LI) instead of oil (A).

7. Method according to claim 6, further comprising recirculating gas leaks from a cavity (82, 83) of the casing towards the aspiration container (17) of the compressor (1) by means of at least a second recirculation duct (R2, R3).

8. Method according to any of claims 6-7, further comprising recirculating gas leaks from the crankcase (7) towards the aspiration container (17) of the compressor by means of a fourth recirculation duct (R4).

9. Method according to any of claims 6-8, where the step of lubricating the crankcase (7) comprises pumping an ionic liquid (LI) through the inlet duct (10) connected to the crankcase (7) and aspirating said ionic liquid (LI) through the outlet duct (11) connected to the bottom of the crankcase (7).

10. Method according to claim 9, further comprising separating the gas from the ionic liquid (LI) lubricating the crankcase (7).

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