Compressor packing sealed with ionic liquids and method for sealing a compressor packing with ionic liquids

Abstract

The invention discloses a compressor packing (1) comprising a fixation plate (2) fixed to a set of sealing units (3A-3F) making up a longitudinal piling, where each sealing unit (3A-3F) comprises a body (31) and, at least, a disc (32) housed in said body (31). The packing (1) is fixed to an end wall of the chamber (CA) of a compressor for separating said chamber (CA) from a longitudinally adjacent space (ES) of the compressor to prevent leaks. The packing (1) is particular in that it comprises an inlet duct (4) and an outlet duct (5) in communication with a cavity (61) of an additional sealing unit (6) for pumping an ionic liquid (LI) to said cavity (61). The ionic liquid (LI) of the cavity makes up a barrier against gas leaks.

Description

Object of the invention

[0001] The present invention belongs to the field of gas compression systems, and more particularly to hydrogen compressors.

[0002] A first aspect of the present invention is directed to a new compressor packing that is designed to allow for the circulation of an ionic liquid. The ionic liquid functions as a seal that prevent gas leaks through the packing.

[0003] A second aspect of the present invention is directed to a method for sealing a compressor packing using ionic liquids.State of the art

[0004] A reciprocating compressor is a positive displacement device wherein the compression is achieved by the displacement of a piston moving linearly in a reciprocating motion inside a cylinder. This process reduces the volume of the chamber, which is the place where the gas is introduced, thereby increasing the pressure up to the discharge pressure.

[0005] Fig. 1 shows a schematic longitudinal section of a reciprocating compressor (CR). As shown, this compressor has a casing (C) formed by several parts connected ones to the others within which a rod (V) moves longitudinally according to a reciprocating motion. At the right end of the rod (V) in the orientation of the figure there is a piston (P), while at the left end of the rod (V) according to the orientation of the figure there is a crankshaft housed within a crankcase (not shown in this figure).

[0006] The piston (P) is housed inside a chamber (CA) and moves within said chamber (CA) in a reciprocating motion. The camber (CA) has two pairs of inlet / outlet ports provided respectively adjacent each of its ends. That is, adjacent a left end of the chamber (CA) there is a first inlet port (PE1) and a firs outlet port (PS1), while at the right end of the chamber (CA) there is a second inlet port (PE2) and a second outlet port (PS2). During the displacement, the piston (P) alternatively compresses the gas of one or the other end of the chamber (CA). A suitable coordination of the opening and closing times of the inlet ports (PE1, PE2) and outlet ports (PS1, PS2) allows for the aspiration and discharge phases to take place.

[0007] In this context, it is known that, specially when the fluid to be compressed is hydrogen, gas leaks from the chamber (CA) appear through the numerous joints and connections of the compressor (CR). A reason is that hydrogen has a low viscosity and molecular weight, which makes it particularly prone to leaks. In any case, gas leaks are an important problem in this field.

[0008] The main place where the gas leaks of a reciprocating compressor (CR) take place is the packing (E). The packing (E), shown in greater deatail in Fig. 2, is the seal provided between the rod (V) and the end wall of the chamber (CA), that is, the wall of the chamber (CA) through which the rod (V) enters said chamber (CA). The packing (E) is normally formed by a number of sealing units (US) provided adjacent one after the other in the longitudinal direction. Each sealing unit (US) comprises a body (CU) housing a number of adjacent discs or rings (D). The sealing units (US) are piled against a fixation plate (PF) provided at an end opposite to the end where the wall of the chamber (CA) is provided, where this fixation plate (PF) may have an additional disc (D). Due to the pressure inside the chamber (CA), which is transmitted through the interstices of the joints, the discs (D) are compressed both against the body (CU) and ones against the others to render an airtight sealing.

[0009] It is currently 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.

[0010] Thus, there is still in this field a need for more airtight sealing systems allowing for the elimination of the gas leaks.Brief disclosure of the invention

[0011] The inventors of the present invention have solved the mentioned drawbacks by means of a new packing comprising a cavity through which an ionic liquid flows that is provided at the leak path of the gas. Due to its very particular physical-chemical characteristics, the ionic liquid is a barrier for the gas. The gas leaks through the compressor packing can therefore be reduced to almost imperceptible amounts. This solution is applicable to all types of compressors, whether of double or simple effect.First aspect: compressor packing

[0012] The first aspect of the present invention is directed to a compressor packing.

[0013] The packing of the invention comprises a fixation plate fixed to a number of sealing units provided ones against the others forming a longitudinal piling. In turn, each sealing unit comprises a body and, at least, one disc housed within said body. As is known, the packing is configured to be fixed by means of the fixation plate to the end wall of the chamber of a compressor for separating said chamber from a longitudinally adjacent space of the compressor with the purpose of preventing leaks.

[0014] Until now, the main components of a conventional packing have been disclosed. However, the packing of the present invention is different from the conventional packings because it additionally comprises an inlet duct and an outlet duct in communication with a cavity of an additional sealing unit. These ducts allow for the pumping of an ionic liquid to said cavity, the ionic liquid in the cavity functioning as a barrier against gas leaks.

[0015] In this context, it is understood that the additional sealing unit has a shape that fits between two conventional sealing units, thereby forming a compact assembly with the remaining elements of the packing. This additional sealing unit, however, instead of having a cavity to receive a conventional sealing disc, has a cylindrical cavity whose diameter is slightly greater than the diameter of the rod of the compressor. Thus, this cavity is passed through by the rod, creating a cylindrical space between the inner walls of the cavity and the outer walls of the rod. The ionic liquid passes through this space to make up a barrier preventing the gas from passing through.

[0016] In principle, the additional sealing unit may be provided at any position of the packing, although preferably it is provided between a first subset of sealing units and a second subset of sealing units. In this case, the inlet duct and the outlet duct pass through the fixation plate and also through the first subset of sealing units in the longitudinal direction until arriving at the additional sealing unit.

[0017] On the other hand, the inlet and outlet ducts may be provided at different angular positions of the packing, although they are preferably provided at diametrically opposing positions of said packing.

[0018] According to a particularly preferred embodiment of the invention, the packing specifically has the following configuration: The fixation plate comprises an inlet mouth followed by a first section of the inlet duct, and an outlet mouth followed by a first section of the outlet duct. That is, in this configuration, the inlet and outlet of the circulation duct of the ionic liquid are both provided at the fixation plate. The first subset of sealing units adjacent the fixation plate comprises respective intermediate sections respectively of the inlet duct and the outlet duct. The inlet and outlet ducts thereby extend from the respective first sections provided at the fixation plate along these sealing units, passing from one section to the other, in the direction of the additional sealing unit. The additional sealing unit comprises a last section of the inlet duct connecting the cavity with the section of the adjacent sealing unit and a last outlet section connecting the cavity with the section of said adjacent sealing unit.

[0019] Naturally, it is understood that all of the mentioned sections are aligned ones with the others along the path of the respective ducts in the longitudinal direction of the packing. Only the last sections of both ducts, that is, those provided at the additional sealing unit, do not have a longitudinal direction but a radial direction, or radial with a certain longitudinal inclination, to connect the radial position of the immediately adjacent section of both ducts with maximum radial dimension of the cavity.

[0020] In principle, the circulation of the ionic liquid can be carried out in any manner allowing for pumping it suitably through the mentioned circuit made by the cavity and the inlet and outlet ducts. For example, a pumping system provided at any suitable position can be employed.

[0021] In a particularly preferred embodiment, the invention is also directed to a compressor comprising a packing such as the one disclosed in the previous paragraphs and further comprising an ionic liquid pumping system connected between the inlet mouth and the outlet mouth of the fixation plate. This pumping system, for example, a pump having a suitable configuration, would have an impulsion outlet connected to the inlet mouth of the inlet duct and an aspiration inlet connected to the outlet mouth of the outlet duct.

[0022] More preferably, this compressor may comprise additionally a separator provided in the path of the ionic liquid through the pumping system to separate the ionic liquid from possibly present dragged gas.Second aspect: sealing method

[0023] The second aspect of the present invention is directed to a sealing method of a packing such as the one disclosed in the previous paragraphs by means of an ionic liquid.

[0024] More specifically, the sealing method comprises pumping an ionic liquid through the inlet duct and receiving the ionic liquid through the outlet duct, the ionic liquid passing through the cavity of the additional sealing unit making up a barrier against gas leaks. Further, an additional step of separating the ionic liquid from gas that might have been dragged by the ionic liquid.Brief disclosure of the figures

[0025] The details of the invention are shown in the accompanying figures, which are not to be understood as a limitation of the scope of the invention: Fig. 1 shows a schematic longitudinal section of a conventional reciprocating compressor. Fig. 2 shows a sectioned perspective view showing the packing of a conventional reciprocating compressor. Fig. 3 shows a sectioned perspective view of a packing according to the present invention. Fig. 4 shows a longitudinal section view of the packing according to the present invention. Detailed description of the invention

[0026] An example of the present invention is now disclosed with specific reference to Figs. 3 and 4. This example is specifically directed to a hydrogen reciprocating compressor, although it is understood that the concept of the invention is applicable to other types of compressors and to other gasses.

[0027] The packing (1) of the present invention mainly comprises a fixation plate (2) connected to a plurality of sealing units (3 A -3 F ) provided ones against the others to form a longitudinal piling. In this specific example, the packing (1) has six sealing units (3 A -3 F ), each of which comprises a body (31) and a sealing disc (32). The shape and structure of the body (31) and the sealing disc (32) of the sealing units (3 A -3 F ) is essentially conventional. That is, each body (31) has a cylindrical shape having an inner duct configured for the passage of the rod (V) of the reciprocating compressor (CR). This inner duct comprises a cylindrical widening of greater diameter at a longitudinal section, thereby having an annular cavity against which the respective sealing disc (32) is provided. The effect of the pressure within the cavity (CA) of the cylinder of the compressor (CR), the sealing discs (32) are compressed against the wall of the body (31) formed by the mentioned cylindrical widening, thereby making up a barrier against hydrogen leaks. As mentioned above, however, this conventional barrier is not completely airtight.

[0028] To solve this problem, in the present invention an additional sealing unit (6) is provided between a first subset formed by three sealing units (3 A , 3 B , 3 C ) and a second subset formed by the remaining three sealing units (3 D , 3 E , 3 F ). The additional sealing unit (6) also has an essentially cylindrical shape and is provided with a central cylindrical cavity (61) oriented in the longitudinal direction through which the rod (V) passes. This cavity (61) has a greater diameter than the rod (V), and therefor between the rod (V) and the inner walls of the cavity (61) there is a space shaped as a cylindrical ring. This space will be filled with ionic liquid (LI) by means of the circuit disclosed below.

[0029] The circuit for feeding the ionic liquid (LI) to the mentioned cavity (61) is formed essentially by an inlet duct (4) and an outlet duct (5). The inlet duct (4) has an inlet mouth (4E) provided at the fixation plate (2). A first section (46) of the inlet duct (4) continues in the longitudinal direction, passing completely through the fixation plate (2). Then, the inlet duct (4) has sections (4 A , 4 B , 4c) passing longitudinally through the sealing units (3 A , 3 B , 3c) of the first subset which are adjacent ones to the others, until arriving at a last section (46) provided in the additional sealing unit (6). This last section (46) does not have a longitudinal direction, but it has a very short longitudinal portion and, it then descends (according to the orientation shown in the figures) in an essentially radial direction, although with a longitudinal component, until connecting with the cavity (61) of said additional sealing unit (6).

[0030] The outlet duct (5) is similar to the inlet duct (4), although it is provided at a diametrically opposite position. Specifically, the last section (56) of the outlet duct (5) has an essentially radial direction, plus a short longitudinal portion, to connect the cavity (61) with longitudinal intermediate sections (5A, 5B, 5C) provided at the respective sealing units (3 A , 3 B , 3 C ) of the first subset, until arriving at the first section (52) provided at the fixation plate (2). This first section (52) exits at an outlet mouth (5S).

[0031] Although not shown in these figures, a pumping system pumps the ionic liquid (LI) through the inlet mouth (4E), causing it to pass through the mentioned circuit until exiting through the outlet mouth (5S). This ionic liquid (LI) passes through the cavity (61) of the additional sealing unit (6), filling it completely. Upstream or downstream the pumping system a separator can be provided for separating hydrogen rests that might have been dragged by the ionic liquid (LI). The additional sealing unit (6) thereby conforms an extremely effective barrier against hydrogen leaks.

Claims

1. Compressor packing (1) sealed with ionic liquids, comprising a fixation plate (2) fixed to a plurality of sealing units (3A-3F) provided ones against the others forming a longitudinal piling, where each sealing unit (3A-3F) comprises a body (31) and, at least, a disc (32) housed inside said body (31), where the packing (1) is configured to be fixed by means of a fixation plate (2) to an end wall of the chamber (CA) of a compressor for separating said chamber (CA) from a longitudinally adjacent space (ES) of the compressor to prevent leaks, characterized by further comprising an inlet duct (4) and an outlet duct (5) in communication with a cavity (61) of an additional sealing unit (6) for pumping an ionic liquid (LI) towards said cavity (61), the ionic liquid (LI) in said cavity (61) functioning as a barrier against gas leaks.

2. Packing (1) according to claim 1 where the additional sealing unit (6) is provided between a first subset of sealing units (3A, 3B, 3C) an a second subset of sealing units (3D, 3E, 3F), such that the inlet duct (4) and the outlet duct (5) pass through the fixation plate (2) and the first subset of sealing units (3A, 3B, 3C) in the longitudinal direction.

3. Packing (1) according to any of the previous claims, where the inlet duct (4) and the outlet duct (5) are provided in diametrically opposite positions of said packing (1).

4. Packing (1) according to any of the previous claims, where: - the fixation plate (2) comprises an inlet mouth (4E) followed by a first section (42) of the inlet duct (4), and an outlet mouth (5S) followed by a first section (52) of the outlet duct (5); - the first subset of sealing units (3A, 3B, 3C) adjacent the fixation plate (2) comprises respective intermediate sections (4A, 4B, 4C; 5A, 5B, 5C) respectively of the inlet duct (4) and the outlet duct (5); and - the additional sealing unit (6) comprises a last section (46) of the inlet duct (4) connecting the cavity (61) with the section (4c) of the adjacent sealing unit (3c) and a last outlet section (56) connecting the cavity (61) with the section (5c) of said adjacent sealing unit (3c).

5. Compressor comprising a packing (1) according to claim 4, further comprising an ionic liquid (LI) pumping system connected between the inlet mouth (4E) and the outlet mouth (5S) of the fixation plate (2).

6. Compressor according to claim 5, further comprising a separator provided in the path of the ionic liquid through the pumping system to separate the ionic liquid from possibly present dragged gas.

7. Method for sealing the packing (1) of any of claims 1-4 by means of an ionic liquid (LI), characterized by comprising pumping an ionic liquid (LI) through the inlet duct (4E) and receiving the ionic liquid (LI) through the outlet duct (5S), the ionic liquid passing through the cavity (61) of the additional sealing unit (6) making up a barrier against gas leaks.

8. Method for sealing the packing (1) according to claim 7, further comprising separating the ionic liquid (LI) from possibly present dragged gas.

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