EP3071832A1

EP3071832A1 - Piston compressor and method for compressing a cryogenic gaseous medium, in particular hydrogen

Info

Publication number: EP3071832A1
Application number: EP14799102.0A
Authority: EP
Inventors: Robert Adler; Christoph Nagl
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2013-11-21
Filing date: 2014-11-05
Publication date: 2016-09-28
Also published as: DE102013019499A1; US20160281705A1; JP2016537558A; WO2015074740A1

Abstract

The invention relates to a piston compressor (1) for compressing a cryogenic fluid medium (M), in particular in the form of hydrogen. It is provided according to the invention that an encircling first gap (S) between a first piston (31) and an inner side (300a), facing towards the first piston (31), of a first cylinder (30) is sealed off by means of at least one seal (32), which is provided on the first piston (31), in such a way that leakage medium (M') from the first cylinder interior space (300) passes through said first gap (S) into the interior space (100) of the housing (11) and flows around the rotor (20) and in particular also the stator, wherein the permanent magnets (P) are provided with a coating (B) in order to protect against said medium (M), in particular in order to protect against hydrogenation in the case of a medium (M) in the form of hydrogen. The invention also relates to a method for compressing a cryogenic fluid medium (M), in particular hydrogen.

Description

description

Piston compressor and method for compressing a cryogenic, gaseous

Medium, especially hydrogen

The invention relates to a piston compressor according to claim 1 and a method for compressing a fluid, in particular gaseous, in particular cryogenic medium, in particular in the form of hydrogen, according to claim 8.

In the present context, a cryogenic, fluid medium is to be understood in particular to mean a fluid medium which has a temperature in the range from 0 K to 130 K. A fluid medium is a gaseous or liquid medium or a phase mixture of a gaseous and a liquid phase. The piston compressor according to the invention can, however, also be operated with higher inlet temperatures of, in particular, up to 320 K, that is to say in a range from 0 K to 320 K. Gases have a comparatively very low density under standard conditions compared with other energy sources. In order to store a gas efficiently, it is necessary to increase the mass of the gas in the available storage space. An effective storage of gases is usually realized with an increase of the gas pressure. Presently most common methods and devices for compressing a gaseous medium are compressor systems such as reciprocating compressors, ionic compressors, screw compressors or membrane compressors. Furthermore, methods for conveying and compressing liquid, cryogenic media are known, which are usually realized by piston compressor systems.

Generic methods and devices are used, for example, in natural gas and hydrogen compressor stations, as they are implemented in gas filling stations.

From the prior art DE-B 102006060147, for example, a fluid motor driven by a linear motor is known in which, for example, the stator in the linear motor and the rotor are separated by a split tube and static seals. The aforementioned compressors usually operate with gas inlet temperatures in the range of the ambient temperature of their place of use. In liquefied gas compressor systems, it is therefore necessary to convert the liquid to its gaseous state. The adjustment of the gas inlet temperature in the compressor via evaporator systems. The necessary for the increase in temperature of the medium energy in the evaporator systems, for example, via heat extraction from the environment or by electrical Anheizvorrichtung. On the other hand, high-performance cryopumps must be supplied with liquid. The necessary for supply liquid tanks are due to the limited

Isolation options and the resulting losses of liquid hydrogen as a result of unusable boil-off gas at long idle times extremely uneconomical. Due to the temperature differences occurring in compressors it is

For example, for piston compressors structurally necessary to provide length tolerances associated with an increase in the dead space. The raised

Gas re-expansion due to the relatively large dead space means a reduced flow rate.

In a dead-space compressor (e.g., ionic compressor), the

Crystallization temperature of the ionic liquid use at low

Temperatures. Furthermore, ionic compressors require a horizontal installation position to maintain the liquid column.

Furthermore, reciprocating compressors known from the prior art often can not be built pressure-encapsulated, whereby a certain leakage of the medium to be compressed to the environment must be accepted. Even static

Gaskets allow only a limited leak-proofing. In the case of the promotion and compression of hydrogen according to the system disclosed in DE-B 102006060147, the skilled person is also faced with the problem of hydrogenation of

Permanent magnets by the leakage gas.

On this basis, the object of the present invention is an improved reciprocating compressor and a corresponding method for compacting a fluid (eg gaseous), and in particular cryogenic medium, in particular hydrogen, indicate.

This object is achieved by a piston compressor with the features of claim 1. Advantageous embodiments of the piston compressor according to the invention are specified in the corresponding subclaims and are further described below.

According to claim 1, the piston compressor according to the invention for compressing a particular cryogenic, fluid medium, in particular in the form of

Hydrogen, a linear motor having a stator and a rotor having permanent magnets, wherein the stator is designed in a known manner to generate a magnetic field for driving the rotor to the rotor along a longitudinal axis along which the rotor extends, to move back and forth relative to the stator. Furthermore, the reciprocating compressor has a housing of the

A linear motor defining an inner space in which the rotor and the stator are arranged, and a first cylinder of the reciprocating compressor connected to the housing, which defines a first cylinder interior, of which

Interior going off, as well as a first cylinder head of the first cylinder, with an inlet through which the medium in the first cylinder interior of the first cylinder can be introduced, and with an outlet through which compressed medium from that first cylinder interior can be dispensed. Furthermore, the reciprocating compressor has a first piston, which extends into the first cylinder interior and extends along the longitudinal axis, which is connected to the rotor, so that the first piston is entrained by the rotor and moved back and forth along the longitudinal axis, the first piston being designed for this purpose is to compress located in the first cylinder interior medium when the first piston moves in the direction of the first cylinder head. According to the invention it is now provided that a

Circumferential first gap between the first piston and an inner side of the first cylinder facing the first piston is sealed with at least one seal provided on the first piston such that only a portion of the medium, referred to herein as leakage medium, from the first cylinder interior through that first gap in the interior of the housing can pass and flows around the rotor and in particular also the stator, wherein the permanent magnets of the rotor for protection against that leakage medium, in particular for protection against a Hydrogenation and further embrittlement in a medium in the form of hydrogen, are provided with a coating.

The at least one seal provided on the first piston is therefore intended to seal off the first cylinder interior, but as a rule a certain leakage past the seal can not be prevented. The same applies to the second piston (see below).

Preferably, the piston compressor according to the invention or the method explained below is designed or designed to compress a fluid medium. The medium can therefore be purely gaseous or present as a mixture of a gaseous and a liquid phase. Furthermore, the medium may also be present as a liquid.

According to a preferred embodiment of the invention

Piston compressor is provided that said permanent magnets a

Neodymium-iron-boron alloy or are made of this material.

In general, suitable materials for the permanent magnets according to the invention are ferrites and their compounds with zinc and / or nickel and with manganese, as well as strontium ferrites, cobalt ferrites, barium ferrites, and furthermore alloys of samarium cobalt and aluminum-nickel-cobalt.

According to another preferred embodiment of the invention

Piston compressor is provided that the coating of the permanent magnets is given by a nickel-copper-nickel coating. That is, the

Carmine magmas are coated with a layer of nickel, followed by a layer of copper, followed by an (especially outermost) layer of nickel. NiCuNi coatings according to the invention may e.g. be prepared galvanically. Furthermore, a coating of the permanent magnets to protect the

Permanent magnets also have one of the following substances or compounds: aluminum oxide, tungsten, molybdenum, gold, platinum, chromium, cadmium, tin, aluminum, silicates of tungsten and molybdenum, or nickel-aluminum compounds. Furthermore, the coating can also be an oxidation layer of the base material of the permanent magnets, which in particular before

Hydrogenation / embrittlement is generated. Such an oxide layer may e.g. be generated by the unprotected flushing and residence of the permanent magnets in atmospheric oxygen, or preferably by pressurizing the permanent magnets in (in particular high purity) oxygen.

A total layer thickness of the respective coating normal to the surface area of the coating or normal to the individual layers is preferably in the range between 3 μητι to 500 μιη.

Furthermore, it is preferably provided that the interior of the housing via a first leakage return line is in fluid communication with a supply line to the inlet on the first cylinder head, so that the interior of the housing with a pressure

is applied, which corresponds to the pressure in that supply line, wherein preferably the first leakage return line branches off from a first end portion of the inner space, and wherein preferably the first cylinder interior of that first end portion of the interior goes off. According to a further preferred embodiment of the invention, it is provided that the piston compressor has a second cylinder connected to the housing. With such a second cylinder, a two-stage compression of the medium to be compressed can be carried out. Preferably, the second cylinder has a second cylinder interior, which from that interior of the

Housing of the linear motor goes off, and a second cylinder head of the second cylinder, said second cylinder head having an inlet through which the medium to be compressed in the second cylinder interior of the second cylinder can be introduced. Furthermore, the second cylinder head has an outlet, via which the compressed in the second cylinder chamber medium from the second

Cylinder interior can be dispensed. Furthermore, a second piston is preferably provided, which projects into the second cylinder interior and extends along the said longitudinal axis. The second piston is in turn preferably connected to the rotor, so that the second piston is taken by the rotor and moved along the longitudinal axis back and forth, the second piston to is configured to compress medium located in the second cylinder interior, when the second piston moves in the direction of the second cylinder head.

Between the second piston and an inner side of the second cylinder facing the second piston, a circumferential second gap is preferably present, which is sealed with at least one seal provided on the second piston, that only a part of the medium from the second cylinder interior, in turn present is referred to as leakage medium, passes through those second gap in the interior of the housing and there flows around the rotor and in particular also the stator (see above).

Furthermore, it is preferably provided that the interior is on the side of the second cylinder via a second leakage return in fluid communication with the inlet of the inlet to the first cylinder head, in particular those second

Leakage leakage from a second end portion of the interior branches off, the first end portion along the longitudinal axis of the reciprocating compressor

is opposite, wherein preferably the second cylinder interior of that second end portion of the interior goes off. The two cylinders are thus provided on both sides of the linear motor, so that medium is sucked into the one cylinder interior, while it is discharged from the other cylinder interior.

So that the movement of the piston can be influenced, and in particular the stroke of the first or second piston can be regulated, a position detection means for detecting the position of the first and / or second piston is preferably provided. In this case, encoderless methods may be used which use, for example, design-related, position-specific ratios of the inductances in the longitudinal and transverse directions to the central axis of the linear motor, it being possible to deduce the position by the position-specific conditions. Furthermore, methods according to EP-B 1746718 or WO-A 1992019038 can be used.

According to one embodiment of the invention, the position detecting means comprises a coupled to the first or the second piston encoder which generates a first magnetic field (the encoder may be formed for example by a magnet) and a measuring element, for example, having a pressure-resistant rod in which magnetic, elastically deformable body is arranged or mounted. The displacement sensor is in this case designed to generate a magnetic longitudinal field in the measuring element. Furthermore, the position detection means is designed to allow a current signal to pass through the measuring element, so that a second magnetic field arises radially around the measuring element. When the two magnetic fields coincide, a deformation of the elastic body takes place, as a result of which a torsion wave passes through the measuring element, which is detected by the position detection means. About the time difference between the current pulse and arrival of the torsion wave is on the position of the encoder and thus to the position of the piston or

inferred.

Furthermore, the problem of the invention by a method for compressing a particular cryogenic, fluid medium, in particular in the form of

Hydrogen dissolved, in particular using a reciprocating compressor according to the invention, wherein according to claim the fluid medium is compressed at least in the first cylinder interior by means of the first piston, wherein only a portion of the medium (referred to as leakage medium) passes through that first gap in the interior of the housing and flows around the rotor and in particular also the stator, and wherein in particular the permanent magnets are protected from that medium by the coating of the permanent magnets, in particular before a hydrogenation and further an embrittlement.

According to an advantageous embodiment of the method according to the invention is further provided that in the first cylinder interior compressed medium from the first cylinder interior is discharged and in the second cylinder interior by means of the second piston is re-compressed, in particular only a portion of the medium in turn from the second cylinder interior on the second gap passes into the interior of the housing of the linear motor and there flows around the rotor and in particular also the stator.

Furthermore, it is preferably provided that medium which has come into the interior space is returned to the inlet on the first cylinder head via the first leakage return line and / or the second leakage return line. The interior of the housing is thus pressurized as described above and allows a return of the Leakage medium to the inlet on the first cylinder head (first compressor stage of the reciprocating compressor).

Furthermore, it is preferably provided, as already indicated above, that the position of the rotor, the first and / or the second piston is preferably detected, in particular with the above-mentioned position detection means. Preferably, the stroke of the first and / or the second piston is controlled so that the corresponding dead space in the first and / or second cylinder interior is reduced in order to increase the efficiency of the reciprocating compressor. The respective dead space is that volume which delimits the end face of the respective piston together with the circumferential inner side of the respective cylinder and the inner side of the respective cylinder head facing the piston. When the dead space disappears, the piston or its end face touches the respective cylinder head. In the method according to the invention, it is particularly preferred that the first medium is supplied in liquid form to the reciprocating compressor and in the

is transferred to the general gaseous state shortly before the introduction into the first cylinder chamber, preferably for evaporating the medium

Ambient heat and / or waste heat of the linear motor is used.

For the purpose of compression, it is provided that the intake temperature of the medium to be compressed just above the equilibrium point of the

corresponding intake pressure is. In addition to a liquid supply, a gaseous, cryogenic supply is also possible in which the medium to be compressed from a source is transported in a cryogenically cryogenic manner into the first cylinder interior.

Further features and advantages of the invention are intended in the following

Figure description of an embodiment of the invention will be explained with reference to the figures.

Show it:

Fig. 1 is a partially sectioned view of an inventive

Piston compressor; and Fig. 2 is a further partially sectional view of the piston compressor according to the invention shown in FIG. 1.

1 shows in connection with FIG. 2 a piston compressor 1 according to the invention. The piston compressor 1 has a linear motor 10 which has a stator and a rotor 20 which can be moved back and forth along a longitudinal axis L by means of the stator. The stator generates a magnetic field that interacts with permanent magnets P of the rotor 20, so that it is moved back and forth along the longitudinal axis L. Stator and rotor 20 of the linear motor 10, which is configured in the present case as a tubular linear motor 10, are arranged in a housing 11 of the linear motor 10, which limits an inner space 100 of the linear motor 10. Of the

Piston compressor 1 has on both sides of the housing 1 1 along the longitudinal axis L a first cylinder 30 and a second cylinder 70, which surround a first cylinder interior 300 and a second cylinder interior 700. These two cylinder inner spaces 300, 700 start from a first end section 100a or a second end section 100b of the inner space 100 of the housing 1 along the longitudinal axis L. The two end portions 100a, 100b of the inner space 100 of the housing 11 are opposite each other along the longitudinal axis L. In the first cylinder interior 300 slides a first piston 31, wherein a

circumferential gap S between the piston 31 and the first piston 31 facing the inside 300 a of the first cylinder 30 is formed, which is sealed by at least one, preferably by a plurality, in particular slotted seals 32 which seal in dynamic operation, but not statically.

Such slotted seals 32 are particularly characterized in that they have at one point a transection, which can be done by a parallel to the cylinder axis of the seal, oblique or three-dimensionally offset cut. The seal 32 may be made with such a separation, or the separation is performed after the seal 32 is made.

In an analogous manner slides in the second cylinder interior 700, a second piston 70, which in turn with at least one, preferably more, in particular slotted

Seals 72 abuts an inner side 700 a of the second cylinder 70 facing the second piston 71 and thus seals a circumferential second gap S 'between the second piston 71 and said inner side 700 a of the cylinder 70. The two pistons 31, 71 of the thus formed compressor stages oscillate in operation between their reversal points in the two cylinders 30, 70 along the longitudinal axis L back and forth and are each by a device on the

Piston rod or the rotor 20 of the tubular linear motor 10 centered and fixed. In each case a centering adapter 21, 23 is seated on the respective free end of the rotor 20. The centering adapters 21, 23 are each provided with a thread. The

Mating rings 22, 24 are provided with a corresponding mating thread and screwed to the respectively associated centering adapter 21, 23, wherein the

Centering adapter 21, 23 are screwed on the one hand to the rotor 20 and the respective piston 31, 71 is clamped between the respective centering adapter 21, 23 and the respective mating ring 22,24, so that a rigid connection between the rotor 20 and the piston 31, 71st resuliert.

The second piston 71 is designed in two parts and has two sections 710, 720, wherein the first portion 710 is fixed to the rotor 20, via said centering adapter 23 and the associated counter-ring 24, and wherein the second portion 720 of the second Piston 71 from the interior 100 fro in the second cylinder 700 and there in the second cylinder interior 700

compressed medium M compressed.

The two cylinders 31, 71 are each with a first and a second

Cylinder head 40, 80 closed at the end, via which the medium to be compressed M is introduced into the respective cylinder 30, 70 and output from the respective cylinder densified.

Furthermore, the cylinders 30, 70 are each centered about a centering surface of a flange 12 with respect to the respective flange 12, wherein those flanges 12 are in turn centered on the housing 11 of the linear motor 10 via a centering surface. The two flanges 12 are each screwed to the front side of the housing 1 and thus place the cylinder 30, 70 on the housing 11 firmly. The sealing of the housing 11 or the cylinder 30, 70 against the environment takes place via a respective static seal in the form of an O-ring 101, 102, which are each arranged between a flange 12 and the housing 11. The housing 11 is thus pressure-sealed. Of the

Linear motor 10 itself is fixed via a flange holder 13 on the housing 1 on its respective footprint. Furthermore, each piston 31, 71 has an annular, on the respective piston circumferential guide belt 33, 73 for receiving the radial forces. As already indicated, during the oscillating movement of the two pistons 31, 71, parts of the medium M located in the respective cylinder interior 300, 700 can pass through said gaps S, S 'into the interior 100 of the housing 11, this seal leakage passing over a first and a first a second leakage return 51, 52 is returned in the form of a pipeline to the input side of the reciprocating compressor 1.

In this case, the first leakage return line 51 branches off at the first end section 100a of the interior 100 and is in fluid communication with a supply line 61, via which medium M to be compressed can be fed via an inlet 41 of the first cylinder head 40. This inlet 41 is closed by a valve in the form of a suction valve 410. Due to the pressure-sealed construction as well as the said

Leakage return is the stator and the rotor 20 of the linear motor 10th

in accordance with the inlet pressure of the reciprocating compressor 1 at the inlet 41

pressurized. Stator and rotor 20 are accordingly flows around the leakage gas M 'and transferred during operation heat to the leakage gas M'. In the first cylinder interior 300 by means of the first piston 31 compressed medium M is discharged through an outlet 42 on the first cylinder head 40 which is closable with a pressure valve 420.

The first cylinder head 40 with the suction and pressure valve 410, 420 is seated at one end of the first cylinder 30 and in turn is screwed via a coupling ring on the first cylinder 30 with this. In the same way, at the opposite end of the second cylinder 70, the second cylinder head 80 is fixed with a coupling ring, the second cylinder head 80 in turn having an inlet 81 and an outlet 82, which are closable with a suction valve 810 and pressure valve 820. From the outlet 42 of the first cylinder head 40 leads a connecting line (not shown) to the inlet 41 of the second cylinder head 80, wherein the feed line 61 and this connecting line are preferably each made heat-insulated.

When compressing a hydrogen-containing medium M must

Permanent magnets P of the linear motor 10 are protected against the hydrogen molecules. The high-performance magnets used in high-performance linear motors 10 preferably consist of compounds of the elements neodymium-iron-boron. neodymium is a metal of the rare earths. Rare earths are used in metal hydride storage systems for hydrogen storage. The case used effect of adsorption and subsequent incorporation of the hydrogen atoms in the metal grid is extremely undesirable in the linear motor 10 and would permanently destroy the permanent magnet P. The protection against this hydrogen storage of the permanent magnets P is preferably carried out by a nickel-copper-nickel coating of the permanent magnets P.

The positioning of the two pistons 31, 71 in the corresponding

Cylinder interiors 300, 700 are preferably carried out via a position detection means 90, which may be a suitable displacement measuring system or else a sensorless control system. The drive concept by means of the tubular linear motor 10 thus allows highly dynamic interventions in the

Movements of the reciprocating compressor 1, during the compression process. Thus, it becomes possible to make the reciprocating compressor 1 variable and to respond to change in length due to thermal expansions and thus perform a Hubanpassung. The adjustment of the piston stroke of the two pistons 31, 71 thus achieves a minimization of the dead space, which has a positive effect on the

Flow rate of the reciprocating compressor 1 effects.

The compression of a gaseous, cryogenic medium M, in particular in the form of hydrogen, by means of the piston compressor 1 according to the invention is preferably carried out by said hydrogen M by a preferred heat-insulated lead 61 from a hydrogen supply via the suction valve 4 0 of the first cylinder head 40 in the first compression chamber or The first cylinder interior 300 is sucked in, wherein in the next cycle the sucked hydrogen M is compressed by the first piston 31 (in this case, the first piston 31 moves toward the first cylinder head 40) and is pushed by the pressure valve 410 on the first cylinder head 40. The. deferred, compressed gas M is sucked through said connecting line, which is also preferably carried out heat-insulated, through the suction valve 810 of the second cylinder head 80 of the second compressor stage and then compressed in the second cylinder interior 700 by corresponding movement of the second piston 71 and pushed out via the pressure valve 820 , The hydrogen is increased by the pressure increase a density increase. Due to the design, this runs Conversely, compression of the first stage and suction of the second stage simultaneously.

The compaction according to the invention at low temperature levels likewise means a small enthalpy difference of the medium M in the intake state to the compression-reduced state compared to a process with the same

Pressure potentials at higher temperature (eg gas at room temperature). This reduces the work required for compaction, which results in a reduced power requirement.

The compression according to the invention at a low temperature level makes it possible, in particular, to dispense with a DC link heat exchanger, since the DC link temperature as a result of a temperature increase by the

Compression process after the first compressor stage continues under the on the

Installation sites usually located ambient temperature is settled.

The compaction according to the invention at low temperature levels continues to be accompanied by high specific densities of the media M, whereby one for pure

Gas compressor relatively high flow rate is achieved.

Due to the preferred fully hermetic construction of the compressor system 1 eliminates a dynamic sealing of moving parts against the environment, whereby the technically known advantages of the static seal can be used. The hermetic construction of the piston compressor system 1 prohibits the

Contamination of the housing 11 by ambient air. This is realized by the housing 11 is constantly subjected to pressure, which corresponds to the inlet pressure of the first compressor stage. This allows a return of the gas leakage M 'of the dynamic piston seals 32, 72 in the respective intake tract or

Cylinder interior 300, 700.

The above-described device for piston fixation on the

Linear motor piston rod or to the so-called rotor 20 allows easy replacement of the two pistons 31, 71 during maintenance. Furthermore, with the adjustment of the cylinder diameter at the same time, the piston diameters can be so be varied that either higher compression end pressures are achieved, or an increase in the capacity occurs.

In the case of compressor stations 1 supplied with liquid, it is also possible to suck the boil-off gas produced as a result of a heat input into the tank and to use it for the compression.

Despite the process-related high achievable delivery capacity of the compressor system 1, the space requirement remains low compared to the common gas compressor systems.

The compressor system 1 described above can be operated both horizontally and vertically with advantage.

In one embodiment of the piston compressor 1 for hydrogen compression, it is provided that the first piston 31 has a diameter of 42 mm and the second piston 71 has a diameter of 16 mm. The frequency of the Kolbenwegegung is preferably at 10 Hz, the mass flow of the working medium M is preferably 10 kg / h, the oscillating mass force (composed of the individual oscillating mass forces of the oscillating components: rotor 20,

Centering adapter 21, 23, counter ring 22, 24, piston 31, 71, seal 32, 72,

Guide band 33, 73) is preferably 50 kg. The stroke of the pistons 31, 71 is preferably 120 mm. The piston movement preferably satisfies a sine function. The resulting compaction force is 10 kN, the footprint of the

Compressor 1, that is, the area projected in plan view, is about 2.5 m by 1 m. The achievable by the linear motor 10 maximum force is 13.8 kN and the of

Linear motor 10 achievable maximum speed is 4.1 m / s. The rated power of the linear motor 10 is 26.6 kW.

The hydrogen is preferably added at 60 K and a pressure of 6 bara in the first cylinder interior 300, compressed and output at 184 K and 133 bara and pressed into the second cylinder interior 700, where it is compressed again and with 288 K and 600 bara is issued. LIST OF REFERENCE NUMBERS

1 piston compressor

10 linear motor

11 housing

12 flange

13 flange

20 runners

21 centering adapter

22 mating ring

23 centering adapter

24 counter ring

30 First cylinder

31 First piston

32 seal

33 leader band

0 First cylinder head 1 inlet

2 outlet

1 First leakage return 2 Second leak return 1 Supply line

0 second cylinder

1 second piston

2 seal

3 leadership band

0 Second cylinder head 1 inlet

2 outlet

0 position detection means 1 displacement sensor

2 measuring element

100 interior

100a First end section 100b Second end section

101, 102 O-rings (static seals)

300 First cylinder interior

300a inside

400 housing

410 valve (suction valve)

420 valve (pressure valve)

700 second cylinder interior

700a inside

810 valve (suction valve)

820 valve (pressure valve)

M medium (e.g., hydrogen)

M 'leakage medium

P permanent magnets (rotor)

B coating

L longitudinal axis

S first gap

S 'second split

Claims

claims

1. piston compressor, for compressing a cryogenic, fluid medium, in particular in the form of hydrogen, with:

- A linear motor (0) having a stator and a permanent magnet (P) having rotor (20), wherein the stator is adapted to

Driving the rotor (20) to generate a magnetic field to reciprocate the rotor (20) along a longitudinal axis (L) along which the rotor (20) extends relative to the stator,

a housing (11) of the linear motor (10) defining an internal space (100) in which the rotor (20) and the stator are arranged,

a first cylinder (30) connected to the housing (11) and defining a first cylinder interior (300) extending from that interior (100),

- A first cylinder head (40) of the first cylinder (30), with an inlet (41) through which the medium (M) in the first cylinder interior (300) can be introduced, and with an outlet (42), via the compressed medium (M) from that first cylinder interior (300) can be output,

- One in the first cylinder interior (300) protruding along the

Longitudinal axis (L) extending first piston (31) which is coupled to the rotor (20), so that the first piston (31) from the rotor (20) entrained and along the longitudinal axis (L) reciprocated, wherein the first piston (31) is designed to compress medium (M) located in the first cylinder interior (300) in the event of a movement of the first piston (31) towards the first cylinder head (40),

characterized in that a circumferential first gap (S) between the first piston (31) and an inner side (300a) of the first cylinder (30) facing the first piston (31) is provided with at least one seal provided on the first piston (31) ( 32) is sealed, that medium (Μ ') from the first cylinder interior (300) passes through that first gap (S) in the interior (100) of the housing (1) and flows around the rotor (20), wherein the

Permanent magnets (P) for protection against that medium (Μ '), in particular for protection against hydrogenation in a medium (Μ') in the form of hydrogen, with a coating (B) are provided. Piston compressor according to claim 1, characterized in that the

Permament magnets (P) comprise an alloy comprising neodymium, iron and boron, in particular having the composition Nd ₂ Fe ₁₄ B.

Piston compressor according to claim 1 or 2, characterized in that the

Coating (B) is one of the following coatings:

a nickel-copper-nickel coating, in particular the

Coating at least one layer of nickel, followed by a layer of copper, followed by a layer of nickel, and wherein in particular the total layer thickness of the coating is in the range between 3 μηη to 500 pm,

a coating comprising aluminum oxide, tungsten, molybdenum, gold, platinum, chromium, cadmium, tin, aluminum, silicates of tungsten and molybdenum, or nickel-aluminum compounds, or

a coating comprising at least one oxide of the

Permanent magnet material, wherein this coating is preferably prepared by the permant magnets are brought into contact with oxygen.

Piston compressor according to one of the preceding claims, characterized in that the inner space (100) via a first leakage return line (51) in fluid communication with a supply line (61) to the inlet (41) on the first cylinder head (40), so that the inner space (100 ) is acted upon by a pressure corresponding to the pressure in that feed line (61), wherein in particular those first leakage return line (51) branches off from a first end section (100a) of the inner space (100), wherein in particular the first one

Cylinder interior (300) of that first Endabschitt (100a) of the interior (100) goes off.

Piston compressor according to one of the preceding claims, characterized in that the reciprocating compressor (1) further comprises:

- A second cylinder (70) connected to the housing (11) defining a second cylinder interior (700) extending from that interior space (100) and - A second cylinder head (80) of the second cylinder (70), wherein the second cylinder head (80) has an inlet (81) through which the medium (M) in the second cylinder interior (700) can be introduced, and an outlet (82 ), via the compressed medium (M) from that second cylinder interior (700) can be output, and

- A in the second cylinder interior (700) projecting, along the longitudinal axis (L) extending second piston (71) which is coupled to the rotor (20), so that the second piston (71) from the rotor (20) taken along and along the longitudinal axis (L) is moved back and forth, wherein the second piston (71) is adapted to, in the second cylinder interior (700) located medium (M) upon movement of the second piston (71) to the second cylinder head (80) in particular, wherein a circumferential second gap (S ') between the second piston (71) and an inner side (700a) of the second cylinder (70) facing the second piston (71) is provided with at least one second piston (71). provided seal (72) is sealed, that medium (Μ ') from the second cylinder interior (700) passes through that second gap (S') in the interior (100) of the housing (1 1) and the rotor (20) flows around.

Piston compressor according to claims 4 and 5, characterized in that the interior space (100) is in fluid communication with the supply line (61) of the inlet (41) on the first cylinder head (40) via a second leakage return line (52), in particular that second leakage return line (52) from a second

End portion (100b) of the inner space (100) branches off, wherein in particular the second cylinder interior (700) from that second Endabschitt (100b) of the inner space (100) goes off.

Piston compressor according to one of the preceding claims, characterized

characterized in that a position detection means (90) is provided for detecting the position of the first and / or second piston (31, 71), in particular that position detection means (90) comprises a displacement sensor coupled to the first or the second piston (31, 71). 91), the to

is designed to generate a first magnetic field and at those back and forth

Movement of the rotor (20) along a in the interior (100) along the longitudinal axis (L) extending measuring element (92) to be moved, having a magnetic, elastically deformable body, wherein the Position detecting means (90) is adapted to a second magnetic field around the measuring element (92) by applying a current signal to the second

To generate measuring element (92), so that due to an interaction of the two magnetic fields, a torsion wave is generated in the elastically deformable body, wherein the position detecting means (90) is adapted to detect that torsion wave and based on a time difference between the application of the current signal Detecting the torsional wave to determine the said position.

Method for compressing a cryogenic, fluid medium, in particular in the form of hydrogen, using a reciprocating compressor (1) according to one of the preceding claims, wherein the medium (M) at least in the first cylinder chamber (300) compacted by means of the first piston (31) is, wherein a portion of the medium (Μ ') passes through that first gap (S) in the interior (100) of the housing (1) and the rotor (20) flows around, in particular the permanent magnets (P) in front of that medium (Μ ') are protected by the coating (B) of the permanent magnets (P), in particular prior to hydrogenation in a medium (Μ') in the form of hydrogen.

A method according to claim 8, characterized in that in the first

Cylinder interior (300) compressed medium (M) from the first

Cylinder interior (300) is output and in the second cylinder interior (700) by means of the second piston (71) is compressed again, in particular a portion of the medium (Μ ') from the second cylinder chamber (700) via the second gap (S') in the interior (100) of the housing (1) passes and the rotor (20) flows around.

0. The method of claim 8 or 9, characterized in that in the

Interior (100) has reached medium (Μ ') via the first leakage return line (51) and / or the second leakage return line (52) to the inlet (41) at the first

Cylinder head (40) is returned.

1. The method according to any one of claims 8 to 10, characterized in that the position of the rotor (20), the first and / or the second piston (31, 71) is detected, and in particular that the stroke of the first and / or the second piston (31, 71) is controlled so that the dead space in the first and / or second cylinder interior (300, 700) is reduced. 12. The method according to any one of claims 8 to 1 1, characterized in that the medium (M) is supplied to the piston compressor (1) in liquid form and is transferred before being introduced into the first cylinder interior (300) in the gaseous state, wherein in particular for evaporation of the medium

Ambient heat and / or waste heat of the linear motor (10) is used.