METHOD FOR OPERATING A COMPRESSOR, AND COMPRESSOR

Abstract

The invention relates to a method for operating a compressor (100), wherein an ionic liquid (a) is used as an operating liquid, and wherein two different materials (c, d) of the compressor (100) are brought in contact with the ionic liquid (b) and form an electrochemical element. In order to partially balance a voltage (U) of the electrochemical element at the compressor (110), a counter voltage (UG) is applied. The invention further relates to such a compressor (100).

Description

The invention relates to a method for operating a compressor in which an ionic liquid is used as the operating fluid, and to such a compressor.

PRIOR ART

Compressors are used in particular for compressing gaseous media. For this purpose, the medium can be displaced, for example, by means of an operating fluid in a displacement cylinder. In this context, such compressors are also referred to as piston-less compressors.

An ionic liquid can be used as the operating fluid. This is then present in particular in an actual hydraulic oil circuit and in a gas circuit. Ionic liquids have the advantage that they have no or at least no measurable vapor pressure. Therefore, gas can be compressed in the manner described without parts of the operating fluid remaining in the compressed gas, as is the case with conventional operating fluids such as hydraulic oil.

Ionic liquids are, in particular, liquid salt, which therefore forms an electrolyte within the compressor or the compressor system. Since, as a rule, different materials are used in such a compressor for different components or parts of the compressor with which the ionic liquid is also in contact, an electrochemical element is formed. In this case, the material or element that is less noble in relation to the electrochemical series is dissolved in the ionic liquid and is degraded or consumed. At another point, this material correspondingly accumulates. Overall, this leads to a reduced service life or running time of the compressor.

Against this background, the object is to provide an option for extending service life or running time of such an ionic compressor.

SUMMARY OF THE INVENTION

This object is achieved by a method for operating a compressor and a compressor having the features of the independent claims. Preferred embodiments are the subject matter of the dependent claims and the following description.

Advantages of the Invention

The present invention is based on a method for operating a compressor in which an ionic liquid is used as the operating fluid. If such a compressor has two different materials which are brought into contact with the ionic liquid, an electrochemical element is automatically formed.

Suitable ionic liquids in this case are preferably compositions which have one of the following substances:

• • a compound in accordance with formula (I)

wherein R₁ and R₂ may be, independently of one another, hydrogen or a substituted or unsubstituted C1-C8 alkyl, in particular a substituted or unsubstituted C1-C4 alkyl, wherein the compound according to formula (I) is in particular a 1-ethyl-3-methylimidazolium.

• • a quaternary ammonium compound, in particular a compound of the formula

N⁺R₄  (II),

wherein each R may be, independently of one another, a substituted or unsubstituted C1-C4 alkyl, wherein the alkyl may in particular be substituted by OH, wherein the compound according to formula (II) is in particular an N,N,N-trimethylethylammonium or a tris(2-hydroxyethyl)-methylammonium.

The composition can likewise have a counter-ion, in particular Cl⁻.

Relevant components or parts of the compressor which may be affected in this case are in particular cylinder heads, pipelines, pistons, valve housings and valves. Suitable materials are, for example, iron (or steel), aluminum and zinc.

According to the invention, it is now provided that a counter-voltage is applied to the compressor at least for partially equalizing a voltage of the electrochemical element. It is particularly useful to equalize the voltage as completely as possible, but at least, for example, 80%, in particular 90%.

By applying such a counter-voltage, current (that is to say external current) is thus externally introduced into the compressor, and thus the dissolution of the correspondingly less noble material or element is counteracted or even stopped. It goes without saying that such a counter-voltage can be applied not only once between two materials, but also between additional pairs of materials when there are additional different materials. The counter-voltage can be generated by a suitable voltage source and can be applied at suitable points in the compressor or the corresponding components or parts.

It is now conceivable to determine the level of the counter-voltage in advance, for example based on the electrochemical series and the voltage of the relevant materials which can be derived therefrom. In the case of aluminum (E₀=−1.66 V) and zinc (E₀=−0.76 V), a voltage of (absolute) 0.9 V results, for example. In the case of zinc and iron (E₀=−0.44 V), a voltage of (absolute) 0.32 V results, for example. The counter-voltage can then be correspondingly specified.

However, it is particularly preferred if the voltage of the electrochemical element is measured and the counter-voltage is set based thereon. For this purpose, a suitable measuring device can be provided which, for example, detects the applied voltage at suitable points of the various materials. This then enables a particularly precise setting or specification of the counter-voltage and thus a compensation of the voltage caused by the electrochemical element which is as extensive as possible. This ultimately leads to minimal wear of the materials of the compressor and thus of the compressor as a whole.

It is also preferred for the counter-voltage to be set as part of a regulation. In this way, possible deviations during operation of the compressor can be equalized.

A reciprocating compressor and/or a multistage compressor is preferably used as the compressor, in particular, for example, a multistage reciprocating compressor. Such compressors are relatively simple in design, but nevertheless benefit from the advantages of the ionic liquid as the operating fluid. In addition, screw compressors, scroll compressors, rotary compressors, or compressors in which two-phase mixtures can be used, are suitable.

It is advantageous if a gas, in particular hydrogen, or a gas mixture is compressed by means of the compressor. As already mentioned, the use of the ionic liquid yields the advantage that no residues of this liquid remain in compressed gas and thus a particularly pure, compressed gas can be obtained. This is of particular interest especially in the case of hydrogen, since hydrogen is used, for example, for drives, in particular with fuel cells.

The subject matter of the invention is further a compressor in which an ionic liquid is provided as the operating fluid, and in which two different materials of the compressor are in contact with the ionic liquid and form an electrochemical element. This is in particular a so-called an ionic compressor. In addition, a voltage source is now provided, with which a counter-voltage can be applied to the compressor at least for partially equalizing a voltage of the electrochemical element.

Preferably, a measuring device is also provided for measuring the voltage of the electrochemical element, wherein the voltage source is configured to set the counter-voltage on the basis of the measured voltage.

It is advantageous if a control and/or regulating unit is provided for setting and/or regulating the counter-voltage. It is also advantageous if the compressor is configured as a reciprocating compressor and/or with multiple stages.

With regard to the detailed explanation as well as further preferred embodiments and advantages of the compressor according to the invention, reference is made to the above explanations, which are correspondingly applicable here, concerning the method according to the invention, which is explained with reference to a compressor, in order to avoid repetitions.

The invention is schematically represented in the drawing using exemplary embodiments and will be described below with reference to the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 schematically shows a compressor according to the invention in a preferred embodiment, which is suitable for carrying out a method according to the invention.

DETAILED DESCRIPTION OF THE DRAWING

FIG. 1 shows a compressor 100 according to the invention in a preferred embodiment. In this case, the compressor has five cylinders 110, 111, 112, 113 and 114 and an additional chamber 150. The cylinder 110 has a movable piston 120 as well as an inlet valve 140 and an outlet valve 141, wherein these two valves are each arranged in a cylinder head 130.

The additional four cylinders are of similar design, but for the sake of clarity no reference numerals are shown here. It should also be noted that the additional cylinders 111 to 114 are smaller than the cylinder 110 in order to allow a corresponding stage-like compression. The respective pistons can be moved, for example, via a suitable drive according to the prior art (not shown here).

A gas b, for example hydrogen, can now be introduced into the cylinder 110 via an inlet 121. Gas compressed within the cylinder 110 can then be directed into the next cylinder 111 via a pipeline 120 (or another suitable connection). Via additional such pipelines, the still further compressed gas can finally be guided into the chamber 150 and from there out of the compressor 100 via an outlet 122. In addition, a sealable connecting line 123 is provided from the inlet 121 to the chamber 150. The chamber 150 serves to separate the ionic liquid from the gas stream; the connecting line 123 permits a flow of liquid due to the pressure difference between the first and last compressor stages, as a result of which a targeted injection of ionic liquid into the gas stream is possible.

In each of the cylinders 110 to 114 as well as in the chamber 150, an ionic liquid a, as mentioned at the outset, is now provided as the operating fluid. In addition to a cooling and/or lubricating effect on the compressor, a property of this ionic liquid that no residue remains in the gas during the compression of the gas b. As already mentioned at the outset, this is due to the fact that an ionic liquid has no or at least no measurable vapor pressure.

Furthermore, a measuring device 160 is now provided, by means of which, for example, a voltage U between the piston 120 and the cylinder 110 or its wall is measured in this case. If the piston 120 and the cylinder 110 or its wall are made of different materials, these two materials form an electrochemical cell with a measurable—here by means of the measuring device 160—voltage U. For example, the cylinder 110 or its wall can be made of steel (denoted by c), whereas the piston 120 can be made of aluminum (denoted by d). As has likewise already been mentioned, this results in one of the materials dissolving in the ionic liquid b and in particular depositing on the other material.

Furthermore, a voltage source 170, which can in particular also be part of a control and/or regulating unit, is now provided. By means of this voltage source 170, it is now possible to apply a counter-voltage U_G to the compressor, in this case between the piston 120 and the cylinder 110 or its wall, so that a current I_G flows. The counter-voltage can now be matched as precisely as possible to the measured voltage so that, as a result, there is no or at least a significantly lower voltage between the corresponding components or parts of the compressor, thus preventing or at least reducing a dissolution of the one material in the ionic liquid. This correspondingly increases the service life of the compressor 110.

It goes without saying that additional such measuring devices and voltage sources (or control and/or regulating units) can also be provided, namely in each case between two other components or parts with different materials. In particular, the aforementioned components or parts are suitable here. Overall, the service life of the compressor 110 can be significantly increased in this way.

Claims

1. Method for operating a compressor (100) in which an ionic liquid (a) is used as the operating fluid, and in which two different materials (c, d) of the compressor (100) are brought into contact with the ionic liquid (b) and form an electrochemical element,

characterized in that a counter-voltage (UG) is applied to the compressor (110) at least for partially equalizing a voltage (U) of the electrochemical element.

2. Method according to claim 1, wherein the voltage (U) of the electrochemical element is measured, and the counter-voltage (UG) is set based thereon.

3. Method according to claim 1, wherein the counter-voltage (UG) is set as part of a regulation.

4. Method according to claim 1, wherein a reciprocating compressor, a screw compressor, a scroll compressor, a rotary compressor, a compressor in which a two-phase mixture can be used, and/or a multi-stage compressor is used as the compressor (100).

5. Method according to claim 1, wherein a gas (b), in particular hydrogen, or a gas mixture is compressed by means of the compressor.

6. Compressor (110) in which an ionic liquid (a) is provided as the operating fluid, and in which two different materials (c, d) of the compressor (100) are in contact with the ionic liquid (a) and form an electrochemical element,

characterized by a voltage source (170) with which a counter-voltage (UG) can be applied to the compressor (U) at least for partially equalizing a voltage (U) of the electrochemical element.

7. Compressor (100) according to claim 6, comprising a measuring device (160) for measuring the voltage (U) of the electrochemical element, wherein the voltage source (170) is configured to set the counter-voltage (UG) based on the measured voltage (U).

8. Compressor (100) according to claim 6, comprising a control and/or regulating unit for setting and/or regulating the counter-voltage (UG).

9. Compressor (100) according to claim 6, which is configured as a reciprocating compressor, a screw compressor, a scroll compressor, a rotary compressor, a compressor in which a two-phase mixture can be used, and/or with multiple stages.