WO2022122179A1

WO2022122179A1 - Filter element for a flow of a gas under high pressure

Info

Publication number: WO2022122179A1
Application number: PCT/EP2021/025441
Authority: WO
Inventors: Sascha Dorner; Daniel Fahrner; Karl Jojo VIDIC; Jan WYSS
Original assignee: Linde Gmbh
Priority date: 2020-12-12
Filing date: 2021-11-16
Publication date: 2022-06-16
Also published as: DE102020007623A1

Abstract

The invention relates to a filter device (1) for a flow of a gas under high pressure, which has at least one inlet opening (2) and at least one outlet opening (4), which are fluidically connected to one another, wherein a filter element (8) is provided which is arranged such that the gas flows through the filter element when there is a gas flow from the inlet opening to the outlet opening; wherein the filter element comprises two gas-permeable and fluid-permeable planar electrodes (10, 12) and an electrically non-conductive planar filter non-woven material (14), wherein the electrodes are arranged running parallel to and at a distance from one another and the filter non-woven material is arranged between the electrodes; wherein the electrodes and the filter non-woven material are cast at respective edges (24, 26) in at least one electrically non-conductive support element (20, 22), wherein electrically conductive terminals (32) are provided on the electrodes. The invention further relates to a corresponding method and a use.

Description

description

Filter element for a flow of high pressure gas

The invention relates to a filter device for a stream of gas under high pressure, as well as a method and a use.

State of the art

In lubricated gas compressor systems, with which gases are compressed to high pressures of over 100 bar, significant concentrations of the lubricant in the clean gas flow can occur in the event of a fault. In this case, for example in the case of a piston compressor at a hydrogen filling station, if the separation capacity of the gas-cleaning system components is no longer sufficient, it can happen that the required degrees of purity (e.g. 5.0, 3.0 or SAE J-2719 and/or ISO/PDTS 14687-2) of the hydrogen (H ₂ ) are not met. In this operating case, the lubricant can continue to be carried over into those areas of the H ₂ filling station which are downstream of the source of contamination. This subsequently leads to contamination of the tank system on the vehicle being refueled with the undesired fluid. This also means that contaminated system components of the H ₂ filling station have to be subjected to a complex cleaning process in the event of a fault in order to continue to ensure proper operation. In addition, there is a significant risk of damage to the refueled fuel cell vehicle (eg contamination of the membrane system) due to contaminated hydrogen.

In the high-pressure hydrogen range, filter elements can be used to filter out solid particles and liquids. However, these are not able to clean the gas and at the same time carry out in situ measurements in order to qualitatively and/or quantitatively determine potential liquid contamination, in particular by ionic liquids or oils, of the incoming gas flow.

Disclosure of Invention This object is achieved by a filter device for a flow of a gas under high pressure, as well as a method and a use having the features of the independent claims. Dependent claims relate to preferred embodiments.

The filter device for a flow of a high-pressure gas has at least one inlet opening and at least one outlet opening which are fluidly connected to one another, there being provided a filter element which is arranged such that the gas flows through the filter element when it comes from the inlet opening flows to the outlet opening; wherein the filter element comprises two gas-permeable and liquid-permeable flat electrodes and an electrically non-conductive flat filter fleece, the electrodes being arranged at a distance parallel to one another and the filter fleece being arranged between the electrodes; wherein the electrodes and the filter fleece are cast into at least one electrically non-conductive support element at respective edges, wherein electrically conductive connections are provided on the electrodes.

The filter device according to the invention filters impurities, in particular liquids, from a gas flowing through the filter fleece, the impurities being separated or absorbed in the filter fleece. As a result, the impurities separated in the filter fleece lead to a change in the electrical properties (conductivity, permittivity) of the filter fleece. The detection of these changes is made possible by the electrodes provided on the filter device and the connections connected thereto. This detection can be done by applying a voltage between the electrodes. In particular, the filter fleece together with the impurities deposited therein forms a dielectric for the capacitor formed by the electrodes, so that the capacitance changes with increasing impurity.

By embedding or casting the filter fleece and the electrodes at the edges in support elements, a composite filter element is formed that has the mechanical stability required for high-pressure applications.

A gas is considered to be under high pressure if it has a pressure of at least 100 bar, preferably at least 300 bar, more preferably at least 500 bar, most preferably at least 800 bar. Irrespective of this, an upper limit is preferably around 1200 bar, more preferably around 1000 bar. The filter device is appropriately adapted to process or filter a gas stream that is under one of the specified pressures. For example, the gas may have a temperature ranging between -50°C and 80°C.

The gas to be filtered is preferably hydrogen gas, the pressure of which is in one of the aforementioned ranges and/or the temperature of which is in the aforementioned range. That is, the filter device is resistant to hydrogen embrittlement at these pressures and/or temperatures and has a high resistance to wear.

The term “area” is to be understood in such a way that the respective element (electrodes or filter fleece or filter element) extends essentially along a surface, with a thickness of the element orthogonal to the surface being small compared to the extent of the surface; e.g., the thickness is at most 1/10 of a maximum dimension of the face, measured along the face. As used herein, "substantially" is intended to refer to that thickness. The surface along which the respective element extends can, in principle, be of any shape and curvature (cf. Figure 1, in which elements in the shape of a cylinder jacket occur) does not have to be flat, i.e. "flat" does not mean "flat". " to understand. The edges are corresponding edges of the surface and extend in the thickness direction.

The filter fleece consists of a (non-conductive) open-pored fabric material, which preferably includes glass fibers, preferably with increased surface roughness. The filter fleece is gas-permeable and able to filter impurities, in particular liquids, from a gas flowing through. The thickness of the filter fleece is preferably matched to the distance between the electrodes, ie equal to this distance, so that the filter fleece is supported by the electrodes.

The electrodes are preferably designed as electrically conductive wires, an electrically conductive wire mesh or a perforated metal sheet. The electrodes are also preferably made of a metal. Preferably, the at least one support member is made of a material that includes a polymeric resin; more preferably the material is a polymeric resin. Polymer resins are useful because they are easy to process and, when cured, ensure a stable connection between the electrodes and the filter fleece.

The connections to the electrodes are preferably brought out through the at least one support element. This is advantageous because the connections and any further cables connected thereto are protected in this way and, in particular, are not located in the gas flow, ie cannot impede it and cannot be swept along by it.

The filter fleece is preferably able (i.e. is designed accordingly) to absorb ionic liquids, oils, in particular mineral oils, and/or hydrocarbon compounds in liquid form. The temperature at which the hydrocarbon compound and the oils are liquid corresponds here to the temperature of the gas to be filtered. For example, a temperature at which the hydrocarbon compound and oils are liquid may range between -50°C and 80°C. An example of ionic liquids are imidazolium derivatives dissolved in a quaternary ammonium compound. The detectability of oils is particularly improved when they are contaminated with electrically conductive substances.

The non-woven filter fabric preferably comprises glass fibers, with the proportion by weight of the glass fibers in the non-woven filter fabric preferably being at least 50 percent by weight, more preferably at least 75 percent by weight. Glass fibers are advantageous because they are suitable for high-pressure applications. In particular, they have high stability/strength, so that no fibers are entrained at high mass flows.

The filter device preferably comprises one or more metallic housing elements; wherein the filter element is attached to the one or more housing elements by means of the at least one support element; wherein preferably the at least one support element in the one or more Housing elements is cast. The stability can be further increased by metallic housing elements.

No other filter is preferably arranged between the inlet opening and the filter element. Another filter (apart from the filter element or filter fleece) between the inlet opening and the filter element is disadvantageous because it filters out impurities from the gas, which are then not separated in the filter fleece between the electrodes, so that the electrical properties of the filter element do not change or change to a lesser extent . As a result, contamination of the supplied gas cannot be detected or can be detected later.

Preferably, the electrodes and the filter fleece each have the shape of a cylinder jacket or of cylinder jacket sections; wherein preferably two support elements are provided, wherein one support element has the shape of a disk, in particular a circular disk, and the other support element has the shape of a ring, in particular a circular ring; with further preference, optionally, a housing base and a housing cover being provided as housing elements, with the housing base having the shape of a disk, in particular a circular disk, and the housing cover having the shape of a ring, in particular a circular ring, with the inlet opening passing through the opening of the Ring is formed, and wherein projections are provided on the outer edges of the housing base and the housing cover, which extend perpendicularly to the disc shape and the ring shape. This design enables a compact design that can be easily integrated into existing systems, which at the same time offers a large filter area.

The filter device preferably comprises a current sensor and/or a capacitance sensor which is connected to the connections to the electrodes and is set up to measure a current and/or a capacitance between the electrodes.

The method according to the invention for filtering a gas under high pressure comprises passing the gas through a filter device according to the invention; measuring a current and/or a capacitance between the electrodes of the filter device. In the method, an alternating voltage is preferably applied between the electrodes or to the electrodes when measuring the current and/or the capacitance.

The method preferably includes comparing the measured current and/or the measured capacitance with a predetermined current limit value or a predetermined capacitance limit value; interrupting the conduction of the gas through the filter device if the comparison establishes that the current limit value or the capacity limit value is exceeded.

Preferably the gas is a hydrogen gas at a pressure of at least 100 bar; preferably the pressure is in a range from 300 bar to 1200 bar, more preferably in a range from 500 bar to 1100 bar, most preferably in a range from 800 to 1000 bar.

The hydrogen gas is preferably passed through the filter device with a mass flow such that the mass flow in relation to an area of the filter element of the filter device is in the range from 0.01 g/s/cm ² to 3 g/s/cm ² , more preferably in the range of 0.02 g/s/cm ² to 2 g/s/cm ² . In particular, high mass flows of more than 0.5 g/s/cm ² are provided for in the process.

According to the use according to the invention, a filter device according to the invention is used for filtering a hydrogen gas which has a pressure of at least 100 bar; wherein the pressure is preferably in a range from 300 bar to 1200 bar, more preferably in a range from 500 bar to 1100 bar, most preferably in a range from 800 to 1000 bar, and/or wherein the hydrogen gas is preferably mixed with a Mass flow is passed through the filter device, so that the mass flow in relation to an area of the filter element of the filter device in the range of 0.01 g / s / cm ² to 3 g / s / cm ² , more preferably in the range of 0.02 g /s/cm ² to 2 g/s/cm ² . In particular, use for high mass flows of over 0.5 g/s/cm ² is intended.

The invention is further explained below with reference to the attached figures, which illustrate embodiments of the present invention. Brief description of the figures

Fig. 1 is a sectional view of a high pressure gas filter apparatus according to a preferred embodiment of the invention; and

FIG. 2 shows a flow chart of a preferred method according to the invention.

Detailed character description

FIG. 1 shows a sectional view of a filter device 1 for a gas under high pressure according to a preferred embodiment of the invention.

The filter device comprises a filter element 8, which has the shape of a cylinder jacket. The filter element 8 is formed by two electrodes 10, 12 and a filter fleece 14, each of which has the shape of a (circular) cylinder jacket, with the corresponding axes of symmetry coinciding. The two electrodes 10, 12 are arranged at a distance from one another, with the filter fleece 14 being arranged between the electrodes. The thickness of the filter fleece is preferably matched to the distance between the electrodes, ie equal to this distance, so that the filter fleece is supported laterally (in the embodiment shown in the radial direction) by the electrodes. The filter fleece consists of a (non-conductive) open-pored fabric material, which preferably includes glass fibers. The filter fleece is gas-permeable and able to filter impurities, in particular liquids, from a gas flowing through.

The electrodes 10, 12 can be formed, for example, by electrically conductive wires 16, 18, which run approximately spirally or form a wire grid or wire mesh with wires (not shown) running at least partially parallel to the axis of symmetry. The wires, in particular of the wire grid or wire mesh, are spaced apart from one another, passages being formed in the radial direction, so that the electrodes are permeable to gas and liquid. It is also possible to use perforated sheets as electrodes use, ie electrically conductive sheets that are provided with out reaching large and many holes.

At their edges 24, 26, the electrodes and the filter fleece are embedded or cast in support elements 20, 22. The edges are circular or annular due to the cylindrical shape of the electrodes and filter fleece. Upper edges 24 are cast into an upper support element 20 and lower edges 26 into a lower support element 22 . As used herein, the terms 'top'/'bottom' refer to the figure; the actual orientation of the filter device can of course be arbitrary. The support members are made of an electrically non-conductive material, preferably a polymeric resin. There is therefore no electrically conductive connection between the electrodes.

The support elements 20, 22 are also cast or embedded in housing elements 28, 30, namely a housing cover 28 and a housing base 30, with the upper support element 20 being cast in the housing cover 28 and the lower support element 22 in the housing base 30. The housing elements are preferably made of metal in order to ensure high stability.

The upper support element 20 has the shape of a circular ring or a circular disc with a central opening. The lower support element 22 has the shape of a circular disc. The shape of the housing elements here corresponds to the shape of the support elements, i.e. the housing cover 28 has the shape of a circular ring or a circular disk with a central opening which is aligned with the opening of the upper support element, and the housing base 30 has the shape of a circular disk. The axes of symmetry of the support elements and of the housing elements coincide and also coincide with the axis of symmetry of the filter device or the cylindrical jacket shape of the filter element. On the outer edges of the housing cover and housing base, projections 29, 31 are additionally provided, which extend in the axial direction (i.e. parallel to the axis of symmetry) and enclose the supporting elements 20, 22 at their edges.

Further housing elements can also be provided (not shown), in particular housing elements which connect the housing cover and the housing base to one another, for example struts running in the longitudinal direction. Furthermore, as housing element, a high-pressure-resistant outer housing can be provided (not shown), into which the filter device of the figure is inserted and in which the supply and discharge passages are provided, which are connected on the one hand to the inlet and outlet ports respectively.

Outlet opening are fluidically connected and on the other hand with (pipe) connections to further gas lines through which the gas to be filtered is supplied and discharged, are connected.

The openings in the upper support element 20 and in the housing cover 28 together form the inlet opening 2 of the filter device. The lower support element 22 closes off the filter device at the opposite end, so that a cylindrical cavity 6 is defined which is defined by the support elements and the filter element. Gas to be filtered flows through the inlet opening 2 into the cavity 6 and flows from there through the filter element 8, each indicated by arrows. The gas then exits the filter device through an outlet opening 4, which here has the shape of a cylinder jacket. Impurities are filtered out of the gas in the filter fleece 8 .

An outside diameter D of the filter element 8 is preferably in the range from 2 cm to 10 cm, in particular in the range from 2 cm to 5 cm. An overall length of the filter device 1 is preferably in the range from 4 cm to 20 cm, in particular in the range from 5 cm to 10 cm. Depending on the design or thickness of the support elements 20, 22 and the housing elements (housing cover 28, housing base 30), the length of the filter element is about 1 cm to 2 cm shorter than the overall length. These dimensions lead to a compact filter device that can be easily integrated into existing systems. At the same time, there is a large filter surface, so that high volume or mass flows are possible. A filter device with an outer diameter of about 3-4 cm and a total length of about 8-9 cm allows, for example, the filtration of hydrogen gas at about 1000 bar with up to 100 g/s (H ₂ mass flow).

Furthermore, connections 32 to the electrodes 10, 12 are provided, which are routed through the lower support element and the housing base in an electrically insulated manner. Insulation is to be provided here, in particular when leading through the metallic housing base, since the support elements are already made of a non-conductive material. With the terminals 32, the electrodes can be electrically be connected or be connected in a conductive manner to a preferably provided current and/or capacitance sensor 34 or current and/or capacitance measuring device.

An electrical voltage, preferably an alternating voltage, can be applied to the electrodes 10, 12 via the connections 32. The filter fleece 14 is non-conductive, i.e. an insulator, and (together with any gas flowing through the filter fleece) forms a dielectric between the two electrodes 10, 12. As soon as pure hydrogen enters the filter element and flows through the filter fleece, there is an extremely low electrical conductivity in the hydrogen-containing channels of the open-pored filter fleece between the electrodes. Since gaseous hydrogen is an electrical insulator, the currents I and capacitances C measured between the electrodes approach zero. As soon as liquid contamination of the incoming gas flow occurs, the porous filter mat is flooded with the two-phase mixture, with the liquid phase (contaminant) being separated in the porous channels of the fabric. After a retention time that depends on the loading of the gas flow and the flow rate, so much liquid has been separated in the filter fleece that the electrochemical mode of action of the dielectric is significantly influenced. Because of this, the measured values for current I and capacitance C also change, in particular the (relative) dielectric constant or permittivity of the dielectric increases with increasing contamination. If one of the two or both measured values exceeds a measured value threshold (current limit value and/or capacity limit value) adapted to the system requirement, an electrical signal can be forwarded to a system control and the supply of gas can be interrupted. Ultimately, this leads, for example, to a compressor system being switched off in order to prevent further liquid contamination of the system components downstream of the filter element.

FIG. 2 illustrates the flow of a preferred method of filtering a high pressure gas in accordance with the present invention using a filter apparatus such as that shown in FIG. 1 in accordance with the present invention. In step 52 gas is conducted through the filter device or the conduction of gas through the filter device is started, ie the gas is conducted into the inlet opening and discharged from the outlet opening. In step 54, a voltage, in particular an alternating voltage, is applied to the electrodes or the terminals connected to them. This can be done before or at the same time as the gas is fed in.

In step 56, a current between the electrodes is measured or determined, i.e. the amperage of the current is measured. The capacitance between the electrodes can also be determined from the current together with the applied voltage (taking into account the relative phase); the capacity is also measured.

In step 58 the measured current (more precisely its current intensity) is compared with a current limit value (more precisely current intensity limit value). As an alternative or in addition, the measured capacity can also be compared with a capacity limit value.

If the comparison establishes that the current limit value or the capacity limit value is exceeded, the supply of gas is interrupted in step 60 (e.g. by appropriately controlling the supplying parts of the system).

Clearly, these steps are not to be understood as consecutive steps, but are carried out continuously, in parallel, unless there is a connection between the steps that necessitates the execution of one step after another. The gas is therefore continuously fed in, the voltage is continuously applied, the current or the capacity is continuously measured and it is continuously compared on the basis of the current current value or the current capacity.

Claims

patent claims

1 . Filtering device (1) for a flow of a gas under high pressure, having at least one inlet opening (2) and at least one outlet opening (4) which are in fluid communication with each other, there being provided a filter element (8) arranged so that the gas flows through the filter element as it flows from the inlet opening to the outlet opening; wherein the filter element comprises two gas-permeable and liquid-permeable flat electrodes (10, 12) and an electrically non-conductive flat filter fleece (14), the electrodes being arranged at a distance parallel to one another and the filter fleece being arranged between the electrodes; the electrodes and the filter fleece being cast into at least one electrically non-conductive support element (20, 22) at respective edges (24, 26), with electrically conductive connections (32) being provided on the electrodes.

2. Filter device according to claim 1, wherein the at least one support element (20, 22) consists of a material comprising a polymer resin; the material preferably being a polymeric resin.

3. Filter device according to one of the preceding claims, wherein the connections (32) are led out to the electrodes through the at least one support element.

4. Filter device according to one of the preceding claims, wherein the filter fleece (14) is capable of absorbing ionic liquids, oils, in particular mineral oils, and/or hydrocarbon compounds in liquid form.

5. Filter device according to one of the preceding claims, wherein the filter fleece (14) comprises glass fibers, wherein a proportion by weight of the glass fibers in the filter fleece is preferably at least 50 percent by weight, more preferably at least 75 percent by weight.

6. Filter device according to one of the preceding claims, comprising one or more metallic housing elements (28, 30); wherein the filter element by means the at least one support member is attached to the one or more housing members; wherein preferably the at least one support element is cast into the one or more housing elements.

7. Filter device according to one of the preceding claims, wherein no other filter is arranged between the inlet opening and the filter element.

8. Filter device according to one of the preceding claims, wherein the electrodes and the filter fleece each have the shape of a cylinder jacket or cylinder jacket sections; wherein preferably two support elements are provided, wherein one support element has the shape of a disk, in particular a circular disk, and the other support element has the shape of a ring, in particular a circular ring; more preferably, if dependent on claim 6, a housing base (30) and a housing cover (28) are provided as housing elements, the housing base having the shape of a disc, in particular a circular disc, and the housing cover having the shape of a ring, in particular a circular ring , Having, wherein the inlet opening is formed by the opening of the ring, and wherein projections are provided on the outer edges of the housing base and the housing cover, which extend perpendicularly to the disc shape or to the ring shape.

9. Filter device according to one of the preceding claims, comprising a current sensor and/or a capacitance sensor (34) which is connected to the connections to the electrodes and is set up to measure a current and/or a capacitance between the electrodes.

A method of filtering a high pressure gas, comprising passing (52) the gas through a filter device according to any one of claims 1-9; measuring (56) a current and/or a capacitance between the electrodes of the filter device.

11 . Method according to claim 10, wherein an alternating voltage is applied between the electrodes when measuring the current and/or the capacitance (54). 14 The method according to any one of claims 10 or 11, comprising

comparing (58) the measured current and/or the measured capacitance with a predetermined current limit value and a predetermined capacitance limit value, respectively;

Interrupting (60) the conduction of the gas through the filter device if the comparison establishes that the current limit value or the capacity limit value is exceeded. A method according to any one of claims 10 to 12, wherein the gas is a hydrogen gas at a pressure of at least 100 bar; preferably the pressure is in a range from 300 bar to 1200 bar, more preferably in a range from 500 bar to 1100 bar, most preferably in a range from 800 to 1000 bar. The method according to claim 13, wherein the hydrogen gas is passed through the filter device with a mass flow such that the mass flow in relation to an area of the filter element of the filter device is in the range from 0.01 g/s/cm ² to 3 g/s/ cm ² , preferably in the range from 0.02 g/s/cm ² to 2 g/s/cm ² . Use of a filter device according to any one of claims 1-9 for filtering a hydrogen gas which has a pressure of at least 100 bar; wherein the pressure is preferably in a range from 300 bar to 1200 bar, more preferably in a range from 500 bar to 1100 bar, most preferably in a range from 800 to 1000 bar, and/or wherein the hydrogen gas is preferably mixed with a Mass flow is passed through the filter device, so that the mass flow in relation to an area of the filter element of the filter device in the range of 0.01 g / s / cm ² to 3 g / s / cm ² , preferably in the range of 0.02 g / s/cm ² to 2 g/s/cm ² .