Device and method for processing gases containing helium and hydrogen

Abstract

The invention relates to a device for processing gases containing helium and hydrogen, comprising - a stacked gas separation device (2) which comprises a plurality of proton-permeable membranes (13) and which is designed as an electrochemical hydrogen pump provided for separating helium from a gas mixture, - a likewise stacked fuel cell (6) which is connected to the gas separation device (2), - a gas treatment system (10) which is designed to separate gas containing helium and hydrogen and which is electrically connected to the fuel cell (6) and fluidically connected to the gas separation device (2).

Description

[0001] Device and method for processing gases containing helium and hydrogen

[0002] The invention relates to a method for processing gas mixtures containing helium and hydrogen. The invention further relates to a device for carrying out such a method.

[0003] US Patent 2005 / 0217479 A1 deals with the separation of helium from a gas stream. It is assumed that a raw gas stream contains a small proportion of helium. In addition to processing steps such as condensation, distillation, and absorption, a separation device containing a polymer membrane is proposed for the separation of helium.

[0004] A device described in CN 115140718 A, intended for helium extraction, operates with an electrochemical hydrogen pump. Compared to cryogenic distillation, this is said to significantly reduce energy consumption.

[0005] WO 2016 / 033447 A1 concerns a process for drying a hydrogen gas mixture. In this process, a hydrogen gas mixture stream is fed through an electrochemical hydrogen compressor or electrolyzer. The hydrogen gas mixture stream is then passed through a bed of adsorbent.

[0006] Aspects of helium recovery in connection with ammonia production are addressed in documents WO 2020 / 070292 A1 and AT 305313 B. In the latter case, helium is separated from a gas mixture after other gases, including argon and methane, have already been separated. The invention is based on the objective of further developing methods for processing gases containing helium and hydrogen, in particular natural gas, compared to the prior art, with the aim of achieving advantageous combinations of material and / or energy flows.

[0007] This problem is solved according to the invention by a device designed for processing gases containing helium and hydrogen, having the features of claim 1. Likewise, the problem is solved by a method designed according to claim 6 for processing gases containing helium and hydrogen. The embodiments and advantages of the invention explained below in connection with the gas processing method also apply mutatis mutandis to the gas processing device and vice versa.

[0008] The device according to the application comprises a stacked gas separation device having a plurality of proton-permeable membranes, which is designed as an electrochemical hydrogen pump for separating helium from a hydrogen-containing gas mixture, in particular natural gas. The device according to the application further comprises a fuel cell, also stacked, which is connected to the gas separation device. The fuel cell utilizes gaseous hydrogen from the gas separation device. Electrical energy generated in the fuel cell is used in a gas processing plant, in particular a natural gas processing plant, attributable to the device according to the application, from which the gas mixture to be separated, containing helium and hydrogen, originates.

[0009] The gas mixture supplied to the gas separation device is primarily boil-off gas (boil-off = evaporation loss), which has been separated from natural gas. This separation is achieved, for example, by cryogenically cooling the natural gas. The energy required to separate the boil-off gas, which is richer in hydrogen and helium compared to natural gas, can be supplied by other sources, particularly a portion of the gas stream separated from the natural gas or an external energy source, if it is not already supplied by electricity from the fuel cell. The energy needed to separate the boil-off gas is primarily required to operate a compressor in a refrigeration unit.

[0010] The patent application process for processing gases containing helium and hydrogen generally comprises the following steps:

[0011] - Hydrogen and helium are separated from a gas mixture,

[0012] - The hydrogen-helium mixture is separated into a hydrogen-rich and a helium-rich fraction using an electrochemical, stacked pump.

[0013] - the hydrogen-rich portion is at least partially consumed in a fuel cell,

[0014] - the helium-rich portion is diverted for separate use,

[0015] - The electrical energy generated in the fuel cell is used for the separation of hydrogen and helium from the gas mixture mentioned in the first point, as well as for the operation of the electrochemical pump.

[0016] According to one possible design, the gas separation device and the fuel cell are constructed as separate stacks. This means that the hydrogen produced in the stacked electrochemical pump is extracted from this pump and fed to the similarly stacked fuel cell.

[0017] Alternatively, the gas separation device and the fuel cell are combined in a single cell stack. In this case, the hydrogen-helium mixture is separated into a hydrogen-rich and a helium-rich fraction by electrochemical pumping within a single cell stack, while the hydrogen-rich fraction produced by electrochemical pumping is simultaneously used to generate electricity via the fuel cell within the same cell stack. Pumping and fuel cell components can be stacked alternately within the multifunctional cell stack. A stacked structure designed as a multi-membrane cell, combining the functions of a hydrogen pump and a fuel cell, can have the following layered structure:

[0018] - A metallic, electrically conductive plate as the first layer. This plate has designated points where a helium-hydrogen mixture is introduced or purified helium is extracted.

[0019] - An electrode for hydrogen oxidation

[0020] - A membrane for proton transport

[0021] - An electrode for hydrogen oxidation

[0022] - A perforated, electrically conductive metallic plate that is permeable to gaseous hydrogen,

[0023] - An electrode for hydrogen reduction

[0024] - A membrane for proton transport

[0025] - An electrode for oxygen reduction

[0026] - An electrically conductive metallic plate as a counterpart to the first layer. Air can be introduced at this plate.

[0027] Overall, the device as applied for enables particularly energy-efficient cleaning of helium, which is present in a helium-hydrogen mixture, with aging of the cleaning system playing practically no role.

[0028] Two exemplary embodiments of the invention are explained in more detail below with reference to a drawing. This drawing shows:

[0029] Fig. 1 shows a block diagram of a plant for separating helium from natural gas, Fig. 2 shows a partial symbolic representation of a cell stack of another plant for separating helium from natural gas.

[0030] Fig. 3 shows the arrangement according to Fig. 2 in a more realistic representation.

[0031] Unless otherwise stated, the following explanations refer to both embodiments. Corresponding or essentially equivalent parts are marked with the same reference numerals in all figures.

[0032] A gas processing plant 1 is part of a process plant designated as 11. Plant 11 comprises a natural gas upgrading plant 10, from which a boil-off gas Bog, containing mainly hydrogen and helium, is derived. The separation of the boil-off gas Bog from the main components of the natural gas is carried out by cryogenic processes. In this process, purified natural gas is cooled to a temperature of approximately -162°C.

[0033] The boil-off gas Bog reaches the gas processing plant 1 via a gas supply line 3, which is connected to a gas separation device 2 belonging to the gas processing plant 1. The gas separation device 2 comprises a first cell stack, which is designed as an electrochemical hydrogen pump. The hydrogen-rich gas obtained by this pump is fed via a hydrogen line 4 to a fuel cell 6, which is designed as the second cell stack of the gas processing plant 1. Gaseous helium obtained by the pump 2 is discharged from the gas separation device 2 via a helium line 5. The helium (He) can be used in its present purity or subjected to further purification steps not shown.

[0034] Fuel cell 6 is shown with an air supply (LZ). It is also possible to operate fuel cell 6 with a gas richer in oxygen than air, particularly pure oxygen. A line for a heat transfer fluid, used to regulate the temperature of fuel cell 6, is designated 7. Once the operating temperature of fuel cell 6 is reached, heat is dissipated via line 7. This heat can be used to heat the gas separation device 2. During normal operation, the gas separation device 2 is heated and the fuel cell 6 is cooled. Heating of the fuel cell 6 is also possible during the start-up phase.

[0035] Water produced in the fuel cell 6 can be discharged via a line 8. The water discharged through line 8 can be used, in particular, in the gas separation device 2. This prevents the introduction of foreign substances or pollutants. Power lines connected to the fuel cell 6 are designated 9. A first power line 9 supplies the gas separation device 2 with electrical energy, while a second power line 9 is provided for the energy supply of the gas processing plant 10, which in this case is designed as a natural gas processing plant. Any additional energy sources that enable the operation of the gas separation device 2 and the gas processing plant 10 are not shown.

[0036] In the embodiment shown in Fig. 1, the gas separation device 2 and the fuel cell 6 are arranged as separate cell stacks, i.e., stacks 2, 6. The stacks 2, 6 can, for example, be housed in a common casing or in separate casings.

[0037] In contrast, in the embodiment shown in Figures 2 and 3, the functions of the electrochemical hydrogen pump 2, used for helium separation, and the fuel cell 6 are combined in a single cell stack 12. As can be seen in Figures 2 and 3, the electrochemical pump 2 comprises pump membranes 13, which are permeable to protons. The pump membranes 13 do not move for pumping purposes. Instead, protons migrating through the pump membrane 13 react with electrons to form gaseous hydrogen, which is thus separated from the hydrogen-helium mixture. Fuel cell membranes 14, which are also contained in the combined cell stack 12, are likewise designed as proton-permeable membranes. Furthermore, fluid-permeable cell internals 15 and 16 exist, which functionally represent fuel cell components and pump components, respectively, and thus components of electrochemical cells.Fluids flowing in the cells of the cell stack 12 are indicated by curved lines in Fig. 3.

[0038] The bipolar plates designated 17, which are further components of the combined cell stack 12, are provided with openings 18 through which media, in particular air and purified helium, can flow. In the embodiment according to Figures 2 and 3, as in the embodiment according to Figure 1, there is a line 5 connected to the stack 12 through which purified helium is discharged. Regarding the use of the electric current generated in the stack 12 or in the separate fuel cell 6, there are also no fundamental differences between the embodiment according to Figures 2 and 3 and the embodiment according to Figure 1.

[0039] List of reference signs

[0040] 1 Gas processing plant

[0041] 2 Gas separation device, first cell stack, pump

[0042] 3 Gas supply line for boil-off gas

[0043] 4 hydrogen pipeline

[0044] 5 Helium conduit

[0045] 6 Fuel cell, second cell stack

[0046] 7. Heat transfer fluid line

[0047] 8 Water pipe

[0048] 9 power line

[0049] 10 Gas processing plant, natural gas processing plant

[0050] 11 process engineering plant

[0051] 12 combined cell stacks

[0052] 13 Pump diaphragm

[0053] 14 Fuel cell membrane

[0054] 15 cell components, fuel cell

[0055] 16 cell components, electrochemical pump

[0056] 17 Bipolar plate

[0057] 18 Opening in the bipolar plate

[0058] Bog Boil-off Gas

[0059] The helium

[0060] LZ Air Supply

Claims

Patent claims 1. Device for processing gases containing helium and hydrogen, comprising - a stacked gas separation device (2) comprising a plurality of proton-permeable membranes (13), which is designed as an electrochemical hydrogen pump intended for separating helium from a gas mixture, - a fuel cell, also stacked, which is connected to the gas separation device, - a gas processing plant (10) designed to separate gas containing helium and hydrogen, which is electrically connected to the fuel cell (6) and fluidically connected to the gas separation device (2).

2. Device according to claim 1, characterized in that the gas processing plant (10) is a natural gas processing plant.

3. Device according to claim 2, characterized in that the natural gas processing plant (10) is designed for deep-freezing natural gas.

4. Device according to one of claims 1 to 3, characterized in that the gas separation device (2) and the fuel cell (6) are constructed as separate stacks.

5. Device according to one of claims 1 to 3, characterized in that the gas separation device (2) and the fuel cell (6) are combined in the form of a single cell stack (12).

6. Method for processing gases containing helium and hydrogen, wherein - hydrogen and helium are separated from a gas mixture, - the hydrogen-helium mixture is separated into a hydrogen-rich and a helium-rich fraction using an electrochemical, stacked pump (2), - the hydrogen-rich fraction in a fuel cell (6) is consumed, - the helium-rich portion is derived, - the electrical energy generated in the fuel cell (6) is used for the aforementioned separation of hydrogen and helium from the gas mixture and for the operation of the electrochemical pump (2).

7. Method according to claim 6, characterized in that the separation of hydrogen and helium from the gas mixture is carried out by deep cooling.

8. Method according to claim 6 or 7, characterized in that the hydrogen obtained in the stacked pump (2) is discharged from the pump (2) and supplied to the fuel cell (6), which is also stacked.

9. Method according to claim 6 or 7, characterized in that in a single cell stack (12) both the separation of the hydrogen-helium mixture into a hydrogen-rich and a helium-rich fraction is carried out by electrochemical pumping and the hydrogen-rich fraction thereby produced is used for electricity generation in the fuel cell (6) also realized by the cell stack (12).

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