Patent Application
20230044196
The present invention belongs to the field of high-purity gas preparation, in particular the preparation of high-purity hydrogen and/or oxygen, and relates to a device and method for producing high-purity hydrogen and oxygen by electrolysis of water.
In industry, there are many methods for the preparation of hydrogen, such as chemical hydrogen production methods including steam methane reforming and methanol reforming, and electrical methods for hydrogen production by electrolysis of water. The basic principle of electrolysis of water to produce hydrogen and oxygen is that water is converted into gaseous hydrogen and oxygen by direct current power. Based on operating temperature, electrolyzers are mainly divided into low-temperature electrolyzers and high-temperature electrolyzers; low-temperature electrolyzers further include alkaline electrolyzers and proton exchange membrane electrolyzers. These have become mature technologies used in commerce.
The semiconductor industry requires large amounts of high-purity gas; here, high-purity means that the impurity content of the required gas is less than a few ppb, Conventional methods for isolating impurities and purifying product gases include adsorption and cryogenic rectification separation under different temperature and pressure conditions. However, the above methods are not very effective at isolating argon in hydrogen and oxygen products.
When a semiconductor factory requires both high-purity oxygen and high-purity hydrogen, electrolyzing water to produce hydrogen and oxygen becomes a particularly suitable method. The impurities which have been the focus of attention in the prior art are mainly various organic substances, salt ions, nitrogen, carbon dioxide, carbon monoxide, hydrocarbons, and water vapor. U.S. Pat. No. 5,484,512 discloses a method and device for providing high-purity oxygen and high-purity hydrogen, including providing pure water to an electrolyzer, passing the generated oxygen and hydrogen through respective purifiers, and further purifying them by cooling, absorption and adsorption, etc. Pure water is prepared by using desalinated water or passing desalinated water through a degassing membrane to remove nitrogen.
The prior art does not pay attention to the presence of argon as an impurity in the hydrogen and oxygen produced by electrolysis of water, and therefore does not provide distinctive methods or ideas for reducing the content of argon. The hydrogen and oxygen prepared by methods in the prior art generally contain argon in a weight ratio of 70-100 ppb. In order to reduce the content of argon in the gas product to less than a few ppb, the present invention discloses a device for preparing high-purity hydrogen and/or oxygen by electrolysis of water, comprising an electrolyzer and a degasser for degassing desalinated water, the degasser being located upstream of the electrolyzer.
Further, the present invention comprises a desalination water treatment system located upstream of the degasser. The electrolyzer of the present invention comprises an alkaline electrolyzer, and the degasser is heated by a hot lye recirculation stream passing through a lye heat exchanger.
In another aspect, the present invention discloses a device for preparing high-purity hydrogen and/or oxygen by electrolysis of water, comprising, connected in sequence, a desalination water treatment system, optionally a desalinated water storage tank, a degasser feed water pump, a desalinated and degassed water heat exchanger, a degasser for degassing desalinated water, an electrolyzer feed water pump and an electrolyzer. The electrolyzer is an alkaline electrolyzer, and comprises an electrolytic cell, an anode lye separator, a cathode lye separator and a lye cooler. The electrolyzer may further comprise a lye heat exchanger, and a hot lye recirculation stream flowing therethrough supplies required heat to the degasser.
In the present invention, the desalinated water has an argon content of less than 10 ppb (by weight proportion) after being degassed by the degasser; the high-purity hydrogen and/or oxygen produced has an argon content of less than 5 ppb (by weight proportion).
In the present invention, O2 generated by the anode of the electrolyzer and H2 generated by the cathode can be further purified.
In another aspect, the present invention discloses a method for preparing high-purity hydrogen and/or oxygen by electrolysis of water, comprising a step of degassing desalinated water in a degasser, to obtain electrolyzer feed water with an argon content of less than 10 ppb.
In another aspect, the method disclosed in the present invention specifically comprises the following steps:
a) degassing desalinated water in a degasser to obtain desalinated and degassed water;
b) pressurizing the desalinated and degassed water with an electrolyzer feed water pump to obtain electrolyzer feed water, and passing this into an anode lye separator and a cathode lye separator, wherein a portion of lye in the separators is cooled in a lye cooler as a hot lye recirculation stream and then passed into an electrolytic cell in communication with a DC power supply;
and c), further purifying O2 separated out in the anode lye separator and H2 separated out in the cathode lye separator to obtain a product.
Compared with the prior art, the technical solution provided in the present invention has the following advantages:
A simple, low-cost degasser is used to reduce the content of various gases, including argon, in the electrolyzer feed water, thereby reducing the content of these impurities in the O2 and H2 products resulting from electrolysis.
The hot lye recirculation stream passing through the lye heat exchanger is used to heat the degasser, thus further saving energy.
Since the gas impurities in the feed water of the electrolyzer have been removed in advance, the gases obtained at the two electrodes after electrolysis contains fewer types of impurities, so the subsequent purification process is simpler, and the purification equipment is cheaper.
Further understanding of the advantages and spirit of the present invention can be gained through the following detailed description of the invention and the accompanying drawings.
In the figure: 100—electrolyzer; 1—alkaline electrolytic cell; 2—cathode lye separator; 3—anode lye separator; 4—lye cooler; 5—lye pump; 6—desalination water treatment system; 7—desalinated water storage tank; 8—electrolyzer feed water pump; 10—hot lye recirculation stream; 11—cold lye recirculation stream; 12—lye oxygen mixed stream; 13—lye hydrogen mixed stream; 14—hydrogen; 15—Oxygen; 20—raw water; 21—desalinated water; 22—electrolyzer feed water; 30—cooling water; 50—degasser feed water pump; 51—desalinated and degassed water heat exchanger; 52—degasser; 53—heater; 60—cold desalinated input water; 61—hot desalinated output water; 62—gas discharge pipeline; 63—hot desalinated and degassed water; 64—cold desalinated and degassed water; 70—lye heat exchanger; 71—vacuum pump.
Specific embodiments of the present invention are explained in detail below in conjunction with the accompanying drawings. However, the present invention should be understood to not be limited to embodiments such as those described below, and the technical concept of the present invention may be implemented in combination with other well-known technologies or other technologies having the same function as those well-known technologies.
In the explanation of particular embodiments below, in order to clearly demonstrate the structure and manner of operation of the present invention, many directional words will be used for description, but words such as “front”, “rear”, “left”, “right”, “outer”, “inner”, “outward”, “inward”, “axial” and “radial” should be understood as being terms of convenience rather than defining words.
In the explanation of particular embodiments below, it must be understood that orientational or positional relationships indicated by terms such as “length”, “width”, “up”, “down”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner” and “outer” are based on the orientational or positional relationships shown in the drawings, and are merely intended to facilitate and simplify the description of the present invention, without indicating or implying that the apparatus or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.
The terms “upstream” and “downstream” indicate a relative positional relationship between a number of steps, devices or a number of device parts. In the present invention, a step that is performed first or a device that is used first according to the flow of a process is positioned upstream of a subsequent step or device.
In the present invention, unless otherwise clearly specified and defined, terms such as “installed”, “connected together”, “connected” and “fixed” should be understood in a broad sense, e.g. may mean connected in a fixed manner, but may also mean removably connected, or forming a single piece; may mean mechanically connected, but may also mean electrically connected; may mean directly connected together, but may also mean connected indirectly via an intermediate medium; and may mean internal communication between two elements, or an interactive relationship between two elements. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.
Unless clearly indicated otherwise, each aspect or embodiment defined here can be combined with any other aspect(s) or embodiment(s). In particular, any preferred or advantageous feature indicated can be combined with any other preferred or advantageous feature indicated.
The electrolyzer is a device that is connected to a DC power supply and electrolyzes water to produce O2 and H2. Various electrolyzers, including alkaline electrolyzers, acidic electrolyzers, and proton exchange membrane electrolyzers, are suitable for use in the present invention. Taking an alkaline electrolyzer as an example, a 10%-30% KOH aqueous solution is used as an electrolyte, and the following reactions occur:
At the anode: 4OH—→O2+2H2O+4e−;
At the cathode: 4H2O+4e−→4OH−+2H2
Overall reaction: 2H2O→2H2+O2
From a structural point of view, an alkaline electrolyzer comprises an electrolytic is cell with electrodes inserted therein; gases generated near the two electrodes are passed separately into a cathode lye separator and an anode lye separator through pipelines. H2 and O2 leave from top ends of the separators separately and enter the next purification step; fresh electrolyzer feed water is added to the two separators separately, leaves from the bottom of the separators, is cooled by a lye cooler, and then flows back to the electrolytic cell.
The electrolyzer feed water is water for replenishment that is passed into the electrolyzer. In the prior art, desalinated water is generally used; in the present invention, desalinated water is further degassed in a degasser to obtain electrolyzer feed water.
The desalination water treatment system is a system that can remove strong electrolytes and/or some of the weak electrolytes in raw water, such as tap water. Generally, one of distillation, ion exchange and electrodialysis, etc. is used, or a combination of more than one of such methods is used, Desalinated water suitable for the semiconductor industry preferably has a resistance equal to or higher than 18 MΩ·cm (25° C.).
The working principle of the degasser is based on the fact that the solubility of gas in water decreases as the water temperature increases and approaches the saturation temperature. The structure of the degasser can take many forms; one of the more common forms is a column-like structure, with multiple plates contained in the column. The stream to be degassed is sprayed downward from the top of the column; washing water is heated to saturation temperature and fed into the column from the bottom thereof, The arrangement of the spraying and the plates can increase the contact area between the stream to be degassed and the washing water, thus increasing the efficiency of degassing. The stream to be degassed reaches saturation temperature through contact and heat exchange with the washing water, the gas dissolved therein is released and discharged from the degasser through a gas discharge port, and the degassed stream is converged and outputted at the bottom of the column. The degasser can effectively remove most of the gas dissolved in water, including O2, N2, CO2 and Ar, etc., to reduce the contents thereof to the level of a few ppb.
Particular embodiments of the present invention e explained in detail below in conjunction with
Since the electrolyzer feed water 22 in
Unless stated otherwise, qualifiers similar to “first” and “second” appearing herein do not indicate a definition of chronological order, quantity or importance, but are merely intended to distinguish one technical feature in this technical solution from another technical feature, Similarly, qualifiers similar to “a” appearing herein do not indicate a definition of quantity, but describe a technical feature that has not appeared in the preceding text. Similarly, modifiers similar to “about” and “approximately” appearing in front of numerals herein generally include the number itself, and the specific meaning thereof should be understood in conjunction with the meaning of the context. Similarly, unless modified by a specific quantity measure word, nouns herein should be regarded as including both singular and plural forms, i.e. the technical solution may include a single one of the technical feature concerned, but may also include a plurality of the technical feature.
The above are merely preferred particular embodiments of the present invention, which are merely intended to illustrate the technical solution of the present invention without limiting the present invention. All technical solutions obtainable by those skilled in the art according to the concept of the present invention by logical analysis, reasoning or limited experiment should be included in the scope of the present invention,
Although the content of the present invention has been described in detail by means of the preferred embodiments above, it should be understood that the above description should not be construed as limiting the present invention. Various amendments and substitutions to the present invention will be apparent after perusal of the above content by those skilled in the art. Thus, the scope of protection of the present invention should be defined by the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201911355604.7 | Dec 2019 | CN | national |
This application is a 371 of International Application No. PCT/CN2020/137965, filed Dec. 21, 2020, which claims priority to Chinese Patent Application No. 201911355604.7, filed Dec. 25, 2019, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2020/137965 | 12/21/2020 | WO |
