The present invention relates to air separation units and more particularly to devices producing oxygen enriched air or the like.
Oxygen (O2) enriched air is used for advanced combustion, coal gasification, industrial processes, and medical applications.
Coal Gasification Application: Coal is a plentiful natural resource in the U.S. but has been underused due to pollution resulting from conventional combustion. Gasification, as opposed to conventional combustion, is the most thermally efficient and cleanest way to convert the energy content of coal into electricity, hydrogen, clean fuels, and value-added chemicals. Gasification plants can run more efficiently and be configured to more economically capture Carmon dioxide (CO2) if the oxidant is oxygen rather than air. The combustion of fossil fuels in nearly pure O2, rather than air, can simplify CO2 capture in fossil fuel power plants. When pure or enriched O2 stream is used in a power plant, the volume of flue gas can be reduced by 75% compared with air-fired combustion. The lower off-gas volume can not only reduce the removal cost of pollutants but also reduce NOx production due to reduced nitrogen content. Gasification plant integrators seek an air separation unit (ASU) that would produce concentrated O2 at very low cost.
On-site oxygen production for coal gasification conventionally uses cryogenic air separation technology. The cryogenic ASU in a conventional gasification plant typically accounts for 12 to 15% of the overall capital cost of the plant, and requires a large parasitic power load primarily to operate gas compressors. Cryogenic ASU is cost effective only in large systems. Alternative air separation technologies include permeation-selective membranes and pressure swing-absorption (PSA). Such systems with limited capacity are now available commercially. While the membrane and PSA systems show cost advantages over cryogenic ASU in smaller installations, more effective and robust components must be development before deployment. Limitations and high cost of existing cryogenic, membrane, and PSA technologies provides an impetus for development of advanced air separation technology for generation of commercial-scale quantities of oxygen at significantly lower cost while being more compact and conducive to modular configuration for integration with smaller plants having 1 to 5 MW of total power capacity. The lack of suitable technology impedes a wide-spread adoption of O2-based combustion.
Medical Applications: The primary factors fueling global demand for portable O2 concentrators are an increasing prevalence of chronic obstructive pulmonary diseases, growing consumer awareness for oxygen therapy devices, a changing consumer lifestyle, adoption of new technologies, increased government expenditure, and a rise in investment by manufacturing companies towards the production of homecare products. O2 concentrators are used by patients requiring supplemental oxygen for pulmonary disorders such as bronchitis, emphysema, lung cancer, and acute pneumonia. O2 concentrators can be efficiently used at home as well as clinical settings to support the user's oxygen needs. Market growth is driven by the popularity and high demand for oxygen concentrators, due to their ease of use. Thus, many players in this market focus on incorporating significant changes in product design to suit patients' routines.
For the medical portable units, the liquid O2 and cryogenic approaches are inappropriate, thus, membrane and PSA systems are used. Due to moving/high-pressure components, such systems are very costly, typically $1,200 per unit, a required significant operating power, and make noise.
Prospects for Magnetic Air Separation: Oxygen is strongly paramagnetic while other constituents of air, namely nitrogen, carbon dioxide, and water vapor are diamagnetic, as seen in
Increased oxygen concentration near poles of strong magnets was observed over a century ago. This suggested that magnetic forces could be utilized for oxygen separation from air. In 1946, magnetic separation technique was employed in an oxygen analyzer (see, e.g., L. Pauling, R. E. Wood, and J. H. Sturdivant, “An Instrument for Determining of Partial Pressure of Oxygen in a Gas”, J. Am. Chem. Soc, Vol. 68, p. 795, 1946). Prospects for magnetic oxygen separation with concentrations and flow rates suitable for medical and industrial uses has been investigated by many but no practical devices were introduced. This is in-part due to technical challenges including diffusion, viscous shear, local turbulence, and remixing of separated species.
Asako showed that magnetic separation of oxygen is possible, but the achievable concentration he predicted using computational models was low (few percent) due to remixing by diffusion and flow dynamic effects. (see, e.g., Y. Asako, in: Proceedings of the ASME Heat Transfer Division-2004, vol. 375, 2004, p. 281). Recent experiments using permanent magnets demonstrated 0.65% oxygen enrichment of air in a single large channel (see, e.g., J. Cai, at al., “Study on oxygen enrichment from air by application of the gradient magnetic field,” J. of magnetism and magnetic materials, 230, 2008, pp 171-181).
The technical challenges including diffusion, viscous shear, local turbulence, and remixing of separated species separation process are overcome by staged magnetic separation of a flow in microchannels in accordance with the subject invention.
This invention is for an innovative magnetic air separator (MAS) for delivering oxygen-enriched air or near-pure oxygen to applications such as gasification plants, fossil fuel power plans, industrial processes, and medical; uses.
In the MAS of the subject invention, input air is drawn into a large array of microchannels immersed in magnetic field with strong ∇B2 (=2.B. ∇B) value. Magnetic forces transport O2 molecules with the microchannel flow generally in the direction transverse to the flow, thus forming enriched and depleted streams in each microchannel. Such streams are then physically separated and subsequently combined with like streams from other microchannels according to their level of O2 enrichment or depletion. Highly enriched streams are repeatedly subjected to the magnetic separation process until the targeted level of O2 concentration is reached in selected streams. Partially enriched streams are recycled and fed back into the process feedstock air, while depleted streams are vented from the process.
MAS attains high O2 concentration by repeating the separation process (aka staging). In particular, enriched streams from upstream microchannels are combined and injected into downstream microchannels for further separation. Similarly, lean streams from upstream microchannels may be combined and injected into downstream microchannels for further separation and O2 recovery. Highly depleted streams may be vented from the process. Slightly depleted streams may be fed back and combined with the feedstock.
The technical challenges encountered in prior art including diffusion, viscous shear, local turbulence, and remixing of separated species separation process are overcome by staged magnetic separation of a flow in microchannels.
In one embodiment of the subject invention, air flows inside the microchannels, while the paramagnetic O2 molecules drift toward the side of the microchannel with stronger magnetic field. Other air constituents (e.g., nitrogen, carbon dioxide, and water vapor) are only slightly diamagnetic and, therefore, are not significantly affected by the magnetic field. However, the resulting increase in partial pressure of oxygen along one microchannel wall causes the weakly diamagnetic air constituents to be driven to the other side of the microchannel. Oxygen enrichment limitations of a single stage separator are overcome by staged separation whereby oxygene enrichment is improved step-wise in downstream stages.
Accordingly, it is an object of the present invention to provide an MCR that is relatively simple and scalable in size. The key advantage of the innovative MAS is significantly lower capital and operating costs compared to existing air separation technology. Another advantage is the scalability of the technology from large systems for gasification plans to small portable devices for use in medical oxygen therapy. In particular, the innovative MAS has no moving parts except for the input air blower. The blower is also the only power consuming element of the innovative MAS. The required steady state magnetic field is conveniently produced by permanent magnets and requires no energy input. The simple construction of the innovative MAS requires very little maintenance.
Injection of highly concentrated O2 inexpensively produced by the innovative MAS enables much more economical gasification and it offers to stimulate wide adoption of the process. The resulting increased use of coal would lower energy costs and lessen country's dependence on foreign oil. Other commercial applications include a point-of-use oxygen generators for laboratories, manufacturing processes, and health care.
Other aspects and features of the present invention, as defined solely by the claims, will become apparent to those ordinarily skilled in the art upon review of the following non-limited detailed description of the invention in conjunction with the accompanying figures.
Selected embodiments of the present invention will now be explained with reference to drawings. In the drawings, identical components are provided with identical reference symbols in one or more of the figures. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are merely exemplary in nature and are in no way intended to limit the invention, its application, or uses.
Referring now to
Referring now to
The microchannel array 270 comprises a plurality of microchannels 222 immersed in the magnetic field with high ∇B2 produced by the magnet structure 216. Referring now to
Referring now to
In operation, the blower 102 in
Within the air separator 200, an air stream 236 (
In the process, a multitude of air streams may be formed that may be generally classified as “highly enriched” (with oxygen concentration significantly above the input air stream 106), “partially enriched” (with oxygen concentration slightly above the input air stream 106), “partially depleted” (with oxygen concentration slightly below the input air stream 106), and “highly depleted” (with oxygen concentration significantly below the input air stream 106). The highly enriched air stream 108 (
The exemplary map of the staging process and flow separation starting with a single microstream in
The input air stream 106 may be at ambient temperature and pressure, or at a sub-ambient pressure (including a near vacuum), or at a sub-ambient temperature (including a near cryogenic), or a combination of sub-ambient pressure and sub-ambient temperature. The sub-ambient conditions are deemed to reduce deleterious remixing and improve separation performance. This may be in-part due to the increased mean-free-path of the air molecules.
The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.
Moreover, terms that are expressed as “means-plus function” in the claims should include any structure that can be utilized to carry out the function of that part of the present invention. In addition, the term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function.
The term “suitable”, as used herein, means having characteristics that are sufficient to produce a desired result. Suitability for the intended purpose can be determined by one of ordinary skill in the art using only routine experimentation.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” and “includes” and/or “including” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.
This application claims priority from the U.S. provisional patent application U.S. Ser. No. 63/103,639, filed on Aug. 14, 2020 and entitled “Magnetic Air Separator”, which is hereby incorporated by reference in its entirety.
This invention was reduced to hardware practice with U.S. Government support under the U.S. Department of Energy Grant No. DE-SC0019663. The U.S. Government may have certain rights in this invention.