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  Integration of igcc plant with superconducting power islandUSPTO Application #: 20070240451Title: Integration of igcc plant with superconducting power island Abstract: A cooling system for high temperature superconductor equipment comprising a cryocooler in heat exchange relationship with the high temperature superconductor equipment, and an air separation unit in heat exchange relationship with the cryocooler, the system arranged such that heat from the high temperature superconductor equipment is rejected to said air separation unit via the cryocooler. (end of abstract)
Agent: Nixon & Vanderhye P.C. - Arlington, VA, US Inventors: James Michael Fogarty, Albert Eugene Steinbach, James William Bray, John Arthur Urbahn, Richard Anthony Depuy USPTO Applicaton #: 20070240451 - Class: 062643000 (USPTO) Related Patent Categories: Refrigeration, Cryogenic Treatment Of Gas Or Gas Mixture, Separation Of Gas Mixture, Air, Distillation The Patent Description & Claims data below is from USPTO Patent Application 20070240451. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0002] This invention relates generally to the cooling of equipment utilizing superconductors and more specifically, to the linking of a cyrocooler for high temperature superconductors with an air separation unit in a power generation plant. [0003] One of the fundamental problems presented by various equipment that utilize superconductors is that the superconductors must be kept within a strict cryogenic temperature range so that the superconductors remain in a superconducting state. If, for example, the temperature is increased above the critical range even briefly, heat is generated within the superconducting wire that could cause further increases in temperature and perhaps lead to equipment failure. [0004] Cryocoolers capable of cooling at temperatures between 4.2 K and 77 K have long been available. However, it is insufficient to simply achieve the operating temperature range. The cryocooler must also be capable of removing heat for a given application (its cooling capacity in watts). In this regard, removing 10 watts at 30 K is much easier than removing 500 watts at the same temperature. Moreover, depending on the thermodynamic cycle being used, a 500 watt heat load could be merely difficult or practically impossible to remove. [0005] Users of power equipment expect that equipment to be extremely reliable. Typical allowances for unreliability for a complete turbine-generator limit the generator to only eight hours downtime each year. Each component within the generator must be even more reliable so that the entire generator achieves the stated goal. As applied to a cryocooler, the reliability budget for the equipment forces the use of redundant systems and equipment that allows online maintenance to avoid unnecessary downtime. As a result, reliability brings both complexity and cost to the cryocooler. [0006] It is now generally known that superconducting equipment can be used in power stations. The equipment presently includes power cables, transformers, generators, fault current limiters and the like. Given that each of these components employs superconducting materials at some cryogenic temperature, and that production of coolants at cryogenic temperatures can be expensive and perhaps unreliable, a means is desired whereby cooling capacity at temperatures between, for example, liquid helium and liquid nitrogen is readily available at an economical cost. BRIEF DESCRIPTION OF THE INVENTION [0007] In an exemplary embodiment of this invention, a cryocooler for high temperature superconductors (HTS) is used that links into the basic process for creating relatively pure oxygen in an integrated gasification combined cycle (IGCC) power plant. [0008] Coal gasification processes convert solid coal into synthetic gas, primarily CO and H.sub.2. Typically, O.sub.2 is used as the oxidizing medium. In an 1GCC plant, a cryogenic air separation unit (ASU) is often used to provide pure oxygen to the gasification reactor, often using or supplemented by, post-compression air bleed from the gas turbine. The ASU typically produces nitrogen and oxygen in the range of 63-90 K, depending on the point within the cycle being considered, and at mass flow rates that are very high compared to the cooling requirements of HTS equipment. The typical cryocooler for HTS applications operates between room temperature (25.degree. C.) and the HTS operating temperature which may be between 30 K and 77 K. For example, in a generator, the HTS field winding may operate at 30 K while in an underground power cable, the HTS wires could be bathed in liquid nitrogen at 77 K. The key technology in known cryocoolers is the transfer of heat from the very cold cryogenic region to ambient air or other heat sinks at room temperature. [0009] In accordance with this invention, however, the HTS cryocooler is modified so that the thermodynamic cycle operates between the desired HTS wire temperature and a heat sink much closer in temperature to the wire compared to room temperature. This is done by linking the cryocooler into the air separation process, reducing the complexity and capital cost of the cryocooler without sacrificing operating reliability. [0010] Compared to existing cryocoolers that operate between an ambient temperature of 25.degree. C. and a working temperature of 30 K, the heat sink for the cryocooler in the example embodiment is approximately 77 K. The reduction in the "apparent" ambient temperature allows the cryocooler to be simpler, less expensive and more reliable. In addition, it consumes less power, thereby improving the efficiency advantage of the HTS equipment. [0011] In one exemplary embodiment, the cryocooler is based on a Reverse Brayton cooling cycle. Specifically, cold fluid from the ASU enters a reservoir available to the cryocooler and cools a separate fluid circulating between the cryogenic reservoir and a recuperative heat exchanger in the cryocooler. A separate fluid circulates between the recuperative heat exchanger and the HTS equipment. By rejecting heat from the HTS equipment to the cryogenic reservoir at a temperature of 63-90 K, instead of to a traditional heat sink at room temperature, i.e., 25.degree. C. (or 298 K), the complexity of the cryocooler can be reduced along with capital cost. [0012] In a second exemplary embodiment, the ASU may be linked with an otherwise conventional Gifford-McMahon (GM) cryocooler. In this embodiment, a pair of auxiliary heat exchangers is inserted in the links from the GM cryocoder compressors. One side of these heat exchangers is fed from the compressor and the other side from nitrogen lines from the ASU. [0013] In a third exemplary embodiment, nitrogen (gaseous or liquid) or liquefied air, which is to a large extent a by-product of the ASU cycle, is simply supplied as the primary coolant to the HTS equipment. The connection between the ASU and HTS equipment can be through insulated piping or via dewars (in the case of liquid coolants) that are filled by the ASU and moved as needed to the HTS equipment. [0014] Accordingly, in one aspect, the present invention relates to a cooling system for high temperature superconductor equipment comprising a cryocooler in heat exchange relationship with the high temperature superconductor equipment, and an air separation unit in heat exchange relationship with the cryocooler, said system arranged such that heat from the high temperature superconductor equipment is transferred to said air separation unit via the cryocooler. [0015] In another aspect, the invention relates to a cooling system for high temperature superconductor equipment comprising a cryocooler in heat exchange relationship with the high temperature superconductor equipment, and an air separation unit in heat exchange relationship with the cryocooler, the system arranged such that heat from the high temperature superconductor equipment is transferred to the air separation unit via the cryocooler, wherein the cryocooler includes a first heat exchanger and wherein a cryogenic fluid utilized in the air separation unit passes in heat exchange relationship with gaseous helium or neon from the high temperature superconductor equipment in the first heat exchanger, wherein the air separation unit includes a second heat exchanger, and wherein the cryogenic fluid passes in heat exchange relationship with said gaseous helium or neon in the second heat exchanger, and further wherein the gaseous helium or neon is compressed in a compressor upstream of the first heat exchanger and expanded in an expansion turbine downstream of the first heat exchanger. [0016] In still another aspect, the invention relates to a method of cooling high temperature superconductor equipment comprising (a) integrating cooling hardware of the high temperature superconductor equipment with an air separation unit of an integrated gasification combined-cycle power plant, and (b) transferring heat from the high temperature superconductor equipment to fluid in the air separation unit. [0017] The invention will now be described in connection with the drawings identified below. BRIEF DESCRIPTION OF THE DRAWINGS [0018] FIG. 1 is a schematic diagram of a Reverse Brayton-type cryocooler connected between a cryogenic reservoir of an air separation unit in an IGCC plant and equipment utilizing high temperature superconductors in accordance with a first exemplary embodiment; [0019] FIG. 2 is a schematic diagram of a Gifford-McMahon cycle cryocooler connected between an air separation unit in an IGCC plant and equipment utilizing high temperature superconductors in accordance with a second exemplary embodiment; and [0020] FIG. 3 is a schematic diagram of an arrangement where the equipment utilizing high temperature superconductors is cooled directly by fluid from an air separation unit in accordance with a third exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION [0021] The exemplary embodiments describe different arrangements for using a cryocooler for high temperature superconductors that links into the basic process for creating relatively pure oxygen in an IGCC power plant. FIG. 1 illustrates an arrangement 10 utilizing a Reverse Brayton cooling cycle cryocooler. This arrangement includes an otherwise conventional cryocooler 12 fluidly connected to a cryogenic reservoir 14 of an air separation unit (ASU) 16 that is incorporated into an IGCC plant 17 and that supplies pure oxygen (02) thereto. In this arrangement, cold fluid enters the reservoir 14 via line 18 and exits through the reservoir 14 via line 20 for return to the ASU. The fluid in this circuit (AB) is typically liquid nitrogen or liquid air at a temperature of between 63-92 K. The fluid in line 20 is slightly higher in temperature than in line A because of the heat rejected (i.e., transferred) from the cryocooler to the ASU, and at a slightly lower pressure because of the pressure losses within the reservoir 14. Continue reading... Full patent description for Integration of igcc plant with superconducting power island Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Integration of igcc plant with superconducting power island patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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