초록 ▼

Enhanced high temperature fuel cell systems, such as solid oxide fuel cell systems and molten carbonate fuel cell systems are disclosed. Embodiments of the disclosure include solid oxide and molten carbonate fuel cell systems incorporating gas separation apparati facilitating the recycle of hydroge

Enhanced high temperature fuel cell systems, such as solid oxide fuel cell systems and molten carbonate fuel cell systems are disclosed. Embodiments of the disclosure include solid oxide and molten carbonate fuel cell systems incorporating gas separation apparati facilitating the recycle of hydrogen fuel from fuel cell anode exhaust for supply to the fuel cell anode inlet, such systems capable of improved power densities and efficiencies of operation. Further embodiments of the disclosure include solid oxide and molten carbonate fuel cell systems incorporating inventive combinations of anode materials conducive to combination with enriched hydrogen fuel. Other embodiments of the disclosure include gas separation apparati for providing enriched oxygen feed to the cathode inlet of solid oxide and molten carbonate fuel cells.

대표청구항 ▼

I claim: 1. A method for operating an electrical current generation system comprising a high temperature fuel cell operating at a temperature of at least 250° C. including a cathode channel with air supply means delivering air to the cathode channel and an anode channel comprising an anode inlet an

I claim: 1. A method for operating an electrical current generation system comprising a high temperature fuel cell operating at a temperature of at least 250° C. including a cathode channel with air supply means delivering air to the cathode channel and an anode channel comprising an anode inlet and an anode outlet, whereby at least one hydrocarbon feedstock is subject to internal reforming in the anode channel to produce a hydrogen containing fuel gas, and a hydrogen recycle means configured to receive an anode exhaust gas comprising hydrogen from the anode outlet, and to enrich and recycle at least a portion of the hydrogen from the anode exhaust gas for supplying to the anode inlet, the method comprising: controlling the hydrogen recycle means and the air supply means to operate the high temperature fuel cell in a substantially thermally balanced regime at a normal design operating point, the system generating only enough high grade heat at a normal design operating point to be self-sustaining while substantially all waste heat of the system is rejected at a relatively low temperature; and controlling the hydrogen recycle means and the air supply means to shift the operating point of the system for peak power demands or for turndown to low delivered power generation. 2. The method according to claim 1 wherein the hydrogen recycle means comprises a rotary VPSA gas separation system, configured to provide a recycle gas enriched in hydrogen relative to the anode exhaust gas for supplying to the anode inlet, comprising at least one vacuum pump powered by the high temperature fuel cell, a variable motor means such that the power of the vacuum pump may be varied, and a variable rotary motor means powered by the high temperature fuel cell, such that the rotational speed of the rotary VPSA may be varied, the method additionally comprising varying the power of the vacuum pump and the rotational speed of the rotary VPSA to control the volume of hydrogen-enriched recycle gas supplied to the high temperature fuel cell to maintain the operation of the high temperature fuel cell in a substantially temperature balanced regime. 3. The method according to claim 1 wherein the electrical current generation system has an efficiency of at least about 70% when electrochemical fuel utilization of the high temperature fuel cell is at least about 90%. 4. The method according to claim 1, shifting the operating point of the system in response to peak power demands by increasing the speed of the hydrogen recycling means so as to maintain the fuel cell anode fuel supply substantially in proportion to electrical current being delivered, while increasing the fuel cell cathode air flow more than proportionally to electrical current being delivered so as to provide enhanced stack cooling under peaking power conditions. 5. The method according to claim 4, in which the fractional increase of air flow from the normal design operating point is in the range of about 1.5 to about 2.5 times the fractional increase in current flow from the normal design operating point. 6. The method according to claim 4, controlling air flow in response to departures of fuel cell stack temperature from the normal stack operating temperature. 7. The method according to claim 4, controlling air flow in response to variations of electrical current being delivered. 8. The method according to claim 1, turning down the operating point of the system to an idle or standby mode to produce relatively low electrical current and power, by reducing the fuel cell anode fuel supply and the fuel cell cathode air flow, while slowing down the hydrogen recycling means. 9. The method according to claim 8, burning excess anode exhaust fuel not recovered by the hydrogen recycling means so as to assist the system to remain at working temperature in the idle or standby mode. 10. The method according to claim 8, further stopping the hydrogen recycling means and burning the anode exhaust gas to assist the system to remain at working temperature in the idle or standby mode. 11. The method according to claim 8, slowing down the cathode air flow more than proportionally to the reduction of electrical current delivered, so as to reduce convective cooling of the fuel cell stack by air circulation through the system, while also increasing heat generation in the stack by partial oxygen deprivation and consequently reduced voltage efficiency. 12. The method according to claim 11, slowing down the cathode air flow so as to establish a low cathode stoichiometry in the range of about 1.1 to about 1.5. 13. The method of claim 1 in which substantially no high grade heat is delivered so as to have a minimum thermal signature. 14. The method of claim 1, operating the fuel cell at a cell voltage in the range of about 800 to about 950 millivolts. 15. The method of claim 14, operating the fuel cell at a cell voltage in the range of about 900 to about 950 millivolts. 16. A method for operating an electrical current generation system, comprising: providing a high temperature fuel cell that operates at a temperature of at least 250° C., the fuel cell including a cathode channel with an air supply delivering air to the cathode channel and an anode channel comprising an anode inlet and an anode outlet, whereby at least one hydrocarbon feedstock is internally reformed in the anode channel to produce a hydrogen containing fuel gas, and a hydrogen recycler that receives an anode exhaust gas comprising hydrogen from the anode outlet to enrich and recycle at least a portion of the hydrogen from the anode exhaust gas for supply to the anode inlet; controlling the hydrogen recycler and the air supply to operate the high temperature fuel cell in a substantially thermally balanced regime at a normal design operating point, the system generating only enough high grade heat at a normal design operating point to be self-sustaining while substantially all waste heat of the system is rejected at a relatively low temperature; and controlling the hydrogen recycler and the air supply to shift the operating point of the system for peak power demands or for turndown to low delivered power generation. 17. The method according to claim 16 wherein the hydrogen recycler comprises a rotary VPSA gas separation system that provides a recycle gas enriched in hydrogen relative to the anode exhaust gas for supply to the anode inlet, the system comprising at least one vacuum pump powered by the high temperature fuel cell and having a variable motor such that the power of the vacuum pump may be varied, and a variable rotary motor powered by the high temperature fuel cell, such that the rotational speed of the rotary VPSA may be varied, the method additionally comprising varying vacuum pump power and rotary VPSA rotational speed to control volume of hydrogen-enriched recycle gas supplied to the high temperature fuel cell to maintain the high temperature fuel cell operating in a substantially temperature balanced regime. 18. The method according to claim 16 wherein the electrical current generation system has an efficiency of at least about 70% when electrochemical fuel utilization of the high temperature fuel cell is at least about 90%.