Purification Techniques for Hydrogen and Oxidants in Fuel Cells

A method to control hydrogen purging in fuel cell vehicles to prevent damage and improve efficiency. It uses an algorithm to estimate hydrogen concentration in the fuel cell stack by monitoring voltage and pressure changes when the hydrogen injection valve is closed. If the concentration falls below a threshold during injection pulses, the purge valve opens to remove water and nitrogen.

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Techniques to control purging of fuel cells to remove accumulated gases and water at the anode, without excessive purging. The method involves periodically opening a purge valve when the fuel cell is at a lower pressure than its nominal operating pressure. The lower pressure is 70-95% of the nominal pressure. If the purge valve doesn't open within a maximum time, it could indicate a valve jam.

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Process to purify hydrogen from a high-pressure tank to a level suitable for use in fuel cells. The process involves flowing the hydrogen stream through an adsorbent purifier to remove contaminants before delivering the purified hydrogen to the fuel cell. Adsorbents like metal organic frameworks (MOFs), zeolites, activated carbon are used to selectively adsorb impurities like CO, CO2, moisture from the hydrogen stream.

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High efficiency, low emission integrated system that produces hydrogen and electricity using a fuel cell with an integrated steam methane reformer (SMR) to convert natural gas to hydrogen. The system includes a water-gas shift reactor, absorber column, PSA purification system, and other components to increase the hydrogen concentration from the SMR and remove impurities. The system also recycles CO2-rich flashed gas and anode exhaust to the SMR to increase heat production.

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A compact, efficient system for removing carbon monoxide from impure hydrogen fuel before feeding it to a fuel cell. The system involves a compact device with a solid electrolyte coated with a catalyst that adsorbs carbon monoxide from the hydrogen gas when an electrical potential is applied across the electrolyte. In regeneration mode, the potential is reversed to desorb and oxidize the carbon monoxide while generating additional hydrogen gas. This allows the device to continuously scrub CO from the fuel.

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A high temperature electrolyzer assembly called a reformer-electrolyzer-purifier (REP) assembly that produces hydrogen from natural gas and removes CO2 emissions. The REP assembly includes an electrolyzer fuel cell stack that can operate in reverse to separate CO2 from the hydrogen produced during natural gas reforming. The fuel cells also generate additional hydrogen from steam electrolysis. By using waste heat from the reforming process and high temperature operation, the REP assembly produces hydrogen with minimal CO2 emissions compared to conventional reforming.

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Method for controlling fuel cell operation to reduce platinum oxide generation and improve long-term durability. The method involves intermittently lowering the fuel cell stack voltage by reducing the DC-link voltage and performing hydrogen purges during idle stops. This reduces platinum oxidation before the oxide elutes and allows recovery of catalyst performance.

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A regenerative fuel cell system that produces hydrogen and oxygen fuel by electrolyzing water. The system has separate valves to return any crossover gases back to their storage tanks. When oxygen accompanies the hydrogen produced, the hydrogen and oxygen react to remove the oxygen before returning the pure hydrogen to storage. Likewise, if hydrogen accompanies the oxygen, they react to remove the hydrogen before returning the pure oxygen to storage. This prevents crossover gases from reaching the wrong tanks and potentially causing fires or explosions.

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A solid oxide fuel cell (SOFC) system that produces electricity, hydrogen and refined carbon dioxide simultaneously from liquid hydrocarbon fuel like gasoline or diesel. The system uses a series of process steps and components, including a hydrodesulfurization unit, steam reformer, water-gas shift reactor, fuel cell, oxygen generator, and CO2 purification system. It also incorporates hydrogen compression and storage for fueling fuel cell vehicles and an electrical output for powering electric vehicles.

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Recovering performance in an aged fuel cell stack by using a pulse operation scheme to simultaneously remove platinum oxides and desorb impurities like CO and SOx that have adsorbed onto the electrode surfaces. The scheme involves alternately inducing an OCV state and a hydrogen pumping reaction in the cathode using gas flow changes and pole substitutions. This allows recovery of both the cathode and anode performance.

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