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The four-cycle cycle was adapted to produce hydrogen

Georgia Tech

Researchers at the Georgia Institute of Technology have developed a compact four-stroke piston unit for catalytic methane reforming and hydrogen production. The latter can already be used, for example, in hydrogen fuel cells. The results of the work of scientists are  published  in Indusrial & Engineering Chemistry Research, and a brief account of them is given in the  message  on the Institute’s website. New plants can be combined into a circuit, thereby increasing the yield of hydrogen.

Reforming  is a process of catalytic processing of hydrocarbons used to increase the octane number of gasolines, the production of aromatic hydrocarbons or hydrogen-containing gas. The process takes place in large installations – reactors, usually connected in series. During the passage of the hydrocarbon mixture, it is heated to a temperature of 490-900 degrees Celsius and subjected to dehydrogenation in the presence of a catalyst, usually platinum or platinum alloys.

Catalytic reforming requires constant maintenance of pressure in 19-35 atmospheres and relative strong heating, as dehydrogenation of hydrocarbons is an endothermic process. This requires serious energy costs. In addition, energy is also needed for the operation of a cascade of compressors that drive the hydrogen-containing gas formed in the reforming process. At the same time, there is a growing need for economical and compact reactors for reforming.

American researchers have developed a reactor with a movable piston, cylinder and valve system. It is quite compact and, unlike industrial installations, does not require strong heating. The reactor operates on a four-cycle cycle. At the first stroke, methane, mixed with steam, is fed through the valves into the cylinder. Thus the piston in the cylinder smoothly falls. After the piston reaches the lower point, the flow of the mixture overlaps.

At the second cycle the piston rises, squeezing the mixture. At the same time, the cylinder is heated to 400 degrees Celsius. Under high pressure and heating conditions, the reforming process takes place. As hydrogen is released, it passes through a membrane that stops the carbon dioxide that also forms during the reforming. Carbon dioxide is then absorbed by the adsorbent material mixed with the catalyst.At the third stroke the piston descends to the lowest position, sharply reducing the pressure in the cylinder. In this case, carbon dioxide is released from the adsorbent material. Then begins the fourth stroke, which opens the valve in the cylinder, and the piston starts to rise again. During the fourth bar, carbon dioxide from the cylinder is squeezed out into the atmosphere. After the fourth cycle, the cycle begins again. In the near future, scientists intend to assemble and test a large methane reformer.

Last spring, the Central Design Bureau of Marine Engineering “Rubin” completed the design of a diesel-electric fifth generation “Kalina” submarine capable of being under water substantially longer than modern ships of this class. The new ship will receive an air-independent power plant operating on a high-purity hydrogen-containing gas. He will receive on board submarines from diesel fuel by reforming.

The resulting hydrogen will be supplied to hydrogen-oxygen fuel cells, where it will generate electricity for engines and on-board systems. Under such a scheme, designers expect to receive a method of almost silent generation of electricity. As expected, the capacity of the installation, designed by Rubin, will be about 400 kilowatts. The development of an anaerobic power plant is planned to be completed in 2018.

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