Device for removing hydrogen from a gas mixture and its use

Details Device for removing hydrogen from a gas mixture and its use Device for removing hydrogen from a gas mixture and its use

1998-06-22

2000-06-13

Knode, Marian C.

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Including heat exchanger for reaction chamber or reactants...

422211, B01D 5334

Patent

active

060746181

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a device for removing hydrogen from a gas mixture containing free hydrogen and oxygen by means of catalytic oxidation of the hydrogen. For this purpose, a support whose surface is coated with catalytically active material is secured in a reaction chamber that is suitable for oxidation. The support not only serves as a catalyst support, but it especially serves to dissipate the reaction heat that is released during the exothermal catalytic hydrogen oxidation. The gas mixture is fed into the reaction chamber through an inlet while the residual gas that remains after the oxidation of the hydrogen flows out of the reaction chamber via an outlet. Another subject matter of the invention is the use of said device.
The catalytic reaction of hydrogen present in an explosive gas mixture of hydrogen and oxygen is known. Catalytic oxidation makes it possible to prevent oxyhydrogen explosions in the gas phase. The catalysis then has to be carried out below the ignition temperature of the gas mixture, that is to say, below approximately 600.degree. C. [1112.degree. F.] at atmospheric pressure. Sufficient heat dissipation must be ensured in order to prevent the temperature from rising above this ignition temperature. If, in addition to the reactants hydrogen and oxygen, the gas mixture also contains inert gas fractions that do not participate in the reaction, such as, for example, nitrogen, then heat is also used to heat up these inert gas fractions. Thus, the temperature of the gas mixture in the reaction chamber can be adjusted by adding air to the gas mixture. The temperature on the surface of the carrier is kept above 100.degree. C. [212.degree. F.] so that the water vapor formed during the reaction cannot condense on the support surface, since water films on the catalytically active surface reduce its catalytic activity.
A catalysis in the liquid phase is described in a publication by R. Wagner et al. titled "Catalytic removal of dissolved oxygen from water", in Ion Exch. Adv., Proc. IEX 92, 1992, pages 144 to 150. This publication describes a process to bind dissolved oxygen in water by introducing hydrogen gas. The catalytic reaction that takes place here can, of course, also be employed to bind hydrogen. Platinum and palladium (on supports made of activated charcoal, aluminum oxide or ion-exchanger resin) are used as the catalysts. In order to achieve a sufficient conversion on the supports, which are situated under water, the gases must be present in a form dissolved in water. Nevertheless, the rate of conversion remains low when the water bath is at room temperature or even at higher water temperatures, so that large catalyst surfaces are necessary if this process is to be utilized. The reaction heat is absorbed by the water bath.
Gas mixtures that contain free hydrogen and oxygen in a stoichiometric ratio and that are consequently extremely explosive are generated, for instance, during the electrolytic production of superpure water. The use of the above-mentioned, known methods of hydrogen oxidation in such processes, however, entails a considerable effort; in this context, see IPAD Catalyst 25/250 D and German laid-open application no. 3,909,540 A1.
The objective of the invention, on the one hand, is to obtain a high rate of conversion for the catalytic hydrogen oxidation while, on the other hand, ensuring sufficient heat dissipation.
This objective is achieved according to the invention with a device of the type mentioned above by means of two alternative embodiments.
In one embodiment, the support secured in the reaction chamber, together with part of its catalytically active surface, is immersed into a liquid bath that is at a temperature below the condensation temperature of the water vapor formed in the reaction chamber, whereby a liquid inlet for the liquid bath simultaneously serves as the inlet for the gas mixture that is to be fed into the reaction chamber, while a liquid outlet concurrently serves as an outlet for the residual gas that remains after the oxidation reaction. B

REFERENCES:
patent: 2943921 (1960-07-01), King
patent: 4297319 (1981-10-01), Ishibashi et al.

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