Patent Number: 053217306
Section: summary

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Continuation of International Application Serial No. PCT/DE91/00508, filed Jun. 20, 1991. The invention relates to a process and a device for oxidizing hydrogen in the containment of a nuclear reactor plant with the aid of finely distributed catalyst particles. In a process of the above-described type, which is known from German Published, Non-Prosecuted Application DE-OS 29 22 717, corresponding to Published European Application No. 0 019 907, a catalyst powder, which is kept as dry as possible, is blown with inert gas into the upper part of the containment, so that it will drop downward by gravity and thus engage the entire space. Due to the high forces of adhesion prevailing in the catalyst powder in the dry state, only relatively large agglomerates that are 3 to 10 .mu.m in size, for instance, can be produced by such processes, even if complicated and expensive dispersing equipment is used. Such agglomerates rapidly settle, and because of the brief suspension times they lead to low hydrogen degradation rates. Moreover, in a humid atmosphere, the high flow velocities required to detach the agglomerates lead to high precipitation of the agglomerates and thus to catalytic deactivation. It is accordingly an object of the invention to provide a process and a device for the oxidation of hydrogen, which overcome the hereinafore-mentioned disadvantages of the heretofore-known processes and devices of this general type and in which a highly effective superfine particle atmosphere with long suspension times is produced by simple means. Moreover, this should be catalytically effectively feasible in the containment atmosphere to be oxidized. With the foregoing and other objects in view there is provided, in accordance with the invention, a process for oxidation of hydrogen in a containment of a nuclear reactor plant with the aid of finely distributed catalyst particles, which comprises spraying or atomizing catalyst particles in the form of a solution or suspension inside or outside a containment of a nuclear reactor plant; subsequently drying the sprayed solution or suspension by heating inside or outside the containment to produce aerosols; and introducing the aerosols produced outside into the containment. In accordance with another mode of the invention, there is provided a process which comprises causing the aerosols to rise in the interior of the containment. This can be done in a continuous operation. The liquid for the suspension or solution and the temperature that are selected, and optionally additional drying of the aerosol atmosphere make it possible to adapt to any prevailing conditions, within wide limits. The solution or suspension can be introduced into the containment through a plurality of nozzles, in order to provide a distribution in fine droplets from the very outset. Therefore, in accordance with a further mode of the invention, there is provided a process which comprises introducing the suspension or solution into the containment and spraying the suspension or solution, through at least one nozzle fed by a line. Especially if two-substance nozzles are used, suspension droplet collectives of from 3 to 30 .mu.m can be produced, which dry, depending on the solid content of the suspension, which varies from 0.1 to 10%, in such a way as to produce highly mobile superfine aerosols in the range of 1 .mu.m and less. In accordance with an added mode of the invention, there is provided a process which comprises heating the suspension or solution before the spraying. In accordance with an additional mode of the invention, there is provided a process which comprises producing suspension droplets having a statistical mean diameter of 3 to 30 .mu.m and resultant solid aerosols of 0.1 to 2 .mu.m containing the catalyst particles. In accordance with yet another mode of the invention, there is provided a process which comprises releasing the aerosols in a superheated state at a velocity of less than 5 m/s in the containment. In accordance with yet a further mode of the invention, there is provided a process which comprises catalytically superheating the aerosols. By extensive calculation and practical experimentation with aerosol deposition or accumulation processes in test containments, it was possible to prove that the aerosols produced and distributed according to the invention precipitate out in the most varied atmospheres at degradation rates of only an average of 0.5 per hour. Releasing them at velocities of less than 5 m/s, particularly in the superheated atmosphere, makes it possible to largely avoid both an addition or attachment to other liquid droplets present in the containment and the formation of water envelopes around the aerosols. Due to this long aerosol suspension time (platinum particles having a diameter of less than 0.5 .mu.m), it is possible with the process of the invention to achieve aerosol concentrations in the containment, even after one-half hour in operation, for instance, which, because of the large catalyst surface area and the short hydrogen diffusion paths, can lead to calculated hydrogen degradation rates of up to 1 kg/s and can thus contribute substantially to gaining control in the event of a malfunction. Catalyst deactivation from catalyst poisons can also be largely compensated for by continuous re-production of aerosols. It is also possible to not produce the solution or suspension until directly before it is introduced into the containment, preferably after preheating. This averts long dwell times with the danger of undesired chemical or physical changes. This is also true if the solution or suspension is produced outside the containment, where charging and maintenance might generally be simpler. An advantageous further feature of the invention provides that in terms of the quantity of suspension or solution sprayed or the concentration of the catalyst particles, the production of the solution or suspension is adjusted or regulated as a function of the hydrogen content in the containment. This makes it possible to minimize the expense for materials and energy, which may be important, especially in long-term operation. In accordance with yet an added mode of the invention, there is provided a process which comprises heating with a thermal recombiner. In accordance with yet an additional mode of the invention, there is provided a process which comprises producing the aerosol with a superheater catalyst by delivering aerosols containing catalyst particles to the superheater catalyst, and regenerating the superheater catalyst by accumulation of the catalytic aerosols. In accordance with again another mode of the invention, there is provided a process which comprises producing the solution or suspension inside the containment immediately before spraying in the containment. In accordance with again a further mode of the invention, there is provided a process which comprises adjusting the solution or suspension with a preheated liquid. In accordance with again an added mode of the invention, there is provided a process which comprises producing the solution or suspension outside the containment. In accordance with again an additional mode of the invention, there is provided a process which comprises heating with thermal ignition devices while spraying the solution or suspension in the containment. In accordance with still another mode of the invention, there is provided a process which comprises producing the solution or suspension by adjusting one of the quantity of liquid being used and the concentration of the catalyst particles being used, as a function of the hydrogen content in the containment. With the objects of the invention in view, there is also provided a device for oxidation of hydrogen in a containment of a nuclear reactor plant with the aid of finely distributed catalyst particles, comprising a container for receiving catalyst particles in the form of a solution or suspension; a distributor configuration connected to the container for spraying the solution or suspension inside or outside a containment of a nuclear reactor plant; and a heater for drying the sprayed solution or suspension before the solution or suspension is released into the containment. In accordance with another feature of the invention, there is provided a a vertical tube having an upper end and having a lower end with an inlet opening formed therein; a cap disposed at the upper end; the upper end of the tube having lateral outlet openings formed therein below the cap; at least one propellant catalyst or a heater disposed in the inlet opening; and a nozzle mounted above the propellant catalyst or heater for receiving the solution or suspension. In accordance with a further feature of the invention, there is provided a pressure vessel having a rupture membrane or bursting disk partitioning the pressure vessel into an upper part with a propellant gas or vapor cushion and a lower part with the solution or suspension, and a line connected between the tube and the lower part of the pressure vessel. The propellant gas cushion then forces the catalyst particles with the liquid through the tube, as soon as the outlet is uncovered, for instance by the opening of a valve. In accordance with an added feature of the invention, there is provided a preheating container disposed above the propellant catalyst or heater for receiving a small quantity of suspension or solution. This is done in order to provide for rapid aerosol production, particularly upon startup. In accordance with a concomitant feature of the invention, the distributor configuration has means for spraying the solution or suspension with solid aerosols having a mean diameter of 0.1 to 2 .mu.m. Other features which are considered as characteristic for the invention ar set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a process and a device for the oxidation of hydrogen, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.