Patent Number: 052308596
Section: description

In the device shown in FIG. 1, the flammable gas mixture is ignited between the inner grilles (19) by the sparking plug (20). Ignition sources 44 other than the sparking plug 20 may be used, for example, glow plugs, naked flames, or catalytic surfaces. The explosion-like combustion remains restricted to the space between the inner grilles (19). The hot combustion products can flow out through the grilles (18, 19) almost unhindered--preferentially upwards. The baffles (22) produce a chimney effect and reinforce the convection. In addition, the heat energy is removed by the cooling lines (21) carrying a coolant. Fresh, unburnt gas mixture flows into the space between the inner grilles (19) and is again ignited. The arrangement, as an example, of sparking plugs and glow plugs as ignition sources in the part volume proves to be particularly suitable for control of the combustion from the outside. For reliable prevention, in the case of mechanical damage to the grille, of a propagated ignition of the explosion through an opening thus formed into the remaining gas space, 2 grilles, electrically insulated from one another, are arranged at a mutual distance around the part volume. If external (for example mechanical) actions on the outer grille occur, the inner grille and the outer grille can come into conductive contact. This triggers a sensor 25 and interrupt switch 27 which interrupts the energy supply to the sparking plug and glow plug. The conductive contact of the two wire grilles is intrinsically safe and cannot initiate any sparks, since the potential difference between the grilles and the electric currents flowing on contact are chosen such that they are insufficient for spark formation. For reliable prevention of an explosive ignition in the remaining gas space by an overheated grille, the following measures are taken: interruption of the lead 30 to the sparking plug and glow plug by means of a corresponding output signal of a temperature sensor 26 which is arranged on one of the grilles, expediently on the inner grille. PA1 Control of the ignition sequence frequency by the corresponding output signal of the temperature sensor 26. PA1 A natural convection through the part volumes, resulting during H.sub.2 combustion, is reinforced by suitable devices such as, for example, fans 40 and/or baffles 22 having a chimney effect; with the increased atmospheric convection, more heat energy can be removed per unit time and larger quantities of H.sub.2 /air mixture can be fed; PA1 cooling of the inner and/or outer grille is effected, for example, by cooling lines 21 carrying a coolant flow, and heat pipes 21 show particular suitability for transporting the heat energy released by the combustion in the interior of the part volume into the remaining gas space. PA1 by sensors 23 which are arranged below and above one or more devices and allow a comparison of temperatures in the gas atmosphere, PA1 by sensors 24 which detect the electromagnetic radiation generated during the combustion reaction, PA1 by sensors 42 which detect the absorption of electromagnetic radiation which is absorbed by combustion products. PA1 this process proves to be insensitive to all substances (impurities) from the post-accident atmosphere; PA1 no additional openings are required in the CV wall; electric lead-throughs are as a rule available in sufficient numbers; PA1 no mechanically moving parts are required in the CV for the process and the functioning of the devices; PA1 ignition of the combustion of the gas mixture takes place only if the grille is undamaged; PA1 intensified cooling of the grille allows increased H.sub.2 conversions; PA1 failure of a device causes no problems, because of the high degree of multiple provision; PA1 H.sub.2 /air mixtures capable of detonation can be removed in an explosion-proof manner; PA1 failure or overheating of the grille leads to switching-off of the ignition sparks and/or of the heating of the hot surfaces and hence to an interruption of the hydrogen combustion in the particular device, so that reliable protection from an uncontrolled explosion or detonation of hydrogen in the remainder of the CV is ensured; PA1 the exothermic hydrogen combustion leads to increased convection in the post-accident atmosphere and hence to increased throughput of hydrogen/air mixture through the part volumes; PA1 the devices are maintenance-free and are not impaired in their operability even in the long term by chemical impurities in the gas space. A maximum temperature of the inner grille of about 2/3 of the ignition temperature of the flammable gas mixture in .degree. C. on hot surfaces is appropriate. A failure of an individual temperature sensor 26 cannot effect overheating of the outer grille and hence an explosion in the remaining gas space by this hot surface, since a fusible cut-out 28 as a passive safety element already finally interrupts the energy supply at 3/4 of the surface temperature in .degree. C., at which the gas mixture ignites; as an example, the following may be stated with regard to the heat removal after an NPS accident with H.sub.2 release into the CV: At high H.sub.2 conversion in the devices, additional measures for lowering the temperature are necessary, which are provided according to the invention as follows: In the case of H.sub.2 /air mixtures in the region of the lower ignition limit, hot surfaces of glow plugs prove to be more appropriate than ignition sparks from sparking plugs to remove the burning gas mixture. In cases, where different H.sub.2 concentrations are to be expected, a combination of glow plug and sparking plug in a device is preferred according to the invention, so that glow plugs can be used preferentially in the region of the lower ignition limit and sparking plugs can be used to an increasing extent at higher H.sub.2 concentrations. The removal of the flammable gas mixture in the devices can be monitored as follows: In a local region, an undesired, local pressure rise can occur as a result of simultaneous ignition in a plurality of multiple part volumes, since the combustion products--for example water vapor--are very hot. Different ignition times in these part volumes prevent such a local pressure rise; appropriately, this can be prevented by means of delay devices 29 in the branches of the lead 30 upstream of the devices 50. The following advantages are associated with the invention: in the combustion of, for example, hydrogen from a post-accident atmosphere of a nuclear power station, preferably with the aid of electric sparks and/or hot surfaces according to the proposed invention: The use of a grille having a mesh width of 0.1 mm has proved to be advantageous for the removal of hydrogen. The process presented and the devices for it are not restricted to a combustion of H.sub.2 in the nuclear field. In chemical plants, flammable gas mixtures can be burned and removed equally reliably, in which case, if necessary, appropriate thermal switches respond at temperatures which are specific to the flammable gas mixtures. A grille having a mesh width specific to the flammable gas mixture must likewise be chosen. A functional proof of the devices has been carried out experimentally for butane and methane. The use of a grille having a mesh width of 0.7 mm has proved to be advantageous for the removal of butane and methane.