A. Koga

D. Ianovski

K. "Munakata

S. Kanjo

T." Uda

Y. Asakura

Y. Yokoyama

National Institute for Fusion Science (NIFS-Repository)

§ 3. Development of High PerformanceCatalyst for Oxidation of Tritium inGaseous PhaseAdditionally, the use of metal honeycomb catalysts makes itpossible to raise rapidly the temperature of the catalystsystem due to the higher heat conductivity of metals.1010080C'>g60 <CDCD _.::J::o40CD§200o600500- Small diameter tube (1 mm¢)------- Packed bed (d =3mm. c-=0.5)4 6Liniar gas velocity [m/sJ100Fig. 1 Calculated pressure drop200 300 400Temp (Oe)Fig. 2 Conversions of H2 and CRt overPt/cordierite catalysto! if···r··.:;....- SV:8500hr-1 ;••••••• SV:4300hr-i iFe;; Gas <Ai'l,l/I. H2 Cone. :0.1% / ,.__ . CH4 Cone. :0.1% l: ,.',iT'-; ,.&,,;: ..:" ..- .... -.. ---,.o 100 200 300 400 500 600Temp (Oe)Fig. 3 Conversions of H2 and CH4 overPt/20%Cr-5%Al-Fe catalysto10'E105"'-l'lla.e"'010'Q)Q:80 ..... ....... ... . 80--.- BV: C'>§-'-SV:8500hr-: 0::JQ) 60 ._----- 60 <••••.•• SV: 4300hr- i CD0:: Q) 3:(1)tillCD __C 0 <+00 __--"'0en>. ::J::o__ ::I:40 40Q) ---> CDC §0(.;IFeed Gas (Ai r)20 --- . Hz Cone. :0.1% 20. CH4 Cone. :0. 1%10080§Q) 60O::Q)tillCO0 __._""Qen>.__ ::I:40Q)---0(.;I200Munakata, K., Koga, A., Kanjo, S., Yokoyama, Y.,Ianovski, D. (Interdisciplinary Graduate School ofEngineering Sciences Kyushu University),Asakura, Y., Uda, T.Recovery of tritium released into the working area offusion power plants or tritium-handling facilities is a keytechnique to establish the safety related to the fusiontechnology. The catalytic oxidation and adsorption is themost conventional and reliable method for removing tritiumthat is accidentally released into the working area of thesefacilities. If accidental tritium releases take place, largeamounts of air should be processed by the air cleanupsystem. Therefore, the air cleanup system needs be designedto deal with the air with high volumetric velocity. The highthroughput of air causes pressure drop in the catalyst bed,which results in higher loading to pumps or air compressors.The honeycomb catalysts, which are generally used in theautomotive industry, are designed to deal with highthroughput exhaust gases. Thus, it is worthwhile to study theapplication of the honeycomb catalysts to the air cleanupsystem. Figure 1 shows the calculated pressure drops as thefunction of linear velocities of the gas flowing through apacked bed (3 particle) and a small-diameter (l mm)tube modeled as a pass in a honeycomb. It is seen that thepressure drop is apparently smaller in the case of thesmall-diameter tube, which indicates that honeycombcatalyst is more suitable for the treatment of high-throughputair. In our previous works, the catalytic activity of metalhoneycomb catalysts with the cell density of 300 CPSI wasinvestigated. However, those oxidation performances werefound to be low. This time, the authors investigated thecatalytic performance of cordierite-based honeycombcatalysts. In addition, the effect of increase in cell density onthe catalytic activity was studied.Figure 2 shows the conversions of H2 and CRt over thePt/cordierite catalyst with the cell density of 400 CPSI. Asseen in this figure, H2 is almost completely oxidized at 100°C even at the space velocity of 16700 h-1, which indicatesthat the performance of the Pt/cordierite catalyst is higherthan that of conventional Pd/alumina catalyst. Thus, it wasfound that the Pt/cordierite catalyst is effective for oxidationof hydrogen isotopes in the gases with higher throughput.Figure 3 shows the conversions of H2 and CRt over thePt/20%Cr-5%Al-Fe catalyst with the cell density of 400CPSI. As seen in this figure, H2 is almost completelyoxidized at 100°C even at the space velocity of 8500 h-1. Incomparison with the results for the metal honeycombcatalysts (with the cell density of 300 CPSI) studiedpreviously, considerable improvement in catalyticperformance was observed. This is probably because of theincrease of the cell density, resulting in higher surface area.256

Development of High Performance Catalyst for Oxidation of Tritium in Gaseous Phase

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