The oxidation of ammonia on woven and knitted platinoid grids

Results f pilot tests of catalytic systems equipped of (7–12) woven or (5–14) knitted platinoid grids in ammonia oxidation are presented. Platinoid woven and loose knitted grids with wire thickness 0,092 and 0,076 mm are made from metal alloy PdRhRu 15-3.5-0.5 (the so-called Alloy № 5), containing 81 % Pt, 15 % Pd, 3,5 % Rh and 0,5 % Ru (STO 00195200-013–2007 and STO 00195200-014–2007) at the Ekaterinburg non-ferrous metals plant JSC «EZOTSM». Tightly knitted grids made by «Umicore» сompany (Germany), and differs from the domestic grid knitted Pt076 greater mass and size of the outer surface of the cross section apparatus. There is a study of the influence of the mass, the outer surface, free volume of woven and knitted platinoid grids on nitric oxide yield. It’s determined the residual ammonia content after platinoid grid bed, depending on their number. The effectiveness of a bit of knitted grids surface depends on the influence degree of transport phenomena and reaction of the homogeneous reduction of nitrogen oxides with ammonia, which flows directly into the void volume of the platinoid catalyst bed. The use of loose knitted grids Pt076 is less efficient than the woven Pt092 in the range of nitric oxide yield ≥ 91,5 %. The test results show, that it is preferable to use a tightly knitted platinoid grids with lower free volume in the layer. If the loose knitted platinoid grids place on regular structure bed (a block catalyst or packing) it’s possible to minimize the free volume and the proportion of ammonia for improper turning.

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