OP-II-3

PP-III-13LOW-TEMPERATURE ABATEMENT OF NITROGEN OXIDES(N 2 O, NO x ) FROM THE EFFLUENT GASES IN NITRIC ACIDPRODUCTIONChumachenko V.A., Zenkovets G.A., Shutilov А.А., Kharitonov A.S.,Pirutko L.V., Mokrinsky V.V., Noskov A.S.Boreskov Institute of Catalysis of SB RAS, Pr. Lavrentieva, 5,Novosibirsk, 630090, Russia, vachum@catalysis.ruNitrogen oxides are among the most dangerous air pollutants. Due to highly toxicimpact of NO and NO 2 on humans, their emissions are strictly controlled in all basicindustries and transport and could be efficiently destroyed by catalytic reduction.Nitrous oxide N 2 O is much less toxic, but now it is also considered as an environmentpollutant and a greenhouse gas. Industrial large capacity nitric acid (NA) units areone of the greatest sources of both types of nitrogen oxides, contributing some 4-8%of total N 2 O emissions. However, in spite of some promising approaches [1-3], theproblem of NOx+N 2 O abatement has not been entirely solved so far.In this work we have analyzed the current status of N 2 O emissions after NOxcatalytic reduction in typical Russian NA technologies and selected the most promisingschemes for combined low-temperature NOx+N 2 O abatement. Experimental lab-scaletesting of new BIC catalysts have shown high activity both in selective catalytic reduction(SCR) of NOx by ammonia, and in subsequent N 2 O decomposition.NAtechnologyTable 1 N 2 O emissions in commercial NA unitsMethod of NOx reductionN 2 O concentration, ppminletoutletUKL-7 High-temperature, by CH 4 (~700°C) 900-1300 20-50UKL-7 SCR, by NH 3 (~280-300°C) * 560 780UKL-7 SCR, by NH 3 (~280-300°C) 900-1200 900-1000AK-72 High-temperature, by CH 4 (~700°C) 1000-1200 3-50Concentrations of N 2 O in effluent gases upstream and downstream the reactor forNOx reduction are presented in Table 1. Systems UKL-7 produce large amounts of N 2 Oafter SCR. Its increase (*) can be caused by improper NH 3 automatic control, or by NH 3excessive supply under wide variations of NOx content in effluents. So, N 2 O abatementin these technological schemes seems quite necessary and reasonable.Catalytic activity of BIC proprietary and commercial vanadia-alumina catalysts inSCR reaction was studied in a flow reactor at: GHSV – 7200 h –1 , [NO] – 1000 ppm,[NH 3 ] – 1100 ppm, [O 2 ] – 4.5 % vol., [H 2 O] – 3.0 % vol., [He] – balance. Degree of462