Selective catalytic reduction design considerations

The 0 rigin o f t he c atalytic a ctivity i n t he v arious r eactions c atalyzed b y F e-zeolites h as been intensively debated over the last decade. In spite of the considerable efforts to characterize these materials, available data are not yet sufficient to conclude exclusively on the structure of the active iron. Binuclear iron species in FeZSM-5 have been designated as the active site in various reactions, including direct N2O decomposition, selective oxidation of benzene to phenol with N2O, and selective catalytic reduction (SCR) of NO c with hydrocarbons. However, in the last reaction, small oligonuclear species of composition Fc404 and isolated iron ions have also been proposed as active sites. ... 

The combustion of natural gas with air is accompanied by formation of nitrogen oxides. This becomes significant above 1400-1500 C, which is easily surpassed in normal diffusion flames. The problem is solved by use of low NOx burners and further reduction can be obtained by cleaning the flue gas using selective catalytic reduction (SCR) with ammonia [510]. Low NOx burners have longer flames in order to limit the maximiun temperatures, but this has a significant impact on the heat flux and temperature profiles in the reformer, since it tends to make the flux profiles wider. The burner type must be taken into consideration in the design. 

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