Select one of the catalytic reduction processes for removing

Select one of the catalytic reduction processes for removing NOx from combustion gases and tell why you think it is the best method

Solution

Nitrogen oxides are major pollutants in the atmosphere, being a precursor to acid rain, photochemical smog, and ozone accumulation. The oxides are mainly nitric oxide (NOx) and nitrogen dioxide (NO2) both of which are corrosive and hazardous to health. With the use of catalytic converters on automobiles, the initial regulatory focus of controlling of mobile NOx emissions has reached the point where further restriction has become economically impractical.

Methods of removal of nitrogen oxides from flue gases applied in recent years belong to the following groups

1)catalytic reduction (non-selective catalytic reduction (NSCR) and selective catalytic reduction (SCR))

2)adsorption,

3) absorption (acid and alkaline)

Absorption method is the best method.

Generally, absorption methods are the characterised by a simplified technological outlines and simple, typical apparatuses. Running of the process does not also cause substantial problems with their exploitation. Specialised sources, however, do not provide essential information on designing installations for purification of flue gas from nitrogen oxides

Absorption of nitrogen oxides in acids leads to producing of nitric acid or concentrated nitrogen oxides, thus application of such methods does not lead to formation of side-products but only to increase of the amount of the basic product. In most cases, the methods are not complicated in terms of chemical and processes engineering. Their shared defect is too slow mass transfer, which demands big capacities of apparatuses in industrial conditions. Many other corrosion problems are linked to these methods, which is usually omitted in the works on laboratory scale.