Nitric Acid adsorption abatement

The primary pollution problem in nitric acid plants is the abatement of NOx in tail gases. Three options exist to reduce these emissions to acceptable levels 1) Capture the NOx and convert it to additional nitric acid, 2) Capture the NOx and convert it to nitrate-nitrite sales, or 3) Render the NOx harmless by converting it to non-polluting compounds. The processes that have been developed to reduce emissions at existing and new plants can be classified into four general categories Absorption, Adsorption, Selective Catalytic Reduction (SCR) and Non-Selective Catalytic Reduction91. 

Adsorption Abatement uses acid-resistant molecular sieves to absorb the NOx from the tail gas. The adsorbent is periodically regenerated and the NOx recovered, converted to NOj and recycled to the plant for recovery as nitric acid. The tail gas may also be mixed with a reducing agent (usually natural gas or ammonia) and passed through a catalyst to reduce the NOx to elemental nitrogen. When natural gas is used, conditions must be carefully controlled and facilities installed to control the heat released by natural gas that reacts with both the NOx and the oxygen91. 

Adsorption abatement uses acid-resistant molecular sieves to absorb the NOx from the tail gas. The adsorbant is periodically regenerated and the NOx recovered, converted to N02 and recycled for recovery as nitric acid.91... 

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