Process intensification writ large with microchannel absorption in nitric acid production

Under the best conditions studied experimentally, an absorption efficiency of 99% was achieved at 2 bar, with an intensification factor relative to a conventional tower absorber of the order of 1000. The NOx concentration in the tail gas is of the order of a few percent under these conditions but the tail gas flow is very small. While further work remains to develop a complete process with acceptable emissions, these results indicate that a microstructured system employing passages ∼1 m long could replace the ∼70 m absorption tower in a conventional nitric acid plant.