500 STPD Nitric Acid Plant

Description

Used 500 STPD Nitric Acid Plant
Built in 1974.
Plant uses synthesis by oxidizing ammonia to make nitrogen dioxide, then absorbed over a catalyst and water to
form nitric acid. New major equipment was installed during 1994 - 2013. Atmospheric air is
filtered and compressed in a centrifugal compressor, driven by a hot gas expander
and steam turbine. Liquid ammonia is vaporized, superheated and filtered and is joined by
the compressed air stream in a double mixing operation based on orificing. Combined
ammonia-air mixture enters the converter where the ammonia stream ignites and burns
very rapidly to form nitric oxide and water vapor. Hot reaction products and excess air
leaving the converter pass through a waste heat boiler and heat exchanger to: cool the
process gas before entering the cooler condenser; recover heat by the generation of
steam; and recover power by heating the tail gas for use in the hot gas expander. Partially
cooled process gas enters the cooler condenser where the water formed during ammonia
burning is condensed, forming weak nitric acid. Weak acid is separated from the gas
and transferred to the top of the absorber, where the weak acid and additional water are
fed through the top tray and counter act with the gas moving up the absorber through the
bottom. Product acid passes through a bleacher where dissolved oxides of nitrogen
are stripped from the acid using a countercurrent flow of air, before flowing into the
storage tank.