500 STPD Nitric Acid Plant

Description

Used 500 STPD Nitric Acid Plant
Built in 1974.
The plant synthesises nitric acid by oxidising ammonia to produce nitrogen dioxide, which is then absorbed over a catalyst and water to form nitric acid. Major new equipment was installed between 1994 and 2013. Atmospheric air is filtered and compressed in a centrifugal compressor, driven by a hot gas expander and steam turbine. Liquid ammonia is vapourised, superheated and filtered, and then combined with the compressed air stream in a double mixing operation based on orificing. The combined ammonia-air mixture enters the converter where the ammonia ignites and burns very rapidly to form nitric oxide and water vapour. Hot reaction products and excess air leaving the converter pass through a waste heat boiler and heat exchanger to: cool the process gas before it enters the cooler condenser; recover heat by generating 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 combustion is condensed, producing weak nitric acid. The 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 counteract the gas rising through the absorber from the bottom. The product acid passes through a bleacher where dissolved nitrogen oxides are stripped from the acid using a countercurrent flow of air, before flowing into the storage tank.