Patent EP-4140947-A1 (EP)
Title: Mono pressure system for producing nitric acid and method of operating thereof
Inventor: VIGELAND BENT
IPC: C01B21/26
Filed: 2021-08-25
Abstract: The present disclosure discloses a system ( 1 ) for producing nitric acid at reduced power consumption. The system comprises an air compressor ( 36 ) for compressing air, comprising an inlet ( 48 ) and an outlet ( 49 ), thereby producing a compressed air stream ( 34 ); a source of pressurised oxygen-rich gas ( 50 ) having a pressure higher than the pressure of the compressed air stream ( 34 ), in fluid communication with the compressed air stream ( 34 ), to provide in an oxygen-rich gas/compressed air stream mixture ( 56 ); a mixing apparatus ( 35 ) for mixing the oxygen-rich gas/compressed air stream mixture ( 56 ) with an ammonia gas stream ( 32 ), to provide in an ammonia/oxygen-enriched air mixture ( 14 ); an ammonia converter ( 37 ) for oxidising ammonia in the ammonia/oxygen-enriched air mixture ( 14 ), to provide in a NO x  gas/steam mixture ( 15 ), comprising water and nitric oxide; means for measuring the temperature in the ammonia converter ( 37 ); means for regulating the concentration of ammonia and of oxygen in the ammonia converter ( 37 ); a steam turbine ( 51 ) or an electric motor (not shown) and means for converting steam into electricity (not shown), for converting steam into power, in fluid communication with the ammonia converter ( 37 ) or the NO x /gas steam mixture ( 15 ); a water cooler/condenser ( 38 ) for separating and condensing steam from NO x  gas in the gaseous NO x  gas/steam mixture ( 15 ), thereby generating an aqueous diluted nitric acid mixture ( 17 ) and a gaseous NO x  stream ( 22 ); an absorption tower ( 41 ) downstream the water cooler/condenser ( 38 ), for absorbing NO x  gases in water, to provide in a stream of raw nitric acid-containing residual NO x  gas ( 27 ) and a tail gas ( 5 ) comprising NO x  gases, comprising an absorption tower tail gas outlet ( 6 ) for evacuating the tail gas ( 5 ); and a tail gas expander ( 7 ) for expanding the tail gas downstream of the absorption tower comprising a tail gas expander inlet ( 8 ) in fluid communication with the absorption tower tail gas outlet ( 6 ), and a tail gas expander outlet ( 9 ). The system is further characterised in that it further comprises means for splitting the tail gas ( 5 ) into a tail gas stream ( 5 ) directed to the tail gas expander inlet ( 8 ) and a tail gas stream ( 10 ) directed to means for pressurising ( 53 ) for pressurising the tail gas stream ( 10 ) to a pressure of about P1 in fluid communication with the compressed air stream ( 34 ), to provide in a pressurised tail gas stream ( 52 ) joining the compressed air stream ( 34 ); and means for adjusting the amount of tail gas ( 5 ) being splitted into the tail gas stream ( 5 ) directed to the tail gas expander inlet ( 8 ) and the tail gas stream ( 10 ) directed to means for pressurising ( 53 ). The present disclosure further relates to a method for producing nitric acid, in the system of the disclosure, at reduced power compression. The present disclosure further relates to the use of the system of the disclosure for producing nitric acid at reduced power consumption. Finally, the present disclosure relates to the revamping of a system for producing nitric acid into the system of the disclosure.