METHOD FOR REMOVING N2O AND �ΟX FROM THE NITRIC ACID PRODUCTION PROCESS, AND AN INSTALLATION SUITABLE FOR SAME.

摘要

The invention relates to a method for producing nitric acid by catalytically oxidising NH3 with oxygen and then reacting the obtained �Οx with an absorption agent in an absorption tower, said tower comprising a catalyst bed for N2O decomposition arranged in the process gas after the catalytic NH3 oxidation and before the absorption tower in the direction of flow, and a catalyst bed for �Οx reduction and further N2O reduction, arranged in the residual gas after the absorption tower in the direction of flow. In the catalyst bed for N2O decomposition that is arranged in the process gas, as much N2O as possible is broken down such that before the residual gas enters the catalyst bed for �Οx reduction, the N2O content is at > 100 ppmv and a molar N2O/�Οx ratio of > 0.25 is the result; the catalyst bed for �Οx reduction and further N2O reduction, arranged in the residual gas, containing at least one zeolite catalyst loaded with iron; there being such an amount of NH3 added to the residual gas prior to entry into the catalyst bed that upon exit from the catalyst bed, an �Οx concentration of < 40 ppmv results; and the operating parameters being selected so as to produce an N2O concentration of <200 ppmv. The invention additionally relates to a nitric acid installation in which the N2O, formed during the catalytic NH3 oxidation, is catalytically removed in the process gas, with the �Οx content being reduced and the N2O content being further reduced in the residual gas, downstream of the absorption tower, and which is characterised in that at least the following elements are present: A) a reactor for the catalytic oxidation of NH3 with oxygen to produce a process gas containing �Οx, B) an absorption tower for reacting the obtained �Οx from the process gas with an absorption agent, a residual gas containing �Οx and N2O being the result, C) at least one first catalyst bed for N2O decomposition through which the process gas flows and which is arranged after the catalytic NH3 oxidation and before the absorption tower in the direction of flow, D) at least one second catalyst bed for �Οx reduction and further N2O reduction, through which the residual gas flows and which is arranged after the absorption tower in the direction of flow, E) at least one device, for feeding a gaseous reduction agent into the residual gas, arranged after the absorption tower and before the second catalyst bed in the direction of flow, F) the first catalyst bed containing a catalyst for decomposing N2O, and G) the second catalyst bed containing a catalyst which contains at least one zeolite loaded with iron. The method and installation allow N2O and �Οx emissions from nitric acid installations to be reduced in a particularly efficient manner.