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AssigneeUhde GmbH
InventorsMeinhard Schwefer, Rainer Maurer, Thomas Turek, Markus Kogel
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A process is described for reducing the NOx concentration and N2O concentration from the residual gas from nitric acid production. The process encompasses the passing of the residual gas leaving the absorption column, prior to entry into the residual gas turbine, through a combination of two stages. The first stage here reduces the NOx content and the second stage the N2O content of the gas, the NOx/N2O ratio prior to entry of the gas into the second stage being in the range from 0.001 to 0.5, and this gas being brought into contact in the second stage with a catalyst which is substantially composed of one or more iron-loaded zeolites.
A process for reducing the NOx concentration and N2O concentration from the residual gas from nitric acid production, where the residual gas leaving the absorption column is passed, prior to entry into the residual gas turbine, through a combination of two stages, the first stage reducing the NOx content by catalytic reduction, and the second stage reducing the N2O content of the gas by decomposition into nitrogen and oxygen, and where the molar NOx/N2O ratio prior to entry of the gas into the second stage is in the range from 0.01 to 0.5, and in the second stage this gas is brought into contact with a catalyst which comprises one or more iron-loaded zeolites, the operating pressure in the second stage being from 4 to 12 bar.
The process as claimed in at least one of the preceding claims, characterized in that the temperature of the first stage is <400° C., preferably <350° C.
The process as claimed in at least one of the preceding claims, characterized in that the temperature of the second stage is in the range of 300 and 550° C., preferably in the range of 350 and 500° C.
The process as claimed in at least one of the preceding claims, characterized in that both stages are operated at a pressure in the range of from 4 to 12 bar.
The process as claimed in at least one of the preceding claims, characterized in that the first stage is operated using the SCR process.
The process as claimed in at least one of the preceding claims, characterized in that, after leaving the absorption column and prior to entry into the first or second stage, use is made of a residual gas whose water content is in the range from 0.05 to 1% by volume, in particular in the range from 0.1 to 0.8% by volume.
The process as claimed in at least one of the preceding claims, characterized in that, prior to entry into the second stage, use is made of a residual gas whose NOx content is in the range from 1 to 200 ppm and whose N2O content is in the range from 200 to 2 000 ppm.
Dependencies are inferred from the claim text.