Thyssenkrupp Industrial Solutions Ag

Thyssen Krupp Ag

Thyssenkrupp Uhde Gmbh

Christian Perbandt

Meinhard Schwefer

Rolf Siefert

Michael Groves

Klaus Ruthardt

Bernhard Hundgen

A method of reducing NOin tail gas obtained during startup of a plant for preparing nitric acid may involve heating the tail gas from a starting temperature T, through a threshold temperature T, to an operating temperature Tat which steady-state operation of the plant can occur (T&#x3c;T&#x3c;T). NO-containing tail gas may be passed through a storage medium and at least partially stored while the temperature of the tail gas is lower than the threshold temperature T. The NOmay be released, preferably when the temperature of the tail gas has attained the threshold temperature T. The NOmay be combined with a reducing agent in the presence of an SCR catalyst after the temperature of the tail gas has exceeded the threshold temperature T, but not before, resulting in catalytic reduction of at least a portion of the NO.

Reducing the emission of nitrogen oxide when starting up systems for producing nitric acid

A process for removing NO and NOfrom offgases by catalytic decomposition of NO by means of iron-containing zeolite catalysts and catalytic reduction of the NOby means of reducing agents, the deNOstage connected downstream of the deNO stage being operated at inlet temperatures of T&#x3c;=400&#xb0; C., and the inlet gas for the deNO stage comprising water and having a selected NO/NOratio, and the operating parameters of temperature, pressure and space velocity of the deNO stage being selected so as to result in an NO degradation of 80 to 98%. Under these conditions, a degree of NOoxidation of 30-70% is established at the outlet of the deNO stage, which is defined as the ratio of the molar amounts of NOto the total molar amount of NO. The result of this is that the downstream deNOstage can be operated under optimal conditions. Also provided is an apparatus for carrying out the process.

Process and apparatus for eliminating NOX and N2O

Disclosed is a method and system for reducing the nitrogen oxide off-gas concentration in a nitric acid plant operated under pressure and equipped with a residual gas purification first reactor configured to remove nitrogen oxides from the off-gas during steady-state operation of the plant, and a second reactor configured to remove nitrogen oxides from the off-gas during a start-up and/or shut down of the plant. The method includes, during start-up and/or shut-down of the nitric acid plant, passing pressurized nitrogen-oxide-containing off-gas from the nitric acid plant and a gaseous reducing agent for the nitrogen oxides into the second reactor charged with a catalyst, to reduce the NOx content in the off-gas by at least catalytic reduction. Using the process and system, a colorless start-up and shut-down of nitric acid plants is possible and the nitrogen oxide content in the off-gas during start-up and/or shutdown can be substantially lowered.

Process for reducing the nitrogen oxide off-gas concentration in a nitric acid plant during shut-down and/or start-up, and nitric acid plant suitable therefor

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Dortmund, Germany

Christian Perbandt