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PROCESS FOR REDUCING THE NITROGEN OXIDE OFFGAS CONCENTRATION IN A NITRIC ACID PLANT DURING SHUTDOWN AND/OR STARTUP, AND NITRIC ACID PLANT SUITABBLE THEREFOR
PROCESS FOR REDUCING THE NITROGEN OXIDE OFFGAS CONCENTRATION IN A NITRIC ACID PLANT DURING SHUTDOWN AND/OR STARTUP, AND NITRIC ACID PLANT SUITABBLE THEREFOR
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机译:降低关机和/或启动过程中硝酸工厂中一氧化氮废气浓度的方法以及适合其的硝酸工厂
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摘要
Process for reducing the nitrogen oxide off-gas concentration in a nitric acid plant operated under pressure and equipped with residual gas purification during shut-down and/or start-up of the plant, wherein the residual gas purification is designed for removing nitrogen oxides from the off-gas for the steady-state operation. The process is characterized in that, during start-up and/or during shut-down of the nitric acid plant, pressurized nitrogen-oxide-containing off-gas from the nitric acid plant and gaseous reducing agent for the nitrogen oxides are passed into a reactor charged with catalyst, which reactor is provided in addition to the reactor of the residual gas purification, and in that the NOx content in the off-gas is reduced by catalytic reduction or in that the NOx content in the off-gas is reduced by catalytic reduction and the N2O content in the off-gas is reduced by catalytic reduction and/or by catalytic decomposition in the additional reactor. Furthermore, a nitric acid plant for carrying out this process is described. Using the process, or using the plant, a colourless start-up and shut-down of nitric acid plants is possible without problems, and the nitrogen oxide content in the off-gas during start-up and/or shut-down can be substantially lowered.
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