Method for operating an exhaust-gas purification system based on a catalytic absorption system

Abstract

In a method for operating an exhaust-gas purification system, in which CO and NO are simultaneously oxidized in accordance with the SCONOx principle by means of a first catalyst, and the NO 2 formed is absorbed on the surface of the catalyst, in which furthermore SO 2 is oxidized in accordance with the SCOSOx principle by means of a second catalyst arranged upstream of the first catalyst, and the SO 3 formed is absorbed on the surface of the catalyst, and in which the first and the second catalyst are regenerated in a regeneration cycle at regular time intervals by means of a regeneration gas containing hydrogen, a reduced requirement for hydrogen is achieved and the overall performance of the purification system is enhanced by virtue of the fact that the regeneration of the first and second catalysts is carried out at time intervals of different lengths, and that the time interval between two regeneration cycles of the second catalyst is significantly longer than the time interval between two regeneration cycles of the first catalyst.

What is claimed as new and desired to be secured by Letters Patent of the United States is:  
     
         1 . A method for operating an exhaust-gas purification system, in which CO and NO are simultaneously oxidized in accordance with the SCONOx principle by means of a first catalyst, and the NO 2  formed is absorbed on the surface of the catalyst, in which furthermore SO 2  is oxidized in accordance with the SCOSOx principle by means of a second catalyst arranged upstream of the first catalyst, and the SO 3  formed is absorbed on the surface of the catalyst, and in which the first and the second catalyst are regenerated in a regeneration cycle at regular time intervals by means of a regeneration gas containing hydrogen, characterized in that the regeneration of the first and second catalyst is carried out at time intervals of different lengths, and in that the time interval between two regeneration cycles of the second catalyst is significantly longer than the time interval between two regeneration cycles of the first catalyst.  
     
     
         2 . The method as claimed in  claim 1 , characterized in that the time interval between two regeneration cycles of the second catalyst is selected as a function of the SO 2  content of the exhaust gas to be purified.  
     
     
         3 . The method as claimed in either of claims  1  and  2 , characterized in that the time interval between two regeneration cycles of the second catalyst is between 2 and 24 hours.