Method and system for purifying the exhaust gases of a combustion engine

Abstract

A method and system for purifying exhaust gases of a combustion engine or an SCR method for purifying exhaust gases of an internal combustion engine of a vehicle, according to which ammonia gas is exclusively metered in the exhaust gases. The method includes: releasing ammonia gas from at least one solid absorbing matrix where it is stored by sorption; metering the released ammonia gas in the exhaust gases; regenerating the solid absorbing matrix including: generating a refilling ammonia gas by chemically decomposing an ammonia precursor in a biochemical decomposition unit mounted on board the vehicle and storing at least one protein component adapted to decompose the ammonia precursor; directing the refilling ammonia gas to the solid absorbing matrix where it is stored thereon.

1 - 15 . (canceled) 
     
     
         16 . A SCR or Selective Catalytic Reduction method for purifying exhaust gases of an internal combustion engine of a vehicle, according to which ammonia gas is exclusively metered in the exhaust gases, the method comprising:
 releasing ammonia gas from at least one solid absorbing matrix where it is stored by sorption; and   metering the released ammonia gas in the exhaust gases;   regenerating the solid absorbing matrix, including:
 generating a refilling ammonia gas by chemically decomposing an ammonia precursor in a biochemical decomposition unit mounted on board the vehicle and storing at least one protein component adapted to decompose the ammonia precursor; 
 directing the refilling ammonia gas to the solid absorbing matrix where it is stored thereon. 
   
     
     
         17 . A SCR method according to  claim 16 , wherein the protein component comprises at least one enzyme. 
     
     
         18 . A SCR method according to  claim 17 , wherein the enzyme is urease. 
     
     
         19 . A SCR method according to  claim 16 , wherein the biochemical decomposition unit includes a heater. 
     
     
         20 . A SCR method according to  claim 16 , further comprising separating water from the refilling ammonia gas by a liquid-vapour separator unit. 
     
     
         21 . A SCR method according to  claim 16 , further comprising compressing the refilling ammonia gas by a gas pressurisation unit, the compressing being performed before the directing the refilling ammonia gas to the solid absorbing matrix. 
     
     
         22 . A SCR method according to  claim 16 , wherein a stream of the refilling ammonia gas is metered in the exhaust gases. 
     
     
         23 . A SCR method according to  claim 16 , wherein the solid absorbing matrix is stored in a first tank and the ammonia precursor is stored in a second tank, and wherein the second tank is connected in a communicating manner to the biochemical decomposition unit, and the biochemical decomposition unit is connected in a communicating manner to the first tank. 
     
     
         24 . A SCR method according to  claim 16 , wherein the solid absorbing matrix comprises a plurality of cells containing at least one material adapted to store ammonia by sorption. 
     
     
         25 . A SCR method according to  claim 16 , wherein the ammonia precursor is a solid compound. 
     
     
         26 . A SCR method according to  claim 16 , wherein the ammonia precursor is an aqueous urea solution. 
     
     
         27 . A SCR method according to  claim 16 , wherein the first tank in which the solid absorbing matrix is stored is connected to a safety valve configured to release excess of gaseous ammonia to release the pressure above a given set-point. 
     
     
         28 . A system for applying an SCR method according to  claim 16 , the system comprising:
 a first tank mounted on board a vehicle and storing at least one solid absorbing matrix where ammonia is stored by sorption;   means for metering ammonia gas released from the solid absorbing matrix, in exhaust gases;   means for directing a stream of ammonia precursor solution to a biochemical decomposition unit mounted on board the vehicle and storing at least one protein component adapted to decompose the stream to generate a refilling ammonia gas;   means for directing the refilling ammonia gas to the solid absorbing matrix stored in the first tank.   
     
     
         29 . A system according to  claim 28 , wherein the protein component comprises at least one enzyme. 
     
     
         30 . A system according to  claim 29 , wherein the enzyme is urease.