초록 ▼

A process for treating exhaust gas from internal combustion engines wherein the combustion exhaust gas contains HC, CO, O2,soot and possibly NOx. In treating the combustion exhaust gas, HC is oxidized to COxand H2O: NO, if present, is oxidized to NO2and soot is oxidized by reaction with NOx. In addi

A process for treating exhaust gas from internal combustion engines wherein the combustion exhaust gas contains HC, CO, O2,soot and possibly NOx. In treating the combustion exhaust gas, HC is oxidized to COxand H2O: NO, if present, is oxidized to NO2and soot is oxidized by reaction with NOx. In addition, NOxis generated by oxidizing ammonia and NOxis introduced into the exhaust gas upstream of the oxidization of soot by reaction with NOx.

대표청구항 ▼

1. Process for treating combustion exhaust gas containing HC, CO, O2,soot and possibly NOx, wherein the process comprises the steps of: (i) oxidising HC to CO2and H2O; (ii) oxidising NO (if present) to NO2; and (iii) oxidising said soot by reaction with NO2 wherein the improvement comprises t

1. Process for treating combustion exhaust gas containing HC, CO, O2,soot and possibly NOx, wherein the process comprises the steps of: (i) oxidising HC to CO2and H2O; (ii) oxidising NO (if present) to NO2; and (iii) oxidising said soot by reaction with NO2 wherein the improvement comprises the step of generating NOx by oxidising ammonia and introducing NOx into the exhaust gas upstream of step (iii). 2. Process according to claim 1 in which ammonia oxidation is effected in step i. 3. Process according to claim 1, wherein step (i) precedes step (ii). 4. Process according to claim 3, wherein the ammonia oxidation is effected in step (ii). 5. Process according to claim 1 further comprising, after step (iii), a step of NOx removal. 6. Process according to claim 5 comprising absorption of NOx, with intermittent in-line regeneration by injection of a NOx-specific reactant and reaction over an SCR catalyst, the catalyst being present in and/or following the absorbent. 7. Process according to claim 6 in which ammonia oxidation is controlled to provide incomplete reaction, thereby slipping enough ammonia to provide the NOx-specific reactant. 8. Process according to claim 1 in which the step of introducing NOx into the exhaust gas is controlled in response to a signal from sensor means indicating that, in the gas entering step (ii), the content of NOx is or has become too low and/or the content of soot is or has become too high, relative to oxidation of soot by NO2in step (ii). 9. Process according to claim 8 in which said injection of NOx-specific reactant is controlled in response to: (a) tail pipe gas composition sensor indication of NOx or ammonia in excess of design; and (b) if a NOx absorber is used, programmed regeneration period. 10. Process according to claim 1 in which the step (i) catalyst, the step (ii) catalyst or the step (i) and step (ii) catalysts is a supported platinum group metal. 11. Process according to claim 1 in which soot is collected on a filter. 12. Process according to claim 1 in which steps (i), (ii), and (iii) are carried out in a continuously regenerating trap system. 13. Process according to claim 1 in which the exhaust gas is the product of an engine operated with a fuel containing less that 50 ppm w/w sulphur compounds calculated as S. 14. Process according to claim 6, wherein the NOx-specific reactant is ammonia.