PURPOSE: To obtain an ammonia concentration by measuring a mixed gas with a nitrogen oxide concentration meter and at the same time performing measurement similarly after the mixed gas is passed through a denitrification catalyst and then subtracting each concentration.
CONSTITUTION: An exhaust gas containing nitrogen oxide NOx and ammonia NH3 is samples by a probe 1 and a specified amount of NO gas is mixed into the sampling from a supply source 5 of nitrogen monoxide. After that, NOx concentration Na is measured by A-system NOx meter 2a in the mixed gas. On the other hand, the mixed gas passes through a denitrification catalyst 3 and NOx concentration Nb is measured by B-system NOx meter 2b. These are sent to an operator 7, the concentration Nb is subtracted from the concentration Na, and it is output as NH3 concentration. In this case, the output Na of A system increases along with an amount of NO to be added. On the other hand, the output Nb in B system does not increase until unreacted NH3 is reduced completely by the catalyst 3 and then increases according to addition of NO, thus enabling an output of the operator 7 to be constant for indicating the NH3 concentration within the exhaust gas.
MORII ATSUSHI
MORIMOTO SHOJI
RYOMEI ENG CORP LTD