Miljøprojekt nr. 1885, 2016

Sulfur trioxide measurement technique for SCR units


Combustion of fossil fuels causes emission of, for example, NOx and SOx those in addition to CO2 are the major of environmental concern. The most effective way to reduce NOx is with selective catalytic reduction (SCR) which combines the flue gas with certain amount of ammonia over catalyst that speed NOx reduction into nitrogen and water.

A major SCR concern is the release of unreacted ammonia (ammonia “slip”) which can cause large problems than the NOx itself. In, for example, biomass co-firing SOx in the flue gas contains mainly from sulfur dioxide (SO2) with small (a few ppm) amount of sulfur trioxide (SO3). Over catalyst some additional oxidation of SO2 to SO3 is also taking place. SO3 in the presence of ammonia forms ammonium sulfate and ammonium bisulfate salts those deposits on catalyst, air heater baskets, heat recovery steam generators and other downstream equipment. Resultant ammonium bisulfate and sulfate particle diameters are on the order of a few microns and thereby contribute to PM10 emissions finally fouling the micropore structure of the catalyst and limiting catalyst reactivity.

Development of SO3 in situ measurement technique with fast response time suitable for modern industrial applications is highly of interest.

The purpose of the project is the development of SO3 in situ measurement technique which will be suitable for industrial applications where SO2/SO3 emissions occur as e.g. SCR units of power plants, large ship engines running on heavy S-fuel and etc.

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