In-furnace measurement of sulphur and nitrogen species in a recovery boiler

There is a lack of experimental data on the gas composition in recovery boiler furnaces, particularly in the lower furnace and at the black liquor spraying level. Experimental determination of the gas composition in full-scale furnaces is important for the understanding of the kinetics of the gasphase reactions and the formation of different intermediates in the combustion process. The gas composition was measured in the furnace of a large recovery boiler using a new gas sampling method. The measurements were carried out from the primary air level to the upper tertiary cur level. The measurements were a part of an extensive campaign planned and carried out to support validation of models hosed on Computational Fluid Dynamics. This paper will focus on the sulphur and nitrogen species measured in the furnace and on the developed gas sampling probe. A number of reactive sulphur and nitrogen intermediates were identified and quantified in the measurements. Especially high concentrations of different intermediates were measured at the black liquor spraying level. Measured nitrogen and sulphur species include: nitrogen monoxide (NO), nitrogen dioxide (NO(2)), ammonia (NH(3)), hydrogen cyanide (HCN), hydrogen sulphide (H(2)S), sulphur dioxide (SO(2)), methyl mercaptan (CH(3)SH), ethyl mercaptan (C(2)H(5)SH), dimethyl sulphide ((CH(3))(2)S), dimethyl disulphide ((CH(3))(2)S(2)), carbonyl sulphide (COS), and carbon disulphide (CS(2)). Some of these have not been reported before in full-scale measurements.