This paper describes measurements in several operating, modern recovery boilers, and simulations of them. The measured results are compared to calculations using the computational fluid dynamics code Fluent. Velocity and temperature fields were measured above the bull nose, carry-over at the bull nose level, and unburned gases after the boiler. The velocities above the bull nose have been measured using a special, cooled Pitot tube, which allows dusty conditions and the presence of carry-over. The suction pyrometer was used for the flue gas temperatures to eliminate measurement errors due to thermal radiation losses. The flow field measurements revealed clearly a re-circulating area above the bull nose in one of the boilers discussed in this paper. Two different modeling approaches were used for calculating the super heater region. Both approaches predicted flow patterns that agreed reasonably well with the field measurements. The carry-over and unburned gases were predicted using a model that has been developed for the lower furnace phenomena. The carry-over predictions were within an acceptable range with the measured values, but the absolute values of the unburned gases were typically too low due to shortcomings in the model.
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