COLD FLOW VELOCITY-MEASUREMENTS IN RECOVERY BOILERS .1. INTERACTION OF PRIMARY AND SECONDARY AIR-FLOWS

Cold air flow velocities were measured in a commercial recovery boiler during shutdown periods, using hot-wire anemometers, modified to indi cate direction. Five tests were carried out using different primary an d secondary air configurations. The conditions tested included arrange ments recommended by others to improve gas flow uniformity, as well as unrealistic extremes to be used in the evaluation of computational fl uid dynamic models. The measurements demonstrated the inherent unstead iness of recovery boiler flows and confirmed that balanced air flows t hrough opposed walls result in a central region of high velocity upwar d flow. Interlacing of the secondary air significantly reduced the pea k velocity and flattened the upward velocity profile at the liquor gun level.