A parametric evaluation of particle-phase dynamics in an industrial pulverized-coal-fired boiler

A parametric study on the variation of particle size, velocity and number density with boiler operating conditions has been completed in a full-scale, tangentially fired, 85 MW(e) pulverized-coal-fired boiler, using a laser-based diagnostic probe. Variables in the lest included boiler load (60 or 85 MW,), coal type and excess air (2.5 or 4.5%). Two bituminous coals were used: HV and LV, with 7 and 10wt% ash respectively. Measurements were made in the radiant section, at the entrance to both the convective pass and economizer, and downstream of the economizer. Variations in particle velocity profiles were correlated with changes in boiler load. Port-to-port velocity variations were associated with changes in the gas flow field imposed by boiler geometry and with gas temperature reductions at downstream locations. Differences in the particle size distribution for a single coal type were nearly always associated with changes in the number density of particles > 10 mu m. Mass loading profiles varied with location in the boiler and coal type. In the radiant section of the boiler, these profiles support a centrifugal effect exerted on the condensed phase by the rotating flow. Throughout the boiler, mass loadings for the LV coal tests were consistently higher than those for the HV coal.