Particle Formation And Deposition In Recovery Boilers

摘要

This paper summarizes a five year research investigation into particle formation and deposition in recovery boilers. The project includes (ⅰ) controlled experiments on particle formation and deposition, (ⅱ) experiments on fume sintering and hardening, (ⅲ) experiments on black liquor droplet combustion and char bed combustion, (ⅳ) field tests at two full-scale recovery boilers; (ⅴ) development of new models to describe the important sub-processes involved in particle formation and deposition, as well as models to describe deposit properties in recovery boilers; and (ⅵ) integration of algorithms describing these sub-process models into a comprehensive CFD code used to predict the performance of recovery boilers. This collaborative and multidiscipline investigation has significantly broadened our understanding of deposition, while uncovering deficiencies where additional work is needed. It is evident from this work that intermediate size particles (ISP), a class of particles between carryover (> 100 microns) and submicron fume, are produced during combustion of black liquor droplets and the char bed. While ISP are ubiquitous, abundant, and potentially important to steam tube fouling in recovery boilers, the mechanisms by which these particles are formed are not well understood.