ABSTRACT
This paper presents results of inertial impaction calculations using part of a comprehensive model being developed by the authors that considers the variations in target shape with time. Boiler design specifics, load, coal properties, boiler operational choices, and locally-entrained ash characteristics are input in terms of superheater tube diameter, steam temperature, flue-gas temperature, gas and particle velocity, gas and particle density, gas viscosity, multiple deposition time increments, particle diameter distributions, and dust loadings with elemental (or CCSEM) analyses for multiple narrow-range particle-diameter bins plus calculated viscosity for impacting particles. A coal ultimate analysis input is used to calculate flue gas composition and flue gas viscosity. Particle size distribution data from a five-stage cyclone measurement made near or downstream from the (pilot-scale-combustor-simulated or real) secondary-superheater location and elemental analyses of the stage-collected fly ash particles represent the major fuel-related input data. An alternative approach to direct measurement could use as input the fly ash data predicted from advanced coal analyses combined with appropriate computer models from other researchers when they are developed. This paper presents calculated two-dimensional deposition results via the inertial impaction mechanism that show the influence of several variables including time, superheater tube diameter, flue gas velocity, fly-ash particle density, particle diameter distribution, and dust loadings. Fly-ash data from the +20MWt, magnetohydrodynamic (MHD) facility at the University of Tennessee Space Institute (UTSI) are used for calculating deposition on superheater tubes during tests with coal+seed and coal alone. Additional data from the Pittsburgh Energy Technology Center (PETC) are examined for deposition of refractory AI2O3 particles injected into the flame zone to simulate fly-ash particles during 100% natural-gas firing in the Fuels Evaluation Facility (FEF).
