High Pressure Char Combustion

1. Influence of Pyrolysis Pressure on Char Reactivity (HPDT) Development of HPDT BYU High-Pressure Drop-Tube Heating rate significantly affects swelling properties during pyrolysis of bituminous coals at atmospheric pressure (Gale et al., Comb. Flame, 1995) Influence of Pyrolysis Pressure on Char Rate Constant (HPDT) Influence on Activation Energy Influence on Oxygen Order Temperature Profile Comparison of HP-FFB and HPDT High-Pressure FFB High-Pressure Drop-Tube High Pressure Char Combustion Dong Zeng, Michael M. Clark, and Thomas H. Fletcher Department of Chemical Engineering Brigham Young University, Provo UT, 20 Feb 2003 Why High Pressure? • To increase conversion efficiency in combined cycle (from 34% to ~60%!!!) -Less CO2 per MW of electricity • Has the potential to reduce pollutants -Sulfur removal easier -Concentrated CO2 stream may help CO2 sequestration efforts • To reduce reactor size • High Pressure Char Work at BYU • FFB Chars from atmosphere are tested in HPTGA. • HPCP char from same temperature are tested in HPCP. • Influence of pyrolysis pressure on coal swelling, char reactivity and high temperature reaction mechanism. High Pressure Char Work Underway • PreliminaryHigh Pressure Pyrolysis Test • Pitt 8 coal pyrolyzed at 1,5,10,15 atm in HPDT (High Pressure Drop Tube); Chars collected. • Chars tested for elemental composition, mass-loss rate, high-pressure reactivity. • High-pressure flat-flame-burner developed and used. • Pitt 8 & Knife River Lignite coal pyrolyzed at 1,5,10 atm in HPFFB (High-Pressure Flat-Flame-Burner); chars collected and analyzed. 1 atm drop tube char 1 atm TGA 5 atm drop tube char 5 atm TGA 10 atm drop tube char 10 atm TGA 15 atm drop tube char 15 atm TGA Why? char density = f(Ptot, heating rate) intrinsic char reactivity = f(Tfinal, heating rate) • Conclusions • Initial tests show that char combustion activation energy increases with pyrolysis pressure. • Oxygen order is constant at 0.9, which is high compared to other research. • Rate constant decreases with increasing pressure. High-Pressure Flat Flame Burner • Research Plan • Find the influence of pressure during pyrolysis on the properties of the resulting chars. • High-temperature, high-pressure char reactivities will be tested in HPFFB, then compared to HPTGA intrinsic rates to find the influence of pressure on char combustion kinetics. • Test results will be used to develop the CBK model (Carbon Burnout Kinetic Model) . • High heating rate. • Controllable reaction residence time. • Capable of pyrolysis and combustion tests by changing feed gas equivalence ratio. • Has been tested up to 10atm, 1300oC