Limestone particle attrition and size distribution in a small circulating fluidized bed

Abstract Limestone particle attrition was investigated in a small circulating fluidized bed reactor at temperatures from 25 to 850 °C, 1 atm pressure and superficial gas velocities from 4.8 to 6.2 m/s. The effects of operating time, superficial gas velocity and temperature were studied with fresh limestone. No calcination or sulfation occurred at temperatures ⩽580 °C, whereas calcination and sulfation affected attrition at 850 °C. Increasing the temperature (while maintaining the same superficial gas velocity) reduced attrition if there was negligible calcination. Attrition was high initially, but after ∼24 h, the rate of mass change became constant. The ratio of initial mean particle diameter to that at later times increased linearly with time and with (Ug − Umf)2, while decreasing exponentially with temperature, with an activation energy for fresh limestone of −4.3 kJ/mol. The attrition followed Rittinger’s surface theory [Beke B. Comminution. Budapest: Akademiai Kiado, 1964; Ray YC, Jiang TS, Wen CY. Particle attrition phenomena in a fluidized bed. Powder Technol 1987a; 49:193–206]. The change of surface area of limestone particles was proportional to the total excess kinetic energy consumed and to the total attrition time, whereas the change of surface area decreased exponentially with increasing temperature. At 850 °C, the attrition rate of calcined lime was highest, whereas the attrition rate was lowest for sulfated particles. When online impact attrition was introduced, the attrition rate was about an order of magnitude higher than without impacts.

[1]  John G. Yates,et al.  Hydrodynamic influences on particle breakage in fluidized beds , 1990 .

[2]  John R. Grace,et al.  Sulfation and reactivation characteristics of nine limestones , 2000 .

[3]  T. Jiang,et al.  Particle population model for a fluidized bed with attrition , 1987 .

[4]  T. Shimizu,et al.  Effect of attrition on SO2 capture by limestone under pressurized fluidized bed combustion conditions: comparison between a mathematical model of SO2 capture by single limestone particle under attrition condition and SO2 capture in a large-scale PFBC , 2001 .

[5]  Ming-Yen Wey,et al.  Influence of hydrodynamic parameters on particle attrition during fluidization at high temperature , 2005 .

[6]  J. Bridgwater,et al.  A review of attrition and attrition test methods , 1987 .

[7]  Tim C. Keener,et al.  Attrition of Lime Sorbents during Fluidization in a Circulating Fluidized Bed Absorber , 1993 .

[8]  C. Y. Wen,et al.  Particle attrition phenomena in a fluidized bed , 1987 .

[9]  M. Wey,et al.  Effects of high temperature and combustion on fluidized material attrition in a fluidized bed , 2003 .

[10]  J. Grace,et al.  Enhancement of the sulfur capture capacity of limestones by the addition of Na2CO3 and NaCl. , 2001, Environmental science & technology.

[11]  Oliver Lindqvist,et al.  Direct sulfation of limestone at elevated pressures , 2000 .

[12]  Fabrizio Scala,et al.  Comminution of limestone during batch fluidized‐bed calcination and sulfation , 1997 .

[13]  Tim C. Keener,et al.  Attrition and changes in particle size distribution of lime sorbents in a circulating fluidized bed absorber , 1996 .

[14]  P. Salatino,et al.  Attrition of sorbents during fluidized bed calcination and sulphation , 2000 .

[15]  Mi-ran Kim,et al.  Enhancement of combustion efficiency with mixing ratio during fluidized bed combustion of anthracite and bituminous blended coal , 2002 .

[16]  İrfan Ar,et al.  Sulfation reaction between SO2 and limestone : application of deactivation model , 2002 .

[17]  John R. Grace,et al.  Study of limestone particle impact attrition , 2007 .

[18]  Wen-ching Yang.  Handbook of Fluidization and Fluid-Particle Systems , 2003 .

[19]  K. Dam-Johansen,et al.  High-temperature reaction between sulphur dioxide and limestone—I. Comparison of limestones in two laboratory reactors and a pilot plant , 1991 .

[20]  Masato Tanaka,et al.  A simplified model of SO2 capture by limestone in 71 MWe pressurized fluidized bed combustor , 2002 .

[21]  A. D. Benedetto,et al.  Modelling attrition of limestone during calcination and sulfation in a fluidized bed reactor , 1998 .