The Effect of Pressure on Ash Formation during Pulverized Coal Combustion

A bituminous coal with a size faction of 63−90 μm was combusted under oxidizing atmosphere (air) in a drop tube furnace (DTF) and a pressurized drop tube furnace (PDTF) at a gas temperature of 1573 K and pressures of 0.1, 0.5, 1.0, and 1.5 MPa. Ash generated at high pressure was found to be much finer than ash generated at low pressure due to the differences in char structure. Pressure influcences ash formation by its effect on the structure of char particles after devolatilisation. Char samples produced at high pressure have higher proportions of porous char particles which fragment to form finer ash particles. This study confirms and elaborates upon previous studies relating the structure and morphologies of char to ash formation.

[1]  Boyd F. Edwards,et al.  Percolation model for simulation of char oxidation and fragmentation time-histories , 1987 .

[2]  R. P. King,et al.  Determination of the distribution of size of irregularly shaped particles from measurements on sections or projected areas , 1982 .

[3]  L. Baxter,et al.  The release of iron during the combustion of Illinois No. 6 coal , 1992 .

[4]  A. A. Boni,et al.  Factors influencing the transformation of minerals during pulverized coal combustion , 1990 .

[5]  Terry Wall,et al.  An experimental study on the effect of system pressure on char structure of an Australian bituminous coal , 2000 .

[6]  T. Fletcher,et al.  Release of inorganic material during coal devolatilization , 1997 .

[7]  R. J. Quann,et al.  Mineral matter and trace-element vaporization in a laboratory-pulverized coal combustion system. , 1982, Environmental science & technology.

[8]  J. Mathews,et al.  A pressurized drop-tube furnace for coal reactivity studies , 1998 .

[9]  Terry Wall,et al.  A char morphology system with applications to coal combustion , 1990 .

[10]  Terry Wall,et al.  Ash liberation from included minerals during combustion of pulverized coal: The relationship with char structure and burnout , 1999 .

[11]  E. Raask.  Creation, capture and coalescence of mineral species in coal flames , 1984 .

[12]  T. Wall,et al.  An Investigation of Factors Affecting the Physical Characteristics of Flyash Formed in a Laboratory Scale Combustor , 1986 .

[13]  Terry Wall,et al.  Mineral matter in coal and the thermal performance of large boilers , 1979 .

[14]  Jouni P. Hämäläinen,et al.  Pressurized Pulverized Fuel Combustion in Different Concentrations of Oxygen and Carbon Dioxide , 1996 .

[15]  Jaakko Saastamoinen,et al.  Effects of Pressure and Oxygen Concentration on the Combustion of Different Coals , 1999 .

[16]  L. Baxter.  The evolution of mineral particle size distributions during early stages of coal combustion , 1990 .

[17]  Adel F. Sarofim,et al.  The Physical Transformation of the Mineral Matter in Pulverized Coal Under Simulated Combustion Conditions , 1977 .