Nowok, JW
1991
Physicochemical Effects Influencing the Measurements of Interfacial Surface Tension of Coal Ashes
Nowok, J.W.; Bieber, J.A.; Benson, S.A. and Jones, M.L.
Fuel, 70:951-956, 1991. Funded by Morgantown Energy Technology Center.
The sessile drop technique has been used to determine the interfacial surface tension of Beulah, Illinois no. 6 and Pittsburgh no. 8 coal ash derived slags under various atmospheres. The physical and chemical effects that influence interfacial surface tension during heating cool slags are discussed. The results indicate that interfacial surface tension measurements obtained below the temperature of critical viscosity (Tcv) were lower than those determined above Tcv. This effect was attributed to a non-equilibrium state of surface tension due to the random distribution of surface active phases in the slag and higher polymerization of silicate structure. The interfacial surface tensions did not vary significantly with temperatures above Tcv.
1990
Sintering Behavior and Strength Development in Various Coal Ashes
Nowok, J.W.; Benson, S.A.; Jones, M.L. and Kalmanovitch, D.P.
Fuel, 1990 (In press). Funded by US Department of Energy.
Sintering, crystallization, and mechanical properties of six coal ashes are being studied to obtain an understanding of ash deposit and agglomerate formation in combustion and gasification systems. Results show that viscous sintering is accomplished by neck growth between particles, shrinkage of closed pores, and/or by diffusion of slag constituents in a liquid film along the grain surfaces. These processes are dependent on temperature, atmosphere, and ash composition. In addition, studies show that the strength of sintered pellets produced from crystallized Beulah lignite ash are weaker than those produced from the amorphous form of the ash. Further, the amorphous form sintered in a CO/CO2 atmosphere is not as strong as the amorphous form sintered in air. Criteria are given for the relationship between compressive strength of sintered coal fly ashes and their activity in the sintering process measured by means of viscosity and surface tension.
Nowok, JW
1991
Physicochemical Effects Influencing the Measurements of Interfacial Surface Tension of Coal Ashes
Nowok, J.W.; Bieber, J.A.; Benson, S.A. and Jones, M.L.
Fuel, 70:951-956, 1991. Funded by Morgantown Energy Technology Center.
The sessile drop technique has been used to determine the interfacial surface tension of Beulah, Illinois no. 6 and Pittsburgh no. 8 coal ash derived slags under various atmospheres. The physical and chemical effects that influence interfacial surface tension during heating cool slags are discussed. The results indicate that interfacial surface tension measurements obtained below the temperature of critical viscosity (Tcv) were lower than those determined above Tcv. This effect was attributed to a non-equilibrium state of surface tension due to the random distribution of surface active phases in the slag and higher polymerization of silicate structure. The interfacial surface tensions did not vary significantly with temperatures above Tcv.
1990
Sintering Behavior and Strength Development in Various Coal Ashes
Nowok, J.W.; Benson, S.A.; Jones, M.L. and Kalmanovitch, D.P.
Fuel, 1990 (In press). Funded by US Department of Energy.
Sintering, crystallization, and mechanical properties of six coal ashes are being studied to obtain an understanding of ash deposit and agglomerate formation in combustion and gasification systems. Results show that viscous sintering is accomplished by neck growth between particles, shrinkage of closed pores, and/or by diffusion of slag constituents in a liquid film along the grain surfaces. These processes are dependent on temperature, atmosphere, and ash composition. In addition, studies show that the strength of sintered pellets produced from crystallized Beulah lignite ash are weaker than those produced from the amorphous form of the ash. Further, the amorphous form sintered in a CO/CO2 atmosphere is not as strong as the amorphous form sintered in air. Criteria are given for the relationship between compressive strength of sintered coal fly ashes and their activity in the sintering process measured by means of viscosity and surface tension.