Intraparticle mass transfer in coal pyrolysis

Abstract

Intraparticle mass transfer in coal pyrolysis is described by ternary diffusion and viscous flow, in conjunction with a simple pore model to predict concentration profiles for gases and tar. At low pressures, product yields depend on particle size only, while at high pressures they depend on pressure and particle size. Limited experimental data from a subbituminous coal confirm these trends. Data from a bituminous coal show different trends, as expected from the drastic changes the pore structure undergoes during pyrolysis.

Kinetic Behavior of Torrefied Biomass in an Oxidative Environment

“…6 is shown in Figure 5, where is increasing as mchar is decreasing. This self-acceleration, however, is much smaller than that of a random-pore kinetics 35 indicating that the internal pore surfaces have only a limited importance in the char burn-off kinetics of these samples. Table 6 4.…”

Study of Activation of Coal Char

“…The proper design of combustion facilities demands that the kinetics of combustion be understood. Much combustion literature suggests that char reactivities should be expressed on a surface area basis [2], although small char micropores might not be fully utilized during oxidation or gasification [e.g., [3][4][5][6][7][8]. Many models have been proposed to describe development of char surface areas with burn-off [9][10][11][12][13][14][15], but many features need further clarification -e.g., different patterns of porosity development are observed in the same char, in different gases, even when rates of reaction are set to be identical [7,16].…”

Study of Activation of Coal Char

“…This may be verified by comparing the ordinate scales of Figures 1, 3 Focusing for the moment on the representation of data involving normalization by m 0 (Figures 1, 3, and 5), it appears that over a wide range of burn-off, the rates in NO and CO 2 are quite constant with burn-off, whereas the rate in O 2 increases and decreases dramatically. This is emphasized by the comparison in Figure 7, which illustrates the change in rate with conversion in The behavior seen in the case of oxygen is often reported in the literature [9][10][11][12][13]. The general interpretation is that the surface area for reaction initially increases with burn-off, and then is lost as a result of pore coalescence.…”