Variation of the pore structure of coal chars during gasification

Effect of operating parameters on coal gasification

“…The reactivity of coal after certain temperature can be decreased because of heat treatment which promotes closing of pores. Closing of pores caused due to presence of large molecules, compressing disorganized carbon, cross linking and collapsing of pores at higher temperature due to plasticity of char (Feng and Bhatia 2003). But in contrast to above discussion, Feng and Bhatia (2003) also reported that with the increase in heat treatment time and temperature, volume of closed pores increases and there is no change in size of various pores with carbon conversion because shrinkage occurs maintaining the same distance between crystalline structures.…”

“…Closing of pores caused due to presence of large molecules, compressing disorganized carbon, cross linking and collapsing of pores at higher temperature due to plasticity of char (Feng and Bhatia 2003). But in contrast to above discussion, Feng and Bhatia (2003) also reported that with the increase in heat treatment time and temperature, volume of closed pores increases and there is no change in size of various pores with carbon conversion because shrinkage occurs maintaining the same distance between crystalline structures. In contrast to above results, Miura et al (1989) and Hurt et al (1991) have reported that the pore structure is not a factor which controls the gasification reaction rate of highly reactive char.…”

“…Kiihl et al (1992) reported that steam gasification produces a less microporous structure than CO 2 gasification. Feng and Bhatia (2003) reported that in air gasification pore structure development is different from CO 2 gasification. During CO 2 gasification, volume and surface area of small micropores increases very dramatically as gasification reaction progresses whereas in air gasification volume and surface area of small micropores does not change appreciably with carbon conversion after a particular extent of carbon conversion (Feng and Bhatia 2003).…”

Evolution of nanoporosity in organic-rich shales during thermal maturation

“…Carbon dioxide adsorption at 273.15 K is often the preferred choice to investigate the microporosity of carbonaceous materials, since the ambient temperature promote the gas diffusion in the microporous system compared to the low temperature (77 K) used in nitrogen adsorption [26]. However, a limitation of CO 2 adsorption at 273.15 K is that CO 2 molecular cannot fill larger micropores and also may have additional interactions with organic matter [26,27]. With more attention focused on the shale pore systems, nitrogen and carbon dioxide adsorption techniques have widely been introduced to study the pore characteristics of shales [5,[13][14][15][16][17].…”

Changes in total active centres on particle surfaces during coal pyrolysis, gasification and combustion

“…(12)) for the temperature range of 1250-1750 K, which was further modified by Visona and Stanmore (1996) with a solid substance volume parameter of the coal char particle in relation to its total volume. In their study on pore structure changes during coal char gasification in air and carbon dioxide, at temperatures 653 K and 1073 K, Feng and Bhatia (2003) also applied Equation (12). Hurt et al (1991) and Sotirchos (1987) provided their own equations for porosity changes during the gasification process, in which changes depended on the changes in pore and particle diameters.…”