Gasification of coal char in H2O/CO2 atmospheres: Evolution of surface morphology and pore structure

Effects of Porous Structure Development and Ash on the Steam Gasification Reactivity of Biochar Residues from a Commercial Gasifier at Different Temperatures

“…As shown in Figure 6a,b the total pore volume (V total ) and the total specific surface area (S total ) increases 1.3-3.1 and 2.0-5.3 times, respectively, with conversion until a value of approximately 70% at all temperatures, indicating a formation of new pores, as a result of steam-carbon reaction. Similar results are also reported in other studies [17,22]. S total , as well as V total , start to decrease after this point.…”

“…Klinghoffer et al [36] observed that the agglomeration is clearly visible at 1000 °C. The agglomerates are formed at higher conversion (green triangle) due to the increased mineral content during char consumption, which is analogous to the results obtained by Yonghui et al [22] while investigating the morphology of chars exposed in steam atmosphere.…”

“…The higher reaction rate (i.e., char reactivity) may be attributed to a change in morphology [12] or a change in textural properties due to the formation of a larger pore volume at high heating rates, mainly consisting of mesopores and macropores, compared to a lower pore volume of mainly micropores at a low heating rates [13]. Textural biomass-char properties are also significantly changed during the gasification process, expressed as an evident increase in porosity and surface area [14][15][16][17][18][19][20][21][22]. Most studies on pore structure development of biomass char use CO 2 as the gasification agent [14][15][16][17]22] and only a few studies focus on char steam gasification, especially wood-derived chars, at different temperatures [18,19,23].…”

“…It is evident that the reactivity of a char differs depending on the conditions present in a real-scale gasification plant and also between chars produced in the laboratory and real chars. Most studies investigating steam biomass char gasification relate the observed reactivity to char structure development [17,19,20,22] or ash content [9,21,[42][43][44][45][46] individually and not in synergy. Mechanistic studies on how both parameters contribute to the char reactivity of real biomass semi-char, during its transformation under steam gasification conditions, are important to enable the development of kinetic models.…”

Impacts of char structure evolution and inherent alkali and alkaline earth metallic species catalysis on reactivity during the coal char gasification with CO2 /H2 O

“…The presence of H 2 O promotes the diffusion of CO 2 into the internal pores of char and thereby contributes to the development of pore structure. Our previous alternately CO 2 /H 2 O gasification experiments established that the channels generated by H 2 O facilitate CO 2 entry to further produce pores . We can observe from Figure B that when the gasification temperature was 900°C, CO 2 /H 2 O‐50%‐char has a higher microporous adsorption capacity and similar pore size distribution as compared with H 2 O‐50%‐char.…”