Inhibition of steam gasification of char by volatiles in a fluidized bed under continuous feeding of a brown coal

Changes in char reactivity due to char–oxygen and char–steam reactions using victorian brown coal in a fixed-bed reactor

“…The increase in coal feeding rates resulted in high concentration of volatiles inside the reaction zone. The radicals (especially H radicals) from interactions between volatiles and coal could occupy reactive sites on char surface, which was believed to be the main reason for inhibiting the char conversion during the gasification in steam [14][15][16][17]. For the gasification with O 2 as gasifying agent in this study, the actual role of the volatile-char interaction on char conversion will be further discussed later.…”

“…For example, it was found that volatile-char interaction was one of the most important factors affecting almost every aspect of gasification using Victorian brown coal [3,[14][15][16][17][18][19][20][21]. The results also implied that gasifying agents (steam, oxygen and CO 2 ) might react with Victorian brown coal on different reactive sites in a fluidised-bed reactor [15,22,23].…”

“…cience about Victorian brown coal gasification has been intensively studied, particularly by Monash University in Australia [9][10][11][12][13][14][15][16][17][18][19][20][21]. For example, it was found that volatile-char interaction was one of the most important factors affecting almost every aspect of gasification using Victorian brown coal [3,[14][15][16][17][18][19][20][21].…”

Modeling of gas/particle flow in coal conversion with a drop tube reactor using a lumped kinetic model accounting volatiles–char interaction

“…Six global chemical reactions were considered in the simulation. Two homogeneous reactions (5)(6) and four heterogeneous reactions (7-10) were considered according to the developed lumped kinetic model, as follows: The boundary conditions for the numerical simulation are shown in the Supplementary Information. In addition, the convergence criteria are set in a transient fashion with a time step of 0.001 s and residuals for continuity less than 10 −4 , energy less than 10 − 6 , and all species less than 10 −6 .…”

“…Tar is an undesirable product of gasification because of various problems associated with condensation, formation of tar aerosols, and polymerization to form more complex structures, which can impede and damage the process equipment, as well as the engines and turbines used in product gas consumption [4]. Also, other volatile materials generated during coal gasification, such as light hydrocarbon gases and hydrogen may strongly inhibit char gasification [5][6][7]. Therefore, the development of technologies and methods for the reduction or removal of tar has received substantial attention in recent years [4,8,9].…”