Will mixing rule or chemical reactions dominate the ash behavior of biomass mixtures in combustion processes on laboratory and pilot scales?

Thermodynamic equilibrium approach to predict the inorganic interactions of ash from biomass and their mixtures: A critical assessment

“…Afterward, each biomass pellet and the ground mixtures were ashed at 550℃ for 2h in natural air with the same procedure as detailed in Atallah et al [26]. This step at 550°C removed all organic oxygen and hydrogen (along with organic nitrogen and part of chlorine) while preserving the majority of the other elements.…”

“…This step at 550°C removed all organic oxygen and hydrogen (along with organic nitrogen and part of chlorine) while preserving the majority of the other elements. Then 0.5 g of ash from each mixture and single biomasses were compressed as ash chips with the same procedure described in Atallah et al [26] to favor the contact between the inorganic ash particles.…”

“…Two prediction approaches were used as done previously [9,25]: a simplified one using phase diagram calculations and a more sophisticated one called global simulation. Both approaches were then compared to experimental results on multiple ash samples already checked to be at equilibrium (from single biomass and mixtures) [26]. This aimed to evaluate the thermodynamic approach prediction capabilities using the most recent databases and suggest improvements.…”

Evaluation on thermal pyrolysis of biomass straw waste: Focusing aspects of products yields, syngas emissions and solid products characterization

“…Moreover, biomass generally contains a large amount of alkali/alkali earth metals (AAEMs, i.e., K, Na, Ca, Mg) together with a considerable content of nonmetallic elements (Cl, S, P, and Si). Failure to remove these condensed alkali compounds from the downstream syngas can probably cause severe ash fouling, slagging, and corrosion problems 25,26 . More specifically, the elements K, Na, S, Cl, P, Si, Al, Ca, Mg, and Fe are inclined to involve in the reactions facilitating agglomeration and fusion, hence probably resulting in operating problems in the reactors and eventually plant shutdown.…”

“…Failure to remove these condensed alkali compounds from the downstream syngas can probably cause severe ash fouling, slagging, and corrosion problems. 25,26 More specifically, the elements K, Na, S, Cl, P, Si, Al, Ca, Mg, and Fe are inclined to involve in the reactions facilitating agglomeration and fusion, hence probably resulting in operating problems in the reactors and eventually plant shutdown. Thus, in addition to better understanding the pyrolysis behaviors of biomass, an in-depth investigation of the physicochemical characterization of ash in the solids together with the transformation behaviors of the inorganic matters at different pyrolysis temperatures could be helpful to provide more valuable information about the physical and chemical phenomena occurring in the gasification process.…”