The influence of a two-step leaching pretreatment on the steam gasification properties of cornstalk waste.

Knowing the effect of specific alkali and alkali earth metals forms is vital for the high-efficient gasification of biomass. This work developed a two-step leaching method to pretreat cornstalk, dividing the inorganic metals into water-soluble (K+, 74 wt%), acid-soluble (Al3+, Ca2+, Fe2+, etc) and insoluble (Si4+) substances. The water-soluble K+ was mainly in KCl form, the acid-soluble metals were removed in phosphates and sulfates forms. The rapid gasification properties of raw material, water leaching residue and acid leaching residue indicated that KCl was the key factor to enhance the hydrogen yield and gasification efficiency. Apart from K+, the alkali earth metals (Ca2+, Mg2+) also had a little catalytic effect on producing hydrogen. When the feedstock was out of metal cations, the syngas was mainly composed of CO. The basic ions to acid ions ratio was linearly related to the syngas quality, which could conduct the flux additives.