Effect of HTC and Water-Leaching of Low-Grade Biomasses on the Release Behavior of Inorganic Constituents in a Calcium Looping Gasification Process at 650 °C

The release of alkali metals (K, Na) and nonmetals (S, Cl) during a calcium looping (CaL) gasification process of waste derived-hydrochars, water-leached samples, and CaO-biomass blends was investigated. Special attention was paid to biomasses that are not particularly promising for gasification requirements but have a large occurrence in Europe, including Grape Bagasse, Organic Fraction of Municipal Solid Waste (OFMSW), Green Waste, and Out-of-use woods from construction debris and discarded furniture. The release experiments were performed at 650 °C in a flow channel reactor to investigate the behavior of inorganic trace substances. Hot-gas analysis was performed by Molecular Beam Mass Spectrometry (MBMS). Thermodynamic equilibrium calculations via FactSage indicate H₂S, carbonyl sulfide (COS), KCl, NaCl, and HCl as the main inorganic impurities. Thus, the focus of the experiments was placed on these species. It was found that the concentrations of trace elements released during gasification at 650 °C, such as H₂S, SO₂, KCl, and NaCl, are hardly affected by intense water-leaching. In contrast, carbonaceous materials from hydrothermal carbonization exhibit a higher concentration of trace potassium substances (K, KCl, and K₂Cl⁺). When biomass samples are combined with CaO, the total amount of inorganic trace compounds (K, Na, and S compounds) in the resulting syngas could be decreased.