Performance of calcium-added molten alkali carbonates for high-temperature desulfurization from pyrolysis gases. (January 2020) - Hu, Hongyun
Abstract: Co-pyrolysis of biomass with oxygen-lean polymer waste is a promising way to improve both quantity and quality of the derived oil. However, the release of sulfur contaminants causes serious adverse effects on the utilization of the derived oil. In order to promote the efficient and economic utilization of the derived products, the high-temperature desulfurization was conducted in this study using a ternary molten carbonates (Li2 CO3 –Na2 CO3 –K2 CO3 ). And the effects of added Ca 2+ or Cl − /SO4 2− on the desulfurization were estimated. The results demonstrated that the molten carbonates showed high efficiency in the removal of H2 S/COS/SO2 at 500 °C. Alkali metals competitively reacted with H2 S/COS to form various sulfides and sulfur species in the cooled products were probably determined by the crystallization processes. Besides, H2 S removal was stimulated by adding CaCO3 and the formed CaS was precipitated from the molten salts. The addition of Cl − /SO4 2− changed the ion distribution characteristics of the molten salts and had slightly adverse effects on the removal of H2 S. In contrast, SO2 removal was hardly affected while COS removal efficiency was decreased after adding Ca 2+ or Cl − /SO4 2− . Anyway, the added Ca 2+ favored the recovery of sulfur as well as the regeneration of spent molten carbonates. Graphical abstract: Image 1 Highlights: Molten carbonates showed good performance for gaseous sulfur removal at 500 °C. H2 S removal was stimulated by adding CaCO3 in the molten alkali metals carbonates. The addition of Ca-compounds had slight undesirable effect on the removal of COS. Cl − /SO4 2− introduction slightly suppressed H2 S or COS removal by the molten salts. Ca 2+ addition favored the recovery of sulfur and the regeneration of spent salts.