Abstract
In order to examine the influence of the coal-included minerals on the CO2 sorption characteristics of Ca-based sorbents during hydrogen production through sorption-enhanced coal gasification (HyPr-RING process) pulverized bituminous coal (Taiheiyo coal) samples with diameter ranges of 38-75 µm and 180-250 µm were gasified with high-pressure steam in the presence of Ca-based CO2 sorbents at 873 and 973 K and at holding times ranging from 0 to 120 min in a laboratory-scale fixed-bed reactor. Local scanning electron microscopy-energy-dispersive X-ray analysis of the solid residues obtained under different conditions showed that some constituents of the coal-included minerals, such as Si and Al, were involved in the sorbent particles. The solid-solid reaction between the Ca-based sorbents and coal-included minerals became significant at the higher temperature and at longer residence time, which causes substantial decrease the CO2-sorption ability of the sorbents. However, when a holding time of less than 10 min was employed, the solid-solid reaction between the minerals and the sorbents seemed to be suppressed, even at 973 K, because the rate of formation of inorganic compounds through the solid-solid reaction was not fast. Our results indicate that the holding time of the feedstock in the reactor should be shortened to avoid deactivation of the Ca-based sorbents during high-pressure steam gasification.
