Determination of the forms of calcium present in coal chars by Ca K-edge XANES with Synchrotron Radiation

TL;DR

This study uses Ca K-edge XANES spectroscopy to identify calcium compounds in coal chars after pyrolysis, revealing different calcium forms depending on the additive used and formation of carboxyl calcium.

Contribution

It introduces the application of Ca K-edge XANES spectroscopy to determine calcium speciation in coal chars, highlighting differences based on calcium additives.

Findings

Ca(OH)2 and CaSO4 are present in both types of Ca-added chars.

CaS and CaO only appear in Ca(OH)2-added chars.

Carboxyl calcium forms during pyrolysis in both cases.

Abstract

This work is concerned with the Ca transformations during the pyrolysis of Ca(OH)2 or CaCO3-added coals. Ca K-edge X-ray absorption near edge structure (XANES) spectroscopy was applied to determine the forms of Ca in chars prepared from the pyrolysis of Ca-added coal. Results showed that Ca(OH)2 and CaSO4 existed in both the Ca(OH)2-added chars and the CaCO3-added chars, while CaS and CaO only existed in the chars prepared from the Ca(OH)2-added coal. Moreover, it was found that carboxyl Ca was formed during pyrolysis for either the Ca(OH)2-added coal or the CaCO3-added coals.