# Mercury Adsorption and Oxidation Performance of an Iron-Based Oxygen Carrier during Coal Chemical Looping Process

## TL;DR

This study explores how an iron-based oxygen carrier affects mercury during coal combustion and gasification processes.

## Contribution

The study identifies three mechanisms—enhanced mercury release, adsorption, and oxidation—by an iron-based oxygen carrier.

## Key findings

- The iron-based oxygen carrier enhances mercury release from coal and oxidizes Hg0 to Hg2+.
- Mercury adsorption decreases with increasing temperature, but oxidation increases.
- The oxygen carrier physically absorbs Hg0 and Hg2+ and forms complexes with mercury.

## Abstract

During chemical looping combustion (CLC) and chemical looping gasification (CLG) of coal, the release, migration, and speciation of mercury in coal are significantly influenced by oxygen-carrier materials; however, the underlying mechanism remains inadequately addressed. In this work, the effect of a typical iron-based oxygen carrier on the release behavior of mercury from a bituminous coal and a lignite was investigated based on the Ontario-Hydro method. It is found that the effect of the iron-based oxygen carrier is attributed to three aspects: the enhanced release rate of mercury from coal, the adsorption of the released mercury, and the oxidization of gaseous Hg0 into Hg2+. With the increasing temperature, the adsorbance of mercury by the iron-based oxygen carrier decreases, while the oxidation of mercury enhances. Even at 900 °C, the adsorbance of mercury by the oxygen carrier remained at 0.1687 g/g, with a relative content of Hg2+ at 22.55%. Additionally, it was observed that iron-based oxygen carriers can physically absorb both Hg0 and Hg2+, while chemisorption refers to complex-compound formation between the iron-based oxygen carrier and mercury.