Impact of oxy-fuel combustion gases on mercury retention in activated carbons from a macroalgae waste: Effect of water

• Published in: Chemosphere (Oxford) Vol. 125; pp. 191 - 197
• Main Authors: Lopez-Anton, M.A., Ferrera-Lorenzo, N., Fuente, E., Díaz-Somoano, M., Suarez-Ruíz, I., Martínez-Tarazona, M.R., Ruiz, B.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-04-2015
• Subjects: Activated carbon; Activated carbons; Adsorption; Algae; Atmospheres; Biomass; Charcoal - chemistry; Coal - analysis; Combustion; Environmental Pollution - prevention & control; Flue gases; Gases - analysis; Industrial macroalgae waste; Mercury; Mercury (metal); Mercury - chemistry; Nitrogen - chemistry; Oxidation-Reduction; Oxy-combustion; Oxygen - chemistry; Seaweed - chemistry; Wastes; Water - chemistry; Water vapor; Industrial macroalgae waste; Mercury; Activated carbons; Oxy-combustion
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2014.12.057

•Activated carbons obtained from algae industry waste may retain mercury.•Mercury retention is favored by the presence of O2 in absence of other gases.•High percentage of mercury oxidation but no retention in oxy-combustion conditions.
The aim of this study is to understand the different sorption behaviors of mercury species on activated carbons in the oxy-fuel combustion of coal and the effect of high quantities of water vapor on the retention process. The work evaluates the interactions between the mercury species and a series of activated carbons prepared from a macroalgae waste (algae meal) from the agar–agar industry in oxy-combustion atmospheres, focussing on the role that the high concentration of water in the flue gases plays in mercury retention. Two novel aspects are considered in this work (i) the impact of oxy-combustion gases on the retention of mercury by activated carbons and (ii) the performance of activated carbons prepared from biomass algae wastes for this application. The results obtained at laboratory scale indicate that the effect of the chemical and textural characteristics of the activated carbons on mercury capture is not as important as that of reactive gases, such as the SOx and water vapor present in the flue gas. Mercury retention was found to be much lower in the oxy-combustion atmosphere than in the O2+N2 (12.6% O2) atmosphere. However, the oxidation of elemental mercury (Hg0) to form oxidized mercury (Hg2+) amounted to 60%, resulting in an enhancement of mercury retention in the flue gas desulfurization units and a reduction in the amalgamation of Hg0 in the CO2 compression unit. This result is of considerable importance for the development of technologies based on activated carbon sorbents for mercury control in oxy-combustion processes.