Brominated sorbents for removing mercury from emissions produced during fuel combustion
Activated cellulosic-based carbon is rendered more thermally stable by exposure to water or aqueous acid, and optionally, to a halogen and/or a halogen-containing compound. Such treated cellulosic-based carbon has enhanced thermal properties and is suitable for use in mitigating the content of hazardous substances in flue gases, especially flue gases having a temperature within the range of from about 100° C. to about 420° C.
1. A process for enhancing the thermal stability of a thermally-activated cellulosic-based carbon, which process comprises extracting the thermally-activated cellulosic-based carbon with a composition comprising water or an aqueous acid, and halogenating the extracted thermally-activated cellulosic-based carbon with halogen and/or halogen-containing compound at a temperature from about 82 to about 105° C. for a period of time within the range of from about 0.1 to about 3 seconds, such that the extracted thermally-activated cellulosic-based carbon has at least one of the following: (i) a temperature of initial energy release greater than the temperature of initial energy release for the same thermally-activated cellulosic-based carbon prior to the extraction; (ii) a self-sustaining ignition temperature greater than the self-sustaining ignition temperature for the same thermally-activated cellulosic-based carbon prior to the extraction; or (iii) an early stage energy release value that is less than the early stage energy release value for the same thermally-activated cellulosic-based carbon prior to the extraction.
2. The process of claim 1 wherein the halogen and/or halogen containing compound comprises bromine, chlorine, fluorine, iodine, ammonium bromide, other nitrogen-containing halogen salts, or calcium bromide.