Self-ignition resistant thermally-activated carbon
Thermally-activated cellulosic-based carbon is rendered more thermally stable by exposure to a halogen and/or a halogen-containing compound. Such treated cellulosic-based carbon 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 thermally-activated cellulosic-based carbon that has been exposed to a halogen and/or a halogen-containing compound, has an ash content of 10 to 15 wt % and that has at least one of the following:
(i) a temperature of initial energy release that is greater than the temperature of initial energy release for the same thermally-activated cellulosic-based carbon without the halogen and/or halogen-containing compound exposure;
(ii) a self-sustaining ignition temperature greater than the self-sustaining ignition temperature for the same thermally-activated cellulosic-based carbon without the halogen and/or halogen-containing compound exposure; and
(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 without the halogen and/or halogen-containing compound exposure.
2. The thermally-activated cellulosic-based carbon 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.
3. The thermally-activated cellulosic-based carbon of claim 1 wherein the thermally-activated cellulosic-based carbon that has been exposed to a halogen or halogen-containing compound contains from about 2 to about 20 wt % halogen, the wt % being based on the total weight of the thermally-activated cellulosic-based carbon that had been exposed to the halogen and/or the halogen-containing compound.
4. A process for enhancing the thermal stability of a thermally-activated cellulosic-based carbon, which process comprises exposing the thermally-activated cellulosic-based carbon to a halogen and/or a halogen-containing compound at a temperature and for a time sufficient so that thermally-activated cellulosic-based carbon that has been exposed to the halogen and/or the halogen-containing compound, has an ash content of 10 to 15 wt % and 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 halogen and/or halogen-containing compound exposure;
(ii) a self-sustaining ignition temperature greater than the self-sustaining ignition temperature for the same thermally-activated cellulosic-based carbon prior to the halogen and/or halogen-containing compound exposure; and
(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 halogen and/or halogen-containing compound exposure.
5. The process of claim 4 wherein the halogen and/or halogen-containing compound comprises bromine, chlorine, fluorine, iodine, ammonium bromide, other nitrogen-containing halogen salts, or calcium bromide.
6. The process of claim 4 wherein the thermally-activated cellulosic-based carbon is exposed to the halogen and/or the halogen-containing compound at a temperature from 82 to 105° C. and for a period of time within the range of from 0.1 to 3 seconds.
7. A halogen and/or halogen-containing compound exposed, thermally-activated cellulosic based carbon that contains from about 2 to about 20 wt % halogen, has an ash content of 10 to 15 wt %, is prepared absent contact with acid, water or a combination thereof and has at least one of the following:
(i) a temperature of initial energy release that is greater than the temperature of initial energy release for the same thermally-activated cellulosic based carbon prior to the halogen and/or halogen-containing compound exposure,
(ii) a self-sustaining ignition temperature greater than the self-sustaining ignition temperature for the same thermally-activated cellulosic-based carbon prior to the halogen and/or halogen-containing compound exposure; and
(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 halogen and/or halogen-containing compound exposure.
8. The thermally-activated cellulosic-based carbon of claim 7 wherein the halogen and/or halogen-containing compound comprises bromine, chlorine, fluorine, iodine, ammonium bromide, other nitrogen-containing halogen salts, or calcium bromide.