Enhanced Fly Ash Collection
A process of enhancing fly ash collection without adding SO 3 to a flue gas can include providing a flue gas that includes fly ash and combustion gases from a coal fired boiler; injecting into the flue gas a particulate resistivity aid; and then collecting the fly ash and particulate resistivity aid with a cold side electrostatic precipitator (ESP).
1 . A process of enhancing fly ash collection comprising:
providing a flue gas that includes fly ash, which has a native fly ash resistivity, and combustion gases from a coal fired boiler;
adding into the flue gas a particulate resistivity aid that consists essentially of a particulate support carrying a resistivity agent;
reducing the native fly ash resistivity to an admixture resistivity; and then
collecting an admixture of the fly ash and particulate resistivity aid with a cold side electrostatic precipitator (ESP);
wherein a collected mass fraction of fly ash is increased without the addition of SO 3 .
2 . The process of claim 1 , wherein a first-field ESP, collected mass fraction is increased by at least 5%.
3 . The process of claim 1 , wherein fly ash emissions from the ESP are reduced by at least 10%.
4 . The process of claim 1 , wherein the particulate resistivity aid is injected into the flue gas between an air preheater and the ESP.
5 . The process of claim 1 , wherein the particulate resistivity aid is injected before an air preheater; and wherein the particulate resistivity aid flows through the air preheater before being collected by the ESP.
6 . The process of claim 1 , wherein injecting the particulate resistivity aid into the fly ash produces an admixture of the fly ash and particulate resistivity aid that includes about 0.1 wt. % to about 5 wt. % of the particulate resistivity aid.
7 . The process of claim 1 , wherein the particulate support does not reduce the native fly ash resistivity.
8 . The process of claim 1 , wherein the particulate support has a support resistivity that is greater than the native fly ash resistivity.
9 . The process of claim 1 , wherein the resistivity agent includes a water-soluble, alkali metal salt.
10 . The process of claim 9 , wherein the water-soluble, alkali metal salt is selected from a sodium salt, a potassium salt, and a mixture thereof.
11 . The process of claim 10 , wherein the water-soluble, alkali metal salt is a sodium salt.
12 . The process of claim 9 , wherein the resistivity agent further includes a transition metal.
13 . The process of claim 1 , wherein the particulate resistivity aid has a ratio of the particulate support to the resistivity agent in a range of about 1:1 (50 wt. %) to about 99:1 (1 wt %) by weight.
14 . The process of claim 13 , wherein the ratio of the particulate support to the resistivity agent in a range of about 4:1 (20 wt %) to about 19:1 (5 wt %) by weight.
15 . A process of enhancing fly ash collection comprising:
providing a flue gas that includes fly ash with a resistivity in a range of about 10 11 to about 10 14 ohm-cm at a temperature of about 150° C. to about 250° C. and combustion gases from a coal fired boiler;
injecting into the flue gas a particulate resistivity aid; and then
collecting the fly ash and particulate resistivity aid with a cold side electrostatic precipitator (ESP).
16 . The process of claim 15 , wherein injecting the particulate resistivity aid reduces the admixture resistivity to about 10 8 to about 2×10 11 ohm-cm.
17 . A process of enhancing fly ash collection comprising:
providing a flue gas that includes fly ash and combustion gases from a coal fired boiler that is burning Powder River Basin coal;
injecting into the flue gas a particulate resistivity aid thereby reducing a resistivity of the fly ash by at least about one order of magnitude (ohm-cm); and then
collecting the fly ash and particulate resistivity aid with a cold side electrostatic precipitator (ESP).
18 . A particulate resistivity aid comprising:
a particulate support selected from the group consisting of a silicate, an aluminate, a metal oxide, a polymeric support, and mixtures thereof; and
a resistivity agent carried by the particulate support.
19 . The particulate resistivity aid of claim 18 , wherein the resistivity agent includes a water-soluble, alkali metal salt.
20 . The particulate resistivity aid of claim 18 , wherein the particulate resistivity aid consists essentially of the particulate support and the resistivity agent,
wherein the resistivity agent includes a water-soluble, alkali metal salt.
21 . The particulate resistivity aid of claim 18 , wherein the particulate resistivity aid has a ratio of the particulate support to the resistivity agent in a range of about 1:1 to about 99:1 by weight.
22 . The particulate resistivity aid of claim 21 , wherein the ratio of the particulate support to the resistivity agent in a range of about 4:1 to about 19:1 by weight.