Sorbents for coal combustion
Sorbent compositions containing iodine are added to coal to mitigate the release of mercury and/or other harmful elements into the environment during combustion of coal containing natural levels of mercury.
1. A method for burning coal in a furnace to reduce emissions of mercury from a coal burning facility, the method comprising:
adding a mercury sorbent composition onto the coal upstream of the furnace, into the flue gases in a plant section of the facility downstream of the furnace, or in a combination of upstream and downstream additions;
adding a sulfur sorbent composition onto the coal upstream of the furnace, into the flue gases in a plant section of the facility downstream of the furnace, or in a combination of upstream and downstream additions;
combusting the coal in the furnace;
measuring the level of mercury present in the flue downstream from the addition of sorbent compositions; and
if the measured mercury level is above a target level, increasing a rate of addition of the mercury sorbent composition; or
if the measured mercury level is below a target level, decreasing a rate of addition of at least one of the components or leaving the rate of addition unchanged, wherein the mercury sorbent composition comprises a halogen compound and the sulfur sorbent composition comprises silica and alumina.
2. The method of claim 1 , wherein the sulfur sorbent composition comprises more than 2% by weight silica and greater than 2% by weight alumina.
3. The method of claim 1 , wherein the sulfur sorbent composition comprises an aluminosilicate clay.
4. The method of claim 3 , wherein the aluminosilicate clay is montmorillonite or kaolin.
5. The method of claim 1 comprising adding the sulfur sorbent downstream of the furnace in a region having a temperature of 1500-2700° F.
6. The method of claim 1 comprising adding the mercury sorbent downstream of the furnace in a region having a temperature of 1500-2700° F.
7. The method of claim 1 wherein the mercury sorbent composition comprises an iodine compound.
8. The method of claim 6 wherein the mercury sorbent composition comprises an iodine compound.
9. The method of claim 1 , wherein emissions of mercury are reduced by at least 70%, compared to burning the coal without applied sorbent compositions.
10. The method of claim 1 , wherein both the mercury sorbent composition and the sulfur sorbent composition are added upstream of the furnace.
11. The method of claim 1 , wherein both the mercury sorbent composition and the sulfur sorbent composition are added downstream of the furnace where the temperature is 1500-2700° F.