Complexation and removal of heavy metals from flue gas desulfurization systems
View Patent ↗A method for the reduction of the emission of mercury into the environment from the burning of fossil fuels with the use of polydithiocarbamic compounds. The polydithiocarbamic compounds are used for the capture of mercury from the resulting flue gases using a flue gas desulfrization systems or scrubbers. The method uses polydithiocarbamic compounds in conjunction with a scrubber to capture mercury and reduce its emission and/or re-emission with stack gases. The method is a unique process of reducing the toxic levels of mercury, which allows for the use of coal as a clean and environmentally friendlier fuel source.
1. A method for preventing the re-emission of mercury in a flue gas wet scrubber process, the method comprising:
burning coal, thereby producing a flue gas; and
passing the flue gas into the flue gas wet scrubber process comprising a scrubber liquor and a polydithiocarbamic compound of one or more polythiocarbamic materials.
2. The method of claim 1 wherein the polydithiocarbamic compound is water soluble.
3. The method of claim 1 wherein the polydithiocarbamic compound contains 5 to 50 mole percent of diothiocarbamate salt groups.
4. The method of claim 1 wherein the polydithiocarbamic compound contains 15 to 50 mole percent of dithiocarbamate salt groups.
5. The method of claim 1 wherein the polydiothiocarbamic compound contains 25 to 40 mole percent of dithiocarbamate salt groups.
6. The method of claim 1 wherein the polydithiocarbamic compound has a molecular weight of 500 to 100,000.
7. The method of claim 1 wherein the polydithiocarbamic compound has a molecular weight of 1,500 to 10,000.
8. The method of claim 1 wherein the polydithiocarbamic compound has a molecular weight of 1,500 to 5,000.
9. The method of claim 2 wherein the slurry is water-based.
10. The method of claim 1 wherein the scrubber is a spray tower system.
11. The method of claim 1 wherein the scrubber is a jet bubblers system.
12. The method of claim 1 wherein the scrubber is a co-current packed tower system.
13. The method of claim 1 wherein the polydithiocarbamic compound is added to the system in a weight ratio of 1:1 to 2000:1 in relation to the mercury content.
14. The method of claim 1 wherein the polydithiocarbamic compound is added to the system in a weight ratio of 5:1 to 500:1 in relation to the mercury content.
15. The method of claim 1 wherein the polydithiocarbamic compound is added to the slurry and then added to the scrubber.
16. The method of claim 1 wherein the polydithiocarbamic compound is added to the scrubber containing the slurry.
17. The method of claim 1 wherein the polydithiocarbamic compound is added to the virgin liquor then added to the scrubber.
18. The method of claim 1 wherein the polydithiocarbamic compound is added to a make-up liquor then added to the scrubber.
19. The method of claim 1 wherein the polydithiocarbamic compound is added to a return liquor then added to the scrubber.
20. The method of claim 1 wherein the polydithiocarbamic compound is added to a reclaimed liquor then added to the scrubber.
21. The method of claim 1 wherein the polydithiocarbamic compound is added to a liquor injected directed into flue gases then added to the scrubber.
22. The method of claim 1 wherein the polydithiocarbamic compound is added to a lime slurry then added to the scrubber.
23. The method of claim 1 wherein the polydithiocarbamic compound with dithiocarbamate salt groups is added to a recirculation loop of the scrubber liquor.
24. The method of claim 1 wherein the polydithiocarbamic compound with dithiocarbamate salt groups is added to a low solids return to the scrubber from the scrubber purge stream.
25. The method of claim 1 , wherein the flue gas wet scrubber process comprises a wet flue gas desulfurizer process.