Mercury Capture from Flue Gas Using Palladium Nanoparticle-Decorated Substrates as Injected Sorbent

Abstract

Although the Clean Air Mercury Rule (CAMR) was recently vacated by the District of Columbia Court of Appeals, efficient mercury (Hg) capture is still an important topic for the coal-fired power plant industry. Several states have Hg emission regulations that are even more stringent than CAMR guidelines. All coals contain Hg, which is released during combustion. Significant research efforts have been made to capture this toxic element before it is released to the atmosphere where it can stay suspended and travel for great distances. A variety of approaches have been examined, among which the injection of sorbent materials such as powdered activated carbon (PAC) is the current method of choice. The work presented here examined the mercury capture capability of various carbon substrates decorated with metal nanoparticles when injected as sorbents. Sorbent injections were carried out in a Hg in air mixture for laboratory-scale screening and in a real flue gas at a coal-fired power plant. It was found that palladium-decorated carbon substrates showed excellent mercury capture capabilities, with total efficiencies greater than 90% in laboratory-scale tests. In the real flue gas, the total efficiency was on the order of ∼60%, comparable to the benchmark commercial sorbent Darco Hg-LH, a brominated PAC, although the tested adsorbents had much lower surface areas. The results of this study are presented herein. Novel mercury capture from a coal-fired flue gas was achieved using carbon substrates decorated with palladium nanoparticles.

First principle study of the interaction of elemental Hg with small neutral, anionic and cationic Pd n (n = 1‒6) clusters

“…[5][6][7][8][9] Nevertheless, in the case of coal gasification for power generation, Hg removal at high temperatures may lead to improvement in the thermal efficiency of IGCC system. Many researchers deeply investigated the possibility of using noble metals such as gold (Au), 10,11 silver (Ag), [12][13][14] palladium (Pd) 15,16 and platinum (Pt) 15 as efficient Hg removal sorbents. 17 These Hg removal sorbents, which show excellent performance for removal of Hg, are regenerable and are also stable for longtime operation.…”

Coal Fired Flue Gas Mercury Emission Controls

“…It has been widely accepted that the minor constituents (SOx, NOx, O 2 , and H 2 O) and fly ash play an important role in mercury reactions in flue gases from coal combustion in air [26][27][28][29]. The influence of these species on mercury oxidation was demonstrated when they were tested individually and also when they were blended in different gas compositions, although the effect was different to the sum of their individual effects.…”

“…It was found that palladium-decorated carbon substrates showed excellent mercury capture capabilities, with total efficiencies greater than 90 % in laboratory-scale tests [29]. Significant research efforts have been made to capture this toxic element before it is released to the atmosphere where it can stay suspended and travel for great distances.…”

“…Previous studies evaluated the effects of various catalytic materials on mercury speciation and found that CuO nanoparticles were most effective for mercury oxidation under low HCl concentrations [29].…”

“…29 The mercury removal efficiencies at different injection rates (pilot scale) (Reprinted from Ref [41],. Copyright 2008, with permission from Elsevier)…”