A New Approach for Retaining Mercury in Energy Generation Processes: Regenerable Carbonaceous Sorbents

Abstract

Abstract:The energy production processes from fossil fuels represent the first anthropogenic source of mercury emissions in Europe and the second in the world. Among the different possibilities that can be posed to reduce these emissions, this work focuses on the use of regenerable sorbents based on gold nanoparticles dispersed on activated carbon foam. The use of regenerable sorbents would not only allow the objective of reducing mercury emissions, but also avoiding the generation of new toxic wastes. The results showed a retention efficiency of 100% and a retention capacity close to 600 µg·g −1 over several cycles of regeneration. Moreover, acid gases did not poison the support. It was observed that mercury capture in this simulated oxy-combustion atmosphere was a consequence of two mechanisms: (1) the amalgamation of elemental mercury and elemental gold and (2) the oxidation of elemental mercury in the presence of HCl, with the subsequent retention of the oxidized mercury on the surface of the activated carbon foam. The nanodispersion of gold on such supports involves a high initial investment. However, this would be counterbalanced by the remarkable regeneration capacity of the sorbent and the possibility of recovering all the materials used.

In Situ Decoration of Selenide on Copper Foam for the Efficient Immobilization of Gaseous Elemental Mercury

“…A high pressure drop and low surface-to-volume ratio are inevitable for a powder fixed-bed. The application of monolith adsorption materials could significantly overcome these disadvantages. − For decades, a ceramic honeycomb was a typical commercial monolith support, but it still suffered from the drawbacks of poor mass transfer ability and low mechanical strength . Metal foams, with strong mechanical stability, plasticity, high porosity, and superior mass transfer ability, have attracted great attention. , Generally, the active component is immobilized on the support by impregnation, wash-coating, or dip-coating. , However, the aggregation of particles causes the inhomogeneous distribution of active components and the blockage of channels.…”

Carbon materials loaded with maghemite as regenerable sorbents for gaseous Hg0 removal

“…The AC support was the commercial activated carbon Norit RB3 (Cabot Norit Nederland B.V.), whereas the carbon foam (CF) was synthesized from a bituminous coal specifically for this work, according to a procedure described elsewhere [17,26]. Previously, similar carbon foams have been employed as a support for Au and have shown great potential as regenerable sorbents for mercury capture [10,17]. However, in such cases the bituminous coal used as foam precursor was demineralized, whereas in this work raw coal was used without any previous treatment.…”

“…The gases emitted by some industrial activities, and in particular those from coal combustion, may contain different species of mercury, such us elemental mercury (Hg 0 ), oxidized mercury (Hg 2+ ) and particulate-bound mercury (Hgp). Of these species, Hg 0 is the most difficult to capture as it is highly volatile, difficult to dissolve in water and chemically inert [10] In contrast, Hg 2+ and Hgp can be efficiently captured by gas cleaning systems already installed for other pollutants, such as wet flue gas desulfurization scrubbers (WFGD) and electrostatic precipitators (ESP) installed in coal power plants for SO2 and particle control respectively [1,11] Mercury speciation and the concentrations of these Hg species depend on the type of fuel used and on the operational conditions of the boiler. For example, higher concentrations Hg 0 are emitted from coal gasification or pyrolysis than from coal combustion [12].…”

A Molten-Salt Pyrolysis Synthesis Strategy toward Sulfur-Functionalized Carbon for Elemental Mercury Removal from Coal-Combustion Flue Gas

“…Coal combustion is one of the largest industrial sources of mercury emission. The mercury emitted from typical coal-combustion flue gas generally existed in three forms, i.e., elemental mercury (Hg 0 ), oxidized mercury (Hg 2+ ), and particulate bound mercury (Hg p ) [4][5][6][7][8]. The Hg p can be captured by using particulate matter control devices, while the Hg 2+ can be removed by using wet flue-gas scrubbers due to Hg 2+ 's water solubility [9][10][11][12].…”