The influence of carbon particle type in fly ashes on mercury adsorption

Abstract

Recent research has shown that certain fly ash materials produced in coal combustion for power generation have an affinity for the mercury compounds present in flue gases. However, the exact nature of Hg-fly ash interactions is still unknown and the different variables that influence mercury adsorption need to be identified. In this work the microscopic components of fly ashes derived from the combustion of different types of feed blends of different coal rank and mercury adsorption were investigated. The aim of this research was to establish relationships between Hg retention and the type of unburned carbons present in various fly ashes. The fly ashes and fly ash fractions studied were used as sorbent beds for high mercury concentrations, conditions in which mercury retention is highly favored. From the results obtained it was confirmed that the role of the unburned carbon components in mercury capture may depend, among other factors, on the type of unburned carbon. Fly ashes capture different species of mercury depending on their nature and the type of anisotropic particles.

The role of unburned carbon concentrates from fly ashes in the oxidation and retention of mercury

“…A number of investigations have attempted to correlate Hg retention and oxidation with the content and characteristics of unburned carbon in raw fly ashes [15][16][17] and have found that, in general, Hg capture increases in fly ashes with a high carbon content [18]. However, the precise mechanisms by which the unburned carbon present in fly ash interacts with Hg species in gas phase are not yet well understood.…”

Experimental study on fly ash capture mercury in flue gas

“…Comparing to anisotropic carbon particles, the relation between isotropic carbon particles and mercury capture capacity is not so clear (Figure 8), even in high mercury concentration [17]. There is no obvious relationship between other petrology components (including other organic, glass, spinels, etc.)…”

“…The porous carbon particle has a great specific surface area, so it can adsorb more mercury. Antonia et al investigated mercury adsorption performance of fly ash in high mercury concentration (about mg/m 3 ), and they also suggested that the relation between anisotropic carbon and mercury capture capacity is very clear [17].…”

“…The content of inorganic components is inversely proportional to mercury capture capacity of fly ash ( Figure 9). While, the influence of inorganic components on mercury adsorption is complex, especially for the glass phases, the mercury capture capacity increased sharply in high mercury concentration [17]. Galbreath et al [18] found that the mercury removal capacity of iron oxides with different speciation varied, which also indicated the complexity of mercury adsorption mechanism by inorganic components in fly ash.…”

Evaluation of elemental mercury adsorption by fly ash modified with ammonium bromide

“…The major factors affecting mercury removal efficiency are composition of the fly ash, unburned carbon content, reactivity, and surface area [20,21]. For this study, the fly ash sample was collected at the outlet of the ESP from a Chinese pulverized coal boiler utilizing bituminous coal.…”