Characterization of Carbon Concentrates from Coal-Combustion Fly Ash

Abstract

A study of carbon concentrates separated by a number of different commercial and laboratory methods from various coal-combustion fly ashes was undertaken to determine what common and unique chemical and physical properties can be expected in such concentrates. The properties were determined using a variety of physical and spectroscopic characterization methods and then were compared among the carbon concentrates and in two cases with the properties of the unprocessed fly ashes. The class F fly ashes originated from a total of seven different utilities burning bituminous coals and underwent one of six different processing methods to produce the carbon concentrates, which contained from 24% to 76% carbon. Three different configurations of triboelectrostatic separators were used to produce the carbon concentrates in addition to two different flotation methods plus a proprietary carbon recovery process. The results showed that unburned carbon concentrates from fly ash have properties similar to most carbon blacks and would be poor replacements for activated carbon in adsorption processes unless they are activated in a separate step. The untreated carbon may have applications as a substitute for carbon black provided it could be obtained in sufficient purity. The results have implications for those who wish to use carbon concentrates from coal-combustion fly ashes in secondary markets, especially as sorbents and fillers.

Impact of Fly Ash Composition on Mercury Speciation in Simulated Flue Gas

“…Carbon black was used in this study to represent UBC in the samples because of the similarities between UBC in fly ash and carbon black. 22 …”

“…2,13,[17][18][19][20] The capacity of fly ash for HgCl 2 and Hg°are similar, 9 but the adsorption rate is higher for HgCl 2 . 21 Results from Baltrus et al 22 showed that UBC concentrates from different fly ash samples have properties similar to most carbon blacks. In general, Hg°reten-tion increases with the surface area of the carbon in the ash in a linear relation.…”

Seasonal dynamics of atmospheric and river inputs of black carbon, and impacts on biogeochemical cycles in Halong Bay, Vietnam

“…For example, coal fly ash, which contains from 20 to 60% BC (Külaots et al, 2003(Külaots et al, , 2004Styszko-Grochowiak et al, 2004), is very efficient at adsorbing molecules from aqueous solutions and flue gas (Baltrus et al, 2001;Külaots et al, 2004;Styszko-Grochowiak et al, 2004;Wang and Wu, 2006;Ahmaruzzaman, 2010), with adsorbing capacity largely linked to its carbon (BC) content (Hassett and Eylands, 1999;Hower et al, 2000Hower et al, , 2010Külaots et al, 2003Külaots et al, , 2004. This byproduct of coal combustion is used as a low-cost adsorbent for cleaning flue gas from SOx, NOx, mercury and organics (Bossan et al, 1995;Seigneur et al, 1998), but also for cleaning wastewater from dissolved organic matter, heavy metals, pesticides and nutrients (Gupta et al, 2002).…”

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

“…In view of the significant variations in the properties of fly ashes obtained from different coals [15,[18][19] and to obtain a better understanding of the properties of the materials that influence the capture of Hg, we have tried to establish a relationship between Hg 0 and HgCl 2 retention and the characteristics of fly ash samples taken from the combustion of feed coal blends of different characteristics. This study is part of a broader work carried out in a laboratory scale reactor that aims to clarify the influence of several variables on mercury capture in fly ashes [11,20].Data on the proportions of different types of carbon particles present in fly ashes were studied together with the ability of these materials to retain high concentrations of mercury in a laboratory scale reactor in which the ashes were used as fixed beds.…”