High-Precision Trace Element and Organic Constituent Analysis of Oil Shale and Solvent-Refined Coal Materials

Abstract

The application of a number of sensitive and precise methods for the determination of trace elements, heavy element species and organic compounds in materials from an oil shale research retort process and from a solvent-refined coal pilot plant operation are discussed. The methods were chosen both for their sensitivity, and also for their relative freedom from interference effects. Coal liquids contain much higher concentrations of aromatic compounds, including polynuclear aromatic hydrocarbons (PNA's). A larger relative fraction of the pna's in shale oil are alkyl substituted. Coal liquids are also considerably higher in phenols (28 percent) than is shale oil (2 percent). N-heterocyclics are present in higher concentration (greater than 8 percent) in shale oil due to the high nitrogen content of the raw shale. Hydroaromatics are common in coal liquids but negligible in shale oil. Inorganic elements and speciation measurements indicate significant amounts of the toxic heavy elements Hg, As, Zn, and Se in effluent oil water and gas streams. In addition, the process water contains significant Co, Br, Sb, and U. Raw oil shale is highly enriched in Se, As and Sb and somewhat enriched in U, Pb, Cs, Hg and Zn. Solvent-refined coal liquids were found to bemore » relatively low in most trace elements. The majority of trace elements are concentrated by the process into the mineral residue. Only Br and Hg are not depleted in solvent-refined coal. Other trace elements still remaining in significant amounts are U, Ta, Cr, and Zn.« less