Characterization of mercury, arsenic, and selenium in the product streams of the Pacific Northwest Laboratory 6-kg retort

Abstract

The objective of this program is to determine how retorting process parameters affect the partitioning of Hg, As, Se, and Cd from raw o11 shale to spent shale, shale oil, retort water, and offgas. For each of the elements, the objective of this study is to 1) determine the distribution coefficients for each product stream; 2) identify the chemical forms in water, gas, and oil streams, with particular emphasis on inorganic or organometallic species known to be or suspected of being carcinogenic, toxic, or otherwise harmful; 3) investigate the mechanism(s) responsible for mobilization into each product stream for toxic or labile chemical forms identified in item 2 are mobilized into each product stream; and 4) the effect of retorting rate, maximum retorting temperature, and retorting atmosphere on items 1 and 3. A Green River shale from Colorado and a New Albany shale from Kentucky were heated at 1 to 2°C/min and at l0°C/min to maximum temperatures of 500 and 750°C under a nitrogen sweep gas. The product streams were analyzed using a variety of methods including Zeeman atomic absorption spectroscopy, microwaveinduced helium plasma spectroscopy, x-ray fluorescence, instrumental neutron activation analysis, high-pressure liquid and silica gel column chromatography, and mercury cold vapor atomic absorption. The results obtained using these analytical methods indicate that the distribution of mercury, arsenic, and selenium in the product stream is a function of oil shale type, heating rates, and maximum retorting temperatures.

Characterization of mercury, arsenic, and selenium in the product streams of a bench-scale, inert-gas, oil shale retort

“…Comparing these results to those observed during the retorting of the three aforementioned Australian shales revealed some differences and some similarities. The selenium in Julia Creek (10) (19) had a tendency to distribute almost equally into the shale oil and the retort water in a manner similar to the behavior in this study's eastern shale; however, contrary to the Australian study findings (10,19) that selenium was progressively mobile as temperatures increased in the Julia Creek, Condor, and Rundle oil shales, this study found little dependency on heating rates or maximum temperatures.…”

“…Selected samples of raw shale, spent shale, shale oil, and retort water were analyzed for total arsenic and selenium (19); the shale oil and retort water samples were also analyzed for mercury by INAA. In addition, a neutron multiplier system was used on selected shale oil samples specifically for selenium analysis.…”

“…Oil shale, spent shale, and shale oil were analyzed for mercury by cold vapor atomic absorption spectroscopy (19).…”