Plasma desulfurization

Since hydrogen sulfide was evolved in the electrical discharge, the dissociation of both the hydrocarbon phase and the sulfur compound must have occurred. The absence of H2S when pure thiophene was used is suggestive of the need for excess H atoms for effective plasma desulfurization. 

In view of the recent successful desulfurization of gasoline by metallic sodium216 at 500-600 K experiments using plasmas in mixtures of sodium vapor and sulfur compounds may demonstrate plasma chemistry that is useful for petroleum desulfurization. 

While desulfurization of petroleum fractions is a possibility more quantitative work is necessary before the plasma technique can be applied on industrial scale. 

There are few direct measurements of the sulfur removed from coals treated in plasmas. Zavitsanos and Bleiler305 reported that coal could be desulfurized without loss of heating value by exposing coal particles of 0.1—4 cm size in 1.5-2 cm layers to 2.45 GHz microwaves for 40 s in air at 1—5 torr pressure. The coal temperature did not exceed 420 K and the sulfur content was reduced from 4.11 to 1.91%. However, Scott et al.224 did not observe any significant change in S content (2%) of bituminous coals as a result of exposure to 60 Hz discharges in the annular space of a Siemens tube. 

U.S. EPA Office of Water Engineering and Analysis Division, Inductively Coupled Plasma/ Mass Spectrometry for Trace Element Analysis in Flue Gas Desulfurization Wastewater, 2009, http //water.epa.gov/scitech/wastetech/guide/steam-electric/upload/Steam-Electric FGD Draft-SOP 2011. pdf. 

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