The sulfur problem where separations can help

Our principal sources of energy - fossil fuels - are all contaminated to some extent with sulfur compounds. When these fuels are burned, the sulfur compounds are burned to sulfur oxides, which are emitted to the atmosphere in the flue gas. In the atmosphere, these oxides are converted into the sulfur acids that are a principal cause of acid rain. 

Natural Gas. The principal sulfur contaminant of natural gas is another gas -hydrogen sulfide. Because it is extremely toxic, civil authorities have long forbidden significant levels of this compound in natural-gas pipelines. Hydrogen sulfide is removed from natural gas by a variety of commercial processes including reaction with aqueous solutions of oxidants, absorption into aqueous solutions of bases, distillation, and selective permeation through membranes. The end product of these processes is elemental sulfur, which can be sold and, in some cases, is worth more than the co-produced natural gas. In 1984, about 24,000 tons (24 million kilograms) of sulfur was produced from natural-gas wells in the United States. 

Petroleum. Sulfur can also be recovered from crude oil with technoiogy that relies on the reaction of hydrogen with sulfur-containing compounds in crude oii (hydrodesulfurization) and permits modern refiners to turn 3 percent sulfur crudes into liquid product with no more than 0.5 percent sulfur. About 26,000 tons of saleable by-product sulfur was produced from crude oil in 1983. 

Coal can be partially desulfurized before combustion. Washing and magnetic 

Separations technoiogy has made a substantiai contribution to reducing the sulfur-pollution problem associated with the burning of fossil fuels. The principal barrier to further alleviation of this problem is economic and will respond to improved technology gained through further research and development [1]. 

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