LBL Research Review August 1994

STEPPING UP THE ATTACK AGAINST acid rain and smog, LBL researchers have developed a new technology to help eliminate sulfur dioxide air pollution from power plants, incinerators, chemical plants, and smelters.

Part of a multi-stage treatment system, the LBL process treats concentrated sulfur dioxide, converting more than 95 percent of it to a valuable commodity: elemental sulfur, a chemical feedstock that can be sold.

Cost is the overriding factor affecting the success of emissions treatment technology. A number of effective technologies have been developed to treat fossil fuel emissions prior to venting them into the atmosphere. However, due to the cost, most of the world's power plants do not significantly treat exhaust gases. Likewise, utilities often elect not to burn abundant fuels such as coal, which have a relatively high sulfur content, because of the expense of removing sulfur dioxide.

The LBL team, which includes Shih-Ger Chang of LBL's Energy and Environment Division and visiting professors Yun Jin and Qiquan Yu from Beijing University, says the primary advantages of their new technology are its affordability and simplicity.

The process relies on the team's invention, a new catalyst for which a patent is pending.

The catalyst consists of an inexpensive mixture of iron-based metal oxides supported on alumina. It was tested in the laboratory over a lifetime of 1080 hours, and the catalytic activity proved very stable.

Dealing with sulfur has frustrated the emergence of one promising clean-coal technology, the Integrated Gasification Combined-Cycle (IGCC) method. The method can convert 42 percent of the energy potential in coal into electricity, a seven percent improvement over the technologies now in common use.

IGCC combines coal, water, and heat to produce a synthetic gas that consists of carbon monoxide, hydrogen, and hydrogen sulfide. However, before this hot gas can be burned to produce electricity, the hydrogen sulfide must be treated.

Researchers have been looking for a way to remove the hydrogen sulfide from the initial synthetic hot gas mix. One technique under development sprays the hot gas with metal salts, and ultimately results in the production of reusable metal salts and concentrated sulfur dioxide.

The new LBL process deals with this concentrated sulfur dioxide by feeding a mixture of synthesis gas and sulfur dioxide into a catalytic chamber, which in a single step, reduces more than 95 percent of the sulfur dioxide to elemental sulfur. This makes the IGCC method more efficient and thus more affordable.

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