Government/Private Coal Cleaning R&D Spawns New Technology Patents, Commercial Prospects

"Microcel" Technology Cleans Pollutants from Coal

Blacksburg, VA - An advanced U.S. coal cleaning technology first developed in a Federal laboratory has generated several new technology patents and expanded commercial prospects for the private industry developer.

Microcel, invented at Virginia Polytechnic Institute and State University (VPI), has been marketed worldwide for several years to remove ash, and some sulfur, from coal. The inventors of Microcel have now received a patent for a new technology that doubles the amount of sulfur removed when compared to traditional techniques currently used by industry.

Microcel is a novel froth flotation column cell for cleaning finely ground coal. It was first developed in the early 1980s by a VPI professor working as a summer intern at DOE's Pittsburgh Energy Technology Center (PETC). In the U.S., Microcel columns have been employed at commercial coal cleaning installations in Virginia, West Virginia, Ohio, and Kentucky, and for mineral processing installations in Arizona and Georgia.

In early 1995, DOE announced that the inventors had completed sales of 16 Microcel units to Australia and that negotiations were under way to sell six units to the China National Coal Development Corporation. The units have since been sold and installed in China.

In December 1995 the VPI developers patented a coal dewatering process that would further enhance the coal cleaning effectiveness of the Microcel units.

Now Gerald H. Luttrell, Associate Professor of Mining and Minerals Engineering, and Roe-Hoan Yoon, Director of the Center for Coal and Minerals Processing, located at VPI, have patented another coal cleaning process that improves sulfur removal when used in conjunction with Microcel.

In this newly patented process, a device generally referred to as an "enhanced gravity separator" -- which separates particles based on different densities -- is used with the Microcel unit, or any other flotation device. Coupling the flotation unit with a gravity separator creates a synergism that facilitates the more efficient removal of the sulfur-containing mineral, pyrite, from the coal.

When a coal is cleaned using a flotation device only, pyrite rejection is generally poor as the mineral acquires water-repelling properties and behaves similarly to coal -- both coal and pyrite will attach to air bubbles and float. Pyrite can be more readily separated from coal based on differences in density, particularly if coal is subjected to high gravitational forces.

This flotation/gravity separation process was successfully tested on a large scale at PETC in early 1995. The test results showed that the process can remove 85 to 95 percent of the pyrite from high-sulfur coals. An advantage of this process is that it works well without coal grinding, a step that is necessary to achieve such high levels of sulfur rejection when a coal is cleaned using a flotation device alone.

The technology developer also noted that the cost of implementing the new process is significantly lower than that for post-combustion scrubbers. Some of the low- to medium-sulfur coals can be cleaned by this process to less than the 1.2-pounds-of-SO2-per-million-Btu level mandated by the 1990 Clean Air Act Amendments and, hence, can be burned without using costly scrubbers.

"The price of coal is highly sensitive to sulfur, and coal companies can command higher prices for lower sulfur coals," says Yoon. "That's why western low-sulfur coals are displacing much of the eastern high-sulfur coals in the U.S."

"If we can remove the sulfur, we can increase the value of eastern U.S. coals," says Luttrell. Studies conducted at the Center for Coal and Minerals Processing showed that the patented technology can increase the retail value of coal by $2-3 per ton by virtue of the lower sulfur content in the product coal.

The new process is being marketed by Virginia Tech Intellectual Properties (VTIP), Inc.

-End of TechLine -

For more information contact:
Pat Leister, Pittsburgh Energy Technology Center, 412/892-6126, email: leister@petc.doe.gov

Hattie Wolfe, Fossil Energy Headquarters, 202/586-6503, email: hattie.wolfe@hq.doe.gov

At Virginia Tech: Dr. Yoon, 540-231-7056 or ryoon@vt.edu or Mike Martin, Virginia Tech Intellectual Properties, Inc., 540-231-8999 or martinmj@vt.edu