WASHINGTON, DC - Close on the heels of the U.S. Environmental Protection Agency’s March 15 release of its Clean Air Mercury Rule, the U.S. Department of Energy has issued a license to private industry to commercially develop a promising low-cost, DOE-patented mercury control technology.
DOE’s National Energy Technology Laboratory issued the license on a technology called the Thief Process to Mobotec USA, Inc., of Walnut Creek, Calif. Mobotec, a leader in developing cost-effective combustion improvement and multi-pollutant reduction technologies for industrial and utility boilers, plans to create prototype systems and conduct full-scale tests of the process. As the exclusive licensee of the Thief patent, Mobotec will ultimately market and sell the technology.
“This licensing demonstrates the longstanding, successful relationship between DOE and its industry partners to move promising technologies from the government to the private sector,” said Principal Deputy Assistant Secretary for Fossil Energy Mark Maddox. “The DOE-patented Thief Process serves as yet another step forward in the Department’s mercury control technology program to make the nation’s air as clean as possible.”
The licensing agreement between NETL and Mobotec is timely in addressing EPA’s new mercury rule, the first-ever federal rule to permanently cap and reduce mercury emissions from coal-fired power plants. The mercury rule limits mercury emissions from new and existing coal-fired power plants and further establishes a market-based cap-and-trade program to reduce utility emissions. When fully implemented in 2018, the EPA rule will slash mercury emissions from power plants from the current 48 tons a year to 15 tons — a 70 percent reduction.
DOE has worked hand-in-hand with the EPA since 1990 to progressively understand mercury emissions and develop technologies to address those emissions and their inherent effects on health. NETL, which manages the Department’s mercury control technology program, has awarded a number of contracts to private industry to improve performance of technologies such as scrubbers, fabric filters, and electrostatic precipitators.
However, few technologies currently exist to consistently and cost-effectively remove mercury from power plant flue gas. Most of the technologies today use activated carbon in their processes, but the costs for its use are very high, ranging from $500 to $3,000 per ton.
NETL researchers developed and patented the Thief Process as a cost-effective alternative to the use of activated carbon. In the Thief Process, partially combusted coal is extracted from the boiler of a pulverized coal power plant and re-injected into the ductwork downstream of the air preheater. By extracting the partially combusted coal, thermally activated sorbent is produced. Once it is introduced into the flue gas, the sorbent reacts with mercury and removes it from the flue gas stream. Since the cost of coal is relatively inexpensive, around $30 per ton, the resultant cost for the Thief sorbents is estimated to be between $90 and $250 per ton.
During earlier tests burning low-chlorine subbituminous coal, the Thief Process achieved mercury removal rates as high as 93 percent. Researchers were able to verify those results by applying the Thief Process at a working pilot plant. The Thief Process could be applicable to many power and industrial plants burning a range of coals and having various configurations of air control devices.
Although mercury naturally occurs throughout the environment, it primarily remains “locked up” in ores, though it can be released through human activities such as power plant combustion, municipal waste combustion, and medical waste incineration. Of these human activities, coal-fired plants annually emit about 48 tons of mercury, which is approximately 40 percent of total U.S. mercury emissions and one percent of mercury emissions from all sources worldwide.
With continued successes in technologies such as the Thief Process, the DOE mercury control technology program will continue to meet the nation’s environmental goals.