Based on health, emissions, and scientific data, the U.S. Environmental Protection Agency (EPA) and the Canadian Council of Ministers of the Environment (CCME) have determined that mercury emitted from utility power plants should be reduced. Plants burning lignite coal emit mercury in a form that is more difficult to control than the mercury emitted while firing other coals. In general, lignite coals contain comparable levels of mercury but lower levels of chlorine and higher concentrations of calcium. This combination causes much higher concentrations of elemental mercury emissions when burned. Although many lignite-fired power plants have some type of scrubber installed, these technologies are ineffective for removal of elemental mercury. Consequently, for utilities burning lignite, more innovative technologies and approaches are needed.

Developing Effective Mercury Control Options
The EERC is conducting a 3-year project to develop, test, and demonstrate cost-effective sorbent-based technologies that can be used to reduce mercury emissions from plants burning lignite coal.

Phase I: Bench- and Pilot-Scale Testing
The goal of Phase I is to generate data needed to select the most promising technology, which will be further tested and demonstrated under Phase II. Bench-scale activities include developing a better understanding of mercury interactions with lignite flue gas and testing a range of sorbent-based technologies such as sorbent injections targeted at oxidation and the removal of elemental mercury. Sorbent-based technology options that were tested at the pilot-scale include sorbent injection in combination with electrostatic precipitators (ESPs), ESPs followed by a baghouse, a baghouse only, and the EERC's Advanced Hybrid^TM filter technology. These technology options have all been tested at the EERC's pilot-scale combustion test facility, with encouraging results.

Phase II: Full-Scale Testing and Demonstration
Results and data generated under Phase I are being used to guide the selection, design, construction, and application of the most promising technology. Sorbent injection upstream of a pulse-jet-type baghouse is the mercury control technology that will be field-tested at the Poplar River Power Station, which is owned and operated by SaskPower. Activities planned for the field demonstration include:

• Field-testing the selected sorbent impacts and performance.
• Assessing technology impacts on unit operations.
• Assessing ash reuse and disposal impacts.
• Estimating cost to control mercury.

The results from the project should provide the lignite industry with a technology option that can be considered by other utilities as they develop their own mercury control strategies.

Sponsors

• SaskPower
• Environment Canada
• Luscar Ltd.
• Basin Electric Power Cooperative
• Minnkota Power Cooperative
• Otter Tail Power Company
• North Dakota Industrial Commission
• Minnesota Power, Xcel Energy, and Great River Energy through tailored collaboration with the Electric Power Research Institute
• U.S. Department of Energy through the EERC's Jointly Sponsored Research Program