Under DOE-NETL Cooperative Agreement DE-FC26-03NT41724, EPRI, in collaboration with Frontier Geosciences and the University of North Dakota Energy and Environmental Research Center (EERC), will perform precise in-stack and in-plume sampling of mercury emitted from the stack of WE Energies' Pleasant Prairie coal-fired power plant near Kenosha, Wisconsin. The overall objective of the project is to clarify the role, rates and end result of chemical transformations that may occur to mercury that has been emitted from elevated stacks of coal-fired electric power plants. This information is critical in determining the role of coal-fired plants in mercury deposition and in developing cost-effective, environmentally sound policies and strategies for reducing the adverse environmental effects of mercury.

In this project, the concentration and speciation of mercury will be measured in the plume of a coal-fired power plant via near-real-time monitors mounted on an aircraft that will fly into the plume.  The in-plume data will be compared to similar measurements made within the power plant stack, and in two types of dilution sampling devices that attempt to simulate the mercury transformations occurring within the plume.  To accomplish the in-plume sampling, instruments will be carried through the plume by aircraft to at least two points downwind along the plume centerline, one close to the stack exit and the second some distance downwind.  The aircraft sampling approach will be to use valved inlets to the instruments, which will be triggered by fast-response sensors of plume-specific chemical constituents, such as nitrogen oxides. This will allow sampling of isolated plume material. Repeated passes through the plume under relatively steady wind conditions should allow time-of-flight equivalency for determining reaction rates for any redox reactions noted. Measurements of mercury speciation in the stack gases prior to emission  will be made simultaneously with the in-plume measurements, and results will be compared to determine the extent of mercury speciation changes.

To complement the in-stack and in-plume sampling, the diluted stack exhaust will be sampled via plume dilution chambers that are designed to simulate the mercury transformation processes that occur as the plume becomes diluted with ambient air. These results will then be compared to the full-scale measurements by aircraft to establish proof-of-method for the dilution chambers. If successful, these chambers can then be used at a greater number of power plants for inexpensive, rapid simulation of plume chemistry.

Data from all mercury measurements will be assembled, interpreted and integrated by EPRI into a comprehensive final report. A key product of the project will be the best-estimate rate of reduction or oxidation of mercury in the plume as measured during the experiments. This will be expressed as a lower bound value, depending on the distances and equivalent plume transit times sampled.

The project team comprises the following organizations:

• EPRI will be responsible for overall planning, coordination, implementation, and reporting of project activities and results.
• The University of North Dakota Energy and Environmental Research Center will be responsible for coal sampling, stack sampling and aircraft measurements of mercury.
• Frontier Geosciences will be responsible for the plume dilution sampling devices.
• WE Energies will serve as the host site for the field tests and will provide technical and logistical support.