The intent of DOE's Phase I and II field tests was to work with industry to evaluate the most promising mercury control technologies at full-scale in a variety of configurations. Although longer-term tests were conducted, the test period was not sufficient to answer many fundamental questions about long-term consistency of mercury removal and reliability of the system when integrated with plant processes. As the technologies move towards commercial implementation, it is critical to accurately define the mercury removal performance and costs so that power companies and policy makers can make informed decisions. Therefore, the overall objective of this Phase III project is to determine the mercury removal performance, long-term emissions variability, and associated O&M costs of activated carbon injection for >90% mercury control over a 10 to 12 month period on a unit that represents the combination of coal and emission control equipment that will be used for many new and existing power plants.

Full-scale testing with commercial-grade equipment will be conducted on the boiler at the Hardin Generating Station. The unit is a PC boiler with a rated capacity of 116 MW. The unit will fire PRB subbituminous coal with approximately 0.65% sulfur. Coal chlorine content is typically <30 ppm. A spray dryer absorber is employed for SO₂ control and particulate control equipment consists of a fabric filter. The unit is equipped with low-NOx burners and an SCR system for NOx reduction. Flue gas temperature at the injection location is nominally 260 to 320^o F, depending on the load and the season.

The primary project objective will be achieved by installing an activated carbon injection system integrated with new-generation mercury CEMs and plant operations for feedback control to optimize sorbent costs. Activated carbon injection will be tested along with a co-benefit analysis of the SCR, SDA, and FF system, with and without additives to enhance the mercury oxidation performance of the SCR. The effectiveness of coal blending will also be tested. Field-testing shall cover a period of 20 months, and shall include baseline measurements, co-benefits analysis, parametric tests, and long-term tests. Baseline and long-term test measurements shall include a full suite of flue gas and solid sample measurements. These shall include spray dryer inlet and fabric filter outlet mercury measurements, particulate, halogens, and ammonia measurements.

This project, if successful, will verify that >90% mercury control can be achieved with sorbents at costs < $10,000/pound of mercury removed. It will also identify mercury removal and long-term emission variability for a configuration being considered for many new plants. Additionally, data on long-term operability, maintainability, and reliability of mercury control systems and compliance mercury CEMs will be obtained. A successful project will show that the injection equipment and mercury CEMs have matured from the research stage to a point that the operation is simpler and can be turned over to plant personnel.