The overall objective of this project is to assess the potential for significant mercury control, between 50 and 90% above baseline, by sorbent injection for the challenging technical process configuration at Public Service of New Hampshire Company Merrimack Station Unit No. 2. The primary emphasis of this project is to evaluate the performance of mercury sorbent injection, but the effect of co-benefits from SO₃ mitigation on mercury control will also be explored. Also in this program the performance capabilities of mercury measurement techniques in challenging flue-gas environment will be assessed and the impact of activated carbon injection on fly ash disposal options will be investigated.

Full-scale testing will be conducted on Unit 2 of the Merrimack Station. The unit is a cyclone-fired boiler with a rated capacity of 335 MW. The unit fires a blend of bituminous coals resulting in 1.0 - 1.3% sulfur. Coal chlorine content is on the order of 1000 µg/g. The particulate control equipment consists of two electrostatic precipitators (ESPs) in series. The first has a specific collection area (SCA) of 120 ft 2 /kacfm and the second ESP has an SCA of 230 ft 2 /kacfm. The unit is equipped with an SCR system utilizing anhydrous ammonia injection for NOx reduction, which is operated year-round and results in ozone season NOx emissions of 0.15 lb/MMBtu. Flue gas temperatures entering the first ESP are nominally 330 – 350^o F, depending on the load and the season.

Mercury control sorbent will be continuously injected into the flue gas over a period of six months. This shall be done in conjunction with any operating changes or SO₃ mitigating technologies that are developed in early tasks. This test period shall evaluate whether the mercury control scheme develops any long-term operational problems and whether mercury control is sustainable. Potential operational impacts that will be monitored include degradation of ESP performance, injection system performance, and contamination of fly ash. Long-term test measurements shall include a full suite of flue gas and solid sample measurements. These shall include at least three ESP inlet and outlet Ontario Hydro mercury measurements, as well as measurements for SO₃, particulate, halogens, and ammonia.

This project, if successful, will prove out new sorbents and co-control strategies that should surpass the performance of existing sorbents and lower the cost of mercury control for Eastern coals. The test results would be applicable to sites that burn medium- to high-sulfur coal, use SO₃ flue-gas conditioning, have small ESPs, operate at flue gas temperature greater than 350^o F, and have SCRs.