URS Group, Inc., in collaboration with EPRI, Apogee Scientific, AEP, Texas Genco, and TXU Power, ADA-ES, will evaluate sorbent injection for mercury control in an 85/15 blend Texas lignite/PRB derived flue gas, upstream of a cold-side ESP – wet FGD combination.

Full-scale sorbent injection tests conducted with various sorbents and combinations of fuel and plant air pollution control devices (APCD) have provided a good understanding of variables that affect sorbent performance. However, many uncertainties exist regarding long-term performance and data gaps remain for specific plant configurations. For example, sorbent injection has not been demonstrated at full-scale for plants firing Texas lignite, which represent approximately 10% of the annual U.S. power plant mercury emissions. The low and variable chloride content of Texas lignite may pose a challenge to achieving high levels of mercury removal with sorbent injection. Furthermore, activated carbon injection may render the fly ash unsuitable for sale, posing an economic liability to Texas lignite utilities. Alternatives to standard activated carbon, such as non-carbon sorbents and alternate injection locations (Toxecon II), have not been fully explored. Toxecon II involves sorbent injection in the middle field(s) of an ESP, thus preserving the integrity of the fly ash in the first fields.

URS Group and its team are proposing this program to evaluate sorbent injection in flue gas derived from Texas lignite. Tests will be conducted at Texas Genco's Limestone Steam Generating Station to evaluate sorbent injection across a cold-side ESP and wet scrubber combination. Parametric tests will be performed with three sorbent materials to determine how addition rate upstream of the ESP impacts mercury removal and supplemental removal across the wet scrubber. Sorbents will include a standard activated carbon, a brominated carbon, and a low-ash impact carbon. Results of initial parametric tests will be used to select two sorbents for additional parametric tests in which injection will occur at three different locations in the ESP: (1) upstream of the ESP, (2) in the middle of the ESP (Toxecon II), and (3) staged injection in which sorbent is injected both upstream of the ESP and in the middle of the ESP. A two month continuous injection test will then be performed with one selected sorbent and injection configuration to evaluate long-term performance and possible effects on ESP or wet FGD scrubber operation or byproduct quality.