REDUCING MERCURY IN STACK EMISSIONS
The testing program evaluated the technical feasibility of utilizing a post-combustion injection system for reducing mercury in stack emissions at a power station in Maryland. In addition to the technology demonstration, BioLargo Engineering also evaluated the technical effectiveness of using a calcium bromide (CaBr2) oxidation solution as applied to the coal feed into the boiler. The CaBr2injection system and materials were supplied by an independent third party vendor.
Field Trial Process
Flue gas samples were collected at the Unit 2 economizer outlet (ECON Out), the electrostatic precipitator (ESP) outlet, and the stack common to both Units 1 and 2. Emissions data acquired at the stack were used primarily to evaluate the site’s Hg CEMS. In conjunction with emissions of Hg, other stack gas parameters and selected pollutants were measured to determine the gas stream concentrations and/or mass emission rates.
For this testing and evaluation project, the multiple injection scenarios created a diverse data set. Each oxidizing material, in conjunction with multiple injection rates and locations, can affect the performance of the boiler or APC devices. A comparison of every potential scenario would have resulted in dozens of possible operating conditions. Therefore, the testing program limited the number of testing runs for each single (or combination) injection material and also restricted the locations of injections. This limited number of data points restricted statistical comparisons for evaluation of performance but did present a reasonable data set for qualitative analyses. Details of these conditions are presented by comparison in the report data summary tables. Given the volume of data, we have presented only summaries of the testing data in the report sections, with the complete backup of testing data provided in the appendices.
Specific tasks that were performed by BioiLargo’s Engineering team included:
- Successfully demonstrated to be a viable and effective method to oxidize elemental mercury to a soluble mercury salt that can then be targeted for removal from the gas stream by downstream air pollution control equipment.
- A total oxidized Hg fraction of greater than 90%.
- Successfully demonstrated that elemental mercury mass rates can be reduced to below the current emission limits.