First full-scale demonstration of mercury control in Alberta

Alberta electricity companies, TransAlta, ATCO, and EPCOR, teamed with GE Energy to conduct full-scale evaluation of sorbent injection in Sundance Unit 5 operated by TransAlta. Sundance Unit 5 fires a Western Canadian sub-bituminous coal and is equipped with cold-side ESP for PM control. Goals of the program were to evaluate: (1) the ability of achieving 70% or greater mercury reduction using activated carbon injection in long-term tests (30 days), (2) the effect of sorbent injection on ESP performance and opacity in long-term testing, and (3) the effects of combustion conditions on “natural” mercury removal in fly ash.DARCO Hg-LH was injected upstream of ESP at average injection rate of 2.1 lb/MMacf and achieved an average mercury removal of 80%. During the test, the sorbent injection rate was varied from 0.55 lb/MMacf to 8 lb/MMacf with mercury removals from 65% to > 95%. The continuous 30-day DARCO Hg-LH injection testing demonstrated that 70% mercury removal could be achieved at DARCO Hg-LH injection rate of 1.2 lb/MMacf.Tests were conducted to optimize combustion conditions to improve “native” mercury capture in the fly ash. Testing demonstrated that combustion conditions that resulted in reduction of NOx emissions also corresponded to reduced mercury emission. Mercury emissions were reduced by up to 50% and NOx emissions by up to 35% from baseline levels as a result of changes in the way Unit 5 operated. Integration of sorbent injection with combustion conditions reduced requirements for sorbent injection by 20–30%.Testing has demonstrated that sorbent injection did not have an effect on opacity and ESP performance.