First full-scale demonstration of mercury control in Alberta

Abstract

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 NO x emissions also corresponded to reduced mercury emission. Mercury emissions were reduced by up to 50% and NO x 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.