The Mercury & Air Toxics Standards (MATS) rule requires coal-fired generating units to comply with emissions limits on filterable particulate matter (PM), acid gases (HCl), and mercury (Hg). The burning of low sulfur fuels, addition of lime-based sorbents for HCl control, and the reduction in SO3 for Hg control, can all tax the performance of the aging fleet of electrostatic precipitators (ESP).
This paper discusses three projects in which low ripple three-phase power supplies (TPPS) were used as part of the solution in reducing the ESP PM emissions. TPPS have been used on coal- fired boiler ESPs in Europe for many years, and in the past three years, Babcock & Wilcox (B&W) has more than 800 installations in China on cement kiln ESPs. Previous to this writing, there had been no installations of the TPPS in the United States (U.S.).
The first case study involves a U.S. utility that switched fuels for MATS compliance to a low sulfur, low chlorine, and low mercury western bituminous coal. Dry sorbent injection (DSI) utilizing hydrated lime was continuously used for acid gas trim. Prior to this project, the ESP could only achieve opacity compliance, while injecting hydrated lime, at 70% boiler load.
In the second case study, a utility plant needed to eliminate their reliance on an ESP SO3 conditioning system to reduce the use of activated carbon injection (ACI) for Hg control. Prior to the ESP upgrade, the unit could only achieve full load while utilizing SO3 to help the ESP’s performance. In both the first and second projects, numerous improvements were made to the ESP, including the addition of TPPS, to address MATS compliance.
This paper will identify the prime considerations when upgrading ESPs to achieve lower PM, HCl, and Hg emissions.
Steven Marchigiano, Plant Manager – Duke Energy Crystal River, Duke Energy
John Knapik, Engineering Manager, Babcock & Wilcox