MATS Mercury and HCl Control Requires More Power to the ESP and Careful Consideration of ESP Design Details


Presented at the: Power Plant Pollutant Control “MEGA” Symposium
August 16-19, 2016
Baltimore, MD

John A. Knapik1, Jia (Erick) Ma1, Steve Burgund2, Morgan Beveridge3, Steve Marchigiano3, and Michael Williams3; 1 The Babcock & Wilcox Company, Barberton, Ohio, 2Dynegy Wood River Generating Station, Alton, Illinois, 3Duke Energy, Crystal River Generating Station, Crystal River, Florida.

ABSTRACT

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.

The third case study describes the simple addition of TPPS to a cement kiln ESP and the resultant increase in ESP power and reduction in PM emissions. This project demonstrates the important role that ESP power supplies play in improving PM collection efficiency.

This paper will identify the prime considerations when upgrading ESPs to achieve lower PM, HCl, and Hg emissions.

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