The Environmental Compliance Strategy for Georgia Power has included recently, in part for federal Mercury and Air Toxics Standards (MATS) compliance, a number of coal-fired power retirements and coal-to-gas conversions.
The latest version of the strategy was filed on Jan. 29 by Georgia Power at the Georgia Public Service Commission as part of the utility's Integrated Resource Plan, which is lodged with the commission every three years. Georgia Power is a unit of Southern Co. (NYSE: SO).
Through 2014, Georgia Power has invested approximately $4.7 billion in capital projects to comply with applicable environmental statutes, including the Clean Air Act; the Clean Water Act; the Comprehensive Environmental Response, Compensation, and Liability Act; the Resource Conservation and Recovery Act; the Toxic Substances Control Act; the Emergency Planning & Community Right-to-Know Act; and the Endangered Species Act.
In Georgia Power’s Annual Report on Form 10-K for the year ended Dec. 31, 2014, which was filed with the Securities and Exchange Commission Georgia Power projected that base level capital expenditures to comply with existing statutes and regulations will be a total of approximately $0.8 billion from 2015 through 2017, with annual totals of approximately $0.3 billion, $0.2 billion, and $0.2 billion for 2015, 2016 and 2017, respectively.
Georgia Power has installed 15 selective catalytic reduction systems (SCRs) for NOx control. SCRs are currently installed and operating at the following Georgia Power units:
- Plant Bowen Units 1-4
- Plant Hammond Unit 4
- Plant Wansley Units 1 and 2
- Plant Scherer Units 1-3
- Plant McDonough Units 4-6
- Plant McIntosh Units 10 and 11
Georgia Power has installed flue gas desulfurization (scrubbers or FGDs) on 13 units. Scrubbers are currently installed and operating at:
- Plant Bowen Units 1-4
- Plant Hammond Units 1-4 (single scrubber vessel)
- Plant Wansley Units 1 and 2
- Plant Scherer Units 1-3
Georgia Power has installed and is operating baghouses with activated carbon injection (ACI) to reduce mercury emissions at Plant Scherer Units 1-3, which are fired with Powder River Basin coal.
Georgia Power has installed the following equipment for compliance with MATS:
- Bowen Units 1 and 2: ACI and alkali sorbent injection (ALK) systems upstream of the electrostatic precipitators (ESPs); Mercury Re-emission Control Systems (MRCS)
- Bowen Units 3 and 4: Baghouses with ACI and ALK
- Hammond Units 1-4: ACI and ALK upstream of the ESPs
- McIntosh Unit 1: ACI and Dry Sorbent Injection (DSI); Fuel switch to Powder River Basin (PRB) coal
- Wansley Units 1 and 2: ACI and ALK systems upstream of the ESPs; MRCS
Georgia Power is evaluating the use of Halogen Injection (i.e. Calcium Bromide or Calcium Chloride) at Plant Scherer Units 1-3.
Georgia Power has switched the following units from coal to natural gas:
- Plant Yates Units 6 and 7
- Plant Gaston Units 1-4, representing Georgia Power’s share of this Alabama plant.
In addition, after thorough evaluation of the projected compliance costs of upcoming environmental regulations, such as the Georgia Multipollutant Rule or MATS, combined with the anticipated cost of other current and pending environmental regulations, Georgia Power decided to retire rather than incur additional environmental control costs for the following mostly cola-fired units:
- Plant Branch Units 1-4
- Plant Kraft Units 1-4
- Plant McManus Units 1 and 2
- Plant Yates Units 1-5
- Plant Mitchell Unit 3 (Georgia Power is seeking decertification of this unit in the 2016 IRP)
Georgia Power has slashed emissions levels in recent years
Between 1990 and 2014, Georgia Power investments have reduced NOx and SO2 emissions by approximately 87% and 91%, respectively (including Georgia Power’s share of Gaston 1-4). The combination of baghouses, SCRs, and scrubbers has reduced Georgia Power’s 2014 mercury emissions by approximately 80% from 2005 levels (including Georgia Power’s share of Gaston 1-4).
These reductions were achieved by fuel switching to lower sulfur coals and the installation of low-NOX burners, selective catalytic reduction systems, and flue gas desulfurization (or scrubbers) at plants across the system. In addition, state regulations have required the reduction of mercury emissions in Georgia.
Units that have scrubbers are generally able to meet the SO2/acid gases limit under MATS, but compliance with the mercury and particulate limit and the need for baghouses and other controls had to be further evaluated. Units that fall into this category include the coal-fired units at Plants Bowen, Hammond, Wansley, and Scherer. In addition to existing scrubbers, the units at Plant Scherer also already operate existing baghouses with activated carbon injection for mercury control.
For mercury, significant reductions are achieved on bituminous coal-fired units through the mercury reduction and capture co-benefits of the SCR and scrubber. However, additional incremental reductions will be needed under certain operating conditions on all units at Plants Bowen, Hammond, and Wansley to comply with the MATS mercury limit on a continuous basis. These reductions can be achieved with the installation of activated carbon injection and alkali sorbent injection systems upstream of either an existing electrostatic precipitator or a baghouse. The activated carbon is injected into the flue gas to capture the mercury resulting from combustion of coal in the boiler. ALK is defined as hydrated lime that is injected into the flue gas upstream of the activated carbon to enhance the effectiveness of the activated carbon. The hydrated lime and activated carbon will then be collected in the electrostatic precipitators or baghouses.
Whether a unit requires a baghouse or can use its existing electrostatic precipitator with the activated carbon and hydrated lime depends on unit-specific characteristics. Baghouse retrofits are necessary for units, such as Bowen Units 3 and 4, that tend to have higher mercury emissions and that require additional particulate matter control to ensure compliance. For units that will not install baghouses, optimization of the existing electrostatic precipitators has been performed as needed to maintain emissions performance with the additional loading of the injected carbon and hydrated lime. In addition, scrubber additives will be used as needed to help control mercury re-emission, which can occur under certain conditions in the scrubber and can counteract the reductions provided upstream of or by the scrubber. The use of scrubber additives in a mercury re-emission control system can also help prevent over-injection of activated carbon and lime into the baghouse or precipitator, thus minimizing the ongoing operational cost of the controls.
Georgia Power is installing ACI and ALK upstream of the electrostatic precipitator at Plant Bowen Units 1 & 2, Plant Wansley Units 1 & 2, and Plant Hammond Units 1-4, and ACI and ALK upstream of a baghouse at Plant Bowen Units 3 & 4. Non-baghouse units have performed electrostatic precipitator optimization, and Bowen Units 1 & 2 and Wansley Units 1 & 2 plan to install mercury re-emission control systems.
For its PRB coal-fired units at Plant Scherer, the company expects to achieve the necessary mercury reduction most cost effectively by employing a combination of already planned SCR, scrubber, carbon injection, and baghouse systems, and potentially the application of calcium bromide/chloride to the fuel. The application of calcium bromide/chloride to the fuel is intended to reduce the amount of carbon injection that is necessary to achieve continuous mercury compliance by enhancing the mercury removal by the scrubbers. Because the cost of carbon is relatively higher, use of calcium bromide/chloride may reduce overall O&M expenses related to operating the environmental controls and help ensure compliance.
Given the stringency of the final MATS requirements and the reduced operational flexibility expected as a result, additional MATS compliance measures will be implemented at Bowen, Hammond, and Wansley to optimize the balance of plant performance and ensure reliability of mercury, acid gas, and particulate controls.
This article was republished with permission.