Based on recent gas conversion announcements, existing coal units generating a total of approximately 9,000 megawatts (MW) will be converted to natural gas firing. The major drivers of this trend have been Mercury and Air Toxics Standards (MATS) regulations, New Source Review (NSR) settlements, natural gas availability and pricing, and the uniqueness of each project to deliver electricity at the required capacity, making it economically feasible to convert existing coal-fired units to natural gas firing capability. Some facilities are already environmentally compliant and are adding dual-fuel firing capabilities for fuel flexibility and to capitalize on fuel cost savings.
The existing coal-related equipment, material handling systems, and air quality control systems (AQCS) are generally left in place to help drive economic feasibility of firing natural gas. In certain cases, this equipment can be put into long-term layup with the uncertainties of fuel costs and environmental regulations but with higher operations and maintenance (O&M) costs. AQCS equipment, such as electrostatic precipitators, can be de-energized and wet/dry flue gas desulfurization (FGD) systems can be bypassed.
In some cases, retiring and decommissioning of all coal equipment and AQCS equipment may be the more prudent choice to avoid the costs of long-term layup and operating and maintaining the equipment.
Two recent cases studies are presented in this paper: (1) retiring and decommissioning of all coal equipment and AQCS equipment, and (2) implementing dual-firing capabilities for coal and natural gas, in which suggested O&M layup procedures for coal equipment and pollution control are discussed.
Marc Lemmons, Ronald Kukral, Raj Gaikwad – Sargent & Lundy
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