The Florida Department of Environmental Protection on Dec. 8 issued a final air construction permit to Tampa Electric that authorizes the construction of four new hoppers at the coal-fired Big Bend power plant and the removal of the existing Dravo unloader used to store and transfer solid fuels from ships or barges.
Big Bend is a nominal 1,892-MW facility located on Tampa Bay on Florida’s Gulf Coast. It takes in waterborne coal and petroleum coke at the site, with most of that fuel consumed at Big Bend itself, and some of it trucked inland to the Polk gasification unit. Big Bend consists of Units 1–4; four steam turbines electrical generators; two simple-cycle combustion turbine 4A and 4B sharing a common electrical generator; solid fuels, fly ash, limestone, gypsum, slag, bottom ash storage and handling facilities; and, fuel oil storage tanks.
The four new hoppers will accommodate three self-unloading vessels (ships or vessels). The new hoppers contain angled chutes that discharge solid fuel immediately above the existing conveyor.
Tampa Electric is a unit of TECO Energy (NYSE: TE).
Also, on Nov. 26 the department put out for comment a draft air permit that covers reduction of SO2 emissions and ambient impacts from the Big Bend facility. Specifically, the permit establishes an SO2 emissions cap of 3,162 pounds per hour (lb/hour) based on a 30-day rolling average over Units 1–4 combined, to be effective on Oct. 16, 2015. In addition to the recent improvements to the wet flue gas desulfurization (FGD) systems, which help with compliance, Tampa Electric is replacing the existing fuel igniters and associated equipment to allow Units 1-4 to burn natural gas instead of fuel oil during startup, shutdown and flame stabilization.
This new emissions cap reduces SO2 emissions and ambient impacts in and around the SO2 non-attainment area in Hillsborough County, Fla., where the plant is located.
Over the years, Tampa Electric has made substantial upgrades to the controls to reduce SO2 emissions including: the installation of wet FGD scrubbers; splitting Units 3 and 4 ducts to exhaust through individual stacks and to remove FGD bypass capabilities; and removing FGD bypass capabilities for Units 1 and 2 prior to exhausting through a shared stack.
More recently, the DEP said, Tampa Electric made the following improvements to enhance the performance of the FGD systems to increase removal efficiency and further reduce SO2 emissions:
Units 1 and 2 FGD System
- Add FGD tower wall ring to deflect the flue gas away from the walls of the towers.
- Replace slurry nozzles in FGD tower absorber with new double-headed nozzles to increase the number of spray nozzles and enhance gas-liquid contact within the towers.
Units 3 and 4 FGD System
- Replace slurry nozzles in FGD Absorber Towers A and B with new double-headed nozzles to increase the number of spray nozzles and enhance gas-liquid contact within the towers for better SO2 removal efficiency.
- In FGD Absorber Towers C and D: replace slurry nozzles with new redesigned spray headers to increase the number of spray nozzles and enhance gas-liquid contact within the towers; install larger motors on the recycle pumps for the spray headers to boost head pressure and improve the spray pattern; and relocate the dual-flow trays in each tower to a lower elevation to increase effectiveness.
- Replace the flue gas inlet ductwork to FGD Absorber Tower C to reduce pressure loss and balance the uneven gas flow distribution between Absorber Towers C and D.
“Although TECO requested an effective date of August 31, 2017, the wet FGD system is fully functional with recent upgrades in place that were installed to ensure compliance with the new Mercury and Air Toxics Standards (MATS) rule,” the department said about compliance timing with the new SO2 limit. “Also, existing SO2 emissions data shows that the combined emissions from Units 1–4 previously met the proposed cap more than 96% of the time – without an operational target and before the scrubber upgrades. The Department established an effective date of October 16, 2015, which provides an additional six months after the MATS compliance date of April 16, 2015. This is adequate time to add the new monitoring requirement to the CEMS software and provides consideration for integration with the new MATS requirements. The Department believes the proposed effective date for the SO2 emissions cap reflects the intent of complying as expeditiously as practicable.”