DTE Electric, during one-year extension periods under the federal Mercury and Air Toxics Standards that run until April 2016, is installing various new air emissions controls on coal-fired units.
DTE Electric, a unit of DTE Energy (NYSE: DTE), on Sept. 30 filed with the Michigan Public Service Commission the latest annual version of its Power Suply Cost Recovery (PSCR) plan, which covers expected expenses in 2016. Barry J. Marietta Jr., employed by DTE Energy Corporate Services LLC within the Environmental Management & Resources division as a Supervisor–Emissions Quality, in that filing outlined the utility’s latest clean-air plans.
Said Marietta about DTE’s biggest coal plant: “Monroe Power Plant will comply by operating flue gas desulfurization (FGD) and selective catalytic reduction (SCR) systems on all four units. The remaining coal-fired units in operation will comply with MATS emission limitations with a combination of Dry Sorbent Injection (DSI) technology and Activated Carbon Injection (ACI) emission control systems by April 2016 as a result of receiving MATS compliance extensions from the Michigan Department of Environmental Quality (MDEQ).”
DTE Electric applied for and received one-year extensions to the compliance date at its coal-fired power plants: Belle River, Monroe, St. Clair, River Rouge, and Trenton Channel. Therefore, the compliance deadline for those five plants is currently April 16, 2016.
DTE Electric currently plans on utilizing ACI technology at Belle River, St. Clair, River Rouge and Trenton Channel. The installation of ACI technology is ongoing at these plants. The installation of FGD and SCR equipment on all four Monroe Power Plant units has been completed. These plans along with utilizing Reduced Emission Fuel (REF), which is coal treated with chemicals for emissions reductions during combustion, will provide compliance for the control of mercury emissions as required by the MATS regulations.
ACI is a dry sorbent technology, which is the most mature technology for the control of mercury emissions from coal-fired boilers, Marietta noted. More specifically, ACI is an engineered system where powdered activated carbon (PAC) is injected into the flue gas ductwork of the power plant. PAC adsorbs vaporized mercury from the flue gas before being removed along with the fly ash by the particulate control equipment, which is electrostatic precipitators (ESPs) in the case of the DTE Electric power plants.
FGD, in use at Monroe, while an effective acid gas technology, requires a significant capital investment. This larger capital investment, however, was prohibitive on the other coal-fired units in the DTE Electric portfolio. An alternative technology to the installation of an FGD is Dry Sorbent Injection (DSI), which is a technology that has been used in the industry to reduce SO3 emissions for some units that burn higher sulfur coals. Hence, the HCl compliance plan includes the installation and operation of DSI technology on units other than the Monroe plant in the DTE Electric portfolio.
The EPA identifies DSI as an alternative to FGD for MATS compliance with acid gas limits and forecasts 44 GW of DSI installations across the country for MATS compliance.
The company’s existing ESPs will continue to be used to remove PM from the flue gas stream. During testing, MATS compliance level PM emissions were able to be achieved with the combination of DSI and ACI sorbents injected into the flue gas prior to the existing ESPs. Tests demonstrated that DSI, using either Trona or SBC, improved the efficiency of the existing ESPs. The increased particulate collection performance allows the existing ESPs to meet MATS PM emission limitations.
Any air systems completed prior to April 2016 will be fired up as completed
As construction of the ACI and DSI systems has progressed, implementation schedules have been updated. Along with continuing to update this schedule, DTE Electric is committed to operating the systems prior to the MATS compliance date should the systems be available at that time. This means that several locations will have operational systems in place in late 2015 with others going into service early in 2016.
A new development in this PSCR plan is that DTE is currently planning to use only BrPAC for mercury control in the ACI systems. This had always been the case for River Rouge and Trenton Channel, and is now the case for Belle River and St. Clair. As engineering, construction and implementation of the ACI and DSI projects progressed, the gap in sorbent costs for standard PAC versus BrPAC became significantly smaller. For comparison, the current cost projection for standard PAC excluding transportation is $0.60 per pound compared to $0.75 per pound for BrPAC. As recently as two years ago, BrPAC was projected to be $1.20 per pound, or double the cost of standard PAC. The difference in pricing between BrPAC and PAC has decreased by 75%. Due to the small gap in pricing, no redundant system was installed to allow for the use of two types of PAC simultaneously.
PAC supply contracts will be fixed, long-term contracts to ensure future price certainty for the plan. In order to use two types of PAC in the ACI process, the installation of redundant storage silos, piping, and other process equipment would have been necessary, which would have resulted in additional capital costs. The lower cost for BrPAC made the installation of redundant systems unnecessary, thereby avoiding additional capital costs.
The ACI system is currently designed to take only one sorbent. In the event that the application frequency of REF is increased to a level at which MATS level mercury reduction is achievable without using BrPAC, then PAC may be used if found more beneficial to the customer.
Marietta wrote: “The consumption of REF at the St. Clair, Belle River, and Monroe power plants is beneficial to DTE Electric’s customers. Its consumption helps the Company comply with the state and federal mercury rules at the lowest reasonable cost as one component of REF is calcium bromide, which is an effective mercury oxidant. The use of REF improves efficiency of mercury removal through this mercury oxidation. At Monroe Power Plant, REF promotes mercury oxidation so that mercury can be more efficiently removed in the FGD system. Although no reduction in sorbent injection rate due to REF has been observed at this time, DTE believes that there is potential to reduce sorbent injection during periods when REF is present as the ACI systems come online and are able to be optimized.”