Consumers Energy is sticking with its plan, announced in December 2011, to mothball its seven smallest coal-fired units by the end of 2014, a utility official said in testimony filed Sept. 19 with the Michigan Public Service Commission
Consumers Energy Director of Staff, Electric Generation David Kehoe filed testimony as part of a rate increase application. Consumers Energy is the utility subsidiary of CMS Energy (NYSE: CMS).
The units that will be mothballed are Whiting Units 1-3, Cobb Units 4-5, and Weadock Units 7-8. The retirement as of around Dec. 31, 2014, is prior to the compliance deadline for the Michigan Mercury Rule (MMR). Because Consumers Energy does not intend to install Air Quality Control Systems (AQCS) on the seven units, they will be mothballed.
These units could operate beyond the end of 2014, Kehoe noted. The Environmental Protection Agency (EPA) signed a rule to reduce emissions of toxic air pollutants from power plants on Dec. 16, 2011, he explained. These mercury and air toxics standards (MATS) for power plants will reduce emissions from new and existing coal and oil-fired electric utility steam generating units (EGUs). Now that MATS is in place, there are efforts being made to rescind the Michigan Mercury Rule. The EPA’s Clean Air Act requires compliance within 3 years plus 60 days of the Federal Register’s approval. “Therefore, compliance would be required by April 16, 2015, and the units would not need to be mothballed until this date,” Kehoe said.
The EPA has estimated there are, nationwide, around 1,400 generating units affected by MATS. “Because market prices are determined by supply and demand, if enough units retire, electric prices could increase to a point where installing AQCS on the smaller units would be cost-effective,” Kehoe said. “On the other hand, if electric prices remain relatively unchanged, installing AQCS on the seven smaller units would not be cost-effective.” Mothballing the seven smaller units in 2015, rather than 2013, affords the company additional time to make an informed decision, he said.
Mothballing the units requires the approval of the Midwest ISO, which has not yet been received. Consumers filed three applications with MISO (one for each site – Cobb, Weadock and Whiting) in February.
Upcoming emissions control work includes:
- In 2013 and 2014, Consumers will invest at Campbell Units 1-2 in AQCS consisting of Spray Dry Absorber (SDA)/Dry Sorbent Injection (DSI), Activated Carbon Injection (ACI), Pulse Jet Fabric Filters (PJFF) and completion of the Selective Catalytic Reduction (SCR) unit at Campbell Unit 2.
- In 2012, Campbell Unit 3 will add fly ash storage silos and improve the wet bottom ash system. In 2013 and 2014, Unit 3 will install the next layer of SCR catalyst and additional AQCS, which are SDA, ACI, and PJFF.
- At Karn Unit 1, in 2013, investments in SDA and ACI will continue. In 2014, the company has scheduled an overhaul and upgrade at Karn 1.
- In 2012, Karn Unit 2 will install an additional layer of SCR catalyst. In 2013, new throttle and governor valves will be installed, new low pressure rotors and cylinders will be installed and investments in SDA and ACI will continue at Karn Unit 2.
The Consumers coal-fired units and net power ratings are:
- J H Campbell 1-2, 615 MW, West Olive, MI;
- J H Campbell 3, 770 MW (owned share), West Olive, MI;
- D E Karn 1-2, 515 MW, Essexville, MI;
- B C Cobb 4-5, 312 MW, Muskegon, MI;
- J R Whiting 1-3, 325 MW, Erie, MI; and
- J C Weadock 7-8, 310 MW, Essexville, MI
At Campbell Unit 3, Consumers owns 93%, with other entities owning the remaining 7%. Thus the 770 MW capacity reported is 93% of the unit size.
Details offered on air emissions control planning
More details on the emissions planning of Consumers was provided by Nancy Popa, the Manager of Long Term Strategy at Consumers. Popa assumed this position as of Aug. 1, 2012. For the previous three years Popa was the Manager of Environmental Services.
ACI coupled with a particulate matter collection device is required to achieve the mercury reductions required by both the MATS and MMR, Popa said. Some form of Flue Gas Desulfurization (FGD), which also needs to be paired with a particulate control device, is required in order to achieve the reduction of acid gases required by MATS. For mercury control, PJFFs were installed at Karn 1-2 in 2011 and 2010 respectively to comply with the MMR/MATS. The PJFF at Campbell 1 is currently in the engineering phase, for Campbell 2 the PJFF is in the construction phase and the PJFF at Campbell 3 is in the equipment fabrication phase. The ACI systems are much smaller in scale and will be fit into the PJFF construction schedule.
Another approach to mercury removal utilizes the electrostatic precipitator (ESP) for particulate control following the ACI system in lieu of PJFFs. The Electric Power Research Institute (EPRI) data indicated that significant ACI injection rates (> 4 lb/million actual cubic feet) are required to achieve high levels of mercury removal with ESP operation. Consequently, the high solids loading can result in an increase in particulate emissions above the limits, Popa wrote.
Consumers Energy has evaluated the impact of ACI on its ESPs and determined that injection rates of this magnitude resulted in an increase in particulate emissions above the significance level that would require installation of best available control technology. This study was performed by Air Consulting Associates. PJFF are currently defined by EPA as best available control technology. This led Consumers to pursue these pulse jet fabric filters coupled with ACI as the technology of choice for removal of mercury.
The industry has the most experience with carbon-based sorbents such as activated carbon. But, there are non-carbon sorbents available in the market today. Once an injection system is installed, sorbent testing can identify the optimum sorbent (carbon or non-carbon) for the individual unit that results in the most cost-effective compliance option, Popa said. Based on this information, Consumers has chosen PJFF and ACI as the mercury technology of choice.
For acid gas control, Consumers Energy is installing SDA at Karn Units 1-2 and Campbell Units 2-3. The SDAs at Karn 1-2 are currently in construction and projected to be operational in 2014. For Campbell 2 the SDA is in preliminary engineering and at Campbell 3 the SDA is in the equipment fabrication phase.
At the current time, plans for Campbell 1 are to install DSI. A demonstration test of DSI at Campbell 1 will be conducted this fall. If the test results don’t turn out well, then Campbell 1 would be required to install an SDA.
Consumers only considered SDA and DSI because wet scrubbers are best suited for units that burn higher sulfur coals, Popa noted. Consumers mostly burns low-sulfur Powder River Basin coal.
For Consumers’ units that burn blended coal, at least a 90% reduction in acid gases is needed for MATS compliance. For those units (Karn 1-2 and Campbell 2), DSI cannot provide the required reductions and assure reliable operations. Consumers Energy believes, however, that DSI can be a feasible MATS compliance option for Campbell 1, which burns 100% western coal, thus the testing to be done this fall.
“Our strategic approach to compliance which has included switching to lower cost and lower sulfur western coal and allowance purchases has allowed us to defer significant capital investments,” Popa wrote. “These actions have been in the customer’s best interest. At this juncture, moving ahead with the investment in control equipment for Karn and Campbell is essential. Our technology decisions have been based on specific unit designs, consideration of new and leading edge technologies and economic evaluations that consider both the capital and O&M expenditures. In the case of Campbell 1, our reconsideration of DSI in lieu of SDA results in approximately $100 million in reduced capital expenditures if the demonstration testing provides favorable results.”
Consumers eliminates renewables to replace mothballed units
David Ronk Jr., Director for Electric Transactions and Resource Planning at Consumers, said in Sept. 19 testimony that Consumers is looking at replacing the seven coal units with various things, including renewables and natural gas. Modification of one or more of the existing seven coal units to use natural gas remains an option at this time. Consumers decided that the cost of power from renewable resources and new generators fueled by coal are likely to be more expensive than the cost of purchasing zonal resource credits, purchasing an existing gas-fueled plant or building a new gas-fueled combined cycle plant.
As for why Consumers isn’t just putting one or more of those seven units in mothballs now, Ronk said the seven units are currently economic compared to the cost of energy and capacity that the company would incur to replace their production. Also, Consumers anticipates some transmission system modifications will be needed when those seven coal units are not in service. It is unlikely that those modifications can be made between now and April 2015. The company also has long-term fuel arrangements that would be costly to terminate if the generating units are removed from service earlier.
When these seven units are mothballed, Consumers will become more dependent on gas than it has been on coal and thus additional reductions in coal-fueled capacity make the company’s fuel supply less diverse, Ronk pointed out.
If the utility were to go a step further and remove the remaining five coal units from service, Consumers anticipates that the effects on the electric transmission system will be much more expensive.
Also, a study was done to identify the conceptual gas infrastructure requirements and costs to support the replacement of the remaining five coal units located at Campbell and Karn with natural gas-fueled combined cycle plants utilizing F-class combustion turbines. The study considered the gas supply requirements associated with installation of 1,200 MW at the Campbell site and 600 MW at Karn. The results of the study indicate the conceptual costs for the gas infrastructure are significant primarily due to the length and diameter of the gas transmission pipeline required to interconnect to the closest major gas transmission system and due to the relatively high gas delivery pressure requirement of F-class combustion turbines, Ronk wrote.