RADFORD, Va. - Environmental regulations is the driver of power plant conversions from coal to natural gas at Radford Army Ammunition Plant. More stringent air emissions regulations imposed by federal and state environmental agencies and the age of the RFAAP power house, more than 75 years, is making the switch a natural progression. Approximately five years ago, several factors converged to spur a renaissance in natural gas for power generation, and that renaissance continues through to the present.
A combination of sustained low natural gas prices and more stringent environmental regulations has driven more coal powered plants to seriously examine natural gas as a fuel option for energy generation. Indeed, according to the U.S. Energy Information Administration's 2014 Annual Energy Outlook, coal currently supplies about 41 percent of the nation's power versus 27 percent from natural gas. But by 2035, the agency anticipates natural gas will be the primary fuel for electricity generation.
Besides adding costly environmental equipment or closing and replacing coal capacity (also a costly proposition), a third avenue exists for a limited number of utility plants. Fuel switching is an attractive and economical option for RFAAP that must maintain a certain generating capacity to maintain production and can't justify the cost of these other options. RFAAP has decided to build a new NG facility and not convert.
The most likely candidate for a coal-to-gas switch are 50-plus year old units, less than 300 megawatts in capacity. The majority of these older, inefficient units are located in the eastern United States. Typically, these plants have limited or no air quality control systems already in place, but the RFAAP coal fired power plant is heavily monitored. RFAAP is self-reporting to Virginia Department of Environmental Quality and typically has multiple permit excursions every week.
Although old RFAAP's coal fired plant still has a decade or more of useful service life due to upgrades that had been performed, the plant still is providing peaking capacity where and when it is needed. Environmental compliance is the unique driver in the conversion with portions of the current power plant remaining a valuable asset that RFAAP is not eager to abandon. The coal fired boilers will be disassembled and sold for scrap and eventually the turbines will move or new turbines will be moved to the site of the natural gas fired boilers. This portion of the project remains unfunded.
So there is significant incentive to keep those assets functioning in some way. If an owner can convert and continue to operate that plant on gas, it allows them to continue to harvest some value from these assets. RFAAP will continue to use the turbines housed in the old power house for electric power generation. The steam provided by the natural gas boilers is used in production at RFAAP and provides comfort heat as well. The power generation is a use of steam for RFAAP. It also allows the Army to convert quickly to gas while planning for a future co-generation facility.
The increase in natural gas supply is a result of gas production from unconventional sources, such as shale gas or tight gas, which is trapped in deep impermeable rock or non-porous limestone and sandstone. Natural gas has much lower emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) as compared to coal. Carbon dioxide (CO2) emissions are approximately 50 percent lower than coal when burned to generate electricity. As a result, natural gas power plants can be constructed and operated with fewer environmental control systems than a coal-fueled plant with similar output under current environmental regulations.
Interestingly, Mercury and Air Toxics Standards (MATS) compliance and federal/state regulations - not the current push to limit greenhouse gas emissions through regulations like EPA's proposed Rule 111(d) - have been the primary regulatory factors driving coal to gas conversions.
THE PROS AND CONS OF FUEL SWITCHING AND TECHNICAL CONSIDERATIONS
Every potential project begins with an extensive study phase in which a number of pros and cons must be considered before undertaking a project that could cost several tens of millions of dollars. Typically from study phase to delivery of equipment takes about two-and-a-half years, although some projects have taken four to five years to develop.
One of the most basic decisions in a conversion is to determine whether a complete replacement of the plant's existing coal burners is required or to simply modify them for gas firing. Ultimately, this depends greatly on the age of the equipment and environmental regulations it must meet post conversion.
Technical issues can greatly impact the viability, performance, cost, and reliability of any steam generating unit firing natural gas when such unit was not originally designed to do so. These issues are very specific to the original design of the boiler, including, but not limited to, its physical geometry, materials of construction, remaining component life, desired operating capacity and boiler steaming conditions required to satisfy the steam turbine-generator set.
Depending on the type of coal currently burned in a plant, switching to burn natural gas could result in a notable drop in plant heat rate and loss of efficiency. For example, when switching from bituminous coal to gas, plant operators could see an approximately four percent degradation in efficiency due to the high moisture content of natural gas. However, the current low price of natural gas may make up for at least some of the cost of this loss of efficiency.
A WORD ABOUT INFRASTRUCTURE
From a manpower perspective, it takes fewer personnel to operate and maintain a gas-fired plant than it does a coal plant. There are a lot of people involved with unloading and handling of coal used as fuel. Not so with natural gas. Significant manpower is also used in maintaining plants that run on coal due to coal's inherent erosive and corrosive nature as a fuel.
Overall, switching to gas, even at current gas prices, is generally not an easy choice economic choice considering the capital cost, fuel costs, cycle efficiency, and future regulatory uncertainty.
The most obvious change to a power plant that switches from coal to gas will be the modifications to the fuel handling, storage and distribution equipment. This can be one of the most significant costs in a coal to gas conversion project. In many cases, existing coal plants lack sufficient infrastructure for gas delivery and distribution and it must be constructed.
The plant must receive natural gas via a pipeline spur from a local main transmission line. If a spur does not currently exist, the plant will need to evaluate the costs and activities, including permits and land rights, associated with constructing a new spur. RFAAP was able to get a natural gas line enlarged to handle our demand. This dedicated line into the plant took an around the clock effort by the local utility.
LOOKING TO THE FUTURE
"The deadline for MATS compliance, the primary driver of this market, is upon us now," said Lt. Col. Alicia Masson, former RFAAP Commander. Her efforts have been noted by Army leaders. RFAAP has worked with VDEQ regarding the compliance issues with the coal fired plant and the conversion to natural gas. So most plant operators have already settled on a compliance strategy and are in the process of implementing it.
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