Always Have a Backup Plan
The new 672,000-sq.-ft. Pennsylvania State Correctional Institution in Fayette County sits atop a 400-ft. precipice that overlooks the Monongahela River in a sparsely populated area of the state. Due to its location and budget constraints, the state had to be creative when it came to selecting and installing systems for the prison, and the boiler system was no exception.
The new 672,000-sq.-ft. Pennsylvania State Correctional Institution in Fayette County sits atop a 400-ft. precipice that overlooks the Monongahela River in a sparsely populated area of the state.
Due to its location and budget constraints, the state had to be creative when it came to selecting and installing systems for the prison, and the boiler system was no exception. The original design called for three large firetube oil-burning boilers. Several states, Pennsylvania included, require new state facilities to use indigenous fuel. Because there are oil supplies in the northwestern portion of the state, planners considered the use of fire-tube oil-burning boilers. However, this possibility was rejected, as space constraints made installing these boiler types impractical.
As such, the state began to look at alternative fuel sources, such as coal and waste coal. As there are waste coal reserves in the southern part of the state, the facility would be able to stay within the boundary of using indigenous fuels. In the end, this fuel source was chosen, as it was deemed the most economical long-term method of generating steam.
But as the engineering for the facility had already been completed, the state's budget for changes at this stage was limited. Power Consultants, which designed the system, called upon a private entity, Fayette Thermal—both firms are based in Carlisle, Pa.—to build, own, operate and service a free-standing boiler plant that would reside separately from the central utility plant on the prison grounds. The independent plant would use bituminous coal tailings in high-efficiency fluidized bed boilers. The boiler plant was constructed 3,000 ft. from the facility on its own property and contains two fluidized bed boilers fired by waste coal readily available from the area. Each boiler provides 15,000 lbs./hr. (500 hp) of steam.
Backing it up
Though Power Consultants and Fayette Thermal had put together an admirable boiler system, all involved parties realized the need for a reliable backup system. "When there is a problem with service from coal boilers because a mechanical system fails, an instantaneous backup is paramount," says David Goldsmith, Power Consultant's design engineer. "Fire-tube boilers cannot respond like that."
The firm chose to install ultra-compact boilers, which take up a fraction of the space of the fire-tube boilers, in the central utility plant; they measure roughly 8 ft. x 12 ft. x 13 ft each. Besides the smaller size of the backup boilers, they are also able to respond quickly; they can provide backup in five minutes. Additionally, before the prison opened and the coal boilers were up and running, the backup boilers carried the entire steam load for the empty facility. Three backup boilers are currently housed at the prison, and space is available for a fourth boiler should the facility expand to accommodate a larger population.
"The really important criteria for the design of these plants is instantaneous backup," Goldsmith says. "[These boilers] go from zero pressure, cold, to operating pressure in five minutes. That has enormous benefits for an emergency system or backup system."