Reliable steam supply is one of many problems a correctional institution must address when demanding fail-safe system design. But it was of particular concern to Fayette Thermal, under contract with the PA Dept of Corrections to supply steam to its new 672,000 sq ft State Correctional Institution Fayette. High efficiency, fluidized bed coal boilers were selected as the heart of the facility's steam plant, with ultracompact Miura boilers providing a highly reliable instantaneous backup-- a unique business proposition for a unique facility.

Moving a Prison

Since Pittsburgh's old correctional institution has too little capacity, the decision was made to build a new facility in Fayette County, which needed an economic boost. The building site selected was on top of a 400 ft precipice bordering the Monongahela River. Only small communities populate the area around the facility, making it a good isolated location.

Pennsylvania, like many states, mandates that a new state facility must use indigenous fuel. The original design called for three large firetube oil-burning boilers, which would use indigenous oil. However, space constraints made installing the firetube boilers impractical.

Chicken Litter and Turkey Feathers. . .

A closer look was then taken at using indigenous coal, or waste coal. The plentiful supply of waste coal piles in the area made this the most economical long-term solution. That's when Power Consultants, Inc was called in. David Goldsmith, Power Consultants' design engineer, continues the story: "We specialize in building steam facilities using energy from waste fuels, coal being just one of these fuels. Others are chicken litter, tires, plastics, turkey feathers, wood waste, construction demolition waste, and many more. So, we designed and implemented a waste coal fuel system for the steam plant."

With the facility's engineering already completed, the state's budget for changes was limited. So Power Consultants proposed that a private entity, Fayette Thermal, would build, own, operate, and service a free-standing boiler plant (not the central utility plant on the facility grounds) using bituminous coal tailings in high efficiency fluidized bed boilers. They would supply the facility's steam needs under a long-term contract.

The fluidized bed boiler plant would be three quarters of a mile away from the facility, on its own property. It would contain two fluidized bed boilers fired by waste coal, each providing 15,000 pounds per hour (500 HP) of steam. The central utility plant, although too small for firetube boilers, had plenty of room to accommodate another part of the solution, enabling Power Consultants to solve two problems with one proposal.

Instantaneous Backup

When dealing with coal, it is understood that there will be occasional problems. To provide a fail-safe system, Power Consultants had to plan for every eventuality: "When there is a problem with service from coal boilers because a mechanical system fails, an instantaneous backup is paramount. Firetube boilers cannot respond like that."

Although the high efficiency, fluidized bed coal boilers are the heart of the facility's steam plant, Power Consultants chose Miura boilers for a highly reliable instantaneous backup. Since the ultracompact Miura boilers take up a fraction of the space of firetube boilers, they fit easily into the central utility plant. Goldsmith says, "The relatively miniaturized waste coal watertube boilers are over three times bigger than the Miuras. With similar capacities, a Miura that is about 8 ft wide by 12 ft long by 13 ft tall, is dwarfed by the Spinheat® boiler, which is 14 ft wide by 22 ft tall by 18 ft long. And that is just the boiler, without the baghouse and the other backend paraphernalia that goes alongside it."

The Miuras would be located in the institution's central utility plant. Miura sales engineer Jacek Grob, who worked with Power Consultants, said the Miuras were chosen because "Miuras were the only boilers capable of providing a backup in five minutes." In fact, the Miuras are not only acting as backup boilers: right now, until the coal boilers are up and running, the Miura boilers are carrying the entire steam load for the empty facility. According to Goldsmith, "The Miuras fit this scenario extremely well. We've housed three, 300 HP EX gas-fired watertube Miura boilers in the central utility plant, which is on the facility grounds, but outside the secure facility walls. The accommodation is there for a fourth boiler to go in when and if they expand the facility to a larger population. The fluidized bed boilers, which are 3000 ft away -- three quarters of a mile -- from the facility on their own property are connected by a steam line to the central utility plant."

Fayette Thermal owns the three Miuras inside the central utility plant on a lease-back basis, so that eventually, the state will own them. Fayette Thermal operates them all under a 20-year steam sales agreement.

5 Minutes From 0 Pressure To Operating Pressure

"The really important criteria for the design of these plants is instantaneous backup," Goldsmith continues. "I've had a lot of experience with Miuras and am very high on the design and operation of these little units. The Miuras go from zero pressure, cold, to operating pressure in five minutes. That has enormous benefits for an emergency system -- or a backup system.

"Maintaining the steam demand at the correctional facility is quite volatile and that is another reason why we need the Miuras' instant response. For example, as you can well imagine, the inmates have to shower once a day. Just imagine 2000 people showering in a 3 hour period. If the two coal-fired boilers at the top of the hill are chugging along but can't respond fast enough to the steam requirements, then of course, one of these little Miuras kicks on and almost instantaneously supports the additional requirements."

Off-Line Until Needed For Optimum Savings

Goldsmith sees Miuras in his future. "I've got several more projects where the Miuras are not a backup system -- they are going to be on most of the time. These are systems where I can't possibly use coal or another waste fuel to provide the savings that my customers want. What happens with Miuras is that by operating a bank of them as opposed to one or two, you end up with savings associated with having them come on and off as needed -- each of them operating at optimum efficiency. Other boilers have to remain online all the time and resultant load swings cause much lower efficiency and costs you an arm and a leg."