Overview

The Department of Corrections (DOC), State Correctional Institution (SCI) Dallas’s heating, domestic hot water, cooking, and laundry needs were served by a central steam plant utilizing a combination of coal fired watertube and oil fired firetube boilers. SCI-Dallas’s plant was operating year-round to serve the 2,000+ inmates and 600+ employees on-site daily. The existing coal boilers were oversized for the current steam load demand and could not be operated efficiently much of the year, forcing SCI-Dallas to rely on their oil boilers when the coal boilers were unable to be fired. Furthermore, the coal boilers would require significant upgrades in order to comply with new environmental emission regulations.

At the central wastewater plant, SCI Dallas was paying an annual fee in excess of $200,000 associated with sludge hauling, due to high water content in the sludge. Historically, the treatment process had incorporated a method of manually raking the sludge to reduce liquid content, but both the practice and the sludge drying “greenhouse” where the raking occurred were abandoned years ago, with no auxiliary process in place to address water removal.

DOC recognized an opportunity to convert to gas (a cheaper fuel source) and identified several other timely opportunities, including sludge hauling to reduce the annual energy consumption of the facility, and decided that the project qualified for Pennsylvania’s GESA (Guaranteed Energy Savings Act) program.

Entech completed a Utility Master Plan (UMP) to evaluate options for the central utility plant at the correctional facility. Once the State selected the options from the UMP, we teamed with Energy Systems Group (ESG) on an Investment Grade Audit (IGA) to develop the scope of work for SCI Dallas. ESG was selected to be the ESCO (Energy Service Company) for the project, and we continued to work with them on the design of the steam plant and wastewater treatment plant.

The selected ECMs replaced SCI-Dallas’ existing coal with new natural gas and oil-fired boilers, and modified their wastewater treatment plant to improve sludge dewatering. A total project cost of $19.9M, with annual energy savings of $2.25M, results in a total energy savings of $34.5M over the next 15 years.

Central Heating UMP/IGA:
We evaluated the 30 year life cycle costs of the following four primary heating options to calculate a net present value (NPV). For the new central boiler installation options, we evaluated both 800 Hp firetube and 800 Hp watertube boilers and performed a life-cycle cost analysis to allow the State to decide which boiler types they wanted:

1. Convert existing coal boilers to natural gas boilers
2. Install new natural gas boilers
3. Upgrade existing coal boilers to pass environmental regulations
4. Decentralize plant with natural gas condensing boilers in each building

The decentralized option presented the lowest NPV, but SCI-Dallas was not comfortable abandoning their central plant, so they chose to go with the second lowest NPV and install new natural gas boilers.

Wastewater Treatment Plant IGA:
SCI-Dallas has a .45MGD biological process wastewater treatment plant on-site. In the baseline year, SCI-Dallas produced and shipped out for disposal over 1.4MG of sludge. An estimated 1.5% of this sludge was solids. We recommended sludge process improvements to reduce the liquids in the sludge, thus reducing the cost to dispose of the sludge.

Design:
Boiler Replacement:
We provided design to install new natural gas boilers, which will provide $1.8M in energy savings annually for SCI-Dallas. We designed the central boiler plant equipment layout, electrical, structural and connection to the existing steam distribution system including the following equipment:

• Two Gas/#2 Oil Fired 800 Hp Cleaver Brooks Watertube Boilers
• 239 Hp Cleaver Brooks Flex Tube Boiler (summer boiler)
• 45,000 lb/hr Deaerator (skid mounted with pumps)
• Surge Tank and Condensate Pumps

Wastewater Treatment Plant Upgrade:
We modified an abandoned clarifier and upgraded it into a sludge thickening tank; Ovivo cartridge membranes were added to existing aerated digesters to increase the volume of solids in the sludge to 3%. The sludge reduction will result in a 34% annual savings or $83,000 in sludge disposal fees.