Start-up of a Combined Heat and Power Generation System for Beneficial Digester Gas Utilization
Authors:
- Joe Rohrbacher - Hazen and Sawyer
The Chesapeake Bay tributary strategy required many wastewater treatment plants (WWTPs) in Virginia to significantly upgrade their facilities to meet the strict nutrient limits imposed by the program. In addition to providing for reliable nutrient removal to meet permit limits, some utilities used these large capital improvement projects to reduce the environmental footprint and operational costs of their facilities by implementing energy efficiency improvements. One such facility was a 15 mgd WWTP that installed a combined heat and power (CHP) system to beneficially utilize digester gas.
The CHP system is comprised of an internal combustion engine, which drives a 335 kilowatt generator to provide electrical power which is used throughout the WWTP, reducing the facilities purchase of electrical energy. Waste heat from the engine and exhaust is captured and used to heat the digesters. In addition a new boiler was installed to provide supplemental heating during cold weather conditions.
The CHP system has been installed and is currently undergoing start-up. Initial start-up issues have included incorrectly installed internal piping for the CHP system by the CHP supplier’s mechanical subcontractor, the need for straining of non-potable water used in the heat exchanger for cooling the unit and leakage issues with the enclosure containing the CHP system. Although these challenges have presented themselves, the manufacturer and supplier have teamed with the engineer and owner in resolving these issues and ensuring a successful final installation. The purpose of this presentation is to further discuss the start-up and testing experience and describe the lessons learned that can be applied to future combined heat and power projects.
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