Waste heat recovery system creates electricity and lowers utility costs

Source: PlantServices.com

Nov 04, 2009

Dresser-Rand Company recently designed and installed a complete waste heat recovery system at the Greater New Haven Water Pollution Control Authority (GNHWPCA). The project included engineering, construction and testing of the waste heat boiler, steam turbine generator set and condenser, ducting, and valves.

Through a long-term service agreement with GNHWPCA, Dresser-Rand will also maintain the facility to achieve the guaranteed electrical production. The system is expected to produce 4.4 million kW hours of electricity per year.

Providing wastewater treatment for the residents of New Haven, Hamden, East Haven and Woodbridge, Conn., the GNHWPCA wanted to reduce its electricity costs, minimize future rate increases and pass those savings on to their customers. The Dresser-Rand project uses waste heat from the wastewater treatment facility to produce steam, powering a Dresser-Rand 750 kW steam turbine generator at the East Shore Water Pollution Abatement Facility. As a result of the project, GNHWPCA expects to reduce its electricity costs by one-third. The GNHWPCA has received financing for 50% of the capital cost for project through the use of Clean Renewable Energy Bonds (CREB’s) at 0% interest for 16 years. The GNHWPCA also received a $300,000 incentive grant from CTDPUC under Connecticut’s legislation for distributed energy facilities.

The GNHWPCA water treatment process involves removing sludge, or sewer system waste, from the water, reducing the moisture content to a combustible level, and burning the dried sludge in a multiple hearth furnace. The resulting exhaust gas is scrubbed to remove pollutants and then released to the atmosphere.

Dresser-Rand’s waste heat recovery solution routes the exhaust gas directly from the furnace to a waste heat boiler, creating steam. The steam powers the turbine generator set, producing electricity in a closed loop cycle. The exhaust gas is returned from the boiler to the scrubber and out the exhaust stack. The process is designed such that it does not change emissions and, therefore, does not impact the facility’s air quality permit. The system simply diverts the gas upstream of the scrubber, extracts a significant amount of the otherwise wasted heat and returns the gas back to the scrubber to continue its normal exhaust path.

This project is Dresser-Rand’s first complete service installation at a sludge incineration facility.

A facility tour is planned for 9 a.m. on Nov. 4. For more information visit www.nebiosolids.org.

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