Seattle Steam Company

Privately owned Seattle Steam Company was established in 1893 and supplies steam to over 200 buildings in the Seattle Business and First Hill Districts, including 3 hospitals. The company has over 18 miles of piping buried under approximately one square mile of the city’s streets and infrastructure. Because of their inaccessibility, the long-ago corroded condensation lines have not been replaced. Consequently, no condensate returns, although many customers make use of it (e.g., restrooms, laundry, dishwashers, etc.)

In one of our earlier projects, Direct Contact LLC (DCLLC) installed a 9-foot diameter, 21-foot tall Hydrothermal Recovery system (HTR) on the rooftop of the historic building. This vessel captures and condenses flue gas, using the energy to add recaptured condensate and pre-heat the make-up water. Exhaust gas from the HTR is added back to the flue exhaust. Gas flows into the vessel at around 45,000 ACFM at 290-350°F (145°F wet-bulb) and leaves at 108-118°F, saturated. Make-up water is heated approximately 133°F prior to feeding it to the de-aeration tank. DCLLC unit atop Seattle Steam Company building. Use of the HTR has resulted in a 6.3% overall plant efficiency improvement and daily savings in excess of $2,500. Some notable aspects of this project were the addition of a structural steel grid (partially visible in the photo above) atop the building’s walls to support the weight of the HTR and fan, in addition to installing pump, piping, and human access in a very tight space. (Testimonial)

With over 180 customer buildings in a 2-square-mile area of San Francisco, NRG Energy Center has over 13 miles of steam mains, some installed prior to 1906. Six natural-gas-fired boilers produce 40,000-to-350,000 lb/hr of steam with no condensate return.

DCLLC’s Hydrothermal Recovery (HTR) system extracts energy from both the boiler flue-gases and the de-aerator steam vent and uses this energy to heat plant make-up water from 55°F to 146°F, prior to sending it to the de-aerator. The result is a 6.7% reduction in natural gas consumption. Further, the HTR recovers flue-gas water vapor, resulting in a 3.2% reduction in plant make-up water, and increasing peak capacity by 20,000 LB/HR. Annual gas savings add up to $880,000, with water and sewer savings at $45,000. This project had a payback of 1.2 years.

The HTR has no impact on pre-existing economizers and can be shut down and cleaned in place without impacting plant operations. (Testimonial, NRG Publication)