Condensing Stack Economizer

A condensing stack economizer is a smart energy-savings solution for industries with existing boiler systems that require pre-heated water. A stack economizer can recover up to 80% of waste heat from conventional gas-fired boiler exhaust while freeing up steam for production purposes and raising overall energy efficiency to nearly 100%. What’s more, using an economizer with a boiler can reduce fuel costs by as much as 25% and generally pays for itself within the first year.

Water temperatures exceeding 140°F can be achieved while lowering the exhaust temperatures of the boiler from 350 or 400° to as low as 80°F. The heated water can be used for numerous processes, including area wash downs and sanitation. Chemical plants, manufacturing industries, feed mills, food processing, commercial laundries and automotive plants all rely on economizers to conserve valuable energy while optimizing their hot water processes.

Here’s how the Economizer works:

A stack economizer is essentially a water-to-air heat exchanger that uses heat from boiler flue gases to heat water. During boiler operation, water for the hot water process enters the top inlet of the economizer and is sprayed over the heat transfer media. At the same time, boiler flue gas is directed to the flue gas inlet located at the base of the economizer. The water travels from the spray nozzle through the stainless steel transfer media. As the water droplets travel through the media, the hot flue gas rises to the top of the economizer preheating the water. Final heating occurs in the direct contact chamber where a transfer pump or gravity moves the preheated water to a hot water storage system then onto the process as required.

Economizer schematic

Package example:

Boiler:  200 HP = 7,000,000 Btu
Boiler efficiency:  78%
Exhaust Btu:  1,500,000 Btu

Economizer input:  1,500,000 Btu
Economizer efficiency:  80%
Exhaust Btu:  300,000 Btu

QuikWater heater:  3,500,000 Btu
Heater efficiency:  99%
Exhaust Btu:  35,000 Btu

Overall package:
Overall Btu input:  10,500,000
Overall Btu output:  10,237,500
Overall efficiency:  97.5%

Economizer Features

Is a stack economizer right for your application? Contact QuikWater to help you design a fully automated stack economizer system for your operation.