Capture Heat from Exhaust Gases, Save Energy

A new process heat recovery system uses the heated air from process dryers, ovens and air pollution control systems to immediately reduce operating costs by capturing waste heat.

Developed by B&W MEGTEC Systems (De Pere, WI), the unit extracts wasted heat energy and uses it to heat areas of a plant or process. It comes fully assembled, can work with existing or new product lines, and has a compact 4 × 21-ft footprint.

In operation the unit draws a slipstream of heated air from an exhaust duct or stack, passes it through a heat exchanger, then returns it to the exhaust duct or stack. It then draws in fresh outdoor air and passes it through the heat exchanger, where it is heated and controlled to a set point of 70 to 125°F to provide supplemental heating or summer cooling.

According to MEGTEC, the unit can handle source temperatures from 200 to 700°F. Safety features include temperature protection of the delivered air stream and isolation of it from the process and facility anytime the unit is turned off.

It interfaces to existing building climate controls and process heat sources while keeping the processes isolated, and can be fitted with optional inlet air filtration, pressure or humidity control, and carbon monoxide monitoring.

The system delivers either heating or cooling air depending on ambient conditions. It can automatically switch between heating or cooling depending on the temperature setpoint selected. It’s also said to prevent formation of condensation from the regulated air stream to eliminate disposal of collected condensate and the need to comply with any regulatory issues. In fact, MEGTEC says the system can be “tuned” to handle various moisture levels while preventing regulatory issues.

So what’s the potential bottom line? According to MEGTEC, energy cost savings can range from about $3 to $14 per hour. The higher figure is arrived at assuming an input air temperature and flow of 450°F and 5000 scfm, natural gas cost of $1 per therm, average ambient temperature of 32°F, and temperature setpoint for the plant heating air of 125°F. The company is offering an online energy savings calculator (www.megtec.com/heatrecover) that will allow visitors to the site to determine how much energy they could save based on their natural gas costs, exhaust temperature and flow, and average temperature in their area.