The Energy Efficiency and Renewable Energy office of the U.S. Department of Energy (DOE) highlighted the benefits of waste heat recovery systems in the Process Heating Tip Sheet #8. Through the Industrial Technologies Program, the DOE strives to help some of the country’s largest energy consumers improve energy efficiency. The September 2005 installment of the Process Heating Tip Sheet defines how the spent combustion gases from fuel-fired heating equipment that still holds considerable thermal energy can be captured via a heat recovery system. The result is energy savings.
According to the Tip Sheet, the following are benefits to waste heat recovery:
- Improved heating-system efficiency. Energy consumption can typically be reduced by 5 to 30 percent.
- Lower flue gas temperature in chimney. Less heat is wasted.
- Higher flame temperatures. Combustion air-preheating heats furnaces better and faster.
- Faster furnace start-up. Combustion air-preheating heats furnaces faster.
- Increased productivity. Waste heat used or load preheating can increase throughput.
The Tip Sheet also identifies and explains the three most common heat recovery methods: preheating combustion air, steam generation and water heating, and load preheating.
The DOE recommends that heat recovery systems be considered if the exhaust temperature is greater than 1,000 degrees F. or if the flue gas mass flow is very large.
To review the Process Heating Tip Sheet #8 in its entirety, visit (www.nrel.gov/docs/fy05osti/38625.pdf).