Every industrial heating process produces waste heat. It’s unavoidable. The question is not whether it exists, but whether any of it can be put back to work.
Waste heat management covers three distinct activities: waste heat reduction, waste heat recycling, and waste heat recovery. Understanding the difference between these three is important for setting realistic expectations about what’s achievable.
The Three Categories
Waste heat reduction means reducing the generation of waste heat in the first place — through better insulation, tighter seals, lower exhaust temperatures, and reduced air infiltration. This is the category that overlaps directly with heat containment, and it’s generally the first step before pursuing recovery.
Waste heat recycling means using waste heat within the same system it came from. The most common example the sourcebook gives is preheating combustion air using heat recovered from the exhaust gases of the same burner. The sourcebook notes that this type of heat recycling can reduce energy use or energy intensity by as much as 25%.
Waste heat recovery means capturing waste heat from one process and using it in a different system — for example, using hot flue gases from a high-temperature process to generate steam or heat water for a lower-temperature process elsewhere in the facility. Payback periods typically ranging from one-half year to five years, with heat recovery of 10% to 75% of the available waste heat depending on the technology.
Where Waste Heat Comes From
The sourcebook provides a useful table of industrial waste heat sources and their temperature ranges. Furnace or heating system exhaust gases run between 600°F and 2,000°F. Gas turbine exhaust runs 900°F to 1,100°F. Hot surfaces — including uninsulated pipe and equipment surfaces — run between 150°F and 600°F. Even steam leaks and condensate return systems represent waste heat streams worth evaluating.
The Right Order of Operations
The sourcebook is explicit about the sequence: reduce waste heat first, then recycle it within the same system, then consider recovery to other systems. This matters because the economics of a heat recovery project depend on how much waste heat is actually available. Improving insulation and reducing air infiltration first may reduce the magnitude of the recovery opportunity — but it also reduces what the system has to generate in the first place, which is the better outcome.
Reducing hot surface losses through insulation is the first step in any waste heat management program. UniTherm’s removable insulation jackets, blankets, and covers help address heat loss from equipment surfaces, piping, and exhaust components — the foundational step before more complex recovery technologies are evaluated.
For our standard removable insulation solutions, visit shop.unitherm.com.
To request a quote for a custom insulation solutions click here.
Source: U.S. DOE, Improving Process Heating System Performance: A Sourcebook for Industry (Third Edition), 2015.
Companies always look to make the best decisions when selecting capital projects to work into the budget; simple metrics like Return on Investment and Internal Rate of Return tend to dictate how the budget for these projects is written each year. In an effort to increase the bottom line, investments are often times funneled toward projects and purchases that directly affect sales rather than decreasing operating costs, but sales growth is never guaranteed.