An Interesting Waste Heat Application

At Cire Technologies we are very cognizant of our customers’ cost of operating our equipment. One area we excel at is reusing waste heat from our equipment back into the process. A current project illustrates an innovative use of waste heat that will pay for itself in less than one year and provide benefits to the bottom line of the customer for years to come.

Our customer has two solvent based pressure sensitive adhesive coating lines that currently exhaust to a recuperative thermal oxidizer that needs to be replaced. It was the customer’s desire to replace the single oxidizer with two oxidizers, one for each coating line, to provide operating flexibility and redundancy. The system design allows the oxidizers to be used interchangeably to add to the system flexibility.

The coating lines process a wide range of products with a corresponding wide range of solvent loads, from high to low. In order to minimize the natural gas required by the oxidizers we selected a regenerative thermal oxidizer with a hot side heat exchanger bypass. This matches the oxidizer heat exchanger efficiency to the wide range of solvent loads, such that the unit is self-sustaining for most products produced.

Since most products produced have high solvent load coatings, there is a substantial quantity of waste heat dumped through the hot side heat exchanger bypass. Our recommendation was to find a use for this high quality (temperature) waste heat. Since the best use of waste heat is back in the process, we recommended replacing the dryer heat source, natural gas burners, with direct feedback of high temperature make-up air to the dryer. These feedback systems will supply all of the heat energy required to heat the drying air of each dryer.

The system includes a duct from the heat exchanger bypass duct to a set of mixing dampers that mix 1500°F cleaned air from the oxidizer combustion chamber with ambient air from the outside. This provides the desired make-up air temperature required by the dryer. In addition the air is filtered to HEPA level to ensure product quality.

For each temperature zone of the dryers new mixing dampers are supplied to mix the heated make-up air with tempering air from the coating head enclosure to achieve the final dryer temperature desired for the associated zone.

Cire Technologies is responsible for the complete turnkey project including the two oxidizers, modifications to the process dryers and exhaust systems, make-up air ductwork and fans. A control system that oversees and operates the entire installation sets fan speeds, damper positions and temperature set points automatically through a recipe system programmed for each of the customer’s products.

Cire Technologies is proud of our attention to energy efficiency, perhaps you have a waste heat source you would like to explore uses for? We would love to hear from you.