The Process

Our furnaces clean by the process of pyrolysis - the chemical breakdown of materials by the action of heat – not fire. Pollution Control’s patented process positively controls the charring of materials and the rate of smoke emission and other volatiles inside the furnace. Close control of excess temperature with water injection eliminates any damage to parts. Organic materials on parts are vaporized into smoke. Afterburners incinerate the smoke, leaving only odorless and harmless water vapor and carbon dioxide to exit out the exhaust stack.  

HOW BURN-OFF OVENS WORK

Burn-Off Ovens are a specialized type of process equipment specifically designed to remove organic material from metal parts. These ovens operate at temperatures of 600 to 900ºF (315 to 482ºC) inside the primary cleaning chamber. The load placed in the oven usually consists of metal parts coated with small amounts of cured paint, cured polymer, cured varnish, grease, oil or other organic material. There are no open flames inside the primary cleaning chamber of a burn-off oven, and the amount of metal loaded into the oven usually accounts for 80 to 97% by weight of the total load. Only small amounts of cured organic coatings are on the metal parts to be cleaned, with coatings typically averaging 3 to 20% of the total load.

The primary heat input burner fires into a combustion chamber, which contains the flame so that only heat is discharged into the work area containing the parts.  No flame actually contacts the parts.  Other than the air required for combustion of the input burner fuel, no additional air is added to the oven.  Therefore, the oxygen content within the oven is reduced to a level, which prevents the material from catching on fire. The heat causes the material to decompose into smoke and pyrolysis gases. These gases are then drawn through an afterburner to burn and completely eliminate any harmful emissions from being discharged out the exhaust stack.

Controlled Pyrolysis® burn-off ovens control the processing rate of the organic material at a constant maximum rate, regardless of the physical size of the oven.

The cleaning process for most materials is a two stage process. During the initial stage (pyrolysis stage), the cured paint, or other organic material breaks down into smoke, which is burned in the afterburner.  During this stage of the process, the processing rate is limited by the size of the afterburner.

The smoke burning capacity (pound per hour processing rate) of the afterburner is determined by several factors, including the idle temperature of the afterburner, the set point temperature of the afterburner, and the amount of heat generated by the smoke as it is burned in the afterburner chamber.  With the idle temperature and set point of the afterburner fixed, the only variable is the amount of heat generated per pound of smoke burned. The amount of heat generated by the smoke as it burns varies based on the material being removed.  Thus, the pound per hour smoke burning capacity of the afterburner varies somewhat from material to material.

Most powder coatings contain anywhere from 10 to 70% inorganic material by weight.  This inorganic material will not burn and therefore drops onto the floor of the oven as an ash.  As a result, actual material removal rates will normally be higher than the smoke-processing rate.

Once most of the organic material has been vaporized into smoke, there is generally a char or carbon residue left behind on the parts.  The actual amount of char formed is dependent on the nature of the material being removed.  Some materials produce virtually no char, while others produce large amounts.  This char can be removed only by the surface oxidation of the carbon ultimately to carbon dioxide.  This second stage (oxidation stage) requires keeping the parts hot while allowing some amount of air to enter the oven in order to oxidize the carbon and remove it from the parts. The rate of carbon oxidation is surface limited and is not affected by the size of the afterburner.

Burn-off ovens are used to remove paints, plastics, oils, and other organic materials from primarily metal components, using a process known as pyrolysis - a decomposition brought about by the action of heat.  The materials are pyrolyzed into smoke and the smoke is burned in an integrated afterburner chamber to convert it to harmless CO^₂ and water vapor before being exhausted to the atmosphere.

The amount of material that can be processed in a given time depends on the composition of the material being removed and the smoke burning capacity of the afterburner.  Using pyrolysis to clean materials for re-use eliminates manual or chemical cleaning processes, which can be dangerous to workers and the environment. Controlled Pyrolysis® is an economical way to accomplish cleaning requirements in today's environment.