OCR Text |
Show parts cleaning, organic chemical production (including paints and solvents), and computer chip manufacturing. They are commonly present in low concentrations, meaning large volumes of air must be heated to ensure complete VOC destruction. Because of the high cost of heating such air volumes, primary heat recovery is used to preheat the incoming VOC-Iaden air with recuperative or regenerative methods being the most common. The specific type of VOC thermal oxidizer to be simulated is the regenerative thermal oxidizer (RTO) which is shown schematically in Figure 4. Polluted process air enters the combustion chamber through a heat transfer bed then exits through an identical bed, heating it in the process. The stream direction is then switched every 50 to 120 seconds after the first bed has given up its available heat. Typical chamber temperatures are 1200° to 1600° F, and the destruction efficiency of a standard RTO is approximately 98%. Figure 4. Schematic Regenerative Thermal Oxidizer. The burner provides a point heat source for the combustion chamber. The VOC destruction qualities of the RTO are a function of the RTO design and not primarily of the burner. However, the burner must operate in this environment with low emissions over at least a 10: 1 turndown range, with emissions of NO x being a special concern. Furnace Simulator Modifications The specific aspect of interest in R TO operation from a burner emissions standpoint, besides the high process temperature, is the high oxygen content of the combustion chamber |