| 摘要 |
A method and apparatus are provided for reducing the VOC, CO, and, alternatively, the NOx content of dryer offgas that is discharged into the atmosphere from a moist organic product drying process using thermal oxidizing apparatus that includes a burner, furnace, mixing chamber, thermal oxidizer, tempering chamber, and an indirect gas-to-gas heat exchanger. The dryer offgas is separated into two portions, with a larger portion being preheated by indirect heat exchange with the hot gaseous output from the thermal oxidizer. The non-preheated portion is directed to the burner in the function of flue gas recycle for NOx control. The preheated portion is separated into two portions, with one portion being directed to the furnace/mixing chamber of the thermal oxidizing apparatus. The other portion of the preheated offgas is recycled to the hot gas inlet of the dryer and serves the function of dryer heat transfer media. Ultimately, all the dryer offgas enters the thermal oxidizer, and comprises a smaller non-preheated portion directed to the burner and a larger preheated portion directed to the furnace/mixing chamber. By preheating a large proportion of the offgas directed to the thermal oxidizing apparatus, simultaneous achievement of an adequate thermal oxidizer temperature, 1600° F., and an adequate oxygen concentration of 5% by volume is achieved for optimized thermal oxidation of carbon monoxide and volatile organic compounds.
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