Slow pyrolysis of different PVC types in a bubbling fluidized bed: Stabilizer effects

The effect of stabilizers on thermal degradation of poly(vinyl chloride) (PVC) in a bubbling fluidized bed (BFB) was studied as part of a process assessment for high-PVC waste treatment. The BFB reactor operated at temperatures between 200 and 400°C and three types of PVC were used in the tests: a pure rigid bottle-grade containing some tin compounds stabilizer, an old, light grey sewage PVC pipe with lead compound stabilizer and a newer orange sewage PVC pipe with Ca/Zn compounds stabilizer. The pyrolysis gases from the BFB were analyzed with a Fourier transform infrared (FT-IR) spectrometer. The result from the tests and char analysis showed that the weight fraction and the type of stabilizer, especially lead compound, have a major effect by slowing PVC degradation especially at the first degradation stage compared to a purer PVC which contains only a small amount of tin based stabilizer. The results also showed that a temperature range 340-350°C, where most of the chlorine for all types used in the tests was released, is optimal for operating the BFB pyrolysis reactor.