Flash-pyrolyzed product distribution of major plastics in a batch reactor

This study is a starting point for the creation of a new plastic recycling process. The process consists of two successive pyrolyzing reactors, for wh ich a spouted bed type seems to be most appropriate for the time being. In the first reactor, plastic chips are fed and instantaneously pyrolyzed into lower hydrocarbons (gas or vapor). In the second reactor, the hydrocarbons are further pyrolyzed into hydrogen and carbon. Hydrogen is a useful and c lean fuel (no carbon dioxide evolution) and a chemical raw material. Carbon can be utilized as carbon black, activated carbon, and so forth. In this s tudy, flash pyrolysis of plastics was investigated to obtain basic data for the first reactor of the process. Six types of plastics, low density polye thylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), polys tyrene (PS), poly(vinyl chloride) (PVC), and poly(ethylene terephthalate) ( PET), were flash-pyrolyzed by putting them into a pre-heated batch reactor (873 K, 5 x 10(-5) m(3)), which was made from stainless steel and contained 5 mm-diameter non-porous alpha -alumina balls as a thermal medium. The pro ducts (gas, condensate and solid residue) were collected and analyzed. In m ost cases, solid residue (in the reactor) yield was less than 3%. Gas yield was 1 to 30%. Condensate yield was 10 to 90%. These results show that in t he first reactor of the proposed process most of the fed plastics can be py rolyzed into gas and vapor, which will move to the second reactor as a flui d.