AROMATIC HYDROCARBON EMISSIONS FROM BURNING POLY(STYRENE), POLY(ETHYLENE) AND PVC PARTICLES AT HIGH-TEMPERATURES

A study on the semi-volatile aromatic hydrocarbon emissions from the p yrolysis/combustion of poly(styrene) (PS), poly(ethylene) (PE) and PVC particles was conducted. Dispersions (aerosols) or batches (fixed bed s) of the above types of polymer particles, 90-300 mu m in diameter, w ere burned in bench-scale, drop-tube or muffle-type electrically-heate d furnaces, respectively. In the drop-tube furnace, pyrolysis/combusti on took place at gas temperatures ranging from 900 to 1200 degrees C a nd particle heating rates were in the order of 10(3) - 10(4) degrees C /s. The total residence times of the gases in the furnaces were 1 or 2 s; envelope flames surrounding the particles lasted for 6-130 ms, whi le residence times in the post-flame region were 0.3-1.8 s depending o n the polymer. Semi-volatile organic emissions were captured from the gas and solid phases using XAD-4 adsorbers and glass fiber filters, re spectively, and analysis was conducted with gas chromatography coupled with mass spectrometry (GC-MS). The combustion characteristics of sin gle particles of the three plastics were studied in earlier experiment s using optical pyrometry and high-speed cinematography. Gaseous diffu sion, chemical kinetics and pyrolysis kinetics were inferred, therein, to govern combustion of PS, PVC and PE particles, respectively. The t ypes of the aromatic hydrocarbon emissions were found to depend on the polymer burned, while their relative amounts were influenced by combu stion parameters such as temperature, residence time, etc. Substituted poly-aromatic hydrocarbons (PAHs), oxygenated compounds and chlorinat ed aromatics were detected in the combustion products of PVC. PAHs wit h fused rings were emitted from the combustion of PE. PAHs, either sub stituted or with fused rings were emitted from the combustion of PS. A s the gas temperatures and residence times increased, the amount of PA H emissions from all polymers decreased. The results indicated that as the size of PVC sample decreased, in the presence of oxygen, the amou nt of PAHs decreased. However, as the size of PE sample decreased, or when oxygen was present, the amount of PAHs did not necessarily decrea se. The behavior of PS was found to be between that of PVC and PS.