The effect of the bulk equivalence ratio on the pah emissions from the combustion of PVC, poly(styrene), and poly(ethylene)

Abstract

This is an investigation on the effects of the bulk equivalence ratio on the polynuclear aromatic hydrocarbon (PAH) emissions from the combustion of poly(vinyl-chloride) (PVC), poly(ethylene) (PE), and poly(styrene) (PS) particles. Steady-flow dispersions (clouds) of the above types of polymer particles, 150–212 μm in diameter, were burned in a drop-tube, electrically heated furnance at different bulk equivalence ratios ( ϕ bulk =0.1–7.3) or were pyrolyzed in N 2 . The gas temperature and residence time in the furnance were 1100°C and 1 s, respectively. (a) The total (specific) amounts of condensed and gaseous-phase PAH emissions increased with the equivalence ratio. In the present experiments, the recorded maxima in the total amounts of PAHs were obtained under pyrolysis in N 2 and accounted for 0.7, 4, and 4% of the input masses of PVC, PE, and PS, respectively. (b) PVC particles were found to oxidize effectively in air, since only minimal amounts of PAHs were produced at ϕ bulk <-1. Chlorinated organies were found at high ϕ bulk . or in N 2 . Combustion of PE and PS particles produced substantial amounts of PAHs at, or near, stoichiometric conditions. PE particles were prone to flash pyrolysis and readily formed group flames (“puffs”), even at mildly fuel-rich or near-stoichiometric conditions. (c) PAH emissions from pyrolysis of PE and PS were sensitive to the particle mass loading (mass of polymer per mass of N 2 ) in the furnance. This was not the case for PVC. (d) For all polymers, the percentage of naphthalene in the total amount of PAHs was influenced by the combustion conditions and experienced a minimum close to stoichiometry. (e) Finally, the experimentally measured molar fractions of pairs of selected PAH isomers were compared with those obtained from chemical equilibrium calculations. For all polymers, the pairs fluoranthene (F)—acephenanthrylene (AP) and cyclopenta[cd]pyrene (CP[ed]P)-benzo[ghi]fluoranthene (B[ghi]F) were at equilibrium, while the pairs fluoranthene (F)—pyrene (P) and benzo[k]fluoranthene (B[k]F)—benzo[a]pyrene (B[a]P) were not at equilibrium. PS produced much higher soot emissions than PE or PVC.