EXPERIMENTAL AND NUMERICAL STUDY OF EMISSIONS FROM FUEL-RICH COMBUSTION OF PULVERIZED POLYSTYRENE

摘要

This is an investigation on the formation of products of incomplete combustion (PIC) of waste poly(styrene) (PS). Pulverized PS was steadily injected into an externally-heated drop-tube laboratory furnace and burned therein in fuel-rich conditions, corresponding to a bulk equivalence ratio of approximately 2.5. Iso-kinetic and iso-axial sampling with a probe was performed at five different heights along the centerline of the furnace. The goal has been to investigate the evolution of fixed product gases, unburned light volatile organic compounds (VOC) and semi-volatile organic compounds (SVOC), with emphasis to polycyclic aromatic hydrocarbons (PAH), along the reaction zone of the furnace. The magnitude of species therein and their respective trends were assessed. The centerline gas temperature was measured by suction thermometry. Moreover, the flow field and gas temperature distribution in the furnace were computed with a 3-dimensional model using the CFD code Fluent. Results showed that of the measured light VOC, acetylene exhibited the highest yields in the combustion effluent, followed by methane, ethylene and benzene. These yields were comparable to those of the most prevalent PAH species. PAH profiles varied somewhat in the sampling zone, with yields spanning the range between 13.8 mg (naphthalene) and 0.058 mg (perylene) per each gram of polystyrene burned. The results for fixed exhaust gases showed an increase in CO values with distance traveled, from 85 to 175 mg whereas CO_2 stayed close to 1000 mg, per gram of PS burned. Oxygen remained somewhat steady near 85 mg/g PS burned. Copious amounts of soot were generated and collected through the probe, 0.25-0.42 g for each gram of PS burned. Computations were conducted using a detailed chemical kinetic model, allowing for the prediction of formation and depletion of major PAH and soot particles of different sizes. In this computation styrene was input as the fuel. In comparing experimental hydrocarbon species concentrations to theoretical predictions, a large number of species were found to be within a factor of 7 or less.