Energy & Fuels 2006, 20, 1951-1958
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Study of the Organic Compounds Produced in the Pyrolysis and Combustion of Used Polyester Fabrics Julia Molto´,* Rafael Font, and Juan A. Conesa Chemical Engineering Department, UniVersity of Alicante, P. O. Box 99, 03080 Alicante, Spain ReceiVed May 8, 2006. ReVised Manuscript ReceiVed July 14, 2006
Emissions evolved from the pyrolysis and combustion of used polyester fabrics were studied at different temperatures between 650 and 1050 °C in a laboratory scale reactor, to analyze the influence of both temperature and reaction atmosphere on the final products. More than 160 compounds, including carbon oxides, light hydrocarbons, and polycyclic aromatic hydrocarbons, have been identified and quantified. Benzene is the organic compound evolved with the highest yield. On the other hand, polychlorodibenzodioxins and -furans and dioxinlike polychlorinated biphenyls (PCBs) were also analyzed in the material and in the exit gas produced in the combustion, under fuel-rich conditions, at 850 °C. A total of 3.9 pg WHO-TEQ/g (toxic equivalence established by the World Health Organization), corresponding to a value of 1.1 to the dioxin-like PCBs, was found in the sample, while for the combustion run, a total of 17.9 pg WHO-TEQ/g was obtained, where dioxin-like PCBs only represent a value of 0.4 pg WHO-TEQ/g. The levels of polychlorodibenzo-p-dioxins, polychlorodibenzofurans, and dioxin-like PCBs obtained show that this waste could be used alone or probably with other fuels in incineration plants with energy recovery.
Introduction Natural and synthetic fibers are the two types most commonly found fibers blended and dyed to make textiles. Polyester fibers are the main synthetic fibers used in the industrial manufacturing sector and can be found in several areas of application.1 Polyester fibers are used in apparel for overcoats, jackets, leisure and sportswear, protective clothing, and so forth. In home furnishings, their uses range from drapery and curtain fabrics to furniture coverings, pillows and pillow stuffing, and table and bed linens to wall and floor coverings. Poly(ethylene terephthalate) (PET) is the most widely used thermoplastic polyester. In recent years, the use of this polymer has grown rapidly in packaging, textiles, audio- and videotapes, and other applications. Plastic thermal degradation can take place in noncontrolled conditions, for example, during fires or open-air burning. The substances emitted during noncontrolled plastic thermal degradation may create a serious hazard for human health and for the environment.2 Textiles not reused or recycled are either incinerated with household waste or sent to landfills for final disposal. Although the chemical composition of the textile waste varies, it has a high potential energy content, which makes it suitable for cocombustion processes. In the energy production sector, which is largely reliant on fossil fuels, textile waste can be considered as an alternative energy source. Therefore, waste cocombustion would save the cost of land filling, reduce the impact on the environment, and help fuel diversification. Mueller et al.3 carried out the cocombustion of different textile dusts in a gas firing test plant, analyzing polycyclic aromatic * Author to whom correspondence should be addressed. E-mail:
[email protected]. Phone: +(34) 96 590 38 67. Fax: +(34) 96 590 38 26. (1) Centre of information about textile and clothing industry: Report 2003. http://ww.cityc.es (accessed Dec 2005). (2) Dzie¸ cioł, M.; Trzeszczyn´ski, J. J. Appl. Polym. Sci. 1998, 69, 23772381. (3) Mueller, H.; Pieper, A.; Wichmann, H.; Endres, G.; Tamasi, L. VDIBer. 2003, 1750, 113-120.
hydrocarbons (PAHs), polychlorodibenzodioxins and -furans (PCDD/Fs), and some heavy metals in the initial material, in the ashes formed, and in the flue gas. The cocombustion of propane with pulverized coal, pine shells, and textile wastes was studied by Ye et al.4 Campbell et al.5 examined the recovery of energy by the cocombustion of textile wastes with coal in a circulating fluidized bed boiler. Dzie¸ cioł and Trzeszczyn´ski2,6,7 and Dzie¸ cioł and Baran8 carried out the thermal degradation of PET (granulate for bottle processing) in a tubular furnace under a nitrogen and air atmosphere at 200-700 °C. Around 30 different products were detected; at 700 °C, the main degradation products were carbon dioxide, carbon monoxide, terephthalic acid, benzoic acid, acetaldehyde, aliphatic C1-C4 hydrocarbons, and benzene. Despite this, there are only scarce data in the literature concerning the concentrations of toxic substances emitted in different atmospheres and at different temperatures. Because of this, to improve the knowledge of the thermal degradation (pyrolysis and combustion) of used polyester fabrics, the substances emitted and their concentrations at different temperatures have been studied. Inflammable interior furnishings and decorative materials (particularly textiles) are among the main fire hazards in dwellings. To improve the behavior of fabrics in fire conditions, better flame-retardants are being developed, which improve the thermal resistance of materials, increasing their ignition temperature, reducing the combustion rate, and decreasing the amount of heat released. Despite this, scarce works have been found studying the combustion or pyrolysis of untreated and flame-retardant treated polyester fabrics. (4) Ye, T. H.; Azevedo, J.; Costa, M.; Semiao, V. Combust. Sci. Technol. 2004, 176 (12), 2071-2104. (5) Campbell, P. E.; McMullan, J. T.; Williams, B. C.; Aumann, F. Fuel Process. Technol. 2000, 67, 115-129. (6) Dzie¸ cioł, M.; Trzeszczyn´ski, J. J. Appl. Polym. Sci. 2001, 81, 30643068. (7) Dzie¸ cioł, M.; Trzeszczyn´ski, J. J. Appl. Polym. Sci. 2000, 77, 18941901. (8) Dzie¸ cioł, M.; Baran, J. Chem. Anal. 2001, 46, 669-676.
10.1021/ef060205e CCC: $33.50 © 2006 American Chemical Society Published on Web 08/22/2006
1952 Energy & Fuels, Vol. 20, No. 5, 2006
Molto´ et al.
Table 1. Characteristics of the Material Used C (wt %) H (wt %) N (wt %) O % by difference (wt %) moisture (wt %) ash content (wt %) net calorific value (kJ/kg)
62.6 4.6 0.4 32.4 0.7
