Academic journal article Journal of Environmental Engineering and Science

Polycyclic Aromatic Hydrocarbons Emitted from a Hot-Mix Drum, Asphalt Plant: Study of the Influence from Use of Recycled Bitumen

Academic journal article Journal of Environmental Engineering and Science

Polycyclic Aromatic Hydrocarbons Emitted from a Hot-Mix Drum, Asphalt Plant: Study of the Influence from Use of Recycled Bitumen

Article excerpt

Abstract: Asphalt mixing is an industrial activity of which energy consumption can reach 60% of the total energy consumed by the construction and maintenance of a road over a 30-year service life. Hot mix asphalt plant represents the most common process found in the road sector. Hot bitumen fumes however contain polycyclic aromatic hydrocarbon (PAH) compounds, and, moreover, the use of recycled bitumen can lead to generating various emissions. Polycyclic aromatic hydrocarbons may also be emitted from the process itself, a step that requires warming and drying aggregate through combustion. In the aim of minimizing emissions, it has become necessary to identify the set of major influential parameters. A joint research program involving several institutions has been laid out to conduct an experimental campaign on the Blois Hot Mix Asphalt plant, with quantification of the 16 PAH listed by the USEPA. Variations in asphalt recycling rate favour emissions of heavy molecular weight PAH, among those analysed.

Key words: reclaimed asphalt pavement, airborne emissions, process study.

Resume : La production d'enrobe bitumineux peut contribuer a 60 % de la consommation d'energie totale de la construction et de l'entretien d'une route pendant 30 ans. Le melange a chaud est le procede le plus courant. Cependant, les fumees du bitume chauffe contiennent des HAP, et l'utilisation de bitume recycle est susceptible de modifier les emissions. Les HAP peuvent egalement etre emis par le procede lui-meme qui requiert une combustion afin de secher et chauffer les granulats. Dans une perspective de minimisation des emissions, il devient necessaire d'identifier les parametres les plus influents. Une collaboration a ete montee entre plusieurs instituts, pour mener une campagne de mesures sur le site de la centrale d'enrobage a chaud de Blois, et les 16 HAP de la liste EPA ont ete quantifies. Des variations a la fois de la teneur en eau des granulats et du taux de recyclage d'enrobe, favorise l'emission des HAP a plus forte masse moleculaire, parmi ceux analyses.

Mots-cles : Recyclage d'enrobe bitumineux, emissions atmospheriques, etude procede.

[Traduit par la Redaction]

Introduction

The energy consumed during asphalt can reach 60% of the total energy required for the construction and the maintenance of a road over a 30-year service life (Hoang et al. 2005). Among the various asphalt production processes, hot mix is the most common and consists of warming and drying aggregate before mixing it with hot bitumen.

Hot bitumen (Landa and Wit 1996) and the fumes it releases (Kitto et al. 1997; Bonnet et al. 2000; Burstyn et al. 2001) however contain polycyclic aromatic hydrocarbon (PAH) compounds, which have been gaining increasing attention due to their toxicity (Burstyn et al. 2000; Blomberg et al. 1999; Brandt et al. 2000). Even though a sizable body of literature is available on PAH emitted by bitumen alone, only two studies can be found that focus on the PAH emissions generated during asphalt mix processes. One report on asphalt plants emissions examines PAH emissions factors (USEPA 2004), while another article has been published on PAH emissions from a hot mix asphalt plant (Lee et al. 2004). The context of this targeted process is a batch mix plant, with PAH collected from various point sources and measures sought for the removal efficiency of installed air pollution control devices. Both of these previous studies have proven valuable in providing general emission factors, in association with plant production rates, to achieve regulatory compliance.

Yet, neither study allows distinguishing the influences of process operations materials used. From the standpoint of the industrial decision-maker however, minimizing emissions is initially expressed by means of choosing the appropriate materials and controlling the process. The distinction between PAH issued from combustion reaction and from bitumen is hence one of the big issues of the study of asphalt mix processes. …

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