Issue 2, 2024

Analysis of nitro- and oxy-PAH emissions from a pilot scale silicon process with flue gas recirculation

Abstract

Silicon alloys are produced by carbothermic reduction of quartz in a submerged arc furnace. This high-temperature pyrolytic process is a source of polycyclic aromatic hydrocarbons (PAHs), which are a group of aromatic organic molecules with known mutagenic and carcinogenic properties. In this study, the emission of oxy- and nitro-PAHs from a pilot-scale Si furnace, with varying process conditions such as oxygen level, flue gas recirculation (FGR), and off-gas flow, was investigated. Analysis shows the presence of both oxy- and nitro-PAH species in all experiments, believed to be formed from radical-induced substitution reactions initiated by SiO combustion and NOx formation. During Si production without FGR, the levels of oxy- and nitro-PAHs range between 1.1 and 4.4 μg Nm−3, independent of the flue gas flow rate. With increasing FGR (0–82.5%) and decreasing oxygen level (20.7–13.3%), the concentrations of both oxy- and nitro-PAHs increase to 36.6 and 65.9 μg Nm−3, respectively. When the levels of substituted PAHs increase, species such as 4-nitropyrene and 1,2-benzanthraquinone are in abundance compared to their parent PAHs. Experiments at lower flue gas flow (500 Nm3 h−1versus 1000 Nm3 h−1) generally produce less substituted PAHs, as well as SiO2 particulate matter and NOx, where the latter two parameters have a 99% correlation in this study.

Graphical abstract: Analysis of nitro- and oxy-PAH emissions from a pilot scale silicon process with flue gas recirculation

Supplementary files

Article information

Article type
Paper
Submitted
12 Jul 2023
Accepted
23 Nov 2023
First published
18 Dec 2023
This article is Open Access
Creative Commons BY license

Environ. Sci.: Adv., 2024,3, 239-248

Analysis of nitro- and oxy-PAH emissions from a pilot scale silicon process with flue gas recirculation

K. Arnesen, V. Andersen, K. Jakovljevic, E. K. Enge, H. Gaertner, T. A. Aarhaug, K. E. Einarsrud and G. Tranell, Environ. Sci.: Adv., 2024, 3, 239 DOI: 10.1039/D3VA00187C

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