Estimation of benzene concentration and flux from a flare stack using differential absorption LiDAR

Abstract In this study, a Differential Absorption Lidar (DIAL) system was employed to remotely quantify the concentration distribution and flux of benzene released from a flare stack. The measurements were conducted on May 2, 2024, at Plant B located within the A petrochemical industrial complex in Korea, and a total of six repeated measurements were performed for a single flare stack. The on-resonant wavelength $$\:\left({\lambda\:}_{on}\right)$$ was determined as 252.1998 nm through a cell scan procedure. A cross-wind measurement geometry was applied to obtain transverse concentration distributions at a distance of approximately 400–430 m from the DIAL. The scan was conducted over 11 lines (line 1–11) ranging from 14.9° to 15.9°. Each line was measured for 50 s at a repetition rate of 10 Hz, yielding 500 shots per line and a total scan duration of 550 s per measurement. The maximum observed benzene concentrations were 2.62, 3.17, 3.11, 2.65, 3.13, and 2.23 ppm for each case. By combining the concentration data with flare stack height wind speeds estimated using a logarithmic wind profile, the corresponding benzene flux was calculated as 7.13, 6.18, 7.61, 8.11, 10.33, and 10.17 kg·hr⁻¹, respectively. The results indicate that wind speed variations significantly influence flux estimation. This study represents the first reported application of a remote DIAL system to quantitatively determine benzene flux from an industrial flare stack in Korea.