Thermodynamic evaluation of flare gas recovery in the Zagros Petrochemical Complex for integration into the methanol production cycle

Research subject: The flare, as an integral part of petrochemical plants, not only ensures the safety of operations and personnel but is also a major source of pollutant emissions and volatile organic compounds. The gases directed to the flare often contain valuable components whose recovery can significantly enhance production, increase revenues, and reduce greenhouse gas emissions. Therefore, investigating the recovery of flare gases and their reuse in petrochemical processes is of considerable importance.
Research approach: In this study, aimed at recovering flare gases in the Zagros Petrochemical Complex, process simulation and energy–exergy analyses were performed. The proposed process consisted of a methane steam reformer operating at 1000 K and 101.3 kPa, a system of heat exchangers, a water–condensate separator, and a gas compression unit increasing the recovered gas pressure to 7600 kPa in accordance with the methanol synthesis reactor conditions. Furthermore, a sensitivity analysis was conducted to examine the effect of steam-to-carbon ratio and reformer feed temperature on the overall energy and exergy performance of the system.
Main results: The results indicated that the optimum steam-to-carbon ratio in the reformer was 13, at which all methane was converted into syngas. Increasing the feed temperature reduced reformer energy consumption, enhanced energy efficiency, and decreased exergy destruction. Exergy analysis showed that the reformer accounted for the highest share of exergy destruction (49.43%), while the water separator contributed none. The overall energy efficiency of the process was calculated as 56.43%, with 17 GJ of input energy utilized. The specific energy loss and exergy destruction per ton of recovered gas were 13.13 GJ and 2.62 GJ, respectively. Methanol synthesis unit simulation revealed that syngas recovery increased methanol production by 9.16%, equivalent to 462.39 tons per day. Finally, the evaluation confirmed that implementing flare gas recovery completely eliminated CO2 emissions from flaring, thereby reducing the CO2 footprint from this source to zero.