Optimization of SO2 and NOx sequential wet absorption in a two-stage bioscrubber for elemental sulphur valorisation

Abstract

Flue gases contain SO2 and NOx that can be treated together for elemental sulfur recovery in bioscrubbers, a technology that couples physical-chemical and biological processes for gaseous emissions treatment in a more economic manner than classical absorption. Sequential wet-absorption of SO2 and NOx from flue gas is thoroughly studied in this work in a two-stage bioscrubber towards elemental sulphur valorisation pursuing reuse of biological process effluents as absorbents. The optimal operating conditions required for SO2 and NOx absorption in two consecutive spray-absorbers were defined using NaOH-based absorbents. Overall, removal efficiencies of 98.9 and 55.9% for SO2 and NOx abatement were obtained in two in-series scrubbers operated under a gas contact time of 1 and 100 s, and a liquid-to-gas ratio of 7.5 and 15 L•m -3 , respectively. Higher NOx removal efficiency to clean gas emission was obtained by oxidants dosing in the absorber for NOx absorption. High NaHCO3 concentration in two-stage bioscrubber effluent was exploited as alkaline absorbent for flue gas treatment. The performance of scrubbers using an absorbent mimicking a reused effluent exhibited same removal efficiencies than those observed using NaOH solutions. In addition, the reuse of bioprocess effluent reduced reagents consumption by a 63.7%. Thus, the two-stage bioscrubber proposed herein offers an environmentally friendly and economic alternative for flue gas treatment.

Mass transfer vectors for nitric oxide removal through biological treatments

“…This is basically because NO is an acid gas, whereas the pH remained at 8 when phosphate solution was used due to its buffer potential effect. This is consistent with what was observed by Guimerà et al ( 2021 ), where no gas-to-liquid mass transfer was observed when a phosphate buffer was added in a system without NAP. However, the system was kept at a neutral pH.…”

“…According to supplementary information Figure S 2 , the results confirmed that as soluble gases (NO 2 ) were formed in the gas phase, they were transferred to the liquid phase through different instantaneous and irreversible reactions with water or phosphate buffer to form nitrous and nitric acids as described by Guimerà et al ( 2021 ). The results of the mass transfer in the three-phase system (Figure S 2 ) showed a higher concentration of and in the aqueous phase when MTV was present compared to NAP-free blanks.…”

Recent Advances in Biotechnologies for the Treatment of Environmental Pollutants Based on Reactive Sulfur Species

“…Efforts have focused on the development of qualified technologies to eliminate SO 2 from coal-combustion flue gas. Flue-gas exhaust contains some CO, nitrogen oxides (NO X ), and small amounts of O 2 in addition to SO 2 [ 24 ]. Developing technologies for integrated methods of treating multiple greenhouse gases remains a global priority.…”