Removal of marine NOx, SOx, and CO2 from flue gas: Simulation and experiment on a pilot plant

Flue gas treatment typically involves multiple scrubbing and absorbing stages, which increases capital and operating costs and requires large spaces; this process is particularly challenging for space-constrained ships. To address this issue, a highly practical, compact, efficient, intensified marine process for a diesel engine that simultaneously removes NO_x and SO_x to meet the current IMO MARPOL VI 14 regulations for SECAs and IMO MARPOL Annex VI Tier III for NECAs and captures CO₂ before compressing and liquefying it to comply with new IMO regulations. The proposed method uses NO ozonation and wet scrubbing with NaOH in a square marine scrubber, which reduces volume, weight, pressure drop, and associated costs. Mixed solvents, multiple feeds, rich solvent recycling, and heat integration were used to intensify CO₂ removal. Experimental results with a pilot scrubber on marine diesel engine flue gas agreed well with the results of Aspen Plus V12 simulations. Moreover, SO₂ absorption efficiency was > 97.0 %, NO₂ removal efficiency was > 92.2 %, and CO₂ removal efficiency increased from 87.4 % to 94.5 %. The stripper reboiler duty reduced to 176 kW (82.2 % savings) and the total operating costs (TOC) and total annual costs (TAC) reduced by 56.3 % and 13.9 %, respectively, compared with those of the base case.