| Contents Notes |
Sulphur dioxide (SO2) emission has become one of the major challenging issues for clean marine transportation globally and especially in zero discharge zones Canada-wide with the implementation of the International Maritime Organization (IMO) regulations. Currently, as per the IMO guidelines, zero-discharge scrubber technology is in use for the ships that operate on low cost high sulfur (3.5% w/w) heavy fuels. One of the main concerns with these scrubber technologies is the non-recyclability of the absorbent and high demand for onsite waste storage which takes a toll on process operating cost and cargo space. Owing to its high capacity, specific selectivity, recyclability, good thermodynamic properties and thermal stability, Ionic Liquids (ILs) can be used as an alternative solvent and need to be tested to get measurable laboratory data. IMO regulations state that SO2 content release should be within 52 ppm as compared to about 1800 ppm of sulfur oxides in typical exhaust flue gas streams. For this, lab scale experiments were performed with a selected group of ILs to understand the absorption-desorption capacity of one such ionic liquids. One IL, named IL-A, was selected for it better performance and was further studied to better understand the reaction mechanism between the IL and SO2. Results were quite promising with good amount of SO2 absorption and partial regenerative desorption of the solvent mixture. Based on the results, it was evident that the viscosity of the IL-A increased tremendously due to SO2 dissolution, which necessitated the use of an additive (additive B) as a diluent. The dilution effect on vapor-liquid-equilibrium (VLE) and other physical properties were experimentally analyzed. TGA and FTIR gave some insights to quantify the amount of solvent loss during the recycling process and to learn about thermal properties and the temperature operating range for the absorption-desorption in order to maximize the efficiency. A mathematical scale-up design model of the absorber to support an actual 20 MW marine vessel combustion engine emitting 61.6 x106 L/hour of flue gas was developed in MATLAB. Theoretical modelling of the process helped in selecting the ideal packing material and to compare the designed tower with traditional scrubber. For the same scrubber diameter, the designed tower height is about 3 meters higher; however, to reduce the footprint to half, an increase of 4.6 meters in height is required. Other advantages include lower operating costs, lower solvent requirement and low storage for solvent and waste generation. |
