Aim of the current research project is the development of a dry exhaust gas cleaning process for desulphurization of exhaust gases from marine diesel engines using heavy fuel oil. To be applied is a two-stage bed absorber with pellets of hydrated lime for absorption of sulphur oxides. 

The principle of desulphurization is based on the reaction of hydrated lime ((CaOH)₂) with SO₂ and SO₃ forming gypsum. The spherical dry lime granular with diameters between 3 and 8 mm is flowing slowly in a packed bed and is circulated around by the exhaust gas.

The prototype of this “Dry Exhaust Gas Cleaning System” (DryEGCS) has been installed in 2009 on the cargo vessel M/V “Timbus”. This research plant is used for evaluation of the process and further development. The flow chart is illustrating the schematics of the absorber in combination with an SCR-catalyst for removal of nitrogen oxides. The SCR-catalyst can be integrated since the exhaust gas temperature stays on a constant level.

An exhaust gas ventilator is used to overcome the pressure loss in the packed bed of about 7 mbar. In later designs, the ventilator may not be necessary.

The absorber has been dimensioned to reduce the sulphur oxides concentration in the exhaust gas from a level of 1% sulphur in the fuel oil to an equivalent sulphur level in fuel of only 0.1%.  Therefore it is possible, to be below the IMO limit of 0.1% sulphur in ECAs beginning 2015.

In the first stage particulate matter is removed from the exhaust gas on used granular. In the upper second stage fresh granular is utilized to absorb the sulphur oxides. 

In first results it has been be shown, that the DryEGCS is able to remove sulphur oxides to an equivalent level of 0.1% sulphur in fuel oil reliably, also for higher sulphur contents in the fuel oil. By further examination and development, the aim is to gain the certificate of a classification society to be able to bunker fuel oils containing high sulphur, but to maintain IMOs limit values.