Langh Tech says it has conducted several preliminary tests of capturing CO2 emitted by a vessel’s main engine by the means of using an existing Langh Tech closed loop SOx scrubber system. In the tests, additional alkali was added to the scrubber closed loop process water in order to provoke a reaction between the alkali and CO2, effectively capturing the CO2 from the exhaust gas into the process water. The setup of tests was limited by the capacity of the existing alkali pump, but positive results were observed even with only a slight increase in the alkali dosing. At a main engine load of approximately 85%, a 5% increase in alkali dosing (over normal level) was able to reduce the measured CO2 emission by 3,3%. At 40% main engine load, a CO2 emission reduction of nearly 7% was observed.

During the tests, the alkali consumption remained at a reasonable level, and the impact on the operating expenses of the vessel would be acceptable. According to Langh Tech the results of the tests are tentative proof of concept and additional tests with further increased alkali feed will be conducted to verify this. It adds that the CO2 capture feature could be applied to any Langh Tech closed loop or hybrid scrubber systems with relatively low cost impact, with only minor changes to the existing scrubber system. The process could be performed with readily available alkali products such as NaOH and MgOH2, which are both already being used in many SOx scrubber processes.

Langh Tech is also researching methods of extracting the captured CO2 from the process water and looking for ways to store and/or utilize the captured CO2 efficiently both onboard vessels and upon possible discharge to shore.

New CO2 separation membrane
In a development that could be applied in the shipping industry in the longer term, Japan-based NGK Insulators has developed a CO2 separation membrane for industrial exhaust gas. In testing with simulated industrial exhaust gas, the membrane achieved a CO2 separation factor approximately five times that of conventionally developed DDR-type zeolite membrane used for CO2 separation.