Wet scrubbers: Open-loop, closed-loop, or hybrid?

摘要

Open-loop scrubbers function by pumping seawater into the system where exhaust gas is sprayed at different stages. The natural salinity of the seawater induces a chemical reaction with the SO_x in the exhaust gas, forming sulphuric acid (H_2SO_4) as a by-product. After the process is complete, the washwater is filtered using centrifugal forces to separate suspended matter and is diluted for pH adjustment before being discharged overboard. Suspended matter is drained away as sludge and stored in a tank. The main benefit of open-loop scrubbers is their simplicity and lack of reliance on additional chemicals to ensure their efficacy. Closed-loop scrubbers use freshwater or seawater that is treated with an alkaline chemical in a 'closed' circuitfor neutralisation and scrubbing. By virtue of their chemical dosing, closed-loop scrubbers can artificially control the alkalinity of the scrubbing liquid. In this type of system, the washwater is recirculated and losses are made up with additional freshwater.