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Using Water-Plate Collector and Water Spray on ESP to Reduce Marine Diesel Exhaust Emission
I Made Ariana, Hirotsugu Fujita, Osami Nishida and Wataru Harano

Electrostatic Precipitator (ESP),one of the methods to reduce particulate matter, can decrease particulate concentration in the marine diesel exhaust gas. Unburned hydrocarbon of particulate matter that is collected on the plate and electrode of ESP is difficult to remove using rapping method. The particulate disturbs electric strength and decreases performance of ESP for long time operation. Two methods, water-plate collector and water spray, are proposed to clean up the collector plate, keep ESP performance, and reduce gaseous emission, NOx and SOx, in the exhaust gas. In the first method, water or a combination of water and plate is used to substitute for the collector plate of the ESP. The water and water vapor of exhaust gas in the high voltage electric region generates gas-phase radicals, O and OH, by electron impact excitation and ionization. The gas-phase radicals oxidize NOx and SOx to HNO2, HNO3, and H2SO4. In the other method, water is periodically sprayed on the electrode and collector plate to remove the particulates from ESP. Effects of fresh water and seawater for collector of ESP on collection efficiency and electric power consumption are also analyzed.

The results show that intermittent spray of water in ESP keeps the ESP performance, and water-plate collector improves ESP performance to reduce PM, NO, and SO2 in the marine diesel engine. Seawater used for the water-plate collector has efficiency of SO2 reduction higher than fresh water.

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