Research About Purification Technology And Equipment Of Ship Emissions

Sulfur oxides of marine diesel engine emissions have become the important source of air pollution. International convention MARPOL73/78 put forwardstrictrequirementsonsulfuroxide emissions. In order to effectively deal with the increasingly stringent marine fuel oil sulfur content and the emission limitations of SO2, we must strengthen the research on sulfur emissions control of the ship.In this paper, a variety of technology are compared, think that seawater desulphurization has the superiority in ship exhaust emission control, because the desulfurizing agent (seawater) can obtain raw material locally. Based on the analysis of SO2 desulfurization mechanism, this paper designs a set of dual-mode flue gas desulfurization system, which takes the seawater or freshwater and alkaline substances as desulfurizing agent, can adapt to different area emissions requirements. Regulation of pH after the first aeration process can reduce the number of equipment, area covered and investment cost. In this paper, we use a venturi tube as the first washing device of desulfurization tower, can get a better cooling, initial washing and dedusting effect, simplify the process, and improve system reliability.The desulfurization tower is the core equipment of seawater desulphurization device, flue gas inlet adopts venturi tube, spiral nozzle as the atomizing nozzle, and use the orifice-plates to optimize the internal flow field. The numerical simulation of gas-liquid two-phase flow in the spray tower found that the installation of two layer orifice-plates is beneficial to the uniform distribution of flow field, reducing the overall rate of flow field. The gas phase flow direction changes under the drag action of spray, turbulence and vortex forms near the nozzle, therefore, reasonable arrangement of orifice-plates and increasing the number of nozzles can improve the efficiency of desulfurization.Using diesel engine exhaust to simulate the ship exhaust gas, the desulfurization effect of the device and the factors affecting desulfurization efficiency are studied by experiments in this paper. We found that the reasonable arrangement of two layer orifice-plates may play a role in optimizing the flow field distribution, and the desulfurization efficiency is improved by about 40%. In the total flow of 4 L-min"1,52% SO2 can be removed at the venturi preliminary washing zone, achieve cooling and dedusting, preliminary washing and shorten the height of the main tower. Alkalinity, pH and temperature of seawater have a greater influence on the desulfurization efficiency, and the effects of salinity less. With the increase of alkalinity of seawater, pH value, the desulfurization efficiency is obviously improved. The SO2 content in the flue gas was negative correlation with the desulfurization efficiency. When the entrance concentration of SO2 increased to 3040 mg·m-3, liquid-gas ratio must reach 15 L·m’that can obtain more than 97.04% desulfurization efficiency, that is to say it reaches the limit value of fuel sulfur content less than 0.1%.With the increase of liquid-gas ratio, the desulfurization efficiency will increase. However, the liquid-gas ratio increased to 7.5 L·m-3 above, the desulfurization efficiency growth became slow. Properly increasing the liquid-gas ratio is an effective way to improve desulfurization efficiency, and liquid-gas ratio above 7.5 L·m-3 can guarantee good desulfurization efficiency.