The Design And Research On Packed Tower Of Marine Exhaust Gas Scrubbing Desulfurization

Along with the development of shipping industry, the pollution of SOx from marine diesel engine exhaust gas to marine atmosphere environment became more and more serious.Each country and international organizations had formulated very strigent marine SOx emission control regulations. Currently, the emission aftertreatment technology was considered as the most effective method of controlling SOx pollution. Exhaust gas scrubbing desulfurization technology had the best treatment effect among aftertreatment technologies,whose economy was relatively good. Foreign countries had carried out extensive studies on scrubbing desulfurization systems of marine diesel engine, while the researchs of our country were relatively less. Due to the regulation of fuel sulfur content in IMO ECA (emission control area) will be implemented in 2015, therefore, the research on the exhaust gas scrubbing desulfurization system suitable for marine power plant is very important.This paper conducted the research on marine exhaust gas scrubbing scheme. Condidering the limited space and ship stability requirements, wet scrubbing method was selected as the ship exhaust scrubbing technology. Due to the strict requirements to back pressure of marine diesel engine, this paper used packed tower as the absorption device of scrubbing system and NaOH as absorbent. Based on physical and chemical absorption process of SOx, the mass transfer process was studied by double film theory. It uses Aspen Plus to simulate desulfurization absorption process, and the main factors in mass transfer process were ascertained, whose effect on desulfurization efficiency was researched. In order to verify the theoretical results, this paper designed the packed tower scheme, including absorption process,operational condition, absorption and packing. Secondly, it finished the design and calculation of packed tower structure and auxiliary equipments, including the selection and calculation of tower structure size, supporting device of packing, liquid spray device, inlet and outlet device of gas and liquid. Finally, a scrubbing desulfurization test-bed of marine diesel engine was built according to the design result, in order to test the desulfurization efficiency of the scrubbing system. Meanwhile, this paper analyzed the influence of packing types, liquid gas ratio (L/V), pH and temperature of absorbent and inlet gas temperature on desulfurization efficiency. At the same time, considering the practical application of desulfurization device on ships, it needs to deal with several power devices. This paper carried on the exhaust gas scrubbing experiment on a double diesel engine,in order to support the relevant revision of IMO on shared waste gas of power plant.Trough the research,this paper gets the following results: for the selected 6 different packings, the size order of desulfurization efficiency is metal corrugated plate > metal saddle ring > Hanket ball > plastic saddle ring >metal Bauer ring > plastic step ring; when the packing height is in the range of 0～400mm,desulfurization efficiency is proportional to the packing height; when L/V is among 1.9～2.8 L/m3, the desulfurization efficiency increases with the increase of L/V; desulfurization efficiency begins to decrease when L/V is more than 2.8L/m3; desulfurization increases with the increase of pH value, and the increasing trend is obvious in the range of 7-10; when pH is among 10～12, desulfurization efficiency shows little chage; when the absorbent temperature is in the range of 25～65℃,desulfurization efficiency dncreases with the increase of absorbent temperature. desulfurization efficiency increases with the inlet gas temperature of 30～60℃; but desulfurization efficiency decreases sharply in the range of 80～100, the proper inlet gas temperature is in the range of 40-70℃;when gas velocity is in the range of 0.5-2m/s. For twin engine operation, diesel engine exhaust backpressure shows the increasing trend with an average of 0.3kPa; the drop pressure within tower is more 3 times than single engine; diesel engine fuel consumption is slightly larger than single engine, and maximum consumption increased rate is 1.8%; diesel engine torque is slightly lower than single engine.This paper carries out a design and calculation of packed tower of marine diesel engine,and the factors influencing desulfurization efficiency of marine exhaust scrubbing desulfurization system are theoretically analyzed and experimentally researched. These results can provide design reference and theoretical guidance for further designe of ship closed-loop scrubbing desulfurization equipment.