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针对现有船舶废气洗涤装置共存的开式系统海水脱硫效果不佳、闭式系统碱液消耗量大的问题提出了梯级洗涤技术,并在试验系统上测试了海水/海水梯级洗涤和海水/碱液梯级洗涤两种模式下的废气脱硫效果.结果表明:海水/海水梯级洗涤脱硫效率与海水碱度密切相关,采用高碱度海水脱硫时梯级洗涤法可以满足硫排放控制要求,但海水碱度低时则无法满足要求;海水/碱液梯级洗涤效果优于海水/海水梯级洗涤.当主洗涤段采用碱度为810 μmol/L、液气比为5 L/m3的海水洗涤SO2浓度为2 000 mg/m3的废气时,副洗涤段使用pH值为12.2的碱液且液气比为l L/m3即可达到97.2％以上的脱硫效率,且碱液的pH值越高,洗涤效果越好.综合脱硫需求、泵耗和防腐需求,建议碱液pH值宜选11 ～13.,Aiming at solving the deficiencies of the existing two desulfurization solutions (i.e.,the insufficient seawater desulfurization efficiency in Sulphur Emission Control Area (ECA) for the open-loop solution and the large fresh water/sodium hydroxide consumption for the closed-loop solution),a cascadescrubbing desulfurization technology coupled with seawater and alkaline liquor was proposed in this paper.Accordingly,a bench-scale cascade-scrubbing desulfurization system was established to perform desulfurization experiments respectively under operational models of cascaded seawater and cascaded seawater/alkaline,so as to confirm its desulfurization performance for the marine exhaust gas.Results showed that high desulfurization efficiency can be gained by the proposed seawater cascade-scrubbing solution and the desulfurization efficiency strongly depends on the seawater alkalinity.In the seawater cascade-scrubbing solution,only the circumstances with high-alkalinity seawater can meet the ECA’s requirements.Again,the seawater/lye cascade-scrubbing model is superior to the sole seawater cascade-scrubbing model in the desulfurization performance.Under the seawater/lye cascade-scrubbing conditions where the parameters in main scrubbing section are seawater alkalinity 810 μmol/L,liquid/gas ratio 5 L/m3,and inlet SO2 concentration 2 000 mg/m3,the subordinate scrubbing section (using a lye with the pH value of 12.2) reaches a sufficiently high desulfurization efficiency above 97.2％,with an extremely low liquid/gas ratio less than 1 L/m3.The higher the pH of the lye,the better the desulfurization performance.In view of an excessively high concentration lye deepening corrosion,sufficient desulfurization efficiency plus a low liquid/gas ratio for low cost necessitates the lye pH levels in the subordinate scrubbing section to be setat 11-13.