Comparative Analysis Of SO_x Emission Control Technology On Board

With the vigorous international trade in recent decades,the shipping industry has made tremendous development,and various large-tonnage diesel ships have also been constantly increasing.Today,marine exhaust gas has become one of the main causes of air pollution,causing continuous concern in the international arena.Organizations such as the developed countries in Europe and the United States and the International Maritime Organization(IMO)have been conducting further discussions on issues such as the quality of marine fuel oil and the design of new ships in order to find out the policies that can reduce the pollution of ships’ exhaust gas to the atmosphere.Among them,developed countries in Europe and North America jointly put forward the establishment of a marine emission control area(ECA),while the International Maritime Organization(IMO)has formulated the MARPOL Annex Ⅵ and came into force in 2005.How to economically and effectively reduce the emission of SOx from ships to meet the relevant regulatory requirements is a hot topic at home and abroad.This article begins with a description of the causes of SOx emissions from ships,the potential hazards and the current status of emissions at home and abroad.Afterwards,the author summarizes the relevant provisions on the marine fuel oil sulfur content of marine emission control area(ECA)in developed countries in Europe and North America and MARPOL Annex VI of the International Maritime Organization(IMO)and draws lessons from its advantages to put forward some measures to prevent and control air pollution in China’s shipping industry.Then,six common desulphurization measures to reduce the SOx content in the ship’s exhaust gas are listed.These include the use of low-sulfur fuels,the use of alternative fuels(LNG),dry desulfurization,open seawater wet desulphurization,closed freshwater wet desulphurization and hybrid wet desulfurization,and details of its working principle and characteristics.After that,a comprehensive evaluation model was established by combining the fuzzy evaluation method and the analytic hierarchy process.The six evaluation indexes of SOx emission control technologies including environmental protection,cost,operation,operability and other factors totally 17 ones were comprehensively evaluated and calculated.The results concluded that closed freshwater wet desulfurization technology is an excellent desulfurization technology;low sulfur fuel technology,LNG alternative fuel technology,open seawater wet desulfurization technology and hybrid wet desulfurization technology are better desulfurization measures,while dry desulfurization technology is a good desulfurization technology.Finally,with the comparative analysis of the real shipboard operation upon the top three comprehensive evaluation scores of SOx emission control technologies,the most economical and environment-friendly SOx emission control technology for marine exhaust gas pollution control with perspective of cost-effectiveness can be selected.The analysis shows that emission control technologies for ships operating within ECA for a long term,the low-sulfur fuel technology has the lowest cost and closed freshwater wet desulfurization technology has higher environmental benefits and maximum return on investment.They are more appropriate marine SOx emission control technologies.