Application Research On New Liquid Oxidant In Integrated Desulfurization And Denitration Of Marine Diesel Engine Exhaust Gas

The international community has long been concerned about the issue of air pollution caused by ships during navigation.In response to this issue,On July 1,2010,the amendment to Annexⅵof the International Convention for the Prevention of Pollution from Ships（MARPOL）came into effect.n this convention,sulfur oxide emissions are capped,and the value has decreased by 88.89 percent year on year;In the set sulfur emission control area,the sulfur emission cap decreased by 93.33%year on year.For nitrogen oxides,the emission limits of low,medium and high speed diesel engines decreased by 76.38%,79.54%and 74.02%compared with the same period last year.Due to the limitation of complicated sailing conditions and narrow ship space,many mature waste gas treatment methods on land are not suitable for marine diesel engine waste gas treatment.After analyzing the advantages and disadvantages of the onshore waste gas treatment technologies,we believe that the wet catalytic oxidation process,especially the liquid oxidant absorption method,is a promising integrated desulfurization and denitrification technology for Marine diesel engine waste gas treatment.The new liquid oxidant used in this paper is iron based liquid oxidant,the main components of the liquid oxidant are:ferrous chloride（Fe Cl₂）and ferrocene（dicyclopentadiene iron）and sulfuric acid.The liquid metal base oxidant prepared by this process has a wide range of use conditions and environment,strong oxidation capacity,high oxidation performance,air regeneration,remarkable economy of circulation,wide application range and prospect.The integrated desulfurization and denitrification of Marine diesel engine exhaust gas was studied by using the iron-based liquid oxidant.The mechanism of the oxidant integrated desulfurization and denitrification,the optimum parameters of the reaction process and the improvement measures of the reaction process were studied.The following conclusions are drawn from the experimental results:（1）It is feasible to integrate desulfurization and denitrification of Marine diesel engine exhaust gas by using the new prepared liquid iron oxidant,and the oxidation mechanism of SO₂ and NO in the reaction is that SO₂ dissolved in the oxidant is oxidized to SO_42-by Fe₃₊and NO.Part of NO is oxidized to NO₂ by oxygen,which is further oxidized to nitric acid,and the other part reacts with dissolved SO₂ to form N₂.（2）The removal rates of SO₂ and NO are different under different reaction conditions,and the main influencing factors are the concentration of oxidizer,reaction temperature and inlet flow rate.The optimal reaction conditions were as follows:the oxidant dilution ratio was 1:10,the air inlet flow rate was 50 m L/min,and the reaction temperature was60℃.（3）Under the optimal experimental conditions,the removal rates of SO₂ and NO in flue gas increased rapidly in the first 60 minutes,but slowed down and reached equilibrium after 60 minutes.SO₂ removal rate is about 95%,NO removal rate is about75%.（4）In the reaction system,with the addition of molecular sieve 13X,NO removal rate is further improved.Under the optimal experimental conditions（10g/L）,the final SO₂ removal rate is about 95%,and NO removal rate increases from 75%to 89%.It can be seen from the experimental results that the new iron-based liquid oxidant prepared by us overcomes the disadvantages of the traditional flue gas desulfurization and denitrification process,and can integrate the harmless treatment of NOx and SOx in the exhaust gas of Marine diesel engine to generate harmless N₂,as well as sulfuric acid and nitric acid that are easy to recover.This process overcomes the disadvantages of traditional flue gas desulfurization and denitration process.Good repeatability while maintaining high treatment efficiency.By comparing the investment returns of several other Marine exhaust gas treatment technologies,this process has obvious advantages in the Marine exhaust gas treatment system,with high efficiency,less investment and low operating cost.Therefore,the liquid oxidant prepared by us has a very broad application range and prospect in the field of Marine exhaust gas treatment.