电解海水法脱除船舶柴油机废气中NO_x的实验研究

发布时间：2018-09-01 13:46

【摘要】：船舶柴油机排放废气中含有硫氧化物(SOx)、氮氧化物(NOx)、颗粒物(PM)等多种污染物,对大气环境造成了严重污染。IMO海上环境保护委员会第70届会议(MEPC70)将欧洲北海和波罗地海设为氮氧化物排放控制区。为了满足排放控制区的要求,人们提出了多种船舶柴油机废气脱硝方法,如SCR、EGR、湿法洗涤脱硝等方法。但SCR存在工作温度高、催化剂易中毒失效等问题。EGR系统会降低柴油机的热效率,增加CO、PM等排放。湿法洗涤脱硝法可以同时脱除废气中的NOx、SOx以及颗粒物等,但是它要求随船携带氧化剂,且会影响船舶运营的安全性。通过海水电解可制备有效氯溶液,其具有强氧化性,可将NO氧化为易溶于水的高价态氮氧化物,随后通过湿法吸收达到脱硝的目的。因此,本文提出一种基于电解海水的船舶柴油机废气脱硝方法,通过实验探究了该方法的可行性。通过电解实验,研究不同电解条件对电解海水有效氯浓度和pH值的影响。结果表明,随着电解时间、电流密度以及海水盐度的增加,电解海水有效氯浓度近乎线性增加。电解海水pH值随着电解时间的增加先降低后增加,电流密度越低,该现象越明显;随电极间距以及海水盐度降低,电解海水pH值增加。通过非循环喷淋电解海水脱硝实验,研究电解海水中有效氯浓度、pH值、NO和SO2初始浓度对脱硝效果的影响。结果表明,随着有效氯的浓度的增加,NOx脱除率增加,并在有效氯浓度为1000 mg/L时趋于稳定。随着电解海水pH值的增加,NOx脱除率都降低;随着NO初始浓度的增加,NOx脱除率增加,并在大于1000ppm时趋于稳定;随着S02初始浓度的增加,NOx脱除率略有降低,但SO2脱除率始终为100%。通过循环喷淋电解海水脱硝实验,研究有效氯浓度对NOx脱除率以及循环喷淋过程持续时间的影响。结果表明,随着有效氯浓度的增加,NOx脱除率以及循环喷淋过程持续时间均增加。另外,对5S35ME-B9型柴油机进行了电解海水循环脱硝的电解电耗分析,计算结果显示:若使该柴油机NOx排放达到Tier III排放标准,所需电解电耗为352.1 kW/h,占该柴油机额定功率的8.09%。
[Abstract]:The exhaust gas of marine diesel engine contains many kinds of pollutants, such as sulfur oxide (SOx), nitrogen oxide (NOx), particle, (PM) and so on. IMO Marine Environment Protection Committee (MEPC70) established the European North Sea and the Baltic Sea as nitrogen oxide emission control areas at the 70th meeting of the IMO Marine Environment Protection Committee (MEPC70). In order to meet the requirements of emission control area, a variety of marine diesel engine exhaust gas denitrification methods, such as SCR,EGR, wet washing denitrification, have been proposed. However, SCR system can reduce the thermal efficiency of diesel engine and increase the emission of CO,PM and so on. Wet washing and denitrification can remove both NOx,SOx and particulate matter from the exhaust gas, but it requires carrying oxidant with the ship and will affect the safety of the ship operation. The available chlorine solution can be prepared by seawater electrolysis, which has strong oxidizing property and can oxidize NO to high valence nitrogen oxide which is easily soluble in water, and then the denitrification can be achieved by wet absorption. Therefore, a marine diesel engine exhaust gas denitrification method based on electrolytic seawater is proposed in this paper, and the feasibility of this method is explored through experiments. The effects of different electrolytic conditions on the concentration of available chlorine and pH value of electrolytic seawater were studied by electrolytic experiments. The results show that the concentration of available chlorine in electrolytic seawater increases linearly with the increase of electrolysis time, current density and salinity of seawater. The pH value of electrolytic seawater decreases first and then increases with the increase of electrolysis time, the lower the current density, the more obvious this phenomenon is, and the pH value of electrolytic seawater increases with the decrease of electrode spacing and salinity. The effect of available chlorine concentration (pH) and initial concentration of SO2 on denitrification in electrolytic seawater was studied by the experiment of non-circulating spray electrolytic seawater denitrification. The results show that the removal rate of no _ x increases with the increase of available chlorine concentration and tends to be stable when the available chlorine concentration is 1000 mg/L. With the increase of pH value of electrolytic seawater, the removal rate of no _ x decreases, the removal rate of no _ x increases with the increase of initial concentration of NO, and it tends to be stable when the initial concentration of NO is greater than 1000ppm, and the removal rate of no _ x decreases slightly with the increase of initial concentration of S02, but the removal rate of SO2 is always 100%. The effect of available chlorine concentration on the removal rate of NOx and the duration of circulating spray process was studied by the experiment of seawater denitrification by cyclic spray electrolysis. The results show that the removal rate of no _ x and the duration of the cycle spray process increase with the increase of available chlorine concentration. In addition, the electrolytic power consumption of 5S35ME-B9 diesel engine is analyzed by electrolytic seawater cycle denitrification. The calculated results show that if the NOx emission of the diesel engine meets the Tier III emission standard, the required electrolytic power consumption of the diesel engine is 352.1 kW/h, which accounts for 8.09% of the rated power of the diesel engine.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U664.121;X736.3

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