基于钠碱海水的船舶柴油机废气脱硫系统设计与实验研究

发布时间：2018-08-18 11:01

【摘要】：随着远洋船舶数量的增加,船舶柴油机废气硫氧化物污染也日益严重,引起了世界各国的关注。依据MARPOL公约附则Ⅵ的规定,自2015年1月1日起,远洋船舶在排放控制区内需燃用含硫量低于0.1%的燃油。为满足日益严格的公约要求,世界各国加大了船舶柴油机废气脱硫技术的研发力度。目前,船舶柴油机湿法废气脱硫技术的研发较为成熟,其应用前景也最为广阔。本文在深入总结和分析现有湿法废气脱硫技术的基础之上,提出了一种改进的基于钠碱海水法的船舶柴油机废气湿法脱硫系统。该系统包括开式和闭式两种工作模式。在开式模式下,系统采用钠碱海水作为废气脱硫洗涤液,既增强了系统的脱硫能力,又使脱硫后洗涤液满足IMO关于脱硫后洗涤液pH值高于6.5的要求;在闭式模式下,系统设置了两个碱液循环柜,两个循环柜中的高浓度碱液在运行过程中交替使用,大大增加了系统在闭式模式下的运行时间;脱硫系统使用水力旋流器组作为洗涤废液离心处理装置。系统可根据运行时洗涤水的流量调整使用的旋流器数量,提高了分离系统的使用灵活性。为验证钠碱海水法在开式模式下脱硫的可行性,本文在自行搭建的模拟船舶废气实验台上进行了废气脱硫实验。实验研究了海水中NaOH浓度、Na_2CO_3浓度和废气中SO_2气体浓度对脱硫率以及洗涤液pH值的影响,并进行了 NaOH和Na_2CO_3混合海水脱硫实验。实验结果表明:当海水中NaOH浓度由零增加至4mmol/L时,洗涤液的脱硫率会提高约4.5%,如果继续提高NaOH浓度至5mmol/L,脱硫率基本保持不变。当废气中SO_2浓度为1143mg/m3时,随着海水中NaOH浓度由零升高至5mmol/L,脱硫后洗涤液pH值会由6.25提高到9.90。当废气中SO_2浓度由1143mg/m3增加至2857mg/m3时,钠碱海水与海水的脱硫率会分别下降15%和20%,脱硫后洗涤液pH值均会下降3.5左右。在相同条件下,NaOH海水的脱硫率要比Na_2CO_3海水高1%～2%,但Na_2CO_3海水保持pH值的能力却明显优于NaOH海水。
[Abstract]:With the increase of the number of ocean-going ships, the pollution of sulfur oxides from marine diesel engine exhaust gas is becoming more and more serious, which has attracted the attention of countries all over the world. According to Annex VI of the MARPOL Convention, from January 1, 2015, the domestic demand of ocean-going ships in the emission control area is to burn fuel containing less than 0.1% sulfur. In order to meet the increasingly stringent requirements of the convention, countries in the world have increased the research and development of marine diesel engine exhaust gas desulfurization technology. At present, the research and development of wet flue gas desulfurization technology for marine diesel engine is relatively mature, and its application prospect is also the most extensive. On the basis of summing up and analyzing the existing wet flue gas desulfurization technology, an improved wet desulfurization system for marine diesel engine exhaust gas based on sodium alkali seawater method is proposed in this paper. The system includes two working modes: open mode and closed mode. In the open mode, the sodium alkali seawater is used as the waste gas desulfurization washing liquid, which not only enhances the desulfurization ability of the system, but also makes the desulfurization washing liquid meet the requirement of IMO that the pH value of the desulphurized washing liquid is higher than 6.5; in the closed mode, Two lye circulating cabinets are installed in the system. The high concentration lye in the two circulating cabinets is alternately used in the operation process, which greatly increases the running time of the system in the closed mode. The desulphurization system uses hydrocyclone as centrifugal treatment unit for washing waste liquid. The system can adjust the number of hydrocyclone used according to the flow rate of washing water, and improve the flexibility of the separation system. In order to verify the feasibility of sodium-alkali seawater desulfurization in open mode, the desulfurization experiment was carried out on a simulated ship exhaust gas test bench. The effects of the concentration of NaOH in seawater and the concentration of SO_2 gas in waste gas on desulfurization rate and pH value of washing solution were studied. The desulfurization experiment of mixed NaOH and Na_2CO_3 in seawater was carried out. The experimental results show that when the concentration of NaOH in seawater increases from zero to 4mmol/L, the desulfurization rate of washing solution will increase by about 4.5%. If the concentration of NaOH continues to increase to 5 mmol / L, the desulfurization rate will remain basically unchanged. When the concentration of SO_2 in waste gas was 1143mg/m3, the pH value of washing solution increased from 6.25 to 9.90 with the increase of NaOH concentration from zero to 5 mmol / L in seawater. When the concentration of SO_2 in waste gas increased from 1143mg/m3 to 2857mg/m3, the desulphurization rate of sodium alkali seawater and seawater decreased by 15% and 20%, respectively, and the pH value of washing liquid decreased about 3.5% after desulphurization. Under the same conditions, the desulphurization rate of Na_2CO_3 seawater is 1 / 2 higher than that of Na_2CO_3 seawater, but the ability of Na_2CO_3 seawater to maintain pH value is obviously better than that of NaOH seawater.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U664.121

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