【作者】 徐晖；

【导师】 张书廷；

【作者基本信息】 天津大学 ， 环境工程， 2010， 博士

【摘要】 烟气脱硫是控制二氧化硫污染最有效的手段之一。目前常用的烟气脱硫技术存在着脱硫副产物大部分被废弃、利用率低,且对环境造成二次污染等问题,阻碍了现行烟气脱硫技术的发展。因此开发废弃物产生量少,且能同时回收SO₂资源的新型烟气脱硫技术尤为重要,其中SO₂气体的富集和吸收液的再生就成为关键技术问题。本文探索了一种脱硫富液超声波解吸再生的新方法,利用超声波的“空化作用”和“声喷流作用”促进钠碱脱硫富液中SO₂气体的脱除,对吸收富液再生的同时使SO₂气体得到富集。根据化学平衡和气液传质关系,推导得到了SO₂气体解吸过程中解吸平衡容量与溶液pH值、Na⁺浓度和温度的相互关系,以及SO₂气体解吸过程传质速率方程,为后续解吸研究提供理论基础。通过对超声波解吸和传统的加热解吸进行实验对比,结果表明脱硫富液pH值为2.0～4.0范围内超声波对解吸具有显著的促进作用,且pH值越低超声波促进作用越大,当脱硫富液pH值为2.0时,超声作用的解吸速率比纯加热解吸时提高1.38倍。随着pH值的升高,解吸促进效果减弱,当pH值大于4.0后,超声波不再具有促进作用。对解吸过程脱硫溶液成分进一步研究表明超声波对脱硫富液的促进主要是加快了富液中H2SO3向SO₂的分解过程,从而提高解吸过程的总体积传质系数KL ? a。利用自行设计的超声波反应器进行钠碱脱硫富液解吸实验研究,重点考察了脱硫富液液面深度、富液初始pH值、温度、富液中Na⁺浓度以及超声波功率等因素对SO₂解吸量和解吸率的影响;并对各参数进行了综合分析,得出较为经济、高效的操作条件,即脱硫富液深度7.9cm;初始pH值2.0,温度60℃,NaHSO3浓度1.0mol/L,超声波功率30W;在此条件下超声波解吸作用180min,就能够得到0.267mol/L的解吸量以及85%的解吸率。在解吸过程中发现,与纯加热解吸相比,超声波解吸虽然单位时间的水分蒸发量有所增加,但是由于超声波大幅度提高了SO₂解吸速率,因而能够最终减少解吸过程的整体水分蒸发量,节省了能量损耗。另外,对脱硫富液中硫酸根离子含量的研究表明,超声波解吸过程中硫酸根离子含量基本保持稳定,超声波能够抑制亚硫酸根离子向硫酸根离子的转化,从而避免吸收液在再生过程中的劣化。本论文主要对钠碱脱硫富液的超声波解吸方法进行探索和机理解析,可以为烟气脱硫富液的再生技术提供新的思路。更多还原

【Abstract】 Flue gas desulfurization （FGD） is one of the most effective technologies to control sulfur dioxide pollution. Currently, FGD technology commonly used have some problems of abandonment or low utilization of most desulfurization by-product and secondary pollution for environment, which hinder the development of these existing FGD technologies. Therefore, the development of new FGD technology with small waste production and SO2 resources recovery is particularly important, in which, SO2 enrichment and FGD solution regeneration is a key point. In this thesis, a new ultrasonic desorption regeneration method of desulfurization rich solution was explored, by using“cavitation”and“fountain”of ultrasound to promote SO2 removal, thus SO2 gas was enriched and at the same time desulfurization rich solution was regenerated.Based on the chemical equilibrium and gas-liquid mass transfer equation, the relationship between desorption capacity with pH value, sodium ion concentration and temperature was deduced, and the mass transfer rate equation of SO2 gas was also obtained in the desorption process. These could provide the theoretical basis for future desorption research.According to the contrast of ultrasound desorption with conventional heating desorption experiments, the results showed that ultrasound could significantly promote the SO2 desorption from sodium alkali desulfurization rich solution in the pH value range of 2.0 to 4.0, and the promotion of ultrasound desorption increased with decrease of pH value. When the pH value of desulfurization rich solution was 2.0, the ultrasound desorption rate increased by 1.38 times than that of heating desorption. The effect of ultrasonic desorption weakened with the pH value increased, and when the pH value was higher than 4.0, the promotion was ignored. Furthermore, by analyzing the composition of desulfurization rich solution with different pH value, the results indicated that the use of ultrasound accelerated mainly the decomposition from H₂SO₃ to SO2, thus total volume mass transfer coefficient K L?a was enhanced in the desorption process.The experiments of ultrasonic desorption of sodium alkali desulfurization rich solution were carried out in the self-designed ultrasonic reactor. The influence of various parameters, including the depth of desulfurization rich solution, the initial pH value, temperature, sodium ion concentration and ultrasonic electric power, on SO₂ desorption amount and desorption rate were researched. Moreover, through the comprehensive analysis of above parameters, a economical and efficient operating condition was obtained, which was depth of desulfurization rich solution of 7.9 cm; initial pH value of 2.0, temperature of 60℃, NaHSO3 concentration of 1.0 mol/L and ultrasonic electric power of 30 W. Under this optimal condition, 0.267 mol/L of desorption amount and 85 % of desorption efficiency were yielded after 180 min ultrasonic vibration.In the desorption process, the water evaporation amount per minute under ultrasound desorption was slightly higher than that with pure heating desorption. Conversely, the total water evaporation amount was lower than that heating desorption at the same SO₂ desorption amount. Therefore, the energy consumption was saved owing to the higher SO₂ desorption rate under ultrasound. In addition, the study on sulfate radical content in desulfurization rich liquid showed that it remained stable level generally, thus it could be considered that ultrasound could restrain the conversion from sulfite radical to sulfate radical, and avoid deterioration of desulfurization solution in the regeneration process.This thesis mainly focused on the method and mechanism explorations of ultrasound desorption from sodium alkali desulfurization rich solution, and it could provide new ideas for the regeneration technology of FGD rich solution.更多还原