低浓度SO₂烟气处理及NO₂和CO₂对其过程的影响研究

【作者】 张丽；

【导师】 秦毅红；

【作者基本信息】 中南大学 ， 冶金物理化学， 2010， 硕士

【摘要】 我国S02排放量高居世界各国前列,由此带来的大气污染和酸雨问题十分严重,经济损失巨大,已成为制约我国经济社会可持续发展的主要因素之一,控制S02污染已势在必行。湿法脱硫以其脱硫效率高、适应范围广、技术成熟等优点得以广泛应用。其中,应用最广泛的是石灰石—石膏洗涤法,但该方法存在固体沉积易使装置结垢堵塞,设备腐蚀、磨损严重,运行、维护费用高,副产品的综合利用价值低等缺点。硫化钠溶液吸收-还原硫法烟气脱硫,具有操作简单,固体废料少,无废水废渣排放,脱硫效率高,产品易于储存和运输等优点,是未来二氧化硫烟气治理颇具前景的脱硫技术。为了将硫化钠溶液吸收-还原硫法较好地应用于低浓度S02烟气的治理,本文通过热力学分析以及条件实验,对Na2S溶液吸收低浓度S02烟气以及NO2和CO2对吸收过程的影响进行了研究,并得出以下结论：(1)通过SO2-Na2S-H2O体系的热力学分析可知,液相中主要存在S2O32-、HSO3-、H2SO3以及少量HS-。当吸收液pH值在3-8之间时,液相中基本上只存在S2032-；当吸收液pH值小于3之后,液相中只存在S2032-和HSO3-。(2)Na2S溶液对低浓度S02烟气具有很好的吸收效果,两级总吸收率基本达到100%。吸收液组成主要受气流速度和终点pH值的影响,而且改变气流速度以及吸收液终点pH值均可控制HSO3-和S2032-合适的浓度比。(3)烟气中的NO2不影响S02气体的吸收效果,但消耗吸收剂(Na2S),而且影响吸收液中离子的种类和浓度。NO2抑制S02吸收过程中HSO3-的生成,同时促进该过程中S2032-和SO42-的生成,从而降低HSO3-和S2032-的浓度比。(4)烟气中的CO2也基本不影响S02气体的吸收效果,但迅速降低吸收液的pH值,并且加快溶液中S2-的消耗。CO2会使S02吸收过程中HSO3-的生成量减少,S2032-的生成量增加。更多还原

【Abstract】 SO2 emission in China tops the forefront of the world. The resulting air pollution and acid rain problems are very serious and the economic loss is very huge, which has become one of the main factors to restrict the economic and social sustainable development. Therefore, it is imperative to control SO2 pollution.Wet FGD is of high desulphurization efficiency, adapts to wide range, and its technology is very mature. For these advantages, wet FGD is widely used. Among wet FGD, limestone-gypsum washing is the most widely used, but there are many disadvantages, such as easy rolling skin and blocking devices, serious corroding and abrading equipments, high cost of operation and maintenance, and less comprehensive utilization of by-products and so on. Sodium sulfide solution absorption-reduction of sulfur FGD, whose operation is simple, solid waste is less, waste water discharge is none, desulfurization efficiency is high and product is easy to store and transport, will be a promising desulfurization technology of SO2 gas in future.In order to apply sodium sulfide solution absorption-reduction of sulfur method to SO2 gas in low concentration, sodium sulfide solution absorbing SO2 gas and the impacts of NO2 and CO2 in flue gas on the absorption process were studied in this paper by thermodynamic analysis and conditional experiments, and draw the following conclusions:(1) The thermodynamic analysis of SO2-Na2S-H2O system shows that the liquid mainly includes S2O32-, HSO3-, H2SO3, and a small amount of HS-. When the absorption solution’s pH value is from 3 to 8, the liquid is essentially only S2O32-; when the absorption solution’s pH value is less than 3, the liquid phase includes only S2O32-and HSO3-.(2) Na2S solution is of a good absorption of SO2 gas in low concentration, and the total absorption rate reaches 100%.The liquid content is mainly affected by gaseous flow rate and final pH value. So changing gaseous flow rate and final pH of absorption solution may control suitable concentration ratio between HSO3-and S2O32-.(3) NO2 in the flue gas does not affect the absorption efficiency of SO2 gas,but it consumes absorbent(Na2S) and affects the type and concentration of ions in absorption solution. NO2 inhibites the generation of HSO3- during SO2 absorption process, while promoting the formation of S2O32-and SO42-, which decreases the concentration ratio between HSO3-and S2O32-.(4) CO2 in the flue gas does not affect the absorption efficiency of SO2 gas either.However,it will reduce the absorption solution’s pH rapidly, and speed up the consumption of S2- in the solution. CO2 will reduce the formation of HSO3- during SO2 absorption process, and increase the generation of S2O32-.更多还原