基于脉冲鼓泡和气动搅拌的烟气脱硫工艺及装置研究

发布时间：2018-06-20 12:25

本文选题：环栅 + 布气系统　；参考：《湖南大学》2016年博士论文

【摘要】：二氧化硫的人为排放主要来自于化石燃料的燃烧。我国以煤炭为主的能源消费结构短期内不会发生改变,根据历年中国环境状况公报显示,我国每年向大气排放的二氧化硫超过2000多万吨,对环境和经济造成很大负担。全球的烟气脱硫技术85%以上为湿法脱硫技术,其中美、日、德三国为90%以上。湿法脱硫技术的核心是吸收塔,第一代吸收塔主要有填料塔、湍球塔等,系统使用的工艺几乎都是抛弃法,第二代吸收塔则是用空塔代替填料塔、湍球塔、筛板塔等,空塔不仅使吸收塔内部结构简洁、造价降低,而且减少了结垢,典型代表的塔型有喷淋塔和喷射鼓泡塔。其中喷淋塔起步较早,而喷射鼓泡塔则发展较快。喷射鼓泡塔以气相为分散相、液相为连续相,将二氧化硫的吸收、亚硫酸钙的氧化、结晶以及除尘等工艺过程集中到同一个反应器中进行,具有较高的脱硫效率和除尘效率,工艺运行pH值范围通常控制在3～5,低pH值环境使吸收塔具有较好的氧化速率。但喷射鼓泡塔系统较为复杂、吸收塔的压力损失较大。第三代塔的发展方向是吸收塔大型模块化,同时通过提高烟气的流速来增加反应场中的扰动,加剧湍流,延长烟气在吸收液中的停留时间,从而提高二氧化硫的吸收率。环栅式吸收塔操作原理与喷射鼓泡塔相同,也属于喷射鼓泡吸收塔的一种。但采用单切向进气方式,运行时气流切向进入环形气体通道,带动吸收液径向旋转,进入栅孔内的气流呈脉冲式,气流被径向旋转的吸收液切割成更小的气泡,在栅孔处,气泡呈现向上、向前、向径向搅拌方向的三维上升状况,吸收液产生脉冲式鼓泡,鼓泡层出现剧烈的扰动状态,延长了塔内气、液接触时间。环栅式布气结构结合单切向的进气方式产生脉冲式鼓泡效果,增加吸收塔内的扰动,与第三代塔提高气速用以增加扰动目的一致。对环栅式吸收塔和日本的喷射管式吸收塔做实验比较,结果显示,在进气量以及液位相同时,环栅式吸收塔的压力损失小于喷射管式吸收塔的压力损失,而环栅式吸收塔的鼓泡层高度大于喷射管式吸收塔的鼓泡层高度,在进气量为2800m3/h时,环栅式吸收塔的鼓泡层高度多次达到1000mm以上,且塔内的气液扰动非常激烈,其最高峰值可达1500mm。喷射管式吸收塔的鼓泡层高度在700mm左右。当用相同量的质量浓度为1.37%CaCO3溶液为吸收液,处理气量2300 m3/h,二氧化硫浓度为3000mg/m3,吸收液pH值大于5.2时,环栅式吸收塔的脱硫效率高于喷射管式吸收塔的脱硫效率,环栅式吸收塔中的吸收液有效成分被迅速消耗,没有新鲜浆液补充,当pH值小于5.2后,环栅式吸收塔的脱硫效率低于喷射管式吸收塔的脱硫效率。当吸收塔直径较大时,环栅式吸收塔存在塔中心部位布气不足的缺陷,因而在环栅内部增设喷射管,设计发明气动搅拌吸收塔,并在环形气体通道中安装浮筒搅拌器,用于加强吸收塔内气固液三相的混合效果。浮筒搅拌器没有固定轴,浮于环形通道内的吸收液液面上,其旋转的动能完全由环形通道内的气流提供,转速越快,搅拌均匀所耗时间越短。进气量相同时,气动搅拌吸收塔的系统压力损失小于日式喷射管式吸收塔的压力损失,当进气量为2400 m3/h,二氧化硫浓度为3400mg/m3,脱硫剂为质量浓度1.64%的CaCO3溶液,吸收液pH值为6.0时,气动搅拌吸收塔的脱硫效率达到96%,喷射管式吸收塔的脱硫效率为80%左右,后期吸收液pH值降到4.0时,气动搅拌吸收塔的脱硫效率仍然达到77%,喷射管式吸收塔的脱硫效率为53%左右。喷射鼓泡塔的低pH值运行环境有利于对重金属物质的富集,结合这一特点发明双循环垂直筛板吸收塔,用于处理高浓度含硫烟气的脱硫,同时回收有经济价值的矿渣。双循环吸收塔一级循环为环栅式布气装置,吸收液采用弱碱性矿物浆液,以磷矿浆为例,磷矿浆液用于脱硫后,其中杂质被去除使磷矿得以富集,脱硫后的矿渣可直接加浓硫酸制成普钙(磷肥)就地销售,二级循环为垂直筛板结构,采用碱性较强的吸收液来维持装置的高脱硫效率,以Na2CO3溶液为例,当进气量为2300m3/h,二氧化硫浓度为3400mg/m3,垂直筛板埋入220mm时,吸收塔的总脱硫效率最高达95%,垂直筛板的埋入深度对吸收塔的脱硫效率有较大影响,其它条件不变,垂直筛板埋入深度80mm时的总脱硫效率最高值为78%。本文针对脱硫吸收塔的布气装置、搅拌装置的性能优化以及吸收塔应用方面进行研究。在保证吸收塔高效脱硫的同时,对吸收塔结构进行简化、降低吸收塔的压力损失、提高吸收塔鼓泡效果等方面取得一定成果,同时在应用双循环吸收塔高效脱硫同时回收具有经济价值的矿物质方面做了大量实验,确定双循环吸收塔的最佳操作范围。为具有自主知识产权的吸收塔的大型工业化提供实践基础和理论依据。
[Abstract]:The man-made emissions of sulfur dioxide are mainly from the combustion of fossil fuels. China's coal based energy consumption structure will not change in the short term. According to the Chinese environmental bulletin, the annual emission of sulfur dioxide to the atmosphere is more than about 20000000 tons, causing a great burden on the environment and economy. More than 85% of the technology is wet desulphurization technology, including more than 90% in the United States, Japan and Germany. The core of the wet desulphurization technology is the absorption tower. The first generation absorption towers are mainly packed tower, turbulence tower and so on. The systems used are almost all abandoned methods. The second generation absorption towers use empty towers instead of packed towers, turbulence towers, sieve plates and so on. The air towers not only make absorption of the tower, but the air towers not only make absorption. The inner structure of the tower is concise, the cost is reduced, and the scale is reduced. The typical tower type is the spray tower and the jet Drum Tower. The spray tower starts early, and the jet drum tower develops faster. The jet drum tower takes the gas phase as the dispersed phase, the liquid phase is continuous phase, the absorption of sulfur dioxide, the oxidation of calcium sulfite, the crystallization and the dust removal. The process is concentrated in the same reactor with high desulfurization efficiency and dedusting efficiency. The range of pH value of the process is usually controlled at 3~5. The low pH environment makes the absorption tower have a better oxidation rate. But the injection drum tower system is more complex and the pressure loss of the absorption tower is lost. The direction of the third generation tower is the absorption tower. By increasing the flow velocity of the flue gas to increase the disturbance in the reaction field, increase the turbulence, prolong the retention time in the absorption liquid and increase the absorption rate of the sulfur dioxide. The operation principle of the ring type absorption tower is the same as the jet Drum Tower, but it is one of the jet bubble absorption towers. When the air flow is cut into the annular gas channel, the absorption liquid is rotated in the radial direction, and the air flow into the gate hole is pulsed. The air flow is cut into smaller bubbles by the absorption liquid which is rotated in the radial direction. At the gate hole, the bubbles appear upward, forward, to the radial direction, and the absorption liquid produces pulse bubbling, and the bubble layer appears play. The strong disturbing state prolongs the gas and liquid contact time in the tower. The ring gate type air distribution structure combines with the single tangent inlet mode to produce the pulse bubbling effect, increases the disturbance in the absorption tower, and is in agreement with the third generation tower to increase the gas velocity to increase the disturbance. When the intake and liquid level are the same, the pressure loss of the ring type absorption tower is less than the pressure loss of the ejector type absorption tower, and the bubble layer height of the ring type absorption tower is larger than the bubble layer height of the ejector type absorption tower. When the intake volume is 2800m3/h, the bubble layer height of the ring type absorption tower is more than 1000mm, and in the tower. The maximum peak of the gas and liquid disturbance can reach the height of the bubble layer of the 1500mm. jet tube absorption tower at about 700mm. The desulfurization efficiency of the ring type absorption tower is higher than the ejector tube when the same quantity of mass concentration is 1.37%CaCO3 solution as the absorption liquid, the concentration of gas is 2300 m3/h, the concentration of sulfur dioxide is 3000mg/m3, and the pH value of the absorption liquid is greater than 5.2. The effective components of the absorption liquid in the ring type absorption tower are quickly consumed and no fresh slurry is added. When the pH value is less than 5.2, the desulfurization efficiency of the ring type absorption tower is lower than that of the ejector type absorption tower. When the diameter of the absorber is larger, the ring type absorption tower has the defects of the central gas distribution in the central part of the tower. Therefore, the ejector tube is added inside the ring gate, and the pneumatic stirring absorber is designed and invented, and the buoy agitator is installed in the annular gas channel to strengthen the mixing effect of the gas solid liquid three phase in the absorption tower. The buoy agitator has no fixed axis and is floating on the absorption liquid surface in the annular channel, and its rotational kinetic energy is completely from the gas in the annular channel. At the same time, the pressure loss of the pneumatic stirring absorber tower is less than that of the Japanese jet tube absorption tower, when the intake volume is 2400 m3/h, the sulfur dioxide concentration is 3400mg/m3, the desulfurizer is the CaCO3 solution with the mass concentration of 1.64%, and the pH value of the absorption liquid is 6. The desulphurization efficiency of the mixed absorption tower is 96%, the desulfurization efficiency of the jet tube absorption tower is about 80%. When the pH value of the later absorption liquid is reduced to 4, the desulfurization efficiency of the pneumatic stirring absorber tower is still 77%, and the desulfurization efficiency of the ejector type absorption tower is about 53%. The low pH operating environment of the jet bubble column is beneficial to the enrichment of heavy metals. The double circulating vertical sieve plate absorption tower was invented to deal with the desulfurization of high concentration sulfur containing flue gas and recovery of economic value. The first cycle of the double cycle absorption tower is a ring type gas distribution device. The absorption liquid is weak alkaline mineral slurry, and phosphate slurry is used as an example. After the phosphate slurry is used for desulphurization, the impurities are removed to phosphorus. The ore can be enriched, and the slag after the desulphurization can be directly added with concentrated sulfuric acid to sell the calcium phosphate (phosphate fertilizer) in place. The two stage cycle is the vertical sieve plate structure. The high desulfurization efficiency is maintained by the strong alkaline absorption liquid. The Na2CO3 solution is taken as an example, when the intake volume is 2300m3/h, the concentration of the oxygen sulfur is 3400mg/m3, the vertical sieve plate is embedded in 220mm, and the absorption tower is used. The total desulfurization efficiency is up to 95%. The buried depth of vertical sieve plate has a great influence on the desulfurization efficiency of the absorber, and the other conditions are unchanged. The total desulfurization efficiency of the vertical sieve plate when the depth of 80mm is buried is 78%.. This paper studies the air distribution device of the desulphurization absorber, the optimization of the agitator and the application of the absorption tower. At the same time, the structure of the absorption tower is simplified, the pressure loss of the absorber is reduced and the effect of the absorption tower is improved. At the same time, a lot of experiments have been made in the application of the double circulation absorption tower for high efficiency desulfurization and the recovery of the mineral resources with economic value, and the optimum of the double circulation absorption tower is determined. The scope of operation provides practical basis and theoretical basis for large-scale industrialization of absorption towers with independent intellectual property rights.
【学位授予单位】：湖南大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X701.3

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