【作者】 田立江；

【导师】 王丽萍；

【作者基本信息】 中国矿业大学 ， 环境工程， 2010， 博士

【摘要】 在我国经济快速发展、煤炭消耗量持续增加而SO₂减排任务重的严峻形势下,WFGD作为主流烟气脱硫工艺在大型燃煤锅炉SO₂减排中扮演了重要角色。中小型燃煤锅炉因负荷变化大、脱硫系统易结垢腐蚀、湿法除尘脱硫一体化脱硫效率偏低等,通过改进WFGD工艺或研发新型脱硫反应器,改善反应器内气液流场和接触传质性能,优化工艺运行参数,提高烟气脱硫效率,为现有中小型燃煤锅炉湿法烟气脱硫提供技术支持。本论文设计的双循环多级水幕反应器,基于钙基脱硫反应动力学原理,采用双循环运行模式和pH值分段控制,反应器内以双圆锥和导流堰组合生成多级水幕代替常规喷淋塔的多层喷淋;运用AUTOCAD、GAMBIT和FLUENT流场模拟软件对塔内构件和流场进行正交模拟优化,得到塔内流场和气液接触最佳的双圆锥和导流堰组合结构参数。反应器采用下段较低pH值有利于石灰石的溶解和上段较高pH值保证SO₂的吸收的双循环运行模式,协调了石灰石利用率与脱硫效率之间的矛盾,研发的反应器具有运行稳定、脱硫效率高、无结垢腐蚀等性能。以脱硫效率和石灰石利用率为指标,通过正交试验和综合平衡法分析,得出冷态最优试验方案,即空塔风速为3.0 m/s,预处理循环和吸收循环浆液pH值分别为4.8-5.0和5.9-6.1,L/G均为20 L/m3,SO₂浓度为1000mg/m3。在最优试验方案条件运行,脱硫效率为98.2%,石灰石利用率为95.2%, Ca/S为1.03。当预处理循环浆液pH值低至4.0、吸收循环浆液pH值在5.4-5.6时,吸收段内壁易出现软垢。当上、下循环浆液pH值均为7.0时,塔内出现大量硬垢。冷态脱硫性能试验表明:双循环多级水幕反应器在进口SO₂浓度为1000-5000 mg/m3时,脱硫效率高于91.3%;不仅为低浓度SO₂治理提供有效的技术支持,而且突破了常规脱硫技术难以处理高浓度SO₂的限制。添加剂强化脱硫试验结果表明,添加剂的加入改善了浆液条件,促进了石灰石的溶解,有效提高了石灰石利用率和脱硫效率,防止塔内结垢,确保脱硫系统运行的稳定性。己二酸和MgSO4组合的复合添加剂强化脱硫试验结果证明二者间存在协同效应,脱硫效率和石灰石利用率比空白试验、MgSO₄强化和己二酸强化分别高出19.6%、14.32%、8.11%和11%、8%、5%。热湿交换性能试验结果表明,循环浆液温度变化对出口烟气状态的影响大于进口烟气本身的影响;上段循环浆液对烟温、湿度的影响程度要大于下段循环浆液的影响。运用Matlab优化工具箱中的lsqnonlin函数,建立进口烟气状态和工艺参数与出口烟气温度和湿度之间关系的热湿交换数学模型,该模型客观反映了脱硫塔下段进出口烟气状态间的关系,不仅可预测进口烟气温度和湿度的变化对脱硫系统和出口烟气状态的影响,而且可有效调控脱硫反应器的运行。通过正交试验和综合平衡法分析,得出热态烟气条件的最优试验方案,即空塔风速3.0m/s,入塔烟温为105℃,预处理循环和吸收循环浆液pH值和L/G分别为4.5、6.0和18 L/m3、15 L/m³。最优试验方案运行对应的脱硫效率达到88.3%,石灰石利用率为82.2%,钙硫比Ca/S=1.07。当预处理循环浆液pH值为6.0时,反应器入口处极易结垢。L/G对脱硫效率的影响试验表明,吸收循环浆液L/G对脱硫效率的影响要远大于预处理循环浆液L/G的影响。本文利用Eviews软件建立脱硫效率与6种运行参数之间关系的数学模型: 426.44T/Y2-2778.24/Y=4.69V+0.45LGD+0.87LGU+2.67PHD+4.57PHU-100该模型的各项评价指标值均处于精确水平,预测值均值和实际值均值无显著差异。模型的建立有助于从理论角度理解反应器脱硫性能,指导反应器工艺运行参数的调整。该论文有图54幅,表13个,参考文献146篇。更多还原

【Abstract】 With the fast developing of economy and continued increasing consumption of coal, wet flue gas desulfurization （WFGD） acts an important role in large-scale coal-fired boilers’SO₂ emission reduction as a mainly used flue gas desulfurization （FGD） technic, while the medium to small scale coal-fired boilers’flue gas desulfurization situation are unoptimistic and total SO₂ emission amount can not be belittled because of the boilers’load changing frequently, easy scaling and corrode, and lower desulfurization efficicency of integrative devices for dust removal and desulphurization. Through the modification of the WFGD technology or developing the new style desulfurzation reactor, improving the flow field and contacting mass transfer process between gas and liquid, increasing desulfurization efficicency, this paper provide the technological support for medium to small scale coal-fired boilers.The designing of double circulation and multi-stage water film tower in this paper bases on the calcium based desulfuration reaction dynamics, uses double circulation model and pH piecewise control, multi-stage water film produced by double cone and stream guidance weir substitited for the muti-layer sprayers inside the spray tower. In order to achieve the structural parameters of the combination of double cone and stream guidance weir which have the optimum flow field and contacting mass transfer inside the tower, three flow field simulation softwares: Autocad, Gambit and Fluent are used to orthogonal simulate and optimize the components inside the tower in this paper. The reactor uses double circulation running mode, the lower slurry pH was adopted of lower part of reactor in favor of the calcium carbonate’s solubility, while the higher slurry pH was adopted of the upper part of reactor in favor of the absorption of sulfur dioxide. The reactor designed coordinated the contradictory between the limestone utilization and desulfurization efficiency. The designed tower has the advantages of running stabilization, high desulfurization efficiency, none scaling and corrosion.Through the orthogonal experiment and analysis of integrated equilibrium method, the experiment achieved the most favorable running parameters of room temperature state, the gas speed of empty tower is 3.0 m/s, the slurry pH of pretreatment circulation and absorption circulation are 4.8-5.0 and 5.9-6.1 respectively, the liquid versus gas ratio （L/G） of pretreatment circulation and absorption circulation are both 20 L/m³. The desulfurization efficiency is 98.2%, the limestone utilization is 95.2%, and the calcium versus sulfur ratio （Ca/S） is 1.03 when the system running at the optimized situation. Absorption part of inside the reactor appeared soft scale when the slurry pH of pretreatment circulation and absorption circulation lower to 4.0 and 5.4-5.6 respectively. Large numbers of hard scale were arisen both upper and lower part inside the reactor when the slurry pH of pretreatment circulation and absorption circulation both are 7.0. This paper reached an important conclusion through the cold state desulfurization experiment, that is, the designed double circulation and multi-stage water film tower not only find an effective way to treat low SO₂ concentration, but also breakthrough the restriction of traditional desulfurization tower to treat high SO₂ concentration, outlet SO₂ concentration could still meet the discharge standard when the inlet SO₂ concentration higher than 4500 mg/m3.Desulfurization efficiency and stability are improved markedly, the slurry condition that limestone’s solution needed made better, the limestone utilization increased effectively, and scale inside the tower was inhibited when additives are added. The desulfurization efficiency and limestone utilization were uplifted 19.6%, 14.32%, 8.11% and 11%, 8%, 5% when the compound additives added compared with none additives’enhancement, MgSO4 enhancement and adipic acid enhancement. The experimental results show that synergistic effect exists when compound additive of adipic acid and MgSO4 is added. The desulfurization efficiency and limestone utilization were uplifted 19.6%, 14.32%, 8.11% and 11%, 8%, 5% respectively when the compound additives added compared with none additives’enhancement, MgSO4 enhancement and adipic acid enhancement.Through the hot-moisture exchanging experiment, the paper grasped the results of outlet flue gas state effected by inlet flue gas temperature, moisture and slurry temperature. The results showed that the outlet flue gas state effected by slurry temperature is greater than effected by inlet flue gas state, the flue gas temperature and moisture effected by slurry of upper part is greater than slurry of lower part. The paper established the mathematical model of lower part using the function of lsqnonlin which belongs to optimization toolbox. The model not only reflects the relationship of inlet and outlet flue gas states, be used to direct the upper part hot and moisture exchange experiment objectively, but also be use to adjusts and controls the desulfurization system’s running effectively.Through the orthogonal experiment and analysis of integrated equilibrium method, the experiment achieved the most favorable running parameters of hot state flue gas, the gas speed of empty tower is 3.0 m/s, the inlet flue gas temperature is 105℃,the slurry pH and L/G of pretreatment circulation and absorption circulation are 4.5,6.0 and 18 L/m3, 15 L/m3. When the system running at the optimized parameters, the desulfurization efficiency is 88.3%, the limestone utilization is 82.2%, and the calcium versus sulfur ratio （Ca/S） is 1.07. The inlet of reactor easily appears scale when the slurry pH of pretreatment circulation is 6.0. The influence of slurry L/G to desulfurization efficiency shows that desulfurization efficiency effected by absorption slurry L/G is greater than pretreatment slurry L/G.Eviews software was used to establish the mathematical model between the desulfurization efficiency and six running parameters in this paper. The mathematical model contributes to comprehend the reactor’s desulfurization characteristics, instruct the reactor’s actual application and running parameters’adjustment from the angle of theory. The P value, significance, R2 and R 2 value, akaike info criterion, schwarz criterion, and etc. were used to evaluate the model’s significance test, and the paper obtained the optimized model as follows: 426.44T/Y2-2778.24/Y=4.69V+0.45LGD+0.87LGU+2.67PHD+4.57PHU-100All the evaluating indicators of the model are lie in accurate level, the forecast precision is high, and there is no difference between the forecast value and test value. The model not only can help to understand the desufurization characteristics of reactor, but also can direct the double circulation and multi-stage water film tower’s application and adjust the running parameters.更多还原