【作者】 倪伟敏；

【导师】 吴忠标； 郑平；

【作者基本信息】 浙江大学 ， 环境工程， 2007， 博士

【摘要】 双碱法烟气脱硫系统中再生浆液分离和重金属控制有利于提高水的重复利用率，可确保脱硫吸收液的循环回用；氧化浆液分离是脱硫渣资源化利用的重要工序；脱硫废水重金属的有效去除可大大减少外排脱硫废水的二次污染，并使其后续处理并入到常规废水处理成为可能。以上三方面的研究将为双碱法脱硫技术的应用提供重要的匹配技术支撑。首先，本文通过旋流分离和絮凝沉降分离实验，研究了提高再生浆液分离设备处理效果的方法，结果表明，由于再生浆液的自凝聚集特性，旋流分离后清液难以达到回用吸收液含固率指标；而絮凝沉降则能有效提高分离设备处理能力。其次，以分层测定-TOP法获取的沉降速度质量分布定量研究了再生浆液悬浮颗粒沉降性能的改善。结果表明再生浆液的pH对絮凝沉降性能是有利的，但再生浆液中离子浓度在0．035mol／L以上会对絮凝沉降产生不利影响。在TOP法基础上，借助分形理论来研究絮凝形态，结果表明，再生浆液絮凝体沉降速度与特征长度成正比；用CFD技术可预测得到沉降设备表面负荷与絮凝剂量之间的关系，与实际情况较吻合，为实际水处理构筑物设计提供基础数据。再者，通过旋流分离氧化浆液实验，研究了进料压力、进料浓度和旋流器结构等对分离效果的影响，结果表明中心构件加入旋流器内部，增加了进料流量和分股比，改善了分离效果，提高了浓缩效率。根据相似理论建立的准数方程，定量描述中心构件、溢流口直径、进料压力、进料流量、进料浓度等影响因素对分离性能指标的影响规律，为氧化浆液的分离工作提供了预测手段。还研究了氢氧化物沉淀、硫化物沉淀和壳聚糖捕集法处理脱硫废水，结果表明，三种方法均能有效去除重金属离子，去除效率可达到95％以上，但壳聚糖捕集法具有较强的抗离子干扰能力，适合应用于脱硫废水处理。实验证实水中溶解的壳聚糖能够与Zn²⁺和Mn²⁺螯合形成金属配合物，并随pH升高，由壳聚糖螯合作用为主向氢氧化物沉淀作用为主转变。最后，实验证明了壳聚糖同步去除再生浆液重金属和悬浮物的可行性，并研制高分子改性絮凝剂聚硅酸和壳聚糖复合絮凝剂，解决聚硅酸稳定性差和壳聚糖价格高的缺陷，在反应条件和絮凝效果上作了探索性试验，结果表明复合絮凝剂能够有效改善悬浮物沉降性能和抑制水中重金属积累。通过上述研究，解决了冉生浆液难分离和重金属积累的问题，提高了氧化浆液旋流分离效率，改进了脱硫废水处理方法，提出了改进的双碱法脱硫系统水循环工艺，与双碱法FGD过程有良好适应性，具有应用前景。更多还原

【Abstract】 During the process of dual-alkali Hue gas desulphuri/ation （FGD）. it is necessary for the recycle of the absorption solution to separate suspended solids and remove heavy metal ions from the regenerated slurry; it is indispensable for practical utilization of FGD gypsum to separate suspended solids （SS） from the oxidated slurry; it is required for pollution abatement to remove heavy metal ions from FGD wastewater. The study above can be in favor of the water circulation in the FGD with well promotion and the FGD project with well development.Firstly, it was studied that hydrocyclone and flocculation were used to raise the removal efficiency of SS. The results showed that the removal efficiency of hydrocyclone performance was not acceptable due to the self-assemble of SS from the regenerated slurry. The SS concentration of the overflow from hydrocyclone could not meet the demand of the absorption solution. However, flocculation-sedimentation could improve its settling characteristic.Secondly, the top loading method was capable of producing a settling velocity curve. which made the settling characteristic of SS in the regenerated slurry quantified. For the case studied, while a basic pH enhanced the separation. a high ionic strength had an adverse effect, especially more than 0.035mol/L. Based on the method, fractal geometry was introduced in order to characterize highly irregular geometric shapes. It showed that the settling velocity was in proportion to the largest size of SS. On the other hand, the relation between the surface loading rate of the sedimentation tank and the flocculant’s dosage could be predicted by computional fluid dynamics （CFD）. The CFD results were in accordance with the experimental data and could be employed for designing the most cost effective sedimentation tank.Thirdly, hydrocyclone experiment studies on the oxidated slurry were made on relationships among adjustable parameters （input pressure, input concentration and some construction parameters of hydrocyclone）. The results were that center piece in hydrcyclone could raise the input flowrate and the underflow percentage and promote the concentration effect. Dealing with the data gained from experiments with similarity theory, a series of equations were established for the relationships between adjustable parameters and separation efficiency. The equations could provide a foundation for the designing of separation operation.Fourthly, it took neutralization, sulfide precipation and chitosan flocculation to treat FGD wastewater. All of the treatments could remove heavy metal ions effectively and the removal efficiencies could achieve more than 95%. The occurrence of other cations in the solution had little influence on chitosan flocculation for heavy metal ions. The associations between chitosan and heavy metal ions, such as Mn²⁺ and Zn²⁺, were also verified. The pH investigation revealed that there were three stages for different actions: adsorption of chitosan for heavy metal ions, precipitation of heavy metal hydroxide and coprecipitation of heavy metal hydroxide and chitosan- heavy metal complex.Finally, the feasibility of coprecipitation of heavy metal and SS from the regenerated slurry by water-soluble chitosan was studied in a lab scale experiment. Based on this research finding, a composite flocculant of chitosan and polysilicic asid was developed to improve performance and achieve stability. The lab experiment showed that application of the composite flocculant could remove heavy metal ions efficiently and meanwhile improve the settling characteristics of SS from the regenerated slurry.The research work resolved some problem. It was possible to separate suspended solids easily and remove heavy metal ions efficiently from the regenerated slurry. The SS of the oxidated slurry could be separated effectively at the hydrocyclone performance. The treatment of heavy metal ions from FGD wastewater was improved. Based on above, a modified water circulation was proposed and had a potential utilization prospect for its flexibility with the dual-alkali FGD process.更多还原