【作者】 朱哲；

【导师】 任爱玲；

【作者基本信息】 河北科技大学 ， 环境工程， 2009， 硕士

【摘要】 随着我国控制和削减SO₂排放力度的不断加大,烟气脱硫已进入快速发展阶段。半干法脱硫技术具有流程简单、占地面积少、无污水排放等优点,但其副产脱硫灰生成量较高,组成上以硫酸钙、亚硫酸钙和残余脱硫剂为主,如何有效加以资源化利用已成为当前急需解决的重要课题,也是制约相关脱硫技术发展的关键因素。本文采集不同产地的脱硫灰,采用XRF、XRD、SEM、激光粒度分析和TG-DTA等测试手段对其化学成分、物理性质、物相组成、颗粒形貌和热稳定性进行了研究,同时测定了灰中重金属离子、氟离子的溶出特性和PAHs的含量;探讨了不同掺量的硫酸钙、亚硫酸钙、氧化钙及脱硫灰对水泥凝结时间及强度的影响,结合不同龄期水泥水化产物的XRD和SEM结果,分析其对水泥水化和凝结硬化的机理;同时研究了硫酸钙、亚硫酸钙、氧化钙及脱硫灰对水泥早期水化过程中电导率的影响,通过对比掺加脱硫灰的水泥和纯熟料（100%）水泥早期水化产物的微观结构,探讨脱硫灰用作水泥缓凝剂的缓凝机理,最后对添加脱硫灰的水泥耐久性进行了研究。研究表明:1)半干法脱硫灰物相组成主要有CaSO₃、CaSO₄、CaCO₃、刚玉及莫来石等,是高钙型脱硫灰;其颗粒为不规则形,呈多孔状,结构疏松。标准浸出试验结果表明脱硫灰不具有浸出毒性;脱硫灰中的多环芳烃以3、4、5环物质为主。2)在硫酸钙加入量占水泥质量的0.5⁵%,亚硫酸钙加入量不超过水泥质量的2%以及固定CaSO₄掺量3.4%、氧化钙加入量不超过水泥质量的3.2%这三种情况下水泥样品的凝结时间、安定性和强度均符合《通用硅酸盐水泥》（GB 175-2007）标准。掺入硫酸钙的水泥主要水化产物为CSH凝胶、Ca（OH）₂和钙矾石晶体（AFt）,掺入亚硫酸钙的水泥主要水化产物为水化硅酸钙（CSH）凝胶、Ca（OH）₂和单硫型水化硫铝酸钙（AFm）。3)采用BOX-Behnken的中心组合设计模型,以CaSO₄·2H₂O掺入量、CaSO₃·1/2H₂O掺入量以及CaO的掺入量为主要的考察因子（自变量）,探讨水泥体系凝结时间的变化规律。通过响应曲面分析了各因素对凝结时间的影响程度和显著性:硫酸钙掺入量>氧化钙掺入量>亚硫酸钙掺入量,且以硫酸钙掺入量为主要因素。4)固定SO₃为1.5%时,采用脱硫灰复掺矿渣生产的水泥,脱硫灰掺量在12%范围内制成的水泥性能均符合《通用硅酸盐水泥》（GB 175-2007）标准,其中脱硫灰掺量为5%时制成的水泥性能最好。掺入脱硫灰的水泥主要水化产物为AFt、CSH凝胶、AFm和氢氧化钙。5)电导率试验结果表明硫酸钙、亚硫酸钙、脱硫灰都具有缓凝作用。脱硫灰中含有一定量的硫酸钙和亚硫酸钙,它主要通过影响铝酸三钙（C₃A）的水化,水化初期快速产生AFt和AFm的细小晶体,包裹在熟料颗粒表面,阻止熟料矿物与水作用,从而延缓了水化的进程。6)脱硫灰复掺矿渣生产的水泥具有良好的抗冻性和干收缩性,但是较普通硅酸盐水泥此种水泥抗硫酸盐侵蚀较差,可考虑在今后的研究中加入某些外加剂。更多还原

【Abstract】 As the strengthening of SO₂ emission control in China, flue gas desulfurization has entered the rapid development stage. Semi-dry desulfurization technology has some advantages, such as simple process, small space-occupy and no sewage discharge, but the output of byproduct—desulfurization ash is higher, which is composed of calcium sulfate, calcium sulfite and residual desulfurizer etc. How to reuse the ash effectively has become important issues, which is the main constraint of the promotion of semi-dry desulfurization technology. In this experiment, chemical composition, physical nature, phase of composition, particlemorpholog and thermal stability of semi-dry desulfurization ash collected from different plants were studied by XRF, XRD, SEM, laser particle size analysis, TG-DTA and other modern testing means. Heavy metal ions, fluoride ion in the dissolution of the ash and PAHs content were also determined. This article focused on the influence of the different content of CaSO₄, CaSO₃, CaO and desulfurization ash on setting time and strength of cement. Cement hydration products of different ages were tested by XRD and SEM. The mechanism of cement hydration and paste was researched simultaneously. At the same time, the impact of CaSO₄, CaSO₃, CaO and desulfurization ash on the conductivity of cement in the early hydration process were tested respectively. The mechanism of which desulfurization ash is used as cement retarder was explored through comparing the micro-structure of early hydration products of cement produced with desulfurization ash and clinker （100%） cement. At last, a pilot study of durability of cement adding the ash was conducted. The results have been shown as follows:1) Semi-dry desulfurization ash is a kind of high calcium ash which is composed of CaSO₃, CaSO₄, CaCO₃, corundum, and mullite etc. And its particles are irregular in shape and porous. Standard leaching test results show that the desulfurization ash does not have the leaching toxicity, and the content of 3, 4, 5-ring polycyclic aromatic hydrocarbons in desulfurization ash is higher.2) In the three cases of the addition of CaSO₄·2H₂O is from 0.5 to 5%, the incorporation of CaSO₃·0.5H₂O is less than 2% by mass and the amount of CaO did not exceed 3.2% when CaSO₄ content fixed at 3.4% in cement, the setting time, stability and the strength of cement all meet the requirement of《Common Portland Cement》（GB 175-2007）. The hydration products of cement which mixed with CaSO₄ are CSH gel, Ca（OH）2 and ettringite crystals （AFt）, while hydration products of the cement mixed with CaSO₃ are CSH gel, Ca（OH）₂ and single S-typed hydration sulphoaluminate （AFm）.3) The variation of setting time in cement system was studied through Box-Benhnken design and response surface methodology （RSM）, and the main factors are the addition of CaSO₄·2H₂O, CaSO₃·0.5H₂O and CaO. The results showed that the successive order of factors affecting setting time was: CaSO₄·2H₂O incorporation>CaO incorporation>CaSO₃·0.5H₂O incorporation.4) When the addition of SO₃ is fixed at 1.5%, the performance of cement which is produced by desulphurization ash and slag meet the requirement of the standard of《Common Portland Cement》（GB 175-2007） when the addition of desulphurization ash is less than 12% by mass, and when the dosage of desulphurization ash is 5% , it shows the best performance. The hydration products of cement adding desulfurization ash are mainly AFt, CSH gel, AFm and Ca（OH）₂.5) Conductivity test results show that calcium sulfate, calcium sulfite and desulfurization ash have a retarding effect on cement. A certain amount of calcium sulfate and calcium sulfite contained in ash, which mainly influenced the hydration of C₃A. Small crystals of AFt and AFm were formed rapidly in the early hydration, wrapping in the clinker particle surface to prevent the action of clinker minerals and water, which delaying the hydration processes.6) Cement produced by desulphurization ash and slag has good performance of frost resistance and dry shrinkage, but sulphate resistance of which is poor compared with ordinary Portland cement, so it could be considered to add certain admixtures in cement in future study.更多还原