脱硝脱硫粉煤灰对水泥性能影响的机制及控制技术研究

发布时间：2018-04-01 15:30

本文选题：脱硝　切入点：脱硫　出处：《济南大学》2017年硕士论文

【摘要】：粉煤灰是火电厂燃煤锅炉排放的一种工业废渣,是一种人造的火山灰质材料。利用粉煤灰作为辅助性胶凝组分生产水泥,是其资源化利用的有效途径之一。但近年来火电厂在原有脱硫工艺的基础上加装脱硝设备,致使粉煤灰在建材行业的利用中出现异常气味、拌合物含气量高、胶砂体积膨胀、强度下降等异常现象,限制了粉煤灰在水泥混凝土中的资源化利用。本文针对以上问题采用模拟脱硝脱硫灰的形式,研究了粉煤灰单掺脱硝副产物(NH_4HSO_4)、单掺脱硫副产物(CaSO_4?2H_2O和CaSO_3?0.5H_2O)和复掺脱硝脱硫副产物(NH_4HSO_4、CaSO_4?2H_2O和CaSO_3?0.5H_2O)对水泥体系标准稠度需水量、凝结时间、安定性以及强度等宏观性能的影响规律。利用XRD、SEM-EDS、TG-DSC、水泥水化热测定仪以及压汞仪等测试手段进行机理分析,得出了脱硝脱硫副产物对粉煤灰-水泥体系物相组成、微观形貌、水化产物、水化程度以及孔结构的影响情况。提出了脱硝脱硫粉煤灰的改性方法。研究结果对脱硝脱硫粉煤灰的综合利用以及水泥工业的节能减排、可持续发展具有巨大的经济价值和社会意义。主要研究结果如下:(1)当脱硝副产物NH_4HSO_4掺量大于1.5 wt.%时,随其掺量的增加,初凝时间和终凝时间明显延长,而副产物掺量对水泥需水量及安定性影响较小;当掺量大于1.5 wt.%时,体系各龄期抗压强度和抗折强度随掺量增加逐渐降低;物相组成中出现重铵矾晶体;副产物导致水泥结构28d时无害孔和少害孔数量减少,多害孔数量增加,总孔隙率增加;水泥体系初始水化期的放热速率增加,加速期和衰减期的放热速率降低,水泥水化3d时累计放热总量明显增加。(2)脱硫副产物CaSO_4?2H_2O占比越大,水泥初凝时间和终凝时间越长;当副产物掺量小于2.0 wt.%时,其掺量及CaSO_4?2H_2O和CaSO_3?0.5H_2O的掺加比例对水泥结构3d、7d抗压强度影响较小,28d各组的抗压强度值较空白组高3~7 MPa,而当掺量大于2.0 wt.%时,各组各龄期的抗压强度值降低3~6 MPa;由于CaSO_4?2H_2O的溶解度大于CaSO_3?0.5H_2O,其易与水泥反应生成钙矾石,提高体系的早期强度;副产物CaSO_4?2H_2O对粉煤灰的激活作用明显,随着龄期的延长,体系中的玻璃体相(莫来石和石英)和Ca(OH)_2的衍射峰值逐渐降低。(3)在脱硫副产物掺量2.0 wt.%条件下,随着脱硝副产物掺量的增加,水泥结构3d、7d和28d的抗压强度较空白样分别降低1~3 MPa、1~5 MPa和1~10 MPa,与单掺脱硫副产物各龄期高于空白样1~7 MPa形成鲜明对比;复掺脱硝脱硫副产物造成水泥硬化结构凝胶数量减少,有害孔数量增多,总孔隙率增加,说明脱硝副产物对水泥结构的危害程度远大于脱硫副产物;副产物中的CaSO_4?2H_2O占比越高,粉煤灰的水化程度越高,玻璃体相的衍射峰值越低,体系中非蒸发水含量越高,Ca(OH)_2含量越低。(4)采用预水化方法处理脱硝脱硫粉煤灰,水泥结构3d、7d和28d的抗压强度和抗折强度分别提高1%、4%和9%;通过孔溶液氮含量的测试结果可知,处理后的水泥结构1d龄期氮含量降低68%,7d龄期氮含量降低36%,28d之后体系氮含量维持5%左右;由于处理后的粉煤灰可以有效改善粉煤灰-水泥体系的孔结构,使得总孔隙率降低2.18%;在耐久性方面,其抗氯离子渗透能力与抗硫酸盐侵蚀能力得到大大提高。
[Abstract]:Fly ash is an industrial waste power plant coal-fired boiler emissions, is an artificial volcano gray material. As a supplementary cementitious material in cement production using fly ash, is one of the effective ways of resource utilization. But in recent years, based on the original desulfurization power plant installed denitration equipment, resulting in abnormal smell appeared in the use of fly ash in building materials industry, the mixture with high gas content, mortar volume expansion, abnormal strength decline, limiting the resource utilization of fly ash in cement concrete. According to the above problem with simulated denitrification desulfurization ash in the form of fly ash doped denitration side the product (NH_4HSO_4), single mixed desulfurization by-products (CaSO_4? 2H_2O and CaSO_3? 0.5H_2O) and mixed with the denitration desulfurization by-products (NH_4HSO_4, 2H_2O and CaSO_4? CaSO_3? 0.5H_2O) of cement standard consistency water demand, setting time, stability Influence of the macroscopic properties and strength. The use of XRD, SEM-EDS, TG-DSC, this paper analyzes the mechanism of cement hydration heat test methods and determination of mercury injection apparatus, the denitration desulfurization by-products of fly ash and cement phase composition, microstructure, hydration, hydration degree and the influence of hole the structure of the proposed modified method of desulfurization and denitrification of fly ash. The results of energy-saving emission reduction and comprehensive utilization of desulfurization and denitrification of fly ash and cement industry, has great economic value and social significance of sustainable development. The main results are as follows: (1) when the denitration byproducts of NH_4HSO_4 content is more than 1.5 wt.% when, with the increase of its dosage, initial setting and final setting time was prolonged, and the by-product dosage of cement water requirement and stability influence is small; when the content is greater than 1.5 wt.%, the compressive strength of the system in each age and the flexural strength increased with content The amount decreased; heavy crystal phase composition of alum; by-products resulted in a decrease of harmless hole and less harmful pore number of cement structure 28d, and multi hole number increased, total porosity increased; cement initial hydration exothermic rate period increases, accelerated phase and decay phase of the heat release rate decreased, water cement 3D when the total cumulative heat increased significantly. (2) the desulfurization by-product of CaSO_4? 2H_2O the greater the proportion of cement, initial setting and final setting time is long; when the by-product content is less than 2 wt.%, and the content of CaSO_4? 2H_2O and CaSO_3? 0.5H_2O cases of cement mixing ratio of 3D. Effect of 7D is low compressive strength, compressive strength of 28d were higher than those in control group 3~7 value MPa, and when the content is greater than 2 wt.%, the compressive strength of each age decreased 3~6 MPa; because the solubility of 2H_2O CaSO_4? 0.5H_2O, greater than CaSO_3? It is easy to generate ettringite mud water reaction, improve The early strength of the system; the by-product of CaSO_4? 2H_2O activation of fly ash was increased with age, vitreous body in the system phase (mullite and quartz) and Ca (OH) _2 diffraction peak gradually decreased. (3) in the by-product content under the condition of 2 wt.%, with the increase of removal no by-product content, cement structure 3D, compressive strength of 7D and 28d were lower than the control samples of 1~3 MPa, 1~5 MPa and 1~10 MPa, and only mixed desulfurization by-products in each age is higher than that of the blank sample 1~7 MPa contrast; mixing denitration desulfurization by-products caused by the quantity structure of hardened cement gel decreased the number of harmful pores increased, total porosity increased, indicating the denitration byproducts on the degree of harm is far greater than the concrete structure of the desulfurization by-products; by-products in CaSO_4? 2H_2O the higher the proportion, the higher the degree of hydration of fly ash, the lower the diffraction peak phase of vitreous body, in the system of non evaporable water content High Ca (OH) _2 content is low. (4) the pre hydration treatment method of desulfurization and denitrification of fly ash cement structure, 3D, 7d and 28d compressive strength and flexural strength were increased by 1%, 4% and 9%; the test results showed that the nitrogen content of the pore solution, the cement structure of 1D age N content after treatment decreased 68%, the nitrogen content of 7D age decreased 36%, the 28d system after nitrogen content maintained about 5%; the pore structure of fly ash can effectively improve the fly ash and cement, the total porosity decreased by 2.18%; in terms of durability, the chloride ion penetration resistance and sulfate resistance has been improved greatly.

【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ172.1

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