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碱-盐复合激发炉底渣基地质聚合物力学性能及耐久性研究

发布时间:2019-02-22 17:03  文章来源:笔耕文化传播
【摘要】:炉底渣是火力发电厂中燃煤在锅炉或其他燃烧设备燃烧后经排渣口排出的工业废弃物,根据锅炉形式的不同主要分为煤粉炉底渣、固硫型流化床炉底渣和非固硫型流化床炉底渣三种,不同类型锅炉产生的底渣成分存在差异。电厂燃煤燃烧排放的炉底渣日益增多,不仅占用宝贵的土地资源,而且造成多种环境污染。因此,综合开展炉底渣的高效循环利用尤为重要。本文针对炉底渣在制备地质聚合物时综合利用率低、激发剂较为单一且用量大的问题,采用非固硫型循环流化床炉底渣作为唯一原料,探索性的将不同种类的碱激发剂与盐激发剂混合作为复合激发剂制备力学性能优良的炉底渣基地质聚合物,对制备的试件进行力学性能分析及各种矿物相、微观形貌表征。结果表明:在碱-盐复合激发剂中,当碱激发剂Na2SiO3掺量为7.7wt%,盐激发剂Na2SO4掺量为0.5wt%时,制备的炉底渣基地质聚合物试件在室温养护28d龄期的抗压强度高达46.94 MPa,较单一碱(Na2SiO3)激发制备试件的抗压强度增加了15.8%。XRD、SEM以及IR结果表明:碱-盐复合激发加速了炉底渣中莫来石、石灰的水化反应,生成了纤维状的钙矾石(AFt)以及大量无定形的地质聚合物凝胶,导致Si-O键的非对称伸缩振动吸收以及Si-O键的弯曲振动吸收均发生了位移。采用水镁石纤维对碱-盐复合激发炉底渣基地质聚合物进行强化增韧研究,结果表明:当水镁石纤维掺量为0.8wt%时,增韧效果最佳,28d龄期的抗压强度达到50.69 MPa,抗折强度为9.14MPa,较零纤维掺量的抗折强度(7.22 MPa)提高了26.59%。XRD、MIP及SEM结果表明水镁石纤维的加入并未改变地质聚合物的矿物相组成,碱-盐复合激发炉底渣水化反应生成的无定形凝胶将水镁石纤维紧紧包裹,纤维承载桥连拔接的作用;纤维增韧地质聚合物的孔隙率减小,小于20nm的孔体积百分数增加了17.23%,平均孔径变小,试件更加致密,力学性能提高。考察了水镁石纤维增韧碱-盐复合激发炉底渣基地质聚合物耐久性能,结果表明:碱-盐复合激发炉底渣基地质聚合物具有优良的耐高温、耐海水侵蚀性能,但抗冻融性能较差;水镁石纤维增韧碱-盐复合激发炉底渣基地质聚合物试件的耐久性能优于未增韧试件。随着煅烧温度的升高,抗压强度先升高后降低,煅烧800℃时,增韧试件的抗压强度仍高达51.19 MPa;经过28个侵蚀周期,纤维增韧试件的抗压强度为41.83 MPa,抗折强度为4.64 MPa;增韧试件最高可承受40个冻融循环,因此,抗冻融性能有待提高。
[Abstract]:The bottom slag is the industrial waste discharged from the boiler or other combustion equipment after burning in the thermal power plant. According to the different boiler forms, it is mainly divided into the pulverized coal furnace bottom slag, The composition of bottom slag produced by different types of boiler is different from that of fluidized bed slag of fixed sulfur type and that of non-sulfur type fluidized bed slag. The bottom slag discharged from coal combustion in power plant is increasing day by day, which not only occupies valuable land resources, but also causes many kinds of environmental pollution. Therefore, it is particularly important to comprehensively develop the efficient recycling of bottom slag. In order to solve the problem of low comprehensive utilization ratio, single activator and large amount of activator in the preparation of geopolymer, the non-sulfur-fixing circulating fluidized bed bottom slag is used as the sole raw material. Different kinds of alkali activator and salt activator were used as composite activators to prepare the base polymer with excellent mechanical properties. The mechanical properties of the samples were analyzed and all kinds of mineral phases were characterized. The results show that when the amount of alkali activator Na2SiO3 and salt activator Na2SO4 is 7.7wt and 0.5wt% respectively, The compressive strength of the base polymer specimen prepared by the furnace bottom slag is up to 46.94 MPa, at room temperature curing for 28 days, and the compressive strength of the sample excited by single base (Na2SiO3) is increased by 15.8. XRD. The results of SEM and IR show that the hydration reaction of mullite and lime in furnace slag is accelerated by the combination of alkali and salt, resulting in the formation of fibrous ettringite (AFt) and a large number of amorphous geopolymer gels. The asymmetric stretching vibration absorption of the Si-O bond and the bending vibration absorption of the Si-O bond are all shifted. Brucite fiber was used to strengthen and toughen the base polymer of alkali-salt activated slag. The results showed that when the content of brucite fiber was 0.8wt%, the toughening effect was the best, and the compressive strength of 28d age was 50.69 MPa,. The flexural strength was 9.14 MPA, and the flexural strength (7.22 MPa) was increased by 26.59.XRDD-MIP and SEM. The results showed that the addition of brucite fiber did not change the mineral phase composition of geopolymers. The amorphous gel formed by the alkali-salt compound excitation slag hydration reaction tightly encapsulates brucite fiber, and the fiber carries the function of bridge connection and pull-out. The porosity of geopolymer toughened by fiber decreases, the percentage of pore volume less than 20nm increases 17.233.The average pore size becomes smaller, the specimen becomes denser and the mechanical properties are improved. The durability of brucite fiber toughened alkali-salt composite activated slag base polymer was investigated. The results showed that alkali-salt composite activated furnace bottom slag base polymer had excellent resistance to high temperature and seawater erosion. But the freeze-thaw resistance is poor; The durability of brucite fiber toughened alkali-salt composite activated slag base polymer specimen is better than that of untoughened specimen. With the increase of calcination temperature, the compressive strength increased first and then decreased. At 800 鈩,

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