循環(huán)流化床飛灰合成地聚物過程中的應用基礎研究
發(fā)布時間：2019-01-08 15:24
【摘要】：循環(huán)流化床飛灰中鈣、硫組分含量較高,導致其難以在傳統(tǒng)水泥行業(yè)實現(xiàn)規(guī)模化利用。從化學組成和礦物組成上來看,循環(huán)流化床飛灰在地聚物合成領域具有廣闊的應用前景,然而灰中大量存在的CaCO_3、CaSO_4和CaO使其地聚反應過程的復雜程度遠高于偏高嶺土基或粉煤灰基地聚反應體系。論文通過在偏高嶺土中分別添加CaCO_3,CaSO_4和Ca(OH)_2來對循環(huán)流化床飛灰進行模擬�；赟iO_2-Al2O_3-CaO-Na2O體系,首先研究了 Na2O/Al2O_3變化對樣品凝結時間和抗壓強度的影響,實驗發(fā)現(xiàn),體系中Na2O/Al2O_3增加有利于偏高嶺土中活性硅、鋁組分的溶出,縮短樣品凝結時間。當養(yǎng)護至90天后,Na2O/Al2O_3為0.7-1.1的樣品中出現(xiàn)八面沸石晶體,而Na2O/Al2O_3為0.6-0.8的樣品中出現(xiàn)A型沸石晶體,這些晶體的生成有利于提升樣品的后期強度。然而,當Na2O/Al2O_3高于1.0,反應體系中因水化石榴石的生成導致地聚反應歷程改變,進而對樣品抗壓強度產生負效應。當堿激發(fā)劑中含有NaCl時,體系中有氯鋁酸鹽生成,樣品抗壓強度降低,因此,為獲得性能優(yōu)異的地質聚合物,堿激發(fā)劑中需保證一定濃度的OH-離子存在。SiO_2/Al2O_3對樣品凝結時間的影響程度高于Na2O/Al2O_3。在反應早期,低SiO_2/Al2O_3(SiO_2/Al2O_32.5)樣品中有沸石晶體的生成,這類晶體能夠提升樣品早期強度;而SiO_2/Al2O_3增加會促使樣品中生成的地聚物類型由Na-PS型向Na-PSS型過渡,后者更有利于樣品后期強度的提高。值得注意的是,樣品中SiO_2/Al2O_3不能過高,否則樣品凝結過快,會導致漿體攪拌不均勻,氣泡逸出困難,使得樣品后期抗壓強度發(fā)展受到影響。利用熔融玻璃粉部分取代(60%)水玻璃,能夠在保持樣品整體SiO_2/Al2O_3不變的基礎上,延長樣品凝結時間,提升高SiO_2/Al2O_3樣品機械強度。通過分別研究CaCO_3,CaSO_4和Ca(OH)_2在堿激發(fā)偏高嶺土體系中的反應歷程發(fā)現(xiàn):CaCO_3對反應起到催化作用,加速樣品凝結,在養(yǎng)護后期主要起到物理填充作用,對強度影響不大;CaSO_4主要參與鈣礬石的形成,鈣礬石可以提升樣品的早期強度,但在養(yǎng)護后期(28天),鈣礬石的生成會導致樣品出現(xiàn)裂紋,影響后期強度發(fā)展;添加Ca(OH)_2的樣品中同時存在火山灰反應和地聚反應。
[Abstract]:The high content of calcium and sulfur in CFB fly ash makes it difficult to realize large-scale utilization in traditional cement industry. In terms of chemical composition and mineral composition, CFB fly ash has a broad application prospect in the field of geopolymer synthesis. However, there is a large number of CaCO_3, in the ash. CaSO_4 and CaO make the process of geopolymerization more complex than that of metakaolin or fly ash base polymerization system. In this paper, CFB fly ash was simulated by adding CaCO_3,CaSO_4 and Ca (OH) _ 2 into metakaolin. Based on the SiO_2-Al2O_3-CaO-Na2O system, the effect of Na2O/Al2O_3 change on the setting time and compressive strength of the samples was studied. It was found that the increase of Na2O/Al2O_3 in the system was beneficial to active silicon in metakaolin. The dissolution of the aluminum component shortens the setting time of the sample. After curing for 90 days, octahedral zeolites were found in samples with Na2O/Al2O_3 of 0.7-1.1, while those with Na2O/Al2O_3 of 0.6-0.8 had A-type crystals. The formation of these crystals is beneficial to the later strength of the sample. However, when the Na2O/Al2O_3 is higher than 1.0, the formation of hydrated garnet in the reaction system results in the change of geopolymerization process, which has a negative effect on the compressive strength of the sample. When the alkali activator contains NaCl, chloraluminate is formed in the system, and the compressive strength of the sample decreases. Therefore, in order to obtain the geopolymer with excellent properties, It is necessary to ensure the existence of certain concentration of OH- ion in alkali activator. The influence of SiO_2/Al2O_3 on the setting time of sample is higher than that of Na2O/Al2O_3.. In the early stage of the reaction, zeolite crystals were formed in the low SiO_2/Al2O_3 (SiO_2/Al2O_32.5) samples, which could enhance the early strength of the samples. The increase of SiO_2/Al2O_3 can promote the transition of polymer type from Na-PS type to Na-PSS type, the latter is more favorable to the later strength of the sample. It is important to note that the SiO_2/Al2O_3 in the sample should not be too high, otherwise, if the sample coagulates too quickly, it will lead to the uneven stirring of the slurry and the difficulty of bubble escape, which will affect the development of the compressive strength in the later stage of the sample. By partially replacing (60%) sodium silicate with molten glass powder, the mechanical strength of high SiO_2/Al2O_3 sample can be improved by prolonging the setting time of the sample on the basis of keeping the whole SiO_2/Al2O_3 of the sample unchanged. By studying the reaction mechanism of CaCO_3,CaSO_4 and Ca (OH) _ 2 in alkali-excited metakaolin system, it is found that CaCO_3 plays a catalytic role in the reaction, accelerates the condensation of the sample, and plays a physical filling role in the later curing period. It has little effect on strength; CaSO_4 is mainly involved in the formation of ettringite, ettringite can enhance the early strength of the sample, but in the late curing period (28 days), the formation of ettringite will lead to cracks in the sample and affect the later strength development. Both pozzolanic reaction and geopolymerization occurred in the samples with Ca (OH) _ 2 addition.
【學位授予單位】：華東理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O635
本文編號：2404798
[Abstract]:The high content of calcium and sulfur in CFB fly ash makes it difficult to realize large-scale utilization in traditional cement industry. In terms of chemical composition and mineral composition, CFB fly ash has a broad application prospect in the field of geopolymer synthesis. However, there is a large number of CaCO_3, in the ash. CaSO_4 and CaO make the process of geopolymerization more complex than that of metakaolin or fly ash base polymerization system. In this paper, CFB fly ash was simulated by adding CaCO_3,CaSO_4 and Ca (OH) _ 2 into metakaolin. Based on the SiO_2-Al2O_3-CaO-Na2O system, the effect of Na2O/Al2O_3 change on the setting time and compressive strength of the samples was studied. It was found that the increase of Na2O/Al2O_3 in the system was beneficial to active silicon in metakaolin. The dissolution of the aluminum component shortens the setting time of the sample. After curing for 90 days, octahedral zeolites were found in samples with Na2O/Al2O_3 of 0.7-1.1, while those with Na2O/Al2O_3 of 0.6-0.8 had A-type crystals. The formation of these crystals is beneficial to the later strength of the sample. However, when the Na2O/Al2O_3 is higher than 1.0, the formation of hydrated garnet in the reaction system results in the change of geopolymerization process, which has a negative effect on the compressive strength of the sample. When the alkali activator contains NaCl, chloraluminate is formed in the system, and the compressive strength of the sample decreases. Therefore, in order to obtain the geopolymer with excellent properties, It is necessary to ensure the existence of certain concentration of OH- ion in alkali activator. The influence of SiO_2/Al2O_3 on the setting time of sample is higher than that of Na2O/Al2O_3.. In the early stage of the reaction, zeolite crystals were formed in the low SiO_2/Al2O_3 (SiO_2/Al2O_32.5) samples, which could enhance the early strength of the samples. The increase of SiO_2/Al2O_3 can promote the transition of polymer type from Na-PS type to Na-PSS type, the latter is more favorable to the later strength of the sample. It is important to note that the SiO_2/Al2O_3 in the sample should not be too high, otherwise, if the sample coagulates too quickly, it will lead to the uneven stirring of the slurry and the difficulty of bubble escape, which will affect the development of the compressive strength in the later stage of the sample. By partially replacing (60%) sodium silicate with molten glass powder, the mechanical strength of high SiO_2/Al2O_3 sample can be improved by prolonging the setting time of the sample on the basis of keeping the whole SiO_2/Al2O_3 of the sample unchanged. By studying the reaction mechanism of CaCO_3,CaSO_4 and Ca (OH) _ 2 in alkali-excited metakaolin system, it is found that CaCO_3 plays a catalytic role in the reaction, accelerates the condensation of the sample, and plays a physical filling role in the later curing period. It has little effect on strength; CaSO_4 is mainly involved in the formation of ettringite, ettringite can enhance the early strength of the sample, but in the late curing period (28 days), the formation of ettringite will lead to cracks in the sample and affect the later strength development. Both pozzolanic reaction and geopolymerization occurred in the samples with Ca (OH) _ 2 addition.
【學位授予單位】：華東理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O635
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