本文選題：硅酸鹽 + 結(jié)晶狀態(tài)��； 參考：《天津大學(xué)》2015年博士論文

【摘要】：隨著礦業(yè)和煤炭行業(yè)的發(fā)展進(jìn)步,各種不同類型的半晶態(tài)硅酸鹽材料層出不窮,由于硅源的提取工藝以及硅酸鹽的合成工藝直接影響了硅酸鹽材料的結(jié)晶狀態(tài)和分子結(jié)構(gòu),進(jìn)而會影響到固液分離效果。因此,研究宏觀水平的過濾效果、介尺度水平的濾餅結(jié)構(gòu)和毛細(xì)作用以及分子水平的結(jié)晶狀態(tài)的耦合機制,并結(jié)合介尺度流場下的分子遷移理論及模擬方法,揭示半晶態(tài)硅酸鹽材料的強化脫水機理,具有重要的理論意義和研究價值。本文針對高鋁粉煤灰顆粒的特殊結(jié)構(gòu),即以莫來石和剛玉為基本構(gòu)架,表面包覆著大量的無定形硅,在充分利用工業(yè)廢熱的前提下,提出了溫度梯度脫硅工藝。溫度梯度脫硅工藝原理是利用低溫反應(yīng)抑制高硅含量的羥基方鈉石的產(chǎn)生,進(jìn)而將高鋁粉煤灰表面的非晶態(tài)硅充分脫除。應(yīng)用該工藝可將脫硅粉煤灰中的鋁硅比從1.92提高至2.51。由于溫度梯度脫硅工藝得到的脫硅粉煤灰過濾困難,為此本文進(jìn)一步研究了添加表面活性劑的強化脫水工藝與機理。結(jié)果表明,在添加量為漿液質(zhì)量的0.6‰陽離子表面活性劑十六烷基三甲基氯化銨時,過濾速度可以提高至原來的2倍,濾餅含水率下降了13%左右。添加表面活性劑之所以能夠強化脫水,是由于脫硅粉煤灰物料的分散度和濾餅毛細(xì)作用得到改善,同時水的表面張力得到降低,進(jìn)而加速了濾餅孔道中的液體流動,最終改善了過濾效果。針對硅酸鈣水熱合成法生產(chǎn)工藝,研究了合成溫度和合成時間對結(jié)晶狀態(tài)的影響規(guī)律。通過跟蹤從活性硅酸鈣轉(zhuǎn)化為硬硅鈣石的過程,基于結(jié)晶狀態(tài)、微觀形貌以及化學(xué)成分分析構(gòu)建了硅酸鈣晶須的生長模型,該模型可用于指導(dǎo)不同結(jié)晶狀態(tài)硅酸鹽材料的過濾分離方法。依據(jù)硅酸鈣晶須生長模型,研究了鋁晶核促進(jìn)硅酸鹽結(jié)晶過程的工藝,結(jié)果表明加入鋁晶核后可以顯著提高結(jié)晶度,最高結(jié)晶度能夠達(dá)到95%左右。在此基礎(chǔ)上,從宏觀水平、介尺度水平和分子水平分析研究了結(jié)晶狀態(tài)與強化脫水之間的耦合作用機理。結(jié)果表明,半晶態(tài)硅酸鹽材料結(jié)晶的過渡階段,由于受到微觀形貌、層間水釋放、比表面積和水分賦存狀態(tài)的影響,具有較優(yōu)的過濾性能,而結(jié)晶狀態(tài)良好的硬硅酸鈣屬于難過濾的物料。在強化脫水過程中,分子水平的結(jié)晶狀態(tài)與宏觀水平的脫水效果之間的耦合可以通過介尺度水平的濾餅結(jié)構(gòu)進(jìn)行研究,而處于介尺度條件下濾餅內(nèi)的微孔通道,其內(nèi)部流場的流動特性不同于與宏觀流場,不僅需要考慮宏觀的重力和壓力作用,還需要考慮微孔中的毛細(xì)作用、分子間作用力、界面張力等。基于此,本文開展了介尺度流場中分子的流動特性研究。研究中定義了一個新的無量綱參數(shù)梯度數(shù)Gr,用來描述分子大小與速度梯度之間的關(guān)系。基于兩相流模型和稀溶液模型,構(gòu)建了分子遷移微擾理論,即以梯度數(shù)展開的動量方程、維森堡數(shù)展開的本構(gòu)方程以及皮勒數(shù)展開的質(zhì)量傳遞方程為基礎(chǔ),利用泰勒公式和微擾方法對分子在介尺度流場中的流動進(jìn)行數(shù)學(xué)演繹分析,得到分子的應(yīng)力張量和濃度分布的理論計算方法。以泰勒渦流場為計算流場,對比了分子遷移微擾理論解析解與布朗動力模擬解,驗證了介尺度條件下分子遷移微擾理論的正確性并得到分子遷移微擾理論的應(yīng)用范圍,即分子遷移微擾理論可以應(yīng)用于梯度數(shù)Gr低于0.208,韋森堡數(shù)Wi低于0.012,皮勒數(shù)Pe低于10的流場中。以含有附加電場的微孔流場為研究背景,從流場的流體動力相互作用以及對流擴散程度兩個方面,對比分析了布朗動力模擬和隨機旋轉(zhuǎn)動力模擬在介尺度分子遷移流場中的應(yīng)用,得到了布朗動力模擬在介尺度分子遷移計算中的適用范圍,即在流體動力相互作用h*小于0.27時,Pe數(shù)低于500時,可以使用布朗動力模擬方法,而當(dāng)流體相互作用和對流強度較高時,必須采用計算成本較高的隨機旋轉(zhuǎn)動力模擬方法。本文的研究結(jié)果為硅酸鹽的合成工藝和過濾分離方法提供了理論依據(jù),為介尺度水平下分子遷移規(guī)律提供了計算方法,對半晶態(tài)硅酸鹽材料的固液分離工藝及微孔流場內(nèi)顆粒流動規(guī)律的研究具有重要的意義。
[Abstract]:With the development and progress of the mining and coal industry, various types of semicrystal silicate materials emerge in endlessly. Because the extraction process of silicon source and the synthesis process of silicate have a direct effect on the crystalline and molecular structure of silicate materials, it will affect the effect of solid-liquid separation. Therefore, the filtration effect of macro level is studied. The coupling mechanism of mesoscale filter cake structure and capillary action and molecular level crystallization state, combined with the molecular migration theory and simulation method under the mesoscale flow field, reveals the strengthening dehydration mechanism of the semicrystal silicate material, which has important theoretical significance and research value. This paper is aimed at the special junction of high alumina fly ash particles. With mullite and corundum as the basic framework, a large number of amorphous silicon is coated on the surface, and a temperature gradient desilication process is put forward on the premise of making full use of industrial waste heat. The principle of temperature gradient desilication is the production of hydroxyl sodium stone with high silicon content by low temperature reaction, and then the amorphous silicon on the surface of high aluminum fly ash. The application of this process can increase the ratio of aluminum and silicon in desilicon fly ash from 1.92 to 2.51. due to the temperature gradient desilication process, which is difficult to filter. Therefore, this paper further studies the strengthening dehydration process and mechanism of adding surfactants. The results show that the addition amount of 0.6 per thousand cationic surface is added to the slurry quality. When the active agent is sixteen alkyl three methyl ammonium chloride, the filtration speed can be raised to 2 times, and the water content of the filter cake is reduced by 13%. The reason that adding surfactants can strengthen the dehydration is due to the improvement of the dispersity of the silica fly ash material and the capillary action of the filter cake, the surface tension of the same water is reduced, and then the filtration is accelerated. The liquid flow in the cake channel eventually improved the filtration effect. According to the process of calcium silicate hydrate hydrothermal synthesis, the influence of the synthesis temperature and time on the crystallization state was studied. The silicic acid was constructed on the basis of the crystallization state, micromorphology and chemical composition analysis by tracking the conversion from active calcium silicate to hard silica. The growth model of calcium whisker can be used to guide the filtration and separation of silicate materials with different crystalline states. Based on the growth model of calcium silicate whisker, the process of promoting the crystallization of silicate by aluminum nucleation is studied. The results show that the crystallinity can be significantly increased after adding aluminum nucleation, and the highest crystallinity can reach about 95%. On the basis of the analysis, the coupling mechanism between the crystallization state and the intensification dehydration is studied from the macro level, the mesoscale level and the molecular level. The results show that the transition stage of the crystallization of the semicrystal silicate material has a better filtration performance due to the influence of the micromorphology, the release of interlayer water, the specific surface area and the water distribution state. In the process of strengthening dehydration, the coupling between the crystalline state of the molecular level and the dehydration effect at the macro level can be studied through the mesoscale filter cake structure during the process of strengthening dehydration, while the microporous channel in the filter cake under the mesoscale condition is different in the flow characteristics of the internal flow field. In the macroscopic flow field, it is necessary to consider not only the macroscopic gravity and pressure effects, but also the capillary action, the intermolecular force and the interfacial tension in the micropores. Based on this, the flow characteristics of the molecules in the mesoscale flow field are studied. A new dimensionless parameter gradient Gr is defined to describe the molecular size and the size of the molecules. The relationship between the velocity gradient. Based on the two phase flow model and the dilute solution model, the theory of the molecular migration perturbation is constructed, which is based on the momentum equation expanded by the ladder number, the constitutive equation of the expansion of the Vivien number and the mass transfer equation of the Peeler number expansion, and the flow of molecules in the mesoscale flow field by the Taylor formula and the perturbation method. The theoretical calculation method of molecular stress tensor and concentration distribution is obtained by mathematical deductive analysis. The Taylor eddy field is used to calculate the flow field. The analytical solution of molecular migration perturbation theory and the Brown dynamic simulation solution are compared. The correctness of the molecular migration perturbation theory under the mesoscale condition is verified and the application scope of the molecular migration perturbation theory is obtained. The theory of molecular migration perturbation can be applied to the flow field in which the number of ladder numbers Gr is below 0.208, the number of Weisenberg is less than 0.012 and the Peeler number Pe is less than 10. With the microporous flow field containing the additional electric field as the research background, the Brown dynamic simulation and the random rotation movement are compared and analyzed from the fluid dynamic interaction of the flow field and the convective diffusion degree in two aspects. The application of force simulation in mesoscale molecular migration flow field is obtained. The application range of Brown dynamic simulation in mesoscale molecular migration is obtained. That is, when the fluid dynamic interaction h* is less than 0.27 and the Pe number is less than 500, the Brown dynamic simulation method can be used. When the fluid phase interaction and convective intensity are high, the calculation must be used. The results of this paper provide a theoretical basis for the synthesis of silicate and the filtration separation method, and provide a calculation method for the molecular migration under the mesoscale level. The study on the solid-liquid separation process and the particle flow law in the micropore flow field of the semi crystalline silicate material is heavy. The meaning of it.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TQ170.1

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