高鋁粉煤灰非晶態(tài)氧化硅高值化利用基礎(chǔ)研究
發(fā)布時(shí)間：2018-08-09 13:49
【摘要】：高鋁粉煤灰年排放量超過2500萬噸,綜合利用率低,大量堆存造成嚴(yán)重的環(huán)境污染。高鋁粉煤灰中氧化鋁含量可達(dá)50%左右,同時(shí)富含大量的非晶態(tài)氧化硅組分。當(dāng)前,研發(fā)經(jīng)濟(jì)可行的氧化鋁提取技術(shù)是高鋁粉煤灰綜合利用的戰(zhàn)略需求,而通過堿法脫除非晶態(tài)氧化硅、提高高鋁粉煤灰鋁硅比是其中的關(guān)鍵環(huán)節(jié)。本文主要針對(duì)高鋁粉煤灰脫硅過程中產(chǎn)生的高堿性脫硅液高值化利用問題,開展了高堿體系中硅基材料可控制備與介質(zhì)循環(huán)的基礎(chǔ)研究,提出了硅酸鈣晶須及保溫材料制備、高比表面二氧化硅聯(lián)產(chǎn)超細(xì)碳酸鈣兩種工藝路線,將為高鋁粉煤灰中伴生非晶態(tài)氧化硅高值化利用提供技術(shù)支撐。主要研究內(nèi)容和結(jié)論如下：(1)針對(duì)高堿體系中硅酸鈣晶須的水熱制備過程,考察了鈣硅比(CA/SI)、堿濃度、反應(yīng)溫度等條件對(duì)硅酸鈣晶型和形貌的影響,建立了反應(yīng)條件與不同形貌及晶型的硅酸鈣晶須對(duì)應(yīng)關(guān)系,并可合成長徑比大于100且分散性良好的變針硅鈣石型晶須；研究發(fā)現(xiàn)硅灰石族硅酸鈣均具有晶須形貌,通過晶面表面能計(jì)算得到變針硅鈣石晶須的軸向和徑向晶面晶面能分別為0.057 eV/A3和0.027 eV/A3,確定晶體軸向的優(yōu)先生長是晶須形貌的成因。(2)提出低溫苛化制備低堿含量無定型水合硅酸鈣(C-S-H),并進(jìn)一步水熱制備硬硅鈣石的新工藝路線；分析表明C-S-H為硅氧四面體鏈狀結(jié)構(gòu),C-S-H中殘留的Na+包括吸附鈉和層間結(jié)合鈉；基于此,開發(fā)了離子交換三級(jí)逆流洗滌工藝,5倍洗水下C-S-H中Na+可降低至0.35%,以此C-S-H為原料可水熱制備得到硬硅鈣石型保溫材料；進(jìn)一步研究發(fā)現(xiàn)過量鋁會(huì)促使晶型轉(zhuǎn)變?yōu)橥胸惸獊硎?但配入硅或加入螯合劑EDTA可以抑制晶型轉(zhuǎn)變。(3)開展了高堿低模數(shù)脫硅液碳化法制備低密度高比表面二氧化硅研究,提出了兩段碳化法制備白炭黑路線,開展了工藝優(yōu)化,白炭黑比表面積最高420.82 m2/g；針對(duì)碳化法制備氣凝膠過程,開展了工藝條件影響考察,優(yōu)化條件下制備氣凝膠密度最低為0.34g/mL,比表面積最高為700.72 m2/g；系統(tǒng)考察了反應(yīng)過程中體系pH值、表面基團(tuán)的變化規(guī)律,發(fā)現(xiàn)溶劑分層導(dǎo)致氣凝膠無法有效表面改性；基于此,采用溶劑預(yù)置換二氧化硅氣凝膠表面形成疏水結(jié)構(gòu),密度可降至0.25 g/mL。(4)針對(duì)碳化殘液循環(huán)利用問題,開發(fā)了苛化過程堿回收和碳酸鈣形貌的協(xié)同控制技術(shù)；考察了工藝條件對(duì)轉(zhuǎn)化率和碳酸鈣形貌的影響,優(yōu)化條件下碳酸根轉(zhuǎn)化率為95.70%,并得到形貌均一、粒徑約100nm超細(xì)碳酸鈣產(chǎn)品；深入研究了反應(yīng)過程中碳酸鈣形貌變化規(guī)律,結(jié)果表明反應(yīng)初始階段碳酸鈣是晶體和無定型的復(fù)合結(jié)構(gòu),反應(yīng)時(shí)間延長,碳酸鈣形貌主要為規(guī)整的正方體顆粒,然后出現(xiàn)其他形狀的碳酸鈣顆粒,堿性條件下,大部分立方體形顆粒開始溶解形成團(tuán)狀物質(zhì)。(5)針對(duì)超細(xì)碳酸鈣晶體顆粒分散性差、易團(tuán)聚的特點(diǎn),利用混合懸浮混合產(chǎn)品排料技術(shù)(MSMPR)開展了高堿體系中碳酸鈣結(jié)晶動(dòng)力學(xué)研究；結(jié)果表明該體系中,碳酸鈣晶體生長是表面反應(yīng)控制,而成核速率則是受粒徑控制,體系中過量的OH-會(huì)與Ca2+結(jié)合導(dǎo)致生長速率常數(shù)和成核速率常數(shù)均較低；團(tuán)聚因子與平均停留時(shí)間呈正比例關(guān)系,氫氧化鈣濃度升高后,懸浮密度的增加則會(huì)導(dǎo)致顆粒間碰撞概率增加從而破壞碳酸鈣顆粒的團(tuán)聚。
[Abstract]:The annual discharge of high alumina fly ash is more than 25 million tons, and the comprehensive utilization rate is low. A large number of storage can cause serious environmental pollution. The alumina content in high alumina fly ash can reach about 50%. At the same time, it is rich in a large number of amorphous silicon oxide components. The key link is to remove the amorphous silicon oxide and improve the ratio of aluminum and silicon to high alumina fly ash. This paper mainly aims at the high value utilization of high alkaline desilication liquid produced in the process of high alumina fly ash deilication. The basic research on the controllable preparation and medium circulation of silicon based materials in the high alkali system is carried out, and the calcium silicate whisker and the heat preservation are put forward. Two process routes of material preparation, high ratio surface silica and superfine calcium carbonate will provide technical support for the high value utilization of associated amorphous silica in high alumina fly ash. The main contents and conclusions are as follows: (1) in the hydrothermal preparation process of calcium silicate whiskers in high alkali system, the calcium silicon ratio (CA/SI), alkali concentration and reaction are investigated. The effects of temperature and other conditions on the crystal form and morphology of calcium silicate have been established. The relationship between the reaction conditions and the crystalline form of calcium silicate whiskers with different morphologies and crystal forms is established. The change of the length to diameter ratio is more than 100 and the dispersibility of the calcium silicate whisker can be synthesized. The study found that the calcium silicate of the wollastonite has the morphology of the crystal whisker and can be calculated by the surface of the crystal. The axial and radial crystal facets of the needle silicon carbide whiskers can be 0.057 eV/A3 and 0.027 eV/A3 respectively. It is determined that the preferential growth of the crystal axis is the cause of the morphology of the whisker. (2) a new process for preparing low alkali content of calcium silicate (C-S-H) with low alkali content and further hydrothermal preparation of hard silicon calcium stone is proposed. The analysis shows that C-S-H is silicon oxygen. The tetrahedral chain structure, the residual Na+ in C-S-H includes sodium adsorbed and interlayer sodium. Based on this, the ion exchange three stage countercurrent washing process is developed. The Na+ can be reduced to 0.35% in the 5 times washing water, and the C-S-H is used as the raw material for the preparation of the hard silicalite type thermal insulation material. Further research has found that the excess aluminum will promote the crystal transformation. For Tobey mullite, silicon or chelating agent EDTA can inhibit crystalline transformation. (3) a low density and low modulus silica solution was developed to prepare low density and high specific surface silica. The process of preparation of white carbon black by two stages of carbonization was put forward, and the surface area of silica was up to 420.82 m2/g. The aerogel process has carried out the influence of the process conditions. Under the optimized conditions, the aerogel density is lowest 0.34g/mL and the specific surface area is 700.72 m2/g. The system pH value and the change law of the surface group are investigated, and the solvent stratification leads to the aerogel without the effective surface modification; based on this, the solvent preposition is used. A hydrophobic structure was formed on the surface of the silica aerogel, and the density could be reduced to 0.25 g/mL. (4) for the recycling of carbonated residue. The synergistic control technology of alkali recovery and calcium carbonate morphology was developed, and the effect of process conditions on the conversion rate and the morphology of calcium carbonate was investigated. The conversion rate of carbonates under optimum conditions was 95.70%, and the results were obtained. The morphology is uniform, the particle size is about 100nm superfine calcium carbonate, and the change regularity of calcium carbonate in the reaction process is deeply studied. The results show that calcium carbonate is a crystal and amorphous composite structure at the initial stage of the reaction, the reaction time is prolonged, the morphology of calcium carbonate is mainly regular cube particles, and then other shapes of Calcium Carbonate Granules and alkali appear. Under the sexual condition, most of the cubic body particles began to dissolve to form a mass of mass. (5) the crystallization kinetics of calcium carbonate in the high alkali system was studied with the characteristics of the poor dispersion of superfine calcium carbonate particles and easy reunion. The results showed that the crystal growth of calcium carbonate was the table in the system. The surface reaction control, while the nucleation rate is controlled by the particle size, the excess OH- in the system will combine with the Ca2+ leading to the low growth rate constant and the nucleation rate constant; the aggregation factor is proportional to the average residence time, and the increase of the concentration of the suspension will lead to the increase of the collision probability between the particles. The reunion of Calcium Carbonate Granules.
【學(xué)位授予單位】：中國科學(xué)院研究生院(過程工程研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TQ127.2
本文編號(hào)：2174266
[Abstract]:The annual discharge of high alumina fly ash is more than 25 million tons, and the comprehensive utilization rate is low. A large number of storage can cause serious environmental pollution. The alumina content in high alumina fly ash can reach about 50%. At the same time, it is rich in a large number of amorphous silicon oxide components. The key link is to remove the amorphous silicon oxide and improve the ratio of aluminum and silicon to high alumina fly ash. This paper mainly aims at the high value utilization of high alkaline desilication liquid produced in the process of high alumina fly ash deilication. The basic research on the controllable preparation and medium circulation of silicon based materials in the high alkali system is carried out, and the calcium silicate whisker and the heat preservation are put forward. Two process routes of material preparation, high ratio surface silica and superfine calcium carbonate will provide technical support for the high value utilization of associated amorphous silica in high alumina fly ash. The main contents and conclusions are as follows: (1) in the hydrothermal preparation process of calcium silicate whiskers in high alkali system, the calcium silicon ratio (CA/SI), alkali concentration and reaction are investigated. The effects of temperature and other conditions on the crystal form and morphology of calcium silicate have been established. The relationship between the reaction conditions and the crystalline form of calcium silicate whiskers with different morphologies and crystal forms is established. The change of the length to diameter ratio is more than 100 and the dispersibility of the calcium silicate whisker can be synthesized. The study found that the calcium silicate of the wollastonite has the morphology of the crystal whisker and can be calculated by the surface of the crystal. The axial and radial crystal facets of the needle silicon carbide whiskers can be 0.057 eV/A3 and 0.027 eV/A3 respectively. It is determined that the preferential growth of the crystal axis is the cause of the morphology of the whisker. (2) a new process for preparing low alkali content of calcium silicate (C-S-H) with low alkali content and further hydrothermal preparation of hard silicon calcium stone is proposed. The analysis shows that C-S-H is silicon oxygen. The tetrahedral chain structure, the residual Na+ in C-S-H includes sodium adsorbed and interlayer sodium. Based on this, the ion exchange three stage countercurrent washing process is developed. The Na+ can be reduced to 0.35% in the 5 times washing water, and the C-S-H is used as the raw material for the preparation of the hard silicalite type thermal insulation material. Further research has found that the excess aluminum will promote the crystal transformation. For Tobey mullite, silicon or chelating agent EDTA can inhibit crystalline transformation. (3) a low density and low modulus silica solution was developed to prepare low density and high specific surface silica. The process of preparation of white carbon black by two stages of carbonization was put forward, and the surface area of silica was up to 420.82 m2/g. The aerogel process has carried out the influence of the process conditions. Under the optimized conditions, the aerogel density is lowest 0.34g/mL and the specific surface area is 700.72 m2/g. The system pH value and the change law of the surface group are investigated, and the solvent stratification leads to the aerogel without the effective surface modification; based on this, the solvent preposition is used. A hydrophobic structure was formed on the surface of the silica aerogel, and the density could be reduced to 0.25 g/mL. (4) for the recycling of carbonated residue. The synergistic control technology of alkali recovery and calcium carbonate morphology was developed, and the effect of process conditions on the conversion rate and the morphology of calcium carbonate was investigated. The conversion rate of carbonates under optimum conditions was 95.70%, and the results were obtained. The morphology is uniform, the particle size is about 100nm superfine calcium carbonate, and the change regularity of calcium carbonate in the reaction process is deeply studied. The results show that calcium carbonate is a crystal and amorphous composite structure at the initial stage of the reaction, the reaction time is prolonged, the morphology of calcium carbonate is mainly regular cube particles, and then other shapes of Calcium Carbonate Granules and alkali appear. Under the sexual condition, most of the cubic body particles began to dissolve to form a mass of mass. (5) the crystallization kinetics of calcium carbonate in the high alkali system was studied with the characteristics of the poor dispersion of superfine calcium carbonate particles and easy reunion. The results showed that the crystal growth of calcium carbonate was the table in the system. The surface reaction control, while the nucleation rate is controlled by the particle size, the excess OH- in the system will combine with the Ca2+ leading to the low growth rate constant and the nucleation rate constant; the aggregation factor is proportional to the average residence time, and the increase of the concentration of the suspension will lead to the increase of the collision probability between the particles. The reunion of Calcium Carbonate Granules.
【學(xué)位授予單位】：中國科學(xué)院研究生院(過程工程研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TQ127.2
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