本文關(guān)鍵詞：焦炭在高爐內(nèi)結(jié)構(gòu)演變行為及多相反應(yīng)機制　出處：《北京科技大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 高爐煉鐵 焦炭 結(jié)構(gòu)演變 多相反應(yīng) 分子動力學(xué)

【摘要】：隨著低碳經(jīng)濟時代的到來,以碳(焦炭)作為能量流和物質(zhì)流主要載體的高爐煉鐵工藝面臨前所未有的挑戰(zhàn)。一方面,大噴煤技術(shù)的廣泛推廣以及高爐大型化對焦炭質(zhì)量提出更加嚴格的要求;另一方面,優(yōu)質(zhì)煉焦煤資源的枯竭以及對焦化行業(yè)污染物排放的嚴格控制使得生產(chǎn)優(yōu)質(zhì)焦炭面臨前所未有的壓力;此外,搗固焦和頂裝焦的同時使用,以及高爐內(nèi)有害元素量的增加,為焦炭質(zhì)量評價帶來困難。因此,亟需深入理解高爐內(nèi)焦炭行為,為焦炭質(zhì)量和性能評價提供參考依據(jù),有效地為煉鐵和煉焦行業(yè)的銜接提供理論結(jié)合點。本文采用模擬實驗、理論計算以及工業(yè)取樣分析等多種研究手段,依據(jù)焦炭在高爐內(nèi)不同區(qū)域的反應(yīng)條件,從微觀層次揭示了焦炭在高爐內(nèi)不同位置的結(jié)構(gòu)演變行為及多相反應(yīng)機制,完善了焦炭在高爐內(nèi)的行為理論。本文通過熱力學(xué)計算及熱重實驗研究了在C-CO_2-Na_2CO_3/K_2CO_3體系下焦炭和石墨碳的氣化動力學(xué)規(guī)律。結(jié)果表明,堿金屬碳酸鹽對石墨碳和焦炭氣化反應(yīng)均有著催化作用,其對石墨碳的催化作用比對焦炭的催化作用明顯。催化效應(yīng)對于石墨碳和焦炭氣化過程都有一個極限,由于焦炭中碳為非均勻亂序結(jié)構(gòu)以及內(nèi)生礦物的催化作用,導(dǎo)致堿金屬碳酸鹽的催化極限值低。動力學(xué)研究表明石墨碳和焦炭的氣化反應(yīng)均存在動力學(xué)補償效應(yīng)。石墨碳氣化過程的活化能能夠被堿金屬碳酸鹽明顯地降低,而焦炭氣化過程很難被進一步降低,這主要是由于焦炭的雜亂碳結(jié)構(gòu)以及內(nèi)生礦物的催化已經(jīng)使得焦炭中碳反應(yīng)的活化能處于較低水平。采用堿化實驗系統(tǒng)地研究了堿金屬蒸氣對焦炭碳結(jié)構(gòu)、礦物結(jié)構(gòu)以及高溫性能的影響規(guī)律。被鉀蒸氣堿化后的焦炭組織受到嚴重破壞,伴隨著有碎屑和焦粉的產(chǎn)生,表明鉀蒸氣對焦炭有很強的直接破壞作用,這種現(xiàn)象被稱為"剝落效應(yīng)",而鈉蒸氣不具有這種直接破壞作用。X射線衍射及元素面掃描實驗證實了被鉀堿化后新生礦物相為六方鉀霞石或者鉀鋁硅酸鹽(KAlSiO_4),被鈉蒸氣堿化后的新生礦物相為鈉鋁硅酸鹽(Na_6Al_4Si_4O_(17)),并且鉀鈉均可以與碳基體產(chǎn)生層間化合物導(dǎo)致碳基體體積膨脹。含鉀礦物和含鈉礦物對焦炭氣化反應(yīng)的催化程度相近。由于鉀蒸氣的直接破壞作用比鈉蒸氣強很多(鉀蒸氣對焦炭有"剝落效應(yīng)",而鈉蒸氣沒有),因此鉀蒸氣在高爐內(nèi)對焦炭性能的破壞能力更大。通過分子動力學(xué)研究了熔融焦炭灰分體系(SiO_2-Al_2O_3-CaO)結(jié)構(gòu)和性能隨著SiO_2含量的變化情況。結(jié)果表明熔體中[AlO_4]四面體結(jié)構(gòu)不如[SiO_4]四面體結(jié)構(gòu)穩(wěn)定,并且存在配位數(shù)高于4的鋁氧多面體結(jié)構(gòu)�；瘜W(xué)成分對鍵長和鍵角的影響非常小,這也表明了體系網(wǎng)絡(luò)結(jié)構(gòu)局部的穩(wěn)定性。隨著SiO_2的還原(減少),體系中橋氧含量降低,而三配位氧的比例增加。隨著SiO_2含量從體系中的減少,Si、Al、Ca和O原子的擴散系數(shù)均明顯增加,這主要是由于Si-O鍵的減少削弱了網(wǎng)絡(luò)結(jié)構(gòu)的穩(wěn)定性。分子動力學(xué)和FactSage計算的粘度值非常接近,且均隨著SiO_2含量的降低而降低,這與實驗結(jié)果一致,這也驗證了本模擬計算方法的可靠性。采用分子動力學(xué)研究了 K_2O和Na_2O兩種堿金屬對熔融焦炭灰分結(jié)構(gòu)和流動性的影響,結(jié)果能夠重現(xiàn)相似體系的實驗結(jié)果并且區(qū)分兩種堿金屬對體系影響的核心差別。兩種堿金屬對局域結(jié)構(gòu)的影響非常微弱,均沒有使得體系中原子間的近鄰距離、次近鄰距離以及配位數(shù)發(fā)生明顯的變化。和預(yù)期的一致,Na~+的擴散能力高于K~+,并且含有Na_2O的體系中的原子擴散能力普遍比含有K_2O的體系中的原子擴散能力要高。體系中原子的總擴散系數(shù)隨著Na_2O含量的增加而增加,從而使得體系的粘度降低;但是體系中原子的總擴散系數(shù)隨著K_2O含量的增加而降低,從而使得體系的粘度增加。通過對風口焦炭和爐缸焦炭的分析,揭示風口區(qū)域焦-渣-鐵的界面特征,詮釋了爐缸焦炭的石墨化及其與爐渣的交互作用。焦炭內(nèi)的灰分在風口位置的高溫區(qū)將會熔融并遷移到焦炭表面,熔融灰分包裹焦炭表面會阻礙焦炭與其他物相(氣、固、液)的反應(yīng)。爐腹渣中的FeO的還原在焦-渣界面發(fā)生,反應(yīng)先在焦炭表面形成一個鐵液層。焦-渣之間的反應(yīng)將通過侵蝕反應(yīng)作用對焦炭的結(jié)構(gòu)和組織產(chǎn)生破壞。所有的爐缸焦炭樣品,無論尺寸大小,均已經(jīng)被嚴重的石墨化。焦炭尺寸越小,其石墨化程度越高,這表明了焦炭在高溫區(qū)的石墨化從表層開始,且石墨化的過程伴隨焦粉的產(chǎn)生。產(chǎn)生的焦粉很容易與渣鐵形成復(fù)雜混合物,這會影響到高爐高溫區(qū)的透氣透液性。爐缸的多孔焦炭內(nèi)部被發(fā)現(xiàn)充滿了爐渣,而焦炭內(nèi)部原始的灰分已經(jīng)完全融入爐渣中。綜上所述,關(guān)于焦炭在高爐內(nèi)的演變行為,本論文在前人研究基礎(chǔ)上,針對幾個尚不清楚的問題展開了系統(tǒng)和全面的研究。深入研究了不同形式堿金屬對焦炭的影響機理,從原子尺度揭示了焦炭熔融灰分的結(jié)構(gòu)演變機制,對工業(yè)解剖高爐的風口焦炭及爐缸焦炭進行了全面表征,為合理評價及高效利用焦炭提供了理論基礎(chǔ)。
[Abstract]:With the era of low-carbon economy, carbon (coke) blast furnace ironmaking process as the energy flow and material flow are the main carrier of the hitherto unknown challenge. On the one hand, pulverized coal injection technology is widely promotion and the large-scale blast furnace, puts forward more strict requirements on the quality of coke; on the other hand, high-quality coking coal resource depletion and coking industry emissions to strictly control the production of high quality coke making faces the hitherto unknown pressure; in addition, at the same time stamping and top charging coke, and increase the amount of harmful elements in the blast furnace, coke quality evaluation difficult. Therefore, to understand the behavior of coke in the blast furnace, to provide reference for the evaluation of the quality and performance of coke. Effective convergence for the iron and coking industry to provide the theory. This paper uses the simulation experiments, several research methods theoretical calculation and industrial sampling analysis etc., On the basis of coke in the blast furnace in different regions of the reaction conditions, reveals the structure of coke in the blast furnace in different positions and evolution behavior of multiphase reaction mechanism from the micro level, improve the behavior theory of coke in the blast furnace. Through thermodynamic calculation and experimental study on the thermal gasification kinetics of coke in the C-CO_2-Na_2CO_3/K_2CO_3 system and the law of graphite. The results show that the alkali metal carbonate on the graphite and carbon gasification reaction of coke has a catalytic effect, catalytic effect of its catalytic effect on the graphite ratio of coke catalytic effect obviously. There is a limit for graphite and coke gasification process, the catalytic effect of carbon in coke for non uniform structure disorder and endogenous minerals the limit leads to the formation of alkali metal carbonate value low. Kinetic studies showed that there were kinetic compensation effect of graphite carbon gasification reaction and coke stone. The activation graphite gasification process can be alkali metal carbonate significantly decreased, and the coke gasification process is difficult to be further reduced, this is mainly due to the catalytic promiscuity carbon structure of coke and endogenous minerals have made carbon in coke reaction activation energy at a low level. The experimental system of alkalization of coke carbon the structure of metal vapor by alkali, influence of mineral structure and high temperature performance. By coke tissue potassium vapor after alkalization was severely damaged, with debris and coke powder, showed that potassium vapor direct damage with a strong effect on coke, this phenomenon is called "peeling effect", and the sodium vapor this is not directly damaging effects of.X ray diffraction and element scan experiment confirmed by alkaline potassium after new mineral phases for the Six Party of kalsilite or potassium aluminum silicate (KAlSiO_4), is after the new alkali sodium vapor Students for the mineral phase of sodium aluminum silicate (Na_6Al_4Si_4O_ (17)), and potassium sodium could produce intercalation compounds resulted in volume expansion of carbon matrix and carbon matrix. Its catalytic extent of potassium bearing minerals and sodium containing minerals on the gasification reaction of coke is similar. Due to the direct damage of potassium vapor than sodium vapor (potassium vapor on many strong coke has "peeling effect", and therefore no sodium vapor), potassium vapor in the blast furnace capacity of coke performance more. Through molecular dynamics study of molten coke ash system (SiO_2-Al_2O_3-CaO) structure and properties change with the SiO_2 content. The results show that the melt [AlO_4] tetrahedral structure as [SiO_4] tetrahedral structure stability the structure and coordination number of aluminum oxide polyhedron are higher than 4. The influence of chemical composition on the bond length and angle is very small, it also shows that the stability of the network structure system with the SiO_2 local. Reduction (reduce), reduce the oxygen content in system, and the three ligand oxygen ratio increased. With the content of SiO_2 from the system reduced, Si, Al, Ca and O atom diffusion coefficient were significantly increased, this is mainly due to the decrease of Si-O bond weakens the stability of network structure. Molecular dynamics and FactSage the calculation of the viscosity is very close, and with the decrease of SiO_2 content decreased, which is consistent with the experimental results, which verifies the reliability of the simulation calculation method. The effects of K_2O and Na_2O of two alkali metal to melt coke ash structure and mobility by using molecular dynamics, the results can reproduce the core difference between similar systems the experimental results and distinguish the effects of two kinds of alkali metal on the system. The influence of two kinds of alkali metal on the local structure is very weak, are not made of neighbor atoms system in distance, the second nearest neighbor distance and the coordination number. Changed significantly. And the expected, the diffusion ability of Na~+ is higher than K~+, atom diffusion and contains Na_2O system in general than the K_2O containing system in atom diffusion is higher. The total diffusion coefficient of atoms in the system increases with the increase of Na_2O content, the viscosity of the system decreased from that; but the total diffusion coefficient of atoms in the system decreases with the increase of K_2O content, which makes the viscosity of the system increased. Through the analysis of tuyere coke and coke hearth, tuyere coke - interface to reveal the characteristics of slag and iron, the interaction of the interpretation of the graphite and coke hearth slag ash in coke. The outlet position in the high temperature zone will melt and migrate to the surface of coke, coke ash melting inclusions surface will hinder the coke and other phases (gas, solid, liquid) reaction. The bosh slag in the FeO reduction in coke slag field The surface reaction occurred before the formation of a molten iron layer on the surface of coke. The coke slag will be produced by the reaction between erosion reaction of coke structure and tissue destruction. All the hearth coke samples, regardless of size, have already been graphitization serious. The coke size is smaller, the higher the degree of graphitization this shows that, the coke in high temperature area of graphite from the surface, and the process of graphitization with coke. Coke powder produced easily with iron slag forming a complex mixture, which will affect the air permeability of blast furnace hearth temperature areas. The internal porous coke was found filled with slag, and coke inside the original ash has been fully integrated into the slag. In summary, on the evolution behavior of coke in the blast furnace, this paper on the basis of previous research, aiming at some unclear issues in a systematic and comprehensive study. Deep research The influence mechanism of different forms of alkali metals on coke is revealed. The mechanism of the evolution of coke ash is revealed from the atomic scale. The anus, coke and hearth coke of the industrial anatomic blast furnace are comprehensively characterized, which provides a theoretical basis for reasonable evaluation and efficient utilization of coke.

【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TF526.1

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