本文選題：褐鐵礦 + 磁化焙燒　； 參考：《內蒙古科技大學》2015年碩士論文

【摘要】：鋼鐵材料是目前及將來長時間內國家經濟發(fā)展的重要基礎之一。然而，，目前我國高品位鐵礦資源已日漸匱乏。以褐鐵礦為代表的低品位難選鐵礦的高效檢選已經成為實現(xiàn)我國經濟、社會可持續(xù)發(fā)展過程中必須解決的問題。 傳統(tǒng)的褐鐵礦焙燒還原主要是在豎爐、沸騰爐和回轉窯等中進行，但是這些設備存在能耗高、還原時間長等缺點，造成設備整體結構及相關技術不過關，不僅還原焙燒質量較差，而且操作管理難度大，結構復雜，投資高，收塵系統(tǒng)復雜�；�于內蒙古固陽褐鐵礦循環(huán)流化床磁化焙燒的開發(fā)項目，為了深入了解微細褐鐵礦粉的還原機理及動力學行為，本文針對褐鐵礦粉在中、低溫下氣體還原的過程建立數(shù)學模型，對褐鐵礦磁化焙燒進行數(shù)值模擬，為低品位褐鐵礦的應用提供理論依據(jù)。 本文運用同步熱分析儀研究CO還原褐鐵礦粉的動力學過程。應用掃描電鏡分析了脫水后褐鐵礦的結構，利用比表面和孔隙度分析儀測定了比表面積和孔隙度的變化。結果表明，褐鐵礦的磁化焙燒是一個很容易進行的反應，在給定的條件范圍內，同時受到環(huán)境溫度、反應氣體濃度和顆粒自身大小的影響。由同步熱分析儀的結果可確定褐鐵礦的反應活化能，細顆粒的礦粉具有較低的活化能。根據(jù)褐鐵礦脫水后的SEM圖和吸附等溫線BET分類分析得出脫水后的褐鐵礦具有高氣孔率，其曲線更符合第Ⅲ類吸附等溫線。 根據(jù)褐鐵礦粉磁化焙燒情況，建立的氣固還原反應的動力學模型包括顆粒內非穩(wěn)態(tài)的傳熱方程、孔隙內氣體傳輸方程和基于描述孔徑分布的改進隨機孔模型的非均相化學反應動力學方程，采用全隱式有限體積法對控制方程進行數(shù)值求解。利用MATLAB，模擬了在不同溫度、不同初始氣體濃度、不同礦粉粒徑及不同初始孔隙率的條件下反應速率和磁化還原所需時間的關系，研究了一氧化碳濃度分布隨孔隙率的變化和不同粒徑、不同溫度下CO濃度沿褐鐵礦顆粒徑向方向分布的情況。結果表明，模型預測結果與實驗結果吻合較好。提高反應溫度可明顯縮短反應完成的時間，褐鐵礦焙燒反應速率與還原氣體CO濃度近似成正比，溫度升高時CO的有效滲入深度減小，當顆粒的粒徑變大時，會影響反應氣體向顆粒內部的傳輸，具有大孔隙率的褐鐵礦將更有利于反應的進行。
[Abstract]:Iron and steel material is one of the important foundations of national economic development at present and in the future. However, high-grade iron ore resources in China are increasingly scarce. The efficient detection and separation of low grade refractory iron ore represented by limonite has become a problem that must be solved in the process of realizing the sustainable development of economy and society in our country. The traditional limonite roasting reduction is mainly carried out in shaft furnace, fluidized bed furnace and rotary kiln, but these equipments have the disadvantages of high energy consumption, long reduction time and so on, resulting in the whole structure of the equipment and related technology being not up to standard. Not only the quality of reduction roasting is poor, but also the operation management is difficult, the structure is complex, the investment is high, and the dust collecting system is complex. Based on the development project of magnetization roasting in circulating fluidized bed of Guyang limonite in Inner Mongolia, in order to deeply understand the reduction mechanism and kinetic behavior of limonite powder, a mathematical model for the reduction process of limonite powder at medium and low temperatures is established in this paper. Numerical simulation of magnetization roasting of limonite provides theoretical basis for the application of low grade limonite. The kinetic process of CO reduction of limonite powder was studied by means of synchronous thermal analyzer. The structure of limonite after dehydration was analyzed by SEM, and the changes of specific surface area and porosity were measured by using specific surface area and porosity analyzer. The results show that the magnetization roasting of limonite is a very easy reaction, which is affected by the ambient temperature, reaction gas concentration and particle size under given conditions. The reaction activation energy of limonite can be determined from the results of simultaneous thermal analyzer. According to the SEM diagram of limonite after dehydration and the BET classification analysis of adsorption isotherm, it is concluded that the dehydrated limonite has high porosity, and its curve is more in line with the third type adsorption isotherm. According to the magnetization roasting of limonite powder, the kinetic model of gas-solid reduction reaction is established, which includes the unsteady heat transfer equation in particles. The gas transfer equation in pores and the heterogeneous chemical reaction kinetics equation based on the improved stochastic pore model describing pore size distribution are numerically solved by the fully implicit finite volume method. The relationship between the reaction rate and the time required for magnetization reduction under different temperatures, different initial gas concentrations, different particle sizes and different initial porosity was simulated by MATLAB. The distribution of carbon monoxide concentration along the radial direction of limonite particles under different particle sizes and temperatures was studied. The results show that the predicted results are in good agreement with the experimental results. Increasing the reaction temperature can obviously shorten the reaction completion time. The roasting rate of limonite is approximately proportional to the CO concentration of the reductive gas, and the effective penetration depth of CO decreases when the temperature increases, and when the particle size becomes larger, the effective penetration depth of CO decreases with the increase of temperature. Limonite with large porosity will affect the transport of reaction gas to the particle, and limonite with large porosity will be more favorable to the reaction.
【學位授予單位】：內蒙古科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TD951

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