【摘要】：流化床作為效能最高的磁化焙燒反應(yīng)器，在磁化焙燒技術(shù)中發(fā)揮重要作，促進(jìn)復(fù)雜難選鐵礦資源的高效利用，提高低品位鐵礦資源的利用效率。而在流化床焙燒工藝中，焙燒時間(停留時間)是決定低品位鐵礦石還原程度的重要因素，過長會發(fā)生過度焙燒現(xiàn)象，過短會產(chǎn)生欠還原反應(yīng)。因此了解顆粒在流化床內(nèi)的停留時間分布規(guī)律對認(rèn)識和控制磁化焙燒反應(yīng)工藝很有必要。 本研究以內(nèi)置豎直隔板的流化床流動顆粒為對象，并對其在流化床內(nèi)的停留時間進(jìn)行了試驗研究，探討了停留時間與磁化焙燒流化工藝的關(guān)系。在流化床內(nèi)使用豎直隔板將流化床分成不同流化區(qū)域，能夠促使新舊物料更換，停留時間分布均勻，在不同的流化區(qū)域逐級升溫，在出口段區(qū)域達(dá)到最佳焙燒溫度，這樣能有效地改善氣固間的傳質(zhì)和傳熱，提高反應(yīng)轉(zhuǎn)化率及產(chǎn)品的產(chǎn)率。 在顆粒停留時間的試驗研究中，以石英玻璃珠為床料，采用平均停留時間的方法和脈沖法研究。在冷態(tài)試驗臺基礎(chǔ)上研究了進(jìn)料速率、表觀流化氣速、顆粒粒徑、內(nèi)置豎直隔板等因素對顆粒停留時間的影響。平均停留時間的方法研究表明，進(jìn)料速率、表觀流化氣速為影響平均停留時間的主要因素，，平均停留時間隨進(jìn)料速率和表觀流化氣速的增大而減小，在一定范圍內(nèi)，進(jìn)料速率達(dá)到臨界值后，不隨進(jìn)料速率的增大而發(fā)生改變，顆粒在床內(nèi)的停留時間主要取決于表觀流化氣速的改變，且在一定的范圍內(nèi)三者之間有固定線性的關(guān)系；顆粒料徑和中間的隔板高度的影響較大，兩側(cè)通流高度達(dá)到一定高度后對平均停留時間幾乎沒有影響。利用脈沖法研究得到，依據(jù)流化床內(nèi)褐鐵礦粉實際磁化焙燒情況，采用床內(nèi)設(shè)置豎直隔板，改進(jìn)顆粒在流化床反應(yīng)器的流化情況，可解決單流化床的單位容積混合強(qiáng)度不高和減少單床的死區(qū)和短路的問題，顆粒在床內(nèi)的停留時間分布(RTD)更加均勻。表觀流化氣速的增大，RTD分布更加集中，但增大表觀流化氣速停留時間偏離平均停留時間加大；而進(jìn)料速率和粒徑的增大，RTD分布分散。上述的試驗研究結(jié)果能夠為磁化焙燒鼓泡流化床物料停留時間和工業(yè)上采用豎直隔板提供理論依據(jù)。
[Abstract]:As the most effective magnetization roasting reactor, fluidized bed plays an important role in magnetization roasting technology, which promotes the efficient utilization of complex refractory iron ore resources and improves the utilization efficiency of low-grade iron ore resources. In the fluidized bed roasting process, the roasting time (residence time) is an important factor to determine the reduction degree of low-grade iron ore. Therefore, it is necessary to understand the residence time distribution of particles in the fluidized bed and to control the magnetization roasting reaction process. In this study, fluidized bed particles with built-in vertical separator were taken as the object, and their residence time in the fluidized bed was studied experimentally, and the relationship between the residence time and magnetization roasting fluidization process was discussed. In the fluidized bed, the fluidized bed is divided into different fluidized areas by vertical separator, which can promote the replacement of old and new materials, the uniform distribution of residence time, the temperature rise step by step in different fluidized areas, and the optimum roasting temperature in the outlet region. In this way, the mass transfer and heat transfer between the gas and solid can be improved effectively, and the conversion rate and the yield of the product can be increased. In the experimental study of particle residence time, the average residence time method and pulse method were used to study quartz glass beads as bed material. The effects of feed rate, apparent fluidized gas velocity, particle size and built-in vertical partition on particle residence time were studied on the basis of cold test rig. The study on the method of average residence time shows that the feed rate and apparent fluidized gas velocity are the main factors affecting the mean residence time, and the mean residence time decreases with the increase of the feed rate and the apparent fluidized gas velocity, and the average residence time decreases with the increase of the feed rate and the apparent fluidized gas velocity in a certain range. When the feed rate reaches the critical value, it does not change with the increase of the feed rate. The residence time of particles in the bed mainly depends on the change of the apparent fluidized gas velocity, and there is a fixed linear relationship between the three in a certain range. The diameter of particle material and the height of the partition board in the middle have a great influence on the average residence time (RTD) when the height of both sides reaches a certain height. According to the actual magnetization and roasting of limonite powder in fluidized bed, the vertical separator was installed in the bed to improve the fluidization of particles in the fluidized bed reactor. It can solve the problem that the unit volume mixing strength of single fluidized bed is not high and the dead zone and short circuit of single bed are reduced. The (RTD) distribution of particles in the bed is more uniform. With the increase of the apparent fluidized gas velocity, the RTD distribution is more concentrated, but the residence time of the apparent fluidized gas velocity deviates from the average residence time, and the RTD distribution is dispersed with the increase of the feed rate and particle size. The experimental results can provide a theoretical basis for the residence time of magnetized roasted bubbling fluidized bed material and the adoption of vertical separator in industry.
【學(xué)位授予單位】：內(nèi)蒙古科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ051.13

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