搅拌流化床中超细氧化铁粉流态化及还原实验研究
文献类型：学位论文
| 作者 | 宋乙峰 |
| 学位类别 | 硕士 |
| 答辩日期 | 2011-06-08 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 朱庆山 |
| 关键词 | 搅拌流化床 超细粉 直接还原 失流 金属化率 |
| 其他题名 | Experimental Study on Fluidization and Reduction of Ultrafine Iron Oxide Powder in an Agitation Fluidized Bed |
| 学位专业 | 化学工程 |
| 中文摘要 | 超细铁粉是粉末冶金工业的基础原料之一，被广泛应用于机械、冶金、化工、医药、电子、兵器等领域。工业上生产铁粉的工艺如赫格纳斯法和水雾化法，都不能生产颗粒尺寸在微纳米级的超细铁粉，而超细铁粉制备新技术，如高能球磨法、真空蒸发法、溅射法、羰基法、液相还原法等，由于原料价格高、设备复杂或反应条件苛刻等原因，难以实现大规模的工业化生产。因此亟需发展适用于工业化规模的超细铁粉生产工艺。流化床可以直接处理铁矿粉，具有气固接触充分、传质传热快的特点，被认为是效率最高的直接还原反应器。以超细氧化铁粉为原料进行流态化还原，具有连续、高效生产超细铁粉的前景。但是，由于超细氧化铁粉流态化还原面临超细粉难以均匀流化和还原过程中粘结失流的技术难题，目前还没有实现超细氧化铁粉流态化还原的研究报道。本工作自制了一套内径为50 mm的搅拌流化床，以平均粒径为239 nm的氧化铁粉为原料，进行了超细氧化铁粉的流态化和氢气还原实验，并与普通流化床中的结果进行了比较，主要结论如下：（1）超细氧化铁粉在普通流化床中易出现沟流和节涌，而在搅拌流化床中能以聚团鼓泡形式实现完全流化，最小流化速度为0.025 m/s，最大床层膨胀比为2.0。（2）床层压力波动的分析结果表明，采用低转速（n<180 r/min）操作既能改善流化质量又可以保证流化的稳定性，而实验所用三种桨型中带孔三叶桨效果最好。（3）随着温度升高，最小流化速度增大，流化质量变差，低温有利于提高流态化还原过程中的失流金属化率，但反应速率和氢气利用率随温度降低而显著下降，搅拌流化床中不同温度下还原实验结果表明500 °C是最佳操作温度，还原60 min后样品的金属化率最高。（4）在500 °C下用氢气还原该氧化铁粉的反应过程为Fe2O3→Fe3O4→Fe，Fe颗粒的粒径比Fe2O3小，有颗粒烧结现象，由金属Fe引起的颗粒烧结和粘结可能是导致失流的原因。与普通流化床相比，搅拌能有效抑制沟流和破碎因粘结形成的团聚物，使流化时间由3 min延长至15 min，使失流金属化率由15%提高至76%。 |
| 英文摘要 | Ultrafine iron powder is one of the basic raw materials in the powder metallurgy industry, which is widely used in machinery, metallurgy, chemical engineering, medicine, electronics, weapons and other fields. Industrial production processes, such as Hoganas process or water atomization, are unable to produce ultrafine iron powder with particle size in the micro-nano scale. Also some new technologies have been developed for preparing ultrafine iron powder recently, such as high energy ball milling, vacuum evaporation, sputtering, carbonyl process, liquid phase reduction and so on. However, it is difficult for these methods to be applied in industrialized production because of high cost reagent, complex devices or extreme reaction conditions. Therefore, it is necessary to develop processes that have the capability of producing ultrafine iron powder in industrial scales. Iron ore powder could be reduced in the fluidized bed, which is considered as one of the most efficient direct reduction reactors due to their excellent gas-solid contact efficiency and fast mass and heat transfer rates. By the fluidization reduction of ultrafine iron oxide powder, ultrafine iron powder may be produced continuously and efficiently. However, there are two major technical difficulties for the fluidization reduction of ultrafine iron oxides, as ultrafine powders are difficult to be fluidized homogenously on the one hand. On the other hand, defluidization will occur at certain metallization rate during the reduction process. Up to the present, direct reduction of ultrafine iron oxide via fluidized beds to produce ultrafine iron powders has not been reported. In the present study, an agitation fluidized bed with 50 mm I.D. was established to study the fluidization and reduction of ultrafine iron oxide powder with averaged particle size of 239 nm. The results obtained from the agitation fluidized bed were compared with those obtained from a conventional fluidized bed. The main results as follows: (1) The ultrafine iron oxide powder in the agitation fluidized bed could be completely fluidized in the form of agglomerate bubbling fluidization. The minimum fluidization velocity was 0.025 m/s and the maximum expansion ratio could reach 2.0. (2) The analysis results of pressure fluctuation in the fluidized bed indicated that good quality and stability of the fluidization were obtained at a low agitation speed (n<180 r/min), and the agitator with three perforated blades had the best performance. (3) The minimum fluidization velocity increased and the fluidization quality declined with increasing temperature. Lower temperature was benefit for raising the metallization rate when defluidization occurred, while the reaction rate and the hydrogen utilization efficiency decreased remarkably. The results of reduction experiments at different temperatures indicated that 500 °C was the optimal operating temperature and the highest metallization rate was obtained as the reduction time was 60 min. |
| 语种 | 中文 |
| 公开日期 | 2013-09-23 |
| 页码 | 65 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1669]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 宋乙峰. 搅拌流化床中超细氧化铁粉流态化及还原实验研究[D]. 中国科学院研究生院. 2011. |
入库方式： OAI收割
来源：过程工程研究所
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