窑法还原中低品位磷矿的技术研究

发布时间：2018-05-13 01:21

  本文选题：热力学 + 反应层技术　； 参考：《西南科技大学》2017年硕士论文

【摘要】：窑法磷酸是一种结合电热法制黄磷和两步法热法磷酸工艺的新型制磷酸工艺,该工艺能够利用选矿尾矿及高杂质含量的中低品位磷矿、不用硫酸、少用电、残渣可利用等优点。但是由于许多问题仍待解决阻碍了其工业生产,如球团中碳烧损、残渣排放量大、需要保护气氛及CO难以有效利用等。本课题通过反应层技术制备窑法磷酸工艺中所用的新型反应层球团以及复合反应层球团,通过热分析确定了焦炭以及CO作还原剂还原磷矿时的快速还原温度,并通过热力学讨论了C及CO还原磷矿时温度、C/S对还原反应的影响。研究了球团结构、C/S、煅烧温度、空气通入速率等因素对磷矿还原率、残球性能的影响,由此确定了反应层技术下窑法还原磷矿的最佳工艺条件,并在此基础上对残球物相进行了分析,同时测定了残球的力学性能,结果表明残球可作轻质骨料使用。研究结果如下:⑴高温下CO和焦炭都能作为还原剂还原磷矿。随着煅烧温度的升高以及Z值的增大(即C/S的减小),C以及CO还原磷矿反应的?8)在减小、平衡常数在增大。而随着煅烧温度的升高,C还原磷矿的?8)在逐渐减小,而CO还原磷矿的?8)几乎不变,且C还原磷矿的?8)是CO还原磷矿的2倍;随着Z值的增大(即C/S的减小),C以及CO还原磷矿的?8)在逐渐减小。因此,温度的升高以及C/S的减小都有利于C以及CO还原磷矿的反应的进行。⑵空气气氛下,C/S=0.4的普通球团在1300℃下煅烧反应3h后其磷矿还原率最高仅为49.76%;N2气氛下,C/S=0.4的普通球团在1275℃下煅烧反应3h后其磷矿还原率可达96.4%。这说明空气气氛下普通球团虽然有严重的碳烧损问题;而N2保护气氛能够有效地防止普通球团中发生碳烧损。⑶C/S为1.0、造孔材料掺量为8%、碳过剩系数为1.4的球团在1300℃下煅烧3h后(窑内气体流速为500ml/min),球团磷矿还原率达到84.14%。且1250℃煅烧3h后可得到容重为671kg/m3,强度为2.3MPa的空心结构的残球。⑷C/S=0.4的复合反应层球团在1275℃下煅烧3h后,可得到形状保持完整、具有多孔结构的残球,此时球团的磷矿还原率可达86.74%(第一反应层磷矿还原率可达95.44%,第二反应层磷矿还原率可达78.03%);同时所得残球的容重为794kg/m3,单粒抗压强度为1.24MPa,符合国家标准可作轻骨料使用。
[Abstract]:Kiln phosphoric acid is a new phosphoric acid process combined with electrothermal phosphoric acid process and two-step thermal phosphoric acid process. The process can utilize the advantages of ore dressing tailings and low grade phosphate rock with high impurity content, no sulfuric acid, less electricity consumption and residue utilization. However, many problems still remain to be solved, such as carbon burning in pellets, large residual emissions, need to protect atmosphere, and CO is difficult to be effectively used. In this paper, the new reaction layer pellets and composite reactive layer pellets used in kiln phosphoric acid process were prepared by reactive layer technology. The rapid reduction temperature of coke and CO as reductant for reducing phosphate rock was determined by thermal analysis. The effect of temperature (C / S) on the reduction of phosphate rock by C and CO was discussed by thermodynamics. The effects of pellet structure C / S, calcination temperature and air flow rate on the reduction rate of phosphate rock and the properties of residual ball were studied, and the optimum technological conditions for the reduction of phosphate rock by kiln method under reactive layer technology were determined. On this basis, the phase of the residual ball was analyzed, and the mechanical properties of the remnant ball were measured. The results show that the residual ball can be used as lightweight aggregate. The results are as follows: at high temperature, CO and coke can be used as reductant to reduce phosphate rock. With the increase of calcination temperature and the increase of Z value (that is, the decrease of C / S), the equilibrium constant is increasing. However, with the increase of calcination temperature, the Ca-8) decreased gradually, but the CO reduced Phosphate almost remained unchanged, and the C- 8) of the C-reduced phosphate rock was twice as high as that of the CO reduced phosphate rock. With the increase of Z value (that is, the decrease of C / S) and the decrease of CO reduced phosphate rock, the value of C / S decreases gradually. Therefore, The increase of temperature and the decrease of C / S are beneficial to the reduction of phosphate rock by C and CO. The reduction rate of C / S _ (0.4) ordinary pellets calcined at 1300 鈩，

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