氧化铁脱除聚氯乙烯中氯元素的反应机制及脱氯固相残存物的高炉冶金性能研究

Iron oxide is employed as the de-chlorination agent at temperature range bewteen 200℃ and 400℃ to remove chlorine in waste poly-vinyl chlorine (PVC) as iron chloride, which can be separated by water leaching, aiming to overcome the disadvantages of high cost and secondary pollution originated from the release of gaseous hydrochloride during the conventional de-chlorination processes. Iron chloride is a valuble chemical feedstock. The solid residue after de-chlorination process is mainly composed of polyene and unreacted iron oxide, a raw material for iron-making, suitable for injection into blast furnace in the place of PCI. During the process, gaseous products such as methane etc. are generated as well and can be collected and utilized as fuel. Therefore, the current innovative de-chlorination process is a low-cost, pollution-free technology..The effects of temperature, heating rate, atmosphere, valence of iron and size of iron oxide particles, mixing ratio of iron oxide to PVC and pressure on the chlorination ratio of iron oxide, the ratio of chlorine fixed in iron chloride to the original chlorine amount in PVC and the micro-structure of solid residue are investigated systemically to clarify the reaction mechanism between iron oxide and PVC. The suitability of solide residue after de-chlorination is assessed by testing the metallurgical properties for injection into blast furnace. The experimenal conditions will be optimized to achieve the maximum chlorination ratio of iron oxide while chlorine from PVC can be fixed in iron chloride completely so that the solid residue after de-chlorination is suitable for injection into blast furnace. The generation of dioxin is mornitored throughout the process. This will provide base knowledge about cleanly and efficiently recycling PVC at low-cost and without secondary pollution to utilize every element in PVC.

针对聚氯乙烯废塑料以气相氯化氢形式脱氯所存在的成本高、易产生二次污染等问题，本课题提出在200-400℃温度范围内利用氧化铁作为聚氯乙烯脱氯剂，以期低耗高效清洁综合回收利用聚氯乙烯废塑料。生成氯化铁通过水浸分离，脱氯后的固相残存物以多烃及未反应的氧化铁为主，伴随反应过程有甲烷等不含氯的气相裂解物生成。氯化铁是重要的化工原料，固相残存物是优良的还原剂及燃料可喷入高炉，气相裂解物可作为燃料。.系统研究温度、升温速度、气氛、氧化铁价态及颗粒粒度、物料混合比、压力等参数对氧化铁的氯化率、聚氯乙烯中氯元素固定于氯化铁中的比率及固相残存物的成分、微观组织结构和高炉冶金性能的影响规律，明确聚氯乙烯与氧化铁的反应机制。优化反应条件使聚氯乙烯中的氯元素完全转化为氯化铁，提高氧化铁的氯化率、确保脱氯后的固相残存物满足高炉喷吹要求并控制二恶英的生成，为高度资源化聚氯乙烯废塑料新技术的建立提供基础理论指导。

采用氧化铁（Fe2O3与Fe3O4）在低于673K脱除聚氯乙烯（PVC）中的氯元素。测试了脱氯后的固相产物多烃及未反应氧化铁进行高炉喷吹的适宜性。此外基于研究结果将脱氯固相产物进行了拓展应用，即经再加热至1273K制备金属铁。结果总结如下:.FactSage计算结果表明Fe2O3及Fe3O4均与PVC在低于673K反应生成FeCl2，还原性气氛有利于FeCl2的生成。氧化铁与PVC的混合质量配比高于40:60时可将PVC中的氯元素完全固定于FeCl2中。.同步热分析协同质谱实验结果表明氧化铁与聚氯乙烯混合物起始反应温度较纯PVC 低15-20K。Fe2O3较Fe3O4降低效果明显，相差5K左右。反应起始温度随升温速率的增加而升高。氧化铁减少了PVC气相裂解有机挥发分，增加了PVC中的C元素转化为固相C的比例。.电阻炉673K的脱氯实验结果显示在相同的质量配比条件下Fe3O4+PVC混合物的脱氯效果优于Fe2O3+PVC混合物。当Fe3O4:PVC质量比为75:25时，可将PVC中97.6%的氯固定于FeCl2中，其余以HCl随气相排出。通过添加SiO2增加PVC裂解产物H2以强化还原性气氛可以提高Fe2O3的脱氯效果。氧化铁的平均粒度0.5微米最佳。未监测出二恶英。.脱氯反应后的固相产物微观组织形貌显示生成的FeCl2主要分布于尚未反应的氧化铁表面，极易通过水浸脱除。.针对水浸脱除FeCl2后的固相残存物进行了高炉喷吹适宜性研究。经添加与残存物等量的聚乙烯塑料后其灰分低于12%，发热值高于29MJ/kg，满足高炉喷吹的要求。.除完成计划外基于研究过程的发现针对脱氯后的固相残存物进行了拓展应用，经再加热至1273K残存物中的C即可完全还原氧化铁，生成的金属铁显示了优异的磁性能，表明塑料还原金属氧化物制备功能性金属材料的可行性，并利用该发现制备了金属镍催化材料。