冷固结球团直接还原技术及其应用

【作者】 黄柱成；

【导师】 邱冠周； 姜涛；

【作者基本信息】 中南大学 ， 钢铁冶金， 2002， 博士

【摘要】 本文采用X射线衍射、电子显微镜、能谱仪和扫描电镜等现代测试分析手段系统地研究了铁精矿冷固结球团煤基直接还原新工艺的基础理论，为冷固结球团直接还原技术的应用提供了理论与实践依据，并将该技术应用于浸锌渣中有价元素的综合回收。 作者运用高分子合成化学、表面化学、催化反应理论等多学科知识，系统研究了铁精矿冷固结球团的制备、冷固结球团的热态性能及直接还原机理。研究表明：F粘结剂具有粘结、催化和还原功能，成功地实现了低温（200℃～250℃）干燥固结替代高温（1200℃～1300℃）氧化固结，省去了一步高温过程：当F用量为1.5％、混合料润磨预处理时间为5min～6min，造球工艺参数：生球水份8.0％～8.5％、成球时间20min，干燥固结：风温200℃～250℃、风速1.2m／s～1.5m／s、时间20min～25min，可获得冷固结球团抗压强度212N／个～248.3N／个、落下强度4.4次／1m～5.8次／1m、耐磨指数-3mm0.8％～1.3％的良好指标。 采用电子显微镜、扫描电镜及X射线衍射分析等测试手段对添加F粘结剂的冷固结球团的热态性能研究表明：在Fe₃O₄还原过程中，既无晶形转变又无晶体的各向异性效应，以至体积还略微收缩（还原膨胀率为-3.24％），且具有孔隙发达、还原性能优良等特性，能快速还原产生金属铁，较好地保证了还原过程强度。当Fe₃O₄还原产生大量FeO时（800℃～900℃），球团强度降到最低，一般为100N／个左右。为了进一步提高冷固结球团在400℃～950℃之间的还原过程中的热态强度，采用有机粘结剂和无机粘结剂复合的制备技术，开发出了新一代复合粘结剂。当F1.3％、A0.86％、膨润土0.7％复合时，获得冷固结球团抗压强度480N／个、落下强度6.6次／1m、耐磨指数-3mm 0.5％，其冷固结球团还原过程最低强度大于200N／个的良好指标。X射线衍射分析表明，复合粘结剂在冷固结球团还原过程中，Fe₃O₄还原生成的FeO的面网间距d值增大，促进了铁氧化物的还原，有效提高了冷固结球团的热态强度。 冷固结球团直接还原机理研究表明：冷固结球团孔隙率高，含有多功能复合粘结剂，所以冷固结球团以体积反应模型进行还原反应，当温度低于800℃时，还原反应由界面化学反应控制，温度高于900℃时，为扩散控制，当温度在800℃～900℃之间为混合控制。 应用铁精矿冷固结球团直接还原的基本原理，开发了浸锌渣冷固结成型直接还原综合回收有价元素的新工艺。浸锌渣通过成型、固结、还原焙烧、磁选，高效地实现了锌、铁、镓、锗和银的富集回收。浸锌渣采用压团成型方法，当C-5粘结剂用量为博士学位论文冷固结球团直接还原技术及其应用5%、成型压力为255 x 105Pa、成型水分为17.5%时，冷固团块抗压强度和落下强度分别为542 x 105Pa和19.2次/1m，其还原过程热态强度最低值在35xlo5Pa以上，保证了还原过程顺利进行。 X射线衍射分析表明，在900℃下还原20min，形成的主要矿物为FeO、ZnS、znZSio4、zns（六方）、ZnO、p一znZsio4等，在还原过程中生成了铁氧化物、硅酸盐矿物等粘结相，保证了良好的热态强度。在1000℃下，随着还原时间的延长，其锌的挥发量增加，铁的氧化物被还原，并形成金属铁。由于金属铁的产生，使团块的热态强度得到了进一步提高。 浸锌渣冷固结团块采用还原焙烧一磁选新工艺，当浸锌渣含Ga527沙、Ge305沙、Ag5OS幼，恒温还原温度为1 100℃、还原时间为1 50min时，还原焙烧渣中铁的金属化率为95.10%、稼的回收率89.10%、锌的挥发率98.42%，还原焙烧渣经过破碎、磨矿、磁选分离获得的磁性产物中含Fe 90.16%、Ga和Ge的质量浓度为21649/t和1410s/t、Fe、Ga和Ge的回收率分别为87.78%、92.42%和99.08%，磁选尾矿中含Ag 1403沙，总的银回收率达85.85%。因此，新工艺有效地实现了锌、铁、嫁、锗和银等的综合回收利用。 采用电子显微镜、能谱仪和扫描电镜等分析手段对还原焙烧渣中金属的富集行为进行了研究。结果表明:还原焙烧渣中金属铁是稼、锗的主要载体矿物相;稼、锗具有明显的亲铁特性;稼、锗在金属铁中的富集是实现浸锌渣在还原焙烧分选过程中高效分离的基础。更多还原

【Abstract】 The fundamental theories on cold-bonded pellet coal-based direct reduction have been studied systematically by using XRD, SEM, electron microscopy, energy spectrograph ect,which offer a great progress for application of cold-bonded pellet direct reduction. Furthermore, the recovery of value elements from zinc-leaching residue has been performed successfully with this technique.The systematical investigation on ferrous concentrate cold-bonded pellet preparation, heat properties and direct-reduction mechanism has been carried out according to the principles of high-molecular compound chemistry, surface chemistry, catalytic theory etc. The results show: the binder F with function of adhesion,catalyst and reduction brings successfully out the replacement of high-temperature oxide bond (1200#~1300#) by low-temperature bond (200#~250#) and cuts high-temperature process through. The strength of cold-bonded pellet of impact strength 212N~248.3N, drop strength 4.4 times/lm~5.8 times/lm every pellet, abrasion strength(-3mm) 0.8%~1.3% can be obtained under conditions of 1.5% F , 5min~6min mixture damp grinding pretreatment, the moisture of balling 8.0%~8.5% and balling time 20min , bond temperature 200#~250#,wind current rate 1.2m/s~1.5m/s, bond time 20min~25min.The heat properties of cold-bonded pellet with F binder have been studied by using electron microscopy, SEM and XRD . The results show: there is no crystal transformation or anisotropy during the reduction of magnetite. What’s more, the volume contracts (reducing swelling ratio is -3.24%).The cold-bonded pellet with porous, good reducing properties and quick formation of ferrum has good heat strength in reducing process.But when a large number of ferrous oxides appear (800#~900#), of pellet strength reduces. In order to improve heat strength of cold-bonded pellet between 400# and 950# during reducing course, a new complex binder has been developed through composition of organic binder and inorganic binder. When compound condition is : 1.5%F, 0.86%A, 0.7% bentonite, the strength of cold-bonded pellet as follows: impact strength 480N, drop strength 6.6 times/lm ,abrasion strength(-3mm) 0.5%, the lowest strength during direct reduction course surpasses 200N. XRD results show: the complex binder increases d (interplanar spacing), accelerates the reduction of ferrous oxide and raises heat strength of cold-bonded pellet effectively.The study of cold-bonded pellet direct reduction mechanism shows: owing to high void ratio, with composite binder, cold-bonded pellet reducing reaction as volume reaction model. Under 800’C,the reaction is controlled by surface chemistry reaction. Above 900, by diffusion. Between 800~900,by mixture control.The enrichment and recovery of Zn, Fe, Ga, Ge, Ag have been realized by cold-bonded briquette pellet direct reduction technique from Zinc-leaching residues. The strength of cold-bonded pellet is as follows: impact strength 54.2 X 105Pa ,drop strength 19.2 times /1m, the lowest heat strength is above 35 X 105Pa during reducing course under conditions of C-5 binder 5%, pressure 255 X 105Pa and moisture 17.5%. The XRD results show that the main minerals such as FeO, ZnS, Zn2SiO4, ZnS (hexahedron), ZnO and P -Zn2SiO4 have been formed when pellets are reduced 20 min at 900 During reduction the formation of iron oxides and silicate sustains good heat strength. With reduction time prolonging at 1000, the volatilization of zinc increases, the iron oxide is reduced and metallic iron forms and the heat strength of pellet is improved obviously because of the formation of metallic iron.The new process of reducing roasting and magnetic separation has been applied to treat zinc-leaching residues bearing Fe 21.18%, Zn 18.6%, Ga 527g/t, Ge 305g/t, Ag 508g/t .The metallization of iron is 95.10%, recovery of Ga is 89.1% and volatilization of Zn is 98.42% when reduction time is ISOmin at 1100. After crush, grind and separation of the reducing roasting residues, the obtained magnetic product has Fe90.16%, Ga 2164g/t and Ge 1410g/t, the recovery of Fe, G更多还原