印尼红土矿直接还原磁选制备镍铁研究报告

1、印尼红土矿直接还原-磁选制备镍铁研 究 报 告中南大学烧结球团与直接还原研究所 中国PT.SEBUKU IRON LATERITIC ORE INDONISIA长沙 2012.8项目负责人：姜 涛 李光辉主要参试人员：姜 涛 李光辉 饶明军 史唐明 黄晴晴 智 谦蔡 文 罗 骏 余正伟 庄锦强 游志雄 张吉清 张树辉 雷 婷 张永健 刘明霞 朱根兴 张 峰报告编写：李光辉 饶明军报告审核：姜 涛IntroductionAs a strategic element, nickel have the extremely important position in the national econ

2、omy development. Nickel is mainly used in high temperature alloy、 stainless steel 、electroplating and chemical industry， and the main supply form is electrolytic nickel board, which is very expensive. About two-thirds of nickel used in the production of stainless steel， The cost of the raw materials

3、 takes 70% of nickel austenitic stainless steel production cost.The main products of the nickel ore is thick nickel iron, so using low cost nickel iron materials will lower the costs of stainless steel smelting production dramatically. There is huge reserves of nickel ore all over the wolrd, but dif

4、ferent types and different origin of nickel ore have so much different in mineral composition 、chemical composition、modes of occurrence of Ni and embedded form，and the grade of Ni is low，impurities mineral content is high，which makes the nickel ore is hard to get high efficiency use。In the study, th

5、e direct reduction-magnetic separation process was used to process nickel ore， because of the strong affinity of Ni and Fe, the metallic nickel formed from the reduction process gatherd with the substrate of metallic iron, thus separate from the non magnetic ore through the magnetic separation. In t

6、his study, two types of nickel ore from Indonesia were used, the effect of the additive to the direct reduction-magnetic separation process was studied, and the highly quality nickel iron stainless steel materials was acquired through this process.目 录前 言I目 录II第一章 原料性能及研究方法11.1红土镍矿11.1.1 1#红土镍矿11.1.1

7、 2#红土镍矿41.2还原煤71.3 试验流程及研究方法7第二章 1#红土镍矿直接还原-磁选试验研究102.1 含硫添加剂种类的影响102.2 添加剂T2的影响122.2.1 还原温度的影响122.2.2 还原时间的影响142.2.3 T2用量的影响152.2.4 还原球团冷却方式的影响162.3 还原球团的分选172.3.1 磨矿粒度的影响172.3.2 磁场强度的影响182.3.3 超声波处理的影响19第三章 2#红土镍矿直接还原-磁选试验研究263.1添加剂的选择273.1.1 以产率为指标293.1.2 以回收率为指标303.1.3 以品位为指标333.2 直接还原-磁选工艺研究353

8、.2.1 还原时间的影响363.2.2 还原温度的影响373.2.3 磁场强度的影响383.2.4 磨矿细度的影响393.3 镍铁性能分析403.4 本章小结43第四章 结论46 Chapter 1 Experimental materials and methods1.1 Nickelferrous laterite· Both the laterite used in the study are from indonesia. Before experimenting, the laterite needs to be dried and grind, after grindin

9、g the particle size below -0.074mm should reach 80%.1.1.1 1# Nickelferrous lateriteThe main chemical composition of 1# nickelferrous laterite is shown in table 1-1，the chemical speciation and content of Ni in the laterite are shown in table 1-2. Table 1-1 shows the XRD result of the ore.Table 1-2 sh

10、ows the TG-DSC curve。We can see from table 1-1 that the 1# nickelferrous laterite has a higher content of silicon and magnesium and lower content of iron. From table 1-2, we can see that the nickel exists in iron oxide in form of isomorphism, accounted for 40% of all, the rest nickel exists in silic

11、ate or in form of nickel oxide.Table 1-1 Main chemical composition of laterite/%CompositionTFeNiCoMgOSiO2Al2O3Cr2O3CaOLOIMass fraction/%22.101.900.0513.4026.494.251.682.0413.18*LOI-loss on ignitionTable 1-2 Chemical phases and distribution of nickel in laterite/%speciation of nickelnickel oxidenicke

12、l sulfidenickel in iron oxidenickel in silicatetotalnickel content0.20.021.460.221.90occupation ratio10.531.0576.8411.58100The XRD result(table 1-1) shows that the nickelferrous laterite is mainly composed of lizardite(Mg3Si2(OH)4O5)、goethite(FeO(OH) and a few hematite(Fe2O3).As shown in Fig 1-2, a

13、decalescence peaks appears at 89.39 due to the evaporation of the free water. The decalescence peaks appears at 269.40 is due to the dehydroxylation of goethite. The decalescence peaks appears at 597.89 is due to the removal of the structural water in the lizardite. The exothermic peak appears at 80

14、5.77 is due to the crystallization of amorphous Mg2SiO4 which is generated from the dehydroxylation of lizardite to forsterite.The SEM of the laterite ore is shown in Fig 1-3, we can see from the figure that the nickel do not exists alone, it mainy exists in iron oxide and silicate in form of isomor

15、phism, which replace the elements of Fe and Mg. Together with the EDS result ,we can see that zone 1 is mainy consists of nickel-containing serpentine, zone 2 is mainy consists of silica, zone 3 is mainy consists of lizardite, zone 4 is mainy consists of goethite.The nickel-containing serpentine and

16、 goethite are sporadic distributes embedded in lizardite and goethite.Fig 1-1 X-ray diffraction pattern of the laterite oreFig. 1-2 TG-DSC curves of the laterite ore (a) back scatter image of laterite ore （b）EDX of zone1 （c）EDX of zone2 （d）EDX of zone3 （e）back scatter image of laterite ore （f）EDX of

17、 zone4Fig. 1-3 SEM of the laterite ore1.1.1 2#Nickelferrous lateriteThe main chemical composition of 2# nickelferrous laterite is shown in table 1-3, We can see from table 1-3 that the 1# nickelferrous laterite has a higher content of silicon and magnesium and lower content of iron. From table 1-4,

18、we can see that 66% of the nickel exists in iron oxide and the rest nickel exists in silicate The XRD result(table 1-1) shows that the nickelferrous laterite is mainly composed of lizardite(Mg3Si2(OH)4O5)、goethite(FeO(OH) and a few hematite(Fe2O3).As shown in Fig 1-2, a decalescence peaks appears at

19、 89.39 due to the evaporation of the free water. The decalescence peaks appears at 269.40 is due to the dehydroxylation of goethite. The decalescence peaks appears at 597.89 is due to the removal of the structural water in the lizardite. The exothermic peak appears at 805.77 is due to the crystalliz

20、ation of amorphous Mg2SiO4 which is generated from the dehydroxylation of lizardite to forsterite.Table 1-3 Main chemical composition of laterite/%TFeNiCoMgOSiO2Al2O3MnSPLOI22.061.580.02319.5335.62.530.410.050.00416.1*LOI-loss on ignitionTable 1-4 Chemical phases and distribution of nickel in lateri

21、te/%adsorption nickelnickel sulfidenickel in iron oxidenickel in silicatetotalnickel content0.0250.0641.0750.4161.58occupation ratio1.64.166.028.3100Fig 1-4 X-ray diffraction pattern of the laterite Fig. 1-5 TG-DSC curves of the laterite 1.2 Reduction coalWe choose lignite from indonisia as reducing

22、 agent in this study. The coal should be crushed until the particle size below 5mm reach 90%. The proximate analysis of coal is shown in table 1-6,the reactivity of the coal is shown in table 1-7. From table 1-5 and 1-6,we can see that the fixed carbon of the coal is 52.63%, volatile is 35.15%, ash

23、content is 5.31%, the softening temperature of ash is 1244，which could meet the requirements of the coal used in direct reduction.Table 1-5 Proximate analysis result of reduction coalproximate analysis /%Characteristicsof cinderash fusibility /MadAdVdafFCadSTHTFT6.915.3135.1552.631124412701445（Mad：w

24、ater；Ad：dry ash；Vdaf：volatile；FCad：fixed carbon；ST：softening temperature；HT：hemispherical temperature；FT：fluid temperature）Table 1-6 Main chemical composition of coal ash/%TFeSiO2Al2O3CaONa2OMgOS9.9945.4632.163.360.270.630.29Table 1-7 Reactivity of coal temperature /750800850900950100010501100reacti

25、vity /%13.840.567.494.798.399.199.31001.3 Test flow and experimental methods(1) Reduction roasting experimentWeigh the Sulfur-containing additives and nickelferrous laterite (particle size below 0.074mm more than 80% ) according to mass ratio, and then mixed and pelletized. Dry the green ball in the

26、 electric ovens at 110 for two hours。Take 50g of coal in the bottom of the high temperature stainless steel tank (60mm×150mm), and then take about 40g of dried ball in the tank, finally cover the ball with enough coal. After that, put the tank in the vertical resistance furnace and reduct accor

27、ding to the set temperature and time. The inner diameter of the vertical resistance furnace is 70mm（Fig 1-6）. Controlling the temperature with the DWK702 temperature controller to ensure the temperature in the required. Take out the tank after the reducing time reaches a set value. Cool down the tan

28、k in the protection of coal until it reach normal temperature. The test flow is shown in fig 1-7.(a) (b)Fig. 1-6 Schematic diagram of the vertical resistance furnaceLateritePelletizingmagnetic separationCrushing、GrindigGrindingReduction roastingmagnetic materialnonmagneticscoaladditiveFig. 1-7 Flows

29、heet of experiment(2) Grinding-magnetic separation testCrushing the reduced ball to a particle size less than 1mm totally.20 g roasted sample with certain pulp density ground to certain fineness was charged in ball mill（Wuhan Rock Grinding equipment manufacture Co., LTD：RK/ZQM liquid crystal ball mi

30、ll intelligence）, Separation of magnetic minerals from non-magnetic minerals was done using a wet weak magnetic separation（Tianjin mine instrument plant：XCGS-73 magnetic tube） under the certain field intensity. After these, the magnetic products is ferronickel. The products were analyzed by chemical

31、 analysis method or fluorescent analysis.第二章 1#红土镍矿直接还原-磁选试验研究2.1 含硫添加剂种类的影响研究分别添加单质硫(S)、硫酸钙 (CaSO4·2H2O)、硫化钠(NaS2)、磁黄铁矿 (FeS)、T2等含硫添加剂对红土镍矿还原焙烧-分选效果的影响。在还原温度为1100、还原时间为60min、磨矿细度90%小于0.043mm、磁场强度1kGs条件下进行试验，各含硫添加剂添加量为：添加物S含量为4.48%（按质量分数配比分别为：单质硫4.48%、硫酸钙24.08%、硫化钠10.92%、磁黄铁矿12.32%、T220%）。红土镍矿还

32、原焙烧-分选结果如图2-1(a)所示。图2-1(a) 含硫添加剂种类对红土镍矿还原-磁分选影响(含S物质的量相等的含硫添加剂)Fig. 2-1(a) Results of reduction-magnetic separation of laterite with different sulfur bearing additives从图2-1(a)可以看出，不同含硫添加剂强化红土镍矿的还原、磁选效果的程度不同，其中以T2的作用最为显著，这是因为不仅硫化作用对还原、磁选有促进作用，碱金属钠离子对金属氧化物的还原分选也有极大的催化作用，这两种作用结合起来使得红土镍矿还原焙烧-磁选的效果有了显著的提

33、高。相比无添加剂时其他含硫添加剂均降低了磁选产品中铁、镍的回收率，但却提高了镍的品位。同时研究了添加剂质量分数均为20%时含硫添加剂种类对还原焙烧的影响，结果见图2-1(b)。图2-1(b) 含硫添加剂种类对红土镍矿还原-磁分选影响(外配20%含硫添加剂)Fig. 2-1(b) Results of reduction-magnetic separation of laterite with different sulfur bearing additives由图2-1(b)可知，在加入相同质量分数的添加剂时，T2的作用仍最显著。相比不加入添加剂时，添加硫酸钙、硫化钠均对还原焙烧-磁选的效果有

34、改善作用，而单质硫的效果仍不明显。因T2作为红土镍矿的添加剂效果较为明显，采用T2作为主要研究的含硫添加剂并系统研究还原温度、还原时间、磨矿细度、磁场强度、冷却方式对红土镍矿焙烧-磁选的影响。2.2 添加剂T2的影响2.2.1 还原温度的影响对于红土镍矿球团还原焙烧过程而言，温度的升高可以使球团内的低熔点物质熔化形成液相，根据固体扩散理论，当体系中存在液相时，扩散系数将增大，改善传质条件，有利于镍、铁晶粒的长大。无添加剂时，在还原时间为60min、磨矿细度90%小于0.043mm、磁场强度为1kGs条件下进行试验，考查还原温度对红土镍矿还原-磁选效果的影响，结果如图2-2所示。以20%T2为添

35、加剂时考查还原温度对红土镍矿焙烧-磁选效果的影响，结果如图2-3所示。图2-2 无添加剂时还原温度对红土镍矿还原-磁选效果的影响Fig. 2-2 Effects of reducing temperature on magnetic separation of laterite pellets reduced for 60min in the absence of sodium sulfate.图2-3 添加20%T2时还原温度对红土镍矿还原-磁选效果的影响Fig. 2-3 Effects of reducing temperature on magnetic separation of la

36、terite pellets reduced for 60 min in the presence of 20 wt.% sodium sulfate.从图2-2可以看出，无添加剂时还原温度对镍、铁的品位和回收率都有显著的影响。随着还原温度从900上升至1200，镍铁中镍、铁品位连续提高，1200时镍、铁品位分别达到最大值2.68%、73.24%；镍铁中镍、铁回收率的增加十分显著，分别从5.9%和9.8%增加到84.7%和96.8%。在图2-3中，当还原温度从800上升至1100时，镍、铁品位分别从7.08%、69.3%上升至9.48%、79.3%，镍、铁回收率分别从25.81%、19.96%

37、上升至83.01%、56.36%。当温度从1100继续提高到1200时，镍、铁品位和回收率只是略有提高。从减小能耗的角度考虑，推荐适当的温度为1100。对比图2-2及2-3可知，在相同的还原温度下，添加T2后产品的各项指标均优于未添加T2时。在1100、焙烧60min的条件下，相比未加入T2时，加入T2还原的磁选产品中镍品位从2.33%提高至9.48%，镍回收率从56.97%提高至83.02%，铁品位从62.79%提高至79.3%，而铁回收率却从65.76%降低至56.36%。2.2.2 还原时间的影响分别研究了无添加剂和添加20%T2条件下还原时间对红土镍矿焙烧-磁选效果的影响。试验在还原温

38、度为1100、磨矿细度90%小于0.043mm、磁场强度1kGs的条件下进行，结果如图2-4、2-5所示。图2-4 无添加剂时还原时间对红土镍矿还原-磁选效果的影响Fig. 2-4 Effects of reducing time on magnetic separation of laterite pellets reduced at 1100 in the absence of sodium sulfate图2-5 添加20%T2时还原时间对红土镍矿还原-磁选效果的影响Fig. 2-5 Effects of reducing time on magnetic separation of l

39、aterite pellets reduced at 1100 in the presence of 20 wt.% sodium sulfate.可见无论是否加入添加剂，延长还原时间都明显有利于镍、铁回收率的提高。无添加剂时，随着还原时间从30min延长到120分钟，镍铁品位略有提升。加入20%T2作为添加剂、还原时间30min时产品镍品位达到最高峰值，继而随着还原时间的延长，镍品位呈下降的趋势，这是因为铁回收率的提高强化了铁的富集作用从而导致镍品位的降低。综合镍品位及镍回收率考虑，适宜的还原时间为60min。2.2.3 T2用量的影响在还原温度为1100、还原时间为60min、磨矿细度90

40、%小于0.043mm、磁场强度为1kGs的条件下进行试验，不同用量的T2作用下红土镍矿的还原焙烧还原-磁选效果如图2-6所示。无添加剂时所得产品指标并不理想，镍、铁品位分别只有2.33%、62.79%，镍、铁回收率分别只有56.97%和65.75%。随着T2添加量的增加，镍的品位与回收率显著连续提高，从无添加剂到添加20%T2，镍品位从2.33%提高至9.48%，镍回收率从56.97%提高至83.02%。然而随着T2用量的提高，铁的金属化率持续下降，铁品位不断提高，铁回收率呈先升高后下降的趋势，在T2用量5%的时候达到最高值。铁的金属化率随T2用量增加而持续下降表明，T2可以抑制金属铁的生成，

41、从而选择性的富集了镍，除此之外可知，T2的存在强化了镍铁磁选的效果。当T2用量为20%时镍铁产品中镍品位、镍回收率均为最大值，由于继续增加T2用量会使还原球团产生熔融现象，故选取T2用量20%为最优条件。T2添加量/wt%图2-6不同用量T2作用下红土镍矿还原-磁选结果Fig. 2-6 Effects of sodium sulfate dosage on reduction and magnetic separation of laterite pellets reduced at 1100 for 60 min2.2.4 还原球团冷却方式的影响不同的冷却速度会影响镍、铁晶粒结晶程度。试验选

42、择水冷为还原球团进行快速冷却，随炉冷却为还原球团进行慢速冷却。以20%T2为添加剂时，在还原温度1100、还原时间为60min、磨矿细度90%小于0.043mm、磁场强度为1kGs条件下进行试验，考查不同冷却制度对红土镍矿焙烧-磁选效果的影响。采用水冷为刚还原完毕的不锈钢罐进行快速冷却。具体方法为取出不锈钢罐用过量褐煤充分填满钢罐保护还原球团，并将钢罐迅速放入乘有自来水的水桶，球团同钢罐一同快速冷却。随炉冷却的方法为用过量褐煤充分填满不锈钢罐保护还原球团，关闭竖式炉电源让竖式炉自然冷却，起到缓慢冷却的效果。试验结果如图2-7所示。经过水冷的球团磁选后产品的各项指标较室温下自然冷却的结果偏低。不

43、仅镍、铁回收率大幅降低，而且镍品位也有较大程度的降低，这是由于急速的冷却使得球团内部的镍、铁晶粒结晶时间大幅减少，结晶过程迅速结束，结晶程度降低。而随炉冷却后的球团磁选后镍、铁回收率相比室温下自然冷却的结果相对增高，慢速的冷却使得晶粒结晶有了充分的时间，结晶程度较好。产品铁品位略有提高，而镍品位有所降低，原因是产品铁品位及回收率的提高导致相对应的镍品位降低。图2-7冷却制度对红土镍矿还原-磁选效果的影响（添加20%T2）Fig. 2-7 Effects of heattreatingregime on magnetic separation of laterite pellets reduce

44、d at 1100 in the presence of 20 wt.% sodium sulfate.2.3 还原球团的分选2.3.1 磨矿粒度的影响以20%T2为添加剂时，在还原温度1100、还原时间为60min、磁场强度为1kGs条件下进行试验，考查不同磨矿粒度对红土镍矿焙烧-磁选效果的影响，结果如图2-8所示。由图2-8可知，磨矿粒度对磁选产品的镍、铁品位有一定的影响，随着-0.043mm粒级含量的增加，镍、铁品位持续上升，但当-0.043mm粒级含量超过90%后，镍、铁品位不再明显提升。磨矿细度对镍回收率影响甚微，但对铁的回收率有显著影响。随着-0.043mm粒级含量的增加，铁的回收

45、率不断下降，这是因为磨矿细度过小矿粉就会产生泥化现象，有价成分与杂质分开难度增加，减弱了磁选分离的效果，考虑磨矿能耗及磁选效果，磨矿浓度为-0.043mm粒级90%。 图2-8 添加20%T2时磨矿细度对红土镍矿还原-磁选效果的影响Fig. 2-8 Effects of grinding fineness on magnetic separation of laterite pellets reduced at 1100 in the presence of 20 wt.% sodium sulfate.2.3.2 磁场强度的影响以20%T2为添加剂时，在还原温度1100、还原时间为60min

46、、磨矿细度90%小于0.043mm的条件下进行试验，考查不同磁场强度对红土镍矿焙烧-磁选效果的影响，结果如图2-9所示。如图2-9所示，随着磁选的磁场强度的增加，产品的镍、铁品位呈略微下降的趋势，这归因于磁场强度过大，会使其他过多的弱磁性杂质夹杂、包裹在磁性矿物颗粒中间和表面，使得镍、铁品位相对降低。而镍、铁回收率提高的原因是因为随着磁场强度的增强产率提升，从而导致回收率的提升。综合考虑镍品位与回收率，选择磁场强度1KGS为最优条件。图2-9 添加20%T2时磨矿细度对红土镍矿还原-磁选效果的影响Fig. 2-9 Effects of magnetic field intensity on m

47、agnetic separation of laterite pellets reduced at 1100 in the presence of 20 wt.% sodium sulfate.2.3.3 超声波处理的影响在还原球团磨矿过程中，矿物颗粒在磨矿介质的撞击下磁性颗粒会与弱磁性或非磁性杂质不完全分离，而分离出来的这些杂质可能夹杂、包裹在磁性矿物颗粒之间或表面，导致在磁选过程中这些杂质不能完全与磁性颗粒分离。为进一步提高镍铁精矿产品质量，研究超声波处理对磁选效果的影响。添加20%T2作为添加剂，在还原温度为1100、还原时间分别为30min、60min、90min和120min条件下进

48、行还原焙烧-磁选，还原球团破碎至-1mm，磨矿细度90%小于0.043mm、磁场强度为1kGs条件下进行磁选试验，得到镍铁精矿。取部分镍铁精矿在超声清洗器中进行超声波处理，频率40KHZ，处理时间3min，然后进行二次磁选试验，再次得到镍铁产品。比较两次磁选试验得到的镍铁产品中铁、镍的品位和回收率，考查超声波处理对镍铁产品镍、铁品位和回收率的影响，结果分别如图2-10至图2-13所示。图2-10 超声波处理对磁选镍品位的影响Fig. 2-10 Effects of ultrasonication on grade of Ni.图2-11超声波处理对磁选铁品位的影响Fig. 2-11 Effec

49、ts of ultrasonication on grade of Fe.图2-12超声波处理对磁选镍回收率的影响Fig. 2-12 Effects of ultrasonication on recovery of Ni.图2-13超声波处理对磁选铁回收率的影响Fig. 2-13 Effects of ultrasonication on recovery of Fe. 从图2-10、图2-11、图2-12和图2-13可以看出，超声波处理对镍铁产品中镍、铁品位的提高具有比较显著的作用，可以将镍铁产品中铁、镍品位分别最高提升3.8%、7.6%。元素SNaMgSiFeWt/%1.065.8916

50、.5920.4349.65At/%1.219.3624.9126.5532.45图2-14 未进行超声波处理的镍铁扫描电镜能谱图Fig. 2-14 ESEM-EDS analyses of ferronickel was not treated by ultrasonic waves元素ONaMgSiFeWt/%35.204.4616.4421.6317.95At/%51.564.5415.8418.057.53图2-15超声波处理后镍铁扫描电镜能谱图Fig. 2-15 ESEM-EDS analyses of ferronickel treated by ultrasonic waves通过

51、镍铁精矿的环境扫描电镜-能谱分析（图2-14，2-15）可知，还原球团在磨矿的过程中，还原得到的镍铁颗粒具有良好的韧性，在磨矿介质的撞击下变成片状，镍铁颗粒成片状过程中包嵌了一定量的镁硅酸盐等杂质，随后的磁选分离过程不能完全有效分离这部分杂质而使其进入磁性产品中。对磁选得到的镍铁精矿进行超声波处理可以有效的分离这部分杂质避免其再次进入磁性产品中，进而提高了镍铁产品中铁、镍的品位。2.4 本章小结(1) 含S物质的量相等的不同含硫添加剂强化红土镍矿的还原、磁选效果的程度不同，其中以T2的作用最为显著。(2) 还原温度对红土镍矿还原焙烧-磁选试验结果得知，无论是否加入添加剂，还原温度对镍、铁的品位

52、和回收率都有显著的影响。通过研究还原时间对红土镍矿还原焙烧还原-磁选试验所得到镍铁中镍、铁品位及回收率的影响得知，无论是否加入添加剂，延长还原时间都明显有利于镍、铁回收率的提高。(3) 不同用量的T2作用下红土镍矿的还原焙烧还原-磁选表明，不添加T2时所得产品镍、铁品位及回收率都较低。随着T2添加量的增加，镍的品位与回收率显著连续提高。然而随着T2用量的提高，铁的金属化率持续下降，铁品位不断提高，铁回收率呈先升高后下降的趋势，在T2用量5%的时候达到最高值。添加剂T2在还原过程中可以抑制金属铁的生成，从而选择性的富集了镍，同时T2的存在强化了镍铁磁选的效果。(4) 通过研究磨矿细度和磁场强度对

53、红土镍矿还原焙烧还原-磁选试验的影响得知，磨矿细度对磁选产品的镍、铁品位有一定的影响，随着-0.043mm粒级含量的增加，镍、铁品位持续上升，但当-0.043mm粒级含量超过90%后，镍、铁品位不再明显提升。磨矿细度对镍回收率影响甚微，但对铁的回收率有显著影响。(5) 通过研究冷却制度对红土镍矿还原焙烧还原-磁选试验的影响得知，经过水冷的球团磁选后产品的各项指标较室温下自然冷却的结果偏低。镍、铁回收率及镍品位都有较大程度的降低，极快的冷却速度使得球团内部的镍、铁晶粒结晶时间大幅减少，结晶过程迅速结束，结晶程度降低。而随炉冷却后的球团磁选后镍、铁回收率相比室温下自然冷却的结果相对增高，慢速的冷却

54、使得晶粒结晶有了充分的时间，结晶程度较好。(6) 通过研究超声波处理对红土镍矿还原焙烧还原-磁选试验的影响得知，超声波处理对镍铁产品中铁、镍品位和回收率的提高具有比较显著的作用。还原球团在磨矿的过程中在磨矿介质的撞击下变成片状，镍铁颗粒成片状过程中包嵌了一定量的镁硅酸盐等杂质，超声波处理过程可以有效的分离这部分杂质避免其进入磁性产品中，进而提高了镍铁产品中镍、铁的品位。(7) 红土镍矿采用还原焙烧还原-磁选工艺在添加剂（T220%）作用下，可以得到有效的处理。获得的适宜工艺条件为：还原温度1100，还原时间60min，磁场强度1kGs，磨矿细度90%小于0.043mm。上述条件下所得磁性物镍铁

55、中的镍、铁品位分别为9.48%、79.30%；镍、铁回收率分别可达到83.02%、56.36%。第三章 2#红土镍矿直接还原-磁选试验研究2#红土镍矿原料中镍含量较低，仅为1.58%，而铁含量相对较高，为22.06%，由于铁、镍原子半径相近，容易形成固溶体，因此本研究通过对红土镍矿进行直接还原，使还原产生的金属镍以含量相对较高的金属铁为载体得到聚集，从而通过磁选与非磁性脉石矿物分离、得到富集。在还原温度1100、还原时间60min、磨矿细度-0.043mm粒级为92.6%、磁场强度1kGs条件下，红土镍矿直接还原-磁选结果如图3-1所示。由图3-1得出，无添加剂作用下，红土镍矿直接还原-磁选效果不理想，镍、铁品位分别为1.88%、62.72%，镍、铁回收率分别仅为25.9%、21.1%。 图3-1无添加剂红土镍矿直接还原-磁选结果 Fig. 3-1 Results of direct reductio