1.School of Metallurgical Engineering,Xi’an University of Architecture and Technology,Key Laboratory of Green Development and Utilization of Non-ferrous Metal Resources of Shaanxi Province,Xi’an 710055,Shaanxi,China
2.Northwest Nonferrous Geological and Mining Group Co. ,Xi’an 710054,Shaanxi,China
In recent years,the depletion of easily accessible gold resources has necessitated a shift in gold mining towards more challenging deposits.Within China’s gold industrial reserves,carbonaceous gold deposits are estimated to exceed 4 000 metric tons,comprising approximately 8% of the total resource reserves and accounting for over 20% of the currently exploited and proven gold reserves.To address the challenges of gold loss and encapsulation in carbonaceous gold ore,an integrated approach involving roasting,magnetic separation,and leaching of carbonaceous gold concentrate and iron oxide has been proposed.The procedure initially employs a vacuum tube furnace for the roasting pretreatment,followed by the utilization of a digital display manual powder tablet press to form the mixture of Fe2O3 and carbonized gold concentrate into a cake-like structure.Subsequently,a weak magnetic separator is used to isolate the strongly magnetic material from the gold concentrate,resulting in the production of iron concentrate.This study also investigated the primary factors influencing the roasting process and elucidated the reaction mechanisms between carbonaceous minerals and sulfide minerals in carbonaceous gold deposits.The findings indicate that,under the conditions where the mass ratio of carbonaceous gold concentrate to iron oxide is 1∶10,the roasting temperature is maintained at 1 100 ℃,the regrinding fineness ratio of particles smaller than 0.074 mm is approximately 100%,and the magnetic field intensity is set at 0.20 T,the average gold leaching rate achieves 81.60%,while the iron recovery rate reaches 97.27%.During the roasting process,the carbonates and FeS2 present in the carbonaceous gold deposit facilitate the reduction of Fe2O3 to Fe3O4,concurrently,the carbonates are transformed into inorganic carbon and CO2,and the desulfurization of FeS2 results in the formation of FeS and S2.The collaborative roasting pretreatment technology addresses the issue of “gold robbing” by carbonaceous minerals and the encapsulation of gold within sulfide and hematite matrices.This approach offers a novel research perspective for the safe and resource-efficient utilization of cyanide red slag.Furthermore,it establishes a theoretical basis for optimizing and enhancing the integrated technology of collaborative roasting,magnetic separation,and leaching processes applied to carbonaceous gold concentrate and cyanide red slag.
氧化焙烧是处理碳质金矿最广泛的一种方法,该工艺是在温度为700 ℃左右条件下对金矿石进行焙烧,使碳质物氧化分解,从而使包裹金裸露出来,此外由于焙烧过程中CO2的额外排放,导致较大的多孔结构产生,有利于金的浸出(Li et al.,2021;Xiao et al.,2022)。然而,有害废气的排放,通气量的调控,以及矿物过烧或欠烧问题,导致企业后序处理成本较高(方兆珩,2003;Thoms et al.,2016)。氯化焙烧是另一种应用较成熟的预处理方法,该方法利用CaCl2和NaCl等与矿物反应生成相应的金属氯化物,改变金的赋存状态,实现金与其他组分的分离(Wang et al.,2019,2020;Liu et al.,2022),但该方法存在金的挥发损失率相对较高,且需处理有毒气体等缺陷。这两类工艺旨在最大限度地去除碳质物的影响,而未充分考虑到碳质物本身也可作为还原剂参与反应,对伴生的其他有价金属进行回收利用。目前碳质金矿预处理相关研究主要集中在单一矿物的焙烧工艺方面,而对多矿物的协同焙烧处理技术研究仍有所欠缺,因此对这一领域的研究有利于碳质金矿预处理技术的改进和应用。
为了充分利用难选金矿中的碳质物,Wu et al.(2020)将水蒸气与含碳物质反应生成的CO和H2作为软锰矿的还原剂,既实现了对废弃物的资源化利用,同时降低了有害气体的排放(Yang et al.,2019)。然而,该处理技术反应的条件较为严苛,且对设备和能耗的要求相对较高,能否投入大规模工业应用还有待商榷。另一方面,还原焙烧可将赤铁矿转化为磁铁矿,使微细铁颗粒聚集,从而改善分选效果(陈潮方等,2022)。尚德兴等(2011)将焙烧氰化尾渣(主要有效成分为赤铁矿)在800 ℃条件下进行还原焙烧50 min,磁选后得到铁品位为59%的铁精矿,其铁的有效回收率达到80%。但是,该方法需要额外添加质量占比为18%的褐煤作为还原剂,在一定程度上提高了生产工艺的成本。本文基于上述研究结果,在真空条件下,对某碳质金精矿与氧化铁进行了焙烧—磁选—浸出的因素试验研究,并基本确定了该工艺的最佳条件。该技术无需通氧,有效防止了SO2和CO2等污染物的大量排放,同时使有价金属元素Fe得到高效回收,具备污染小、流程短和成本较低的特点,有较好的发展前景。
综合分析,图7(a)与图7(c)的变化趋势有一定的相似性,但二者的失重率差异明显。对于混合矿物,其实际总质量损失率为5.11%,但如果只考虑由碳质金精矿和Fe2O3引起的失重,则混合矿物的理论总质量损失率为4.98%。结合表5和图8,在无氧条件下,主要发生的是碳质物与Fe2O3的反应,生成Fe3O4和Fe等强磁性物质。在高温环境中,黄铁矿热分解的主要产物之一S2为硫的双原子分子蒸气(Zagoruiko et al.,2002;Jackson et al.,2016)。另外,该过程不仅存在黄铁矿和S2(g)与Fe2O3的反应,黄铁矿脱硫产物(如Fe7S8和FeS等)也与Fe2O3发生反应,导致在实际反应过程中,混合矿物的质量进一步降低(Qin et al.,2023)。由表5和图8(b)可以得出,2FeO+SiO2=Fe2SiO4的吉布斯自由能变化在0~1 200 ℃范围内均小于0,说明该反应在焙烧预处理过程始终可自发进行。由于该类物质属于弱磁性矿物,因此磁选方式难以将其与富含金的尾矿有效分离,可能对暴露金产生二次包裹,影响浸出效果(Yin et al.,2014)。此外,混合样品与单样品的失重率差异表明,在焙烧碳质金精矿和Fe2O3时,除了其自身发生热解之外,二者之间还发生了复杂的氧化还原反应,如:3Fe2O3+C=2Fe3O4+CO(g),8Fe2O3+2FeS= 6Fe3O4+S2(g)等,进一步体现了该焙烧预处理工艺的协同作用。
AmankwahR K, PicklesC A,2009.Microwave roasting of a carbonaceous sulphidic gold concentrate[J].Minerals Engineering,22(13):1095-1101.
[2]
ChenChaofang, QiuXianhui, QiuTingsheng,et al,2022.Characteristics and comprehensive utilization of cyanized tailings[J].Nonferrous Metals Science and Engineering,13(4):107-115.
[3]
EspitiaS L M, LapidusG T,2015.Pretreatment of a refractory arsenopyritic gold ore using hydroxyl ion[J].Hydrometallurgy,153:106-113.
[4]
FangZhaoheng,2003.Mineral characteristic and extractive technology of carbonaceous gold ores[J].Gold Science and Technology,11(6):28-35.
[5]
JacksonA J, TianaD, WalshA,2016.A universal chemical potential for sulfur vapours[J].Chemical Science,7(2):1082-1092.
[6]
JiaYujuan, WangXiaojun, ChengWei,et al,2019.Research progress on non-cyanide leaching of refractory gold ores[J].Chinese Journal of Engineering,41(3):307-315.
[7]
LiH, XiaoW, JinJ P,et al,2021.Oxidation roasting of fine-grained carbonaceous gold ore:The effect of aeration rate[J].Minerals,11(6):558.
[8]
LiuS L, FengY L, LiH R,et al,2022.Simultaneous extraction of gold and vanadium from vanadium and carbon-rich refractory gold minerals by chlorination roasting[J].Metallurgical and Materials Transactions B,53(6):3955-3966.
[9]
LiuZhilou, YangTianzu,2014.Treatment status for refractory gold ores[J].Precious Metals,35(1):79-83,89.
[10]
NiuHuiqun, TongLinlin, ZhongShuiping,et al,2019.Reasearch status on carbonaceous matter characteristic and decarbonization of carlin-type gold ore[J].Nonferrous Metals (smelting part),(6):33-39.
[11]
PourdashtM,2018.Study on the Surface Features of Preg-Robbing Carbonaceous Matter During Oxidation Treatment[D].Ontario:The University of Western Ontario.
[12]
QinH, GuoX Y, YuD W,et al,2023.Pyrite as an efficient reductant for magnetization roasting and its efficacy in iron recovery from iron-bearing tailing[J].Separation and Purification Technology,305:122511.
[13]
ShangDexing, ChenFangfang, ZhangYifei,et al,2011.Experimental study on reduction of roasting-magnetic separation [J].Mining and Metallurgy Engineering,31(5):35-38.
[14]
SongYan, YangHongying, TongLinlin,et al,2018.Experimental study on bacterial oxidation-cyanidation of a complex refractory gold mine in Gansu Province[J].Gold Science and Technology,26(2):241-247.
[15]
ThomsK G, ColeA P,2016.Roasting Developments Especially Oxygenated Roasting Science Direct[M].Amsterdam:Elsevier.
[16]
WangH J, FengY L, LiH R,et al,2019.The separation of gold and vanadium in carbonaceous gold ore by one-step roasting method[J].Powder Technology,355:191-200.
[17]
WangH J, FengY L, LiH R,et al,2020.Simultaneous extraction of gold and zinc from refractory carbonaceous gold ore by chlorination roasting process[J].Transactions of Nonferrous Metals Society of China,30(4):1111-1123.
[18]
WuH, FengY L, LiH R,et al,2020.Co-recovery of manganese from pyrolusite and gold from carbonaceous gold ore using fluidized roasting coupling technology [J].Chemical Engineering and Processing Process Intensification,147:107742.
[19]
WuTiaojiao, CaoHuan, NiuFangyin,et al,2021.Study on gold extraction from a carbon-bearing fine-grained refractory gold ore by flotation process[J].Gold Science and Technology,29(5):761-770.
[20]
XiaoH X, JinJ P, HeF Y,et al,2022.Accelerating the decarbonization of carbonaceous gold ore by suspension oxidation roasting towards the improvement of gold leaching efficiency[J].Advanced Powder Technology,33:634-639.
[21]
YangB, HuangD X, LiuD C,et al,2019.Research and industrial application of a vacuum separation technique for recovering valuable metals from copper dross[J].Separation and Purification Technology,236:116309.DOI:10.1016/j.seppur.2019.116309 .
[22]
YangH Y, LiuQ, SongX L,et al,2013.Research status of carbonaceous matter in carbonaceous gold ores and bio-oxidation pretreatment[J].Transactions of Nonferrous Metals Society of China,23(11):3405-3411.
[23]
YinZ L, LuW H, XiaoH,2014.Arsenic removal from copper-silver ore by roasting in vacuum[J].Vacuum,101:350-353.
[24]
ZagoruikoA N, MatrosY S,2002.Mathematical modelling of Claus reactors undergoing sulfur condensation and evaporation[J].Chemical Engineering Journal,87(1):73-88.
[25]
ZhangLiang, SongYonghui, ZhangXinwei,et al,2024.Study on the synergistic roasting and magnetic separation of carbon gold mine and cyanide tailings[J].Gold,45(4):32-39,56.
[26]
ZhangX W, SongY H, YinN,et al,2021.Study on vacuum roasting pretreatment of carbonaceous gold concentrates based on nonoxidation technology[J].Journal of Chemistry,2021:6848020.
[27]
ZhangXingang, ChaofeiLü, JiaJialin,et al,2015.Recovery of Au and Ag from silver slag produced in the treatment of cyanide gold mud[J].Precious Metals,36(3):63-68.
[28]
ZhongMei, GaoShiqiu, ZhangZhikai,et al,2012.Preparation conditions of char via pyrolysis of low-rank particulate coal in oxygen-containing atmosphere[J].The Chinese Journal of Process Engineering,12(2):231-238.
[29]
ZhuJun, LiuSuning,2010.Status and research of leaching technology of gold ore that is difficult to be treated[J].Mining Engineering,8(1):35-37.