【作者】 高国龙；

【导师】 李登新；

【作者基本信息】 东华大学 ， 环境工程， 2009， 博士

【摘要】 随着世界上易选冶的黄金矿石资源日益枯竭,开发利用难选冶金精矿或尾渣,特别是含高硫、高砷的难选冶金精矿或尾渣是一大趋势。难选冶金精矿在氰化提金之前一般都需要预处理,从而提高金的回收率。预处理难选冶金精矿的工艺主要包括氧化焙烧、加压氧化和细菌氧化。焙烧氧化法产生废气,污染环境;加压氧化法生产操作和设备维护均要求很高的技术水平;细菌氧化法反应时间比较长,对砷的含量有一定的限制;用硝酸预氧化金精矿可以显著降低反应温度和压力,使硫化矿物能在较低温度和压力下快速氧化分解,提高金的浸出率。用硝酸预氧化金精矿现主要有三种工艺:NlTROX工艺、ARSENO工艺和COAL法。与高压氧化法相比,ARSENO工艺和COAL法压力降低了很多,但仍然需要2-7个大气压的压力;NITROX法中氮氧化物回收系统复杂。针对以上问题,结合三相循环流化床的特点,本文提出了三相流化床中NO_X循环催化氧化高硫高砷金精矿和尾渣工艺,实现在常压下可连续、NO_X易回用、回用率较高和回收系统简单的地预处理难选金精矿或尾渣,以期望低成本、低能耗、低投资和最大化地综合利用该类难选冶资源,消除其对环境的污染,达到清洁生产目的。本文首先借助XRD、MLA（矿物解离度分析）、线扫描、面扫描和氰化等测试手段表征所采用的高硫高砷难选冶金精矿和尾渣,表明高硫高砷金精矿属于难选冶一类,金以超显微金的形式存在载金矿物成分中,必须氧化预处理后提金。其次从硝酸分子和硝酸根的结构、硝酸的电极电势和NO₂的催化作用等三方面分析了硝酸的氧化性。然后从化学反应的反应热、焓和吉布斯自由能等角度对硝酸催化氧化高硫高砷难选冶金精矿和尾渣进行了热力学分析,从理论上说明了采用硝酸氧化高硫高砷金精矿和尾渣是可行的。在上述理论的指导下,本文进行了间歇式反应器中HNO₃直接氧化高硫高砷金精矿、三相循环流化床中流体力学特性、三相循环流化床中硝酸直接氧化高硫高砷金精矿和三相循环流化床中NO_X循环氧化高硫高砷金精矿和尾渣等四个方面研究,得出了以下结论:（1）采用高硫高砷金精矿为实验原料,以间歇式反应器中硝酸直接氧化高硫高砷金精矿反应过程中铁的转化率为实验指标,通过正交实验和单因素实验研究,考察了主要的各相关因素对铁转化率的影响。在此基础上研究了间歇反应器中硝酸直接氧化高硫高砷金精矿的反应模型。研究表明:①间歇式反应器中硝酸氧化金精矿的转化率受反应温度、硝酸浓度、金精矿粒径、反应时间、搅拌速度等因素的影响。随着搅拌速度、反应温度及硝酸浓度的增加,转化率均有所提高,而随着金精矿粒径的增加,转化率降低;②间歇式反应器中硝酸直接氧化高硫高砷金精矿反应过程可以用粒径缩小的缩核模型来描述。③在反应温度25-85℃、硝酸初始浓度10～30%,金精矿粒径74～154μm、搅拌速度400-800 rpm的条件下,当硝酸浓度为10%时,活化能为10.70kJ/mol,当硝酸浓度为25%时,活化能为12.25kJ/mol。间歇式反应器中硝酸直接氧化高硫高砷金精矿反应过程属于扩散控制。因此,加速流体湍动,减少液膜厚度是强化该过程的首要措施。（2）分别以空气、水、金精矿为气相、液相和固相,采用理论分析和实验研究的方法,进行了三相循环流化床中流体力学特性研究,考察了气体分布板形式和操作条件对反应器内流动特性的影响,研究表明:①平均气含率随气速的增大呈指数增加;少量固体颗粒的加入,使处于湍动域时的微孔分布板三相循环流化床全床平均气含率增加。②相同操作条件下,微孔气体分布板三相循环流化床中气含率比疏孔气体分布板三相循环流化床气含率大。③在初始阶段,随着气体流速的增加,两点间压降下降。上部压降最大,下部次之,中部最小。随着气体流速进一步增加,压降下降幅度略微降低。④疏孔气体分布板三相循环流化床和微孔气体分布板三相循环流化床内平均气含率的关联式分别为ε_g=0.08U_g^0.86和ε_g=0.12U_g^0.99。（3）采用高硫高砷金精矿为实验原料,以三相循环流化床中硝酸直接氧化高硫高砷金精矿反应过程中铁的转化率为实验指标,通过单因素实验研究,考察了主要的各相关因素对铁转化率的影响。在此基础上研究了三相循环流化床中硝酸直接氧化高硫高砷金精矿的反应模型。研究表明:①在三相循环流化床中硝酸氧化金精矿过程中铁的转化率受气速、硝酸浓度、温度和粒径等因素的影响。随着气速、硝酸浓度及反应温度的增加,转化率均有所提高,而随着金精矿粒径的增加,转化率降低;②三相流化床中硝酸与高硫高砷金精矿反应过程系气液固多相反应,其反应的活化能为43.2KJ/mol,该反应属于化学控制过程；反应模型为1-（1-C_r）^?=5987.325e^-5187.14/Tt,反应速率为（?）。（4）采用高硫高砷金精矿和尾渣为实验原料,以三相循环流化床中NO_X循环催化氧化高硫高砷金精矿和尾渣反应过程中铁的转化率为实验指标,进行了三相循环流化床中NO_X循环催化氧化高硫高砷金精矿和尾渣实验。并借助于XRD、点扫描、线扫描和面扫描等测试手段对深度处理前后的金精矿和尾渣的成分进行分析对比。研究表明:①三相循环流化床中NO_X循环催化氧化高硫高砷金精矿和尾渣反应过程中铁的转化率可高达97.59%,经过深度预处理金精矿后的氧化渣中,Fe的单点分析最高量仅为0.63%,S和As单点含量为0,无论线扫描还是面扫描,As均为0;经过深度预处理尾渣之后的氧化渣中铁、硫的残留量极低,FeS₂和FeAsS等载金矿物基本被氧化完全,从而实现金的解离。②三相循环流化床中催化氧化高硫高砷难选冶金精矿和尾渣得到的氧化渣金的浸出率分别达到了96%和100%（氰化钠用量3000g/t,液固比3:1,粒径-25μm,浸出时间24小时,浸出pH 9-10）,表明三相循环流化床催化氧化技术确实提高了金的浸出率,提高幅度大约一倍。③三相循环流化床NO_X循环催化氧化高硫高砷难选冶金精矿和尾渣技术是可行的,且设备较为简单,操作方便,易于实现,基本无有害物质排放,有利于环保。更多还原

【Abstract】 With the depletion of high-grade ore resources, it is a trend to develop and utilizerefractory gold ore and tailings, especially high-sulfur and high-arsenic goldconcentrate （HGC） and tailings. To achieve a satisfactory recovery, an oxidativepretreatment stage is required before applying any conventional treatment. Refractoryore pretreatment processes mainly include roasting oxidation, pressure oxidation andbacterial oxidation. Roasting oxidation would release SO₂ and As₂O₃ and pollute theenvironment; Pressure oxidation processes require high-pressure and high temperatureequipments. Bio-oxidation process requires long time for pretreatment and is sensitiveto arsenic. Nitric acid oxidation method can significantly reduce the reactiontemperature and pressure. Nitric acid oxidation method can be divided into N1TROXprocess, ARSENO technology and COAL method. Although pressure is lower inARSENO technology and COAL method than in high pressure method, there are still2 to 7 atmospheres of pressure. In N1TROX process, nitrogen oxides recovery systemis complex. Considering the above problems and the characteristics of three-phasecirculated fluidized bed, the process of catalytic oxidation of high-sulfur andhigh-arsenic refractory gold concentrate and tailings in three-phase circulatedfluidized bed was suggested. Therefore the development of a cost-effective, clean,atmospheric pressure, low temperature, NO_X easy reuse and recycling rates arerelatively high pre-treatment methods have become the current needs.In this paper, first of all, Through XRD, MLA （Mineral Analysis dissociation） andpoint scan, line scan and surface scan, it was revealed that the gold concentrate andtailings in this paper is of refractory kind and the gold in HGC and tailings isencapsulated as fine grained particles in the crystal structure of the mineral matrix.Then, nitric acid oxidation ability was analysed from three aspects: the structure of nitrate and nitric acid molecules, the electrode potential of nitric acid, and catalyticaleffect of NO₂. Thermodynamic analysis was conducted from three aspects: chemicalreaction heat, enthalpy and Gibbs free energy. It was found that HGC and tailingswere oxidized by nitric acid is feasible in theory.Under the guidance of the above theories, this paper researched four problems:Direct oxidation of HGC by HNO₃ in the intermittent reactor; Hydrodynamics inthree-phase circulated fluidized; Direct oxidation of HGC by nitric acid in three-phasefluidized bed; NOx circulated catalytic oxidation of HGC and tailings in three-phasecirculating fluidized bed. The conclusions can be drawn as follows:（1） The HGC was used as raw materials. The conversion of iron was made as theindicator. Through orthogonal experiment and single factor experiment, the influencesof main factors on the rate of conversion of iron were conducted. Furthermore, thekinetics of HGC oxidation by dilute nitric acid in batch reactor was investigated.①The effects of particle size （50-335μm）, reaction temperature （25-85℃）, initialacid concentration （10-30%, wt.） and stirring speed （400-800 rpm） on the ironextraction rate （C_r） were determined. It is obvious that C_r increases with the rise ofinitial nitric acid concentration, reaction time and stirring speed, but decreases withthe increase of particle size.②the kinetics of HGC oxidation by dilute nitric acidunder in batch reactor was investigated. The reaction process conforms to shrinkingcore model.③The activation energies were determined to be 10.70 KJ/mol in the10% HNO₃ and 12.25 KJ/mol in the 25% HNO₃. Oxidation kinetics indicates that theprocess of HGC oxidation by dilute nitric acid in batch reactor is diffusion controlled.It is necessary to accelerate fluid turbulence and decreases liquid film.（2） Air, water and HGC were used as gas phase, liquid phase and solid phase,respectively. Through theoretical analysis and experimental study, hydrodynamics inthree-phase circulated fluidized were studied. The effects of gas distribution plate andoperation conditions on the flow Characteristics were conducted.①average gasholdup increased with gas velocity exponentially; liquid circulation velocity increasedwith gas velocity, and gas-liquid mass transfer mainly occurred in the upper tube; average gas holdup increased with amount of solid particles.②Under the sameoperating conditions, gas holdup is higher in the circulating fluidized bed withmicropore gas distribution board than in the circulating fluidized bed with sparse gashole distribution board.③At the initial stage, with the increase in gas flow rate,pressure drop between two points dropped. The pressure drop of upper part is thelargest, the lower part is the second, the central is minimum. With a further increase ingas flow rate, pressure drop slightly decrease.④Under the experimental condition,the correlation of average gas holdup in circulating fluidized bed with sparse poredistribution board and micro-pore distribution board areε_g=0.08U_g^0.86andε_g=0.12U_g^0.99, respectively.（3） The HGC was used as raw materials. The conversion of iron in three-phasecirculated fluidized bed was made as the indicator. Through single factor experiment,the influences of main factors on the rate of conversion of iron were conducted.Furthermore, the kinetics of HGC oxidation by nitric acid in three-phase circulatedfluidized bed was investigated.①In three-phase circulated fluidized bed, theconversion of iron increases with the rise of initial nitric acid concentration, reactiontemperature and air velocity, but decreases with the increase of particle size.②Thereaction process of HGC oxidation by nitric acid in three-phase circulated fluidizedbed conforms to shrinking core model.③The activation energies were determined tobe 43.2KJ/mol. Oxidation kinetics indicates that the reaction process of HGCoxidation by nitric acid in three-phase circulated fluidized bed ischemically-controlled. Reaction model is 1-（1-C_r）^?=5987.325e^-5187.14/Tt andreaction rate is（?）.（4） The HGC and tailings were used as raw materials. The conversion of iron inNOx circulated catalytic oxidation process was made as the indicator. The experimentof NO_X circulated catalytic oxidation of HGC and tailings in three-phase circulatedfluidized bed was conducted. Through XRD, point scan, line scan and surface scan, the effect of NOx circulated catalytic oxidation were studied.①The conversion ofiron in NOx circulated catalytic oxidation process can be as high as 97.59%. Afterdepth pretreatment, the maximum volume Fe of the single-point is only 0.63%; S andAs contents of a single point is 0. Regardless of line or surface scan, As content is 0.Gold minerals can be completely oxidized in NOx cycle three-phase circulatingfluidized bed.②The cyanidation leaching rate of HGC and tailings after depthpre-treatment is 96.38% and 100%, respectively（The amount of sodium cyanide is3000g/t; liquid-solid ratio is 3:1; particle size -25μm; leaching time is 24 h; pH is9-10）, proving that NOx circulated catalytic oxidation process indeed improve the rateof gold leaching.③It is feasible to pretreat HGC and tailings using three-phasecirculating fluidized bed NO_X catalytic oxidation method. The apparatus is simple andis easy to operate. There is no waste and the environment was protected.更多还原