极低品位高钙氧化锌矿“冶—选”新技术的基础研究

【作者】 魏志聪；

【导师】 童雄； 张文彬；

【作者基本信息】 昆明理工大学 ， 矿物加工工程， 2011， 博士

【摘要】 随着我国经济和社会的高速发展,对锌金属的需求量快速增长,锌矿资源紧缺的问题日益凸现。到目前为止,每年约有三分之一的锌原料依靠进口。可是,在另一方面,我国储量相对丰富的低品位氧化锌矿资源,却又未能得到合理利用。矿石难于选矿和冶炼的主要原因是品位低、氧化程度深、含泥量大和矿物组成复杂等。大量的这种类型的矿石开采出来只能长期堆存甚至废弃。因此,针对该类资源,研发高效加工新技术,对保障我国锌资源的有效供给,实现锌冶炼产业的可持续发展具有重要意义。为了解决低品位高钙氧化锌矿的有效利用难题,以本文作者的导师—张文彬教授为首的研究团队提出了一个全新的冶-选联合流程,即“氨浸-萃取-电积-浸渣浮选”流程。其主要特色是先氨浸,后浮选。这样,既可以用氨浸的办法解决高钙矿石中难于浮选的氧化锌矿物的回收问题,又可以用浮选的办法解决矿石中难于浸出的硫化锌矿物的回收问题。本论文的研究目的,不是对上述新流程进行全面深入的工艺条件试验,获取最佳技术经济指标,而是着重进行该流程关键步骤的基础理论研究,为该流程提供理论支撑。同时,通过初步的工艺条件试验,证明该流程的主要环节和全流程的可行性。本论文的研究共采用了两个试料,均为低品位高钙氧化锌矿。矿石的主要特点是品位极低(含锌分别为6.5%和7.52%)、钙含量高(CaO22％以上)、含泥量大、铅锌矿物结构复杂和嵌布粒度微细等。在基础理论方面,通过本论文的深入研究,得到了如下主要结果：(1)氧化锌矿氨浸体系的基础理论采用沉淀法揭示了氧化锌矿的溶解度与氨-铵总氮浓度、碳酸氢铵的加入量和溶液的pH的关系。发现稳定的锌氨配位离子析出的pH范围为6.5-11,氨与碳酸氢铵配比组成的复合浸出剂的pH值在10-11之间时,可获得较高的浸出率。试验表明,氨-铵盐体系的浸出效果优于单独使用氨水体系或铵盐浸出体系,因此,选择了氨-碳酸氢铵作为浸出体系；在热力学方面,推导计算了各溶液体系中锌可能存在的物种形式,证明了在Zn(Ⅱ)-NH3-NH4HCO3-H2O体系中锌主要以[Zn(NH3)4]2+形式存在。氨浸动力学研究阐明了搅拌强度、总氨浓度、搅拌时间和反应温度均对锌浸出率有影响,明确了浸出反应符合“未反应核减缩模型”。动力学方程满足1-(1-α)1/3=kt,浸出反应受外扩散控制,反应的表观活化能Ea=6.489KJ/mol。(2)M5640萃取体系基础理论氨浸溶液中锌的萃取是难点,也是国内众多研究尚未很好解决的问题,亦是所提出的整个工艺流程的关键环节。本论文研究结果表明：在M5640萃取体系中,萃合物分子式为ZnR2；有机相中锌的最大负载量与M5640浓度呈线性关系,单位体积浓度(1V/0) M5640在氨-碳酸氢铵体系中锌的饱和容量为0.16g/L；M5640萃取锌过程是一个放热的过程,等压反应热为-5.66J/mol。提高体系温度不利于萃锌,萃取过程适宜在常温条件下进行；锌的萃取平衡等温线表明应采用错流法进行萃取；采用恒界面池法对M5640萃取体系进行定性的动力学分析,初步判定了在恒界面池中萃取反应为化学反应控制类型。(3)氨浸对浸出渣浮选的活化效应研究从氨浸出渣中浮选硫化锌矿物,本论文是首次。发现经过氨浸,渣中的硫化矿物得到了显著的活化,并提出了“溶解活化浮选”的新概念。本论文通过初步条件试验,验证了包括氨浸、萃取-电积、浸渣浮选单元过程以及全流程的技术可行性,即：(1)氨浸过程的可行性通过初步的条件试验及其优化试验,以NH3-NH4HCO3为复合浸出剂,处理极低品位高钙氧化锌矿石,取得了较好的技术指标,验证了氨浸的可行性。证明在Zn(Ⅱ)-NH3-NH4HCO3-H2O体系中,氨及铵盐用量对锌的浸出率均有一定的影响,增大磨矿细度、延长浸出时间、增大液固比、提高反应温度和增大搅拌强度等均可提高锌的浸出率。利用响应曲面法对氨法浸出条件进行初步优化的结果表明,在C(NH3)4.95mol/L,液固比6：1,反应温度323.05K,磨矿细度-74μm占95%,C(NH4HCO3)2.5mol/L,浸出时间2h,搅拌转速400rpm最优条件下,原矿中锌的浸出率达到了83.07%。(2)萃取-电积的可行性本文研究证明,用醛肟类萃取剂M5640可以从氧化锌矿氨浸液中有效萃取锌。该萃取技术已经获的国家发明专利授权。在M5640萃取体系中,萃取剂浓度、溶液的pH值、总氨浓度等是锌萃取的主要影响因素。对萃取和反萃进行的初步条件试验表明,对含锌9.72g/L、pH=9.71的氨浸出液,其最佳萃取条件为：有机相中萃取剂浓度为35%,相比(O/A)2：1,萃取时间3min,单级萃取得到锌的萃取率为65.18%；反萃的最佳条件为：硫酸浓度40g/L,相比1：1,3min时锌的反萃率可达100%。利用错流萃取流程研究了锌的富集过程。研究表明,在萃取剂浓度为35%,相比为2：1,萃取原液锌浓度为9.57g/L,pH=9.56,萃取时间3min；洗涤剂为去离子水,pH=1.3～1.5,相比1：1,洗涤时间3min；反萃相比为1：1,硫酸浓度为150g/L,反萃为时间3min的条件下进行七段错流萃取-洗涤-反萃富锌试验,反萃液锌含量可达55.84g/L,达到了电积锌液质量要求。锌的电解沉积方面,由于其是成熟工艺,论文仅考查了有机物对电积的影响。研究发现,电积前须用15gm的活性炭脱除反萃液夹带的有机物。(3)浸渣浮选的可行性通过初步的锌-铅混合浮选试验表明,在相同流程和相同条件下,与原矿相比,浸渣中的硫化矿物,表现出了良好的浮游性能。仅通过3min的浮选,铅和锌矿物的作业回收率分别达到49.34%和57.03%；氨的“溶解活化效应”明显,混选粗精矿中硫化锌矿物的相回收率达到了76.5%。(4)全流程的可行性在联合流程的主要关键环节的可行性都得到验证的基础上,全流程验的可行性也得到了验证。整体技术已申报了国家发明专利,并已进入实审阶段。其主要优势在于,既能充分回收氧化锌矿物,又能充分回收硫化锌矿物,同时也排除了钙对湿法冶金过程的影响。更多还原

【Abstract】 The shortage of zinc supply in china is becoming a serious problem with the increasingly rising demand for zinc metal. In recent years, one third of zinc supply per year has to be imported from abroad. Although the zinc oxide ore resources are relatively abundant and available in many mines in China, their low quality for processing, such as low grade, high oxidation degree, high content of slime and complex mineral composition, prevent them from being economically and effectively beneficiated and smelted, leading the mined ores always to be only stacked and even discarde as wastes. Thus, it is quite urgent to develop a new technology to treat and use this kind of zinc reserves, supporting a sustainable development of china’s zinc industry.In this thesis, a newly developed combined flowsheet,"ammonia leaching-extraction-electrolytic deposition-leaching residue flotation (LEEF Process)", for treating extremely low-grade zinc oxide ores with high content of calcium was studied. The main characteristics of the ores studied mainly include low zinc grade (<8%zinc), high content of calcium and (CaO:>22%), high content of slime, complex ore structure and fine dissemination of the minerals.In this study, the basic theory aspects of the key steps of the flowsheet are investigated as emphases, and feasibilities of individual unit operations and the whole flowsheet of the LEEF Process has been confermed by primary condition tests. The main conclusions can be summarized as follows.(1) Basic theory of the ammonia leaching system of the zinc oxide oresThe solubility of zinc oxide ores is dependent on total nitrogen (ammonia-ammonium) concentration, dosage of ammonium hydrogen carbonate and pH values of the solution. The pH range is varied from6.5to11according to stable precipitation of coordination ions formed by zinc and ammonia. Higher leaching rates can be reached at pH values of10to11of the leaching solution.The results of comparison experiments show that the leaching efficiency for an ammonia-ammonium complex system is superior to that for an ammonia water-only or ammonium-only system. So, an ammonia-ammonium system was adopted as the leaching system for the leaching tests. The possible existence forms of zinc of various solution systems were determined by thermodynamic calculation. The results indicate that zinc in Zn(II)-NH3-NH4HCO3-H2O system is mainly in the form of [Zn(NH3)4]2+.Kinetics study of the ammonia leaching process is affected by stirring intensity, the total ammonia concentration, stirring time and reaction temperature. The leaching process follows a shrinking unreacted core model, which can be described by the kinetic equation, i.e.1-(1-α)1/3=k·t. The leaching process is controlled by the external diffusion. The apparent activation energy of the leaching reaction is6.489KJ/mol.(2) Basic theory of M5640extraction systemThe extraction of zinc is the key procedure in the process. The basic theory of zinc ammonia solution extraction was studied. The results obtained show that the chemical formula of extraction complex can be expressed as ZnR2. A linear relation is found between the maximum capacity of zinc presented in organic phase and M5640concentration. The saturated capacity of zinc in NH3-NH4HCO3system containing1V/O M5640is determined as0.16g/L. The process of zinc extracted by M5640is exothermic and the isobaric enthalpy is equal to-5.66J/mol. Thus the extraction process should be better operated at normal temperature since increasing temperatures are unfavourable to zinc extraction. The equilibria isotherm of zinc extraction shows that the extraction process should adopt cross flow. Kinetics analysis of M5640extraction system has carried out, applying the method of invariable interface. The extraction process in an invariable interface pool has been preliminarily categorized into chemical reaction control.(3) Activating effect of ammonia leaching on leaching residue flotationFor the first time, the effect of ammonia leaching on the residue flotaion was investigated. It has been discovered that the floatability of zinc and lead sulphide minerals remained in the residues have been apparently improved after being leached. The phenomena is referred to as "dissolution activation".In order to prove the feasibilityes of the individual steps of the process, including the ammonia leaching, the extraction-electrowinning, the leaching residue flotation, and the feasibility of the whole flowsheet, primary condition tests are also carried out, and the main conclusions can be drawn as follows: (1) The feasibility of ammonia leachingA complex agent of NH3-NH4HCO3was selected as leacing agent. The leaching performance is determined through preliminary tests and optimization tests, and the feasibility of ammonia leaching is confirmed.The leaching efficiency of zinc is dependent on the dosages of ammonia and ammonium for the Zn(Ⅱ)-NH3-NH4HCO3-H2O system. Increasing grinding fineness of the roe, extended leaching time, increasing reaction temperature and stirring speed can enhance the leaching efficiency of zinc.In order to supply reference data for technology tests in future, response surface design method was adopted to study the parameters of the zinc oxide ore ammonia leaching. The leaching efficiency of zinc is about83.07%under the optimized conditions, i.e. C(NH3) of4.95mol/L, liquid-solid ratio of6:1, reaction temperature of323.05K, grinding fineness of74μm accounting for95%, C(NH4HCO3) of2.5mol/L, leaching time of2h and stirring speed of400rpm.(2) The feasibility of extraction-electrowinningIt has been proved that zinc can be extracted from ammonia leaching solution by aldehyde oxime extracting agent (M5640). The feasibility of the extraction technology has been confirmed and has been patented in China.The extractant, pH value of solution and total ammonia concentration are the dominant factors for the extraction operation. The extraction and strpping tests were carried out. The experimental results show that for the ammonia leaching solution with zinc concentration of9.72g/L and pH of9.71, the optimal extraction parameters are extractant concentration of35%in organic phase, phase ratio (O/A) of2:1, extraction time of3min. The zinc concentration through a single stage extraction is65.18%. The optimal parameters for stripping are:sulfuric acid concentration of40g/L, phase ratio (O/A) of1:1. The efficiency of strippng during three minutes can reach100%.The zinc enrichment process by cross-flow extrctions was also studied. The results indicate that under the conditions of extractant concentration of35%, phase ratio of2:1, zinc concentration in feeding solution of9.57g/L, pH of9.56, extraction time of3min, deionized water used as scrubbing, pH of1.3～1.5, phase ratio of1:1, scrubbing time of3min, stripping phase ratio of1:1and sulfuric acid concentration of150g/L, stripping time of3min, the zinc concentration presented in stripping solution can reach55.84g/L, and thus meeting the demand for zinc electrowinning after going through seven stages of cross-flow extraction-scrubbing-stripping.With regard to the developed electrowinning, the effect of organic matters on electrowinning was studied. The results show that the organic matters should be reduced to a certain degree by using15g/L activated carbon before the electrowinning process.(3) The feasibility of leaching residue flotationThe feasibility of leaching residue flotation was also demonstrated by primary experiments.The results of zinc-lead bulk flotation tests indicate that the leaching residue exhibits a much better floatability. The recovery of the ammonia leached lead and zinc minerals are49.34%and57.03%, respectively. The recovery of zinc reported in the bulk concentrate from the rough concentrate can reach as haigh as76.65%. A new concept of "dissolution activation" was put forward and a patent has been applied for.(4) The feasibility of the whole flowsheetUsing the LEEF Process, both the zinc oxide minerals and zinc sulfide minerals can be fully recovered due to the advantages of ammonia leaching and flotation. The feasibility of the whole flowsheet has been experimentally demonstrated,and a patent of the LEEF Process has also been applied for.更多还原