CAS OpenIR
含金硫酸烧渣高温氯化提金的研究
丁剑
Subtype博士
Thesis Advisor叶树峰
2017-01
Degree Grantor中国科学院研究生院
Degree Name博士
Degree Discipline环境工程
Keyword含金硫酸烧渣,提金,高温氯化,Cacl2,反应器
Abstract

我国每年产出800万吨以上的含金硫酸烧渣,其中高达22.8t的金没有得到回收,造成了金资源的巨大浪费。含金硫酸烧渣中的金多被包裹,采用常规的湿法提金技术难以获得满意的金回收率。高温氯化法是一种对原料适应性强的火法分离技术,用于含金硫酸烧渣提金时具有分离彻底的优点。然而,应用传统的高温氯化工艺进行氯化时存在一系列的问题:焙烧过程中粉化、结瘤、结圈严重,严重影响作业率;加热制度无法满足工艺要求,Au的挥发率低;内衬材料常发生腐蚀和粘接。这就对氯化工艺及氯化反应器提出新的更高的要求。本文以两种典型的含金硫酸烧渣为研究对象,进行了高温氯化提金的基础和应用研究。通过对CaCl2作氯化剂时,高温氯化提金机理和Au挥发行为以及氯化反应过程中球团性能变化的研究,确定了适宜的工艺条件,利用模拟计算进行了高温氯化反应器的结构设计,并通过实验选择了合适的高温氯化反应器内衬材料。在扩大试验过程中对实验以及模拟计算的结果进行了验证。以扩大试验为基础,进行了工业化设计。研究得到的主要结论如下:Au-CaCl2体系高温氯化挥发机理的研究结果表明:只有当载金矿物如SiO2、FeS2存在时固态CaCl2才能将Au氯化。当加热温度超过CaCl2熔点时,CaCl2会部分气化,气态CaCl2具有较强的化学反应活性,可以与O2或H2O反应生成Cl2/HCl或直接将Au氯化。SiO2是对Au高温氯化影响最大的载金矿物,其与CaCl2的反应起始温度为578~604℃,该反应在700℃存在转折点。含金硫酸烧渣-CaCl2球团焙烧时,Au的起始挥发温度在不含水、含水空气气氛下分别为350℃和750℃,Cl的起始挥发温度分别为350℃和250℃,因此生球烘干温度需低于250℃。球团焙烧温度需在1100℃时Au的挥发率达到最大值。升温时间过长会降低有价金属元素的挥发率,增加CaCl2的添加量或添加CaCO3可缓解这一效应。因此,短升温时间、高CaCl2添加量以及某些添加剂如CaCO3的加入可促进和保证Au的挥发。含金硫酸烧渣氯化球团性能研究表明:可通过磨矿并添加复合粘结剂的方法提高生球和烘干球的质量。在氯化球团的加热过程中,焙烧球团的强度从400℃开始先降低后升高,最低强度不到烘干球团强度的10%,这一现象是高温氯化时球团粉化的主要原因。提高烘干球的强度、适当降低CaCl2的配比可以提高球团中温强度。高温焙烧时,适当的CaCl2添加量和Fe3O4的存在有助于球团形成Ca-Fe-Si系液相,填充孔隙,提高球团高温焙烧后的强度。CaCl2添加量超过6wt%时产生更多的孔隙,降低球团的强度。通过模拟计算进行了含金硫酸烧渣高温氯化反应器的设计,结果表明:为保证元素的挥发率和球团的强度,存在最优的竖炉的长宽比和高度修正系数最优值0.95和1.75,对应最优操作点的高温气体利用率最高。探讨了炉料和Cl2两种腐蚀介质对Al-Si系耐火砖的作用,结果表明:以SiO2或莫来石形式存在的硅都可与原料发生作用,莫来石会在1250℃时与原料中的液相(主要为铁酸钙)反应生成Ca-Fe-Si-Al-O四元氧化物,造成原料与耐火材料之间的粘接。体系中α-Al2O3性质较为稳定,仅在高温下发生与Fe2O3之间的固溶。因此,低硅高铝的耐火材料更适合用作高温氯化反应器的内衬。根据实验研究结果,设计了含金硫酸烧渣高温氯化提金反应器,并进行了规模为2万吨/年(无锡)的一系列扩大试验。扩大试验得到了理想的结果:烘干球团和焙烧球团的粉化率低;焙烧球的性质稳定,平均抗压强度达到了炼铁用氧化球团的要求;Au、Ag的挥发率分别为88%、66%;选用的低硅高铝耐火砖长期使用未发生腐蚀和粘接。扩大试验为工业化推广提供了技术支撑和保障。在实验室研究和无锡2万吨/年扩大试验的基础上,在山东泰安建立了15万吨/年规模的含金硫酸烧渣高温氯化提金示范工程,可实现无废水和废渣排放,Au回收率高,预计可实现可观的经济、环境和社会效益。;More than 8 000 000 tons of gold-bearing pyrite cinder is produced each year in China, and 22.8 tons of gold in such pyrite cinder could not be recovered, resulting in the huge waste of gold resources. Gold recovery rate is not satisfactory when such pyrite cinder is dealt with common hydrometallurgical methods because the gold is commonly wrapped. High-temperature chloridizing method has strong adaptability to raw materials. It could be applied to the extraction of gold from gold-bearing pyrite cinder due to its high separation efficiency. However, there are a series of problems for the application of conventional high-temperature chlorination process. The pulverization, scaffolding and ringing during roasting could affect the working rate. Heating procedure could not meet the technological requirements of process. Gold volatilization rate, the corrosion and adhesion of refractory is not satisfying. Higher demands on the chlorination process and chlorination reactor are drawn.Two typical gold-bearing pyrite cinders are selected as the research materials in the present paper to carry on the fundamental and applied research of the extraction of gold by high-temperature chlorination method. Optimal operating conditions are determined through the researches on the reaction mechanisms and gold chloridizing volatilization behaviour when CaCl2 is used as the chlorinating agent, and the changes of pellet properties. The structural design of high-temperature chlorinationreactor is done by simulating computation. And appropriate refractory is selected by experiments. The experimental and computation results are verified by expanding test. Industrialization design is carried out based on the results of expanding test. The following conclusions are drawn.Research on the mechanism of the high-temperature chlorination-volatilization process for Au-CaCl2 system was carried out. The results show that Au could be chlorinated by solid CaCl2 only in the presence of gold-carrying minerals such as SiO2 or FeS2. Part of CaCl2 evaporates at temperature above liquidus. Gaseous CaCl2 has stronger chemical activity and can react with O2/H2O to form Cl2/HCl or chlorinate Au directly. SiO2 is the gold-carrying mineral that has the most impact on the high-temperature chlorination of Au. The reaction between SiO2 and CaCl2 starts at 578-604℃, and the reaction has a turning point at 700℃. Au volatilization start temperatures are 350℃ and 750℃ when gold-bearing pyrite cinder and CaCl2 pellets roasted in dry and humid air, respectively. Au volatilization rate reaches the maximum value when the heating temperature is 1100℃. The element volatilization rates become smaller if the heating up time is longer. More CaCl2 addition or the addition of CaCO3 could reduce the impact of heating up time on the volatilization rate. Therefore, a satisfying gold volatilization rate could be ensured with short heating up time, large CaCl2 adding amount and some addition agents like CaCO3.The research on the chlorination pellets made from gold-bearing pyrite cinder shows that grinding and adding organic or inorganic binders could ensure the quality of green ball and dry pellets. The strength of roasted pellets gradually decreases to less than 10% of that of dried pellets when temperature is higher than 400°C during heating. The low mid-temperature strength is the main reason of pulverization of pellets during chlorination-volatilization process. Less addition of CaCl2 and improvement of the strength of dry pellets could increase the mid-temperature strength. An appropriate CaCl2 dosage and the existence of Fe3O4 are helpful for the forming of Ca-Fe-Si systematic liquid slag, which could fill the interstices between particles and increase the strength of pellets roasted at high temperature. However, too much more CaCl2 (>6wt%) could generate much more interstices and decrease the pellet strength.The structural design of high-temperature chlorination reactor is done by simulating computation. And the results show that there are optimal values for length-width ratio and height of shaft furnace, which are 0.95 and 1.75 respectively, to ensure the elemental volatilization rates and strength of roasted pellets. The usage rates of high temperature gas for different structures corresponding to the optimal values are the highest. The effects of furnace burden and Cl2 on Al-Si systematic refractory are investigated. The results show that silicon in monomer silica and mullite could react with furnace burden. Ca-Fe-Si-Al-O systematic calcium ferrite is generated and leads to the adhesion between furnace burden and refractory during the chlorination process. α-Al2O3 has a stronger stability, and could react with iron oxides to generate solid solutions only when the temperature is high. Therefore, refractory with low Si content and high Al content is recommended for lining of high-temperature chlorination reactor.Based on the results of experimental research, high-temperature chlorination reactor for the recovery of Au from gold-bearing pyrite cinder, and expansion test with a production capacity of 20 thousand tons each year was conducted in Wuxi city. Ideal results were obtained. The results show that the pulverization ratio of dried pellets and roasted pellets are smaller. The quality of the roasted pellets is stable, and the mean compressive strength of roasted pellets could meet the technical requirements of oxidized pellets. The chlorination rates are 88% and 66% for Au and Ag respectively. No sign of corrosion and adhesion was found after long term use of refractory with low Si content and high Al content. Expansion test offer a technological support and guarantee to the industrialization. Based on the laboratory investigation and expansion test (20 000 t/a in Wuxi), demonstration project of high-temperature chlorination process for the recovery of Au from gold-bearing pyrite cinder were built (150 000 t/a in Taian Shandong). No waste water and residue are discharged and high recovery of gold is obtained in the project. Considerable economical, environmental and social benefits are predicted. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/26827
Collection中国科学院过程工程研究所
研究所(批量导入)
Recommended Citation
GB/T 7714
丁剑. 含金硫酸烧渣高温氯化提金的研究[D]. 中国科学院研究生院,2017.
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