硫铁矿烧渣脱硫脱砷的研究

【作者】 李亚军；

【导师】 苏毅；

【作者基本信息】 昆明理工大学 ， 化学工程， 2009， 硕士

【摘要】 硫铁矿烧渣是化工厂在以硫铁矿为原料煅烧生产硫酸时排出的废渣,其主要成份为铁,另外还含有硅、钙、镁、硫、砷、铜和银等其它元素,主要矿物为赤铁矿、磁铁矿、石英、硬石膏等。我国硫铁矿烧渣年排放量为1000～1500万吨左右。目前硫铁矿烧渣大都采用堆存或者填埋处理,不仅占用大量的土地,工厂还需支付土地征用费、运费、填埋费等,而且还会对大气、水体、土壤等造成环境污染。同时硫铁矿烧渣中富含铁元素,大约占40%～60%,同时还含有少量的Cu、Ag、Au等有价值的元素,是一种宝贵的二次资源,所以充分利用硫铁矿烧渣不仅可消除其对环境的污染,还会变废为宝,创造一定的经济效益以及社会效益。硫铁矿烧渣的综合利用已经受到各国的高度重视,而且很多发达国家对硫铁矿烧渣的综合利用研究已经进行了多年,虽然我国从70年代就开始对硫铁矿烧渣的综合利用进行了研究,由于我国硫铁矿烧渣质量差、技术水平低、经济落后等一系列因素,导致烧渣利用率很低。与国外一些国家相比仍有很大差距,我国硫铁矿烧渣的利用还存在着很多问题,其中最主要的是不能对烧渣中的杂质进行有效的处理,特别是砷元素和硫元素的存在对于烧渣综合利用(例如作为炼铁原料)所带来的危害。本论文采用硫酸溶液处理硫铁矿烧渣,可达到脱砷、部分脱硫的目的,同时还可使渣中的铁品位提高。研究表明采用硫酸溶液处理硫铁矿烧渣,烧渣经硫酸溶液处理后,As含量可降到0.036%,去除率高达98.7%,S含量降至0.319%,同时Fe品位可达到62.56%,经处理后的烧渣砷、铁含量均达到炼铁原料的质量要求。为探索试验的最佳工艺条件,设计进行了条件试验包括硫酸浓度的影响试验、温度的影响试验、矿浆浓度的影响试验、反应时间的影响试验、搅拌速度的影响试验；同时还对硫酸浓度、温度、反应时间以及搅拌速度这四个因素进行了正交试验的研究,最后确定最佳试验条件为：硫酸浓度为15%,温度为50℃,矿浆浓度为30%,反应时间为120分钟,搅拌速度为300转/分。由于硫酸浸出废液中含有大量的未反应的游离硫酸,为了有效利用这部分硫酸,降低硫酸使用量,本研究对硫酸溶液浸出硫铁矿烧渣得到的反应废液进行了循环利用研究,研究表明废液经配酸后,返回浸出阶段用于硫铁矿烧渣的浸出,可有效的利用浸出液中的游离硫酸,使工业硫酸的用量明显降低；反应废液经配酸后返回浸出阶段用于硫铁矿烧渣的浸出,经三次循环使用均可有效的降低处理样品中的砷、硫含量,其中砷和铁的含量均达到炼铁原料相应指标的要求,杂质脱出效果与直接使用硫酸处理原料时相当。由于单独采用硫酸溶液处理硫铁矿烧渣,样品中硫含量达不到炼铁原料质量要求,本论文进行了在硫酸溶液中加入添加剂共同作用处理硫铁矿烧渣的探索性研究,研究表明在硫酸溶液中添加重铬酸钾或氯酸钾处理硫铁矿烧渣,可使样品中的硫含量降至0.279～0.291%,可以同时达到脱砷脱硫的目的,脱砷、脱硫后的烧渣能很好的达到炼铁原料的质量要求。同时在本论文中,对硫酸溶液处理硫铁矿烧渣脱出其中砷的过程进行了动力学研究,动力学研究表明：采用硫酸溶液浸出硫铁矿烧渣脱砷的浸出过程可用粒径不变的收缩未反应核模型描述,浸出过程的化学反应速率受界面化学反应过程控制；浸出过程的化学反应的表观活化能Ea=140.075kJ/mol,化学反应级数为0.8287。更多还原

【Abstract】 Pyrite slag is a kind of waste slag discharged from the process of producing sulfuric acid from pyrite in chemical factory, which contain mainly Fe and a few impurities such as Si, Ca, Mg, S, As, Cu and Ag etc. Its main minerals include hematite, magnetite, quartz, gypsum etc. The amount of pyrite slag discharged is about 1.0×107～1.5×107 t each year. At present a large amount of pyrite slag is stored up or filled in buries processing, not only it occupies plenty of land, but also the factory must pay the expense of the land, the transport expense, the filling spends in buries and so on. At the same time it also does pollution to air, water and earth. Meanwhile there are much Fe, about 40%-60%, and many useful materials such as Cu, Ag, Au in the pyrite slag, and it is a kind of valuable reused resource. Therefore, to reuse the slag not only can eliminate pollution, but also turn waste to useful material which can bring some economic profit and society profit.Comprehensive utilizing pyrite slag has been paid more attention in many countries and many developed countries already have carried on the comprehensive utilization research of pyrite slag many years ago. Although people began to study the utilization of pyrite slag from 1970’s in china, because of bad quality of our slag, lower level of technology and lag economy etc, the utilization ratio is still far lower than other countries. There are many difficulties in utilizing the slag, in which the most main one is the impurity of pyrite slag can not be removed of, specially the arsenic element and the sulfur element bring the harm to the comprehensive utilization of slag (such as Fe raw material).This paper researches the process that pyrite slag is leached by sulfuric acid solution, which can remove As and S element in pyrite slag effectively. The research indicates that after the slag is treated with sulfuric acid solution, As content is reduced to 0.036%, it’s elimination eficiency is 98.7%, S content is reduced to 0.319%, Fe content of sample treated is raised to 62.56%, and As content and Fe content the in treated slag can satisfy quality achievements of iron-smelting raw material.To obtain optimum process conditions, the paper studied effect of sulfuric acid concentration, temperature, solid concentration, the reaction time, stirring speed on Fe, As and S content of sample, and conduct orthogonal experiment.The optimum technical conditions of removing of As and S are:the concentration of arsenic removal reagent is 15%, the temperature is 50℃, the solid concentration is 30%, the reaction time is 120 minutes, and the stirring speed is 300 rpm.The paper study circulation utilization of the waste liquid obtained from leaching pyrite slag with sulfuric acid by returning to leaching stage. The research indicates that when the waste liquid is returned to the leaching stage to leach pyrite slag, which is matched with acid, free sulfuric acid in leaching liquid can be utilized effectively and the amount of industry sulfuric acid used is reduced obviously. When circulation utilization of the waste liquid reaches three times which is returned to the leaching stage to leach pyrite slag, the As and S content in processing sample may be reduced effectively and the iron is concentrated simultaneously, As and Fe content in sample can achieve the quality requirement of raw material of iron-making.Because S content of sample do not achieve the quality requirement of raw material of iron-making when pyrite slag is leached by sulfuric acid solution, the paper study effect of additive in sulfuric acid solution on removing S from pyrite slag. The research indicates that when K2Cr2O7 or KClO3 is mixed into sulfuric acid solution and the solution is used treating pyrite slag, S content in sample may be reduced to 0.279～0.291%, and can achieve removal of As and S simultaneously. The pyrite slag of removing As and S can achieve the quality requirement of raw material of iron-making.Meanwhile the paper carried on dynamics research of the processing of removing the arsenic element from pyrite slag by sulfuric acid.Simultaneously dynamics research indicated that, the leaching process of removing arsenic from pyrite slag by sulfuric acid may be described by the unreacted shrink core model with solid resultant (inert material) and the invariable particle size, chemical reaction speed of leaching process was controlled by surface chemical reaction process, the chemical reaction apparent activation energy of leaching process Ea=140.075kJ/mol, the chemical reaction order is 0.8287.更多还原