Development of Wet Recycling Process to Remove Tramp Elements from Scraped Steels

开发废钢中去除杂质元素的湿法回收工艺

基本信息

批准号：
11555181
负责人：
TSURU Tooru
金额：
$ 8.51万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Many recycling processes for scraped steels have been proposed in these decades, however, wet processes to remove tramp elements are very rare because of their processing speed. We proposed again to use wet process based on electrochemical method to remove zinc and copper which are major harmful elements for using recycled steels. In a concentrated nitric acid solution, zinc and copper easily dissolved contrasting steel dissolution which are negligible by complete passivation of steels. Moreover, stability the passive films on steels in nitric acid depends upon the concentration of nitrate ions. We finally proposed a method to remove and recover coppers from scraped steels by using aqueous ammonia solution and electrolysis. In aqueous ammonia solution, copper and zinc dissolved as ammonia complexes in neutral to alkaline solution, however, iron remains stable passive state. To accelerate dissolution rate of copper, the scraped steels containing sufficient amount of copper was anodically polarized and the dissolved copper was deposited to the counter electrode by the same current. Current efficiency of the anodic dissolution was almost 100 % and that of cathodic deposition reached to 70 %. The purity of the deposited copper exceeds 99.9 %. In this research, we designed a bi-potentiostate having a capability of 50 A and 50 V of output. Using this, the electrode potential of the counter electrode also controlled to maintain a suitable deposition potentials for copper. To extend the acceleration of copper dissolution, anodic dissolution mechanism of copper was analyzed using a rotating disk electrode. The dissolution is controlled by diffusion of ammonia to the electrode in a stagnant condition. In a condition of eliminating diffusion effect, the rate determining step is found a chemical reaction following the electron transfer reaction.

在这几十年中，已经提出了许多用于刮擦钢的回收过程，但是，由于其处理速度，去除流浪汉元素的湿法非常罕见。我们再次提议使用基于电化学方法的湿过程去除锌和铜，这是使用再生钢的主要有害元素。在浓缩的硝酸溶液中，锌和铜很容易溶解钢溶解，这可以通过完全钝化钢而微不足道。此外，稳定性硝酸中钢上的被动膜取决于硝酸盐离子的浓度。最终，我们提出了一种通过使用氨溶液和电解的水从刮钢中去除和回收铜的方法。在氨溶液中，铜和锌作为中性至碱性溶液中的氨复合物溶解，但是铁保持稳定。为了加速铜的溶解速率，含足够量的铜的刮擦钢呈阳极极化，并通过相同的电流将溶解的铜沉积在柜台电极上。阳极溶解的当前效率几乎为100％，阴极沉积的效率达到70％。沉积铜的纯度超过99.9％。在这项研究中，我们设计了一个两静脉静脉固醇，功能为50 a和50 v。使用此功能，计数器电极的电极电势还控制了铜的合适沉积电势。为了扩展铜溶解的加速度，使用旋转盘电极分析铜的阳极溶解机理。溶解是通过在停滞状态下向电极扩散到电极的。在消除扩散效果的条件下，发现速率确定步骤是在电子转移反应后的化学反应。