Study on selective calcium removal by adsorption and gypsum precipitation control

在淡水河谷长港加工厂，镍精矿采用加压氧化法浸出，以**回收镍、铜和钴，并使用石灰提高浸出液的pH值，以去除沉淀物中的铁。**由于在除铁过程中使用石灰时产生了高浓度的钙离子，**浸出液中**存在硫酸盐离子，石膏(CaSO4.2H2O)沉淀物在管道系统中积聚得非常快，导致**严重的流量限制。为了暂时解决这个问题，该工厂正在建设旁路**管道，以便清理堵塞的主管道。用石膏垢清洗管道需要时间、人力和金钱。这是一个严重的过程和技术问题，他们必须解决**生产的顺利和稳定**，特别是在冬季，寒冷的气温促进了石膏结垢速度的增加。**石膏的沉淀取决于处理体系中钙离子浓度和硫酸盐离子浓度的乘积**。在这个项目中，我们计划解决或减少石膏结垢问题，方法是通过使用树脂或其他吸收剂吸附选择性除钙，或/和**控制石膏沉淀，即在大容量储罐或浓缩器中加速石膏沉淀，**在含有高浓度**钙离子和硫酸盐离子的溶液进入管道系统之前，**这对石膏的清洗和处理要容易得多。在确定流程时**将考虑工程、环境和经济因素。**NSERC Engage计划的完成将帮助淡水河谷长港加工厂保持**更稳定和可控的镍生产流程。该项目对淡水河谷长港业务以及纽芬兰和拉布拉多省具有重大的技术、经济和社会意义。

At Vale Long Harbour Processing Plant, nickel concentrate is leached using pressure oxidation process to**recover nickel, copper and cobalt, and lime is used to raise the pH of leach liquor to remove iron as precipitate.**Due to the high concentrations of calcium ion from the use of lime in iron removal process and sulfate ion in**the leach liquor, gypsum (CaSO4.2H2O) precipitate builds up very quickly in pipeline systems, resulting in**severe flow restrictions. To overcome the problem temporarily, the plant is in the process of building bypass**lines to allow cleaning the clogged main pipelines. It takes time, labour and money to clean pipelines with**gypsum scale. This is a serious process and technological problem they must solve for smooth and stable**production, especially in winter time when cold temperatures promote increased gypsum scaling rates.**The precipitation of gypsum is determined by the product of calcium ion concentration and sulfate ion**concentration in the processed system. In this project, we plan to solve or reduce the magnitude of the gypsum**fouling problem through selective calcium removal by adsorption using resins or other absorbents, or/and**controlled gypsum precipitation, i.e., accelerating gypsum precipitation in large volume tanks or thickeners,**which is much easier for gypsum cleaning and processing, before the solution with high concentrations of**calcium ion and sulfate ion enters to the pipeline systems. Engineering, environmental and economic factors**will be considered for process determination.**The accomplishment of this NSERC Engage program will help Vale Long Harbour Processing Plant maintain a**more stable and controllable nickel production process. The program is of great technological, economic and**social significances to Vale Long Harbour Operations and the Province of Newfoundland and Labrador.