Study on selective calcium removal by adsorption and gypsum precipitation control

在Vale Long Harbour选矿厂，镍精矿采用加压氧化工艺进行浸出，以 ** 回收镍、铜和钴，并使用石灰提高浸出液的pH值，以除去沉淀铁。由于在除铁过程中使用石灰产生的高浓度钙离子和 ** 浸提液中的硫酸根离子，石膏（CaSO4.2H2O）沉淀物在管道系统中非常迅速地积聚，导致 ** 严重的流量限制。为了暂时解决这个问题，工厂正在建造旁路管道，以便清理堵塞的主管道。带 ** 石膏垢的管道清洗费时、费力、费钱。这是一个严重的工艺和技术问题，他们必须解决顺利和稳定的 ** 生产，特别是在冬季，当寒冷的温度促进增加石膏结垢率。石膏的沉淀取决于被处理体系中钙离子浓度和硫酸根离子浓度的乘积。在本项目中，我们计划通过使用树脂或其他吸收剂进行吸附或/和控制石膏沉淀（即，在含有高浓度 ** 钙离子和硫酸根离子的溶液进入管道系统之前，加速石膏在大容量罐或浓缩器中沉淀，** 这对于石膏的清洁和处理来说要容易得多。工艺确定将考虑工程、环境和经济因素 **。该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过程。该项目对淡水河谷长港作业和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.