Grant: Engage Grants Program

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.