If sodium, potassium, or ammonium ions are present in the leach solution, the corresponding jarosite species will be precipitated in the low-acid leach. The first commercial integration of the Dynatec zinc pressure leach process was at the Cominco Zinc Refinery in Trail, British Columbia, in 1980. The expansion and ensuing operation are well documented. In the process as practiced by Cominco , the bulk of the iron contained in the zinc concentrate fed to pressure leaching is initially extracted to solution, with a portion of the dissolved iron reprecipitating in the autoclave as plumbojarosite. Following removal of sulfur by flotation, the pressure-leach slurry is directed to the calcine leach circuit.
Dissolved iron is precipitated in the neutral leach.
The neutral leach residue reports to the acid leach step. The acid leach residue is transferred to the lead smelter, where it is converted into a disposable slag. A low-acid pressure leach circuit was also chosen for integration with the zinc plant at Kidd Creek to expand zinc production capacity. The original plant, constructed in 1972, was based on conventional electrolytic zinc plant technology, including iron precipitation as sodium jarosite. The pressure-leach expansion was commissioned in 1983, and the operation has been described in detail.