Patents by Inventor Herman J. Pieterse

Herman J. Pieterse has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 5071477
    Abstract: The present invention is directed to an improvement in a process for the recovery of gold from refractory sulfidic auriferous ores which comprises oxidizing a slurry of ore with oxygen gas under pressure in the presence of sulfuric acid, neutralizing the oxidized slurry, cyanidizing the neutralized slurry to leach gold therefrom, and recovering gold from the resultant leachate. In accordance with the improved process, the oxidation of the ore slurry is carried out in a manner whereby, after a startup phase during which oxidation is initiated, the amount of sulfuric acid added to the ore slurry is sufficient to insure the oxidation of that portion of the sulfide sulfur in the ore which will allow recovery, by cyanide leaching, of at least about 80% of the gold in the ore. The oxidized slurry can be neutralized without a washing operation.
    Type: Grant
    Filed: May 3, 1990
    Date of Patent: December 10, 1991
    Assignee: American Barrick Resources Corporation of Toronto
    Inventors: Kenneth G. Thomas, Herman J. Pieterse, Robert E. Brewer, Kevin S. Fraser