Examples of this include pressure oxidation (POX) of sulfide ores and concentrates, high-pressure acid leaching (HPAL) of nickel laterites, and wet-air oxidation of organics. Both batch and continuous reactors are available at Hazen for developing high-temperature processes.

Hazen's engineers have assisted clients in developing POX processes for refractory gold ores, metals recovery from catalysts, and sulfide concentrates of copper, nickel, zinc, and molybdenum. Hazen has successfully scaled up batch experiments to pilot operations. A number of commercial plants throughout the world have been designed, built, and successfully operated based on pilot plant data generated at Hazen.

Processes utilizing HPAL of nickel laterites using sulfuric acid have been piloted at Hazen. These processes involve temperatures up to 250°C at low pH, with the goal of minimizing acid use while maximizing nickel and cobalt extractions.