Increasing refractory gold production for Petropavlovsk

A partnership worth its weight in gold

Petropavlovsk is one of the five largest gold mining companies in Russia, with three operations named Malomir, Pioneer, and Albyn in Russia’s Far Eastern Federal District. The company supplements traditional non-refractory production with the processing of refractory concentrate.

The mining of refractory ore is becoming increasingly common in Russia’s numerous operational gold mines, with the process requiring additional pre-treatment prior to cyanidation for gold recovery.

Enabling profitable processing of challenging ore

Close to 50% of Petropavlovsk’s 21 Moz of resources and reserves are now classified as refractory. As it will be necessary for Petropavlovsk to process refractory ore in the long term, the company decided to develop and invest in a pressure oxidation (POX) hub at Pokrovskiy, where concentrates from different mines can be processed.

Petropavlovsk’s four autoclaves process in the region up to 500,000 tons of flotation concentrate per year, with this project opening up new opportunities in refractory ore processing for the Russian gold mining industry. The POX hub is in close proximity to the company’s depleted mine, Pokrovskiy, where it benefits from milling facilities, road and rail infrastructure, low-cost renewable power, and a nearby limestone deposit – a key ingredient in the POX process.

The plant was commissioned at the end of 2018, initially treating refractory gold concentrate from the Malomir mine – which accounted for 18% of Petropavlovsk’s gold production in 2018 – and third-party concentrates. In the future, the POX hub will treat concentrates from the group’s Pioneer refractory gold mine, which is one of the largest gold mines in Russia based on processing capacity.

Optimizing performance with extensive R&D

The company performed extensive research into industrial-scale POX technology, building a state-ofthe-art R&D center in St. Petersburg in 2008 and a POX pilot plant in Blagoveshchensk in 2011. Extensive batch test campaigns were conducted at the R&D center to determine the optimal process conditions and develop a POX flowsheet for different ore types. A detailed mathematical model was developed to help optimize the design of the POX process. Process performance was confirmed and the model was validated with pilot-scale experiments at the Blagoveshchensk plant, providing a solid basis for the scale-up and final plant design.

A reliable full-service partner

With a long and successful history of developing and supplying process solutions, technologies, and services for the mining and metallurgical industries, Outotec was the ideal partner to help Petropavlovsk implement such a complex project. Outotec’s experts analyzed the test results from the pilot-scale experiments at Blagoveshchensk and offered a complete solution, including engineering and procurement. Outotec was committed from the very beginning to integrating every piece of the solution together to help create a state-ofthe-art POX hub.

Joint development ensures fast implementation

Based on the data and information gathered by Petropavlovsk, Outotec provided basic and detail engineering services for both the Malomir and Pioneer concentrators and the Pokrovskiy POX hub. Engineering and equipment supply were performed in stages to ensure fast implementation. Outotec supplied most of the equipment for Malomir and the Pokrovskiy POX process plant. Construction of the Malomir concentrator plant and the Pokrovskiy POX hub was managed by Petropavlovsk’s in-house construction department together with their subcontractors. Outotec provided advisory services for equipment installation, instrumentation, automation, and commissioning.

The POX plant flowsheet

The Pokrovskiy site benefits from well-developed infrastructure, including energy and water supply as well as a road network. The existing facilities were utilized and integrated into the design. The delivery scope included:

• Separate treatment process routes for Malomir and Pioneer concentrates
• Four autoclaves
• Two-stage flash allowing energy recovery (24 MW)
• Integration with existing regrinding and resin-in-pulp facilities and infrastructure
• Concentrate treatment capacity up to 500,000 tpa

A systematic approach ensures successful start-up and commissioning

Project development was approached systematically, resulting in the successful start-up of both the Malomir concentrator plant and the Pokrovskiy POX hub in 2018, with the Malomir concentrator achieving its design capacity. The two autoclave trains were efficiently brought up to design capacity and the design throughput has been reached. The first gold was produced within three weeks of start-up and recovery has remained within the predicted range. A heat and water recovery system has been commissioned, and part of the energy generated in the pressure oxidation of sulfides is distributed to the local district heating network.

Petropavlovsk had organized extensive training sessions for operators to support fast commissioning, including a dedicated autoclave training simulator to enable operators to learn the process in a safe environment.

State-of-the-art POX hub increases production

The hub and its associated flotation infrastructure at Malomir and Pioneer have unlocked the value of refractory gold.

Overall, the plant commissioning was successful and achieved ahead of schedule, and the close co-operation between Petropavlovsk and Outotec was the key to its success. The start-up of the Pioneer concentrator is planned for 2020.

*Metso Outotec was formed July 1, 2020 when Metso and Outotec merged into one company. This case study has been written prior to the merger under the old company name.