Built by Belgium's Coek Engineering, the autoclave is 50m long, has a diameter of 6m and weighs 1,100 tonnes, said Polymetal. It has cost US$27 million in total for the equipment and its shipment to Amursk.
The vessel, which is made of steel and has a titanium lining, will operate at the temperature of up to 240 Celsius and a pressure of 45 bar, and is the largest in the gold industry globally.
"The installation of the autoclave vessel is a crucial project milestone. We accomplished it on time despite the COVID-related restrictions and complex logistics. It marks our consistent progress towards start-up in Q3 2023", said Vitaly Nesis, chief executive of Polymetal.
Amursk POX-2, which is designed for processing double-refractory ore, is expected to have a 250-300 Ktpa concentrate capacity after it comes online in 2023.
The company has said that its POX-2 process differs from its POX-1 facility as it will operate at twice the pressure, and 40 Celsius higher temperature.
This requires the use of a larger and more advanced autoclave that is lined with titanium rather than brick.
Total capital costs for the POX-2 project in 2019-2021 are estimated at US$431 million.