Kounrad: Copper Recovery Through In Situ Dump Leaching in Kazakhstan

The Kounrad in situ dump leach operation is an operating copper cathode production facility located in Kazakhstan, owned by Central Asia Metals plc through its subsidiary. The operation processes historical mine dumps from the former Kounrad open-pit copper mine using dump leaching with solvent extraction and electrowinning. The plant was commissioned in 2012 and has undergone two stages of expansion. Construction of the original plant was completed in 2012 with a capital expenditure of US$39 million, and the facility has operated continuously since first copper production in April 2012.

Critical Data

Overview

The Kounrad operation processes copper from historic waste dumps generated by previous open-pit mining activity. The process design uses in situ dump leaching where raffinate solution at pH 1.2 is distributed across the dump surfaces to dissolve copper mineralisation. Pregnant leach solution (PLS) collected at the base of the dumps is pumped to a central SX-EW plant for copper recovery. The facility has produced copper cathode continuously since 2012, reaching a maximum annual production of 14,254 tonnes in 2022.

The operation was designed by the Beijing General Research Institute of Mining and Metallurgy (BGRIMM) in 2010. BGRIMM developed a detailed leaching schedule and designed a plant capable of treating a range of flow rates and solution grades. The design accounted for extreme climate conditions, particularly winter operability. Two expansion stages have been completed since start up. Stage 1 in 2015 increased cathode capacity from 35 tpd to 50 tpd. Stage 2 in 2016-2017 developed the western dump area with transfer pipelines, power infrastructure, and additional boiler capacity.

Leaching of eastern dumps 6, 7, and 9-10 is now largely complete, though some additional recovery continues through further leaching. Dump 5 is partially leached with further production planned. The remaining eastern dump, Dump 2, will be leached at the end of the mine life due to lower recoveries associated with higher clay content. Current production focuses on the western dump area.

Key Process Stages

The recovery process follows a continuous flow from solution distribution through to final cathode production. Raffinate from the SX-EW plant is pumped via a 450 mm pipeline to the leach areas. When a new leach area is started, the dumps are first flattened with a bulldozer and the surface is ripped to break up compacted material. Solution is distributed through pipes ranging from 225 mm to 90 mm diameter, then passes to 16 mm dripper pipes spaced 0.6 m apart with hole spacings of 0.6 m. Application rates are approximately 2.5 to 3 litres per square metre per hour.

During winter months, solutions are heated using coal-fired boilers. Heat exchangers in the SX-EW plant warm PLS to approximately 10°C. The heated solutions are distributed under HDPE liners. Additional dripper systems can be installed on each dump as backup in case of freezing.

Acidic solutions percolate through the dumps, dissolving copper minerals together with other acid-soluble elements. The low permeability clay base on which the dumps are located restricts solution losses. PLS is recovered into drainage ditches excavated at the toe of each dump.

Solution collection uses the same technique at both eastern and western dumps. A collection interceptor trench is excavated at the dump toe. Trenches are typically 3.5 m deep and 7 m wide and are HDPE lined. Solutions gravitate along channels to collection ponds. At the western plant site there are three ponds of 10,000 m³ capacity each for raffinate, PLS, and emergency storage, plus a 3,500 m³ pond. Seven emergency discharge ponds are located along the 12.5 km pipeline between western and eastern areas. At the eastern plant site there are four main ponds for PLS storage with capacities of 40,000 m³, two of 6,000 m³, and 4,000 m³.

PLS from the western dumps is pumped 12.5 km to the eastern SX-EW plant. Raffinate returns through a separate pipeline to the western irrigation solution pond.

The solvent extraction plant was commissioned in 2012 with a PLS treatment capacity increased to 1,200 m³/h as part of Stage 1 expansion. The SX circuit consists of six mixer-settler tanks with two-stage mixer boxes measuring 2.8 by 2.8 by 3.4 m and settlers of 20.0 by 13.0 by 12.0 m (260 m²). In the mixer boxes, PLS is agitated with an organic phase consisting of LIX and Escaid. LIX selectively absorbs copper over iron, and Escaid acts as a diluent. The loaded organic phase is contacted with acid-rich return from the electrowinning circuit to recover copper into an enriched aqueous phase.

The circuit is designed for a rich electrolyte flow rate of 180 m³/h. Two stages of electrolyte filtration remove organic material ahead of electrowinning. The first stage uses coagulation, and the second uses filtration.

The electrowinning plant has two sections. The rich electrolyte from SX is heated to a minimum of 35°C through heat exchangers. It is pumped to the first stage (EW2) consisting of 24 cells with anode and cathode spacing at 90 mm. The lean electrolyte then goes to the second stage (EW1) consisting of 50 cells. A total of approximately 2,500 lead anode plates and 2,500 stainless steel cathode sheets are placed inside these cells.

Rich electrolyte contains approximately 45 g/l Cu and 150 g/l H₂SO₄. Spent electrolyte contains approximately 35 g/l Cu and 180 g/l H₂SO₄. Chlorine levels are maintained below 30 ppm. Guar is added to smooth cathode surfaces, and cobalt sulphate is added to reduce anode erosion.

Copper is harvested every three days on a planned schedule. A proportion of stainless steel cathodes are lifted from the cells by crane and washed. Physical removal of copper is achieved after mechanical vibration loosens the sheets. Copper sheets are formed into bundles of 30 to 40 sheets weighing 1.5 to 2.0 tonnes.

Additional Interesting Data and Summary

The facility operates eight coal-fired boilers with combined installed capacity of 22 MW (8 by 2.8 MW units) distributed across two locations. The east boiler house contains five units with mechanical feeding. The west boiler house contains three units that are manually fed. Boiler utilisation is weather-dependent, with peak winter conditions requiring 100% utilisation of all units for up to a month. The site consumes approximately 20 kt of coal annually from regional Pavlodar coalfields. A scheduled programme to replace three boilers is planned to commence in 2026.

Critical backup power is provided by six emergency generator units across both sites. Additional capacity comes from a 4.7 MW solar farm, though without battery installation contributions are limited to daytime periods.

Copper cathode quality conforms to LME Grade A at greater than 99.99% Cu. Impurity levels are historically very low.

The site laboratory analyses routine plant control samples using ICP-OES, atomic absorption spectrophotometry, UV spectrophotometry, automatic titration equipment, and an induction furnace. Leach plant samples are analysed daily for copper, iron, pH, acidity, and chloride. Solutions within the SX-EW site are sampled manually every 2 to 4 hours. The laboratory operates with 13 staff on a 12-hour shift rota. Copper cathode product is sampled by drilling, and samples are split and sent to SGS Laboratories as an umpire service.

Maintenance uses a four-shift system managed through the Chief Mechanical Engineer and Chief Power Engineer, supported by 45 to 50 mechanical and electrical personnel. Major invasive maintenance is concentrated into two annual 12-hour shutdowns in April and October.

Process consumables for 2025 included 3,964 tonnes of sulphuric acid, 607.46 tonnes of Escaid, 85.96 tonnes of LIX-984, 5.46 tonnes of cobalt sulphate, 3.719 tonnes of guar or Vecosol, and 56,934,833 kWh of electricity.

Historical production has ranged from 6,586 tonnes in 2012 to a peak of 14,254 tonnes in 2022. Total production from 2012 through 2025 reached 178,961 tonnes of copper cathode. The forecast production schedule plans for 74,459 tonnes of copper cathode from 2026 to 2034, declining from 12,000 tonnes in 2026 to approximately 6,000 tonnes in 2032 and 2033.

Leach recovery estimates are prepared by site metallurgical staff based on laboratory and pilot plant testing, assumptions of leach and solution migration rates, and cathode production. Due to the overlapping nature of the dumps and inability to collect and measure leach solutions from each dump separately, individual dump recoveries cannot be accurately measured. From oxide dumps, 69.0 kt of copper has been recovered at an overall leach recovery of 51%, with 12.5 kt remaining. From mixed and sulphide dumps, 110.3 kt of copper has been recovered at 42% overall leach recovery, with 62.9 kt remaining. Overall, 179.3 kt of copper has been recovered with 75.4 kt remaining. A leach recovery of 25% was applied to Dump 2 due to percolation issues associated with higher clay content. Testwork is continuing to improve that recovery.

A loss factor of 0.5% is applied for SX-EW recovery inefficiencies. A leach recovery of 42.0% equates to an overall recovery to cathode of 41.5%.

The Qualified Persons consider there is sufficient leachable metal to support the production plan based on the Mineral Reserve estimate and estimated metallurgical recoveries. They also consider the operation has sufficient supply of energy and water for forecast throughputs, with well-established sourcing of process consumables from recognised suppliers.

Key Processes

• In situ dump leaching with raffinate solution at pH 1.2
• Solution distribution through dripper systems at 2.5-3 l/m²/h
• PLS collection via HDPE-lined interceptor trenches and ponds
• Solvent extraction using LIX and Escaid in six mixer-settler units
• Electrowinning with two-stage circuit (EW2 and EW1) producing LME Grade A cathode
• Coal-fired boiler heating for winter solution temperature management
• Mechanical copper harvesting on three-day cycles
• Site laboratory for process control analysis with umpire service confirmation

Source: NI 43-101 Technical Report on the Kounrad In Situ Dump Leach Operation, Kazakhstan, December 31, 2025. Project website: Kounrad