Leading specialists of M HEAVY TECHNOLOGY visited the Northern Mining and Processing Plant, where construction of a tailings thickening complex is underway under the company’s project.
The project was developed in three engineering stages between 2019 and 2023 and includes:
- Feasibility Study (FS);
- Basic Design Stage;
- Detailed Engineering Documentation
Project Objective:
To reduce electric power consumption associated with large-scale process operations within the tailings management system of PJSC Northern Mining and Processing Plant.
Solutions data:
To decrease electrical power consumption required for pumping tailings to the tailings storage facility, a tailings thickening technology is being implemented. This technology decreases the volume of slurry, requiring transportation and reduces the load on the tailings storage facility.
In addition, the process enables return of clarified water from the thickeners to the plant’s recirculating water system for further reuse within the complex.
Scope of Construction:
The Tailings Thickening Complex construction volume includes reconstruction and construction of the following facilities:
- Slurry Pumping Station No. 1 (SPS-1);
- Tailings Distribution Chamber (TDC);
- Four HRT-60 high-rate thickeners, Ø60 m;
- Centralized Slurry Pumping Station (CSPS);
- Reverse Water Supply Pumping Station (RWPS);
- Water Treatment and Seal Water Pumping Station;
- Four Thickened Product Discharge Pump Stations;
- Four Reagent Preparation and Dosing Stations.
The project also provides for construction of power supply networks and facilities, as well as process pipeline infrastructure, including water supply pipeline racks and slurry pipeline systems.
The project is being executed under brownfield conditions within an operating mining and processing facility. M HEAVY TECHNOLOGY’s engineering solutions ensure minimal disruption to production and product quality during construction.
General Process Description.
Tailings slurry containing 3.49% solids is conveyed by gravity through slurry channels to Slurry Pumping Station No. 1 (SPS-1). Following the replacement of the existing pumps with low-head pumping equipment, the slurry is transferred to the Tailings Distribution Chamber (TDC).
In the Tailings Distribution Chamber (TDC) the flow is evenly distributed among four high-rate radial thickeners, each 60 m in diameter. The slurry is treated with Magnafloc 1011 flocculant, which promotes particle agglomeration and settling under gravity.
The thickened product, containing 50–55% solids, is pumped by the discharge pumps to the sump of the Centralized Slurry Pumping Station and is then transported to the tailings storage facility.
Tailings Slurry Reception and Transfer.
Tailings slurry with a solids content of 3–5% is delivered from Concentrating Plant No. 1 (CP-1) through gravity slurry channels to Slurry Pumping Station No. 1 (SPS-1). Following the modernization of the pumping equipment (10 low-head pumps), the slurry is pumped to the Tailings Distribution Chamber (TDC).
From the TDC, the flow is evenly distributed among four high-rate radial thickeners, each with a diameter of 60 m.
Tailings Distribution Chamber (TDC).
The TDC provides hydraulic equalization and flow distribution.
A calming baffle stabilizes the incoming flow before the slurry enters the distribution section, where it is evenly distributed among the thickeners.
The chamber is equipped with level monitoring systems, emergency overflow protection and a drainage system. Internal surfaces are protected by a multilayer wear-resistant lining.
Thickening Process.
The slurry is treated with Magnafloc 1011 flocculant, which promotes particle agglomeration and settling under gravity.
The process results are:
- Thickened product containing 50–55% solids;
- Clarified water with a solids concentration not exceeding 150 mg/L.
The thickened slurry is withdrawn from the central discharge area of the thickener and directed to the discharge pumps, while clarified water is routed to the recirculating water system.
Radial Thickeners.
The thickeners are vertical tanks with conical bottoms and rake-type mechanisms for settled sludge removal. The drive mechanism is located in the upper central section of the unit.
Hydraulic sluicing giants are installed for maintenance and cleaning of internal surfaces.
The equipment is designed for outdoor operation at ambient temperatures to −40°C.
Thickened Product Discharge.
Under each thickener there is an individual discharge pumping station.
The pumps transfer the thickened product to the sump of the Centralized Slurry Pumping Station.
Centralized Slurry Pumping Station (CSPS).
The CSPS serves as an intermediate transportation hub for conveying thickened slurry to the tailings storage facility.
The thickened slurry enters a receiving tank where continuous mixing prevents sedimentation.
The material is then pumped by four Metso Outotec MR500 slurry pumps operating in a 2 × 2 configuration, ensuring reliable transportation to the tailings storage facility. Pump operation is controlled through frequency converters.
The receiving tank is equipped with agitation systems, level measurement devices, emergency overflow protection, drainage systems, and process monitoring instrumentation. Internal surface is protected with wear-resistant lining, while external structures are thermally insulated.
Reverse Water Supply Pumping Station (RWPS).
The Reverse Water Supply Pumping Station ensures uninterrupted delivery of clarified process water to Concentrating Plant No. 1 (CP-1) and is classified as a facility of reliability category I.
Clarified water from the thickeners flows by gravity through four DN1400 pipelines into the RWPS receiving tank. Then the water is pumped for process needs of the plant.
The RWPS was designed entirely by the in-house engineering team of M HEAVY TECHNOLOGY.
Hydraulic sealing and Auxiliary Systems.
A dedicated seal water system supplies filtered water from the Water Treatment and Seal Water Pumping Station to support the operation of pumping equipment. For pumping equipment operation a hydraulic water sealing system with filtered water supply from the water treatment plant and water sealing system is provided. The design also includes systems for flushing check valves and slurry pipelines.
A drainage system is provided to collect and remove accidental leaks from the pump hall to a sump or emergency tank.
Conclusion.
The tailings thickening process implemented at the facility ensures stable thickening of tailings slurry to a solids concentration of 50–55%, efficient separation of clarified water and its subsequent reuse within the recirculating water system.
The project also includes supply of modern pumping, thickening and auxiliary equipment, integrated with advanced automation systems, ensuring reliable and continuous operation of the complex.
Construction is planned in four stages with completion of the first stage scheduled for the first quarter of 2027.
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