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Engineering Design

General Pattern of the Technological Process

The technological process of gold mining is defined by features of the deposit. The gravitational gold extraction method, the flotation method and the cyanidation method of gold ore extraction have been considered and compared. When choosing the gold extraction method, the composition of the ore, the grain size of gold and the presence of arsenides and sulphides in the ore have been taken into account, as the latter two elements actively react with cyanides, blocking the transition of gold into the solution. Therefore, it has been decided to use a combined scheme – the gravitational-cyanic one.

The general production pattern of gold mining facilities includes the primary processes – extraction and enrichment as well as auxiliary processes – infrastructure, transportation etc.

Basic processes
Extraction
Ore benefition
Implementation
Supporting processes
Provision of infrastracture
Logistics
Storage facilities

Technology for Extraction of Gold Ore

The development of the Kadara gold deposit will be carried out by an open method of development or open development of mineral deposits. The development of open-pit mineral deposits includes the following stages:

  • preliminary stage, during which the surface of the land quarry is vacated, i.e. trees are cut, swamps and lakes are drained, rivers are diverted, roads and utilities are transferred; the deposit is pre-drained; the quarry is protected from surface water; the fertile soil layer is removes and stored etc.;
  • construction stage, includes a set of mining operations, creating an initial front of overburden and mining operations and availability of development operations; this stage includes construction of buildings and structures of the surface complex, facilities, mining and transport communications, providing access to the mining floor of the quarry;
  • development stage, which includes stripping work, i.e. excavation, transfer and placement stripping soils in dumps; and mining operations, including excavation, transfer, unloading or storage of minerals; the stripping operations result in systematic removal of empty rocks to gain access to the mineral resources, therefore, their function is a preparatory one, while the mining operations resulting in extraction of minerals is the extraction work;
  • restorative stage, includes reclamation of lands disturbed by mining operations.

All stages of open development of an open-pit field, i.e. deposits or parts thereof are carried out on a land plot, which is the land allotment of the quarry, which also includes dumps of stripping soils, a production site and other production facilities.

The adopted system should ensure a systematic and safe development of the field with the rational use of its reserves, meeting the requirements for environmental protection and restoration of lands disturbed by open mine works.

A rational system of open development should ensure extraction of minerals in the planned amount, meet the standard quality requirements, ensure maximum extraction from the subsoil, high labor efficiency and cost effectiveness along with maximum safety of works

Technology of Enrichment of Gold Ore

The structure of the gold recovery complex will include the following main subdivisions: ore extraction and ore dressing department, hydrometallurgical department, pre-production area and the tailing unit.

Ore from the quarries of the Kadara deposit will flow to the receiving hopper of the crushing plant. From there, the ore is fed with an apron feeder (Metso) into an auger-toothed crusher (Metso or Sanme). The crushed ore is fed by stationary conveyor, and then the spreader (Takraf or Sandvik) to the cone of crushed ore. From the cone, the crushed ore is again fed into the wet self-grinding mills (Cemtec), which are located in the section of the ore preparation and ore dressing department with belt conveyor belts. The sub-nutrient product is fed from the mill, to the sump and from there, using WARMAN 12/10 pumps (Weir Minerals), the grinded product is pumped into CAVEX 650 hydro-cyclone units (Weir Minerals). The hydro-cyclone units separate the pulp grade.

The fine grade (0.074 mm) is fed to Dorr Oliver (FLSmidth Minerals) flotation machines; while the coarse grade (sands) is partially fed to high-frequency screens (Sizitec). Oversize products are fed to a ball mill for re-grinding (Metso or Intech). The undersized products are fed again by WARMAN 12/10 (Weir Minerals) pumps through surge tanks (Tasmo) to KNELSON concentrators (FLSmidth Minerals).

In KNELSON concentrators, gravitational enrichment of coarse gold is done, and a gravel concentrate is formed. This gravel concentrate is then sent to the hydrometallurgical department for intensive cyanidation with ConSep ACACIA unit (FLSmidth Minerals).

This is followed by the process of sorption and desorption of gold in disrobers. The sub-crushing product after the wet self-grinding mill (Cemtec) is fed to a grinding mill (Metso or Intech). The sub-debarked pre-milled product is mixed with the first stage sub-crushing product of the grinding mill (Cemtec) and fed to the sump, where they both are fed to CAVEX 650 (Weir Minerals) hydrocyclone units. As mentioned above, the fine fraction, after passing the hydrocyclone units, is fed for flotation stage. The flotation stage includes flotation enrichment of finely dispersed gold. After the flotation, the flotation concentrate is fed for thickening, and then the thickened product with a density of 55-60% is fed to the main sorption of the hydrometallurgical unit.

It should be mentioned that a new environment friendly reagent for leaching gold without cyanide, Flotent GoldSC 570 of Chinese production, was tested in Russia in 2016. The results were positive, as the recovery of gold by the new reagent was 12% higher. The price of the environment friendly reagent is currently 1.5 times higher than the price of cyanide, but, based on calculations and taking into account the costs of processes to ensure the safety of the cyanide technology, it is still much more profitable to use the new reagent than the unsafe sodium cyanide.