Against the backdrop of increasingly complex global gold resources and fluctuating grades, efficient gold extraction processes have become the core support for the profitability of mining projects. The 1200 tons/day gold concentrator in Tanzania, a highly representative mining project in the region, has achieved ultra-high leaching rates of 93.75% for sulfide ore and 91.58% for oxide ore through the precise application of whole-sludge cyanidation gold extraction technology, setting a benchmark for similar gold mining projects. This project adopts an EPC+M+O full lifecycle service model, optimizing the entire chain from process design to operational implementation, maximizing the technological advantages of the whole-sludge cyanidation process.
The whole-sludge cyanidation process, also known as carbon leaching (CIL), is a highly efficient gold extraction technology that simultaneously performs leaching and adsorption. Its core logic lies in the full reaction between the cyanide solution and the gold ore slurry, converting gold into soluble complexes, which are then simultaneously adsorbed and recovered using activated carbon, significantly shortening the production cycle and improving the recovery rate. Compared to the traditional carbon-in-pulp (CIP) process, the whole-sludge cyanidation process eliminates the separate operations of cyanide leaching and activated carbon adsorption, integrating the two processes into one. This not only reduces equipment investment and land area but also minimizes gold retention during production, creating conditions for rapid capital recovery. Taking the Tanzanian project as an example, based on a daily processing capacity of 1200 tons of ore and a sulfide ore grade of 10.7 g/t, simply shortening the gold retention period can reduce the mine owner's monthly capital occupation costs by hundreds of thousands of dollars.
The successful application of this process in the Tanzanian project is inseparable from the precise adaptation to the ore characteristics. The project's ore consists of sulfide ore (10.7 g/t) and oxide ore (2.4 g/t), with gold as the only valuable element. The differences in ore properties placed personalized requirements on the process parameters. To achieve efficient leaching of both types of ores, the project team optimized specific process details: In the leaching slurry preparation stage, precise adjustment of the slurry concentration and pH value (maintained above 10.5) ensured both the reaction efficiency of cyanide and gold and reduced ineffective cyanide consumption and environmental risks. Xinhai's specially formulated imported coconut shell activated carbon was selected; its small pore size, high activity, wear resistance, and regenerability increased the adsorption rate by 30%, effectively reducing the cost increase caused by activated carbon loss.
The efficient operation of the whole-sludge cyanidation process also relies on the coordinated operation of core equipment. The project employs a stepped arrangement of high-efficiency cyanidation leaching tanks in the leaching stage. The first two sections are used for slurry pre-cyanidation, while the latter seven sections simultaneously perform cyanidation and countercurrent adsorption with activated carbon, ensuring that gold in the ore is fully dissolved and rapidly captured. The stirring system adopts a centrally aerated riser design, reducing power consumption by 70% compared to traditional mechanical stirring tanks, while simultaneously achieving uniform slurry suspension, reducing activated carbon wear, and further improving gold recovery rate. In the desorption-electrolysis stage, the project employs a high-temperature, high-pressure desorption method. Under conditions of 150℃ and 0.5MPa, 99% of the gold in the gold-loaded carbon can be extracted in just 2-6 hours. After processing by an integrated desorption-electrolysis system, high-purity solid gold is directly obtained, simplifying the subsequent smelting process.
It is worth noting that the highly toxic nature of cyanide has previously sparked controversy within the industry regarding this process. However, through scientific safety management and environmental protection measures, harmless production can be achieved. The Tanzania project, by maintaining an alkaline environment (pH≥10.5) throughout the process and implementing a comprehensive cyanide recovery and destruction system, minimized the risk of cyanide leakage and its impact on the surrounding environment. This approach complies with local environmental regulations and achieves a balance between economic and ecological benefits. Today, the experience gained from the project's full-sludge cyanidation process has become an important reference for medium- to high-grade gold mining projects in Africa, providing a feasible path for more mines to overcome gold extraction efficiency bottlenecks.
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