Recovery of Tungsten from Copper Tailings

Yongping Copper Mine is a polymetallic deposit mainly containing copper and sulfur, with associated tungsten, silver, and other elements. The concentrator has a daily processing capacity of 10,000 tons, with a daily tailings output of approximately 7,000 tons. Analysis of the WO₃ and S content in the tailings shows monthly average grades of 0.064% and 2.28%, respectively. The WO₃ content varies between 0.041% and 0.093%. Annually, over 2,000 tons of tungsten oxide are lost to the tailings.

The tungsten in the copper tailings of Yongping Copper Mine occurs mainly as scheelite, followed by tungsten‑bearing limonite, with very little tungstite. Scheelite‑phase tungsten accounts for 82.05% of the total tungsten; the limonite contains 0.14%–0.18% tungsten. Scheelite is mainly intergrown with garnet, diopside, limonite (hematite), and quartz, with particle sizes of 0.076–0.25 mm. Garnet contains scheelite less than 6 μm in size, and the tungsten in limonite exists as a highly dispersed phase. The main gangue minerals are garnet and quartz, accounting for 32% and 36% of the mineral content, respectively. Additionally, barite and apatite are present; these two minerals have similar floatability to scheelite, increasing the difficulty of separation by flotation. Scheelite has a fine particle size and liberates late. Its size distribution is uneven. The liberation degree in the 0.076–0.04 mm size fraction is only 69%, and over 80% of the intergrowths are poor intergrowths. The multi‑element analysis and particle size analysis of the tailings are shown in Tables 4-42 and 4-43, respectively.

Table 4-42 Multi‑element analysis (%)

Table 4-43 Grain size analysis

It is primarily intergrown with garnet, diopside, limonite, and quartz.

To comprehensively recover scheelite from the tailings, a process of gravity separation – magnetic separation – gravity separation – flotation – gravity separation (see Figure 4-26) was adopted for tailings re‑processing. First, a high‑efficiency spiral chute was used as the primary roughing stage for gangue rejection, discarding 91.25% of the tailings. Next, high‑efficiency magnetic separation equipment was used to remove magnetic minerals and garnet, reducing the amount of tailings fed to the shaking tables to 4%–5%, thus minimizing the number of shaking tables required. After the shaking table, only about 1% of the tailings proceeded to the cleaning desulfurization stage. Finally, a tungsten concentrate with a WO₃ grade of 66.83% and a recovery of 18.01% was obtained, along with a sulfur concentrate containing 42% S at a recovery of 15%, as well as products such as garnet and barite. Based on a daily tailings treatment of 7,000 tons and 330 operating days per year, the annual production is 339.3 tons of scheelite concentrate and 1,584 tons of sulfur concentrate.