Mining well water evaporation treatment
Mining operations generate large amounts of mine water and tailings dam leachate, which are complex in quality, containing high concentrations of sulfates, heavy metals, and suspended solids. Evaporation processes can not only reduce the volume of wastewater but also recover valuable salts (such as sodium sulfate and magnesium sulfate), turning waste into treasure.
Wastewater characteristics
● TDS: 5,000～80,000 mg/L, varies greatly depending on the type of mineral (coal/copper/lithium).
● High sulfate content: SO₄²⁻ concentration can reach 10,000–40,000 mg/L, with Na₂SO₄ being the main recyclable product.
● Heavy metals: High content of heavy metals such as Fe, Mn, Cu, and Zn, which must be removed beforehand.
● High suspended solids: SS can reach hundreds to thousands of ppm, requiring adequate pretreatment.
● Large fluctuations in water volume: Affected by rainfall and mining depth, the treatment system needs to have a certain peak-shaving capacity.
Processing flow
| Mine water evaporation treatment process Mine water inflow → equalization tank → coagulation and sedimentation (removal of suspended solids and heavy metals) → multi-media filtration → reverse osmosis pre-concentration (TDS increased to 20,000~40,000 mg/L) → multi-effect evaporation/TVR evaporation concentration → forced circulation crystallizer → centrifuge separation → anhydrous sodium sulfate/magnesium sulfate (industrial grade) → sale or export Condensate: Reused in mining production water, achieving zero discharge. |
Key Processes
● Deep removal of heavy metals: Before evaporation, Fe/Mn/Cu/Zn and other metals must be reduced to below ppm level to avoid metal deposition on the evaporator tube wall and a decrease in product salt quality.
● RO pre-concentration: When the water volume is large, reverse osmosis is used to concentrate the mine water to the feed concentration of the evaporator, which greatly reduces the evaporator's processing capacity and energy consumption.
● Separate crystallization: The solubility of sodium sulfate and magnesium sulfate changes with temperature in opposite directions. They can be separated by high-temperature evaporation to precipitate MgSO₄ and low-temperature crystallization to precipitate Na₂SO₄·10H₂O.
● TVR Applicability: Mining areas usually have industrial steam supply. TVR (Thermal Compression Evaporation) can reduce initial investment and is suitable for small and medium-sized mines with low water volume.
