Hydrated lime, or slaked lime, is a versatile alkali whose high reactivity and moderate solubility make it indispensable in heavy-industry. In mining and metallurgy, it controls pH for ore flotation and heap leaching, neutralizes acidic process streams, and forms slag to remove impurities in steelmaking. In water and wastewater treatment, it adjusts pH and precipitates heavy metals, while in flue-gas desulfurization it captures SO₂, curbing acid-rain emissions. Beyond these, hydrated lime stabilizes soils and improves road bases at mining sites, enhances asphalt durability, and serves as a key reagent in chemical manufacturing. Abundant, cost-effective, and eco-friendly, it underpins numerous processes critical to clean production and resource recovery.
Introduction to Hydrated Lime
Hydrated lime, chemically Ca(OH)₂, is produced by adding water to quicklime (CaO) in a hydration reaction that releases heat and yields a fine, white powder known as slaked lime . Its slight water solubility produces a strongly alkaline solution (pH ≈12.4), ideal for neutralizing acids and precipitating impurities in industrial streams.
CaO(s) + H₂O(l) → Ca(OH)₂(s) ΔH = –63.7 kJ/mol
This exothermic reaction “slakes” the lime, creating a material whose reactivity and surface area depend on hydration conditions. Control of particle size and moisture content is critical; finer grades dissolve faster but can generate dust, while coarser grades offer slower reactivity but improved handling.
Mining and Metallurgical Applications
• pH Control in Ore Flotation
In sulfide-ore flotation, precise pH (usually 9–11) is essential for selective collector action. Hydrated lime raises slurry pH, enhancing mineral–collector interactions and suppressing gangue minerals.
• Heap Leaching and Cyanide Detoxification
During gold heap leaching, cyanide solutions percolate ore stacks. pH must be maintained above 10.5 to prevent HCN volatilization. Hydrated lime serves as a cost-effective pH regulator, ensuring operator safety and maximizing gold recovery.
• Slag Formation in Steelmaking
In basic oxygen steelmaking (BOS), impurities (silica, alumina, phosphorus) form a molten slag with lime. Hydrated lime—often after conversion to CaO—removes acid oxides, improving steel quality and reducing refractory wear.
Water Treatment and Environmental Uses
• Neutralization and Metal Precipitation
Hydrated lime is a staple coagulant in industrial water and wastewater treatment. It neutralizes acidic effluents (e.g., from mining or metal-finishing), precipitating metals like Fe, Al, and heavy metals as hydroxides, which are then removed by sedimentation or filtration.
• Flue-Gas Desulfurization (FGD)
Power plants burning sulfur-bearing fuels emit SO₂, a precursor to acid rain. In wet scrubbers, hydrated lime slurry reacts with SO₂ to form calcium sulfite/sulfate, cutting emissions by over 90%.
• Acid Mine Drainage (AMD) Remediation
Where sulfide minerals oxidize, acidic drainage forms (AMD). Hydrated lime neutralizes acidity, raises pH, and precipitates dissolved metals—an essential step in restoring aquatic ecosystems downstream of mine sites.
Construction and Infrastructure in Mining Sites
• Soil Stabilization and Road Base Improvement
Hydrated lime reacts with clay minerals in soils to form cementitious calcium silicates and aluminates, enhancing load-bearing capacity. Mine roads treated with lime-stabilized subgrades exhibit reduced rutting, lower maintenance, and improved durability under heavy haul traffic.
• Asphalt Modification
Adding hydrated lime to asphalt mixtures improves binder–aggregate adhesion, reduces moisture-induced stripping, and slows aging. On haul roads and plant site pavements, lime-treated asphalt resists rutting and fatigue under cyclic loading.
Other Notable Industrial Uses
• Chemical Manufacturing:As a neutralizing reagent and source of Ca²⁺ in producing calcium salts, soaps, and paper chemicals.
• Gas Purification:In chlor-alkali and ammonia plants, lime removes CO₂ and acidic gases.
• Flue-Gas Treatment Beyond SO₂:Hydrated lime also captures HF and HCl in industrial exhausts, protecting equipment and reducing emissions.
Conclusion
From ore beneficiation to clean-air technologies, hydrated lime’s ability to neutralize acids, precipitate metals, and stabilize materials makes it indispensable across mining and industrial sectors. Its low cost, abundance, and eco-friendly pedigree—derived from natural limestone—ensure its continued role in sustainable resource extraction and environmental protection.
For more detailed technical specifications and application guidelines, please feel free to contact at feronia@wit-stone.com | +86-15655559799
Post time: Apr-25-2025