Hydrated lime, also known as calcium hydroxide (Ca(OH)2)is an alkaline powder produced by the reaction of calcium oxide (CaO) with water. The production process is known as lime slaking.

The reaction is highly exothermic and is often carried out in special extinguishing systems to ensure uniform hydration.

Properties and chemical structure

Hydrated lime is a white, crystalline powder with a high affinity for water and has the following characteristics:

  • pH value: Strong alkalinity (pH value of approx. 12.4 in saturated solution).
  • Reactivity: High reactivity with acids and heavy metal ions.
  • Solubility: Moderately soluble in water (1.85 g/L at 20 °C), solubility decreases with increasing temperature.
Dosing station and preparation station for lime milk, Lime Dosing Station

Photo: ALMA LIME lime milk dosing and preparation station

Industrial applications

  1. Water and waste water treatment
    Hydrated lime is a universal reagent in industrial water treatment. It is used for:

    • Neutralization of acidic waste waterEspecially for processes contaminated with sulphuric or hydrochloric acid.
    • Precipitation of heavy metalsHeavy metal ions are precipitated as hydroxides, which facilitates the separation of solids.
    • Phosphate elimination: In municipal wastewater treatment to reduce the phosphorus load in order to prevent eutrophication.

  2. Construction industry
    Hydrated lime is used as a binding agent in mortars and plasters. It improves workability and increases the durability of materials.

  3. Chemical industry

    • Production of calcium compounds such as calcium chloride or calcium stearate.
    • pH value regulation in chemical processes.

  4. Environmental technology
    Hydrated lime is used in flue gas cleaning systems for desulphurization and the removal of acid gases.

  5. Agriculture
    Used for soil improvement and disinfection to regulate the pH value of the soil and eliminate pathogenic microorganisms.

Technological use in practice

Milk of lime preparation:
Hydrated lime is often used in the form of milk of lime. It is prepared in specially developed milk of lime preparation stations, such as the ALMA LIME systemfrom ALMAWATECH. These ensure a homogeneous mixture and precise dosing, which maximizes chemical efficiency.

Dosing station for flocculants, precipitants and neutralizing agents for wastewater treatment

Photo: ALMA LIME lime milk dosing and preparation station and other IBC dosing stations from ALMAWATECH

Advantages of using hydrated lime

  • Cost-effective and versatile.
  • Effective pH value regulation and precipitation properties.
  • Easy handling and storage.

Conclusion

Hydrated lime is an indispensable reagent in industrial water and wastewater treatment. Its chemical properties and versatile applications make it one of the most frequently used substances in process water and environmental technology. With innovative systems such as ALMA LIME companies can further optimize their efficiency and sustainability.

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