Calcium carbonate (CaCO₃) is a widely used inorganic salt that occurs naturally in the form of limestone, marble or chalk. Calcium carbonate plays a central role in industrial water treatment and wastewater treatment, both as a chemical component of water and in relation to scaling problems and the lime-carbonic acid balance in water cycles.
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Technical background
Calcium carbonate dissolves in water partly in the form of calcium ions (Ca²⁺) and carbonate ions (CO₃²-). The solubility of calcium carbonate depends heavily on the pH value, the temperature and the concentration of carbon dioxide (CO₂) in the water.
Hard water usually contains high concentrations of calcium and magnesium ions, with calcium carbonate being the main cause of water hardness. A high calcium carbonate content can lead to deposits in pipes, heat exchangers and membranes, which impairs heat transfer and reduces the efficiency of the systems.
The lime-carbonic acid equilibrium describes the ratio of calcium carbonate and dissolved carbon dioxide in water. This balance is decisive for the corrosion and sedimentation properties of the water. Water that is in equilibrium tends neither to form limescale deposits nor to corrode.
Calcium carbonate in industrial water treatment
Prevention of deposits (scaling): In systems such as cooling water circuits, boilers and reverse osmosis systems the precipitation of calcium carbonate can lead to considerable operating problems. These deposits, also known as scale or scaling, form solid layers on surfaces that hinder heat transfer and drastically reduce the efficiency of the system. To prevent this, antiscalants antiscalants and hardness stabilizers are used to inhibit or slow down the crystallization of calcium carbonate.
Water softening: In water softening, calcium carbonate is removed by chemical precipitation or ion exchange. In chemical softening, calcium hydroxide or soda is added to precipitate the calcium carbonate. In the ion exchange process, calcium ions are replaced by sodium ions, which reduces the hardness of the water.
Photo: Softening system for small water flows(ALMA ION)
Lime-carbonic acid balance and calcium carbonate saturation
The lime-carbonic acid balance describes the chemical balance between dissolved calcium carbonate and carbonic acid (H₂CO₃) in water. This balance determines whether the water is aggressive (corrosive), scaling (forming deposits) or in chemical equilibrium.
Aggressive water: If the water contains too little calcium carbonate, the water can have a corrosive effect and attack metal surfaces. This typically occurs with soft water that contains little calcium and carbonate.
Supersaturated water: An excessively high calcium carbonate content leads to the precipitation of calcium carbonate, which results in limescale deposits in pipes and systems. This condition is also known as scaling.
Equilibrium state: In an equilibrium state, there is a balance between dissolved carbon dioxide and calcium carbonate. In this state, the water has no tendency to corrode or form deposits.
Hardness stabilizers and antiscalants from ALMAWATECH
The ALMA AQUA -product range from ALMAWATECH includes chemicals that are aimed at pH stabilization, hardness stabilization and precipitation of calcium carbonate. These products are specifically used to prevent problems such as scaling and to optimize water quality in various industrial processes.
Hardness stabilizers and antiscalants from the ALMA AQUA product line prevent the formation of calcium carbonate deposits in cooling water and reverse osmosis systems. reverse osmosis systems. They inhibit the crystallization of calcium carbonate and thus contribute to the long-term efficiency of the systems.
Photo: Hardness stabilizers, dispersants and antiscalants from the ALMA AQUA product range
Challenges for water with a high calcium carbonate concentration
Scaling: One of the biggest challenges when using calcium carbonate is the risk of scaling, especially in sophisticated membrane systems such as reverse osmosis. reverse osmosis. Without the use of suitable antiscalants severe scaling can occur, which drastically reduces the performance of the membranes.
Corrosion due to incorrect dosing: An imbalance in the lime-carbonic acid system can lead to corrosion problems if the water contains either too little or too much calcium carbonate.
Conclusion
Calcium carbonate is a key factor in industrial water treatment and wastewater treatment, particularly with regard to water hardness, corrosion, deposits and scaling. scaling. High calcium carbonate concentrations in water lead to deposits that impair heat exchange and the efficiency of systems. At the same time, an imbalance in the lime-carbonic acid system can lead to either scaling or corrosion. It is therefore crucial to control the calcium carbonate behaviour in the water circuit in order to minimize deposits and extend the service life of the systems. With the appropriate hardness stabilizers and antiscalantsas contained in the ALMA AQUA-product range, these problems can be effectively solved and system operation optimized.
