In terms of mechanism of action, scale inhibitors have four functions: chelation and solubilization, coagulation and dispersion, electrostatic repulsion, and crystal distortion.   In laboratory evaluation experiments, dispersion is a remedial measure for chelation, and lattice distortion is a remedial measure for dispersion. Today, the editor will briefly introduce the dispersing and lattice distortion effects of scale inhibitors.

dispersion

The result of dispersion is to prevent the mutual contact and aggregation between scaling particles, thereby preventing the growth of scale. Scaling particles can be calcium and magnesium ions, scaling particles composed of thousands of CaCO3 and MgCO3 molecules, as well as dust, sediment, or other water-insoluble substances. Dispersants are polymers with a certain relative molecular weight (or degree of polymerization), and the dispersibility is closely related to the size of the relative molecular weight (or degree of polymerization). If the degree of polymerization is too low, the number of particles adsorbed and dispersed will be small, resulting in low dispersion efficiency; If the degree of aggregation is too high, there will be too many particles adsorbed and dispersed, causing the water to become turbid and even forming flocs (which act similarly to coagulants). Compared to chelation, dispersion is more efficient. Experiments have shown that 1 mg of dispersant can stabilize scale particles ranging from 10 to 100 mg in circulating water. In medium to high hardness water, the dispersing function of the scale inhibitor plays a major role.

Lattice distortion effect

When the hardness and alkalinity of the system are high and the chelating agents and dispersants used are not sufficient to completely prevent their precipitation, they inevitably precipitate. If there is no dispersant present, the growth of scale will follow the general law of crystal growth, and the formed scale will firmly adhere to the surface of the heat exchanger. If there is a sufficient amount of dispersant present, the scaling particles (composed of hundreds or thousands of CaCO3 molecules) are adsorbed and surrounded by the dispersant, preventing them from arranging on their regular lattice, thus making the generated dirt soft and easy to be washed away by water flow.