There are many ways to soften hard water and avoid deposition of scale. Frequently used methods are:
1) Ion exchange method: The specific cation exchange resin is used to replace calcium and magnesium ions in water with sodium ions. Since the solubility of sodium salt is high, scale generation due to temperature increase is avoided. This method is currently the most commonly used standard method. The main advantages are: the effect is stable and accurate, and the process is mature. The hardness can be reduced to zero. Soft water equipment that uses this method is also commonly referred to as an "ion exchanger" (since it is mostly a sodium ion exchange resin, it is also often referred to as a "sodium ion exchanger").
2) Lime Method: Lime is added to the water, which is mainly used to handle high-flow hard water, and can only reduce the hardness to a certain extent.
Lime softening principle Lime is added to hard water first, then soda ash is added, and the mixture can be fully stirred and then filtered. The basic principle is:
First add lime milk (Ca(OH)2) to hard water
MgCl2 + Ca(OH)2 = CaCl2 + Mg(OH)2â†“ (transforms hardness from magnesium ion to hardness formed from calcium ions)
Soda ash (Na2CO3) is added to remove excess calcium hydroxide and calcium ions that cause permanent hardness.
This method is effective for water with temporary hardness and permanent hardness. 3) Dosing method: adding a special scale inhibitor to the water can change the characteristics of the combination of calcium and magnesium ions and carbonate ions, so that the scale can not be precipitated and deposited. There are many scale inhibitors that can be used industrially. The characteristics of this method are: less one-time investment and wide adaptability; but when the water volume is soft, the running cost is high. Due to the addition of chemical substances, the application of water is greatly limited, and it cannot be used for drinking in general. Food processing, industrial production and other aspects. It is also rarely used in civilian fields.
4) Electromagnetic method: Use a certain electric field or magnetic field in water to change the characteristics of ions, thereby changing the deposition rate of calcium carbonate (magnesium carbonate) and the physical properties during deposition to prevent the formation of hard scale. Its characteristics are: equipment investment is small, easy installation, low operating costs; but the effect is not stable enough, there is no uniform measurement standards, and because the main function is only affect the physical properties of a certain range of scale, so the use of treated water Time and distance have some limitations. The treatment of circulating cooling water, which is mostly used in commercial applications (such as central air-conditioning), cannot be applied to industrial production and the treatment of boiler makeup water (at the same time, the mechanism of this kind of equipment has not been truly verified by theory).
5) Membrane separation method: Both nanofiltration (NF) and reverse osmosis (RO) membranes can intercept calcium and magnesium ions in water, thereby fundamentally reducing the hardness of water. The characteristic of this method is that the effect is obvious and stable, and the treated water has a wide range of application; however, it has higher requirements for water inlet pressure, and the equipment investment and operating costs are higher. Generally less used, and more for specialized softening.
According to practical experience and characteristics, the most commonly used method in industrial boilers and industrial production is the ion exchange method (currently basically standard equipment). In ordinary circumstances, the term â€œsoftenerâ€ generally refers to such equipment.
In catering, food, chemical, pharmaceutical and other fields, air-conditioning, industrial circulating water and other applications, the use of ion exchange method to treat the replenishment.
In small hot water boilers, heat exchangers, etc., dosing method is used.
Commercial central air-conditioning and industrial cooling water with low temperature (up to a temperature of about 60 degrees) mostly use electromagnetic method for full-flow treatment, that is, all circulating water is treated, and in most cases, water is supplemented with supplementary water. Exchange method or recycling water treatment method to ensure the effect.
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