Common solar hot water project solutions to scale

1. Ion exchange method: using a specific cation exchange resin to replace calcium and magnesium ions in the water with sodium ions. Due to the high solubility of sodium salt, the formation of scale caused by the increase in temperature is avoided. The main advantages are: the effect is stable and accurate, the process is mature, and the hardness can be reduced to 0. Water softening equipment in this way is generally also called "ion exchanger" (because most of the sodium ion exchange resin is used, it is also called "sodium ion exchanger").

The disadvantages are:

(1) Excessive regenerated waste liquid will be generated, and the cost of using the air source heat pump will be higher;

(2) The salt consumption is large and needs to be restored frequently;

(3) Discharging a large amount of salt-containing wastewater can easily cause pipeline corrosion, and the use of hot water poses a safety hazard.

2. Electromagnetic method: Add a certain electric or magnetic field to the water to change the characteristics of water molecules, thereby changing the deposition rate of calcium carbonate (magnesium carbonate) and the physical characteristics of the deposition to prevent the formation of scale. Its characteristics are: equipment investment is small, installation is convenient, and operating costs are low; but the effect is not stable enough, and there is no unified measurement standard, because the water molecules after passing through the magnetic field will return to the state before the magnetic flux in about half an hour, so after treatment There are certain limitations on the time and distance of water use. From the method point of view, it can only be applied to the treatment of circulating water. There are hard indicators for the size of the magnetic force. The magnetic field strength must be above 2000 Gauss. The most important thing is that the current magnetization function has not been certified. Its feasibility and effectiveness Sexuality is questionable.

3. Membrane separation method: Both nanofiltration membrane (NF) and reverse osmosis membrane (RO) can intercept calcium and magnesium ions in water, thereby fundamentally reducing water hardness. The characteristic of this method is that the effect is obvious and stable, and the scope of application of the treated water is wide; but it has higher requirements on the inlet pressure, and the equipment investment and operating cost are higher.

4. Dosing method: Adding a special scale inhibitor to the water can make calcium and magnesium ions, carbonate ions and the molecules of the agent form complexes, increase their solubility in high-temperature water, and prevent scale precipitation and deposition. At present, there are many scale inhibitors that can be used in industry. The commonly used scale inhibitors in water treatment are complex phosphate, organic phosphonic acid, phosphonic acid, organic phosphonate, polycarboxylic acid and so on. The characteristics of this method are: less one-time investment, wide adaptability, strong scale inhibition and descaling ability, especially suitable for water storage heaters, but the system is more complicated due to the constant input of chemicals.

5. High frequency electronic descaler for descaling

This method needs to cut the pipe during installation, and the electrode is easy to adhere to the suspended matter in the water and cause the system to fail. The installation is troublesome, and the amount of work is large. Now there is a new anti-scaling product quantum ring, which uses the frequency generated by it to resonate with the natural frequency of the mineral ions in the water to make it precipitate in advance. This product has a good anti-scaling effect, but it uses special materials and production technology. , The cost is quite high, and it is difficult for general users to accept.

6. Descaling of permanent magnet equipment

The appearance is a ring-shaped permanent magnet, which is then sheathed on a straight pipe, and the water passing through the pipe is treated by the magnetic field passing through the pipe. It is mostly used in places with large pipelines. Due to its fixed frequency and strength of the magnetic field, the applicable water quality range is relatively narrow. It performs better under certain water quality conditions, but it may not be effective after changing the water quality. .

7. Electronic induction water processor

The principle is that the host generates an induced electromagnetic field in the water with frequency and intensity that changes according to a certain rule. The electromagnetic field causes the scale-forming ions in the water to combine into a large number of aragonite crystal nuclei. When the mineral content in the water exceeds the saturated solubility of water, the scale-forming ions will precipitate and preferentially grow on these nuclei to form aragonite crystals, instead of The precipitation of calcite crystals, while the aragonite crystals are soft and flocculent, which are easily washed away by water. This method is simple to install, does not need to cut and punch, does not require electrode replacement and maintenance, and consumes very little power. It is a perfect solution. However, due to the different opinions of the manufacturers on the promotion, the application is limited.

8. Pickling method:

Hydrochloric acid, phosphoric acid, chromic acid and hydrofluoric acid can be used, but sulfuric acid cannot be used. Because when sulfuric acid is in contact with water, a hard film of calcium sulfate is formed on the surface of the scale, so that the scale under the film is not easily exposed to the acid solution. Although phosphoric acid and chromic acid are more effective than hydrochloric acid, they are generally more expensive than hydrochloric acid. Hydrochloric acid can only clean the carbonate salt scale. The magnesium chloride and calcium chloride produced during pickling are highly soluble and easy to remove, accompanied by the production of carbon dioxide, which has the effect of stirring the hydrochloric acid solution. For pure silicate scale, hydrofluoric acid can be used for cleaning. Sulfate and silicate-based mixed scale can also be cleaned with hydrochloric acid. The function of pickling is to use an acid solution to dissolve the iron oxide layer between the scale and the metal wall, so that the acid contacts the metal, and hydrogen bubbles are generated to cause the scale to fall off. It is different from the principle of hydrochloric acid cleaning of hydrochloride scale. Before pickling, the amount of hydrochloric acid must be accurately calculated according to the degree of scaling. Since the scaling rate of air energy water heaters is very fast, so pickling is required every 2-3 months or even a month. Due to the particularity of the water supply object, the water supply cannot be interrupted during pickling, unlike boiler hot water for low-concentration uninterrupted pickling. Such frequent pickling is unacceptable to users. Therefore, the feasibility of this method is not high.

9. Alkaline washing method:

It is mainly to remove sulfate and silicate scale, and it can also remove the mixed scale of sulfate and silicate. Can not remove carbonate scale. The alkaline washing method is not to dissolve and remove the scale, but to soften the scale, and then remove it mechanically. The medicaments used are sodium carbonate and sodium hydroxide.

Chemical methods are complicated to operate, costly and difficult. Generally used in the descaling of boilers and other equipment, but not suitable for solar water heaters. In addition, the physical methods have the following methods for your reference:

1. Mechanical method: Rinse with water or remove with a brush. If the scale is very hard, it can be cleaned with a pipe washer driven by electricity or water. This method is more suitable in the early stage of scale formation.

2. Electronic method: Using electrical signals to change the molecular structure of water to accelerate the release of minerals from water and make the minerals tightly combined. The combined minerals are taken away with the flow of water, which can prevent the generation of scale.

3. Other methods: such as using magnesium rods, adding minerals, magnetizing, etc., these methods can effectively prevent the generation of scale.