Knowledge of softened water treatment and softened water treatment equipment

Let's first understand what softened water is.

In daily life, we often see scale forming on the inner wall of kettles after long-term use. What is the reason? It turns out that the water we use contains a lot of inorganic salts, such as calcium and magnesium salts. These salts cannot be seen by the naked eye in water at room temperature. Once they are heated and boiled, a lot of calcium and magnesium salts will precipitate out in the form of carbonates, and they will form scale close to the wall of the kettle. We usually use the indicator "hardness" to represent the content of calcium and magnesium ions in water. 1 degree of hardness is equivalent to 10 mg of calcium oxide per liter of water. Water below 8 degrees is called soft water, above 17 degrees is called hard water, and between 8 and 17 degrees is called moderately hard water. Rain, snow water, river, lake water are all soft water, spring water, deep well water, and sea water are all hard water.

Raw water refers to untreated water. In a broad sense, water before entering the water treatment process is also called raw water for the water treatment. For example, water sent from the water source to the clarification tank for treatment is called raw water.

Let's take a look at the difference between softened water and other water

Softened water refers to water in which the hardness (mainly calcium and magnesium ions in water) is removed or reduced to a certain extent. In the process of softening water, only the hardness is reduced, and the total salt content remains unchanged.

Demineralized water refers to water in which the salts (mainly strong electrolytes dissolved in water) are removed or reduced to a certain extent. Its conductivity is generally 1.0~10.0µS/cm, resistivity (25℃) (0.1~1.0)×106Ω·cm, and salt content is 1~5mg/L.

Pure water refers to water in which strong electrolytes and weak electrolytes (such as SiO2, CO2, etc.) in water are removed or reduced to a certain extent. Its conductivity is generally: 1.0~0.1µS/cm, conductivity (1.01.0~10.0)×106Ω·cm. The salt content is <1mg/L.

Ultrapure water refers to water in which the conductive medium is almost completely removed, and the non-dissociated gases, colloids and organic substances (including bacteria, etc.) are also removed to a very low level. Its conductivity is generally 0.1~0.055µS/cm, resistivity (25℃)>10×106Ω·cm, and salt content is less than 0.1 mg/L. The conductivity of ideal pure water (theoretically) is 0.05µS/cm, and the resistivity (25℃) is 18.3×106Ω·cm.

What is softened water treatment?

Strong acidic cationic resin is used to replace calcium and magnesium ions in the raw water, and the boiler water filtered through the softening water equipment becomes softened purified water for boilers with extremely low hardness.

Working principle

Ion exchange method

Method: Use specific cation exchange resin to replace calcium and magnesium ions in water with sodium ions. Since the solubility of sodium salt is very high, it avoids the formation of scale with the increase of temperature.

Features and effects: The effect is stable and accurate, and the process is mature. The hardness can be reduced to 0.

Scope of application: In catering, food, chemical, pharmaceutical and other fields, air conditioning, industrial circulating water and other applications. The most commonly used standard method at present.

Electromagnetic method

Method: Add a certain electric field or magnetic field to the water to change the characteristics of ions, thereby changing the deposition speed of calcium carbonate (magnesium carbonate) and the physical properties during deposition to prevent the formation of hard scale.

Features and effects: Small equipment investment, easy installation, and low operating costs. The effect is not stable enough, there is no unified measurement standard, and because the main function is only to affect the physical properties of scale within a certain range, the use time and distance of the treated water are limited.

Scope of application: It is mostly used for the treatment of circulating cooling water in commercial (such as central air conditioning, etc.), and cannot be used for industrial production and boiler feed water treatment.

Membrane separation method

Method: Both nanofiltration membrane (NF) and reverse osmosis membrane (RO) can intercept calcium and magnesium ions in water, thereby fundamentally reducing the hardness of water.

The hardness can only be reduced to a certain range.

Featured effect: The effect is obvious and stable, and the treated water has a wide range of applications. There are high requirements for water inlet pressure, and the equipment investment and operating costs are high.

Scope of application: Generally less used for special softening treatment.

Lime method

Method: Add lime to the water.

Featured effect: The hardness can only be reduced to a certain range.

Scope of application: Applicable to high-hardness water with a large flow rate.

Dosing method

Method: Adding a special scale inhibitor to the water can change the characteristics of the combination of calcium and magnesium ions with carbonate ions, so that scale cannot precipitate and deposit.

Featured effect: Less one-time investment and wide adaptability. The operating cost is biased when the water volume is soft and large.

Scope of application: Due to the addition of chemical substances, the application of water is greatly restricted. Generally, it cannot be used for drinking, food processing, industrial production, etc. It is rarely used in the civilian field.

Softening water equipment work flow and working requirements

1) Softening water equipment workflow

Working (sometimes called water production, the same below), backwashing, salt absorption (regeneration), slow flushing (replacement), and fast flushing. All processes of different softening water equipment are very similar, but there may be some additional processes due to different actual processes or control needs. Any softening water equipment based on sodium ion exchange is developed on the basis of these five processes (among which, fully automatic softening water equipment will increase the brine re-injection process).

Backwashing: After working for a period of time, the equipment will intercept a lot of dirt brought by the raw water on the upper part of the resin. After removing these dirt, the ion exchange resin can be fully exposed and the regeneration effect can be guaranteed. The backwashing process is that water washes in from the bottom of the resin and flows out from the top, so that the dirt intercepted from the top can be washed away. This process generally takes about 5-15 minutes.

Salt absorption (regeneration): the process of injecting brine into the resin tank. Traditional equipment uses a salt pump to inject brine, and fully automatic equipment uses a dedicated built-in ejector to absorb brine (as long as the incoming water has a certain pressure). In actual working process, the regeneration effect of brine flowing through the resin at a slower speed is better than that of simply soaking the resin with brine, so the softening water equipment is regenerated by the method of slowly flowing brine through the resin. This process generally takes about 30 minutes, and the actual time is affected by the amount of salt used.

Slow flushing (displacement): After the brine flows through the resin, the process of slowly flushing all the salt in the resin with raw water at the same flow rate is called slow flushing. Since there are still a large number of calcium and magnesium ions on the functional groups being exchanged by sodium ions during this flushing process, according to actual experience, this process is the main process of regeneration, so many people call this process replacement. This process is generally the same as the time of salt absorption, that is, about 30 minutes.

Fast flushing: In order to thoroughly flush the residual salt, the resin should be flushed with raw water at a flow rate close to the actual work. The final water output of this process should be soft water that meets the standards. In general, the fast flushing process takes 5-15 minutes.

2) Technical indicators and working requirements of softening water equipment:

Inlet water pressure: 0.18-0.6Mpa

Working temperature: 1-55℃ Source water hardness: <8mmol/L

Operation mode: automatic/manual Outlet water hardness: ≤0.03mmol/L

Regeneration agent: NaCL Regeneration method: downstream/countercurrent

Exchange agent: 001*7 strong acid ion exchange resin

Control mode: time/flow Working power supply: 220V/50Hz

The role of soft water treatment

1. The use of softened water equipment saves a lot of wasted fuel

When the boiler is scaled, a boiler with a working pressure of 1.4MPa will produce 1mm of scale, which will waste 8% of fuel.

2. Softened water equipment improves thermal efficiency and reduces output

When the boiler evaporation surface is scaled, the heat on the fire side cannot be quickly transferred to the water side, which will reduce the output of the boiler. If the boiler is scaled due to improper water treatment, the boiler evaporation capacity will be reduced by one third, and the automatic operation line cannot be started due to insufficient gas supply.

3. The use of softened water equipment reduces the amount of boiler maintenance

After the boiler plate or pipe is scaled, it is very difficult to remove, especially due to the leakage, cracks, damage, deformation, corrosion and other diseases caused by the scale. Not only does it damage the boiler, but it also consumes a lot of manpower and material resources to repair it, which not only shortens the operation time, but also increases the maintenance cost.

4. The application of softening water equipment reduces safety hazards

Boiler accidents caused by scale account for more than 20% of the total number of boiler accidents, which not only causes equipment losses but also threatens personal safety. The infrastructure and operating costs of water treatment account for a quarter of the various savings.

Softening water treatment equipment

Softening water equipment, as the name suggests, is equipment that reduces water hardness. It mainly removes calcium and magnesium ions in water. In layman's terms, it is equipment that reduces water hardness. Its main functions are to remove calcium and magnesium ions in water, activate water quality, sterilize and kill algae, and prevent and remove scale. Softening water equipment cannot reduce the total salt content in water during the softening process. It is widely used in hot water boiler systems, heat exchange systems, industrial cooling systems, central air conditioning systems, and other water-using equipment systems.

Working principle

Since the hardness of water is mainly formed and expressed by calcium and magnesium, cation exchange resins (water softeners) are generally used to replace Ca2+ and Mg2+ (the main components of scale formation) in water. As the Ca2+ and Mg2+ in the resin increase, the efficiency of the resin in removing Ca2+ and Mg2+ gradually decreases.

When the resin absorbs a certain amount of calcium and magnesium ions, it must be regenerated. The regeneration process is to flush the resin layer with salt water in the salt box, replace the hardness ions on the resin, and discharge them out of the tank with the regeneration waste liquid. The resin will resume its softening exchange function.

Since the hardness of water is mainly formed by calcium and magnesium, the principle of sodium ion exchange softening treatment is to pass the raw water through the sodium type cation exchange resin, so that the hardness components Ca2+ and Mg2+ in the water are exchanged with Na+ in the resin, thereby absorbing Ca2+ and Mg2+ in the water to soften the water.

Workflow

Work (sometimes called water production, the same below), backwashing, salt absorption (regeneration), slow flushing (replacement), and fast flushing. All the processes of different softening water equipment are very similar, but there may be some additional processes due to different actual processes or control needs. Any softening water equipment based on sodium ion exchange is developed on the basis of these five processes (among which, fully automatic softening water equipment will increase the brine re-injection process).

Backwashing: After working for a period of time, the equipment will intercept a lot of dirt brought by the raw water on the upper part of the resin. After removing these dirt, the ion exchange resin can be fully exposed and the regeneration effect can be guaranteed. The backwashing process is that water washes in from the bottom of the resin and flows out from the top, so that the dirt intercepted at the top can be washed away. This process generally takes about 5-15 minutes.

Slow flushing (displacement): After the brine flows through the resin, the process of slowly flushing all the salt in the resin with raw water at the same flow rate is called slow flushing. Since a large number of calcium and magnesium ions on the functional groups are still exchanged by sodium ions during this flushing process, according to actual experience, this process is the main process of regeneration, so many people call this process replacement. This process is generally the same as the time of salt absorption, that is, about 30 minutes.

Application

Different applications require different soft water treatment equipment

1. Scope of application of softened water equipment:

① Heating

② Cooling water

③ Process water

④ Steam boiler

⑤ Steel smelting

⑥ Chemical and pharmaceutical

2. System water use time required by the industry

System water use time is: hourly water consumption, average value, and peak value. Equipment can be selected according to water supply time. If continuous water supply is not required, single-valve single-tank equipment can be selected; if continuous water supply is required, it is necessary to select a double-bed centralized control or double-control double-bed series softened water treatment device.

3. Hardness of water source

For the same model of water softener, the water production cycle of the one with harder water quality will inevitably be relatively shorter, and the water output will be lower, which will lead to frequent regeneration of softening water equipment and reduce the service life of resin. In this case, it is necessary to choose a larger model of water softener and increase the volume of resin.

二. Selection of softening water equipment

① Controller: divided into automatic control and manual control. The brand selection can be imported or domestic.

② Resin tank: The tank material of the softening water device is divided into fiberglass, carbon steel, and stainless steel.

③ Equipment control form: One is that the prepared water volume reaches the set value and is automatically restored, which is called flow type; it is suitable for all water supply system softening water treatment equipment. The second is the method of controlling regeneration metering by time, which is called time type; it is suitable for water supply systems with stable water volume, and the shortest restoration and regeneration cycle is 24 hours.

④ Equipment combination:

Single control single bed: stop water supply for 2 hours during the restoration period or continue to supply raw water (hard water bypass).

Single control double bed: alternating water supply, one use and one standby type.

Double control double bed: alternating water supply, one use and one standby type.

Double control double bed: simultaneous water supply, alternating regeneration.

Multiple control beds: more than three softening water resin tanks are used in parallel, suitable for large water supply systems.

It can be widely used in the softening of feed water for steam boilers, hot water boilers, exchangers, evaporative condensers, air conditioners, direct-fired engines, etc. It can also be used for the treatment of domestic water in hotels, restaurants, office buildings, apartments, homes, etc., and for softening water in the food, beverage, brewing, laundry, printing and dyeing, chemical, pharmaceutical and other industries.

2. Selection of softening water equipment

① Controller: divided into automatic control and manual control. The brand selection can be imported or domestic.

② Resin tank: The tank material of the softening water device is divided into fiberglass, carbon steel, and stainless steel.

④ Equipment combination:

Single control single bed: stop water supply for 2 hours during the restoration period or continue to supply raw water (hard water bypass).

Single control double bed: alternating water supply, one use and one standby type.

Double control double bed: alternating water supply, one use and one standby type.

Double control double bed: simultaneous water supply, alternating regeneration.

Multiple control beds: more than three softening water resin tanks are used in parallel, suitable for large water supply systems.

Equipment classification

Industrial water treatment equipment, drinking water treatment equipment, filling equipment, water treatment accessories.

Industrial water treatment equipment

Large reverse osmosis equipment in power plants, ultrapure water equipment in the pharmaceutical and electronic industries, pure water equipment for watering flowers and fruits, dosing equipment, boiler softening water equipment;

Drinking water treatment equipment

Pure water equipment in the food and beverage industry, pure water and mineral water equipment in water plants, rural drinking water equipment, direct drinking water equipment for hotels, schools, government agencies, canteens, etc.;

Filling equipment

Large barrel and small bottle filling lines, barrel brushing and capping machines;

Water treatment accessories

Filter media, filter elements, booster pumps, reverse osmosis membranes, membrane shells, precision filters, flow meters, pressure gauges, ozone generators, ultraviolet sterilizers, scale inhibitors, etc.