Let's first understand what softened water is

In our daily life, we often see scale formation on the inner wall of the kettle after long use. What is the reason for this? It turns out that the water we use contains many inorganic salts, such as calcium and magnesium salts. Once they are heated and boiled, a lot of calcium and magnesium salts are precipitated as carbonates, and they cling to the wall of the pot to form scale. We usually express the content of calcium and magnesium ions in water by "hardness". One degree of hardness is equivalent to 10 mg of calcium oxide per liter of water. Water below 8 degrees is called soft water, water above 17 degrees is called hard water, and water between 8 and 17 degrees is called moderate hard water. Rain, snow, rivers and lakes are all soft water, while springs, deep wells and sea water are all hard water.

Take another look at the difference between softened water and other water

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

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

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

Pure water refers to the water with strong electrolyte and weak electrolyte (such as SiO2, CO2, etc.) removed or reduced to a certain extent. Its conductivity is generally 1.0 ~ 0.1 μ s / cm, conductivity (1.01.0 ~ 10.0) × 106Ω·cm 。 The salt content was less than 1mg / L.

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

What is softened water treatment?

Strong acid cation resin is used to replace calcium and magnesium ions in raw water, and then the boiler water filtered by the softened water equipment becomes the softened water with very low hardness.

working principle

Ion exchange method

Methods: the specific cation exchange resin was used to replace calcium and magnesium ions in water with sodium ions. Due to the high solubility of sodium salt, the scale formation with the increase of temperature was avoided.

Characteristics and effect: the effect is stable and accurate, and the technology is mature. The hardness can be reduced to 0.

Scope of application: 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

Methods: adding a certain electric field or magnetic field to water to change the characteristics of ions, so as to change the deposition speed and physical characteristics of calcium carbonate (magnesium carbonate) to prevent the formation of hard scale.

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

Scope of application: it is mainly used for the treatment of circulating cooling water in commercial (such as central air conditioning, etc.), but cannot be used for the treatment of industrial production and boiler make-up water.

Membrane separation

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

The hardness can only be reduced to a certain range.

Characteristic effect: the effect is obvious and stable, and the treated water has a wide range of application. There are higher requirements for inlet pressure, equipment investment and operation cost.

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

Lime process

Methods: lime was added to water.

Characteristic effect: can only reduce the hardness to a certain range.

Scope of application: applicable to high hard water with large flow.

Dosing method

Methods: adding special scale inhibitor to water can change the combination characteristics of calcium and magnesium ions and carbonate ions, so that scale can not be precipitated and deposited.

Characteristics and effects: less one-time investment, wide adaptability. When the water quantity is soft, the operation cost is low.

Scope of application: due to the addition of chemical substances, the application of water is greatly limited, generally can not be used in drinking, food processing, industrial production and other aspects. It is rarely used in civil field.

Working process and requirements of softened water equipment

1) Work flow of softened water equipment

There are five processes: operation (sometimes called water production, the same below), backwashing, salt absorption (regeneration), slow flushing (replacement) and fast flushing. All processes of different softened water equipment are very close, but due to different actual processes or control needs, there may be some additional processes. Any softened water equipment based on sodium ion exchange is developed on the basis of these five processes (among them, automatic softened water equipment will increase brine reinjection process).

Backwashing: after working for a period of time, the equipment will intercept a lot of pollutants from raw water on the top of the resin. After removing these pollutants, the ion exchange resin can be completely 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 usually takes about 5-15 minutes.

Salt absorption (regeneration): in the process of injecting salt water into resin tank, the traditional equipment uses salt pump to inject salt water, and the fully automatic equipment uses special built-in injector to suck salt water (as long as the water inlet has a certain pressure). In the actual working process, the regeneration effect of salt water flowing through the resin at a slow speed is better than that of soaking the resin with salt water alone. Therefore, the method of salt water flowing through the resin at a slow speed is adopted for the regeneration of softened water equipment, which generally takes about 30 minutes. The actual time is affected by the amount of salt used.

Slow flushing (replacement): after the salt water 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. Because a large number of calcium and magnesium ions on the functional groups are still exchanged by sodium ions in this flushing process, according to practical experience, this process is the main process of regeneration, so many people call this process replacement. This process is generally the same as salt absorption time, 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 effluent of this process should be soft water up to the standard. Generally, the fast flushing process is 5-15 minutes.

2) Technical indexes and working requirements of softened water equipment:

Inlet water pressure: 0.18-0.6mpa

Working temperature: 1-55 ℃, hardness of source water: < 8 mmol / L

Operation mode: automatic / manual outlet water hardness: ≤ 0.03mmol/l

Regenerant: NaCl regeneration mode: downstream / countercurrent

Exchanger: 001 * 7 strong acid ion exchange resin

Control mode: time / flow working power: 220 V / 50 Hz

Function of soft water exchange treatment

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

When the boiler has scale, the boiler with working pressure of 1.4mpa will generate 1 mm scale, which will waste 8% of the fuel.

2. Soften water equipment to improve thermal efficiency and reduce output

When there is scale on the evaporation surface of the boiler, the heat on the fire side can not be transferred quickly, and the output of the boiler will be reduced on the water supply side. If the evaporation capacity of the boiler is reduced by one third due to improper water treatment and boiler scaling, 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 has scale, it is very difficult to remove, especially due to the scale caused by boiler leakage, cracks, damage, deformation, corrosion and other diseases. It not only damages the boiler, but also consumes a lot of manpower and material resources to repair, which not only shortens the operation time, but also increases the maintenance cost.

4. The application of softened water equipment can reduce the risk to safety

Boiler accidents caused by scale account for more than 20% of the total number of boiler accidents, which not only cause equipment loss, but also threaten personal safety. The capital construction and operation costs of water treatment account for a quarter of the savings.

Softened water treatment equipment

Softening water equipment, as the name suggests, is the equipment to reduce the hardness of water. It is mainly used to remove calcium and magnesium ions in water. Generally speaking, it is the equipment to reduce the hardness of water. Its main functions are to remove calcium and magnesium ions in water, activate water quality, kill bacteria and algae, prevent and remove scale. In the process of softening water, the total salt content in water cannot be reduced. It is widely used in hot water boiler system, heat exchange system, industrial cooling system, central air conditioning system and other water equipment system.

working principle

Because the hardness of water is mainly formed and expressed by calcium and magnesium, cation exchange resin (water softener) is generally used to replace Ca2 + and Mg2 + (the main component of scale formation) in water. With the increase of Ca2 + and Mg2 + in the resin, the efficiency of removing Ca2 + and Mg2 + by resin gradually decreases.

When the resin absorbs a certain amount of calcium and magnesium ions, it must be regenerated. The regeneration process is to wash the resin layer with salt water in the salt tank, replace the hardness ions on the resin, and discharge the regenerated waste liquid out of the tank, so that the resin can restore the softening exchange function.

Because the hardness of water is mainly formed and expressed by calcium and magnesium, because the hardness of water is mainly formed by calcium and magnesium and expressed by sodium ion exchange, the principle of softening treatment is to exchange the hardness components Ca2 + and Mg2 + in the water with Na + in the resin by passing the raw water through sodium type cation exchange resin, so as to absorb Ca2 + and Mg2 + in the water and soften the water.

Workflow

There are five processes: operation (sometimes called water production, the same below), backwashing, salt absorption (regeneration), slow flushing (replacement) and fast flushing. All processes of different softened water equipment are very close, but due to different actual processes or control needs, there may be some additional processes. Any softened water equipment based on sodium ion exchange is developed on the basis of these five processes (among them, automatic softened water equipment will increase brine reinjection process).

Backwashing: after working for a period of time, the equipment will intercept a lot of pollutants from raw water on the top of the resin. After removing these pollutants, the ion exchange resin can be completely 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 usually takes about 5-15 minutes.

Salt absorption (regeneration): in the process of injecting salt water into resin tank, the traditional equipment uses salt pump to inject salt water, and the fully automatic equipment uses special built-in injector to suck salt water (as long as the water inlet has a certain pressure). In the actual working process, the regeneration effect of salt water flowing through the resin at a slow speed is better than that of soaking the resin with salt water alone. Therefore, the method of salt water flowing through the resin at a slow speed is adopted for the regeneration of softened water equipment, which generally takes about 30 minutes. The actual time is affected by the amount of salt used.

Slow flushing (replacement): after the salt water 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. Because a large number of calcium and magnesium ions on the functional groups are still exchanged by sodium ions in this flushing process, according to practical experience, this process is the main process of regeneration, so many people call this process replacement. This process is generally the same as salt absorption time, 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 effluent of this process should be soft water up to the standard. Generally, the fast flushing process is 5-15 minutes.

application

Choose different soft water treatment equipment for different applications

1. Application scope of softened water equipment:

① Heating

② Make up cooling water

③ Process water

④ Steam boiler

⑤ Iron and steel smelting

⑥ Chemical pharmacy

2. System water consumption time required by the industry

Water consumption time of the system: water consumption per hour, average value and peak value. The equipment can be selected according to the water supply time. If continuous water supply is not required, single valve and single tank equipment can be selected; If continuous water supply is needed, double bed centralized control or double control double bed series softened water treatment device should be selected.

3. Hardness of water source

If the water quality of the same type of softener is relatively hard, the water making cycle will be relatively reduced and the water yield will be low, which will lead to frequent regeneration of softened water equipment and reduce the service life of resin. In this case, we need to choose a larger type of water softener to increase the resin volume.

2、 Selection of softened water equipment

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

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

③ Equipment control form: one is automatic reduction when the water quantity reaches the set value, which is called flow type; It is applicable to all softened water treatment equipment of water supply system. The second way is to control regeneration metering by time, which is called time type; It is suitable for water supply system with stable water quantity, and the shortest reduction regeneration cycle is 24 hours.

④ Equipment combination:

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

Single control double bed: alternate water supply, one for use and one for standby.

Double control double bed: alternate water supply, one for use and one for standby.

Double control and double bed: supply water at the same time and regenerate alternately.

Multiple control and several beds: more than three softened water resin tanks are used in parallel, suitable for large water supply system.

It can be widely used to soften the make-up water of steam boiler, hot water boiler, exchanger, evaporative condenser, air conditioner, direct fired machine and other systems. It can also be used in hotels, restaurants, office buildings, apartments, home and other domestic water treatment and softened water treatment in food, beverage, wine making, laundry, printing and dyeing, chemical industry, medicine and other industries.

Technical index

1. Inlet pressure: 0.2 ~ 0.5MPa

2. Raw water hardness: < 12mmol / L (when raw water hardness > 8 mmol / L, special design should be made according to water quality of different regions)

3. Effluent hardness: < 0.03mmol/l (meet the requirements of national water quality standard for low pressure boilers (gb1576-2001));

4. Salt content of raw water < 1500mg / L, turbidity < 5, iron ion < 0.3mg/l

5. Power supply: ~ 220 V, 50 Hz

6. Salt consumption < 100g / g equivalent (related to raw water hardness);

7. Water consumption < 2%; Main technical specifications of automatic softened water desalination equipment with power consumption less than 50W

1. Technical code for construction and acceptance of electric power construction

2. Standard for acceptance and evaluation of thermal power construction quality

3. JB / t74-94 technical conditions for pipeline flange

4. Sand blasting rust removal shall comply with gb8923

5. DL / t5054-1996 technical specification for steam water piping design of thermal power plant

6. GB / t18300-2001 specification for automatic control sodium ion exchanger

7. GB 1576-2001 low pressure boiler water quality

8. GB 5462-199 industrial salt

9. GB / T 13659-1992 001 * 7 strong acid styrene cation exchange resin

10. JB / T 2932-1999 technical conditions of water treatment equipment

11. GB / T 13384-1992 general specification for packaging of mechanical and electrical products

Equipment classification

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

Industrial water treatment equipment

Large scale reverse osmosis equipment in power plant, ultra pure water equipment in medicine and electronics industry, pure water equipment for flower and fruit irrigation, dosing equipment, boiler softened water equipment;

Drinking water treatment equipment

Pure water equipment for food and beverage industry, pure water and mineral water equipment for waterworks, drinking water equipment for rural life, direct drinking water equipment for hotels, schools, institutions and canteens, etc;

Filling equipment

Big barrel and small bottle filling line, barrel brushing and capping machine;

Water treatment accessories

Filter material, filter element, booster pump, reverse osmosis membrane, membrane shell, precision filter, flowmeter, pressure gauge, ozone generator, ultraviolet sterilizer, scale inhibitor, etc.