Summary of knowledge of softened water treatment equipment
2021-03-09
In our daily life, we often see that the inner wall of the kettle will be formed with scale after a long time. What is the reason? The original water we use contains many inorganic salts, such as calcium, magnesium salt, etc. These salts can not be found by naked eyes in the water at room temperature. Once they are heated and boiled, a lot of calcium and magnesium salts are precipitated out of carbonate, and they form scale close to the wall of the pot.
We usually use the "hardness" index to express the content of calcium and magnesium ions in water. Hardness 1 degree is equivalent to 10 mg of calcium oxide per liter of water. Water below 8 degrees is called soft water, and hard water is called hard water when it is higher than 17 degrees, and medium hard water between 8 and 17 degrees. Rain, snow, river, river and lake are soft water, spring water, deep well water and sea water are hard water.
The difference between softened water and other water
Raw water refers to untreated water. Generally speaking, the water before entering the water treatment process is also called the raw water of the water treatment. For example, the water sent to the clarifier by water source is called raw water.
Softened water refers to water with hardness (mainly refers to calcium and magnesium ions in water) to remove or reduce to a certain extent. In the process of softening, the hardness of water decreases, but the total salt content is not changed.
Desalted water refers to the water where salts (mainly strong electrolytes dissolved in water) are removed or reduced to a certain extent. The conductivity is generally 1.0-10.0 μ s/cm, resistivity (25 ℃) (0.1-1.0) × 106 Ω ɋ cm, and salt content is 1-5mg / L.
Pure water refers to the strong electrolyte and weak electrolyte (such as SiO2, CO2, etc.) in water, which can be removed or reduced to a certain extent. The conductivity is generally 1.0-0.1 μ s/cm, and the conductivity (1.01.0-10.0) × 106 Ω · cm. The salt content was less than 1mg / L.
Ultra pure water refers to the almost complete removal of conductive medium in water, and the non dissociated gas, colloid and organic matter (including bacteria) are also removed to a very low level of water. The conductivity is generally 0.1-0.055 μ s/cm, the resistivity (25 ℃) > 10 × 106 Ω · cm, and the salt content is less than 0.1mg/l. The ideal pure water (theoretically) has a conductivity of 0.05 μ s/cm and a resistivity of 18.3 × 106 Ω · cm at 25 ℃.
What is softened water treatment?
The strong acid cation resin is used to replace the calcium and magnesium ions in the raw water, and then the boiler water filtered out by the softened water equipment is the softened water for boiler with very low hardness.
working principle
Ion exchange method
Methods: the calcium magnesium ions in water were replaced by sodium ion with a specific cation exchange resin. Because of the high solubility of sodium salt, the scale formation was avoided with the increase of temperature.
Characteristics and effects: the effect is stable and accurate, and the technology is mature. The hardness can be reduced to 0.
Scope of use: food, food, chemical, medicine and other fields, air conditioning, industrial circulating water and other applications. The most commonly used standard method at present.
Electromagnetic method
Methods: the ion characteristics were changed by adding a certain electric field or magnetic field to the water, so as to change the deposition speed and physical characteristics of the calcium carbonate (magnesium carbonate) to prevent the formation of hard scale.
Features: small investment in equipment, convenient installation and low operating cost. The effect is not stable enough, there is no unified measurement standard, and because the main function is only affecting the physical properties of scale within a certain range, the use time and distance of treated water have certain limitations.
Application scope: it is mainly used for commercial (such as central air conditioning) circulating cooling water treatment, and cannot be applied to industrial production and boiler make-up water treatment.
Membrane separation
Methods: NF and RO can intercept calcium and magnesium ions in water, thus reducing the hardness of water fundamentally.
The hardness can only be reduced to a certain range.
Characteristic effect: the effect is obvious and stable, and the water after treatment is widely used. There are high requirements for the water inlet pressure, and the equipment investment and operation cost are high.
Application scope: generally less used for special softening treatment.
Lime method
Methods: lime was added to the water.
Characteristic effect: only hardness can be reduced to a certain range.
Application scope: high and hard water with large flow.
Dosing method
Methods: adding special scale inhibitor to water can change the characteristics of calcium magnesium ion and carbonate ion combination, so that scale can not be precipitated and deposited.
Characteristic effect: less investment at one time and wide adaptability. When the water volume is soft, the operating cost is partial.
Application scope: because of the chemical substances added, the application of water is greatly limited, and it cannot be applied to drinking, food processing, industrial production and other aspects. It is also rarely used in civil fields.
Working flow and working requirements of softened water equipment
1) Working flow of softened water equipment
The five processes are working (sometimes called water production, the same below), backwashing, salt absorption (regeneration), slow flushing (replacement), and quick flushing. All processes of different softened water equipment are very close, but there may be some additional processes due to the different actual processes or the need of control. Any softened water equipment based on sodium ion exchange is developed on the basis of these five processes (among which, the automatic softener will increase the process of brine reinjection).
Backwash: after a period of operation, the equipment will intercept a lot of dirt brought by raw water on the upper part of resin. After removing these pollutants, the ion exchange resin can be fully exposed, and the regeneration effect can be guaranteed. The backwash process is that water is washed from the bottom of the resin and out of 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): the process of injecting brine into resin tank body. The traditional equipment is to inject salt water with salt pump. The fully automatic equipment is to use special built-in injector to inhale salt water (as long as there is certain pressure for water inlet). In the actual work process, the regeneration effect of brine flowing through the resin at a slower speed is better than that of soaking resin with salt water alone. Therefore, the softened water equipment is regenerated by the method of slow flow of brine through resin. This process generally takes about 30 minutes, and the actual time is affected by the amount of salt used. Slow flushing (replacement): after the brine flows through the resin, the process of washing all the salt in the resin slowly with the same flow rate is called slow flushing. Because there are still a lot of calcium and magnesium ions on the functional groups in the washing process are exchanged by sodium ions, according to the 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, i.e. about 30 minutes. Quick flushing: in order to thoroughly wash the remaining salt, the resin shall be washed with raw water at a flow rate close to the actual work. The final effluent of this process shall be soft water up to standard. In general, the rapid 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 ℃ source water hardness: < 8mmol/l
Operation mode: hardness of automatic / manual water outlet: < 0.03mmol/l
Regenerant: NaCl regeneration mode: downstream / reverse current
Exchange agent: 001 * 7 strong acid ion exchange resin
Control mode: time / flow working power supply: 220v/50hz
The function of soft water exchange treatment
1. the use of softened water equipment saves a lot of waste fuel
When the boiler is incrusted, the boiler with working pressure of 1.4mpa will generate 1 mm scale and waste 8% of fuel.
2. soften water equipment to improve thermal efficiency and reduce output
When the boiler evaporation surface is incrusted, the heat on the fire side can not be transmitted to the feed water side quickly, which will reduce the boiler output. If the boiler scale due to improper water treatment, the evaporation capacity of the boiler is reduced by one third, and the automatic operation line cannot be started due to insufficient air supply.
3. use of softened water equipment to reduce boiler maintenance
After the boiler plate or pipe is incrusted, it is very difficult to remove, especially the boiler leakage, crack, fracture, deformation, corrosion and other diseases caused by the scale. Not only damage the boiler, but also consume a lot of manpower, material and power to overhaul, not only shorten the operation time, but also increase the maintenance cost.
4. application of softened water equipment to reduce safety hazards
Boiler accidents caused by scale account for more than 20% of the total boiler accidents, which not only cause equipment loss, but also threaten personal safety. The cost of infrastructure and operation of water treatment accounts for one fourth of all the cost savings.
Softened water treatment equipment
Soften water equipment, as the name implies, is to reduce the hardness of water, mainly remove calcium and magnesium ions in water, in general, it is a device to reduce the hardness of water. It mainly plays a role in removing calcium and magnesium ions in water, activating water quality, germicidal and algae killing, and preventing scale and scaling. The total salt content of the softened water equipment cannot be reduced during the process of softening water. It has been widely used in hot water boiler system, heat exchange system, industrial cooling system, central air conditioning system and other water equipment systems.
working principle
Because the hardness of water is mainly formed and expressed by calcium and magnesium, cation exchange resin (soft water device) is generally used to replace ca2+, mg2+ (the main component of scale formation) in water. With the increase of ca2+, mg2+, the efficiency of resin to remove ca2+, mg2+ is gradually reduced.
When the resin absorbs a certain amount of calcium and magnesium ions, it is necessary to regenerate. The regeneration process is to wash the resin layer with salt water in the salt tank, and replace the hardness ions on the resin. With the waste liquid discharged from the tank, the resin will resume the softening exchange function.
Because the hardness of water is mainly formed by calcium and magnesium and the principle of water hardness is mainly formed by calcium and magnesium and the principle of sodium ion exchange softening treatment is to exchange raw water through sodium cation exchange resin, and exchange the hardness components ca2+, mg2+ in water with na+ in the resin, and absorb ca2+, mg2+ in water to soften water.
Workflow
The five processes are working (sometimes called water production, the same below), backwashing, salt absorption (regeneration), slow flushing (replacement), and quick flushing. All processes of different softened water equipment are very close, but there may be some additional processes due to the different actual processes or the need of control. Any softened water equipment based on sodium ion exchange is developed on the basis of these five processes (among which, the automatic softener will increase the process of brine reinjection).
Backwash: after a period of operation, the equipment will intercept a lot of dirt brought by raw water on the upper part of resin. After removing these pollutants, the ion exchange resin can be fully exposed, and the regeneration effect can be guaranteed. The backwash process is that water is washed from the bottom of the resin and out of 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): the process of injecting brine into resin tank body. The traditional equipment is to inject salt water with salt pump. The fully automatic equipment is to use special built-in injector to inhale salt water (as long as there is certain pressure for water inlet). In the actual work process, the regeneration effect of brine flowing through the resin at a slower speed is better than that of soaking resin with salt water alone. Therefore, the softened water equipment is regenerated by the method of slow flow of brine through resin. This process generally takes about 30 minutes, and the actual time is affected by the amount of salt used.
Slow flushing (replacement): after the brine flows through the resin, the process of washing all the salt in the resin slowly with the same flow rate is called slow flushing. Because there are still a lot of calcium and magnesium ions on the functional groups in the washing process are exchanged by sodium ions, according to the 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, i.e. about 30 minutes.
Quick flushing: in order to thoroughly wash the remaining salt, the resin shall be washed with raw water at a flow rate close to the actual work. The final effluent of this process shall be soft water up to standard. In general, the rapid flushing process is 5-15 minutes.
application
Different application choose different soft water treatment equipment
1. Application scope of softened water equipment:
① Heating
② Cooling water supplement
③ Process water
④ Steam boiler
⑤ Iron and steel smelting
⑥ Chemical pharmaceutical
2. System water consumption time required by the industry
The water consumption time of the system is: water consumption per hour, average value and peak value. Equipment can be selected according to the water supply time. If continuous water supply is not needed, the equipment of single valve and single tank can be selected; if continuous water supply is needed, double bed centralized control or double control double bed series softened water treatment device shall be selected.
3. Hardness of water source
The water production period of the same type of water softener with hard water quality must be reduced relatively, and the water yield is lower, which leads to frequent regeneration of softened water equipment, thus reducing the service life of resin. In this case, larger soft water softeners should be selected to increase the volume of resin.
Selection of softened water equipment
① Controller: it is divided into automatic control and manual control. The choice of brand can be imported or domestic.
② Resin tank: the tank material of softener is divided into glass steel, carbon steel and stainless steel.
③ Equipment control mode: one is that the preparation water reaches the set value and is automatically reduced, called flow type; it is applicable to all softened water treatment equipment of water supply system. The second is the time-based control regeneration measurement method, called time type; suitable for water supply system with stable water volume, 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 double bed: supply water at the same time, and regenerate alternately.
Multiple control several beds: more than three softened water resin tanks are used in parallel, which is suitable for large water supply system.
It can be widely used in softening the makeup water of steam boiler, hot water boiler, exchanger, evaporation condenser, air conditioning, direct combustion engine and other systems. It can also be used for the treatment of domestic water such as hotels, hotels, office buildings, apartments, home and other domestic water, and softened water treatment in food, beverage, wine making, laundry, printing and dyeing, chemical industry, medicine and other industries.
Technical index
1. water inlet pressure: 0.2-0.5mpa
2. raw water hardness: < 12mmol / L (when the hardness of raw water is more than 8mmol/l, special design shall be made according to the water quality in different regions)
3. water hardness: < 0.03mmol/l (up to the requirements of gb1576-2001 national water quality standard for low pressure boiler);
4. the salt content of raw water is less than 1500mg/l, turbidity is less than 5 iron ion ＜ 0.3mg/l
5. power supply: ~220v, 50Hz
6. salt consumption is less than 100g / g equivalent (related to the hardness of raw water);
7. water consumption ＜ 2%; power consumption ＜ 50W fully automatic softening
