In daily life, we often observe that the inner walls of kettles develop scale after prolonged use. Why does this happen? The reason is that the water we use contains various inorganic salts, such as calcium and magnesium salts. These salts are invisible to the naked eye in water at room temperature, but when heated and boiled, many calcium and magnesium salts precipitate out in the form of carbonates, adhering to the kettle walls and forming scale. The content of calcium and magnesium ions in water is typically measured using the "hardness" index. One degree of hardness corresponds to 10 milligrams of calcium oxide per liter of water. Water with less than 8 degrees is called soft water, while water exceeding 17 degrees is classified as hard water. Water with hardness between 8 and 17 degrees is considered moderately hard. Rainwater, snowmelt, river, lake, and stream water are all soft water, whereas spring water, deep well water, and seawater are hard water.
Let's take another look at the differences between softened water and other types of water. Raw water refers to untreated water. Broadly speaking, water before entering the water treatment process is also called the raw water for that treatment. For example, water delivered from the source to the clarification tank for treatment is termed raw water.
Water softening refers to the process of removing or reducing the hardness (primarily calcium and magnesium ions) in water to a certain extent. During this process, only the hardness is reduced, while the total salt content remains unchanged.
Desalinated water refers to water from which salts (primarily strong electrolytes soluble in water) have been removed or reduced to a certain extent. Its conductivity typically ranges from 1.0 to 10.0 µS/cm, resistivity (at 25°C) is (0.1 to 1.0) × 10^6 Ω·cm, and salt content is 1 to 5 mg/L.
Pure water refers to water from which strong and weak electrolytes (such as SiO2, CO2, etc.) are removed or reduced to a certain extent. Its conductivity typically ranges from 1.0 to 0.1 µS/cm, with resistivity (1.0 to 10.0) × 10^6 Ω·cm. The salt content is less than 1 mg/L.
Ultrapure water refers to water in which conductive media are almost completely removed, along with non-ionized gases, colloids, and organic substances (including bacteria), to an extremely low level. Its conductivity typically ranges from 0.1 to 0.055 µS/cm, resistivity (at 25°C) exceeds 10×10⁶ Ω·cm, and salt content is less than 0.1 mg/L. Theoretically, ideal pure water has a conductivity of 0.05 µS/cm and a resistivity (at 25°C) of 18.3×10⁶ Ω·cm.
What is water softening treatment? It involves using strongly acidic cation resin to remove calcium and magnesium ions from raw water, and after filtration by this water softening device, the resulting feedwater for boilers becomes highly purified and low-hardness softened water suitable for boiler use.
Working Principle of Ion Exchange Method: Specific cation exchange resins are used to replace calcium and magnesium ions in water with sodium ions. Due to the high solubility of sodium salts, the formation of scale caused by temperature increases is effectively prevented.
Features and Effects: The effects are stable and accurate, with mature technology. It can reduce hardness to zero.
Scope of Application: Used in various fields such as catering, food, chemical industry, pharmaceuticals, as well as in applications like air conditioning and industrial circulating water. Currently the most commonly adopted standard method.
Electromagnetic method: By adding a certain electric or magnetic field to water to change the characteristics of ions, the deposition rate and physical properties of calcium carbonate (magnesium carbonate) are altered to prevent the formation of hard scale.
Characteristics 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 usage time and distance of the treated water are limited to a certain extent.
Scope of application: It is mainly used for the treatment of commercial (such as central air conditioning) circulating cooling water, and cannot be applied to industrial production and boiler feedwater treatment. Membrane separation 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.
Characteristic effect: The effect is obvious and stable, and the treated water has a wide range of applications. There are high requirements for inlet pressure, and equipment investment and operating costs are also high.
Scope of application: Generally less used for specialized softening treatment.
Lime method: Add lime to water.
Characteristic effect: It can only reduce the hardness to a certain range.
Scope of application: Suitable for high hardness water with large flow rates.
Dosing method: Adding a specialized scale inhibitor to water can change the binding characteristics of calcium and magnesium ions with carbonate ions, thereby preventing the precipitation and deposition of scale.
Characteristic effect: Less one-time investment, wide adaptability. When the water volume is soft and large, the operating cost is relatively high.
Scope of application: Due to the addition of chemical substances, the application of water is greatly limited and generally cannot be used for drinking, food processing, industrial production, and other purposes. It is also rarely used in the civilian field.
Softening water equipment workflow and work requirements 1) Softening water equipment workflow
There are five processes: work (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 differences in 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, the fully automatic softening water equipment will increase the saltwater re injection process).
Backwash: 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 when water is washed in from the bottom of the resin and out from the top, which can wash away the dirt intercepted at the top. This process usually takes about 5-15 minutes.
Salt absorption (regeneration): The process of injecting salt water into a resin tank. Traditional equipment uses a salt pump to inject salt water, while fully automatic equipment uses a dedicated built-in sprayer to suck in salt water (as long as the inlet water has a certain pressure). In practical work, the regeneration effect of salt water flowing through the resin at a slower speed is better than simply soaking the resin in salt water. Therefore, softening water equipment adopts the method of slow flow of salt water through the resin for regeneration, which generally takes about 30 minutes. The actual time is affected by the amount of salt used.
Slow flushing (displacement): After flowing salt water 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. Due to the fact that a large number of calcium and magnesium ions on functional groups are still exchanged by sodium ions during this flushing process, according to practical experience, this process is the main process of regeneration, so many people call this process displacement. This process is generally the same as the salt absorption time, which is about 30 minutes.
Quick flushing: In order to thoroughly flush away residual salt, a flow rate similar to actual work should be used to flush the resin with raw water. The final effluent of this process should be soft water that meets the standard. Generally, the fast flushing process takes 5-15 minutes.
2) Technical specifications and working requirements for softened water equipment: Inlet water pressure: 0.18-0.6Mpa Working temperature: 1-55 ℃ Source water hardness:<8mmol/L Operating mode: automatic/manual Outlet hardness: ≤ 0.03mmol/L Regenerator: NaCl Regeneration mode: co current/counter current Exchange agent: 001 * 7 Strong acidic 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 wasted fuel. When the boiler forms scale, a boiler with a working pressure of 1.4 MPa will form 1 millimeter of scale, which will waste 8% of fuel.
2. Softening water equipment improves thermal efficiency and reduces output. When there is scale on the evaporation surface of the boiler, 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 scaling occurs due to improper water treatment, reducing the boiler's evaporation capacity by one-third, and the automatic operation line cannot operate due to insufficient gas supply
4. The application of softened water equipment reduces the risk of accidents caused by water scale in boilers, which accounts for more than 20% of the total number of boiler accidents. This not only causes equipment damage, but also threatens personal safety. And the infrastructure and operating costs of water treatment account for a quarter of all cost savings.
Softening water treatment equipment, as the name suggests, refers to equipment that reduces the hardness of water. It mainly removes calcium and magnesium ions from water. Simply put, it is a device that reduces the hardness of water. Its main functions include removing calcium and magnesium ions from water, activating water quality, killing bacteria and algae, and preventing scaling. Softening equipment cannot reduce the total salt content in the 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 equipment systems.
Working principle: As 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 components that form scale) in water. As the Ca2+and Mg2+in the resin increase, the efficiency of removing Ca2+and Mg2+gradually decreases.
After the resin absorbs a certain amount of calcium and magnesium ions, it must be regenerated. The regeneration process is to rinse the resin layer with saline solution in the salt tank, replacing the hardness ions on the resin. The resin is then discharged from the tank with the regeneration waste liquid, and the softening exchange function of the resin is restored.
Due to the fact that 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 a sodium type cation exchange resin, allowing the hardness components Ca2+and Mg2+in the water to exchange with Na+in the resin, thereby adsorbing Ca2+and Mg2+in the water and softening the water.
The workflow includes five processes: water production, 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 differences in 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, the fully automatic softening water equipment will increase the saltwater re injection process).
Backwash: 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 when water is washed in from the bottom of the resin and out from the top, which can wash away the dirt intercepted at the top. This process usually takes about 5-15 minutes.
Salt absorption (regeneration): The process of injecting salt water into a resin tank. Traditional equipment uses a salt pump to inject salt water, while fully automatic equipment uses a dedicated built-in sprayer to suck in salt water (as long as the inlet water has a certain pressure). In practical work, the regeneration effect of salt water flowing through the resin at a slower speed is better than simply soaking the resin in salt water. Therefore, softening water equipment adopts the method of slow flow of salt water through the resin for regeneration, which generally takes about 30 minutes
Slow flushing (displacement): After flowing salt water 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. Due to the fact that a large number of calcium and magnesium ions on functional groups are still exchanged by sodium ions during this flushing process, according to practical experience, this process is the main process of regeneration, so many people call this process displacement. This process is generally the same as the salt absorption time, which is about 30 minutes.
Quick flushing: In order to thoroughly flush away residual salt, a flow rate similar to actual work should be used to flush the resin with raw water. The final effluent of this process should be soft water that meets the standard. Generally, the fast flushing process takes 5-15 minutes.
Choose different soft water treatment equipment for different applications: 1. Scope of application of soft water equipment: ① Heating ② Cooling water replenishment ③ Process water ④ Steam boiler ⑤ Steel smelting ⑥ Chemical and pharmaceutical industries
2. The required system water usage time for the industry includes hourly water usage, average value, and peak value. Equipment can be selected based on 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 required, it is necessary to choose a dual bed centralized control or dual control dual bed series softened water treatment device.
3. The hardness of the water source is the same as that of the same type of water softener. If the water quality is harder, the water production cycle will inevitably be relatively reduced, resulting in lower water production. This leads to frequent regeneration of the softened water equipment, thereby reducing the service life of the resin. In this case, it is necessary to choose a larger model of water softener and increase the resin volume.
2、 Softening water equipment selection ① Controller: divided into automatic control and manual control. The choice of brand can be either imported or domestically produced. ② Resin tank: The material of the softened water device tank body is divided into fiberglass, carbon steel, and stainless steel. ③ Equipment control form: One is the automatic restoration when the water preparation reaches the set value, which is called flow type; Suitable for all softened water treatment equipment in water supply systems. The second method is to control the regeneration measurement based on time, which is called time type; Suitable for water supply systems with stable water flow, 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 twin bed: alternate water supply, one in use and one as backup. Dual control twin bed: alternate water supply, one in use and one as backup. Dual control dual bed: simultaneous water supply, alternating regeneration. Multiple control beds: Three or more softened water resin tanks are used in parallel, suitable for large-scale water supply systems. It can be widely used for softening the supply water of steam boilers, hot water boilers, exchangers, evaporative condensers, air conditioners, direct fired engines and other systems. It can also be used for the treatment of domestic water in hotels, restaurants, office buildings, apartments, homes, and other industries, as well as for the treatment of softened water in food, beverage, brewing, laundry, printing and dyeing, chemical, pharmaceutical and other industries.
Technical indicators: 1. Inlet pressure: 0.2~0.5Mpa 2. Raw water hardness:<12mmol/L (when the raw water hardness is>8 mmol/L, special design should be made according to the water quality of different regions) 3. Outlet water hardness:<0.03mmol/L (meeting the requirements of the National Low pressure Boiler Water Quality Standard GB1576-2001); 4. The salt content of the raw water is less than 1500mg/L, the turbidity is less than 5, and the iron ion concentration is less than 0.3mg/L. 5. Power supply:~220V, 50HZ. 6. Salt consumption is less than 100g/gram equivalent (related to the hardness of the raw water); 7. Water consumption<2%; Main technical specifications for fully automatic softened water desalination equipment with power consumption<50W: 1. "Technical specifications for construction and acceptance of electric power construction" 2. "Quality acceptance and evaluation standards for thermal power construction" 3. JB/T74-94 "Technical conditions for pipeline flanges" 4. Sandblasting and rust removal should comply with GB8923 5, DL/T5054-1996 "Technical specifications for design of steam and water pipelines in thermal power plants" 6. GB/T18300-2001 automatic control sodium ion exchanger technical conditions 7. GB 1576-2001 low pressure boiler water quality 8. GB 5462-199 industrial salt 9. GB/T 13659-1992 001 * 7 strong acidic styrene cation exchange resin 10. JB/T 2932-1999 water treatment equipment technical conditions 11. GB/T 13384-1992 electromechanical General technical specifications for product packaging
Equipment classification includes industrial water treatment equipment, drinking water treatment equipment, filling equipment, and water treatment accessories.
Industrial water treatment equipment, large-scale reverse osmosis equipment for power plants, ultra pure water equipment for industries such as medicine and electronics, pure water equipment for flower and fruit irrigation, dosing equipment, boiler softening water equipment;
Drinking water treatment equipment, purified water equipment for the food and beverage industry, purified water and mineral water equipment for 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, brush barrel and cap removal machines;
Water treatment accessories include filter media, filter cartridges, booster pumps, reverse osmosis membranes, membrane housings, precision filters, flow meters, pressure gauges, ozone generators, ultraviolet sterilizers, scale inhibitors, etc.
