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Process Flow of Membrane Treatment System for Softening Water Equipment
In the water vapor circulation system of thermal power plant, there are strict water quality requirements for water used as working medium of thermal system and equipment quality of cooling dielectronics industry. For example, the feed water of high pressure boiler requires not only low hardness, but also very little dissolved oxygen, solid content and organic matter content. Water that does not meet the feed water standard will make the power plant set up. In order to operate safely and economically, reverse osmosis desalting water treatment system, double bed, mixed bed ion exchange high purity water treatment system and ultra-pure water treatment equipment are needed to treat the super high pressure boiler feed water in thermal power plants. To this end, the quality indicators of various kinds of water used in thermal power plants have been formulated.
The recharge water of power plants often comes from surface water, groundwater, coastal and freshwater-scarce areas. Seawater is often used as the recharge water source. These water must be treated by high purity water equipment such as precipitation, filtration, desalination and degassing. Only when seawater is used as the recharge water source, the desalination equipment can be softened to enter the water circulation system of power plants.
In membrane treatment system, hollow fibers with diameter of 1 mm are usually used to remove suspended substances and colloids from raw water. The biggest problem of UF used as pretreatment is membrane fouling and blockage of membrane pore. Therefore, pre-filters are often set in front to remove large-sized suspended substances and flocculants, such as PAC, are added before pre-filtration. Polypropionic acid can improve the quality of filtration water and reduce membrane resistance. The dissolved oxygen requirement for power plant boiler feed water system is generally less than 0.3mg/L, so the degassing film should be operated at a vacuum of less than 5.33Kpa (40TORR).
Typical process flow:
· Pretreatment-reverse osmosis-electrodeionization (EDI) -ion EXCHANGE DESALINATION
· Pretreatment-reverse osmosis equipment
· Pretreatment-reverse osmosis-ion EXCHANGE DESALINATION
AHRO series medium and high pressure boiler feedwater softening equipment is suitable for the treatment of boiler feedwater in thermal power plants and large and medium-sized industrial and mining enterprises. With the world's most advanced reverse osmosis membrane components, pressure vessels and other equipment, coupled with reasonable and pre-treatment and post-treatment equipment, it can produce water that meets the supply water standard of high-pressure boiler in the power industry. The control system is programmed by industrial computer, which can automatically start and stop, add medicine and flush, and automatically monitor various operating parameters for production management.
Equipment performance:
The imported low-roll composite reverse osmosis membrane with high desalination rate and low operating pressure has excellent water quality, low operating cost and long service life. High efficiency, low noise.
Imported on-line water conductance meter for raw water and product water, PH meter can monitor water quality at any time.
Imported on-line product water, concentrated water flowmeter, can monitor product water volume and system recovery at any time.
It is equipped with automatic circulating cleaning system for cleaning after membrane fouling.
The quick-impact valve regularly washes the surface of the membrane, reduces the speed of membrane fouling and prolongs the service life of the membrane.
Softening water method:
Soft water: Natural water containing only a small amount of soluble calcium and magnesium salts, or hard water treated by softening water equipment. Natural soft water generally refers to river water, River water, Lake (freshwater lake) water. Hard water treated by softening refers to the softened water obtained when the content of calcium salt and magnesium salt is reduced to 1.0-50 mg/l. Although boiling can turn temporary hard water into soft water, it is extremely uneconomical to use this method to treat large amounts of water in industry. The methods of softening water are as follows:
(1) Lime-soda method.
Firstly, the hardness of the water was determined, and then the calcium hydroxide and sodium carbonate were added quantitatively. Calcium and magnesium ions in the hard water precipitated and precipitated.
Ca(HCO_3)2+Ca(OH)22CaCO_3+2H_2O
Mg(HCO_3)2+2Ca(OH)2Mg(OH)2_+2CaCO_3_+2H_2O
CaSO4 + na2co3caco3 ↓ + Na2SO4
(2) Phosphate soft water method.
For boiler water, sodium phosphite (NaPO3) can be added as a water softener, which forms a complex with calcium and magnesium ions. When boiling water, calcium and magnesium will not precipitate in the form of precipitation, thus no scale will be formed. This method is not suitable for the softening of drinking water.
(3) Ion exchange method.
Zeolite and ion exchanger are insoluble in water, but sodium ions and hydrogen ions can exchange with calcium and magnesium ions in hard water, so that calcium and magnesium ions are adsorbed by zeolite, artificial zeolite and ion exchanger and removed. Zeolites and ion exchangers that have failed after long-term use can be reused through regeneration, so this method is economical and advanced soft water method.
[Benefits of softening water]
In our daily life, we often see scales on the inner wall of the kettle after a long time. What's the reason? There are many inorganic salts in the water we used, such as calcium and magnesium salts. These salts can not be found by naked eyes in water at room temperature. Once they are heated and boiled, a lot of calcium and magnesium salts are precipitated by carbonate, which forms scale close to the pot wall. We usually express the content of calcium and magnesium ions in water by the index of hardness. Hardness of 1 degree 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 medium hard water. Rain, snow, rivers, rivers and lakes are soft water, while spring water, deep well water and sea water are hard water.
Some water with high content of calcium and magnesium ions has no scale formation. This is because these calcium and magnesium ions exist in the form of chloride salts. They are soluble, so they can not precipitate when heated.
The hardness of water has a great influence on daily life. For example, when the hardness of water is large, washing clothes does not bubble; when living in a different place, because the hardness of drinking water is not suitable, the symptoms of acclimatization may occur; scaling in the kettle will reduce the thermal conductivity of the kettle; scaling in industrial boilers can cause explosion accidents. Therefore, the hardness of water should be properly controlled in both domestic and industrial water use. Drinking soft water (pure water) is prone to cardiovascular and cerebrovascular diseases, and drinking hard water (mineral water) is prone to kidney stones.
Author: Hangzhou Water Shield Technology Co., Ltd.
Website: http://www.zjhzsd.com/
Key words: water equipment in electronic industry, desalination equipment
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