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How to solve the problem of circulating water generated during the operation of the main

2016-09-23 02:44:46

Industrial cooling water system during operation, due to evaporation, wind damage and so the circulating water constantly concentrated salts contained therein exceeded, ions increases, pH value changes significantly, resulting in deterioration of water quality, and the circulating water temperature, pH and nutrients conducive to the propagation of microorganisms, cooling towers sufficient sunlight is an ideal place for the growth of algae. The scale control and corrosion control, microbial control and so on, the inevitable need for circulating water.

Recycled water generated during the operation of the main problems:

(1) Scale: Due to evaporation of the water circulating in the cooling process, so that the water constantly increasing salt concentration, exceeds the solubility of certain salts precipitated. Common are calcium carbonate, calcium phosphate, magnesium and other dirt. Scale comparative dense texture, greatly reducing heat transfer efficiency, 0.6 mm thick dirt on the heat transfer coefficient decreased by 20%.

(2) dirt: dirt mainly composed of organic matter in water, microbial colonies, and discharge, sediment, dust, dirt texture soft, not only reduces the heat transfer efficiency but also lead to corrosion under the scale, shorten equipment life.

(3) Corrosion: recycled water corrosion of heat transfer equipment, mainly electrochemical corrosion causes have equipment manufacturing defects, adequate water, oxygen, water, corrosive ions (Cl-, Fe2 +, Cu2 +) and microbial secretion of mucus by dirt and other factors resulting consequences of corrosion is very serious, uncontrolled short time even if the heat exchanger, water piping equipment scrapped.

(4) microbial slime: Because there are plenty of circulating water dissolved oxygen, suitable temperature and nutrient-rich conditions, it is suitable for microbial growth and reproduction, if not controlled will quickly lead to deterioration of water quality, smelly, black, a lot of cooling tower even sticky dirt deposits clogging the cooling heat dissipation dropped, equipment corrosion increased. So circulating water treatment is necessary to control the propagation of microorganisms.

Microbiological hazards

Circulating cooling water of microorganisms from two aspects. First, the process of evaporation of water in the cooling tower of the need to introduce a lot of air, microbes in the air into the cooling water, the second is to add water cooling water system will have more or less of microorganisms that are added with water into the cooling water system.

Algae in the sunlight, and will work with carbon dioxide, water, bicarbonate and other carbon sources from photosynthesis, absorb carbon and emit oxygen as a nutrient, therefore, when algal blooms will increase the dissolved oxygen content, conducive to oxygen depolarization, thereby accelerating the corrosion process. Microorganisms in circulating water systems multiply, make recycled water color black, the occurrence of odor, pollution of the environment. At the same time, it will form a large slime so that the cooling efficiency of the cooling tower is reduced, deterioration of wood rot. Slime deposited in the heat exchanger, the heat transfer efficiency and reduce head loss increases, deposited on the metal surface of slime can cause severe corrosion under the scale, but it also isolated the role of metal corrosion and scale inhibitors, so agents can not achieve the desired corrosion and scale performance. In addition to microbial slime will accelerate corrosion under the scale, but some bacteria in the metabolic process, but also on biological secretions direct metal corrosion. All of these issues lead to long-term safety of circulating water system can not operate, affecting production, causing serious economic losses, therefore, microbiological hazards and scale, corrosion of the cooling water system is the same as serious harm, or even can be said that compared with the three control microbiological hazards is paramount.

Microorganisms in water circulating through the following chemical analysis of trends in project measurement:

(1) Chlorine (free chlorine) time to pay attention to the amount of chlorine and chlorine occur when chlorinator, because it will make a large amount of earth circulating water consumption of chlorine increased microbial propagation serious.

(2) ammonia circulating water is generally not ammonia, but because the process medium leaks or inhalation of ammonia in the air when the water will also appear ammonia, then can not be taken lightly, in addition to actively look for the leak of ammonia, but also pay attention to whether the water containing nitrite, ammonia content in water is preferably controlled at 10mg / l or less.

When (3) NO2- occurs when water containing ammonia and nitrite, nitrite has been said that the water bacteria convert ammonia to nitrite, then the circulating water system chlorination will become very difficult to increase the amount of consumption of chlorine, chlorine is difficult to achieve the target, the best NO2- content in water is controlled to less than 1mg / l.

(4) the propagation of microorganisms in water chemical oxygen demand COD serious cause increased mucus secretion because the bacteria increases the organic matter content of the water, so by analyzing the chemical oxygen demand of microorganisms in water can be observed changes in the movements of water in normal circumstances COD is preferably less than 5mg / l (KMnO4 method).

Hazards caused by microorganisms in water circulating is very serious, and then if you want to take steps to cause harm in microorganisms are often less effective but also cost a lot of biocides and money. Therefore, prior comprehensive microbiological monitoring circulating cooling water situation is very necessary.

Concentrate multiples

Circulating water concentration ratio refers to the circulating water system during operation, due to evaporation, wind damage and so the circulating water continually concentrate magnification (to supplement the water as a benchmark to compare), which is a measure of the quality of an important water quality control comprehensive index. Concentration ratio is low, water consumption, sewage volume is large and the effectiveness of water treatment agent not full; high concentration ratio can reduce the amount of water, saving water treatment costs; but the concentration ratio is too high, scaling tendency of water will increase, scale control and corrosion control will increase the difficulty, water treatment chemicals will fail, it is not conducive to microbial control, so the circulating water concentration ratio have a reasonable control targets.

The formation of scale

In the circulating water system, scale is supersaturated water soluble components of the formation, a variety of dissolved salts, such as bicarbonates, carbonates, chlorides, silicates, of which the dissolved bicarbonate salts such as Ca (HCO3) 2, Mg (HCO3) 2

Most unstable, very easy to decomposition of carbonate, therefore, when the cooling water of dissolved bicarbonates more water flow through the heat exchanger surface, especially a hot surface, heat will break down; phosphate dissolved in water when calcium ions will also produce precipitation of calcium phosphate; calcium carbonate and Ca3 (PO4) 2, etc. are difficult solubility salts in general also different, not its solubility increases with temperature increase, but with the temperature rises. Thus, in the heat exchanger heat transfer surface, these insoluble salts easily reached saturation and crystallization water, especially when the small flow rate or heat transfer surface is rough, the crystalline precipitate will be deposited on the heat transfer surface , giving what is known scale, since these scale crystalline dense, relatively hard, hard scale is also known, is a common scale components: calcium carbonate, calcium sulfate, calcium phosphate, magnesium silicate.

Circulating water treatment technology

According to the characteristics and conditions of the business cycle water system, combined with the local water quality characteristics, select the appropriate treatment program enterprises operating conditions, by dosing and other measures to control the operation of the circulating water indicators within a certain range, both to ensure the long-period production equipment operation, but also improves the utilization rate of recycled water. Using a circulating water treatment technology, both to the enterprise bring significant economic benefits, but also for the community good social benefits. So circulating water treatment technology is very necessary.

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