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How to solve the circulating water running the main problems

2016-10-07 02:39:32

Industrial circulating cooling water system in the course of running, due to water evaporation, wind loss and so on to make the circulating water concentration, which contains excessive salt, anion and cation increase, pH significantly change, resulting in deterioration of water quality, and circulating water Temperature, pH value and nutrient content are beneficial to the propagation of microorganisms. The sufficient sunlight on the cooling tower is the ideal place for algae growth. The scaling control and corrosion control, microbial control, etc., the inevitable need for recycling water treatment.

The main problems in the process of circulating water running:

(1) Scale: As the circulating water in the cooling process of continuous evaporation, so that the salt concentration in water continues to increase, more than the solubility of certain salts and precipitation. Common are calcium carbonate, calcium phosphate, magnesium silicate and other dirt. Scale texture is relatively dense, greatly reducing the heat transfer efficiency, 0.6 mm thick scale on the heat transfer coefficient decreased by 20%.

(2) dirt: dirt mainly by the organic matter in the water, microbial colonies and secretions, sediment, dust and other composition, dirt texture soft, not only reduces the heat transfer efficiency but also caused corrosion under the scale and shorten equipment life.

(3) corrosion: the corrosion of circulating water on the heat transfer equipment, mainly electrochemical corrosion, the causes of equipment manufacturing defects, adequate oxygen in water, corrosive ions in water (Cl-, Fe2 +, Cu2 +) and microbial secretion of mucus Generation of dirt and other factors, the consequences of corrosion is very serious, without control of a very short time even if the heat exchanger, water pipeline equipment scrapped.

(4) microbial slime: because the circulating water dissolved in sufficient oxygen, the appropriate temperature and the conditions of enrichment, it is suitable for microbial growth and reproduction, if not promptly control will lead to deterioration of water quality, smelly, black, cooling tower Sticky dirt deposition or even blocked, cooling cooling effect dropped significantly, equipment corrosion increased. Therefore, circulating water treatment must control the propagation of microorganisms.

Microbial hazards

Microorganisms in circulating cooling water come from two aspects. First, the cooling tower in the water evaporation process requires the introduction of a large number of air, microbes with air into the cooling water, the second is the cooling water system will have more or less added water, these microbes also with the supplementary water into the cooling water System.

Algae in the sunlight, and water carbon dioxide, bicarbonate and other carbon source photosynthesis, absorption of carbon as nutrients and release oxygen, so when the algae multiply, it will increase the dissolved oxygen content in the water is conducive to oxygen Of the depolarization, the corrosion process is thus accelerated. Microorganisms in the circulating water system in a large number of breeding, will make the water color black, the occurrence of stench, pollute the environment. At the same time, will form a large number of slime cooling tower to reduce the cooling efficiency, wood deterioration rot. Slime deposited in the heat exchanger, so that the heat transfer efficiency and head loss increases, deposited on the metal surface of the sludge will cause serious corrosion under the scale, and it also cut off the corrosion inhibitor on the role of metal, so that Pharmacy can not play the necessary corrosion and scale inhibition. In addition to microbial sludge will accelerate corrosion under the scale, some bacteria in the metabolic process, biological secretions will be directly on the metal corrosion. All of these problems lead to long-term safe operation of circulating water systems, affecting production, resulting in serious economic losses, so the hazards of micro-organisms and scale, corrosion on the cooling water system is as serious as harm, and even can be compared, Microbiological hazards are paramount.

The trends of microorganisms in the circulating water can be measured by the following chemical analysis items:

(1) residual chlorine (free chlorine) Chlorine sterilization should pay attention to residual chlorine occurs time and residual chlorine, because the microbial breeding serious cycle of water consumption will greatly increase the chlorine consumption.

(2) Ammonia circulating water generally does not contain ammonia, but because the process medium leakage or inhalation of ammonia in the water will also contain ammonia, this time can not be taken lightly, in addition to actively looking for ammonia leakage, but also pay attention to whether the water Containing nitrite, the water content of ammonia is preferably controlled at 10mg / l or less.

(3) NO2 - when the water containing ammonia and nitrite, it is said that the water has been nitrite bacteria will be converted to nitrite nitrite, then the circulating water system will become very difficult chlorine, chlorine consumption increased, Residual chlorine is difficult to achieve the target, the water content of the best control of NO2 - is less than 1mg / l.

(4) chemical oxygen demand of microorganisms in the water will cause serious COD increase, because bacteria increase the mucus of the water content of organic matter, so the analysis of chemical oxygen demand can be observed in the water changes in microbial trends, under normal circumstances the water COD is preferably less than 5 mg / l (KMnO4 method).

The harm caused by microorganisms in circulating water is very serious, if you want to take harm after the microbial measures are often less effective but also cost a lot of biocides and money. Therefore, it is necessary to thoroughly monitor the microbial condition of circulating cooling water beforehand.

Concentration of water

Circulating water concentration factor refers to the circulating water system in the operation process, due to water evaporation, wind loss and so on to make the circulating water concentration ratio (to make up water as a benchmark for comparison), it is an important measure of water quality control is important Comprehensive index. High concentration of water can reduce the amount of water treatment costs; but the concentration is too high, the tendency of the scaling of water will increase, the water concentration is low, water consumption, sewage volume are large and the effectiveness of water treatment agents are not fully into play; Scale control and corrosion control will increase the difficulty of water treatment agents will fail, is not conducive to microbial control, so the cycle of water concentration factor to have a reasonable control index.

Scale formation

In the circulating water system, the scale is formed by the supersaturated water-soluble components, water dissolved in a variety of salts, such as bicarbonate, carbonate, chloride, silicate, which dissolved in hydrogen carbonate Salts such as Ca (HCO3) 2, Mg (HCO3) 2

Most unstable, very easy to produce carbonates decomposition, so when the cooling water dissolved bicarbonate more, the water flow through the heat exchanger surface, especially the higher temperature surface, it will heat decomposition; water soluble phosphate And calcium ions, calcium carbonate will also produce precipitation; calcium carbonate and Ca3 (PO4) 2 are difficult to dissolve with the general salt is also different, the solubility is not increased with increasing temperature, but with the The temperature decreases. Therefore, these insoluble salts easily reach the supersaturation state in the heat transfer surface of the heat exchanger and crystallize in water, especially when the water flow speed is small or the heat transfer surface is rough, these crystal precipitates will be deposited on the heat transfer surface , The formation of the so-called scale, because these scale crystallization dense, relatively hard, also known as hard dirt, common scale components: calcium carbonate, calcium sulfate, calcium phosphate, magnesium salt, silicate.

Circulating water treatment technology

According to the characteristics of the enterprise circulating water system and process conditions, combined with local water quality characteristics, select the appropriate conditions for the operation of water treatment program, through dosing and other measures to control the circulating water indicators within a certain range of operation, both to ensure long-term production equipment Operation, but also improve the utilization of recycled water. The use of recycled water treatment technology, both to the enterprise to bring significant economic benefits, but also for the community to bring good social benefits. So the application of circulating water treatment technology is very necessary.

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