Which mediums are easy to be polluted and damaged in the production of condenser evaporator

Which mediums are easy to be polluted and damaged in the production of condenser evaporator

In the process of industrial production, the condenser is a kind of non-stop refrigeration and heat exchange auxiliary equipment for a long time. Because of the different production requirements, the cooling and heat exchange medium used is also different. Often the heat exchanger (cold zone, condenser) , Evaporator) The most prone problem is the internal dirt clogging and the casing being corroded. Then, which production media are likely to cause similar problems?

　　1. Impurities dissolved in water in the state of ions or molecules are harmful

　　A. The main components of calcium salts in water are Ca(HCO3)2, CaCl2, CaSO4, CaSiO3, etc. Calcium salt is the main component that causes fouling of heat exchangers. Among them, CaSO4 is a kind of hard, fine crystalline scale with loose structure and low adhesion. It is a relatively soft sludge, separated from the water with fluidity, and it is easy to remove even if it adheres to the heated surface.

　　B. The main components of magnesium salt in water are Mg(HCO3), MgCl2, MgSO4, etc. After magnesium is dissolved in water, Mg(OH)2 precipitates after being decomposed by heat, and Mg(OH)2 is also sludge scale. MgCl2 and MgSO4 dissolved in water will cause acid corrosion of the metal wall due to hydrolysis when the water pH is less than 7.

　　C. Sodium salt mainly consists of NaCl, Na2SO4, NaHCO3, etc. NaCl does not generate scale, but the presence of free oxygen in the water will accelerate the corrosion of the metal wall; too high content of Na2SO4 will form salt on the accessories behind the evaporator, affecting safe operation; the effect of NaHCO3 in water on temperature and pressure It will decompose NaCO3, NaOH, CO2 and damage the metal grains.

　　 2. The harm of dissolved oxygen gas

　　 There are many reasons for the corrosion of heat exchangers, but the most serious and fastest corrosion is oxygen. In the atomic order table, the potential of iron is higher than that of hydrogen. In neutral water without oxygen, the iron atoms on the metal surface of the system lose electrons and become divalent ions (Fe-2e→Fe2+), Fe2+ ions and OH in the water. -Ions combine [Fe2++2OH-→Fe(OH)2] under the action of electrostatic attraction, and establish the following balance in water:

　　Fe2++2OH-=Fe(OH)2

　　 When there is oxygen in the water, Fe(OH)2 is further oxidized to precipitate insoluble iron hydroxide:

　　4Fe(OH)2+O2+2H2O→4Fe(OH)3↓

　　 Due to the precipitation of Fe(OH)3, the iron ions around the anode are transferred into the aqueous solution, which accelerates the progress of corrosion.

　　 It can be seen from the above reaction that water and oxygen are the necessary conditions for corrosion. The anode part is the corroded part, and the cathode part is the part where corrosion products accumulate. When the corrosion is basically uniform on the entire metal surface, the corrosion rate will not be very fast, so the harm is not great. This kind of corrosion is called general corrosion. When corrosion is concentrated on certain parts of the metal surface, it is called localized corrosion. The local corrosion rate is very fast and it is easy to rust through. Pitting corrosion is a common local corrosion in heat exchangers, so it is very harmful.

　　3. The harm of impurities in the colloidal state to the heat exchanger

　　A, iron compound The main component is Fe2O3, which generates iron scale. When the water contains more iron compounds, the water is often yellow.

　　B. Microorganisms As the water temperature, dissolved oxygen, nutrients, etc. of the air-conditioning cooling circulating water provide conditions that are conducive to the reproduction of microorganisms, microorganisms will multiply and multiply. Microorganisms come from the soil and the air. When the temperature of the cooling circulating water is high, the oxygen content will increase through aeration of the cooling tower, and phosphates and other agents are often added to the water, which are just the nutrients for the microorganisms. The cooling towers are mostly located Outdoors and sunlight are conducive to the growth of algae. The reproduction of microorganisms not only blocks the passage of the plates, but sometimes also blocks the pipelines, and also corrodes the metal.

　　C, sludge The sludge in the cooling circulating water comes from dust in the air and suspended solids in the supplementary water. During the convective exchange of air and water, a large amount of air is sprayed by circulating water in the tower, so that dust enters the water and gradually deposits in the heat exchanger with a lower flow rate.

　　D, sludge is mainly formed by the adhesion of microbial secretions with sediment, corrosion products, and bacterial and algae debris in the water. They are often attached to the wall of the heat exchanger and produce various organic acids, which can also cause corrosion.

　　 Therefore, the requirements for the water quality of the heat exchanger fluid are very important. In the operation and management, we should pay more attention to it and be equipped with some necessary anti-scaling and anti-corrosion equipment to extend the service life of the equipment.

　　 Based on the above points, everyone can judge the reason for the similar situation in the heat exchanger during the production process.