Central air conditioning scale and water treatment instructions and treatment

First, the cooling water system in the scale is how to form

The formation of scale and slag is a complex physical and chemical process, the process is divided into two steps:

The first step: salt impurities in the supersaturated water solution crystallization precipitation;

The second step: the crystallization of salt impurities attached to the metal surface to form scale, or suspended in the water to become water slag.

Cooling water due to continuous circulation, evaporation and concentration, resulting in salt impurities in the water over its solubility limit (i.e., solubility, also known as solubility product) and crystallization from the water.

Second, the cooling water system in the bacteria and algae is how to produce

Cooling water system temperature, PH value and nutrients are very suitable for the growth of bacteria and algae, cooling tower water collection plate and tower wall is a good environment for the survival and reproduction of bacteria and algae. Algae present in the soil and water will enter the cooling water system with the air and supplemental water to reproduce, affecting the quality of water. Most algae are blue-green in color.

Third, the water system corrosion type

Electrochemical corrosion: the main material of the water system pipe is carbon steel, its surface is not uniform, and the water is constantly O2 dissolved, when the carbon steel is immersed in water, the surface will form a number of tiny corrosion battery.

Acid corrosion: CO2 is more impurities in the water. The more CO2 in the water, the more H+ is generated (the lower the PH value of water), the more acidic water, the stronger the corrosive, thus destroying the carbon steel surface generated by the oxidized film caused by corrosion.

Corrosion under the scale: pipeline scaling, the microorganisms between the dirt layer and the pipe wall will be converted into acidic substances and gradually corrode the pipe wall, resulting in localized pitting and perforation of the pipeline.

Fourth, scaling, corrosion hazards

1, scaling will cause heat transfer tube heat transfer efficiency is reduced, resulting in poor air conditioning, energy consumption increased.

The main component of scale is bicarbonate, sulfate and so on. Carbonate scale coefficient of thermal conductivity is only 0.15% of the thermal conductivity of copper, the difference between the two is huge. Heat exchanger tube every increase of 1mm scale, will make the cooling capacity to reduce 20 ~ 40%, air conditioning energy consumption increased by 15 ~ 30%.

2, scale, rust residue, algae and other impurities, will clog the filter and heat exchanger tube, resulting in air conditioning ineffective, and even jump pumps, shutdown.

3, the system piping, heat exchanger tube wall corrosion, or even perforation, resulting in a shortened life expectancy, increasing the operation and maintenance costs. Due to the presence of corrosive ions in the system circulating water, and the inner wall of the pipeline are generally not treated, it is easy to corrode the inner wall. The source of this article refrigeration encyclopedia weibo public number.

4, a large number of bacteria breeding caused by disease (especially “legionella”), and generate slime caused by corrosion under the scale and microbial corrosion.

Cooling system in the sunlight to the parts of the algal bloom, sunlight is not part of the bacterial reproduction, generating slime covering the surface of the pipe wall to reduce the heat transfer effect, and cause corrosion and microbial corrosion under the scale. At the same time, if the bacteria are not killed in time to remove, but also easy to cause disease.
 

V. Scaling case

A company used 2 sets of units, with the increase of operating years, the cooling effect has not reached the design requirements. In order to clarify the reason for the decline in unit output, it was requested to conduct unit output test at a certain time.

During the test, the engineer found that the temperature difference between the upper part of the refrigerant differential pressure tube and the cooling water outlet temperature was about 8℃ (about 4℃ when there was no fouling), confirming that the condenser copper tube was seriously fouled. After opening the water cover, it was proved that the scaling was very serious and the condenser scale was more than 2mm.