Understand the central air conditioning cooling circulating water

one. The problem of central air conditioning cooling circulating water:

During the operation of the open cooling tower, the circulating cooling water in the system has a lot of contact with the air. On the one hand, CO2 in the water escapes into the air, and the equilibrium state of carbonic acid in the water is destroyed. On the other hand, dissolved oxygen is brought into the cooling water, which causes the water quality to be unstable. Scale and corrosion will be produced in the system. At the same time, organic matter and microorganisms in the air dust will also be brought into the water, accumulating and multiplying continuously. The above-mentioned scale, corrosion and biological sludge are not isolated, but are interrelated and affect each other. For example, salt scale and dirt are often combined together, and scale and sludge can cause or aggravate corrosion. Therefore, the main task of cooling circulating water treatment is to eliminate or reduce the hazards of scaling, corrosion and biological slime to ensure the efficiency and service life of the entire circulating water system.

two. The current status of water treatment in the cooling cycle system of the central air-conditioning project in Shanghai:

The circulating water treatment of the air conditioning cooling water system has always been an issue of debate and discussion. The current domestic situation is:

1. No treatment or simple blowdown is used to control scaling or corrosion.

2. The supplemental water is softened to control the quality of the circulating water.

3. An electrostatic water processor is added to the cooling water system to prevent scale, descale, sterilize and kill algae.

4. Add chemicals (scaling, corrosion, sterilization, and algae) to the cooling water system to control scaling, corrosion and microbial growth.

three. Comparison of several methods:

1. Operation without drug administration, on the surface, no serious problems have been seen in a short period of time. In fact, after two to three years, the consequences of this kind of wrong operation will be clearly exposed, and serious irreversible accidents will be caused, such as waste discharge alone.

2. Take softening treatment to remove Ca2+ and Mg2+ ions. Practice has shown that it not only brings large initial investment and high operating costs, but also causes corrosion, scaling and microbial growth of equipment and pipelines. The reason is very simple. Due to the decrease of Ca2+ and Mg2+ ions in the water, the corrosion of metals by dissolved oxygen, CO2 and chloride ions in the water promotes the buffering effect. The iron in the water and the dissolved oxygen have an autocatalytic reaction to produce ferrous hydroxide. In the presence of dissolved oxygen Bottom, ferrous hydroxide forms Fe2O3·nH2O, or rust, at an appropriate temperature. The actual measurement shows that the corrosion rate of carbon steel in tap water in Beijing is 1.12mm/α, and the corrosion rate in softened water is 3.27mm/α. The Fe2O3 content in the analysis of corrosion products and scale samples accounts for 77.6%.

3. Electrostatic water processor is a water quality control method that has been adopted in the central air-conditioning cooling water circulation system in recent years. It is a physical function that uses electrostatic fields for water treatment. This kind of water processor manufacturer claims that it can prevent scale, remove scale, and has a significant sterilization effect. But judging from the test results and user feedback, the descaling effect is average, and the corrosion inhibition and sterilization effects have not changed after testing. In addition, the equipment is expensive.

4. Add anti-scaling, corrosion-inhibiting, anti-bacterial and algaecide agents in the circulating cooling water system to inhibit scaling, corrosion and the reproduction of microorganisms. The function of anti-scaling is to prevent the formation of CaCO3 nuclei and prevent the growth of CaCO3 crystals. , Disperse CaCO3 crystals to prevent aggregation. Corrosion inhibition includes the blocking effect on iron ions and the dispersion effect on ferrous hydroxide. This processing method is a relatively complete and mature processing method at home and abroad.

four. Current problems in central air conditioning water treatment:

1. Large amount of sewage

2. The cooling tower packing is easy to scale

3. A large amount of supplemental water causes an increase in costs