Central air-conditioning circulating cooling water system after running for some time will face corrosion, scaling and biological slime adhesion of the three major hidden dangers, resulting in a reduction in the efficiency of heat transfer, increase in energy consumption, equipment corrosion, pipeline clogging or leakage and a series of faults such as hidden dangers, to shorten the life cycle of the equipment. At present, there are a variety of ways to eliminate these hidden problems, such as ozone, ultra-low-frequency vibration method and chemical purification method (adding scale inhibitors, corrosion inhibitors and sterilization - algaecide). The latter is the most commonly used, a one-time low investment in equipment, but there are certain requirements for the addition of chemicals, such as the right amount, uniform, continuous or timed, otherwise it may not achieve the desired results, or increase operating costs. Practice shows that: the use of automatic dosing technology and complete sets of equipment is to improve equipment efficiency, extend the service life, reduce operating costs, strengthen the management of effective means.
It is necessary to point out that the automatic dosing ≠ dosing pump + medicine box. Although the metering pump is a pre-set speed in accordance with the operation of electromechanical equipment, can be replaced to a certain extent manual operation. However, the metering pump + medicine box is only a combination of automatic control systems in the implementation of a combination of actuators, and other types of actuators (such as electric / pneumatic control valves, frequency converter speed controller, etc.) is different. 'Automatic dosing' is actually the industry to add chemical reagents to remove impurities in the water treatment process to achieve automated operation of the common name. For example: neutralization process pH control and acid / alkali automatic dosing, flocculation - precipitation process turbidity control and flocculant automatic dosing, boiler water dissolved oxygen control and deoxidizer automatic dosing, water disinfection process residual chlorine control and sodium hypochlorite / chlorine dioxide automatic dosing, circulating coolant water concentration multiplier to maintain the scale - corrosion inhibitors, biocides and algaecides automatic dosing, and so on. Although the above typical unit operation automation is inseparable from the 'metering pump + medicine box', but the key technology is the designer selected 'control algorithm' (control mode / control law) and the corresponding measurement and control equipment, software and its integration program. Shanshui environmental protection machinery production dosing device, air conditioning cooling circulating water dosing device.
Circulating cooling water dosing scale and corrosion inhibitors, bactericides and algaecides and maintain the optimal concentration rate is a very complex issue. Because the circulating water on the equipment and pipeline corrosion and fouling, is a long, complex chemical/physical-chemical process, the quantitative relationship between the dosage of pharmaceuticals and corrosion, structural velocity is not yet a practical mathematical model. In recent years, on-line monitoring of fouling and corrosion rate of instrumentation and devices have been introduced and gradually adopted, which is indeed very meaningful for management work, but how to measure the results and dosage associated with the same no mature experience to learn from. In view of this, the current automatic dosing system design and selection, but also only according to experience 'symptomatic', the introduction of a number of low-cost, 'foolproof' multi-functional dosing equipment for users to select.
Two, process requirements
For the cooling tower of the open circulating cooling water system, in addition to dosing to achieve corrosion inhibition, scale inhibition, sterilization and algaecide effect, but also need to take into account due to evaporation, splash escape and constant loss of water, making the circulating water soluble solids and a variety of impurities and pollutants continue to be concentrated, thus affecting the efficiency of the heat exchange, the need for the appropriate amount of drainage and supplemental fresh water to maintain the circulating water body. Supplementary fresh water to maintain the concentration of soluble solids and impurities in the circulating water body at the appropriate level, and strive to operate the water system in the best technical and economic indicators. The economic and technical indicators of the relationship between the quality and quantity of supplementary water and discharge water are usually characterized by the 'concentration factor'. Increase 'concentration times' can reduce the amount of sewage, is conducive to saving water resources, but the water quality deteriorates, affecting the heat exchange efficiency and scale - corrosion inhibition; reduce 'concentration times' is to improve the water quality, heat exchange effect is good, but the amount of sewage, water consumption increases, contrary to the water conservation policy. It is contrary to the water conservation policy. Theoretical analysis and experiments show that keep the 'concentration times' in 2.5 ~ 3.5 between the more appropriate, but depending on the specific environment, technology and water quality conditions for appropriate adjustment. It can be seen that the economic operation and maintenance of air-conditioning circulating cooling water system, in addition to setting the quantitative dosing equipment, should also be set up 'concentration times' automatic maintenance system.