Application of Chlorine dosing system in the chilled water system
I. Common problems of chilled water system
As the water quantity of the chilled water system remains almost the same and the calcium and magnesium in the water will not increase due to the circulation, so its trend structure is not so serious. The problem of the system mainly lies in the dissolved oxygen corrosion because of the microcell formed by the carbon steel in the water. The process of corrosion reaction can be expressed as:
Ferric hydroxide is quite easy to be oxidized into red brown rust and this is the main reason for red water in the chilled water. In the open-type and spray-type chilled water system, as part of the system exposes to air or directly contact with air, the dissolved oxygen content in the system is very sufficient; while in the closed-type chilled water system, the dissolved oxygen will become insufficient due to the consumption caused by corrosion. Despite of this, there is still some dissolved oxygen left in the system, mainly coming through the valve, pipe joint and thrust pad of pump. Besides, though the chilled water system is seldom supplemented with water, the dissolved oxygen will also be added into the system with the supplementary water. Therefore, the dissolved oxygen is the main reason which causes the corrosion of chilled water system. As the chilled water system runs in a closed circulation for a long time, it will lead to the propagation of anaerobic bacteria which can also corrupt the pipe.
II. The drug of Chlorine dosing system
2.1 Corrosion Inhibitor for Closed Chilled Water The corrosion inhibitor of chemical dosing system consists of nitrite, molybdate and phosphate with a strong synergistic inhibition effect especially to the carbon steel, copper and aluminum. The corrosion types it can prevent include: uniform corrosion, crevice corrosion, pitting corrosion and stress corrosion. It has a good heat resistance and applicable to the closed soft water system like chilled water system and high temperature water system.
2.2 Biological Control We adopt efficient broad-spectrum biocide which has a good sterilizing effect to the heterotroph, iron bacteria, sulfate reducing bacteria and various algae. It is compounded by the base glutaraldehyde, cationic surface active agent and assistant, and able to inhibit the process of microbial protein synthesis and destruct the cell membrane to cause the death of microorganism efficiently. The product can sterilize efficiently and quickly with a long term of effect and applicable to a wide PH value range especially in the low alkali condition.
III. Dosing method of Chlorine dosing system
3.1 Irregular dosing according to the water quality detection result
3.2 Continuous dosing: Continuous discharging and adding of water with dosing
3.3 Regular dosing: change water with dosing at regular intervals. As water change consumes large quantity of cold energy, partial discharge and partial supplement will be applied in general, as well as partial discharge and supplement of chilled water every few months
3.4 Automatic dosing control: the dosing can be controlled through the conductivity and discharge quantity of the chilled water indicated by the detectors.