Surface heat exchanger aluminum radiator(SCAL) indirect air-cooling units has become an effective measure to solve problems during power generation in coal-rich and water-poor areas in northern China. However

the phenomenon that the p H value of circulating water increases unexpectedly occurs frequently during stable operation of the SCAL indirect cooling system. The radiator in this system is made of aluminum. The abnormal increase of pH value may cause corrosion of the oxidation film on the aluminum tube

even leading to leakage.Thus

the abnormal increase of pH value of the circulating water is the primary problem troubling chemical operators. By analyzing the structure of the SCAL indirect air-cooling system and the quality of circulating water

the dynamic variables in the system were analyzed in this paper. An in-depth study of this problem was conducted through theoretical calculation and industrial test verification. The results show that

the SCAL indirect air-cooling system is basically in a closed state during operation

the oxygen is difficult to diffuse into the system from outside.The source of the dissolved oxygen in the circulating water of the system is the dissolved oxygen in the desalting water before the operation. Corrosion reaction of carbon steel is the main reaction consuming the dissolved oxygen in the system. The decrease of dissolved oxygen content changes the phase of corrosion products of carbon steel.When the dissolved oxygen content is low

the Fe(OH)2 formed by carbon steel corrosion has relatively large solubility

which can lead to the increase of pH value of the circulating water.