Research On Descaling Method Of The Industrial Recirculating Cooling Water System

In industrial production, scaling on the surface of heat exchanger can lead tomany problems, such as output decreasing, energy consumption increasing andshorten lifetime of equipment. The usual method of chemical technology for reducinghardness always causes secondary water pollution. Therefore, an effective, clean andlow-cost technology need be explored to reduce scale species. Electrochemicalmethod, which reduced the hardness by changing the species properties, was studiedto recycle the cooling water.The paper investigated the effects of operating factors on the removal rate,precipitating rate and energy consumption. And different cathodes were used toevaluate the precipitating rate and peeling rate of CaCO3. The results showed that theoptimal operating conditions were5min of retention time,10V of voltage and30℃of water temperature, when the removal rate was30%, precipitating rate was20g/h·m2and the energy consumption was17kWh/kg. Hardness concentration wasdecreased to160mg/L~200mg/L, resulting in higher removal rates and no harm to thenext process. Under the same conditions, the order of precipitating rate was coatedtitanium mesh (little holes)> coated titanium mesh (big holes)> coated titanium>magnesium plate> uncoated titanium. Inverting electrode and increasing current wereused to peel scale on cathode surface. Then the order of peeling rate under these twopeeling methods was same: magnesium plate> uncoated titanium> coated titanium>coated titanium mesh (big holes)> coated titanium mesh (little holes). The peelingrate related to the material and structure of cathode: the bigger area of cathode and therougher surface would induce to higher precipitating rate and lower peeling rate. Inaddition, the inverting electrode method was better than increasing current methodunder same conditions. After peeling, the precipitating rate of cathode was notchanged.