Cooling-water treatment 
             for control of 
                    scaling, fouling, corrosive

    In order to mitigate the problem of water resource shortage, to promote the water reuse by circulating-cooling-water technology is a suitable choice.
    Water remove heat form process fluids through heat exchanger and move on to cooling tower to cold there by evaporation. Some part lost by evaporation, leaks and intentional discharge can be supplement by make-up water,in order to maintain an acceptable level of salinity in system.
    After full cycle then water can be reused.

Therefore, the problems associated with deposits formation , microbiological deposition and corrosion are occurred here.

• Higher water temperatures, promoting scale deposition and more rapid corrosion.

• Microorganism, dust and dirt introducing to circulating water through cooling tower and enhanced potential for fouling and corrosion ;

• Addition of make-up water, more scale, deposit and corrosion-forming constituents will be brought into it;

• Continued presence of oxygen--which is particularly corrosive to mild steel and other metals--caused corrosion of heat exchangers.

 Modern preventive measures

A: Keep the scale-forming constituents in solution; 
  Polyacrylate、its modifier and organophosphonic acid are the newer, cost-effective, most commonly used chemicals.
    Polyacrylates are effective scale inhibitors for calcium carbonate and sulfate control at high temperatures (over 250F). They are stable and soluble at high and low pH levels, good dispersants for suspended material, and low in cost. 
    Organophosphnic acids are the other group for scale control and corrosion inhibition. These compounds keep calcium salts in solution even at quite high pH values, at high scale-mineral concentrations, and protect mild steel under severe scaling conditions.
B: Oxidizing chemical and nonoxidizing types are effective microboicides.
    In oxidizing chemicals there are chlorine, chlorine dioxide, bromine chloride and brominated propionamides. They oxidize protein groups resulting in loss of normal enzyme activity. 
    In some situations, nonoxidizing toxicants prove to be more effective than their oxidizing counterparts, or else they are used in conjunction with oxidizing microbiocides for broader control. Chlorinated phenolics, Chloroisocyanurates, N-Halohydantoin, Methylene bis-thiocyanate. and Quaternary ammonium are commonly used nonoxidizing toxicants.
    The choice between oxidizing and nonoxidizing microbicides depend on the limitation discharge of toxic substance, the operating parameters of cooling water system: temperature, and pH.
C: Corrosion inhibition 
    Cathodic inhibitors are favorable considered "safe" inhibitors for corrosion control. Polyphosphate and calcium, mixture of organophosphnic acid and zinc are excellent corrosion inhibitors for Cooling-water treatment.