Once-through cooling system

Figure 1.1 Schematic of once-through cooling system.

The following is a summary of once-through cooling system flow rates based on responses to 308 USEPA questionnaires. 

The once-through cooling system flow rate range of 239 steam electric power generation plants using coal is 0.189-6,280,000 m /plant (mean 1,130,000 m / plant), which is equal to 0.001-209,000 mVMW (mean 4,310,000 m /MW). 

Wet cooling systems often employ once-though water, drawn from the sea, a lake, or a river. Where adequate supplies of water are available, once-through cooling systems are still one of the primary choices for large users, such as power generation or major industrial processors. 

Mechanical and Chemical Deaeration. The corrosive quahties of water can he reduced by deaeration. Vacuum deaeration has been used successftdly in once-through cooling systems. When all oxygen is not removed, catalyzed sodium sulfite can be used to remove the remaining oxygen. The sulfite reaction with dissolved oxygen is... 

In addition to weeds, acrolein is used to control fouling organisms in cooling water systems. Effective control was established in a once-through cooling system of a steel mill with continuous application of 200.0 p,g... 

Accidents resulting from two simultaneous Independent system failures are considered credible accidents. For example a major primary loop rupture combined with failure of the emergency once-through cooling system to supply coolant Is the maxlmimi credible accident. 

Thus, the reactor can be shutdown in an orderly fashion, cooled and depressiirized without dependence on the emergency once-through cooling system. 

The corrosion testing techniques described can also be used in closed cooling systems, once-through cooling systems, boiler feed water systems, etc. 

The survey will uncover applications for water that can be recycled for repeated reuse. Some wastewater, now discharged to the sewer, may be well suited for cooling or boiler feed. The economics of using coohng towers to replace once-through cooling systems should be reconsidered. In some cases it may even pay to switch to air-cooled heat exchangers. 

The consensus today for once-through cooling systems seems to be that, where permitted, the materials of construction must be chosen to be resistant to the water, be it fresh water or seawater. All natural... 

Once-through cooling systems require inexpensive corrosion inhibitors. In open systems, corrosion is more severe and good inhibition is imperative. The situation is similar to that in municipal water supplies, so comparable remedial measures, namely addition of lime or polyphosphates, are used. In waters that are very corrosive due to high chloride concentrations, chromates or nitrites may be required in addition to polyphosphates. 

---