The cation conductivity in water-steam cycle has been significantly increased as external heating units presented on trends in large capacity and high parameters. Real test has been carried out to demonstrate the TOC concentration in feedwater has been increased as the external heating increases. The presence of organic acid would significantly reduce the pH of the condensate and result in general corrosion, pitting and environment assisted cracking. For the cogeneration thermal power stations in which make-up water were produced with traditional ion exchange system and Integrated Membrane Technology separately, the main factors affecting cation conductivity of steam are residues of the organics in raw water and dynamic variation about bacterial reproduction in reducing environment, respectively. If gel type anion resin had been replaced with macroporous strong base anion resin, the remaining TOC in traditional ion exchange system could be significantly reduced. And if non-oxidative bactericide had been dosed before or after Ultrahigh Purity Filter, bacteria could be effectively killed. For heat-supply units, the actual rates of makeup water, denote with “N%”, are always more than the design value. So it is very important in this scenario to revise the ceiling values of TOC for makeup water, which should be divided by N, to allow that ceiling value to match the actual rate of makeup water. For drum boilers and once-through boilers which superheated steam pressure are greater than 18.3 MPa, in order to guarantee the cation conductivity (25 °C) values of feed water less than the standard of 0.10 μ S/cm, TOC values in feed water should be under 50μ g/L.

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