Study On Scale And Corrosion Inhibition In The Reclaimed Water Recycling Cooling System For The Power Plant

Because the water quality requirements of the power plants recycling cooling arebelow the domestic water, there are significant environmental and social benefits ifreclaimed water is used as the source of recycling cooling water for the power plants.However, the reclaimed water quality is special and complex, so it will cause moreserious scaling and corrosion problems when it is used as supplementary water insteadof the fresh water. These problems can affect the normal operation of recyclingcooling systems for the power plants or lead to a security incident.The double-membrane water of a recycling plant was used as the adding water ofrecycling cooling systerm for the power plants in this paper. The study of waterquality stabilization technology was carried out when the reclaimed water was reusedinto recycling cooling system. Aiming at the double-membrane water quality, themethods of calcium carbonate deposition, rotating coupon and dynamic simulationexperiment were used to investigate scale and corrosion inhibition properties of thescale-corrosion inhibitors. And the scale and corrosion inhibition mechanism of theseinhibitors was explored by Scanning Electron Microscopy and Energy DispersiveSpectrometer. The economic, efficient and environmental friendly scale-corrosioninhibitors for stainless steel and carbon steel were screened to slow down the processof scaling and corrosion for the power plants condenser. The scale-corrosioninhibitors can also achieve the purpose of providing technology demonstration for thepower plants water-saving or emission-reduction. The main conclusions were asfollows:（1）Under the condition of3times concentration in the static experiment, thedosages of HT-1A1and HT-1A2were38mg/L and31mg/L, respectively. Scaleinhibition efficiencies were96%and98%, respectively. Corrosion inhibition rates forstainless steel were56.5%and91.3%, respectively. The annual corrosion rates forstainless steel were both controlled less than0.001mm/a.（2）Under the condition of high concentration multiple, the dosages of HT-2A1and HT-2A2were both27mg/L in the static experiment. The scale inhibitionefficiencies reached87%and86%, respectively. The annual corrosion rates for carbonsteel were0.0723mm/a and0.0689mm/a, respectively. The corrosion inhibition efficiencies for carbon steel were82.95%and83.75%, respectively.（3）In the dynamic experiment, HT-1A1and HT-1A2can control the foulingresistances of two systems stable at about1.6×10^-4m²·℃/W under the condition ofthree times concentration which were both less than the national standard3.44×10^-4m²·℃/W. And stainless steel coupon corrosion rates were also less than thenational standard.（4）Scale inhibition mechanism for HT-1A1and HT-1A2mainly included latticedistortion, chelation solubilization and charge dispersion. Corrosion inhibitionmechanism for stainless steel was the coexistence of the precipitation and adsorptionmembranes consisting of carbon, oxygen and calcium to restrain the cathodic reaction.Howerer, corrosion inhibition mechanism for carbon steel included the coexistence ofthe precipitation and adsorption membranes consisting of carbon and oxygen. It alsoincluded better dispersion of iron and calcium deposition to inhibit corrosion underthe scale.