Abstract

In thermal power plants, during the boilers functioning, heterogeneous deposits of substances must often be removed in order to prolong their operation and avoid their deterioration. The nature, type and quantity of deposits depend on the characteristics of the water supply systems and the chemical operating regime. For boilers with high deposits of copper and iron, the utilization of mineral acids for chemical cleaning is not quite effective, because their surfaces may be covered with a metal copper film. Organic impurities in the water supply affect the operation of steam generators, increasing electrical conductivity and lowering the pH. The heterogeneous composition of the deposits is unevenly distributed in the combustion system, making its cleaning a complex problem. For efficient chemical cleaning, the agents must have a minimal corrosive action on the metal surfaces, ensuring only the dissolution of the compounds on the surface of the boilers. To prevent corrosion of metals, inhibitors are introduced to diminish the reactions on the metal surface or at least to delay the kinetics of the reaction. This paper analyzes the implications of organic pollutants in the corrosion phenomena and chemical processes where they are involved. As an example, the power plant Borzesti affiliated to the Petrochemical Platform, Bacau County, Romania is presented. The adopted solution uses as an inhibitor, a synthesis between amino alcohol and a thiazole, in the presence of water. This inhibitor has been tested in the laboratory on different steels used in energy pipes, in different areas of the thermal circuits in the boiler, as pure steel or with different alloys. The methods used to reduce the effects of corrosion are briefly presented. Four classes of organic substances with properties of corrosion inhibitors in the organic acid environment were analyzed. The experimental results obtained, associated with a comparative analysis of corrosion rates, for different concentrations of inhibitors for a time interval of 4 hours are mentioned. In the second stage, the inhibitor behavior was analyzed for 6h and 8h. Corrosion rates are estimated by measuring the weight loss of the tested probes. Finally, the most suitable types of inhibitors, adapted at different metal compositions are presented, with a result in the cleaning of more than 98% of the surface of the boilers.

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