Novel Prediction Model Based on Two-Film Theory for Ammonia Distribution Coefficient in Heat Recovery Steam Generator of Gas Turbine Combined Cycle Power Plants

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ABSTRACT

In a combined cycle power plant with a heat recovery steam generator, ammonia and hydrazine are injected into the boiler feedwater, while sodium phosphate is used in the drum boiler water. However, hydrazine is feared to cause health problems, and sodium phosphate may cause phosphoric acid corrosion. An alternative method has been applied in recent years wherein only ammonia is used for water treatment. Although the ammonia concentration in the drum boiler water depends on the gas-liquid distribution coefficient of ammonia, the measured result of the gas-liquid distribution coefficient in the actual plants is found to be smaller than the reported value in the equilibrium state. This is because the boiler feedwater passes through the drum boiler before attaining equilibrium. In this study, a novel dynamic model for the gas- liquid distribution of ammonia between the drum boiler water and the drum boiler steam was investigated by applying the two-film theory. Using this novel model, the ammonia gas-liquid distribution coefficient in the drum boiler can be estimated more accurately. Furthermore, the ammonia concentration of the boiler feedwater can be determined, even in a water treatment system with only ammonia, which is effective in preventing flow-accelerated corrosion of the drum boiler.

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Nakatsuchi, Y., Kido, H., Hamasaki, A., Fujimoto, S., "Novel Prediction Model Based on Two-Film Theory for Ammonia Distribution Coefficient in Heat Recovery Steam Generator of Gas Turbine Combined Cycle Power Plants", PPCHEM 2025, 27(2), 102.
DOI 10.69158/PPCHEM.2025.02.102

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