Study of the influence of iron and copper ions on oxidation processes at different temperatures using hydrazine reagent

Water treatment problems are very relevant in the operation of boiler plants and heating systems, both in small boiler houses, large enterprises, and energy facilities. The main cause of internal corrosion of equipment and pipelines of water heating systems is the presence of corrosive gases (oxygen and carbon dioxide) dissolved in water. This leads to economic costs, disruption of process technology, and also increases the anthropogenic load on the environment. Therefore, high requirements are imposed on these water regimes for desalination and deoxygenation, which allows to reduce the aggressiveness of water, prevent the formation of scale, corrosion of pipes and devices in the water supply system, and reduce the withdrawal of clean water from surface and underground sources. Deoxygenation of water is an important method for reducing metal corrosion, since oxygen is one of the main agents contributing to corrosion processes. Water containing dissolved oxygen can actively interact with metals, causing their oxidation and destruction. Reducing the concentration of oxygen in water helps to significantly slow down these processes. To reduce the oxygen concentration in water, or completely remove it from the system, a fairly large number of methods can be used – physical, chemical, physico-chemical and combined. Hydrazine hydrate is successfully used for water treatment of both drum and direct-flow boilers. The reaction rate depends on the temperature, pH of the medium, excess hydrazine according to the law of mass action, and the presence of catalysts. At temperatures below 30 °C, hydrazine practically does not interact with O2, but at 105 °C, pH 9–9.5, and an excess of hydrazine, the time for almost complete oxygen binding is several seconds. Based on experimental data, dependences were obtained that demonstrate the kinetics of changes in oxygen concentration over one hour. Initially, a study was conducted of the change in oxygen concentration upon addition of hydrazine hydrate when the experimental temperature changed from 15 to 40 °C. Studies of changes in the oxygen concentration in water with the addition of hydrazine hydrate and iron and copper ions and at different temperatures showed that the doses of hydrazine and temperature have the greatest impact on the deoxidation processes, while iron and copper ions almost did not make significant changes to the course of the process. When using iron (II) ions in a composition with hydrazine hydrate at elevated temperatures, an increase in removal efficiency by 30–40 % is noted, and the time to reach zero concentration at maximum doses is reduced by approximately 90 %. Copper (I) ions did not show catalytic properties in compositions with hydrazine hydrate at low temperatures in deoxidation processes and almost did not affect the rate of reaction with oxygen.