INVESTIGATION OF INCREASING PROCESS GAS COOLING PERFORMANCE BY IMPROVING AMMONIA OXIDATION REACTOR HEAT EXCHANGERS

This study aims to increase the cooling performance of NOx gas by improving the heat exchangers of an industrial-type ammonia oxidation reactor with a diameter of 3.8 m and a height of 6.5 m in a nitric acid production plant with a capacity of 610 tons/day. The reactor produces 100% HNO3, 56% diluted nitric acid, and 33 tons/hour of superheated steam. To this end, the parametric analysis study, in which the horizontal and vertical distance between the exchanger tubes, the pipe diameters, and the distance between the exchanger packages (pre-evaporator, superheater, evaporator, economizer) were used separately, was carried out with the help of Ansys Fluent program and the flow properties and performance values were examined. The best cooling performance (for the inner part of the ammonia oxidation reactor) resulted from different parametric studies; there was a study in which the process gas temperature was obtained at 270.510C with a 56 mm horizontal distance between the heat exchanger tubes (a). Thus, a 9.1% decrease in the actual gas outlet temperature of the operating reactor was achieved. In other parametric studies, the lowest process gas temperatures are; it was found to be 323.200C for the distance between heat exchanger packages (L), 318.42 0C for the vertical distance between heat exchanger tubes (b), and 296.67 0C for the heat exchanger tube diameter (D). In addition, when the CFD simulation results, which provide the best cooling performance, are compared with actual operating data (SCADA online data), In the ammonia oxidation reactor, the fluid outlet temperature increased by 8.2% in the economizer, 9.7% in the evaporator and 4.3% in the superheater.