Modeling and performance improvement of an industrial ammonia synthesis reactor

Abstract

Ammonia production from synthesis gas is one of the most important processes in the petrochemical industry. A heterogeneous model is used to improve the efficiency of an industrial ammonia synthesis reactor including three adiabatic catalyst beds. In this model, the effectiveness factor was determined by considering the diffusion reaction equation. Reasonable agreement was achieved between simulated results and industrial data in terms of reactor component mole fraction and temperature. This mathematical model was modified to use for improving the ammonia converter performance and predict the effectiveness factors, nitrogen fractional conversion, temperature, and hydrogen and ammonia mole fraction profiles. The competency of the modified model has been investigated for industrial application by manipulating the reactor operation conditions and observing their effects on reactor output and results revealed the reliability of the developed model.The model is employed to obtain the optimum temperature profiles of each catalyst bed in the reactor based on equilibrium curve of ammonia synthesis reaction. Operating condition of the reactor was changed to achieve the optimum temperature profile according to model results by manipulating the reactor quench valves. After implementing changes in the reactor, the reactor performance and efficiency has improved with increasing ammonia conversion from 15.26% to 15.45% that increases ammonia production by 3t/d and energy saving by 1.66 Gj/h. The differential temperature of the first catalyst bed significantly increased by 6 °C and overall differential temperature through ammonia converter is increased by around 4 °C. This increases steam production by 2 t/h through loop boiler.

Keywords

• Modeling
• Optimization
• Reliability
• Fixed bed reactor
• Ammonia synthesis