Experimental and theoretical investigations of a new cascaded reactor for ammonia as a renewable fuel

Although there has been the commercially employed and widely used Haber-Bosch ammonia synthesis process which requires the high operating pressure and temperature in addition to the relatively low conversion rates, there is a need for a more compact and modular, but more efficient and effective approach. In conjunction with this, the present study develops, tests and investigates a cascaded ammonia synthesis system to explore the room for improvement in the ammonia conversion efficiencies. A lab-scale prototype is developed to investigate the effect of cascading two ammonia synthesis reactors in series employing pre-reduced KMR catalyst and the experimental investigations revealed the improved ammonia synthesis rates using cascaded configuration. The scanning electron microscopy (SEM) results of the KMR catalyst are also presented at different magnifications of 2.00 kx and 50.0 kx. The Aspen Plus simulation results of the cascaded ammonia synthesis system have also been validated using the experimental results and validation shows the percentage difference ranging from 1.62?6.61%. The experimentally developed cascaded ammonia synthesis system is investigated under different operating temperatures and pressures. The experimental results revealed that the ammonia conversion efficiencies that range from 4.58?7.88% using the single reactor with pressure rise from 6 to 12 bar at the temperature of 370 ?C, increase to the conversion efficiencies of 5.42?9.16% by employing cascaded ammonia synthesis design.

Automated summary

This study developed a cascaded ammonia synthesis system by serially connecting two ammonia synthesis reactors with pre-reduced KMR catalyst, leading to improved synthesis rates. Experimental results showed that under the right operating temperature and pressure, employing a cascaded ammonia synthesis system can increase ammonia conversion efficiencies.