The catalyst activity can be improved by increasing the surface area per unit volume of the catalyst modules. Increased catalyst activity results in reduced recirculation rate and/or lower synthesis pressure. A decreased recirculation rate will lower the power requirements of the circulator and the refrigerator. The increased concentration of ammonia in the exit gases increases the condensation temperature therefore, the amount of ammonia condensed by water cooling increases, decreasing the power requirements for refrigeration (ECCJ, 1999 p.150). 

Although the use of smaller particle size catalysts increases the reaction rate, if the gas velocity in the catalyst bed is not decreased it can result in increased pressure drop which will limit the energy savings (UNIDO, 1979 p.173). The pressure drop can be reduced with the use of radial flow, cross sectional flow, and axial-radial flow converters (ECCJ, 1999 p.150) that operate at relatively low gas velocities and permit the use of small size catalysts (UNIDO, 1979 p.173; Ullmann’s, 2011 p.162 & p.199). Smaller particle sizes of 1.5-3 mm can be used instead of 6-10 mm. In addition to energy savings this measure reduces the catalyst volume required (IPTS/EC, 2007 p.79).