A comprehensive model of Primary Enrichment Section (PES) comprising of preliminary isotopic exchange unit (PIEU), ammonia synthesis unit, catalyst stripping unit, ammonia cracker and heat exchange network (HEN) has been developed to determine optimized conditions for heavy water production. A separate PIEU simulation carried out in the previous work has predicted a high temperature operation would be beneficial for the increased deuterium extraction [M.R. Sawant, A.W. Patwardhan, V.G. Gaikar, Simulation of the mono-thermal ammonia hydrogen chemical exchange tower as reactive absorption system, Ind. Eng. Chem. Res. 45 (20) (2006) 6745]. However, it would be limited by adverse effect of the increased temperature on the ammonia synthesis unit. The entire Primary Enrichment Section (PES) is. therefore, simulated to quantify the effect of the operating variables on the throughput of NH2 D from this section. The model predicts that, by increasing the operating temperature of the PES from 248 K to 258 K would not only reduce the energy requirement in the HEN by 50% but also increases the productivity of heavy water by 7%. (C) 2008 Elsevier B.V. All rights reserved.