Traditionally, high-purity argon recovery from air is considerably difficult owing to the boiling point of argon close to that of oxygen. Recently with the increasing demands for argon, another attractive source of ammonia purge gas has been paid more attention. In this paper with an objective of minimizing energy consumption per argon product, the two-column process for recovering argon from hydrogen-depleted ammonia purge gas is analyzed and optimized in detail on the ASPEN PLUS platform. Firstly, the model of two-column process is set up using the standard unit operation blocks and PENG-ROB property method of ASPEN PLUS, in which validation of PENG-ROB property method is carried out by comparison with a total 623 experimental data from three aspects: vapor-liquid equilibrium, liquid phase density, and enthalpy. It is followed by the thermodynamic and simulation and sensitivity analysis, which on the one hand can reduce the number of decision variables related to optimization problem, and on the other hand can obtain reasonable parameter specification, variables initial values and ranges, thus effectively ensuring the later optimization algorithm converges quickly and accurately. Finally the built-in sequential quadratic programming (SQP) solver of ASPEN PLUS is adopted to solve the minimum energy consumption optimization problem of two-column process. On the processor of 2.66 GHz Intel(R) Core (TM)2 Duo CPU with 4 GB RAM, the whole optimization only takes CPU times 10 s or so to accomplish. The optimal results show that thermal state of feed to demethanizer is a very efficient and valuable means to reduce system energy consumption which at T-CO5 = 103 K is only 87.4% of that at T-CO5 = 109 K where T-CO5 is the temperature of feed to demethanizer directly reflecting its thermal state. The condensing pressure of hydrogen-depleted ammonia purge gas also plays a vital role in reducing system energy consumption which is less at higher condensing pressure, whereas it almost has no influence on the yield and purity of argon recovery. The optimal operating pressure of flash separator used to remove the residual hydrogen in the feed hydrogen-depleted ammonia purge gas is 0.4-0.6 MPa (A); the most economical reflux ratio of argon distillation column is 1.15, and that of demethanizer varies from 0.33 to 0.45 depending on thermal state of feed to demethanizer. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.