The cryogenic air separation process is among the most energy-intensive operations and requires intelligent approaches to minimize its operational cost, the main constituent of which is the power cost. Some of the air separation plants operate in a co-operative manner with each other, and to capture the intricacies of these arrangements, a novel multisite framework is needed. In this paper, a novel approach called enclave optimization, which incorporates a small product exchange network among plants in the enclave, along with the multiplant production network, is introduced. The merits of enclave level framework lie in its ability to address the major challenges that originate from multiplant arrangements such as shared inventory, common customer and global liquid demands, etc. Motivated by the time scales of (0 gas and liquid demands and (ii) other operational factors, we adopt a nonuniform time discretization framework, which helps to define constraints regarding different products in various time scales, over the optimization horizon. The results show that the successful implementation of the nonuniform time discretization greatly reduces the overall number of constraints and variables involved in the optimization problem and makes the formulation computationally efficient. The above-mentioned nonuniform time, enclave level framework is applied to a real-world multiplant setting using representative scenarios provided by Praxair India Pvt., Ltd. The proposed model manifests its efficacy by optimizing those plants in a collaborative manner to determine an overall minimum production cost with high computational efficiency.