Mass Exchange Network Design For Continuous And Batch Processes

Mass exchange network (MEN), a system including absorption, stripping, adsorption, extraction, leaching and ion exchange, is of great significance as an important branch in Process Systems Engineering. In a typical problem of mass exchange network design, the valuable or undesirable components in rich process streams can be reduced in countercurrent direct-contacted mass exchange units by contacting with lean process streams or external mass separating agents (MSAs). Techniques of mass exchange network design can be used to improve the materials'purity and the utilization of valuable resources to satisfy the economic benefits, and also reduce the poisonous emissions for the purpose of pollution prevention.This paper is aimed at developing a systemic methodology for minimizing the operating costs and capital costs of the mass exchange networks for both batch and continuous processes in a simultaneous manner. Generally speaking, the State Space Superstructure is adopted to capture all possible network configurations, based on which better total annualized cost (TAC) can be easily generated with the corresponding mixed-integer nonlinear programming (MINLP) model. In addition, a hybrid optimization strategy incorporating both deterministic and stochastic components is developed for the resulting MINLP model to guarantee the solution quality and efficiency. The main contents addressed in this paper can be stated as follows:(1) The characteristics and difficulties of the study in mass exchange network design for continuous processes are first investigated from the views of thermodynamics. By introducing the State Space Superstructure, this paper investigates the mixing/splitting strategies of the streams with different compositions and sources. Furthermore, the mixed-integer nonlinear programming (MINLP) model is formulated based on the State Space Superstructure to optimize the total annual cost (TAC) of the MENs, so that a trade-off between operating cost and capital cost can be achieved.(2) In order to utilizing the materials more sufficiently and thus reducing the harmful emissions, simultaneous optimization of the preliminary network and regeneration networks in the mass exchange systems is investigated in this paper. Moreover, by introducing the Energy Separating Agents (ESAs), this paper further analyses the combined optimization problem of traditional mass exchange network and distillation system, which is corresponding to the use of ESAs. According to a serious of case studies, the proposed model formulation and solution strategy can not only decrease the total cost associated the MENs, but also reduce the consumption of fresh materials and the emission of wastes.(3) Batch productions have aroused ever-increasing awareness for the past decades, due to their incomparable advantages in producing small-amount and high-value-added products. These processes would generate many time-dependent rich or lean process streams with great potential of mass recovery and environmental protection. However, there are several challenges in batch MEN design, such as matches between process streams from different time sequences and the storage strategies, that make the optimization problem as a relatively rare-discussed topic compared with the continuous one. In this work, the State Space superstructure has been improved to capture all the potential structures, including stream splitting and mixing, matches between rich and lean streams, and also allows storage tanks to locate at any possible composition point and any time interval. Furthermore, synthesis problems of the batch mass exchange network with/without storage tanks are both taken into consideration, in order to analysis of the roles of storage strategies in network design for the batch processes.