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Chemical Engineering Science, Vol.203, 1-11, 2019
CO2 footprint reduction via the optimal design of Carbon-Hydrogen-Oxygen SYmbiosis Networks (CHOSYNs)
Carbon dioxide (CO2) has significant potential as a chemical feedstock as it is an abundant source of carbon atoms, entails zero or negative acquisition costs and utilization reduces environmental impact. However, significant challenges remain as the use of this feedstock involves unfavorable thermodynamics in reaction and separation, material transportation and end use application. Opportunities exist to overcome these limitations especially within eco-industrial parks which involve a group of facilities cooperating by exchanging materials and energy. An important class of EIPs, Carbon-Hydrogen-Oxygen SYmbiosis Networks (CHOSYN), has been recently introduced to integrate hydrocarbon streams from multiple plants while allowing for chemical conversion (in addition to the conventional exchange, separation, and allocation) through a multiscale targeting approach. The objective of this work is to address the problem of designing a CHOSYN with the conversion of CO2 into value-added chemicals while reducing the carbon footprint for the whole system. A multi-scale synthesis and optimization approach is proposed. First, atomic-level information coupled with economic data are used to establish benchmarks for the utilization of process streams, the purchase of external sources, and the discharge of CO2. A presynthesis approach is adopted to develop optimal policies for the CO2-separation technologies. Candidate CO2-utilization reactions are integrated with the existing plants to produce value-added chemicals while addressing economic and environmental objectives. Carbon-footprint constraints are added based on life-cycle analysis of the used sources and energy associated with the various reaction and separation steps. This systematic procedure captures significant interactions between surrounding CO2 sources and CO2 sinks while reducing the difficulty of selection and design of the CO2 capture process. A case study is developed and solved to demonstrate the application of this new method. (C) 2019 Elsevier Ltd. All rights reserved.