(347a) A Systematic Approach for Synthesizing Carbon-Hydrogen-Oxygen Networks Involving Detailed Process Simulations

Carbon-Hydrogen-Oxygen symbiotic networks (CHOSYN) are settled for multi-plant mass integration among hydrocarbon processing plants as a strategy for reaching more sustainable industrial processes through performance targets as reduction of raw material usage and waste generation, but also economic targets as cost reductions and profitability enhancement [1]. The foremost problems of synthesis of CHOSYN is to optimize the allocation of the exchanged resources through the integration network, sizing the involved processes and detailing exchange network meanwhile performance targets are satisfied. Stoichiometric-economic targeting methodologies followed by an associated mathematical programming problem were previously proposed to solve the problem of synthesis [2-3], regardless they offer benchmarks through bounds of material usage there is a lack of detailing to continue with the conceptual design of the CHOSYN and the evident need of a rigorous method that provides information for detailing a non-idealistic configuration of the network. A systematic approach for CHOSYNs synthesis involving detailed process simulation is proposed, the features and advantages of using a processes simulation software are discussed. The methodology proposes a sequential and iterative approach aided by a process simulator (i.e., Aspen plus®). The process simulator makes possible to determine the amount of available resources in the network at any design stage, it makes easier to determine the size of the new processing plants, and provides performance and cost information to determine the total cost of the network. Also, the simulation environment offers the possibility, in an easy way, to propose and evaluate the needed units for changing operating conditions from sources to sinks in the exchanging network.

The proposed approach consists in three main tasks, which are described as follows:

1) Total identification of the existing available resources and sinks of the network: flowrate, composition, temperature and pressure.

2) Selection of the new plant as well as its processing capacity (the new plants are part of the new facilities to carry out the integration).

3) Scale up, simulation and coupling of the new plant to the previous network.

The methodology developed through this approach was implemented in a case study, which involves five existing plants (Auto thermal reforming of natural gas, Ethylene plant, propane dehydrogenation, methanol to propylene and monomer of vinyl acetate) seeking for satisfying internal sinks (140 kmol/h of acetic acid and 6500 kmol/h of methanol) through the selection of new plants among set of seven installable plants (acetic acid production, methanol from syngas, methanol from CO₂, Dry reforming of methane, steam reforming of methane to syngas and to CO₂, and Water Gas Shift reaction), which foremost entailing the maximum use of internal sources (H₂O, CH₄, CO, CO₂ and H₂) and resource conservation. The results show four different feasible final configurations where different combinations new plants are selected. The results of each solution show the total reduction of raw material in general, the allocation of each exchangeable stream with its flowrate, pressure and temperature and the extra needed operating units to change this conditions and make feasible the linking from the sources to the sink. These solutions are evaluated and compared through economic and resource usage performances. The best solutions according these objectives is to produce 202 ton/day of Acetic acid, 882 ton/day of methanol from syngas, 2152 ton /day of methanol from CO₂ and 253 ton/day of syngas from steam methane reforming. This configuration allows to save 289 million USD/year in raw material purchasing with a new total investment of 127 million USD. Since the complexity of CHOSYNs design, the proposed method represents an easy way to meet the lack of detailing by including processing conditions in the design. Besides the software provides enough information to a close evaluation of the different objectives of the network.

References

[1] Noureldin, M. M. B., & El‐Halwagi, M. M. (2015). Synthesis of C‐H‐O Symbiosis Networks. AIChE Journal, 61(4), 1242–1262. https://doi.org/10.1002/aic.14714

[2] El-Halwagi, M. M. (2017). A Shortcut Approach to the Multi-scale Atomic Targeting and Design of C–H–O Symbiosis Networks. Process Integration and Optimization for Sustainability, 1(1), 3–13. https://doi.org/10.1007/s41660-016-0001-y

[3] Juárez-García, M., Ponce-Ortega, J. M., & El-Halwagi, M. M. (2018). A Disjunctive Programming Approach for Optimizing Carbon, Hydrogen, and Oxygen Symbiosis Networks. Process Integration and Optimization for Sustainability. https://doi.org/10.1007/s41660-018-0065-y