(101f) Effect of Ethylene Oxide Reactor Intensification on the Downstream Processes

Reactor intensification in the chemical process can significantly impact downstream separation, particularly for processes like ethylene oxide (EO) production, where exothermic reactors handle a large amount of inert and unwanted byproducts (i.e., carbon dioxide). The byproducts must be removed before the unreacted reactant can be recycled back into the reactor [1]. Intensifying such a reactor, on the one hand, may provide the opportunity for an increase in reactor efficiency and throughput, but the realization of the efficiency depends on the existing downstream separation process, which may or may not be able to handle the separation.

Reactor intensification with Microfibrous Entraped Catalysts (MFECs) has gained considerable interest in academia and the industry alike. MFECs are a type of catalyst enhancer composed of microfibers metals that entraps catalytic particles and typically have diameters in the range of a few micrometers to a few hundred micrometers [2]. One of the key advantages of MFECs is their high surface area-to-volume ratio, which allows for a greater concentration of catalytic particles per unit volume compared to traditional catalysts. This higher concentration can lead to increased catalytic activity and selectivity, as well as more efficient use of the catalytic material. Another advantage of MFECs is their ability to provide good mixing and convective heat transfer characteristics due to the small size, high surface area, and higher thermal conductivity of the microfibers. This can improve EO reaction kinetics and reduce the potential for mass and heat transfer limitations of traditional catalysts [3-5].

Re-routing or reconfiguration of the chemical process flowsheet by utilizing unused separation columns can be an effective way to enhance separation capacity. This approach involves identifying and utilizing underutilized or idle separation columns in the process flow and reconfiguring the flow to use these columns for other separations instead of investing in new equipment. Previous research works have explored the potential benefits of reconfiguration in terms of cost savings and energy efficiency. As a result of reactor intensification using MFECs, inert materials were reduced, leading to a decrease in solvent usage in the EO separation column. This decrease in solvent use subsequently eliminated the need for one of the two EO purification columns, which can be repurposed to handle excess capacity, resulting in an overall increase in the efficiency of the separation process and process cost reduction.

Derivative-free optimization (DFO) is a framework for solving optimization problems where the objective function and/or its derivative cannot be expressed mathematically. Instead, DFO uses algorithm-specific search strategies to improve objective function values for sets of decision variables until the best set is found [6]. DFO treats the model used to estimate objective function values as a black-box model. In this work, we have applied the DFO framework to find the optimized flowsheet to minimize the overall cost of EO production.

Overall, in this work, reactor intensification with MFEC has been shown to improve the efficiency of the EO separation process. In addition, re-routing or reconfiguring the process flowsheet can reduce operating costs by up to 22.3% for an existing brownfield process and up to 37.5% for a greenfield design, compared to the conventional process. These cost reductions can be achieved by identifying and utilizing underutilized or idle separation columns.

References

[1] Mukta, C.B., Cremaschi, S., Eden, M. R., Tatarchuk, B. J. (2022). Techno-Economic Study of Intensified Ethylene Oxide Production Using High Thermal Conductivity Microfibrous Entrapped Catalyst. Computer Aided Chemical Engineering (Vol. 51, pp.1 Elsevier.

[2] Cheng, X., Yang, H., & Tatarchuk, B. J. (2016). Microfibrous entrapped hybrid iron-based catalysts for Fischer–Tropsch synthesis. Catalysis Today, 273, 62-71.

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[3] Sheng, M., Gonzalez, C. F., Yantz Jr, W. R., Cahela, D. R., Yang, H., Harris, D. R., & Tatarchuk, B. J. (2013). Micro scale heat transfer comparison between packed beds and microfibrous entrapped catalysts. Engineering Applications of Computational Fluid Mechanics, 7(4), 471-485.

[4] Kalluri, R. R., Cahela, D. R., & Tatarchuk, B. J. (2009). Comparative heterogeneous contacting efficiency in fixed bed reactors: Opportunities for new microstructured systems. Applied Catalysis B: Environmental, 90(3-4), 507-515.

[5] Cheng, P., & Tatarchuk, B. J. (2019). Kinetic study of SO2 adsorption on microfibrous entrapped sorbents for solid oxide fuel cell cathode protection. Chemical Engineering Science, 201, 157-166.

[6] Boukouvala, F., Misener, R., & Floudas, C. A. (2016). Global optimization advances in mixed-integer nonlinear programming, MINLP, and constrained derivative-free optimization, CDFO. European Journal of Operational Research, 252(3), 701-727..