(393c) Coupling Process Intensification and Process Flowsheeting for Addressing Mass Transfer Effects on Technoeconomic and Life Cycle Assesstment. the Case of HMF Production.

The sustainability concerns of fossil-based chemicals have promoted the search for new renewable sources and more sustainable manufacturing routes. Vegetal biomass, with an estimated potential of nearly 450 gigatons, has been proposed as an interesting renewable raw material for producing fuels and chemicals.¹ One of the most attractive biomass-based platform chemicals is 5-hydroxymethyl furfural (HMF).² HMF can be converted into a wide range of added-value products such as lubricants, detergents, pharmaceutics, and dienes. Techno-economic (TEA) and Life Cycle Assessment analyses (LCA) have been performed for HMF production using Continuous Stirred Tank Reactors CSTR evaluating the type of solvent³ or raw materials (e.g., glucose vs fructose).⁴ Other studies have focused on process intensification and evaluated different separation methods⁵ such as adsorption beds to recover HMF with low energy requirements. Although these intensified separation techniques improve profitability, most TEA studies have highlighted that the main economic limitation is the cost of sugars or biomass used as raw material and the low yields achieved in the reactor.⁶ In order to improve the yield, plug-flow microreactors are an attractive alternative that increases heat and mass transfer rates by 2-3 orders of magnitude in comparison with conventional reactors; at the same time they allow the continuous production of HMF.⁷ At sufficiently high flow velocities and adequate temperatures, yields of nearly 100% have been obtained.⁸ Integrating the design of these reactors within the TEA and LCA is not a simple task, requiring the development of new modeling frameworks.

In this work, we develop a new framework that addresses detailed models able to integrate the heat and mass transfer mechanisms into the design of the process and subsequently the TEA and LCA.⁹ The iterative modeling framework is composed of two sections: The first one includes the kinetic model and the design of the reactor following the Number of Transfer Units (NTU) method. The second part is an Aspen Plus that models the process. Both models are run following the iterative procedure presented in Figure 1. The procedure is implemented in a script that connects the kinetic model in Python with an Aspen Plus model by means of the libraries os and win32.

The framework has been used to compare micro-reactors versus conventional reactors in HMF production. The results show that microreactors reduce the minimum selling price (MSP) by at least 10%. Apart from the economics, the environmental results have shown that microreactors reduce emissions by at least 5% compared to conventional-size reactors and up to 40% for bigger sizes. Sensitivity analysis points to the reactor diameter as a key one. Diameters above 1 inch reduce the heat transfer significantly, requiring higher residence times and longer reactors to achieve the maximum conversion.

References

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9. Hernández, B; Vlachos, D.G.; Ierapetritou, M.G. Coupling Process Intensification and Systems Flowsheeting for Economic and Environmental Analysis of 5-Hydroxymethyl Furfural Modular Microreactor Plants. ACS Sust Chem Eng. 2022, 10,45,14955-14971.