Innovation in waste-to-energy hydrothermal conversions modeling

The current global environmental concerns require advanced solutions approach that will ensure we remain on the right path for nurturing sustainable development. In particular, among the available conversion processes, biomass hydrothermal carbonization has attracted significant research interest. In addition to offering solutions to emerging environmental problems, it is also a promising contributor to the production of low-cost super-performing materials for various industrial processes such as the conversion and exploitation of biomass and wastes.

Advancement in biomass hydrothermal carbonization-based processes is faced by several challenges including inadequate understanding of the current limits of reaction kinetics and unavailability of basic experimental data. Therefore, the development of new kinetic modeling for intensification of sustainable biomass-based hydrothermal carbonization processes is highly desirable to enable technology transfer from research to industry. This could involve improvement of the available mathematical models to accommodate valuable information for the process. Regarding the available biomass hydrothermal carbonization modeling approaches, statistical techniques, in particular, can greatly contribute to the hydrothermal carbonization modeling.

Recently, Professor Alberto Gallifuoco from the Department of Industrial and Information Engineering & Economics at University of L’Aquila investigated the kinetics of biomass hydrothermal carbonization of lignocellulosic biomass. Fundamentally, a Markov-chain process was used to describe the biomass hydrothermal carbonization mechanism for modeling the reaction of biomass with hot compressed air. On the other hand, handling of the batch reaction data and determining the required probability distribution for analyzing the process statistically was done through a setup procedure. The main objective was to further explore the previous findings and give a proof of the correctness of the previous hypothesis for handling the experimental data for accessing the model statistically. His new method is currently published in the journal, ACS Sustainable Chemistry & Engineering.

Markov analysis technique proved sufficient for studying the kinetics of biomass hydrothermal carbonization of lignocellulosic biomass. By obtaining the transition probability functions, the matrix algebra essential for evaluating the dynamics of the reacting system was developed. Thus, the interactions between the hot compressed water and solid substrate were modeled based on the probability laws. Consequently, this methodology exhibited the ability to furnish useful information for the design and development of advanced biomass hydrothermal carbonization industrial processes.

As a concept proof, the model was tested with data concerning batch reactions of both agro-food residual and lignocellulosic biomass. The test was carried out at 200^°C and a fixed 7:1 water to the solid ratio for up to 120 minutes. In addition, data derived from the literature were also used. The experimental results agreed well with the simulation results for a broad temperature range and residence time. In addition, valuable indications useful for refining the models were provided. Furthermore, it was worth noting that the proposed modeling approach could help in the selection of the optimal kinetic pattern provided in the literature.

In summary, Professor Alberto Gallifuoco in a statement to Advances in Engineering noted that for the first time the probabilistic approach is applied in modeling biomass reaction with hot compressed air. Based on the results, he is confident that the presented method is flexible enough and will offer an additional tool for modeling the hydrothermal carbonization for different types of biomass.