Computational Modeling Approaches of Hydrothermal Carbonization: A Critical Review

Abstract

Hydrothermal carbonization (HTC) continues to gain recognition over other valorization techniques for organic and biomass residue in recent research. The hydrochar product of HTC can be effectively produced from various sustainable resources and has been shown to have impressive potential for a wide range of applications. As industries work to adapt the implementation of HTC over large processes, the need for reliable models that can be referred to for predictions and optimization studies are becoming imperative. Although much of the available research relating to HTC has worked on the modeling area, a large gap remains in developing advanced computational models that can better describe the complex mechanisms, heat transfer, and fluid dynamics that take place in the reactor of the process. This review aims to highlight the importance of expanding the research relating to computational modeling for HTC conversion of biomass. It identifies six research areas that are recommended to be further examined for contributing to necessary advancements that need to be made for large-scale and continuous HTC operations. The six areas that are identified for further investigation are variable feedstock compositions, heat of exothermic reactions, type of reactor and scale-up, consideration of pre-pressurization, consideration of the heat-up period, and porosity of feedstock. Addressing these areas in future HTC modeling efforts will greatly help with commercialization of this promising technology.

Research Needs and Pathways to Advance Hydrothermal Carbonization Technology

“…In light of the recentness of these two reviews, the aim of this section is not to provide yet another comprehensive survey of the existing literature. Instead, it aims to offer a concise overview of the objectives and The scarcity of efforts in HTC modeling is also reflected in the number of existing review articles that focus on this topic: as far as we are aware, the only ones are the 2021 work by Ischia and Fiori (2020) [47] and the 2022 work by Ubene et al (2022) [48] (although others have also covered the topic with less focus [3,49]). In light of the recentness of these two reviews, the aim of this section is not to provide yet another comprehensive survey of the existing literature.…”

High Surface Area Microporous Activated Carbon from Corn Fiber Using Graphene Oxide-Assisted Hydrothermal Carbonization

“…With the global transition away from fossil fuels and towards green technology comprising of zero or negative carbon emissions, the suitability of porous carbon materials as the most environmentally sustainable and affordable options for adsorbent applications has become apparent. , Thermochemical conversion processes which produce these materials have further progressed emission and cost reduction efforts through the incorporation of hydrothermal technologies as an initial carbonization step. These technologies, such as hydrothermal carbonization (HTC), entail many advantages over pyrolysis as an initial pre-treatment method for activated carbon (AC) production and promote the utilization of biomass as carbonaceous feedstock by eliminating the need for drying feedstock, reducing ash content, requiring lower energy inputs, and producing higher solid yields. ,− Utilizing biomass for AC production over conventional coal-based precursors that are produced commercially help to reduce waste from agricultural and food residues, produce less emissions, and can be valorized into high-value carbon products for various applications …”

“…The use of HTC as a pre-treatment method overcomes the heterogeneous nature and high moisture content found in biomass by using water in the subcritical state as the reactant, at autogenous pressures (2-6 MPa), and temperatures in the range of 180-350 °C. , In general, the hydrochar product exhibits favorable chemical and structural properties and improved higher heating value (HHV) by possessing a higher carbon content and lower oxygen content, the degree to which is determined by the process conditions. , Besides being used for applications such as soil amendments, catalyst templating, or adsorbents, the improved properties of the hydrochar make it more suitable as a source for subsequent activation to produce AC with well developed porosity, carbon content, and microstructure …”