Skip to main content
ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #387618
Research Project: Innovative Manure Treatment Technologies and Enhanced Soil Health for Agricultural Systems of the Southeastern Coastal Plain

Location: Coastal Plain Soil, Water and Plant Conservation Research

Title: Theoretical framework for estimating design reactor pressure for water-based hydrothermal carbonization (HTC) systems

Author
item ALVAREZ-MURILLO, ANDRES - University Of Extremadura
item LIBRA, JUDY - Leibniz Institute
item Ro, Kyoung

Submitted to: Thermal Science and Engineering Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2022
Publication Date: 3/11/2022
Citation: Alvarez-Murillo, A., Libra, J.A., Ro, K.S. 2022. Theoretical framework for estimating design reactor pressure for water-based hydrothermal carbonization (HTC) systems. Thermal Science and Engineering Progress. 30:101241. https://doi.org/10.1016/j.tsep.2022.101241.
DOI: https://doi.org/10.1016/j.tsep.2022.101241

Interpretive Summary: Hydrothermal carbonization (HTC) uses water as the reaction media to thermochemically convert wet organic residues and wastes from numerous sources to a carbonaceous solid product called hydrochar. The hydrochar has been shown to be used as a fossil coal alternative, soil amendment, or carbon materials that can be used as adsorbents to remove pollutants from water or gases or for other application such as batteries. An important basis for designing cost-effective equipment for the HTC systems is understanding the safety aspects and related costs associated with the reactor pressure resulting from hydrothermal reactions. While the reaction temperatures in HTC are much lower than those in alternative thermochemical processes for biomass such as pyrolysis, gasification or combustion usually operating at atmospheric pressures, the pressures required in HTC are much higher, rising with temperature as the autogenic pressure of water rises, in addition to the pressure increases due to reaction gas production. The high-pressure conditions will determine the design parameters, such as thickness, manufacturing techniques, materials in the reactor system. Thus, it is very important to predict the HTC reactor pressure that can be reached before we design reactor system for hydrothermally carbonizing various biomass. Up until now, there is no systematic method to predict the HTC reactor pressure for biomass systems reported in the literature. In this study, we developed theoretical framework in predicting HTC reactor pressure, validated the developed model with well-defined experiments, compared the accuracy of the theoretical model with actual HTC reaction with real biomass beet and bark, and suggested simple design procedure to predict HTC reactor pressure. The easy-to-follow methodology developed in this study will help researchers, design engineers, and manufacturers to estimate the pressure reached in the HTC reactor based on desired design goals and promote the widespread use of HTC for converting wet wastes into value added hydrochar which can improve soil health and reduce environmental pollution.

Technical Abstract: Hydrothermal carbonization (HTC) has been shown to be a valuable system component in sustainable management strategies for wet organic residues from agriculture, industries and municipalities. While the reaction temperatures in HTC are much lower than those in alternative thermochemical processes, the pressures required in HTC are much higher, rising with temperature as the autogenic pressure of water rises, and as reaction gas is produced. An important basis for designing cost-effective equipment for the HTC systems is understanding the safety aspects and related costs associated with the reactor pressure resulting from hydrothermal reactions. This paper presents a theoretical framework to predict the expected HTC reactor pressure for biomass reactions producing carbon dioxide (CO2). The developed model was validated by well-defined experiments with carbon dioxide-water (CO2-H2O). The accuracy of the theoretical model was compared with actual pressures in HTC reactions with real biomass (bark mulch, sugar beet pulp) and a simple design procedure was suggested to predict HTC reactor pressure. The results of a sensitivity analysis showed that the pressure estimation is most affected by the parameters related to the amount of CO2 formed during the HTC reaction. The easy-to-follow methodology developed in this study will help researchers, design engineers, and manufacturers to estimate the pressure reached in the HTC reactor based on desired design goals and promote the widespread use of HTC for converting wet wastes into value added hydrochar which can improve soil health and reduce environmental pollution.