Operation and Thermodynamic Modeling of a Novel Advanced Hydrothermal Reactor: Introduction of the Novel 3-Step Evolution Model

• Published in: Energies (Basel) 2023-02, Vol.16 (4), p.2032
• Main Authors: Vakalis, Stergios, Ail, Snehesh Shivananda, Moustakas, Konstantinos, Castaldi, Marco J.
• Format: Article
• Language: English
• Subjects: Biomass; biowaste; Carbon; Carbon dioxide; Carbon monoxide; Chickens; Combustion; Composition; Energy; Evolution; Gasification; hydrochar; hydrothermal carbonization; Manures; mass balances; Methane; Methods; Municipal wastes; Poultry manure; Raw materials; Reactors; Refuse and refuse disposal; Simulation; Sludge; Slurries; Synthesis gas; thermodynamic modeling; Thermodynamic models; Thermodynamics; Waste management
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en16042032

Liquid biowaste represents more than 98% of the total municipal waste streams on wet basis and 4–5% on dry basis. Recent attention has been focused on how to manage it optimally, and several novel technologies are being developed to valorize it. Among the developing alternatives is a technology that operates continuously by integrating a hydrothermal reactor, a gasifier and condenser to recover hydrochar using any produced gases to power the system. This study introduces the “3-step evolution model” in order to simulate the hydrothermal reactor. The model has been developed in a MATLAB/Cantera environment and calculates the outputs as the products of a series of sub-stoichiometric char-gas reactions. Experiments with chicken manure slurry as feedstock were implemented for the validation of the model. Treatment of 32.16 kg/h of chicken manure produces 4.57 kg/h of hydrochar and 3.45 kg/h of syngas. The 3-step evolution model simulated the correct ratio of solid-to-gas, 57–43% (excluding the liquids). The experimentally measured carbon dioxide is used as a correction factor to calculate all the other parameters that cannot be assessed during the continuous operation of the hydrothermal reactor. The simulated compositions for carbon dioxide and methane were 94–96% and 0.5–0.8%, respectively. The values were close to the experimental results that ranged from 94.7% to 95.6% for the carbon dioxide and from 0.5% to 0.7% for the methane. The model predicts that higher temperatures of operation would increase carbon monoxide composition from 4–5% up to 7–8%.