Experimental study and validation of a kinetic scheme for hydrothermal carbonization reactions

Abstract

This study presents a new kinetic scheme for the mass yield prediction of waste lignocellulosic biomasses treated by Hydrothermal Carbonization (HTC). The proposed reactions are based on the decomposition, solubilization, and polymerization of each main fraction of the biomass: cellulose, hemicellulose, and lignin. The ash content was assumed to be inert. The kinetic parameters have been obtained by non-linear adjustment using a data set with 220 experimental runs collected from the literature. The results indicate that the pre-exponential factors range was from 7.33 x10 1 to 1.412x10 5 min -1 , and activation energies were between 33.75 y 225.3 kJ/mol.A good fit is achieved between the observed and predicted data with an R 2 of 0.81 and an RMSE of 7.7 %. The proposed scheme was validated with the experimental data obtained by the HTC of sawdust (Pinus radiata) and rapeseed (Brassica napus). The experiments were carried out at temperatures of 190, 220, and 250 ºC and reaction times of 0, 30, 60, 90, and 120 min. The predicted values showed an average error of 2.3 and 3.5 %, respectively. Therefore, the kinetic scheme is a useful tool in the conversion analysis of waste biomass treated by HTC.

Insights into hydrothermal treatment of biomass blends: Assessing energy yield and ash content for biofuel enhancement

“…Other factors, including residence time, additives, and alterations in secondary biomass composition, influenced ash content outcomes significantly. Reactions promoting biomass decomposition under longer residence times at high temperatures and pressures were observed [ 62 , 63 ], impacting the carbon content of the initial feedstock. Distinct ash reduction trends were observed in specific experimental sets, notably sets 1, 3, and 7, where time duration emerged as a critical factor driving ash reduction, particularly evident in experiments utilizing agricultural residues such as oat husks (AV) and pressed olive (OLV) as primary biomass sources.…”

“…Various studies have been carried out to establish the impact of the macromolecular composition of the biomass during the HTC process [ 19 , 68 , 69 ]. The secondary biomass change (30% in the blends) generated an MY decrease (sets 1,3 and 7) and an HHV increase (sets 5 to 8).…”

“…The next challenge of the HTC process development is to achieve high yields on a full scale, complying with quality parameters, notably regarding ash content. This purpose requires evaluating changes in biomass properties, such as mass and energy yields induced by the different operating conditions [ 19 ]. Specifically, assessing ash generation in its relationship with additives and the degree of interaction in biomass blends enables finding operational conditions to obtain improved products.…”

Life cycle assessment for hydrothermal carbonization of urban organic solid waste in comparison with gasification process: A case study of Southern Chile

“…In addition, Temuco and Padre de Las Casas, both located in the Region of La Araucanía (in the South of Chile), are considered one of the most polluted cities in Chile, presenting 388 critical episodes of PM 2.5 in 2016. Due to the USW management and air pollution problems, the Chilean government incentives plans and support technologies development to replace firewood with less polluting fuel 19,20 . In this context, gasification and HTC are presented as potential solutions to achieve a waste valorization 21–23 .…”

“…However, the process requirements, such as energy or water consumption, depending on biomass composition and quantity. In Chile, the OFUSW and lignocellulosic waste 19,20 have been treated by HTC at a laboratory scale, showing an increase of 30%–40% in the higher heating value in the product 21,22…”