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 x101 to 1.412x105 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 R2 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.

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

“…On the other hand, no significant differences were found between the R 2 and RMSE showed in the previous subsection (0.81 and 4.3 %, respectively) and the reported values by earlier studies with models to predict MY in specific biomasses [14,42] and blends [11] . Indeed, the equations for MY obtained by Multiple Linear Regression and Regression Trees [13] indicated an R 2 of 0.85 and an RMSE of 6 %. The proposed kinetic model presented an average error with the validation data set of 2.3 and 3.5 % for sawdust and raps, respectively.…”

“…Currently, the hydrochar is used as a biofuel in boilers and stoves [5] , as a precursor of activated carbon [6] , catalysts [7] , capacitors, among others [8,9] . The HTC has been deeply studied in some key areas, such as maximize the energy yield by analyzing the influence of the operating parameters and type of biomass treated [10][11][12][13] and the study of elemental and complex kinetics for specific biomasses [14][15][16][17] . Besides, economic and feasibility analysis have been carried out to scale the process in batch and continuous pilot plants [18][19][20] and to evaluate the environmental impact [21] .…”

“…An increase in reaction time causes the biomass to move along the paths of these reactions in all cases considered [28] . Some studies have been developed to get a valid model to describe the biomass conversion in hydrochar evaluating mass yield (MY) and HHV, mainly linear regression models [12,13,29] . On the other hand, there is no general kinetic model for biomass available from the literature.…”

Hybrid porous media gasification of urban solid waste pre-treated by hydrothermal carbonization

“…More recently, Lin et al (2020) suggested that gasification coupled with HTC was a practical approach to producing hydrogen-rich gas from MSW [17]. Thus, this research assesses the HTC and gasification integration efficiency for the best MSW biomass blend found in prior studies [18].…”

“…Regarding the pretreatment process, a reactor of 5 L was used for this process, using 1.0 kg of raw material and a 1:10 ratio of dry biomass and water. Note that the moisture contents of sludge, residual food, and pruning were 75.4, 83.2 and 52.9%, respectively; thus, the moisture content for the blend was 80.2 [13,18], and 1.98 liters of water were added in the reactor [18]. The blend was treated by hydrothermal carbonization for one hour at 220˚C, which were optimal operational conditions determined to maximize energy yield [18,19].…”