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This study presents a comprehensive numerical modeling approach to analyze and evaluate the performance of a throat biomass updraft fixed bed gasification reactor through computational fluid dynamic simulations. The numerical model uses detailed kinetics to capture the complex thermochemical processes within the gasifier. The influence of key parameters such as reactor design on the gasification efficiency and producer gas composition are systematically investigated. Also, performance metrics, including cold gas efficiency, hydrogen-carbon monoxide ratio, and producer gas heating value, are employed to quantitatively quantify the effectiveness of the throat updraft fixed bed gasification reactor to assess the reactors performance under varying configurations. The hydrogen and carbon monoxide concentrations increased by 6.5 % and 5.2 % by changing the throat diameter ratio from 0.14 to 0.33, respectively. Increased gasification efficiency is also observed, from 65.5 % to 77.84 %, within the same ratio range increase. Similarly, a 2.6 % increase is observed in the lower heating valve between the models with throat-to-diameter ratio of 0.14 and 0.33. The findings contribute to a deeper understanding of the gasification process in throat reactors, offering insights into optimization opportunities for enhanced producer gas quality and overall efficiency. • Gasification of biomass in an updraft gasifier using CFD modeling. • Throat updraft gasifiers have the high tendency of stable gasification temperature. • Gasification temperature improved as the throat ratio is increase. • High throat ratios increase the carbon conversion and cold gas efficiency. • Lower heating value increases as the throat ratio increases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Isothermal prediction based on model-free method was established. • Kinetic parameters form model-free and model-fitting method were compared. • Gasification mechanism was revealed from carbon and pore structure evolution. • The fractal dimension D 1 was related with amorphous structure. • Mesopore SSA increased by hundred times whereas active sites changed insignificantly. Biomass gasification integrated with leaching pretreatment can be conducive to the sustainable energy system. In this work, the biochar gasification was studied from structure to reactivity with the consideration of leaching pretreatment. The biochar was prepared from raw and leached corn straw (CS) and corncob (CC) in a fixed bed reactor. The gasification was performed in thermogravimetric analyzer with the emphasis on kinetic parameters comparison and reactivity prediction. The carbon and pore structure were investigated to reveal gasification mechanism. The prediction procedure based on model-free method was proposed. From the results, compared with CS, leaching pretreatment reduced gasification reactivity of CC considerably according to reactivity index and reactivity prediction. The random pore model showed the best fitting performance. Furthermore, the leaching pretreatment reduced inorganics (mainly K) in CS and CC, and removed water-soluble organics (pectin) in CC. The active sites and surface roughness in leached biochar decreased accordingly. The CO 2 gasification can activate initial biochar after pyrolysis. Specifically, the specific surface area of mesopore increased by hundred times and more active sites were also generated. However, as the gasification proceeding, the active sites and the fractional dimensions changed insignificantly for both raw and leached biochar. The leaching pretreatment mainly promoted the micropore development during gasification. The pore structure evolution was consistent with the carbon structure, which appeared to be correlated with the kinetic analysis. The research gives new insight into structure-performance correlation of biomass gasification and provides the implication for sustainable energy system based on gasification technology. [ABSTRACT FROM AUTHOR]

In this study, corn straw and rice husk were hydrothermally carbonized at 180 °C and 240 °C. The effect of hydrothermal carbonization on the biomass/hydrochar characteristics, fate of heavy metals such as As, Cr, Pb, Ti, Cd, Zn, Fe, Cu, and Ni, global reactivity of the pyrolysis and gasification of biomass and hydrochar were investigated in a thermogravimetric analyzer, followed by kinetic modeling and reactivity prediction. Results showed that hydrothermal carbonization temperature 180 °C is more suitable for producing solid fuel in terms of low heavy metals content. Higher hydrothermal carbonization temperature (240 °C) decreased O/C content and improved various characteristics of the hydrochar such as coalification degree, carbon content, higher heating value and the specific surface area. While hydrothermal carbonization conducted at lower temperature of 180 °C, was advantageous for obtaining higher energy yield efficiency and hydrochar yield. The gasification reactivity of hydrochar was more sensitive to the heating rate than the pyrolysis process. The activation energy (E a) of the pyrolysis process varied significantly with conversion, whereas the gasification activation energy changes were insignificant. Based on the reactivity prediction, the hydrothermal carbonization effect on corn straw and rice husk was almost similar. The hydrochar generated under severe hydrothermal carbonization temperature (240 °C) showed higher thermal stability during pyrolysis in comparison with gasification. Compared with the gasification of rice husk hydrochar, hydrochar gasification of corn straw had lower E a , hence requires less energy to produce syngas. The results of this research imply that biomass hydrochar is a suitable alternative option to produce pulverized solid fuel. [Display omitted] • Gasification and pyrolysis of Agriculture residues-derived hydrochars were performed. • HTC improved coalification degree and carbon content and higher heating value. • 180 °C provided a higher hydrochar and energy yields with lower HMs content. • Changes of E a variation during pyrolysis and gasification by HTC were compared. • Gasification reactivity of CS was more sensitive to HTC temperature than that of RH. [ABSTRACT FROM AUTHOR]

• Gasification phenomena of raw PKS, torrefied PKS, and steam-CO 2 are studied. • Euler-Lagrangian two-dimensional CFD model is used to investigate tar formation by modeling all components in tar together. • The gasification efficiency of torrefied-PKS is up by 29.1 % as compare to the raw-PKS. • The S-CO 2 -R and gasification temperature reduced tar concentration by 21.4 % and 20.5 % respectively. Experimental and numerical evaluation of steam and carbon dioxide gasification on torrefied palm kernel shell in an updraft fixed bed gasifier is studied. Euler-Lagrangian two-dimensional model with 15 kinetic reactions is developed to investigate tar formation in relation to torrefaction temperature, gasification temperature, and steam-to-carbon-dioxide ratio (S-CO 2 -R). The combination of steam and CO 2 had considerable effect on the tar reduction and also influenced the gaseous composition significantly when the varying parameters were compared. The results show that increasing both gasification temperature and S-CO 2 -R do enhance the H 2 production whiles drastically reducing the tar formation. The tar concentration reduced by 21.4 % and 20.5 % by changing the S-CO 2 -R from 0.4 to 2.0 and gasification process temperature from 973 and 1173 K respectively. An increase in hydrogen is also observed, from 55.5 % to 60.84 %, when the S-CO 2 -R is increased to 1.2. Similarly, 29.1 % increase is observed in gasification efficiency as compared to the raw-PKS. [ABSTRACT FROM AUTHOR]

[Display omitted] • An integration of pilot-scale HTC, gasification, and anaerobic digestion for EFB conversion was investigated. • Inherent AAEMs have significant effects on gasification products. • CO and H 2 were enhanced under CO 2 /O 2 gasification. • Liquid products from HTC can be utilized for methane production via anaerobic digestion. • The mass and energy balance revealed that the whole process could be feasible. In the context of evolving a circular economy for the palm-oil industry, this article presents a study of oil-palm empty fruit bunch (EFB) conversion and utilization within a palm-oil mill. Pilot-scale hydrothermal carbonization (HTC), washing and gasification processes, as well as anaerobic digestion of the HTC liquid product were investigated. Results showed that the fuel properties of hydrochars had improved. In terms of air gasification, char and tar products accounted for 22.7–33.8 % and 17.3–28.8 %, respectively while CO 2 /O 2 gasification resulted in 31.3–36.6 % for char and 8.5–30.8 % for tar. In general, hydrochar (HT-EFB) gave the lower tar content compared to washed hydrochar (HTW-EFB) due to the catalytic effects of alkali and alkaline earth metals. Major tar components from HT-EFB and HTW-EFB were aliphatic and monoaromatic hydrocarbons, respectively. Syngas products from air gasification of hydrochars were 39.9–56.5 %, 11.4–21.4 %, and 9.0–14.4 % for CO, H 2 and CH 4 , respectively while CO 2 /O 2 gasification products yielded 45.1–56.6 %, 11.6–24.3 %, and 9.4–14.0 % for CO, H 2 and CH 4 , respectively. The lower heating value of syngas was in the range of 4.7–6.6 MJ/Nm3 and cold gas efficiency was approximately 39.1–55.1 %. The cumulative methane from the liquid products amounted to 213.8 and 154.5 L/kg COD for food/microorganism ratios of 1:2 and 1:3, respectively. The mass and energy balance showed that the whole process is promising for future commercialization. [ABSTRACT FROM AUTHOR]