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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]

Ultra-small biomass gasification and power generation systems are a promising technology for disaster areas in developed countries and non-electrified rural areas of developing countries. The gasification characteristics of carbonized wood pellets and carbonized wood briquettes without or with 1 wt% sea salt were tested in a pilot-scale updraft fixed-bed gasifier. The results showed that the carbon balance during gasification was easily achieved, and most of the chlorine in the carbonized briquettes with sea salt remained in the residual char and fly ash after gasification. Inorganic chlorine in the solid fuel was transformed into organic chlorine combined with carbon matrix after heat treatment in the gasifier. Syngas with a low heating value higher than 4 MJ·m −3 could be continuously obtained when the system reached a stable condition, which enabled power generation using a gas engine. A combination of several secondary tar removal processes was adopted for the syngas purification. The tar content in the syngas after the gas cleaning for 425 °C-carbonized pellet, 425 °C-carbonized briquette, 475 °C-carbonized briquette, and 475 °C-carbonized briquette with sea salt was 0.98, 0.26, 1.4, and 0.2 g·Nm −3 , respectively. During the stable stage, 425 °C-carbonized pellet showed the highest cold gas efficiency (CGE) of 45.6% and carbon conversion efficiency (CCE) of 57.8%, respectively, with an equivalence ratio (ER) of 0.24. A lower carbonization temperature showed a higher CGE and CCE. The residual char and fly ash after gasification could be considered for reuse as feedstock to further improve the overall process efficiency. The maximum output power was 23 kW at an air flow rate of 40 Nm 3 /h during the gasification of carbonized pellets, and the corresponding overall power generation efficiency of the engine using the syngas was about 27.8%. For 475 °C carbonized briquette, the maximum output power was 18 kW at an air flow rate of 40 Nm 3 /h, and the corresponding overall power generation efficiency of the engine using the syngas was about 25.5%. [ABSTRACT FROM AUTHOR]

Small-scale, distributed and low cost biomass power generation technologies are highly required in the modern society. The biomass pretreatment process, that is, a combination of carbonization and pelletization processes of cedar wood were explored in this study. For the carbonization process, a novel carbonizer composed of one carbonization chamber and one combustion chamber was tested, and the mass and energy balances during cedar wood carbonization at 400–500 °C were analyzed, respectively. During the initial heating stage, about 22 kg of wood with dry basis should be supplied into the combustion chamber through several batches. When the temperature in the carbonization chamber reached to the range of 200–220 °C, the combustion chamber could be self-heated by burning the pyrolysis gas (tar vapor, CH 4 , H 2 , CO) sent from the carbonization chamber. The specific wood consumption for producing 1 kg of wood char was within 3.6–4.4 kg, which presented an increase trend with increasing the carbonization temperature. Moreover, this carbonization system can deal with different kinds of biomass with various water contents and shapes. For the pelletization process, effects of adding amount of the binder (poval solution), water and the carbonization temperature on the pellet quality were studied so as to explore the optimal condition for making high quality pellets from the crushed wood char. The results indicated that there was an optimal ratio among char, added water, and the binder for making high quality pellets. Considering the energy transfer efficiency and pellet quality, the mass ratio of 0.93:0.32:0.10 for 450 °C-char in the dry basis: added water plus water in char: poval solution was the optimal condition for making high quality pellets. [ABSTRACT FROM AUTHOR]

In this work, a heating stage microscope and a thermogravimetric analyzer were adopted to explore behaviors of char-slag/ash transition during CO 2 gasification of rice straw (RS) and Neimeng lignite (NM). Effects of demineralized treatment and various gasification temperatures on the char-slag/ash evolution process were studied. Both RS and NM particles exhibited shrinkage particle form at a moderate reaction temperature (1000 °C). The variation of the existential state of K with char-slag/ash transition could well explain the reactivity differences between RS raw char and demineralized char. Compared to RS raw char, NM raw char showed a more significant flow of molten slag at 1350 °C, which accounted for the high inhibitory effects at the late stage of NM raw char gasification. There is a threshold conversion (x = 0.9) during the evolution processes of NM char samples to NM slag/ash at 1200 °C and 1350 °C, while this threshold value is only existing at 1000 °C for RS char gasification. [ABSTRACT FROM AUTHOR]

Rapid pyrolysis characteristics of three different rank coals and two petroleum cokes were investigated using a drop tube furnace. Moreover, gasification characteristics of char samples were studied in an in-situ heating stage. The results showed that H 2 and CO were the main gaseous pyrolysis products of coal samples. The relative content of H 2 and CO increased with increasing pyrolysis temperature. The volume fraction of H 2 in syngas increased with increasing coal rank, whereas that of CO showed the contrary trend. Anthracite and petroleum cokes (Petcoke 1 and Petcoke 2) exhibited a great similarity in gas release characteristics. There was a maximum value for the specific surface area and graphitization degree of char samples with increasing pyrolysis temperature. The results of in-situ heating stage experiments indicated that the most of char particles reacted with CO 2 in the shrinking particle mode at the initial stage. Char samples of petcokes and anthracite were similar in slow consumption of particle skeleton during gasification. Interestingly, petcokes demonstrated particle migration, residual agglomeration, and rapid consumption at the later reaction stage. The variation trend of the area shrinkage ratio of char samples was well verified by the TGA results. [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]

• 300 °C torrefaction reduced gasification reactivity mainly in midterm and late stage. • Low-temperature torrefaction had slight effect on char gasification reactivity. • Gasification kinetics were analyzed based on the gas-solid reaction methods. • Pathways of char structure evolution changed after 800 °C pyrolysis. • Gasification reactivity decreased significantly for chars pyrolyzed after 800 °C. In this study, the effect of torrefaction on the gasification reactivity of chars from raw and torrefied biomass was investigated. Three torrefaction temperatures and four pyrolysis temperatures were taken into consideration. It was found that the severe torrefaction (300 °C) would reduce the char gasification reactivity by at least 19% according to the normalized gasification rate. Moreover, the reduction of gasification reactivity appeared after the midterm stage. The gasification reaction were further analyzed by nucleation/growth model and model-free method. The activation energy increased by ~80 kJ/mol with conversion, indicating an enhancement of the reaction resistance. Furthermore, 800 °C pyrolysis was found to be a turning point, beyond which the gasification reactivity reduced significantly. These reactivity changes were implied by the bio-char structure evolution and active alkali and alkaline earth metals (AAEMs) contents variations. The research results provide insights into the effect of torrefaction on biomass gasification. [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]

The effects of alkali and alkaline earth metals (AAEM) on the component and distribution of products, gasification reactivity, catalytic mechanism and char-ash/slag transition during biomass gasification were reviewed. Biomass is mainly composed of cellulose, hemicellulose and lignin, and has a much higher AAEM species content than coal. The influence of inherent AAEM on biomass gasification is closely related to the gasification agent and operating conditions. To remove tar and reduce soot, interest has grown on the subject of AAEM catalysis for biomass gasification. Therefore, component and distribution of products and gasification reactivity in inherent and loaded AAEM catalytic biomass gasification were reviewed. Furthermore, the effects of AAEM on biomass conversion can be divided into homogeneous and heterogeneous catalytic effects based on the phase states involved in chemical reactions. Three main mechanisms including oxygen transfer mechanism, active site mechanism and catalytic desorption mechanism are summarized to understand the heterogeneous catalytic process. The attribution to the promotion of the homogeneous reaction is concluded as the volatile gaseous AAEM catalyzed the water-gas shift reaction and the hydrocarbon reforming reaction. In addition, the effects of AAEM content on char-ash/slag transition in biomass gasification were also reviewed. • Biomass component gasification characteristics are summarized and compared. • Product distribution and reactivity of biomass gasification are reviewed. • Three main AAEM catalytic biomass gasification mechanisms are summarized. • Effect of AAEM on char-ash/slag transition during gasification is discussed. [ABSTRACT FROM AUTHOR]

Biomass gasification is a promising technology in current and future low carbon energy systems. Soot formation is a great technical challenge for the industrialization of biomass gasification that is inevitable at high temperature and fuel rich conditions. In this review, a comprehensive summary of soot formation in biomass gasification is provided with special focus on entrained flow technologies. The topics covered the state of the art knowledge of soot formation in different gasifiers, the fundamental knowledge, experimental methods and recent control strategies. Soot generation and oxidation mechanism are discussed while the relationship between soot, tar and char in biomass gasification are analyzed in detail. Reaction models for soot formation coupled to the gasification process are introduced, including (semi-)empirical and detailed models. Effect of biomass components and ash forming elements on soot formation are highlighted. This is followed by a detailed description of in-situ and ex-situ experimental measurements, such as the optical diagnostics, aerosol particle mass analyzer and mass spectrometer. Soot formation characteristics and properties in different types of gasifiers are then addressed in detail with an emphasis of entrained flow gasifiers. Finally, the soot control strategies in biomass gasification are reviewed and evaluated. This review concludes by summarizing the available knowledge and challenges in soot formation during biomass gasification. • State-of-the-art knowledge of soot formation in different gasifiers is reviewed. • Mechanism and model of soot formation and oxidation are summarized. • Effect of biomass components and ash on soot formation are highlighted. • Flow manipulation technique and catalytic gasification could suppress soot formation. [ABSTRACT FROM AUTHOR]