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A thermal energy storage–updraft gasification device is a type of reactor that should be considered for use in solid waste gasification research that can save energy. However, the operating parameters and internal flow field during its operation remain unclear. In this study, a numerical model of the thermal energy storage–solid waste gasification device based on the computational fluid dynamics dense discrete phase model (CFD-DDPM) which had almost never been used before was established, and an innovative method that causes particles to be piled to simulate the gasification process was proposed according to the updraft fixed bed gasification characteristics; meanwhile, solid waste gasification experiments were conducted on the device. This study focused on the influence of moisture content and excess air coefficient on the gasification process of solid waste particles, and the velocity, pressure, temperature, and species distribution of the internal flow field of the device were analyzed. Simulation results showed that the higher the moisture content of particles, the greater the amplitude of changes in the internal physical field of the device. The fluid pressure drop is around 25 Pa–75 Pa for different working conditions. The combustible species of the gas of moist particles raise slightly with the increase in excess air coefficient, while the dry particles have the opposite effect. Compared with other gasification devices of the same type, the hydrogen production of this device is about 2–3 times higher. Our findings could facilitate the analysis, predict the operation status, and provide a theoretical basis for the improvement of this device. [ABSTRACT FROM AUTHOR]

A thermal energy storage–updraft gasification device is a type of reactor that should be considered for use in solid waste gasification research that can save energy. However, the operating parameters and internal flow field during its operation remain unclear. In this study, a numerical model of the thermal energy storage–solid waste gasification device based on the computational fluid dynamics dense discrete phase model (CFD-DDPM) which had almost never been used before was established, and an innovative method that causes particles to be piled to simulate the gasification process was proposed according to the updraft fixed bed gasification characteristics; meanwhile, solid waste gasification experiments were conducted on the device. This study focused on the influence of moisture content and excess air coefficient on the gasification process of solid waste particles, and the velocity, pressure, temperature, and species distribution of the internal flow field of the device were analyzed. Simulation results showed that the higher the moisture content of particles, the greater the amplitude of changes in the internal physical field of the device. The fluid pressure drop is around 25 Pa–75 Pa for different working conditions. The combustible species of the gas of moist particles raise slightly with the increase in excess air coefficient, while the dry particles have the opposite effect. Compared with other gasification devices of the same type, the hydrogen production of this device is about 2–3 times higher. Our findings could facilitate the analysis, predict the operation status, and provide a theoretical basis for the improvement of this device.

[Display omitted] Supercritical water processes include supercritical water (SCW) oxidation (SCWO) and supercritical water gasification (SCWG). These are promising green technologies to address critical solid waste and wastewater management challenges, and in producing clean and renewable energy. Both SCWO and SCWG can use catalysts to improve reaction performance, such as to treat biomass at more moderate temperatures in SCWO processes, and to increase selectivity for production of more desirable gas products in SCWG processes. Heterogeneous catalysis has shown to be advantageous compared to homogenous catalysis for SCW processes. This paper reviews literature on heterogeneous catalysis applied to SCWO and SCWG process from the past decade, by focusing on catalyst preparation, characterization, and mechanisms, primarily for wastewater treatment and biogas production applications. The findings show that metal oxide catalysts such as Ag 2 O, CeO 2 , CuO, Fe 2 O 3 , MgO can enhance SCWO of biomass. On the other hand, transition metal catalysts (mainly nickel- and ruthenium-based catalysts) have been more often used for SCWG of biomass in SCW, compared to metal oxides, noble metals, zeolites, and carbon-based catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Evolutionary behavior of syngas characteristics evolved during the gasification of cardboard has been examined using a batch reactor with steam as a gasifying agent. Evolutionary behavior of syngas chemical composition, mole fractions of hydrogen, CO and CH4, as well as H2/CO ratio, LHV (kJ/m3), hydrogen flow rate, and percentage of combustible fuel in the syngas evolved has been examined at different steam to flow rates with fixed mass of waste cardboard. The effect of steam to carbon ratio as affect by the steam flow rate on overall syngas properties has therefore been examined. A new parameter called coefficient of energy gain (CEG) has been introduced that provides information on the energy gained from the process. This new parameter elaborates the importance of optimizing the sample residence time in the reactor. [Copyright &y& Elsevier]