Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Machine learning-driven optimization of Ni-based catalysts for catalytic steam reforming of biomass tar
No full textBiomass gasification is a promising process for producing syngas, which is widely used in various industrial processes. However, the presence of tar in syngas poses a significant challenge to biomass gasification due to the difficulties in its removal and potential downstream issues, such as clogging, slagging, and corrosion. Extensive efforts have been made to address this challenge through catalytic tar removal using various catalysts, generating a vast amount of experimental data. Processing this large dataset and gaining new insights into process optimization requires the development of efficient data analysis methods. In this study, a comprehensive database was built, encompassing a total of 584 data points and 14 input parameters collected from literature published between 2005 and 2020. Machine learning algorithms were then trained using this dataset to predict and optimize the catalytic steam reforming of biomass tar. The predicted results were found to agree well with the experimental data. The results show that the reaction temperature is the most important process parameter, with the highest relative importance of 0.24, followed by the support (0.16), additive (0.12), nickel (Ni) loading (0.08), and calcination temperature (0.07), among the 14 input parameters. This work has proposed optimal ranges for the reaction temperature (600-700 degrees C), Ni loading (5-15 wt%), and calcination temperature (500-650 degrees C). Furthermore, it was found that a larger specific surface area and higher Ni dispersion are two critical factors for selecting additives and supports. This study provides insights into key parameters for optimizing the catalytic steam reforming of biomass tar, enabling enhanced efficiency and effectiveness in biomass gasification processes
Zero/negative carbon emission coal and biomass staged co-gasification power generation system via biomass heating
No full textCurrently, most coal utilization technologies cannot completely remove CO2, which hinders coal utilization in the context of carbon neutrality. Staged coal-steam gasification has proven to be a potential clean coal utilization method suitable for power generation. However, it cannot achieve zero or negative carbon emissions, and there is the potential to improve energy efficiency further. This study introduces biomass into staged coal gasification and proposes a novel power generation system based on coal-and biomass-staged co-gasification via biomass external combustion heating. Biomass with a lower energy level was combusted to provide heat for gasification, thus improving the energy level matching between the gasification and biomass combustion reactions. The synergistic effect of coal and biomass reduces the tar yield and improves the gasification efficiency. Furthermore, as a carbon-neutral fuel, the introduction of biomass in the staged coal-gasification process can achieve zero or negative carbon utilization of coal. The entire system was simulated using the ASPEN PLUS software, key pro-cesses were experimentally validated, and the energy efficiency and carbon emission performance were sys-tematically studied. The results indicated that the improved gasification methods and the synergistic effect between coal and biomass significantly improved the energy performance and emission reduction characteristics. The power efficiency of the novel system was the highest at 40.03% when the biomass blending ratio of the co -gasification sub-process was 0.8, which was 5.27% and 10.46% higher than conventional integrated gasification combined cycle (IGCC) system and biomass direct-fired power plant. The carbon-specific emissions of the novel system could be reduced to-308.1 kgCO(2)/MWh, achieving negative carbon utilization of fossil fuels. This novel staged coal and biomass co-gasification method heating by biomass can achieve efficient and negative carbon utilization of fossil fuels
Medium and long-term hydrogen production technology routes and hydrogen energy supply scenarios in Guangdong Province
No full textHydrogen is a type of clean secondary energy, and the hydrogen energy supply is vital to regional energy development. Guangdong is at the forefront of hydrogen energy deploy-ment in China, and aims to achieve peak carbon by 2030. However, hydrogen production research is challenging due to complex technical routes, technical maturity levels, life -cycle carbon emissions, and costs. Multi-time-scale research is necessary to explore optimal production paths and their contributions to CO2 emission reduction. This study discussed key technologies and the technical maturity of five hydrogen production routes: production from industrial byproducts and coal, wind, hydro-, and photovoltaic power. Policy scenarios were designed to investigate the potential of these routes and technology deployment intensity under medium-and long-term scenarios. This paper proposes a roadmap for hydrogen development and provides a reference for hydrogen production planning in Guangdong. This methodology can be applied in other regions for hydrogen energy development research.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
Study on the ignition characteristics of CH4/H2/air mixtures in a micro flow reactor with a controlled temperature profile
No full textThe ignition characteristics of stoichiometric CH4/H2/air mixtures with different H2 dilu-tion ratios were studied by using a micro flow reactor (MFR) with a controlled temperature profile. The weak flame positions of the mixtures were determined by the luminosity of CH*, and the ignition temperatures (defined as the corresponding wall temperatures) were obtained. The ignition temperature of the mixture is smoothly decreased with a small amount of H2 addition, while the decrease of the ignition temperature is more rapid with increasing H2 dilution. One-dimensional computation with a detailed reaction mechanism was also conducted to study the ignition characteristics of the CH4/H2/air mixtures. The computational ignition temperature which is defined as the wall temperature at the peak of the heat release rate (HRR) peak is also obtained. Both the experimental and computa-tional results show that the weak flame shifts to the lower temperature region with an increase of the H2 mole fraction. And the non-linear decrease of the ignition temperature of the CH4/H2/air weak flame versus increasing H2 dilution was also well reproduced by the numerical computation. The flame structures, primary exothermic and endothermic re-actions of the CH4/H2/air weak flames were studied in detail. The importance of H and OH in the ignition process of the mixtures was analyzed, and the kinetic effects of H2 on the ignition of the mixture in the intermediate-temperature region (1000-1200 K) and high -temperature region (1200-1300 K) were elucidated. The analysis of the computational re-sults reveals that the OH production routes in the intermediate-temperature region are substantially changed with different H2 dilutions, while the OH production routes at the peak of the heat release rate are not obviously influenced. In the end, the primary mech-anism for the non-linear effects of H2 addition on the ignition temperatures of the CH4/H2 mixtures was clarified.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved
Clay mineral as catalysis for controlling the nitrogen containing pollutants during sewage sludge pyrolysis
No full textPyrolysis technology is considered one of the most promising processes for the environmentally friendly disposal of sewage sludge (SS), as it can neutralize pathogens, reduce hazardous substances, and promote the immobilization of heavy metals. However, nitrogen -containing gases produced in SS pyrolysis can be converted to nitrogen oxides, causing serious environmental pollution. In this study, we investigated the evolution of the nitrogen (N) element in rapid pyrolysis of SS and explored the effect of clay minerals (attapulgite, montmorillonite, and kaolin) in regulating N conversion. The results showed that the higher temperature (800 degrees C) could promote the conversion of pyrroles/pyridines and NOx precursors in char to N2 (the conversion rate was 32.76 %), and clay minerals catalyzed the cleavage of N -containing macromolecules in the bio-oil, reducing the N content in bio-oil from 28.70 % to 6.23 %, and was conducted to realize the denitrification of bio-oil. Notably, the attapulgite (ATP) on N migration was more effective and could reduce the yield of NOx precursors from 23.80 % to 10.55 % by capturing NH4* and inhibiting the secondary reaction, while catalyzing the removal of N2 from pyridine/pyrrole (N2 production increased to 34.38 %). MgO and CaO in the clays played a major role in facilitating the conversion of char -N to N2, and clay structures loading on the biochar surface promoted the catalysis of N -containing volatiles to N2 by metal oxides. This study provides a viable and harmless approach to SS minimization
Molecular dynamics simulation study of the cosine oscillation electric field's effect on methane hydrate growth
No full textCosine oscillation electric field could be a promising option to fasten methane hydrate formation in pure water. Molecular dynamics simulation was employed to examine the performance of cosine oscillation electric field in the intensity range of (0.5-2.0) V center dot nm(-1) and frequency range of (0.2-1.0) THz. The hydrate growth time and the hydrate growth rate were firstly defined and obtained by calculating the four-body structure order parameter for different systems at different x positions. The results showed that the added electric field with appropriate parameters could promote methane hydrate formation significantly, represented by shorter hydrate growth time and higher hydrate growth rate. In all studied systems, system with 1.5 V center dot nm(-1) intensity and 0.4 THz field intensity was recommended for fast hydrate growth rate, which could be three times higher than that of system without electric field. It was noteworthy that there was an electric field frequency boundary, lower than which the effect of cosine oscillation electric field on methane hydrate formation could be totally different. The electric field frequency boundary for systems with different electric field intensities was identified and fitted with two exponential growth functions
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