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Abstract Hydrothermal liquefaction (HTL) of biomass into biocrude is attractive but the biocrude themselves are poor fuels, which need to be upgraded for further utilization. Compared with the traditional catalytic upgradation process, a non-catalytic method for biocrude upgrading in the aqueous waste (HTL-AW) derived from HTL of cornstalk was proposed. Optimal reaction conditions of upgradation process were obtained at 356 °C (temperature), 37 min (reaction time) and 19 mL/g (HTL-AW/biocrude) based on the response surface methodology. The biocrude was effectively upgraded in the HTL-AW and a high hydrogen to carbon effective (H/Ceff) ratio of 1.07 with a higher heating value of 36.94 MJ/kg was observed. The energy recovery of ∼80% from biocrude to upgraded biocrude was feasible. GC–MS analysis showed that the contents of phenols and ketones were decreased from 65.61% to 48.38% and 22.39%–16.78%, respectively, while the contents of nitrogen-containing compounds n-hexadecanoic acid were increased from 2.25% to 10.15% and 9.56%–22.23%, respectively. The high H/Ceff was attributed to the promoted deoxygenation by alkali and alkaline earth metals as well as H+ enriched in the HTL-AW. This study demonstrates the feasibility of improving the H/Ceff of biocrude in the HTL-AW under a relatively mild reaction condition.

Abstract Hydrothermal liquefaction (HTL) of biomass into biocrude is attractive but the biocrude themselves are poor fuels, which need to be upgraded for further utilization. Compared with the traditional catalytic upgradation process, a non-catalytic method for biocrude upgrading in the aqueous waste (HTL-AW) derived from HTL of cornstalk was proposed. Optimal reaction conditions of upgradation process were obtained at 356 °C (temperature), 37 min (reaction time) and 19 mL/g (HTL-AW/biocrude) based on the response surface methodology. The biocrude was effectively upgraded in the HTL-AW and a high hydrogen to carbon effective (H/Ceff) ratio of 1.07 with a higher heating value of 36.94 MJ/kg was observed. The energy recovery of ∼80% from biocrude to upgraded biocrude was feasible. GC–MS analysis showed that the contents of phenols and ketones were decreased from 65.61% to 48.38% and 22.39%–16.78%, respectively, while the contents of nitrogen-containing compounds n-hexadecanoic acid were increased from 2.25% to 10.15% and 9.56%–22.23%, respectively. The high H/Ceff was attributed to the promoted deoxygenation by alkali and alkaline earth metals as well as H+ enriched in the HTL-AW. This study demonstrates the feasibility of improving the H/Ceff of biocrude in the HTL-AW under a relatively mild reaction condition.

Abstract Effective utilization of solar energy resource enables to improve the thermal performance of solar evacuated tube. In present work, the back side of solar vacuum tube was coupled with mini-compound parabolic concentrator (mini-CPC). The thermal characteristics of the presented mini-CPC solar vacuum tube were analyzed theoretically and experimentally. A mathematical model of heat transfer for the mini-CPC vacuum tube was established according to the energy conservation, and solved by iterative calculation based on home-built C programming language. The obtained numerical solutions fit in well with the experimental results. Furthermore, analysis indicates the vacuum interlayer plays a crucial role in hindering heat transfer. The thermal-convection resistance (Rco-air,conv) dominates the heat loss from cover tube to ambient rather than thermal-radiation resistance (Rco-sky,rad). The measured final temperature increment of working water for the mini-CPC and ordinary evacuated tube can reach 63.4 K and 49.8 K, respectively. An experimental result also reveals that the thermal efficiency of the mini-CPC vacuum tube is increased by 24.3%–29.2% compared with that of vacuum tube without mini-CPC, considering various weather conditions. Consequently, the designed mini-CPC evacuated tube shows a preferable performance, which may provide a certain reference in technology for engineering applications.

Abstract Effective utilization of solar energy resource enables to improve the thermal performance of solar evacuated tube. In present work, the back side of solar vacuum tube was coupled with mini-compound parabolic concentrator (mini-CPC). The thermal characteristics of the presented mini-CPC solar vacuum tube were analyzed theoretically and experimentally. A mathematical model of heat transfer for the mini-CPC vacuum tube was established according to the energy conservation, and solved by iterative calculation based on home-built C programming language. The obtained numerical solutions fit in well with the experimental results. Furthermore, analysis indicates the vacuum interlayer plays a crucial role in hindering heat transfer. The thermal-convection resistance (Rco-air,conv) dominates the heat loss from cover tube to ambient rather than thermal-radiation resistance (Rco-sky,rad). The measured final temperature increment of working water for the mini-CPC and ordinary evacuated tube can reach 63.4 K and 49.8 K, respectively. An experimental result also reveals that the thermal efficiency of the mini-CPC vacuum tube is increased by 24.3%–29.2% compared with that of vacuum tube without mini-CPC, considering various weather conditions. Consequently, the designed mini-CPC evacuated tube shows a preferable performance, which may provide a certain reference in technology for engineering applications.

Abstract The sale of value-added byproducts from hydrogen-generating reactions is a strategic approach to lower the costs of hydrogen fuel in order to realize a truly sustainable hydrogen economy. Metal hydrolysis is a chemical process that produces hydrogen together with a metal hydroxide species; however, this reaction is rarely observed without chemical additives or extreme reaction conditions. Previously, we demonstrated that hierarchical nanoporous aluminum can create hydrogen at standard conditions for temperature and pressure via hydrolysis without any additives. The advantage of this method is the co-production of pure aluminum hydroxide (Al(OH)3). Here we explore the transformation of this Al(OH)3 hydrolysis byproduct into valuable materials to elucidate strategies in reducing the overall cost of hydrogen generated. In particular, we demonstrate in this work that (i) the synthesis of hierarchical nanoporous aluminum is scalable to meet the needs of large-scale production for a hydrogen economy, and (ii) the Al(OH)3 hydrolysis byproduct can be transformed to create high surface-area “activated alumina” (Al2O3) as a commercially viable product.

Abstract The sale of value-added byproducts from hydrogen-generating reactions is a strategic approach to lower the costs of hydrogen fuel in order to realize a truly sustainable hydrogen economy. Metal hydrolysis is a chemical process that produces hydrogen together with a metal hydroxide species; however, this reaction is rarely observed without chemical additives or extreme reaction conditions. Previously, we demonstrated that hierarchical nanoporous aluminum can create hydrogen at standard conditions for temperature and pressure via hydrolysis without any additives. The advantage of this method is the co-production of pure aluminum hydroxide (Al(OH)3). Here we explore the transformation of this Al(OH)3 hydrolysis byproduct into valuable materials to elucidate strategies in reducing the overall cost of hydrogen generated. In particular, we demonstrate in this work that (i) the synthesis of hierarchical nanoporous aluminum is scalable to meet the needs of large-scale production for a hydrogen economy, and (ii) the Al(OH)3 hydrolysis byproduct can be transformed to create high surface-area “activated alumina” (Al2O3) as a commercially viable product.

Abstract Microbial fuel cells (MFCs) are potentially used for electricity generation, but their low power output hinders their practical application. This study presents novel, porosity binderless PPy–CS–CNT hydrogel materials, which were prepared using Fe(NO3)3 as an initiator. It can be seen from the results of SEM and swelling ratio that the prepared material had a uniform structure with rich three-dimensional porosity and showed good water retention performance. Electrochemical tests showed that the charge transfer impedance (Rct) of PPy–CS–CNT anode displayed a reduction in comparison with PPy anode (1.06 Ω vs. 2.20 Ω). And the power density of MFC with PPy–CS–CNT anode reached 364 mW m−2, which was 1.36 times as much as that of MFC with PPy anode. High-throughput sequencing results showed that the PPy–CS–CNT hydrogel bioanode exhibits good biocompatibility and selective enrichment of electrogenic bacteria. The dominant genera on PPy–CS–CNT hydrogel anode are the electroactive bacteria, Rhodopsedomonas (47.69%) and Geobacter (8.47%). Therefore, the PPy–CS–CNT hydrogel anode showed a potential for improving the electricity production performance of MFCs.

Abstract Microbial fuel cells (MFCs) are potentially used for electricity generation, but their low power output hinders their practical application. This study presents novel, porosity binderless PPy–CS–CNT hydrogel materials, which were prepared using Fe(NO3)3 as an initiator. It can be seen from the results of SEM and swelling ratio that the prepared material had a uniform structure with rich three-dimensional porosity and showed good water retention performance. Electrochemical tests showed that the charge transfer impedance (Rct) of PPy–CS–CNT anode displayed a reduction in comparison with PPy anode (1.06 Ω vs. 2.20 Ω). And the power density of MFC with PPy–CS–CNT anode reached 364 mW m−2, which was 1.36 times as much as that of MFC with PPy anode. High-throughput sequencing results showed that the PPy–CS–CNT hydrogel bioanode exhibits good biocompatibility and selective enrichment of electrogenic bacteria. The dominant genera on PPy–CS–CNT hydrogel anode are the electroactive bacteria, Rhodopsedomonas (47.69%) and Geobacter (8.47%). Therefore, the PPy–CS–CNT hydrogel anode showed a potential for improving the electricity production performance of MFCs.

Abstract In this study, three types of biomass including corn stover, radiata pine wood and rice husk in the form of pellets were gasified with steam as gasification agent in a 100 kW dual fluidised bed gasifier. Tar formation in initial devolatilization stage and its correlation to the final tar concentration in the producer gas were investigated. In addition, the yields and composition of the producer gas for each type of biomass were also examined. In the gasification experiments, operating temperature was controlled, respectively, at 700 °C and 800 °C. Silica sand was used as the bed material with an inventory of 30 kg. For simulation of the initial devolatilization stage in the steam gasification, N2 was used as fluidization agent. From this study, it is found that there was a positive correlation between tar contents in the devolatilization product gas and those in the final producer gas from gasification. In the devolatilization stage, radiata pine biomass yielded more phenols, while corn stover generated more toluene. Based on the results of this study, tar formation mechanism was proposed which is verified by the observation that more naphthalene was present in the producer gas from gasification of radiata pine while gasification of corn stover produced more biphenyl. The experimental results also show that at gasification temperature of 700 °C, the producer gas yield was the highest for corn stover followed by rice husk and then radiata pine wood. However, for gasification at 800 °C, the trend was reversed with radiata pine having the highest yield followed by risk husk and the corn stover. At both 700 and 800 °C, the radiata pine biomass produced a producer gas with higher contents of H2 and CH4 while the producer gas from rice husk had a higher content of CO and that from corn stover had a higher content of CO2, C2H4 and C2H6. These differences are closely related to the chemical composition of the biomass which was also analysed in this study. Radiata pine had a higher content of lignin (31.96 wt%), rice husk had a higher content of hemicellulose (25.30 wt%) while corn stover was rich in cellulose (69.85 wt%).