Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Analysis on a five-spot well for enhancing energy recovery from silty natural gas hydrate deposits in the South China Sea
No full textThe five-spot well is a promising technique for enhancing the inherent low gas production rate from silty natural gas hydrate (NGH) reservoirs with low permeability in the South China Sea (SCS). However, the production characteristics and the responses to key geological and engineering factors are still unclear and warrants investigation. Herein, we first establish a three-dimensional reservoir model based on the SH2 NGH deposits at SCS with the implementation of a five-spot well. We systematically examine the gas production enhancement effect and the unexpected well-to-well interaction induced by long-term depressurization. A sensitivity analysis on the effects of bottomhole pressure (Pbtm), permeability (k) and hydrate saturation (SH) is conducted to elucidate the key factors controlling the gas production enhancement. Our results reveal that the five-spot well significantly improves the gas productivity with cumulative gas production increased to 4.12 times that of a single well over 10 years. The well interference on gas production is not significant in the early stage but becomes more significant as depressurization sustains. Due to the relatively slow pressure propagation at the inner well, contribution to gas production from the inner well decreases over time while the outer wells increase. Based on the sensitivity analysis, gas production increases with decreasing P btm , increasing k , and decreasing SH H with P btm and k as the key controlling factors. The findings provide valuable design basis for the adoption of a multi-well system in enhancing gas production for targeted NGH reservoirs in the next field production trial at SCS
Impact of Steep Seabed Terrains on Oscillating Buoy-Wave Energy-Converter Performance
No full textThis paper employs Computational Fluid Dynamics (CFD) methods to develop a numerical model of an oscillating buoy-wave energy converter and investigates the impact of steep seabed topography near islands and reefs on its performance. The model's accuracy is validated by comparison with experimental results from the published literature. Subsequently, the influence of deployment location, reef-front slope gradient, and reef-flat water depth on the device's performance is analyzed. The results indicate that the strategic utilization of steep seabed topography can significantly enhance the energy capture efficiency of the device in long-wave regions. This study provides valuable references for the design and deployment of oscillating buoy-wave energy converters in near-reef areas
Impact of Steep Seabed Terrains on Oscillating Buoy-Wave Energy-Converter Performance
No full textThis paper employs Computational Fluid Dynamics (CFD) methods to develop a numerical model of an oscillating buoy-wave energy converter and investigates the impact of steep seabed topography near islands and reefs on its performance. The model's accuracy is validated by comparison with experimental results from the published literature. Subsequently, the influence of deployment location, reef-front slope gradient, and reef-flat water depth on the device's performance is analyzed. The results indicate that the strategic utilization of steep seabed topography can significantly enhance the energy capture efficiency of the device in long-wave regions. This study provides valuable references for the design and deployment of oscillating buoy-wave energy converters in near-reef areas
Different macrophytes and eutrophic gradients regulate microbial communities of phytoremediation for eutrophication pollution and carbon reduction
No full textPhytoremediation on eutrophicated ecosystems has received growing research interest, and macrophytes and eutrophic gradients are considered as key influencing factors. This study used Vallisneria natans, Iris pseudacorus, and their mixed plantings in aquatic ecosystems (9 m x 2 m x 0.5 m, L x W x D) receiving increased eutrophic nitrogen and phosphorus gradients (4, 40, 80 mg/L of nitrogen and 0.4, 4, 8 mg/L of phosphorus), to unveil phytoremediation effects and corresponding microbial mechanisms. Different phytoremediations could effectively improve water quality with removal efficiencies of 57.4%-98.7% on ammonium, 45.7%-93.7% on total nitrogen, 46.7%-100% on available phosphorus, and 38.4%-95.2% on total phosphorus, respectively. Macrophytes and eutrophic gradients jointly affected diversities, compositions, structures, interactions, and functions of sedimental bacterial and archaeal communities. Microbial diversities increased with macrophytes presence and increased eutrophic gradients. Principal component analysis demonstrated that different macrophytes diverged microbial community structures, and increment of eutrophic gradients reduced structural dissimilarities. Dominant compositional communities, including Chloroflexi, Firmicutes, Proteobacteria, Anaerolineae, and Nitrososphaeria, were also keystone taxa of community co-occurrence networks in phytoremediations. Increased eutrophic gradients enhanced microbial cooperative interactions, whilst V. natans fostered bacterial interactions, and I. pseudacorus and mixed plantings strengthened archaeal interactions. Functional prediction indicated that bacterial "phosphate transferase" and archaeal "methanogenesis" were significantly reduced, whilst archaeal "nitrification", "denitrification", "comammox", and "methane oxidation" were elevated by macrophytes and eutrophic gradients, indicating likely mechanisms for nutrient and GHGs metabolisms. This study extended our knowledge on microbial mechanisms of phytoremediations with different macrophytes treating eutrophicated waters of increased gradients, therefore providing references for further developing phytoremediation technologies
Comprehensive analysis of the characteristics of tobacco stalk in-situ and cooling biochar
No full textCurrently, most kinetic research on the thermal conversion process of char is focused on cooling char. However, the significant disparity in physicochemical properties between cooling char and in-situ char makes studying char gasification kinetics challenging. In this study, in order to assess the impact of different cooling processes on the char while mitigating the influence of inorganic elements, the preparation of char with four varying cooling rates was carried out using demineralized tobacco stalk. Firstly, the gasification reactivity of the cooling char was determined using thermogravimetric analysis. The results indicated that a higher cooling rate led to char reactivity closer to the in-situ state. Subsequently, the char was characterized in terms of its skeletal structure, chemical functional groups, micromorphology, pore size distribution, and surface active sites. The objective was to analyze the impact of cooling on the physicochemical structure of char, probe into the reasons behind variations in char gasification reactivity, and search for the relationship between various cooling rates, the degree of graphitization, and the active site of char. The findings revealed that the cooling treatment had a significant influence on the skeletal structure and pore structure of the char, resulting in variations in the number of active sites. When the cooling rate increases from 0.04 K/s to 1.35 K/s, 2.39 K/s, 5.78 K/s respectively, the degree of graphitization decreases by 7.48 %, 11.02 %, and 32.68 %, the chemical adsorption capacity (active sites) of CO2 2 increased by 5.15%, 9.28%, and 26.80%. During the cooling process, the temperature gradient generated stress, leading to fragmentation of the char and subsequently affecting the number of pores. However, the cooling treatment had minimal impact on the chemical functional groups and pore size distribution of the char. The main reason for the decrease in reactivity of cooling char is that the pore structure is irreversibly damaged
Plant performance and soil-plant carbon relationship response to different biochar types
No full textBiochar (BC) applications in soil has positive effects on plant performance, particularly for loose soil in agricultural context. However, how biochar types affect plant performance of non-crop species and soil-plant carbon relationships is not clear. We selected five different BC types and three plant species to investigate the responses of plant performance and the soil-plant carbon relationship to BC effects. The result demonstrated that peanut shell BC led to the death of both R. tomentosa and C. edithiae, due to a reduction in nutrient uptake caused by higher soil electricity conductivity (2001.7 and 976.3 mu S cm-1). However, the carbon content of S. arboricola increased by 57% in peanut shell BC-amended soil, suggesting that S. arboricola has a higher tolerance for soil salinity. Wood BC-amended soil led to better stomatal conductance (gs) and leaf area index (LAI) of both R. tomentosa and C. edithiae due to the higher water retention in the soil (22.68% and 20.79%). This illustrated that a higher amount of water retention brought by wood BC with a great amount of pore volume might be the limited factor for plant growth. The relationship between gs and LAI suggested that gs would not increase when LAI reached beyond 3. Moreover, wood and peanut shell BC caused a negative relationship between soil organic carbon and plant carbon content, suggesting that plants consume more carbon from the soil to store it in the plant. Overall, wood BC is recommended for plant growth of R. tomentosa and C. edithiae, and peanut shell BC is suggested for S. arboricola carbon storage.
Peanut shell biochar enhanced soil salinity which causes the death of R. tomentosa and C. edithiae, while wood biochar is suitable for these plant species.Wood and peanut shell biochar caused a negative relationship between soil organic carbon and plant carbon content.The stomatal conductance will not increase when the leaf area reaches the limiting value 3.An empirical function is developed to correlate plant carbon content and leaf area index under different biochar applications
Insight into high-temperature fast pyrolysis characterization, product distribution and interaction effect of municipal solid waste and its components under steam-containing hydrogen-rich syngas atmosphere
No full textThis research delves into the field of fast hydropyrolysis of mixed municipal solid waste (MSW), with the goal of understanding product distribution and interactions in a hydrogen-rich condition. Through experimental investigations on MSW and its components, this study thoroughly examines the impact of pyrolysis temperature and gasification atmosphere (30 % H2+30 % CO+20 % CO2+20 % H2O) on the yields and distribution of the three-phase products. As the temperature increases, the gas yield gradually increases, while the yields of tar and char gradually decrease. The introduction of a hydrogen source increases the methane content in the combustible gas, which generally reaches its maximum at 850 degrees C, and promotes aromatic formation in tar, making aromatics the main component of pyrolysis oil. Notably, aromatics have the highest-octane number in gasoline. This study highlights gasification as a promising technology for converting organic waste into valuable fuel, advancing waste management and energy recovery
Removal performance of Nitrogen, sulfur and chlorine pollutants during chemical looping combustion of textile dyeing sludge using red mud as an oxygen carrier
No full textTextile dyeing sludge (TDS) is a solid waste produced by the textile industry, which contains a large number of N, S and Cl components. Direct heat treatment of TDS will cause a large number of N, S, Cl pollutants to be released. This study verified the possibility of chemical looping combustion (CLC) of TDS using alkaline WS900 red mud (RM) oxygen carrier, which is rich in Na/Ca, to remove N, S and Cl pollutants at the same time. Raising the reaction temperature in the range of 750-900 degrees C, prolonging the residence time and increasing the oxygen excess coefficient can promote the oxidation performance of WS900 to NOx precursor, while CO2 atmosphere inhibits the oxidation ability. After 10 cycles of CLC, the Cl fixation rate of WS900 is still close to 100% and its S fixation rate is more than 97%. It can maintain more than 90% of carbon conversion and 86% of CO2 selectivity. Compared with the pyrolysis condition, the removal rate of N pollutants is about 67%. Alkaline RM is also neutralized after absorbing acid gases during CLC, which is convenient for its further treatment and utilization
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