Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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A study on the thermochemical conversion characteristics of biomass mixed blast furnace slag catalyst coupled in supercritical CO2/H2O atmosphere
No full textTo reduce excessive CO2 in the environment and reutilize waste blast furnace slag, thermochemical reduction methods have become a focus of attention. The waste blast furnace slag as the catalyst, thermochemical conversion of biomass and its mixed catalyst under supercritical CO2 (scCO2)/scCO2 mixed H2O atmosphere were compared to explore the best CO2 consumed condition. The composition and thermal stability of the raw materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence spectrometer (XRF), thermogravimetric analysis (TGA) and simultaneous thermal analysis (STA), while gas chromatograph (GC), gas chromatography mass spectrometer (GC-MS), scanning electron microscope (SEM), brunauer emmette teller (BET), fourier transform infrared spectrometer (FT-IR) and X-ray diffractometer (XRD) were used to analyze the properties of the products. As a result, the scCO2 atmosphere increased the consumption of CO2 during the reaction process compared to the N2 atmosphere. Under the scCO2 mixed H2O atmosphere, the addition of the catalyst resulted in the highest H2 yield of 5.90 +/- 0.01 mol/kg, led to an increase in HE from 58.17 % to 69.16 %, and also greatly facilitated the phenolic hydroxyl groups-OH and carboxyl groups C=O on the solid products to be detached from the aromatic ring. The specific surface area of the biomass reached the optimum value of 240.83 m2/g in the CHE7 when the characteristic peaks 002 and 100 intensities displayed high stack height and lateral dimensions
Combustion characteristics of pre-vaporized<i> n</i>-heptane jet flames in hot O2/ N2/CO2 and O2/N2/H2O coflows
No full textThe liftoff height and blowout velocity of pre-vaporized n-heptane jet flame in hot coflows containing 21%O2/ 75%N2/4%CO2, 21%O2/75%N2/4%H2O, 21%O2/70%N2/9%CO2 and 21%O2/70%N2/9%H2O have been experimentally studied to compare the effects of CO2 and H2O on the combustion characteristics of liquid fuel. The combustion characteristics of pre-vaporized n-heptane jet flame in hot air coflow were also studied for comparison. The experimental results show that the liftoff height of the jet flame is increased by CO2 and H2O dilutions, and the increase of the liftoff height by the CO2 dilution is more significant. Theoretical analysis indicates that the liftoff behavior of the jet flame in different coflows can be well captured by the large-scale model. The physical and chemical effects of CO2 and H2O dilutions on the liftoff height have been compared theoretically based on the large-scale model and computation results. The measured blowout limit of pre-vaporized nheptane jet flame in different coflows show that the stability of the flame is decreased by CO2 and H2O dilutions. Moreover, the effect of CO2 dilution on the blowout limit is more significant than that of H2O dilution. A modified formula based the large-scale model was developed to interpret the blowout velocities in different coflows
Isolation and characterization of ureolytic calcifying bacteria from methane hydrate-bearing marine sediments for bio-cementation application
No full textIn bio-calcification, microbes precipitate calcium carbonate (CaCO3), forming versatile solid substances that promotes eco-friendly materials and reduce carbon emissions. Marine bacteria can generate bio-cements to strengthen dikes and combat coastal erosion. However, the role of marine bacteria in generating bio-cements for enhancing coastal structures and combating erosion is not fully understood. This study investigates the potential of CaCO3 precipitating bacteria isolated from methane hydrate-bearing marine sediments. Five calcifying marine bacteria were isolated using Christensen's urea agar from marine sediments collected from Gawadar coastal, Pakistan. Bacterial strains induced CaCO3 precipitation producing urease enzymes. Strains were identified as Pseudomonas putida, Bacillus altitudinis, Vibrio sp., Bacillus sp., and Vibrio plantisponsor. Energy-dispersive X-ray spectroscopy, scanning electron microscopy, and X-ray diffraction were applied for the identification and differentiation of calcite and vaterite precipitates. The growth of isolates and precipitation potential were observed optimum at 5% NaCl and pH 9.5-11. Bacillus altitudinis (ST4SD3) and Bacillus sp. (ST4SD1) produced more soluble Ca2+ (8532.53 mg/l and 7581.98 mg/l) as compare to other isolates at higher pH 10 and pH 11, favorable for CaCO3 precipitation. It is concluded that marine ureolytic bacteria possess significant potential for bio-cementation, which can stabilize methane hydrate-bearing sediments, improve soil properties, protect coastal regions from erosion, and crucial in the methane cycle, a greenhouse gas. We recommend further exploration of such bacteria's applications in marine construction and sediment stabilization to enhance the robustness and longevity of coastal infrastructures. Furthermore, such bacteria could also be beneficial in extracting gas from unconsolidated methane hydrates containing sediments
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