13 research outputs found

    Nitrogen and sulfur conversion during pressurized pyrolysis under CO2 atmosphere in fluidized bed

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    Pressurized oxy-fuel combustion (POFC) is a promising technology for CO2 capture from coal-fired power plants, offering both high efficiency and a low penalty. However, the high partial pressure of CO2 in a POFC furnace has important impacts on fuel-N and fuel-S conversion during the coal pyrolysis process, and understanding this will help to achieve further control of SOx/NOx. In this study, coal pyrolysis experiments were conducted in a pressurized fluidized bed with the pressure range of 0.1–0.7 MPa under N2 and CO2 atmosphere. The gaseous products were monitored by a Fourier transform infrared spectroscopy analyzer (FTIR) and the char residue was characterized by an X-ray photoelectron spectroscopy (XPS) analyzer in order to acquire the species information for S-containing and N-containing compounds. Results show that the enrichment of CO2 in the local atmosphere enhances the fuel-N conversion to HCN in the pyrolysis process, which serves as a favorable precursor to N2O. The generation of HCN and NH3 increase simultaneously with the increase of overall pressure. SO2 concentration in the gaseous product is relatively low, and as the pressure increases, the concentration decreases slightly due to CO reduction of SO2 to COS. Sulfur content in the char decreases as the pressure goes from 0.1 MPa to 0.7 MPa indicating higher CO2 pressure accelerates the decomposition of sulfur compounds in the coal, which is further confirmed by the XPS results

    Observation of simultaneously low CO, NOx and SO2 emission during oxy-coal combustion in a pressurized fluidized bed

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    Pressurized oxy-fuel combustion is a promising technology for CO2 capture with respect to its high combustion efficiency and the simultaneous reduction of gaseous pollutants. A 10 kWth bubbling fluidized bed reactor with continuous coal-feeding was designed, and effects of pressure, temperature and fuel types on pollutant emission were investigated in detail. Generally, the relatively low carbon content in the ash and CO concentration in the flue gas demonstrated that the combustion efficiency was improved by high pressure. The concentration of NO, N2O and SO2 showed decreasing trends with the increase of pressure. Moreover, the effect of pressure on the emission of NO and SO2 in the lower pressure (≤0.3 MPa) was more pronounced than that in the higher pressure. The concentrations of NO and SO2 correlated positively with temperature, while for N2O, it had a negative correlation. Compared with air combustion, NO and SO2 emission dropped sharply in 21%O2/79%CO2 atmosphere. However, N2O concentration during oxy-combustion was slightly higher than that in air combustion in the range of experimental pressure

    Flow characteristics in pressurized oxy-fuel fluidized bed under hot condition

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    Pressurized oxy-fuel fluidized bed (POFB) combustion is regarded as a promising technology for carbon capture from coal-fired power plants. High pressure and temperature conditions have important impacts on the flow characteristic of fluidized bed, and understanding them will help to optimize the design and operation of the POFB boiler. In this work, experiments were carried out in two pressurized fluidized bed (PFB) devices (a hot PFB and a “visual PFB”) both operated under high temperature (20-800 °C) and high pressure conditions (0.1-1.0 MPa). Four parameters including the minimum fluidization velocity (umf), the minimum bubbling velocity (umb), bubble diameter (Db) and bubble frequency (f) were examined in this study. Results showed that the umf decreases with rising pressure and temperature. Based on our results a formula was fitted for calculating the minimum fluidization velocity in PFB, with a relative error less than 15%. With the increase of fluidization number (w), the bubble size and tail vortex increased gradually, the bubbles tended to merge, and the shape of bubbles became more irregular. The Db decreases with the increase of temperature and pressure at the same w. The f increases with increased w, while it decreased with the increase of temperature and pressure

    UAV photogrammetry in intertidal mudflats: accuracy, efficiency, and potential for integration with satellite imagery

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    The rapid, up-to-date, cost-effective acquisition and tracking of intertidal topography are the fundamental basis for timely, high-priority protection and restoration of the intertidal zone. The low cost, ease of use, and flexible UAV-based photogrammetry have revolutionized the monitoring of intertidal zones. However, the capability of the RTK-assisted UAV photogrammetry without ground control points, the impact of flight configuration difference, the presence of surface water in low-lying intertidal areas on the photogrammetric accuracy, and the potential of UAV/satellite Synergy remain unknown. In this paper, we used an RTK-assisted UAV to assess the impact of the above-mentioned considerations quantitatively on photogrammetric results in the context of annual monitoring of the Chongming Dongtan Nature Reserve, China based on an optimal flight combination. The results suggested that (1) RTK-assisted UAVs can obtain high-accuracy topographic data with a vertical RMSE of 3.1 cm, without the need for ground control points. (2) The effect of flight altitude on topographic accuracy was most significant and also nonlinear. (3) The elevation obtained by UAV photogrammetry was overestimated by approximately 2.4 cm in the low-lying water-bearing regions. (4) The integration of UAV and satellite observations can increase the accuracy of satellite-based waterline methods by 51%. These quantitative results not only provide scientific insights and guidelines for the balance between accuracy and efficiency in utilizing UAV-based intertidal monitoring, but also demonstrate the great potential of combined UAV and satellite observations in identifying coastal erosion hotspots. This establishes high-priority protection mechanisms and promotes coastal restoration

    Effectiveness and cost-effectiveness of four different strategies for SARS-CoV-2 surveillance in the general population (CoV-Surv Study): study protocol for a two-factorial randomized controlled multi-arm trial with cluster sampling

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    Background: To achieve higher effectiveness in population-based SARS-CoV-2 surveillance and to reliably predict the course of an outbreak, screening, and monitoring of infected individuals without major symptoms (about 40% of the population) will be necessary. While current testing capacities are also used to identify such asymptomatic cases, this rather passive approach is not suitable in generating reliable population-based estimates of the prevalence of asymptomatic carriers to allow any dependable predictions on the course of the pandemic. Methods: This trial implements a two-factorial, randomized, controlled, multi-arm, prospective, interventional, single-blinded design with cluster sampling and four study arms, each representing a different SARS-CoV-2 testing and surveillance strategy based on individuals' self-collection of saliva samples which are then sent to and analyzed by a laboratory. The targeted sample size for the trial is 10,000 saliva samples equally allocated to the four study arms (2500 participants per arm). Strategies differ with respect to tested population groups (individuals vs. all household members) and testing approach (without vs. with pre-screening survey). The trial is complemented by an economic evaluation and qualitative assessment of user experiences. Primary outcomes include costs per completely screened person, costs per positive case, positive detection rate, and precision of positive detection rate. Discussion: Systems for active surveillance of the general population will gain more importance in the context of pandemics and related disease prevention efforts. The pandemic parameters derived from such active surveillance with routine population monitoring therefore not only enable a prospective assessment of the short-term course of a pandemic, but also a more targeted and thus more effective use of local and short-term countermeasures. Trial registration: ClinicalTrials.gov DRKS00023271. Registered November 30, 2020, with the German Clinical Trials Register (Deutsches Register Klinischer Studien

    Three-dimensional full-loop numerical simulation of coal and sludge co-combustion in a circulating fluidized bed

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    The Dense Discrete Phase Model (DDPM) method is used to simulate the co-combustion process of coal and sludge over the full-loop circulating fluidized bed in a three-dimensional (3D) Eulerian-Lagrangian framework. Both heterogeneous (fuel conversion through pyrolysis and char combustion) and homogeneous reactions (e.g. volatile combustion) are considered. Comparison of the predicted pressure profile, flue gas composition and bed temperature with measurements show good agreement and validate the DDPM methodology for accurate description of the gas–solid flow and combustion process over the full-loop circulating fluidized bed. The results of coal and sludge co-combustion are analysed qualitatively and quantitatively in terms of flow characteristics, gas composition, reaction rate profile, and particle combustion characteristics. Due to the lower density and higher volatile content of the sludge, as the coal-to-sludge feeding ratio decreases, the combustion reaction rate is gradually skewed upwards in the furnace, shifting up also the corresponding gas concentration profiles. For the given fuel sizes, the faster devolatilization rate of coal yields a shorter burnout time than that of the sludge particles. Our work provides an intuitive perspective to the fluidized bed community to boost comprehension on the coal and sludge co-combustion in a full-loop circulating fluidized bed

    UAV Photogrammetry in Intertidal Mudflats: Accuracy, Efficiency, and Potential for Integration with Satellite Imagery

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    The rapid, up-to-date, cost-effective acquisition and tracking of intertidal topography are the fundamental basis for timely, high-priority protection and restoration of the intertidal zone. The low cost, ease of use, and flexible UAV-based photogrammetry have revolutionized the monitoring of intertidal zones. However, the capability of the RTK-assisted UAV photogrammetry without ground control points, the impact of flight configuration difference, the presence of surface water in low-lying intertidal areas on the photogrammetric accuracy, and the potential of UAV/satellite Synergy remain unknown. In this paper, we used an RTK-assisted UAV to assess the impact of the above-mentioned considerations quantitatively on photogrammetric results in the context of annual monitoring of the Chongming Dongtan Nature Reserve, China based on an optimal flight combination. The results suggested that (1) RTK-assisted UAVs can obtain high-accuracy topographic data with a vertical RMSE of 3.1 cm, without the need for ground control points. (2) The effect of flight altitude on topographic accuracy was most significant and also nonlinear. (3) The elevation obtained by UAV photogrammetry was overestimated by approximately 2.4 cm in the low-lying water-bearing regions. (4) The integration of UAV and satellite observations can increase the accuracy of satellite-based waterline methods by 51%. These quantitative results not only provide scientific insights and guidelines for the balance between accuracy and efficiency in utilizing UAV-based intertidal monitoring, but also demonstrate the great potential of combined UAV and satellite observations in identifying coastal erosion hotspots. This establishes high-priority protection mechanisms and promotes coastal restoration

    Rapid Loss of Tidal Flats in the Yangtze River Delta since 1974

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    As the home to national nature reserves and a Ramsar wetland, the tidal flats of the Yangtze River Delta are of great significance for ecological security, at both the local and global scales. However, a comprehensive understanding of the spatiotemporal conditions of the tidal flats in the Yangtze River Delta remains lacking. Here, we propose using remote sensing to obtain a detailed spatiotemporal profile of the tidal flats, using all available Landsat images from 1974 to 2018 with the help of the Google Earth Engine cloud platform. In addition, reclamation data were manually extracted from time series Landsat images for the same period. We found that approximately 40.0% (34.9–43.1%) of the tidal flats in the study area have been lost since 1980, the year in which the tidal flat area was maximal. The change in the tidal flat areas was consistent with the change in the riverine sediment supply. We also found that the cumulative reclamation areas totaled 816.6 km2 and 431.9 km2 in the Yangtze estuary zone and along the Jiangsu coast, respectively, between 1974 and 2018. Because of reclamation, some areas (e.g., the Hengsha eastern shoal and Pudong bank), which used to be quite rich, have lost most of their tidal flats. Currently, almost 70% of the remaining tidal flats are located in the shrinking branch (North Branch) and the two National Nature Reserves (Chongming Dongtan and Jiuduansha) in the Yangtze estuary zone. Consequently, the large-scale loss of tidal flats observed was primarily associated with reduced sediment supply and land reclamation at the time scale of the study. Because increasing demand for land and rising sea levels are expected in the future, immediate steps should be taken to prevent the further deterioration of this valuable ecosystem

    YeastRGB: comparing the abundance and localization of yeast proteins across cells and libraries

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    The ability to measure the abundance and visualize the localization of proteins across the yeast proteome has stimulated hypotheses on gene function and fueled discoveries. While the classic C’ tagged GFP yeast library has been the only resource for over a decade, the recent development of the SWAT technology has led to the creation of multiple novel yeast libraries where new-generation fluorescent reporters are fused at the N’ and C’ of open reading frames. Efficient access to these data requires a user interface to visualize and compare protein abundance, localization and co-localization across cells, strains, and libraries. YeastRGB (www.yeastRGB.org) was designed to address such a need, through a user-friendly interface that maximizes informative content. It employs a compact display where cells are cropped and tiled together into a ‘cell-grid.’ This representation enables viewing dozens of cells for a particular strain within a display unit, and up to 30 display units can be arrayed on a standard high-definition screen. Additionally, the display unit allows users to control zoom-level and overlay of images acquired using different color channels. Thus, YeastRGB makes comparing abundance and localization efficient, across thousands of cells from different strains and libraries.</p
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