Simulation Investigation on the Structure and Its Influence on the Impinging Pressure of the Carbon Dioxide Jet.

An improved understanding of the mechanisms of SC-CO2 jet drilling technology is important for the application of this new technology. The flow field structure and dynamic fluctuation of SC-CO2 jets are the key factors affecting the jet erosion performance. To improve the erosion performance of the SC-CO2 jet, it is necessary to study the relationship between the different flow fields of the jet. In this study, a numerical simulation model for SC-CO2 jet drilling technology is established. Based on the modified real-gas model, the pressure distribution and flow field characteristics of the SC-CO2 jet were obtained by the simulation investigation, and the reliability of the model was verified. The results show that the flow field structure of a supercritical CO2 jet has typical compressible flow field characteristics. As the jet is fully expanded, its pressure fluctuation is slight and less affected by the distance between the nozzle and the wall. When the jet is in the state of under-expansion, the flow field structure characteristics have a significant impact on the pressure distribution and peak pressure. At the same time, when the distance is large, when nozzle pressure ratio = 5, the pressure ratio has a more significant impact on the flow field and the pressure peak and distribution. The pressure distribution of different flow fields should be fully considered in the application.

Oxidation-absorption process for simultaneous removal of NOx and SO2 over Fe/Al2O3@SiO2 using vaporized H2O2.

3% Fe/Al2O3 and 3% Fe/Al2O3@SiO2 were prepared to investigate the performance in simultaneous removal of NOx and SO2 using vaporized H2O2. Certain paraments were changed to explore the activity of catalysts, including temperature, H2O2 concentration, GHSV and coexistence gases component. A 24-h durability test was conducted on 3% Fe/Al2O3@SiO2. Moreover, a series of characterizations were employed to analyze the physical and chemical properties of catalysts, including XRD, BET, SEM, TEM, FTIR and XPS. Compared with 3% Fe/Al2O3, 3% Fe/Al2O3@SiO2 exhibited more excellent catalytic activity, which could achieve the peak removal efficiency of 100% for SO2 and 93.76% for NOx. Moreover, 3% Fe/Al2O3@SiO2 kept stable simultaneous removal efficiency in a 24-h test. The characterization results indicated that the BET area was greatly improved and the core-shell structure was synthesized with the formation of more micropores and mesopores by the coating of SiO2, which could improve the activity of catalyst at high temperature and high SO2 concentration. Besides, the mechanism of SO2 molecules on simultaneous removal was investigated. On one hand, a part of H2O2 was consumed by SO2 molecules without catalyst, which resulted in the drop of NOx removal by the decrease of oxidants. The main products were sulfites and bisulfites, which were broken down into SO2 over the catalyst. On the other hand, the presence of SO2 was beneficial for NOx removal by increasing oxygen vacancies on the catalyst surface and facilitating the absorption of NO2 by NaOH solution.

Systematic evaluation of COVID-19 related Internet health rumors during the breaking out period of COVID-19 in China.

Background: To adapt the scientific evaluation tool for the confusion evaluation of health rumors and to test this tool to the confusion evaluation of coronavirus disease 2019 (COVID-19)-related health rumors on Chinese online platforms during the outbreak period of COVID-19in China. Methods: The design of our study was systematic evaluation of COVID-19-related health rumors. Retrieved from 7 rumor-repellent platforms, rumors about COVID-19 were collected during the publication from December 1, 2019, to February 6, 2020, and their origins were traced. Researchers evaluated rumors using the confusion evaluation tool in 6 dimensions(creators, evidence selection, evidence evaluation, evidence application, backing and publication platform, conflict of interest). Items were scored using a seven-point Likert scale. The scores were converted into percentages, and the median of rumors from different sources was compared with rank-sum test. Results: Our research included 127 rumors. Scores were converted to percentages, median and interquartile range are used to describe the data. The median score: creators 25.00%(interquartile range, IQR, 16.67-37.50%), evidence selection 27.78% (IQR, 13.89-44.44%),evidence evaluation 33.33% (IQR, 25.00-45.83%), evidence application 36.11% (IQR, 22.22-47.22%), backing and publication platform 8.33% (IQR, 4.17-20.83%), conflict of interest75.00% (IQR, 50.00-83.33%). Almost 40% rumors came from WeChat and the rumors with the lowest scores were concentrated on the WeChat platform. The rumors about prevention methods have relatively lower scores. Conclusion: Most rumors included were not highly confusing for evaluators of this project.WeChat is the "worst-hit area" of COVID-19 related health rumors. More than half rumors focus on the description of prevention methods, which reflects the panic, anxiety and blind conformity of the public under public health emergencies.

Oxidation of NO x Using Hydrogen Peroxide Vapor over Mo/TiO2.

xMo/TiO2 catalysts (x = 1, 2, 3, and 4%) were prepared using the coprecipitation method in the present study. The coprecipitation method was used in the thermal catalytic decomposition of H2O2 steam to treat NO x at a low temperature range (80-160 °C). Several characterization techniques have been employed, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller measurements, transmission electron microscopy (TEM), scanning electron microscopy and energy-dispersive X-ray spectrometry (SEM-EDXS), and Fourier transform infrared spectroscopy. The activity tests showed that the incorporation of molybdenum into TiO2 led to a significant increase in the catalytic oxidation of NO, and under the condition of H2O2/NO = 6:1 (molar ratio), the NO x removal rate of 2% Mo/TiO2 is the highest, reaching 92.56%. XRD, TEM, and SEM-EDXS analyses showed that Mo was well dispersed on the surface of an anatase-phase TiO2. XPS analysis indicated that Mo mixed with slag mainly existed in the form of Mo6+. Moreover, in comparison with the mostly reported SCO catalysts, used for the elimination of NO, the prepared Mo/TiO2 catalyst showed excellent stability and sulfur resistance.

Experiment and simulation study of the effect of ethanol and compound additives on the urea-based selective non-catalytic reduction process under moderate temperature conditions.

An experiment and simulation study of the effect of using liquid additives on the selective non-catalytic reduction (SNCR) process is presented, providing a novel way for plants reducing NOX emissions. An experimental study is conducted in an entrained flow reactor, and CHEMKIN is applied for simulation study. Ethanol additive can effectively shift the temperature window of the NOXOUT process to a lower range and the NOXOUT efficiency ranges from 29 to 56% at 700-800°C. Furthermore, ethanol additive has a significant inhibitory effect on ammonia slip. Na2SO4 and C2H5OH can be combined into a compound additive, which has a synergistic effect on NO reduction. The addition of methanol can greatly promote denitrification efficiency from 650°C to 725°C, indicating the potential of compound additives in NO reduction. The HNCO + OH = H2O + NCO pathway is also proven to be enhanced for ethanol decomposition, thereby providing OH•, which is active in NO reduction. Finally, the reaction routes for ethanol on the urea-based SNCR process at the proper temperature are proposed.