Fluidization stability and periodic fluctuations in gas–solid separation fluidized bed using Geldart A dense medium

Gas–solid separation fluidized bed is a typical method for coal separation without water utilization.Geldart A particles is also considered as the ideal dense medium to strengthen separation efficiency.Fluidization stability reflects the bed pressure fluctuations and the distribution of bubble and emulsion phases,affecting the separation performance.And the main frequency of pressure fluctuations can directly reflect the degree of pressure fluctuations.Therefore,the detailed fluidization stability is analyzed combined the method of standard deviation of pressure fluctuations,power spectral density,etc.,for Geldart A particles.The results showed that maintaining an appropriate gas velocity resulted in an average bed pressure of around 2000 Pa.The main frequency is mainly concentrated around 1–1.5 Hz.Finally,a prediction model of the main frequency of pressure fluctuations is established,and the error can be controlled within±0.15.The investigation further proved the stable fluidization of Geldart A particles and provides a method for predicting the main frequency of pressure fluctuations in the gas–solid separation fluidized bed.

Forming solid electrolyte interphase in situ in an ionic conducting Li_(1.5)Al_(0.5)Ge_(1.5)(PO_4)_3-polypropylene(PP) based separator for Li-ion batteries

A new concept of forming solid electrolyte interphases（SEI） in situ in an ionic conducting Li（1.5）Al（0.5）Ge（1.5）（PO4）3-polypropylene（LAGP-PP） based separator during charging and discharging is proposed and demonstrated. This unique structure shows a high ionic conductivity, low interface resistance with electrode, and can suppress the growth of lithium dendrite. The features of forming the SEI in situ are investigated by scanning electron microscopy（SEM） and x-ray photoelectron spectroscopy（XPS）. The results confirm that SEI films mainly consist of lithium fluoride and carbonates with various alkyl contents. The cell assembled by using the LAGP-coated separator demonstrates a good cycling performance even at high charging rates, and the lithium dendrites were not observed on the lithium metal electrode. Therefore, the SEI-LAGP-PP separator can be used as a promising flexible solid electrolyte for solid state lithium batteries.

Recent progresses in dry gas polymeric filters

Filtration and membrane separation are popular methods in gas separation since they are cost and energy efficient. Despite to air filters, there are comparatively few studies on dry gas filters, particularly at industrial scale. In fact, major unsolved challenges such as high efficiency, low pressure drop, long-term stability, high-thermal and chemical stability and advanced physiochemical properties, are still remained. The aim of this review is to scrutinize the advanced scientific and technological practices (such as selection of appropriate polymeric materials and additives, nanotechnology, modification techniques and preparation methods) towards design and fabrication of an efficient filter media for solid particles removal from the natural gas flow. Recent progresses in solid particle separation mechanisms, modeling and simulation techniques and the effect of membrane fabrication methods on its performance, strategies for modification of filter media, current challenges and future perspective are discussed.

新一代中型固液捆绑火箭技术特点

China’s first solid-liquid bundled launch vehicle,the Long March 6 A(LM-6 A)successfully adopted a number of key new technologies,launching the Pujiang 2 and Tiankun 2 satellites precisely into their predetermined orbits,thus demonstrating that China has mastered solid-liquid bundled launch vehicle technology and has a new member in the new generation launch vehicle family.For the first time in China,a booster adopted a 2 m-diameter solid motor and a 270 V,20 k W high-voltage and high-power electric servo system was used to control the swing of the solid motor nozzles.A health diagnosis system for the core first stage engine and unattended automation technology were also adopted for the first time.

Numerical simulation of a dense solid particle flow inside a cyclone separator using the hybrid Euler-Lagrange approach

This paper presents a numerical simulation of the flow inside a cyclone separator at high particle loads. The gas and gas–particle flows were analyzed using a commercial computational fluid dynamics code. The turbulence effects inside the separator were modeled using the Reynolds stress model. The two phase gas–solid particles flow was modeled using a hybrid Euler–Lagrange approach, which accounts for the four-way coupling between phases. The simulations were performed for three inlet velocities of the gaseous phase and several cyclone mass particle loadings. Moreover, the influences of several submodel parameters on the calculated results were investigated. The obtained results were compared against experimental data collected at the in-house experimental rig. The cyclone pressure drop evaluated numerically underpredicts the measured values. The possible reason of this discrepancies was disused.

Filtering cylindrical–conical hydrocyclone

Hydrocyclones have versatile applications in various industrial processes.They functionn on the principle of centrifugal separation to remove a dispersed phase(particles or drops)from a continuous phase(fluid).In unconventional filtering hydrocyclones,the separation efficiency and energy costs have been improved by combining filtration with centrifugal separation.This work investigated experimentally the effect of incorporating a cylinder and a porous cone in a conventional hydrocyclone.It also evaluated the effects of the main geometric dimensions of the separator on the hydrocyclone performance.A differential-evolution algorithm was applied to optimize the hydrocyclone performance,which was represented as the maximum total efficiency and minimum Euler number.The experimental results validated the optimization results and showed that hydrocyclones with optimized geometries exhibited higher total efficiencies(89.59%)and lower Euler numbers(582)than hydrocyclones with other experimental configurations.

Advances in Nonwoven‑Based Separators for Lithium‑Ion Batteries

Lithium-ion batteries(LIBs)are energy-storage devices with a high-energy density in which the separator provides a physical barrier between the cathode and anode,to prevent electrical short circuits.To meet the demands of high-performance batteries,the separator must have excellent electrolyte wettability,thermotolerance,mechanical strength,highly porous structures,and ionic conductivity.Numerous nonwoven-based separators have been used in LIBs due to their high porosity and large surface-to-volume ratios.However,the fabrication of multi-functional fibers,the construction of nonwoven separators,and their integration into energy-storage devices present grand challenges in fundamental theory and practical implementation.Herein,we systematically review the up-to-date concerning the design and preparation of nonwoven-based separators for LIBs.Recent progress in monolayer,composite,and solid electrolyte nonwoven-based separators and their fabrication strategies is discussed.Future challenges and directions toward advancements in separator technologies are also discussed to obtain separators with remarkable performance for high-energy density batteries.