Intensification Mechanism Research Articles

Selective lithium recovery from waste lithium-ion batteries by H2SO4 roasting focused on process intensification and conversion mechanism

The purpose of this study is to prove the feasibility, efficiency and selectivity of lithium recovery from waste lithium-ion batteries (LIB) via sulfuric acid roasting-water leaching by thermodynamic analysis and experimental verification. The feasibility was proved by Gibbs free energy calculations and experiments. Then, the effects of H2SO4 concentration, roasting temperature and roasting time were assessed on the leaching rate of valuable metals. The results indicate that the leaching efficiency of lithium increases firstly and then decreases with the increase of H2SO4 concentration, roasting temperature and roasting time, more than 91 % lithium are leached under optimized experimental conditions: 50 wt% H2SO4, roasting temperature of 650°C, and roasting time of 2 h. Meanwhile, the selectivity of lithium is up to 88 % which means overwhelming majority lithium have been separated completely. In addition, the factors which cause sintering phenomenon such as high temperature and longtime roasting will change the microstructure of roasted product extremely, which is inconducive to the subsequent water leaching. The investigations of the phase conversion mechanism by thermodynamic simulation and instrumental characterization indicated that the leaching behaviors of valuable metals might be influenced by the different reaction pathways of the compounds while changing roasting conditions. The recovery process can be divided into two stages: the partial structure of LiNixCoyMnzO2 was destroyed to form metal sulfates at ambient temperature and the solid phase reaction between unreacted LiNixCoyMnzO2 which contained Li+ in the unstable layered structure with transition metal sulfates at high temperature. The fully reduced low-valence states are mainly (NiO)0.75(MnO)0.25 and CoO, and basically all Li within the crystalline LiNixCoyMnzO2 was de-intercalated and transformed to soluble Li2SO4. These results further confirm the advantages of H2SO4 roasting on selective Li recovery, and provide a better understanding of conversion mechanism by combining theory and experiments.

Intensification Mechanism of Acidic Imidazole-Based Ionic Liquids on the Synthesis of 1,3,5-Trioxane Catalyzed by Sulfuric Acid

Intensification Mechanism of Acidic Imidazole-Based Ionic Liquids on the Synthesis of 1,3,5-Trioxane Catalyzed by Sulfuric Acid

Solid hydrogen storage with palladium-graphene composites: Synthesis, characterization, and mechanistic insights

Efficient and safe hydrogen storage is a pivotal challenge for the advancement of hydrogen energy technologies. To address this, the engineering of high-performance solid-state hydrogen storage materials through the loading of transition metals (TM) on carbon-based solids has gained considerable interest. However, the mechanics for TM such as Palladium that bolster hydrogen storage have not well addressed yet. This work presents hydrogen absorptions with metal Pd nanoparticles loaded on reduced graphene oxide (Pd-rGO), including material preparation, structural characterization, hydrogen storage performance, and quantum chemical mechanistic insights. A simple material synthesis strategy has been explored and Pd-rGO composites are successfully prepared with graphite powder as raw materials by an easy reduction-oxidation process. Then, Pd-rGO composites are characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, Raman, transmission electron microscopy, and nitrogen adsorption-desorption isotherms methods to clarify the detailed structural characteristics of Pd-rGO with different loading amounts. It is found that Pd nanoparticles with an average particle size of 10 nm are uniformly dispersed on the surface of rGO. The materials have high defect severity and increased specific surface areas with Pd loading. The hydrogen adsorption capacity of Pd-rGO can be increased by 64 % compared with that without Pd loading due to the hydrogen spillover effect. In addition, the intensification mechanism of hydrogen storage of Pd-rGO composites is further understood by using density functional theory calculations and surface interaction analysis.

Study on the bubble breakup and internal flow characteristics in the pulsed jet ejector

To intensify the bubble breakup in the ejector, a novel pulsed jet ejector is designed in this work. The pulsed jet is introduced into the ejector by one fluidic oscillator. A high-speed camera experiment is conducted to capture the progress of bubble breakup. The intensification mechanism of pulsed jet on bubble breakup in ejector is investigated by numerical simulation. The experimental results indicate that the introduction of the pulsed jet effectively induces the occurrences of pressure fluctuations and vortex collision, prompting the deformation of bubbles to produce microbubbles. It is also found that the bubble diameter and number of microbubbles mainly depend on the process of bubble breakup in the divergent section, and the bubble diameter distribution is significantly influenced by the variation of Reynolds number. The variations of the vortex structure are induced by the pulsed jet, which is a key factor influencing mixing efficiency and bubble breakup effects. In addition, pulsed jet ejectors have superior mixing performance compared to conventional ejectors.

CFD simulation and experimental study of CO2 absorption in a rotating packed bed

The rotating packed bed (RPB), a process intensification equipment, has been widely studied and applied to chemical engineering processes such as gas absorption, nanomaterial preparation, and polymer devolatilization. In this study, we presented a typical RPB model to study the intensification mechanism of high gravity on gas-liquid mass transfer. Based on this, three-dimensional computational fluid dynamics (CFD) simulations and experiments of CO2 physical absorption were conducted to investigate the gas-liquid mass transfer characteristics in the RPB. The predicted and experimental values of CO2 saturation rates of the liquid phase showed good agreement, and the errors were within ± 15 % under various operating conditions. Moreover, detailed flow field and mass transfer information that are difficult to measure experimentally, such as the distribution of CO2 mass fraction in the liquid, liquid holdup, turbulent kinetic energy dissipation rate, and gas-liquid interfacial area, were analyzed by CFD simulation results. These results provide a solid foundation for the further development and application of RPB.

Hybrid conditioning of ionic liquid coupling with H2SO4 to improve the dewatering performance of municipal sludge.

Municipal sludge generated from wastewater treatment plants can cause a serious environmental and economic burden. A novel hybrid conditioning strategy was developed to enhance the dewatering performance of sludge, employing 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([C4mim][CF3SO3]) treatment combined with H2SO4 acidification. Following conditioning, the capillary suction time ( ), the specific resistance of filtration (SRF), and moisture content of the treated sludge were decreased to 1.99 ± 0.24 (s·L/g TSS), 1.33 ± 0.05 (1012m/kg), and 72.01 ± 0.94%, respectively. The results were superior to those achieved with sludge treated solely by H2SO4 acidification or [C4mim][CF3SO3] alone. The biomacromolecules within the sludge flocs were dissolved by [C4mim][CF3SO3], while simultaneously, the microorganisms were inactivated. Consequently, the colloidal-like structures of the sludge flocs were destroyed. Additionally, the ionizable functional groups of the biomacromolecules were instantly protonated by the introduced H+ ions, and their negative charges were neutralized during the H2SO4 acidification process. The presence of H+ ions promoted the weakening of electrostatic repulsion between the sludge flocs. As a result, an enhancement of sludge dewaterability was obtained after treatment with [C4mim][CF3SO3] and H2SO4 acidification. The finding of the intensification mechanism of sludge dewaterability brought by hybrid treatment of acidification and [C4mim][CF3SO3] provides novel insights into the field of sludge disposal.

Means of expressing the category of intensity and their role in creating the image of the city in L. N. Andreev’s story "The Curse of the Beast"

The need for a holistic linguistic analysis of such a little-studied literary phenomenon as Russian expressionism determines the relevance of the research. Analysis can be performed through systematising the ways of conveying expressivity as an aesthetic norm of this movement. These means include the intensity category representants distinguished by the pragmatically fixed function of impact enhancers. In addition, studying the versatile literary creativity of L. N. Andreev, "the first expressionist in Russian prose", we can comprehend the unique features of the writer ’s individual style from new perspectives while analysing his intensification solutions. The article aims to study the expressive potential of different-level intensity-expressing means considering the expressionistic tendencies in creating the key image of the city in "one of the most ʻhighly publicised’ works" by L. N. Andreev, i. e. the story "The Curse of the Beast". The linguistic material was selected using the continuous sampling method. Contextual analysis identified the specific features of actualising the meanings of certain intensity representants. Definitional analysis made it possible to identify the presence/absence of an intensifying component in the semantics of a particular word. Linguostylistic analysis was used to deter mine the specifics of the intensification mechanism while studying the author’s individual style. The article concludes that the use of means of expressing intensity, which on the pages of the story become a way of categorising the expressionist world perception, is a specific technique for influencing the reader ’s perception when describing the city. At the level of linguistic organisation of the text, the study has demonstrated how urban space is presented in deformed images – visual, temporal, auditory – with the help of the means expressing such semantics. They are grouped around the dominant textual concepts of "quantity", "size", "speed", "temperature", "extent", "sound". Moreover, when creating an urban text, L. N. Andreev shifts the focus from the usual description of the setting to "visible emotions" (which is in the spirit of the expressionist movement) with the help of abundant multielement linguistic units.

Enhancement of solid-liquid mixing state quality in a mechanical stirred reactor with serial-chaotic rotation generated by basic speed method

In this work, a novel controllable chaotic stirring strategy that basic speed with chaotic mappings is proposed to enhance the solid-liquid mixing state quality. Specially, the modern statistical image analysis technique is introduced to explore the intensification mechanism of the mixing process. Results show that the best experimental conditions are obtained by studying the influence of factors such as the type of chaotic mapping, the speed change time, and the basic speed on the mixing state quality. Moreover, the case in which the basic speed is set to 150 r/min generated by the cascaded Logistic-Cubic chaotic mapping is the best while the speed change time is set to 5 s and the fluctuation threshold is 30. The mixing time of this case is 50 s and the shortest, energy consumption is 1.64 × 104 W/m3 and appropriate, the solid particle suspension quality is 83 and the best.

Observation and simulation study on the rapid intensification mechanism of Typhoon “Mekkhala” (2006)

Based on Doppler Weather radar observations and numerical simulations applying the Weather Research and Forecasting (WRF) system, this study focused on the rapid intensification (RI) of Typhoon “Mekkhala” (2006) in the inshore area in 2020. The simulated track of the typhoon relatively matched with the observation, with a slight eastward bias compared to the observed track. During the phase of RI, there was a slight weakening of vertical wind shear between 200–500 hPa. The temporary decrease in vertical wind shear became a favorable factor for the intensification of the typhoon. In general, vertical wind shear of the lower atmosphere is the key to supporting the RI of Typhoon Mekkhala. In the middle troposphere, the southward component of the vertical wind shear suddenly increases, indicates that the inflow of southern wind to the core of the typhoon had strengthened. Thus, the strengthening of the moisture transport by enhanced southern wind, contributed to the intensification of the typhoon. During the intensification of the typhoon, the low-level vorticity was significantly enhanced, and the high vorticity values expanded from the lower to higher troposphere. The vertical distribution of vorticity transformed from symmetry to asymmetry. The development of secondary circulation on both sides of the typhoon is a dynamic factor for intensification.

Combustion Intensification Mechanism in a Vortex-Tube Reactive Flow

The combustion intensification mechanism was revealed in a stratified vortex-tube combustor. The results show that a triple-flame structure is formed in this combustor and the peak heat release is located exactly at the triple-point position. The peak heat release rates in the five selected representative cases studied in this paper are all over . The stability limit is wide, and the lean stability limit is always lower than 0.2. The decreased mixing length and decreased velocity difference between the fuel and oxidant streams delay the mixing process and then bring about a stratified distribution of species. This is crucial for the generation of a triple-flame structure and the corresponding high species concentration in the vicinity of the reaction zone under lean conditions. The Damköhler numbers on the lines across the triple points were calculated with values above 1.0 in each of the cases, indicating that the species’ transport time is longer than the chemical reaction time. Therefore, the transport flux of species determines the final combustion strength. The synergistic coupling of the flowfield and species field gives rise to a large transport flux of the key species in the vicinity of the reaction zone. The results show that the corresponding fuel transport flux is large, with values all over . This is the principal reason for the high combustion intensity in this combustor. The different transport fluxes of the critical species are responsible for the different chemical reaction strengths on the triple point in each of the different cases.

Intensification Rates of Tropical Cyclone–Like Vortices in a Model with Downtilt Diabatic Forcing and Oceanic Surface Drag

Abstract Tropical cyclones are commonly observed to have appreciable vertical misalignments prior to becoming full-strength hurricanes. The vertical misalignment (tilt) of a tropical cyclone is generally coupled to a pronounced asymmetry of inner-core convection, with the strongest convection tending to concentrate downtilt of the surface vortex center. Neither the mechanisms by which tilted tropical cyclones intensify nor the time scales over which such mechanisms operate are fully understood. The present study offers some insight into the asymmetric intensification process by examining the responses of tilted tropical cyclone–like vortices to downtilt diabatic forcing (heating) in a 3D nonhydrostatic numerical model. The magnitude of the heating is adjusted so as to vary the strength of the downtilt convection that it generates. A fairly consistent picture of intensification is found in various simulation groups that differ in their initial vortex configurations, environmental shear flows, and specific positionings of downtilt heating. The intensification mechanism generally depends on whether the low-level convergence σb produced in the vicinity of the downtilt heat source exceeds a critical value dependent on the local velocity of the low-level nondivergent background flow in a reference frame that drifts with the heat source. Supercritical σb causes fast spinup initiated by downtilt core replacement. Subcritical σb causes a slower intensification process. As measured herein, the supercritical intensification rate is approximately proportional to σb. The subcritical intensification rate has a more subtle scaling, and expectedly becomes negative when σb drops below a threshold for frictional spindown to dominate. The relevance of the foregoing results to real-world tropical cyclones is discussed.

Numerical investigation on intensified mixing performance with modified dual impeller

Process intensification is important for achieving efficient fluid mixing. In this study, the process intensification mechanism of mixing was investigated based on the evolution of sub-steady flow pattern. The results showed that the modified dual impeller (Mod-DI) could eliminate the isolation zone and symmetry of the flow pattern, which always appears in the traditional dual impeller (Trad-DI) system. Furthermore, the mixing time (tm) and dynamic equilibrium time (tde) of the Mod-DI system were significantly shorter than those of the Trad-DI system, which could be attributed to the enhancement of fluid flow fluctuations caused by the loss of stability of sub-steady flow field. In the presence of baffles, tm and tde could be further reduced. The shortening of time was at the expense of increasing power consumption. Overall, the intensification mechanism of the Mod-DI is mainly since the formation of sub-steady flow field, which enhances the instability of the fluid flow.

Surfactant-enhanced extraction of valuable metals from limonitic laterite: Porous kinetics and mechanism analysis

The efficient extraction of valuable metals from low-grade mineral resources is an important initiative to implement the concept of carbon neutrality and achieve energy conservation and emission reduction. Atmospheric leaching of laterite ores is widely noted for its low cost. However, low extraction and difficulties in slurry filtration have severely restricted its development. Inspired by our previous studies on the porous kinetics, two options for improving the nitric acid atmospheric leaching (NAAL) of limonitic laterite are proposed. 84.85 % of Ni extraction is achieved under the optimal process conditions (Temperature: 98 °C, Time: 3.5 h, Liquid/Solid: 4.7 mL/g, and the initial nitric acid concentration: 487 g/L). After enhanced treatment, the Ni extraction is increased by 3.16 % (bleed air), 4.55 % (SDS: sodium dodecyl sulphate), and 5.67 % (DTAB: dodecyl trimethyl ammonium bromide), respectively. In addition, DTAB not only promotes the leaching of laterite ores but also improves the filtration performance of the slurry. The filtration rate was more than three times higher than in the absence of DTAB. The presence of silicic acid is responsible for the difficult filtration of the slurry and the low extraction of valuable metals. Analysis of the intensification mechanism shows that the bleed air treatment mainly eliminates the obstruction of leaching by air in the pores, thus increasing the effective reaction area. The reinforcing effect of surfactants is mainly due to the improvement of diffusion efficiency, the reduction of adsorption, and the increase in permeability. This paper provided a feasible option for the enhanced leaching of limonitic laterite, and the reinforcement mechanism was explained clearly. It not only responds to the call for energy conservation and emission reduction by achieving efficient extraction of valuable metals from low grade laterite resources, but also avoids the treatment of laterite ores by means of high temperature and pressure.

A novel insight on the intensification mechanism of sludge dewaterability by ionic liquids

The huge output of sewage sludge has caused a remarkable environmental burden. Sludge dewatering is considered as an important way to reduce the sludge volume. Five imidazole-based ionic liquids were used to improve the dewaterability of sewage sludge. 1-ethyl-3-methylimidazolium dihydrogen phosphate ([Emim][H2PO4]) was screened out as a potential conditioner of sludge due to its excellent dewatering performance and reusability. The solid content of sludge filter cake after treatment with [Emim][H2PO4] was about 10% higher than that of sludge treated by cationic polyacrylamides (CPAM). The intensification mechanism of ionic liquids to the improvement of sludge dewatering performance was studied. The presence of acidic ionic liquids [Emim][H2PO4] resulted the increase of zeta potential from −14.57 ± 0.81 mV to −5.60 ± 0.30 mV and led to the protonation of biopolymers. Acidic ionic liquids [Emim][H2PO4] inactivated the microorganism and led to a porous and unconsolidated structure of the solid sludge particles. All these effects were conducive to destroy the microstructure of sludge and release water. However, [Emim]Cl, [Bmim][OTf] and [Hmim][OTf] showed little effect on the protonation of ionizable functional groups at near-neutral environment. The dissolution of biopolymer decreased the zeta potential and strengthened the electrostatic repulsion. So, they showed weaker intensification effects than CPAM.

Heat Transfer Intensification Mechanism of a Baffled Fluidized Bed Heat Exchanger

Gas–solid fluidized bed heat exchangers are commonly applied to remove heat in highly exothermic processes. The heat transfer performance is related to hydrodynamics. Baffles, such as ring-type baffles, louver baffles, and packings, are widely applied to improve the hydrodynamics in a fluidized bed. In this study, a baffled fluidized bed heat exchanger was proposed to enhance the bed-to-surface heat transfer coefficient. The baffles are specially designed to intensify the contact characteristics between heat transfer tubes and fluidized bed medium. The hydrodynamics and heat transfer characteristics were compared between the conventional and the newly designed baffled heat exchanger to explore the intensification mechanism in dilute and dense fluidization regions. Proper arrangement of the baffles in the fluidized bed heat exchanger increases the time fraction of the particle packet as well as the solid holdup, which enhances the heat transfer coefficient in dilute region. For the dense region, the contact time between the packet and heat transfer surface is decreased in the baffled fluidized bed heat exchanger due to the reduced bubble size, increased bubble frequency, and enhanced radial movement of bubbles and particles. Therefore, the bed-to-surface heat transfer in the dense region is significantly intensified.

Application of the rotating-convection paradigm for tropical cyclones to interpreting medicanes: An example

The rotating-convection paradigm for tropical cyclone behaviour is shown to provide an attractive and consistent framework for interpreting the dynamics of formation and intensification of at least some medicanes. The ideas are illustrated by a case study of the medicane that formed over the eastern Mediterranean in mid-December 2020. This case study is based on analyses of data from the European Centre for Medium Range Weather Forecasts (ECMWF), imagery from the European geostationary meteorological satellite, Meteosat Second Generation, and output from a convection permitting numerical simulation of the event using the United Kingdom (UK) Met Office regional model with the RAL2 physics configuration. Limitations of the currently widely accepted interpretation of medicanes in terms of the so-called Wind-Induced Surface Heat Exchange (WISHE) intensification mechanism are discussed.

Short-wave run-ups of the 1611 Keicho tsunami along the Sanriku Coast

A tsunami generated by an earthquake that occurred off the east coast of Japan in 1611 was predominantly concentrated along the Sanriku Coast. The 1611 event produced its greatest observed tsunami height at Koyadori, 28.8 m, higher than that produced by other representative tsunamis at the same location such as the 2011 Tohoku and 1896 Meiji Sanriku tsunamis. The characteristics of the source that resulted in the remarkable tsunami height at Koyadori have been widely debated. In this study, we simulated the local intensification mechanism of the 1611 tsunami and derived some key characteristics of the earthquake that produced the intensification at Koyadori based on these results. First, we investigated the topographical inundation characteristics in representative areas on the Sanriku Coast, including Koyadori, by numerical means. By comparing the numerical results with the observed heights for the 1611 tsunami, we found that a simulated tsunami that was dominated by short-wave components yielded a promising reproduction of the observed heights. The development of a local resonance seemed a more likely cause for the observed local intensification at Koyadori than a single-pulse wave. These results suggested that the 1611 earthquake produced a tsunami dominated by short-wave components. Furthermore, the source must have been located far off the Tohoku coast near the Japan Trench axis to have had substantial short-wave components along the Sanriku Coast. Based on these findings, we constructed a source scenario for local intensification by investigating the characteristics of Green’s functions from single-point sources. The scenario involves two separate earthquake sources in shallow crustal areas at the plate interface of the subduction zone, resulting in a moment magnitude of 8.5. The tsunami produced by this source model, which reflected the characteristics of a tsunami earthquake, effectively reproduced the local intensification observed on the Sanriku Coast.

Continuous synthesis of dolutegravir sodium crystals using liquid-gas heterogeneous microreactor

In this work, a liquid-gas heterogeneous microreactor was developed for investigating continuous crystallization of dolutegravir sodium (DTG), as well as revealing reaction kinetics and mixing mechanism with 3-min data acquisition. The reaction kinetics models were established by visually recording the concentration variation of reactants over time in the microchannel via adding pH-sensitive fluorescent dye. The mixing intensification mechanism of liquid-gas flow was quantified through the fluorescent signal to indicate mixing process, demonstrating an outstanding mixing performance with a mixing time less than 0.1 s. Compared with batch crystallization, continuous synthesis of dolutegravir sodium using liquid-gas heterogenous microreactor optimizes crystal distribution size, and successfully modifies the crystal morphology in needle-like habit instead of rod-like habit. The microreactor continuous crystallization can run for 5 h without crystal blockage and achieve D90 of DTG less than 30 µm. This work provides a feasible approach for continuously synthesizing dolutegravir sodium, and can optimize the existing pharmaceutical crystallization.

Chaotic Mixing Intensification and Flow Field Evolution Mechanism in a Stirred Reactor Using a Dual-Shaft Eccentric Impeller

Chaotic Mixing Intensification and Flow Field Evolution Mechanism in a Stirred Reactor Using a Dual-Shaft Eccentric Impeller

Intensification-driven local search for the traveling repairman problem with profits

The Traveling Repairman Problem with Profits is to select a subset of nodes (customers) in a weighted graph to maximize the collected time-dependent revenues. We introduce an intensification-driven local search algorithm for solving this challenging problem. The key feature of the algorithm is an intensification mechanism that intensively investigates bounded areas around each very-high-quality local optimum encountered. As for its underlying local optimization, the algorithm employs an extended variable neighborhood search procedure which adopts for the first time a K-exchange sampling based neighborhood and a concise perturbation procedure to obtain high-quality solutions. Experimental results on 140 benchmark instances show a high performance of the algorithm by reporting 36 improved best-known results (new lower bounds) and equal best-known results for 95 instances. Additional experiments are conducted to investigate the usefulness of the key components of the algorithm.