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Supercritical water fluidized bed reactor (SCWFBR) is a novel concept for the gasification of coal and biomass to produce hydrogen. In this work, to enhance the mixing in the axial direction, an inclined distributor is introduced to optimize the flow dynamics in SCWFBR with partitioned fluid supply. Through numerical simulations based on the two fluid model (TFM), the effects of the inclined distributor structure and operating parameters on the solid distribution and the residence time are evaluated with the optimal values determined. Numerical results show that, area ratio = 2:1, SCW velocity ratio = 3:1, flow ratio = 3.36:1 and inclination angle = 20 ° are the optimal design in this paper. A predictive correlation of the minimum fluidization velocity for the improved SCWFBR is also proposed based on the numerical data. The average error between the correlation and numerical simulation results is approximately 1.4% which strongly demonstrates its capability. Finally, based on the optimal design, the lab-scale reactor is further scaled up and the studies about two scale-up rules are carried out. Only the cold flow is simulated in this study without considering chemical reaction which would be involved in future work.

In the steam thermal cracking of naphtha, the hydrocarbon stream flows inside tubular reactors and is exposed to flames of a series of burners in the firebox. In this paper, a full three-dimensional computational fluid dynamics (CFD) model was developed to investigate the process variables in the firebox and reactor coil of an industrial naphtha furnace. This comprehensive CFD model consists of a standard k-e turbulence model accompanied by a molecular kinetic reaction for cracking, detailed combustion model, and radiative properties. In order to improve the steam cracking performance, the model is solved using a proposed iterative algorithm. With respect to temperature, product yield and specially propylene-to-ethylene ratio (P/E), the simulation results agreed well with industrial data obtained from a mega olefin plant of a petrochemical complex. The deviation of P/E results from industrial data was less than 2%. The obtained velocity, temperature, and concentration profiles were used to investigate the residence time, coking rate, coke concentration, and some other findings. The coke concentration at coil exit was 1.9×10-3 %(mass) and the residence time is calculated to be 0.29 s. The results can be used as a scientific guide for process engineers.

The low density of mass and energy are the main reason for the underutilization of great potential of Empty Fruit Bunch (EFB) as a raw material of alternative and renewable fuels. The using of bintaro fruit as co-firing and treatment of torrefaction – densification processes were believed to increase the density of mass and energy of the EFB biopellet. This study aims to determine the effect of residence time, compaction pressure, and addition of bintaro fruit to the characteristics of EFB biopellet according to ISO 17225-6 standards. Biopellet manufacture was carried out two processes sequence, namely the torrefaction process and the densification process. The torrefaction process was carried out at 275oC with residence time variations 30, 45, and 60 minutes. The densification process was carried out without binder with compaction pressure variations 30, 40, and 50 bar. The addition of bintaro fruit was intended as co-firing of EFB at a ratio 70:30. The best characteristics of biopellet were obtained under conditions of 60 minutes residence time and 50 bar compaction pressures with 3.00% of moisture content, 7.90% of ash content, 8.70% of volatile content, 80.40% of fixed carbon content, 4719.59 cal/gr of heating value, and 1.28 gr/cm3 of density. Characteristics of moisture content and volatile content decreased while ash content, fixed carbon content, and heating value increased with increasing residence time. Characteristics of density increased with increasing compaction pressure. Characteristics of proximate and heating value increased while density properties of biopellet decreased with the addition of bintaro fruit as co-firing.

Glycerol, as a main by-product of biodiesel synthesis, can be used in a large variety of applications including food, personal care, pharmaceutical and chemical industries However, due to the large production of biodiesel, the glycerol market was depressed. The conversion of glycerol into an energy carrier (syngas or hydrogen) could be a very interesting route to providing value as a renewable energy source. The reforming of glycerol leads to an almost complete conversion and very high carbon-to-gas efficiency with short residence time. In this work, the performances of packed bed reactor for hydrogen production from glycerol in supercritical conditions, by using a Ni-based catalyst supported on Al2O3 and SiO2, through CFD modelling in three-dimensions were studied. The parameters of kinetic model were determined by using an optimization method to fit the experimental data. The developed model was been validated based on experimental results published in literature for three different feed concentration of glycerol of 5, 10 and 20 wt% (R2 = 0.969). Varying the reaction temperature, between 500 and 800 °C, and residence time, between 1.5 and 10 s, the concentration of hydrogen increased with increasing the temperature and decreasing the residence time. At high temperature, the hydrogen can achieve a concentration of 65% and the present of methane is less than 5% and carbon monoxide maintain lower concentration. The simulation results show that high hydrogen yield can be obtained in short residence time with conversion of glycerol almost completed.

The bench scales continuous stirred tank reactor (CSTR) for the synthesis of zirconium basic sulfate (ZBS) is one of the prototypes of research and development for the manufacture of nuclear-grade zirconium products in Center for Accelerator Science and Technology (CAST). The use of bench scale CSTR is to reduce the impurities of U, Th, Fe, Ti from zirconium oxychloride (ZOC) at certain pH conditions through the ZBS precipitation process. The purpose of this study is to test the CSTR of bench scale for ZBS synthesis by studying the effect of stirring speed of 100, 150, 200, 250, 300 rpm and residence time of 60, 75, 90, 105, 120 min on the conversion of ZBS synthesis. The bench scales of CSTR for ZBS synthesis was carried out by reacting to a 0.2 M ZOC solution with (NH4)2SO4 0.08 M at a mole ratio of Zr/SO4- = 5/2 and the pH of ZBS formation about 1.8─2.0. The experimental results show that at a stirring speed of 250 rpm and a reactant residences time of 120 min gives a ZBS formation conversion of 0.5059. It can be concluded that the greater the stirring speed and space-time the greater the conversion of ZBS.

The flow behavior of polydisperse particles in rolling mode rotating drum is important in industry, but it is still not clear. In this work, the discrete element method (DEM) is used to explore the flow of particles in the three-dimensional drum. After the accuracy of simulation verified by the experimental data from literature, the particle bed is divided into active layer and passive layer. The flow behavior of polydisperse particles was revealed by studying the particle velocity, residence time, mixing and axial dispersion in different regions in the drum. By exploring the parameters such as rotation speed, filling level and the shape and position of the lifter, some ideas are provided for improving the performance of the rolling mode rotating drum. In addition, the difference of flow behavior between polydisperse particles and monodisperse particles is also given, which can provide some reference for the industrial application of complex particle system.

The design paper focuses on developing a circular quick pyrolysing reactor that normally converts the agricultural biomass into biochar. The uniqueness incorporated in the design criteria is easy to attain high heating potential in the combustion chamber. All the supporting components in the reactor enhance control on temperature that supports even distribution of heat transfer and withholding the volatile organic compound with reasonable residence time. The design specifications are adopted with proper kinetic studies and making of the real time model that can operate 100 kg of biomass in 1 h duration. The fluidized bed reactor models normally have the ability to transfer heat even in low voids and can circulate high solid content within their limits which normally combust the biomass within less vapor residence time. In addition to pyrolyser design the importance of processing the agricultural waste for pollution free environment has been highlighted in this research outcome.

Prediction of combustion characteristics of aluminum particle is of great significance for a variety of propulsion and power systems to achieve optimal energy release within a limited residence time. In this study, a diffusion-controlled combustion model for micro aluminum particle was developed and validated to predict the burning time and capture the evolution of particle size during combustion in environments with multiple oxidizers. Thereafter, the key factors influencing particle combustion were evaluated including particle size, ambient temperature, oxidizer concentration and characteristics of oxide cap. The burning time drops as the oxidizer concentration and the ambient temperature increase, and their influences on burning time become weakened gradually. The effect of oxidizer concentration presents more obvious than ambient temperature. As the number of oxide cap increases from 2 to 5, the burning time rises by 6.9%–27.4%. Then a non-linear empirical equation was proposed to describe the effective oxidizer, which is more accurate than the existing linear correlation, especially for H2O. Finally, a formula capable of predicting the burning time was proposed and validated, providing a convenient and accurate method for practical application.

This study numerically evaluates a three-dimensional, turbulent, non-premixed syngas (a mixture of H2 and CO) flame issued from a round nozzle. The flow Reynolds number on the basis of the inlet velocity and the nozzle diameter is 16,700 and the flame is shrouded by a coflow under atmospheric conditions. A computational tool with a modified k-omega turbulence model and eddy dissipation model is used for simulating the reacting flow and its immediate surroundings. The outcomes are first compared against the existing experimental data. This reveals that when β*, as a constant coefficient in the k-omega turbulence model, is 0.073, the numerical results match the experimental data with high accuracy. Subsequently, the effects of variations in the diameter of the inlet nozzle and its geometry are investigated. This shows that an increase in the inlet nozzle diameter leads to the downstream movement of the high-temperature region diminishing combustion efficiency. Importantly, it is shown that using the elliptical inlet nozzle with the large diameter of 1.2 based nozzle diameter (4.48 mm) assists the combustion performance and increases the maximum combustion temperature by up to 9.6%. It also results in a considerable reduction of the unburned fuels and enhances the flow residence time significantly.

The presence of suspended contaminants in water and wastewater such as algae, colloids, fats and oil, necessitates the use of systems such as dissolved air flotation (DAF) for their removal. In the current study, a novel setup has been proposed for bubble enhancement. An industrial scale (pilot) DAF system was tested at saturator pressures of 3 to 7 atm and flow rates of 5 to 20 L/min in three different configurations, namely, empty, packed, and the innovative two-stage (TS) configuration. In the TS system, after the nucleation of micro bubbles, the water is returned to the saturator to undergo pressurization for a second time before it is passed through the nozzle once more and is released. The results show that the highest volume of released air as well as the smallest microbubbles are seen in the TS configuration, followed by packed mode, with the empty configuration showing the least favorable results. Moreover, the bubbles produced at the lowest residence time and pressure (3 atm) with the novel setup are better than the bubbles produced by the standard configuration even with pressures as high as 7 atm. Thus, the novel TS setup can allow for significantly lower energy requirements and lower capital costs. For real-world application of the TS system, the feed for the saturator would have to be extracted from within or near the contact zone, i.e., where the bubbles are released in the DAF tank.

The impact of the length of axially segmented lifters, as used in industrial rotary drums, on their process behavior and in particular the axial solids transport is analyzed in this study. Experime...

We observe the impact of bouncing and floating of water drops on a pool of immiscible volatile oil pools at low Weber numbers. The residence time of the impacting drop ranges from a few milliseconds to a few seconds before it sinks into the lighter oil phase. It is hypothesized that the confined evaporation from the volatile oil pool replenishes the thin film draining and results in prolonged floating and delayed sinking of drops into the oil pool. Water drops are released from a low height to impact on volatile hydrocarbon oil deep pools of various volatilities. The floating dynamics and residence times are captured using high-speed imaging. A theoretical model for the residence time has been developed to evaluate the hypothesis. The drop residence time is found to be directly proportional to the volatility of the oil pool in accordance with the hypothesis. The mathematical model incorporating the coupled confined evaporation and film draining dynamics is found to be in well agreement with the experimentally observed residence time. The bouncing-sinking regime map has been developed based on the experimental data.

O presente trabalho analisa as alterações morfológicas ocorridas no Complexo Estuarino Lagunar Mundaú-Manguaba (CELMM), através de técnicas de geoprocessamento e da modelagem computacional. Inicialmente realizou-se uma análise multitemporal das variações das linhas de costa entre o período de 1986 até 2017 a partir de imagens dos satélites Landsat 5-TM e Landsat 8-OLI. As imagens foram vetorizadas em ambiente de Sistema de Informações Geográficas (SIG) para a posterior realização do cálculo das taxas de erosão e acreção. Após isso, algumas simulações foram realizadas com o auxílio do Sistema Base de Hidrodinâmica Ambiental (SisBaHiA®) para os parâmetros tempo de residência e idade da água, considerando três cenários com configurações de embocaduras distintas (2006, 2014 e 2017). Os resultados indicaram o predomínio da deposição de sedimentos na região da embocadura, com a dinâmica migratória no sentido sudoeste-nordeste. O tempo de residência apontou possíveis áreas de estagnação na região noroeste da laguna Manguaba e nas porções noroeste e sudeste da laguna Mundaú. O cenário de 2014 apresentou menores idades das águas, mostrando que as diferentes configurações de embocaduras interferem na renovação das águas do complexo estuarino lagunar.

Closed-loop geothermal energy recovery technology has advantages of being independent of reservoir fluid and permeability, experiencing less parasitic load from pumps, and being technologically ready and widely used for heat exchange in shallow geothermal systems. Commercial application of closed-loop geothermal technology to deep high-enthalpy systems is now feasible given advances in drilling technology. However, the technology it uses has been questioned due to differences in heat transport capacities of convective flow within the wellbores and conductive flux in the surrounding rock. Here we demonstrate that closed-loop geothermal systems can provide reasonable temperature and heat duty for over 30 years using multiple laterals when installed in a suitable geological setting. Through use of two analytical methods, our results indicate that the closed-loop geothermal system is sensitive to reservoir thermal conductivity that controls the level of outlet temperature and interference between wells over time. The residence time of the fluid in the horizontal section, calculated as a ratio of the lateral length to flow rate, dictates heat transport efficiency. A long vertical production section could cause large drops in fluid temperature in a single lateral production system, but such heat loss can be reduced significantly in a closed-loop system with multiple laterals.

In this study, a wet electrostatic precipitator (WESP) with combination of electric field and charged water drop atomization was designed for fine particle collection, which replaced the traditional water film and mechanically spray. The removal performance was evaluated considering applied voltage, water flow rate, gas residence time, dust concentration, and continuous operation time. Results indicated that supplying charged droplets could acquire higher discharge current and better agglomeration effect than the dry type. The maximum penetration ratio was reduced from 3.8%−11.56% in the dry ESP to 3.58%−8.6% with charged droplets, as the applied voltage increased from 30 kV to 60 kV. Meanwhile, increase of water flow rate improved the total removal efficiency. The advantage of the WESP was more obvious under short gas residence time. The route of synergistically increasing gas residence time and applied voltage could largely reduce the penetration ratio, which decreased from 6.99%−19.81% to 1.03%−2.43% as they were enhanced from 1.50 s and 30 kV to 3.33 s and 60 kV. Increasing the dust concentration led to the trend that the total removal efficiency first increasing and then decreasing gradually, resulted from combined mechanisms of particle agglomeration and suppression of corona current. Moreover, the atomization of charged water drop maintained the advantage on particle removal under continuous operation, and the efficiency drop after long-term operation could be avoided. In particular, the WESP achieved significant reduction on water consumption compared to conventional large-scale and on-site WESPs in application with equivalent levels of removal efficiency.

International audience; Jet clarifier combines jet hydrodynamics, flocculation and settling in a unit operation. Generally, Camp and Stein G t parameter is recommended to evaluate clarifier efficiency, where G stands for a global velocity gradient and t a characteristic time scale (contact time). In this work, a quasi-two-dimensional jet clarifier is developed to make easier the hydrodynamic analysis of the flocculation zone of a jet clarifier. Measurements of instantaneous velocity field are performed by means of particle image velocimetry (PIV). PIV data are processed to visualise the strong circulation induced by the jet in the flocculation zone. Characteristic time scales related to macromixing are then extracted. Based on PIV data processing, local and instantaneous shear rate are estimated. The analysis of space averaged velocity gradient G is presented. The range of G is 2-15 s-1 whereas the residence time decreases from 4 to 1 h. Based on the hydrodynamic analysis, the parameter Gt is shown to be constant around 30,000 for different jet flow rates. Efficiency of such jet clarifier can thus be foreseen.

A reversed gas feed configuration for Hall thrusters is proposed and studied numerically. As an alternative to standard direct injection, we investigate the effect of injecting the propellant near the channel exit and directing it backwards, towards the anode. The resulting neutral density and average velocity fields are studied with the Direct Simulation Monte Carlo method for both cold and warm anode conditions. The residence time of neutral particles inside the channel and in the ionization region is computed using a test-particle Monte Carlo method. The computations indicate that the reversed injection allows for increasing the mass utilization efficiency of a standard feed configuration from 2-5% to a maximum of 20-30% depending on the initial efficiency.

An active pharmaceutical ingredient is currently produced in a traditional batch antisolvent crystallization process. Although well-established, this process lacks flexibility to control the crystal size distribution (CSD). Therefore, a new process was developed to enable the control of the CSD according to different specifications. This new process was implemented in continuous in a planar oscillatory flow crystallizer (planar-OFC). In this work, the main goal was to enable the production of small crystals to meet very specific formulation requirements and, simultaneously, promote the aggregation of these small particles to optimize the filtration operation. First, the operating conditions were optimized for continuous operation. Then, the planar-OFC was divided into two spatially independent sections, the nucleation zone (where nucleation is dominant) and the crystal growth zone (where crystal growth is dominant), so as to control the CSD as a function of the residence time in each zone. In particular, the formation of aggregates could be promoted by increasing the residence time in the nucleation zone. Ultimately, the planar-OFC was able to produce smaller particles with significantly narrower CSDs than the traditional batch process. This is particularly important when small particle sizes are required, thus reducing manufacturing time and operating costs.

Simulations of the ventricular flow patterns during left ventricular assist device (LVAD) support are mainly performed with idealized cylindrical inflow, neglecting the influence of the atrial vortex. In this study, the influence of the left atrium (LA) on the intra-ventricular flow was investigated via Computational Fluid Dynamics (CFD) simulations. Ventricular flow was simulated by a combined Eulerian (carrier flow)/Lagrangian (particles) approach taking into account either the LA or a cylindrical inflow section to mimic a fully support condition. The flow deviation at the mitral valve, the blood low-velocity volume as well as the residence time and shear stress history of the particles were calculated. Inclusion of the LA deflects the flow at the mitral valve by 25°, resulting in an asymmetric flow jet entering the left ventricle. This reduced the ventricular low-velocity volume by 40% (from 6.4 to 3.9 cm3), increased (40%) the shear stress experienced by particles and correspondingly increased (27%) their residence time. Under the studied conditions, the atrial geometry plays a major role in the development of intraventricular flow patterns. A reliable prediction of blood flow dynamics and consequently thrombosis risk analysis within the ventricle requires the consideration of the LA in computational simulations.

A continuous synthesis method for the less than 10 nm core-shell upconversion nanoparticles was developed via coiled tube embedded flask reactors and a flow solvothermal co-participation reaction up to 300 °C. Fast nucleation of hexagonal nanocrystals in less than 9 min residence time was achieved owing to the excellent heating ability of the reactors, and a two-step reaction strategy was created for the synthesis of β-NaYF4:Gd,Yb,Er/Ho/Tm@NaYF4 particles without intermediate purification.

Small microplastic particles

In this paper, we proposed a microextraction approach for the extraction and separation of Mn(II) and Co(II) from sulfate solution simulating leachate of spent lithium-ion battery cathode materials using saponified di-(2-ethylhexyl)phosphoric acid system. The effects of the following operational variables were investigated: equilibrium pH, tri-n-butyl phosphate concentration, saponification rate, two-phase ratio and residence time. The results showcased that the microextractor can reach the extraction equilibrium within 20 s, thereby greatly reducing necessary extraction time comparing to that of conventional processes. The volumetric mass transfer coefficient showed 8–21 times larger than that of batch device. With the help of microextractor, 95% of Mn(II) was extracted with a single theoretical stage at a chosen two-phase ratio of 3:1, and the separation factor βMn/Co was as large as 65.5. In the subsequent stripping step, more than 99% of manganese from loaded phase was easily stripped under optimal conditions. The microextraction approach greatly enhances the mass transfer while enabling a continuous and controllable extraction process within a simple structure design. When extracting spent electrode material with microextractors, the comprehensive recovery of mangenese can reach 96%. The microextraction approach has a good applicability in the spent lithium-ion battery cathode materials recycling at both bench and industrial scales.

Process intensification research is concentrated on the use of the continuous flow microreactor over the conventional batch reactors due to the various advantages that bring this latter in terms of efficient micromixing and enhanced heat and mass transfer in small residence time. The continuous flow process has been successfully developed for many common reactions in the pharmaceutical and chemical industries. This paper explores the catalytic performance of Pd nanoparticles (NPs) in a continuous flow mode and studies different microreactors configuration, and their applications on the benchmark reaction model of 4-nitrophenol reduction in aqueous media by using sodium borohydride as a reducer. A PTFE Spiral Capillary Microreactor (SCM) was designed and compared to a Continuous Vessel Microreactor (CVM) for the reduction of 4-Nip into 4-Amp. Multiple equations were obtained from different microreactor configurations that can be used for the calculation of theoretical mean conversion and 4-nitrophenol concentration at the outlet of the microreactor. The kinetics studies of this reaction model already determined in batch reactor were confirmed by using pseudo-first order in continuous flow microreactor. The real microreactor (SCM) is acting as a plug flow reactor (PFR). The engineering aspects such as reaction conditions and microreactor model are discussed. This work studies the kinetics of the 4-Nip reduction for the first time with nanoparticles non supported in continuous flow. This work showed that the kinetic study of the reaction can be carried out successfully in SCM and advantageously in particular for short reaction times.

Recent computational fluid dynamics (CFD) studies have demonstrated the concurrence of atherosclerotic changes in regions exposed to prolonged blood residence. In this proof-of-concept study, we investigated a small but homogeneous cohort of large, cavernous carotid aneurysms (CCAs) to establish the clinical feasibility of CFD analysis in treatment planning, based on the association between pathophysiology and hemodynamics. This study included 15 patients with individual large CCAs. We identified calcifications, which indicated atherosclerotic changes, using the masking data of digital subtraction angiography. We conducted a CFD simulation under patient-specific inlet flow rates measured using magnetic resonance (MR) velocimetry. In the post-CFD analysis, we calculated the blood residence time ( $$\xi$$ ) and segmented the surface exposed to blood residence time over 1 s ( $${S}_{\xi >1}$$ ). We measured the decrease in volume after flow diversion using the original time-of-flight MR angiography data. Calcifications were observed in the region with $${S}_{\xi >1}$$ . In addition, the ratio of $${S}_{\xi >1}$$ to the surface of the aneurysmal domain exhibited a negative relationship with the rate of volume reduction at the 6- and 12-month follow-ups. Post-CFD visualization demonstrated that intra-aneurysmal swirling flow prolonged blood residence time under the condition of a small inlet flow rate, when compared to the aneurysmal volume. The results of this study suggest the usefulness of CFD analysis for the diagnosis of atherosclerotic changes in large CCAs that may affect the therapeutic response after flow diversion.

Pilot-scale mine water treatment facilities were operated for over four years at the Ilwol mine, South Korea. A steel slag-limestone reactor (referred to as the slag reactor) was tested and a successive alkalinity producing system (SAPS) and a SAPS incorporating slag from a basic oxygen steelmaking furnace were compared. The SAPS decreased Mn from 23.3 to 7.4 mg L−1 on average because the alkalinity generated led to saturation with rhodochrosite. Adding a slag reactor removed Mn down to levels of 0.002–1.8 mg L−1 from influent Mn as high as 17.1 mg L−1 with a residence time of 5–25 h. Mn-containing carbonates and oxides were precipitated, which was supported by the geochemical modelling and observed with scanning electron microscopy with energy dispersive spectroscopy. The increased alkalinity in the SAPS before the slag reactor helped remove Mn at a pH range of 8.0–8.3. Mn removal rates and Mn-standardized Mn removal rates in the slag reactor were 0.76 mg L−1 h−1 and 0.105 h−1 in average, respectively. The passive treatment of Mn using an Fe-pretreatment and alkalinity-generation system, a slag-limestone reactor, and a wetland rather than a SAPS including slag, an oxidation-settling pond, and a wetland is suggested to consistently meet the effluent standards for Mn and pH.

There is increasing interest in new protein sources for the food and feed industry and for the agricultural sector, and microalgae are considered a good alternative, having a high protein content and a well-balanced amino acid profile. However, protein production from microalgae presents several unsolved issues, as the biomass composition changes markedly as a function of cultivation operating conditions. Continuous systems, however, may be properly set to boost the accumulation of protein in the biomass, ensuring stable production. Here, two microalgae and two cyanobacterial species were cultivated in continuous operating photobioreactors (PBR) under nonlimiting nutrient conditions, to study the effects of light intensity and residence time on both biomass and protein productivity at steady state. Although light strongly affected biomass growth inside the PBR, the overall protein pool did not vary in response to irradiance. On the other hand, shorter residence times resulted in protein accumulation of up to 68 % in cyanobacteria, in contrast with green algae, where a minor influence of residence time on biomass composition was observed. Energy balance showed that light conversion to protein decreased with light intensity. Protein content was also related to energy costs for cell maintenance. In conclusion, it is shown that residence time is the key variable to increase protein content and yield of protein production, but its effect depends on the specific species.

This work discusses the effects of increasing laser power on the size data derived from NTA for particles of known size and scatterers in solutions of flufenamic acid in ethanol. We find that whilst a higher laser power reveals more particles as expected, their residence time changes due to laser-induced convection. This reduced residence time decreases the number of tracks available for individual particle size determination, shifting the size distribution to smaller values. This problem is overcome by using a shutter to inhibit the development of convection currents, increasing particle residence time and reducing the error on the size distribution. The detailed understanding of laser-induced convection permits more robust size characterisation of mesoscopic organic clusters, which play a key role in two-step nucleation theory., In nanoparticle tracking analysis, laser-induced convection increases the error on individual particle sizing.

The ore processed by grinding in the minerals industry is generally composed of two or more minerals, and thus multicomponent formulations are commonly used to simulate the grinding process. In this paper, batch studies were carried out by grinding magnetite, limestone, and magnetite/limestone mixture at different mixing ratios in a laboratory-scale stirred mill. The impact of mixing ratios on the volume fraction of the desired size (−45 + 10 μm) in the ground products, energy consumption, and residence time of the feed in the grinding chamber was studied. The breakage parameters of the material were predicted by the population balance model (PBM). The results indicated that the back-calculated particle size distribution (PSD) of ground products by PBM fitted well with the measured data. The correlation of breakage parameters and mixing ratio were discussed and then compared to the single mineral grinding results. In addition, the predicted PSD was analyzed and discussed by the attainable region (AR) method. A significant effect of specific energy input on the yield of the desired size in the ground products was elucidated. The energy consumption and residence time of one component in the grinding chamber were compared to the single mineral grinding results at the turning point and switch point.

Thermochemical gasification is a potential energy extraction pathway that converts biomass to gaseous fuel and chemical feedstock. Modelling of biomass gasification is an efficient and economical method to predict the gaseous fuel characteristics compared to experimentation, which incurs additional time and effort. The present work deals with kinetic modelling and analysis of CaO enabled biomass gasification to analyse the effect of steam to biomass ratio, sorbent addition and residence time on syngas composition in MATLAB platform. The model is developed by applying Arrhenius reaction kinetics for homogeneous, heterogeneous and tar cracking reactions associated with gasification. Rate of gasification, tar cracking and carbonation reactions are incorporated in the model to predict the effect of residence time of solid and gaseous reaction species in the final syngas constitution. Rate of generation of each chemical species is determined by considering the cumulative effect of reaction kinetics of the reactions considered. The developed model is validated for product gas composition with the experimental results of air–steam gasification. An RMS error of 3.66 is reflected when the model estimated syngas composition for air–steam gasification is compared with that of the experimental results. The uniqueness of the model is that it can predict the temporal variation of syngas species for steam-assisted air gasification in sorbent enabled environment for CO2 capture. It is also found that at a temperature of 1000 K, equivalence ratio of 0.25 and steam to biomass ratio of unity, H2 mole fraction has no appreciable increase beyond a sorbent to biomass ratio of 1. The developed model can be used to predict the effect of residence time on syngas composition for air–steam biomass gasification (with and without sorbent) for a steam to biomass ratio and sorbent to biomass ratio range of 0–2.

The discrete element method (DEM) is widely used to tackle problems associated with granular material processing. Its applications are diverse, ranging from powder mixing to transport and fluidized beds. Computational costs are a major issue with regard to DEM. Long process times combined with a large numbers of particles require simulations that can last months. In this paper we apply an extrapolation method based on pseudo-steady state DEM bulk behavior to allow for the long repetitive process to be completed. The extrapolation method is applied to two processes relevant to the pharmaceutical industry: continuous mixing and a tablet press feed frame. The results of the extrapolation method are validated against full DEM simulations of the complete process in terms of residence time, travel distance, and velocity distributions. The DEM extrapolation for pseudo-steady state processes resulted in an enormous reduction of the simulation time, while retaining residence times, travel distance and velocity distributions.

To design a particle solar receiver (PSR), a vital energy conversion system, is still a bottleneck for researchers. This study presents a novel PSR based on countercurrent fluidized bed (CCFB) technology, named CCFB receiver. In this design, downward-moving particles are subjected to the action of an up-flow gas to reduce the falling speed and enhance the radial disturbance, and hence increase the residence time of particles and improve the heat transfer. A cold-mold visual experimental setup is established. The influence factors are investigated experimentally, including the superficial gas velocity, solid flux, aeration gas, particle size and transport tube diameter. The results indicate that the maximum solid holdup can exceed 9% or so with fine particles of diameter dp = 113.5 µm and a tube diameter of 40 mm. It is proved that the CCFB can operate stably and adjust the solid flux rapidly. The results of this study provide a new structure for PSRs in the concentrated solar power field and could fill the research insufficiency in the gas-solid counterflow field.

Hampir di setiap kota di Indonesia banyak terdapat industri tempe skala rumahan. Industri-industri tersebut belum melakukan pengolahan limbahnya, sehingga mengakibatkan pencemaran air sungai. Keterbatasan dana menjadi kendala ketika pemilik industri membangun fasilitas pengolahan air limbah. Pembangunan fasilitas pengolahan air limbah yang tepat dan murah akan sangat bermanfaat bagi mereka. Kombinasi reaktor aerobik dan media biofilter merupakan proses pengolahan air limbah secara biologis dengan menggunakan media filter. Penelitian ini menggunakan sistem aerobik dengan variasi yang digunakan adalah waktu detensi selama 24, 48, 72, 96, 120 jam dan kombinasi konsorsium mikroorganisme. Parameter yang dianalisis adalah BOD, TSS, dan TDS. Dari penelitian didapatkan hasil efisiensi penyisihan yang optimal dengan konsorsium mikroorganisme pada reaktor A dengan waktu sampling 120 jam dan hasil akhir BOD 95,58%, TSS 24,82%, dan TDS 48,95%

The modified microsurfacing mix design procedure for polymer-modified bitumen emulsion (PMBE) is introduced in this study under the influence of emulsifiers, lead time and through application of SB...

Background:Conventional delivery systems like solution and suspension are commonly used for the treatment of ocular diseases but have low corneal residence time and hence the duration of effect is ...

In this study, two connected drop tube furnaces (DTFs) were used to clarify the NO emission characteristics during the high-temperature preheating-combustion process. The most important factors, including preheating temperatures, residence times, and excess air ratios (EAR), were studied systematically. Experimental results showed that both increasing the preheating temperature and prolonging the residence time in the preheating zone promoted the release of coal-N as volatile-N, the reduction of volatile-N, and the interaction between char-N and nitrogen-containing gases, and therefore enhanced NO reduction. With the EAR increased in the preheating zone, the NO emission first decreased and then increased. There was an optimal EAR for NO reduction, which was 0.4 in this work. Meanwhile, the lowest NO emission was 223 mg·m−3, corresponding conversion ratio of coal-N to NO was 12.6% and NO removal efficiency was 60.38%. Moreover, kinetic modeling confirmed the experimental results, and rate of production (ROP) analysis indicated that the main radicals for NO destruction were NH2, hydrocarbon (CiHj), HCCO, NCO and HCO. In addition, the NO reduction by CiHj was stronger than other nitrogen-containing compounds, except NH2, which contributed nearly 30% of overall NO destruction.

Sulfur compounds are major contaminants in diesel fuels and cause significant negative impacts on the environment, human health, and petroleum product quality. Oxidative desulfurization (ODS) has gained attention due to relatively mild operating conditions. However, ODS requires significant improvements in terms of productivity, reaction time, and conversion. This study reports the development of a highly efficient, rapid ODS process, in an oscillatory baffled reactor (OBR), to allow continuous, safe dibenzothiophene (DBT) removal. DBT conversion was studied as a function of temperature, residence time, oscillation frequency, and oscillation amplitude. By optimizing the operating conditions, up to 94 % DBT could be removed without further extraction in 3 min, at 80 °C, 4 Hz, and 6 mm. This is a substantial increase over comparable processes at this temperature and furthermore has been conducted in a reactor that scales up predictably, hence it is probable that this performance can be realized at an industrial scale.

A numerical study was carried out on the motion characteristics of rapeseeds in the two-phase flow of the distribution head of an air-assisted centralised seed-metering device based on coupled simulations using computational fluid dynamics (CFD) and discrete element method (DEM). The effects of various structural and working parameters on seed motion characteristics and airflow field were investigated. The results showed that motion characteristics, collision frequency and the residence time of seeds significantly varied. Studies of the effect of structural parameters showed that an appropriate diameter to height ratio (e.g., 2.0), lid angle (e.g., 120°) and distribution head with streamlined design could effectively facilitate the movement of seeds, reduce the frequency of seed–seed and seed-wall contacts, avoid excessive residence of seeds, and improve distribution performance. With increasing airflow velocity, the movement and seed-wall collision of seeds became more intense, and the average residence time reduced. Distribution uniformity and power consumption were improved for airspeeds of 20–24 m s−1 with the different rapeseed feed. The coefficient of variation of seed distribution measured in a bench test was less than 5.0%. The results will contribute to improving knowledge of the seed distribution characteristics and optimising the structure of distribution heads for the air-assisted centralised seed-metering devices.

In the context of the anaerobic digestion of slowly biodegradable substrates for energy and chemicals production, this study investigated the anaerobic digestion of cellulose without any chemical pre-treatments using open (undefined) mixed microbial cultures. The anaerobic conversion of cellulose was investigated in extended-length (run length in the range 518–734 days) batch and semi-continuous runs (residence time 20–80 days), at high cellulose concentration (20–40 g L−1), at temperatures of 25 and 35 °C. The maximum cellulose removal was 77% in batch (after 412 days) and 60% (at 80 days residence time) in semi-continuous experiments. In semi-continuous experiments, cellulose removal increased as the residence time increased however the cellulose removal rate showed a maximum (0.17 g L−1 day−1) at residence time 40–60 days. Both cellulose removal and removal rate decreased when cellulose concentration in the feed was increased from 20 to 40 g L−1. Liquid-phase products (ethanol and short chain organic acids) were only observed under transient conditions but not at the steady state of semi-continuous runs. Most of the observed results were well described by a mathematical model which included cellulose hydrolysis and growth on the produced glucose. The model provided insight into the physical phenomena behind the observed results.

This paper reports the first known comprehensive survey of combustion operating conditions across the wide range of municipal waste-to-energy facilities in the U.S. The survey was conducted in a step-wise fashion. Once the population of 188 units operating at over 70 facilities was defined, this population was stratified by distinguishing characteristics of combustion technology. Stratum-level estimates for operating conditions were determined from data collected in the survey. These stratum-level values were weighted by corresponding design capacity share and combined to infer national-level operating parameter estimates representative of the overall population. Survey results show that typical municipal waste-to-energy combustion operating conditions in the U.S. are (1) furnace temperature above 1160 °C, (2) gas residence time above 2.4 s, (3) exit gas concentrations of nearly 10% for oxygen (dry basis), and (4) over 16% for moisture. These operating parameter values can serve as benchmarks for laboratory-scale studies representative of municipal waste-to-energy combustion as typically practiced in the U.S.

Long residence time enzyme inhibitors with a two-step binding mechanism are characterized by a high internal energy barrier for target association. This raises the question of whether optimizing residence time via further increasing this internal energy barrier would inevitably lead to insufficient target occupancy in vivo due to slow, time-dependent binding. We attempted to address this question during optimization of cyclooxygenase-2 (COX-2) inhibitors. Defining long residence time drugs with acceptable association and dissociation rate constants required for sufficient target occupancy and sustained efficacy, which we termed "balanced internal energetics", provides an important criterion for successful progression during lead optimization. Despite the advancement of several COX-2 inhibitors to marketed drugs, their detailed inhibition kinetics have been surprisingly limiting especially during the structure-activity relationship process mainly due to the lack of robust kinetic assays. Herein, we describe a reoptimized COX enzymatic assay and a novel MS-based assay enabling detailed mechanistic studies for identifying long residence time COX-2 inhibitors with balanced internal energetics. These efforts led to the discovery of promising leads possessing dissociation half-lives of ≤40 h, much greater than the values of 6 and 0.71 h for two marketed drugs, etoricoxib and celecoxib, respectively. Importantly, the inhibition rate constants remain comparable to those of the marketed drugs and above the lower limits set by the criteria of balanced internal energetics, predicting sufficient target occupancy required for efficacy. Taken together, this study demonstrates the feasibility of increasing the internal energy barrier as a viable approach for lead optimization toward discovering long residence time drug candidates.

Along with the increasingly stringent dust emission concentration standards for the thermal power plants and the challenge of market competition, wet electrostatic precipitators (ESPs) have been widely used as terminal equipment for the flue gas treatment. The wet ESPs pilot test platform using the modified carbon steel collectors with hydrophilic properties was established in this paper and the experimental research on PM2.5 removal characteristics were carried out. The mechanism of the particles removal efficiency enhancement by water film on the surface of modified collectors was studied. The effect of gas temperature, residence time, working voltage, inlet concentration, and flushing water flowrate on the particles removal efficiency was investigated. The results indicated that the fibrous layer over the surface of the modified collectors could reduce the effect of the airflow recoil and the electromigration resistance of particles. The surface of the modified collectors could also maintain a uniform and stable water film with a lower amount of water consumption. The water film could restrain the back corona and the re-entrainment of dust. And the evaporation of water film increased the humidity of the flue gas, meanwhile, the particles charge capacity and electromigration velocity increased. Those all could improve the particles removal efficiency. The particles removal efficiency increased with the increase of the flue gas residence time and the applied voltage, but the particles removal efficiency improved less with the increase of the particles inlet concentration and flushing water flow rate after maintaining uniform and stable water film. The modified rigid collector provided high removal efficiency for particles with diameters of 0.04～0.48 μm under lower energy and water consumption.Implications: The wet electrostatic precipitators (ESPs) have been widely used as terminal equipment of the flue gas treatment to purify the flue gas deeply. The surface of the modified carbon steel collectors with hydrophilic properties could maintain a uniform and stable water film with a lower amount of water consumption. The evaporation of water film improved the particle charge capacity and electromigration velocity. The wet ESPs using the modified rigid collector exhibited significantly higher removal efficiency of particles than using the conventional rigid collector especially to the particles with diameter of 0.04～0.48 μm.

Atmospheric water vapour residence time (WVRT) is an essential indicator of how atmospheric dynamics and thermodynamics mediate hydrological cycle responses to climate change. WVRT is also important in estimating moisture sources and sinks, linking evaporation and precipitation across spatial scales. In this Review, we outline how WVRT is shaped by the interaction between evaporation and precipitation, and, thus, reflects anthropogenic changes in the hydrological cycle. Estimates of WVRT differ owing to contrasting definitions, but these differences can be reconciled by framing WVRT as a probability density function with a mean of 8-10 days and a median of 4-5 days. WVRT varies spatially and temporally in response to regional, seasonal and synoptic-scale differences in evaporation, precipitation, long-range moisture transport and atmospheric mixing. Theory predicts, and observations confirm, that in most (but not all) regions, anthropogenic warming is increasing atmospheric humidity faster than it is speeding up rates of evaporation and precipitation. Warming is, thus, projected to increase global WVRT by 3-6% K-1, lengthening the distance travelled between evaporation sources and precipitation sinks. Future efforts should focus on data integration, joint measurement initiatives and intercomparisons, and dynamic simulations to provide a formal resolution of WVRT from both Lagrangian and Eulerian perspectives. Universidad de Costa Rica/[805-B9-519]/UCR/Costa Rica Gobierno de España/[RTI2018-095772-B-I00]/LAGRIMA/España Ministerio de Ciencia, Innovación y Universidades/[]//España European Regional Development Fund/[]/ERDF/España Xunta de Galicia/[ED481B 2018/069]//España Xunta de Galicia/[ED413C 2017/64]//España Fulbright Program/[]//Estados Unidos Centro Universitario de la Defensa/[]/CUD/España Netherlands Organization for Scientific Research/[016.Veni.181.015]/NWO/Países Bajos National Science Foundation/[1454089]/NSF/Estados Unidos Research Council of Norway/[262710]/RCN/Noruega European Research Council/[773245]/ERC/Bélgica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI) UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Física

Oil and coal reserves are still abundant and are part of a strategy to assure safe energy in almost every energy matrix around the world. Nevertheless, it is important to look for solutions that reduce the negative impacts of burning fossil fuels. CO2 capture in thermoelectric plants is a significant alternative in favor of this technological need. In the present study, CO2 adsorption in a zeolite-based bench scale prototype was evaluated numerically and experimentally considering the constructive and operational parameters of the bench unit. The configuration of the plates and the zeolites flow pattern were studied considering the residence time (RT) and CO2 capture capacity. A residence time of 13 s was reached experimentally with simple modifications on the number of plates of the unit. The efficacy of the CO2 removal was high, reaching 95.5% for a RT of 10.65 s and 99.33% for a RT of 15 s. The numerical results showed good agreement with the experimental data with a maximum error of 10% for the residence time, and 6% for the adsorption capacity. The herein study is a contribution to make the CO2 capture technology viable by Moving Bed Temperature Swing Adsorption (MTBSA) adsorption column with zeolite and indicating optimum operational parameters leading to higher efficiency levels.

A highly scalable combined modular and 3D-printed falling film crystallization device is developed and demonstrated herein; the device uses a small, complex, printed overflow-based film distribution part that ensures formation of a well-distributed heated liquid film around a modular, tubular residence time/crystallizer section, enabling extended residence times to be achieved. A model API (ibuprofen) and impurity (ibuprofen ethyl ester) were used as a test system in the evaluation of the novel crystallizer design. The proposed crystallizer was run using three operational configurations: batch, cyclical batch, and continuous feed, all with intermittent removal of product. Results were suitable for intermediate purification requirements, and stable operation was demonstrated over multiple cycles, indicating that this approach should be compatible with parallel semicontinuous operation for intermediate purification and solvent swap applications in the manufacture of drugs.

Maximizing separation sharpness is critical for the design and operation of hydrocyclones but remains difficult to achieve. This work presents a numerical study on the relationship between separation performance and the characteristics of axial velocity wave zone to understand the reasons for the limited separation sharpness. The results showed that this zone is featured as an inherent transition region, with extensive secondary vortices formed between inner and outer spiral flows. The presence of this zone adversely affects the fluid-solid momentum transfer, causing prolonged residence time and accumulation of intermediate-sized particles. The separation sharpness shows a strong dependence on the characteristics of axial velocity wave zone, which are further controlled by geometric parameters. Increasing the symmetry of flow field and optimizing the spatial distribution of this zone can help increase the separation sharpness while its size shows little effect.

In tablet manufacturing, mixing operations in tumble blending (TB) and in the feed frame (FF) of the rotary press can both increase lubricity, negatively influencing the tablet mechanical strength. While the TB-driven lubrication was systematically studied, no reliable bench-scale methods exist for the effect of FF lubrication. Because TB and FF mixing are usually two successive operations in tablet manufacturing, we developed a phenomenological model to incorporate the impact of TB-driven lubrication and the FF lubrication on the tablet tensile strength (TS). We noted that exponential decay functions can describe the evolution of the tablet TS as the function of the extent of TB, as well as the residence time in FF. Hence, the overall lubrication sensitivity can be modeled by incorporating two distinct exponential decay functions. The model can be calibrated through bench-scale experiments. Using an investigational powder blend, we showed that this approach accurately predicted the tablet TS in a scale-up tablet compression study, thereby verifying its utility. This model can serve as a scale-up diagnostic and risk-assessment tool, with the ability to adjust the overall effect of lubrication by changing the TB scale and the FF residence time commensurate with the large-scale operations.

The high-temperature syngas and molten slag droplets discharged from entrained-flow coal gasifiers contain a large amount of heat energy, which can be efficiently recovered by radiant syngas coolers (RSCs). However, it is hard to know the solidification degree of molten slag droplets at the outlet of an RSC during industrial operations. In this work, the industrial-scale RSC and molten slag droplet models are established to predict the solidification degree of slag droplets at the outlet of the RSC. Then, the effects of slag diameter, syngas flow field, slag initial temperature, slag porosity, and slag pore structure are investigated by numerical simulations, and residence time as well as complete solidification time are calculated by coupling of a discrete-phase model and a solidification model. The results indicate that as the slag droplet diameter increases, the residence time of the slag droplet shortens, but the complete solidification time increases. When the slag droplet diameter is greater than or equal to 3.0 mm, the complete solidification time is larger than the residence time, and the slag droplet cannot solidify completely at the outlet of the RSC. The solidification degree in the windward zone is greater than that in the leeward zone. Although the slag initial temperature has little effect on the solidification, a lower slag initial temperature is still conducive to a greater solidification degree. Additionally, the pore structure facilitates solidification, and the promoting effect of penetrated pores is more remarkable than that of closed pores. A larger porosity is also beneficial to accelerate the solidification of molten slag droplets and increase the solidification degree.

Residence time of late-race sockeye spawners on spawning grounds located in the littoral zone of Lake Nachikinskoye in southern Kamchatka is determined directly using 11 series of tagging and tracking of tags conducted in 2018 and 2020 (700 tagged individuals). The residence time is the key parameter for calculation of the spawners number on the data of repeated observations from the beginning to the end of spawning. Methodology of the experiment is described in details and all data of measurements are presented. Impact of certain variables on the target function is discussed. The residence time is estimated as 5 days.