Static Bed Research Articles

Sorptive uptake of Ranitidine hydrochloride by Parthenium hysterophorus based chemically treated N-biochar in static bed continuous flow system

The current work explored the sorptive efficacy of hazardous Parthenium hysterophorus based chemically treated N-biochar (PH-ANB) as a promising sorbent to eradicate ranitidine hydrochloride (R.H.) from synthetic aqueous solution in a miniaturized column with a static bed. PH-ANB was studied by S.E.M., B.E.T surface area analyzer, the point of zero charges (pHpzc), and X-ray diffraction analyzer (XRD). The breakthrough curves were generated based on the experimental studies to verify the effects of flow rate ( 2–6 mL min−1), bed depth (1–3 cm), and R.H. concentration (100–200 mg L−1) in column study. PH-ANB exhibited the highest sorptive capacity of 34.29 mg −1 at an optimum bed depth, volumetric flow rate, and initial R.H. concentrations of 3 cm, 2.0 mL min −1, and 200 mg L−1, respectively. The data derived from the column study were fitted into Thomas, Adams–Bohart, and Yoon–Nelson models. The Yoon–Nelson model provided the most appropriate fit for mathematically explaining R.H. removal in column studies over other models. The column study results suggested that PH-ANB could be quite efficacious in R.H. removal through continuous operation.

Prediction of Fluctuation, Expansion Ratios and Gas Hold Up in a Three Stage Gas-solid Fluidized Bed – A Statistical Approach

Multistage fluidized bed has shown greater performance than the single stage in terms adsorption efficiency, recovery efficiency etc. Thus, experiments have been carried out in a three stage gas-solid fluidized bed. The hydrodynamic characteristicssuch as fluctuation ratio, expansion ratio and gas holdups have been studied. The dependency of these quantities with the system variables like particle size, initial static bed height and superficial gas velocity in each stage of a three-stage fluidized bed have been analyzed. It has been found that both fluctuation and expansion ratios are inverse functions of particle size and static bed height whereas a direct function of superficial gas velocity. However the gas holdup is a direct function of all the three operating parameter.It has also been observed that bed fluctuation and expansion goes on decreasing from lower bed to the upper bed. Further correlations have been developed for all the three stages for fluctuation ratio, expansion ratio and gas holdup using statistical analysis. It has been found that the experimental values of the responses agree well with the values predicted from the models.

Cartesian grid simulation of reacting gas-solid flow using CFD-DEM-IBM method

The computational fluid dynamics-discrete element-immersed boundary method (CFD-DEM-IBM method) is extended to simulate the decomposition of ozone in a cylindrical bubbling fluidized bed, where the effect of complex geometries on the fluid flow is imposed by immersed boundary method. The expanded bed height and the global circulation patterns obtained from CFD-DEM-IBM simulations are in a good agreement with the results reported in literatures. The effects of inlet gas velocity and static bed height on the ozone conversion are also investigated, and the simulation results are consistent with the experimental data of Fryer and Potter (Fryer and Potter, 1976 [1]). Present study proved the feasibility of simulation of catalytic reaction processes in fluidized beds with complex geometries using CFD-DEM-IBM method.

Experimental investigation on the impact of tube bundle designs on heat transfer coefficient in gas-solid fluidized bed reactor for Fischer-Tropsch synthesis

The impact of vertical heat exchanging tube bundle on heat transfer coefficient (HTC) has been investigated locally and instantaneously using a sophisticate heat transfer technique using glass beads solid particles of 210 μm average size and 2500 kg/m3 solid density (Geldart B particles), with a static bed height of 0.35 m as bed material. A mimicked Fischer-Tropsch fluidized bed with vertical heat exchanging tubes is designed and built in this study. Heat transfer performance is also investigated by using two different tubes arrangement (square-pitch and triangular-pitch tubes arrangement). To represent the heat exchanging tubes used in the Fischer–Tropsch process, stainless-steel heat exchanging tubes inserted vertically, each with a diameter of 0.012 m, were used in each tubes arrangement occupying 25% of the column cross-section area. The experiments were performed in a 0.13 m inner diameter Plexiglas fluidized bed reactor with varied gas flowrates (0.2–0.48) m/s at numerous radial positions along the diameter of the column (±0.58, ±0.33, and ± 0.03) and two axial locations (H/D = 1.153 and 1.923). It was found that HTCs significantly enhance with increasing the gas flowrates for all radial positions for square-pitch tubes arrangement. While different behavior can be noticed in the radial positions with triangular-pitch tube arrangement, especially near the wall region (±0.33). Also, the local heat transfer coefficient (LHTC) improved with increasing the axial positions by 12.06% at highest gas flowrates (0.48 m/s). Moreover, the square-pitch tubes arrangement showed a significant increase and uniformity in HTC when measured instantaneously comparing with other tubes arrangement. Furthermore, the findings of this study will improve awareness of vertical tubes' effect on heat transfer in a fluidized bed reactor. Moreover, the data acquired from this investigation can be employed to validate reactor models, CFD codes, and simulations in order to support the design and scale-up processes of such reactors.

High performance fluidized bed photoreactor for ethylene decomposition

Abstract Removal of C2H4 in the air was carried out in the continuous flow reactor with the photocatalytic bed (expanded polystyrene spheres coated by TiO2 or SiO2/TiO2) under irradiation of UV light. Continuous flow of a gas stream through the reactor was realised at the static bed and under bed fluidization. The required flow of a gas stream through the reactor for bed fluidisation was 500–700 ml/min, whereas for the static bed the flow rate of 20 ml/min was used. Fluidized bed reactor appeared to be much more efficient in ethylene removal than that with the stationary bed. It was caused by the increased speed of C2H4 mass transfer to the photocatalyst surface and better utilization of the incident UV light. In the fluidized bed reactor calculated rate of C2H4 degradation was around 10 μg/min whereas in the stationary state 1.2 μg/min only.

Bed hydrodynamics of a new three-phase fluidized bed flotation column with steel ball particles

The new three-phase fluidized bed flotation column (TFC) hydrodynamics characteristics, such as gas holdup, bubble diameter and bubble surface area flux have been carried out, and this study focuses on bed fluid hydrodynamic parameters of the TFC. The bed hydrodynamic characteristics viz., bed fluctuation ratio (r), bed expansion ratio (R) and bed voidage (ε) of the TFC have been studied using air as the discontinuous phase and water as the continuous phase, respectively. The effects of the system parameters studied include superficial gas, liquid velocities and initial static bed height (H0). Experimental studies based on the Response surface methodology (RSM) have been made to investigate the mathematical model of hydrodynamic parameters (r, R, ε) and bubble diameter (Db) of the TFC. The results show that the models which were established by operating variables can predict the r, R, ε and Db of the TFC well. Based on the previous investigation of the optimization of bubble performance parameters which has been caried out by Liu et al. (2020), the correlation of Db has been carried out, and the result shows that H0 is the boundary condition that determines the variation of Db. The optimization of Db by RSM shows that relatively small bubbles can be obtained when H0 is greater than 0.290 m within the range of parameters studied. The values of the experiment have been compared with those predicted by the proposed models and have been found to agree well.

Specialised psychiatric beds and 24-hour residential care in Australia 2018-2019 - Comparative analysis and commentary according to international benchmarking.

A commentary on Australian specialised private and public psychiatric acute and non-acute inpatient care, and 24-hour-staffed community residential care with regard to international benchmarks. Descriptive analysis of specialised psychiatric beds from the Australian Institute of Health and Welfare (AIHW) with the WHO Mental Health Atlas 2020, and an international Delphi consensus on optimal and minimal psychiatric beds per capita. Australian private sector beds have shown a 3.8% annual growth rate from 2014-15 to 2018-19, in contrast to relatively static public sector bed numbers. Australia's national combined public and private psychiatric bed number (hospital acute and non-acute, and 24-hour-staffed community residential) of 48.8 per 100,000 population is lower than the WHO European (100.6) and World Bank High Income (69.2) medians, due to fewer community residential and non-acute beds. Australia's 40.9 general and stand-alone psychiatric beds per 100,000 are below the Delphi consensus optimal level of 60 beds per 100,000, but above the bed shortage threshold (30 per 100,000). Rising bed numbers in private hospitals have contributed to Australian psychiatric inpatient capacity, although the level remains below comparable international medians. Recent initiatives to increase psychiatric bed numbers may signal a policy shift in the public sector, complementary to private and community care.

Intensification of coal slime separation in fluidized bed flotation column: change of turbulence

ABSTRACT Flotation cell and flotation column are widely used as the separation equipment for coal slime. In order to obtain better flotation results for different particle sizes, different turbulence intensity of flow field need to be created, but the turbulence intensity is not easy to adjust in conventional flotation equipment. In this paper, a new fluidized bed flotation column was designed to control turbulence intensity by the liquid velocity and static bed height. The effects of liquid velocities (0.198 m/s,0.226 m/s,0.254 m/s) and static bed heights (0.317 m,0.343 m,0.380 m) on coal slime flotation with different particle sizes were studied, which were evaluated by the combustible recovery, ash content, and the yield of clean coal. The research results showed that the flotation performance of coarse particles is better with low turbulence caused by low liquid velocity and great static bed height than that in high turbulence. Under the condition of high liquid velocity and low bed height, a high turbulence intensity environment is created, and the fine particle separation efficiency is better than that in low turbulence.

A Detailed Insight into Acoustic Attenuation in a Static Bed of Hydrophilic Nanosilica.

The commercial utilization of bulk nanosilica is widespread in concrete, rubber and plastics, cosmetics and agriculture-related applications, and the market of this product is projected to exceed USD 5 billion by 2025. In this investigation, the local dynamics of a nanosilica bed, excited with sinusoidal acoustic waves of different frequencies, were carefully monitored using sensitive pressure transducers to obtain detailed insights into the effectiveness of sound waves as a means of energy transport inside the bed. The evolution of wave patterns and their frequency and power distributions were examined both in the freeboard and in the static bed. These results were compared with those obtained by using an empty column. The acoustic frequency strongly affected the signal power. The average power of the acoustic signal in the freeboard region was twice higher than that for the empty column, whereas the same (power) ratio decreased to approximately 0.03 inside the bed for 300 Hz. However, at 360 Hz, the power ratio was substantially lower at 0.24 and 0.002 for the freeboard and the granular bed, respectively, thereby indicating tremendous attenuation of acoustic waves in the granular media at all frequencies.

An experimental study on the startup velocity and motion characteristics of sand beds in air–water pipelines

AbstractSand deposition in the wellbore is one of the most common problems in oil–gas and hydrate exploitation work. A detailed understanding of the migration characteristics of the sand bed and accurate prediction of the starting velocity of the sand bed are key aspects of effective sand carrying. Therefore, this study conducted a large‐scale outdoor gas–water–sand three‐phase flow experiment. The effects of critical factors such as flow pattern, sand size, sand bed height, and pipe inclination angle on sand bed startup velocity and migration were studied experimentally. The experimental results indicated that during the startup process of the sand bed, sand particles exhibited three states: rolling, jumping, and suspension. During the experiment, the sand bed morphology included a static bed, rolling bed, jumping bed, and suspension bed. Compared to a stratified flow, intermittent flow and agitated flow were more beneficial for the startup velocity of sand beds. An increase in pipe inclination also reduced the starting velocity of the sand bed. With an increase in sand size, the startup velocity of the sand bed increased correspondingly. However, there was no significant influence on the migration morphology of the sand bed. Additionally, the greater the thickness of the sand bed, the lower the starting velocity of the sand bed. Based on the stress states of sand grains, in combination with experimental data, this study used least‐squares estimation to establish a prediction model for the startup velocity of sand beds. The model prediction results were in good agreement with the experimental data. This study will provide a basis for predicting the startup velocity of sand beds during the gas–liquid two‐phase sand‐carrying process.

Measuring binary fluidization of nonspherical and spherical particles using machine learning aided image processing

AbstractThe binary fluidization of Geldart D type nonspherical wood particles and spherical low density polyethylene (LDPE) particles was investigated in a laboratory‐scale bed. The experiment was performed for varying static bed height, wood particles count, as well as superficial gas velocity. The LDPE velocity field were quantified using particle image velocimetry (PIV). The wood particles orientation and velocity are measured using particle tracking velocimetry (PTV). A machine learning pixel‐wise classification model was trained and applied to acquire wood and LDPE particle masks for PIV and PTV processing, respectively. The results show significant differences in the fluidization behavior between LDPE only case and binary fluidization case. The effects of wood particles on the slugging frequency, mean, and variation of bed height, and characteristics of the particle velocities/orientations were quantified and compared. This comprehensive experimental dataset serves as a benchmark for validating numerical models.

Infrared temperature measurements and DEM simulations of heat transfer in a bladed mixer

AbstractAn understanding of heat transfer in a bladed mixer is important for drying of pharmaceutical drug crystals. This study presents thermal imaging experiments of the particle bed surface in a bladed mixer to investigate how the impeller speed influences the rate and the uniformity of heat transfer. Next, the process is simulated using the discrete element method. The bed thermal properties are lumped into an effective thermal conductivity, that is calibrated for one impeller speed. The experiments and the simulations show the same trends and generally agree well for all agitated beds. However, to obtain good agreement of the rate of heat transfer between the simulations and experiments in a static bed, we need to adopt a higher thermal conductivity than for the agitated beds. Finally, we discuss the implications of these results for the design of operating protocols.

Fluidization of the spherocylindrical particles: Comparison of multi-sphere and bond-sphere models

The fluidization of spherocylindrical particles is widely encountered in many engineering applications. In this work, by using the computational fluid dynamic-discrete element method (CFD-DEM), both the multi-sphere and bond-sphere models are developed, validated, and applied to investigate the fluidization characteristics of almost rigid spherocylinders. The differences between the two models are highlighted. Results show that the particle resolution of the multi-sphere model has a great impact on the pressure drop of the stationary bed but a small effect on full fluidization behaviors. More particles tend to be in the vertical direction by using the bond-sphere model, whereas the multi-sphere model predicts a more horizontal particle orientation. A left–right symmetrical particle flow pattern is observed for the multi-sphere model while a particle circulation configuration across the whole bed width appears for the bond-sphere model. All these observations are helpful for selecting particle model and deeply understanding the fluidization of spherocylindrical particles.

Environmental Assessment of a Diesel Engine Fueled with Various Biodiesel Blends: Polynomial Regression and Grey Wolf Optimization

A series of tests were carried out to assess the environmental effects of biodiesel blends made of different vegetable oil, such as corn, sunflower, and palm, on exhaust and noise diesel engine emissions. Biodiesel blends with 20% vegetable oil biodiesel and 80% diesel fuel by volume were developed. The tests were conducted in a stationary diesel engine test bed consisting of a single-cylinder, four-stroke, and direct injection engine at variable engine speed. A prediction framework in terms of polynomial regression (PR) was first adopted to determine the correlation between the independent variables (engine speed, fuel type) and the dependent variables (exhaust emissions, noise level, and brake thermal efficiency). After that, a regression model was optimized by the grey wolf optimization (GWO) algorithm to update the current positions of the population in the discrete searching space, resulting in the optimal engine speed and fuel type for lower exhaust and noise emissions and maximizing engine performance. The following conclusions were drawn from the experimental and optimization results: in general, the emissions of unburned hydrocarbon (UHC), carbon dioxide (CO2), and carbon monoxide (CO) from all the different types of biodiesel blends were lower than those of diesel fuel. In contrast, the concentration of nitrogen oxides (NOx) emitted by all the types of biodiesel blends increased. The noise level produced by all the forms of biodiesel, especially palm biodiesel fuel, was lowered when compared to pure diesel. All the tested fuels had a high noise level in the middle frequency band, at 75% engine load, and high engine speeds. On average, the proposed PR-GWO model exhibited remarkable predictive reliability, with a high square of correlation coefficient (R2) of 0.9823 and a low root mean square error (RMSE) of 0.0177. Finally, the proposed model achieved superior outcomes, which may be utilized to predict and maximize engine performance and minimize exhaust and noise emissions.

Numerical Simulation of Effective Hole Cleaning by Using an Innovative Elliptical Drillpipe in Horizontal Wellbore

In the drilling of horizontal wells, the drill cuttings tend to settle down on the low side of the annulus due to gravity and form a stationary bed, which results in hole cleaning problems. In this paper, a novel type of drillpipe with an elliptical shape was proposed to alleviate inadequate hole cleaning during the drilling of horizontal wells. A three-dimensional computational fluid dynamic (CFD) Eulerian-Eulerian approach with the Realizable k-ɛ turbulence model was developed to predict the solid–liquid two-phase flow in the annular space. Numerical examples were given to investigate the influence of different parameters on cuttings’ transport behavior, and the elliptical drillpipe was compared with the circular drillpipe. The annular cuttings concentration, annular pressure drop, and hole cleaning efficiency were evaluated. The numerical results clarify the potential of the elliptical drillpipe to enhance the hole cleaning efficiency without significantly increasing the annular pressure drop. Due to the swirl flow and secondary flow caused by the rotation of the curvature wall, the swaying phenomenon of drill cuttings’ distribution along the rotation direction of drillpipe was observed and enhanced the cuttings transport ability. Using the elliptical drillpipe as a joint-type tool can improve hole cleaning performance. Under the optimum conditions applied in this study, the hole cleaning efficiency increased by nearly 18%.

Study on Fluidization Characteristics of Magnetically Fluidized Beds for Microfine Particles

The bed pressure drop, minimum fluidized gas velocity, bed density, and bed expansion rate are important parameters characterizing the fluidization characteristics of gas-solid fluidized beds. By analyzing these parameters, the advantages and disadvantages of the fluidization state can be known. In this study, experiments were conducted to study the fluidization characteristics of a gas-solid magnetically fluidized bed for microfine particles by changing the magnetic field strength, magnetic field addition sequence, and static bed height. The experimental results show that when the magnetic field strength increased from 0 KA/m to 5 KA/m, the minimum fluidized gas velocity of particles increased from 4.42 cm/s to 10.32 cm/s, while the bed pressure drop first increased and then decreased. When the magnetic field strength is less than 3.4 KA/m, the microfine particles in the bed are mainly acted on by the airflow; while when the magnetic field strength is greater than 3.4 KA/m, the microfine particles are mainly dominated by the magnetic field. The magnetic field addition sequence affects the fluidization quality of microfine particles. The fluidized bed with ‘adding magnetic field first’ shows a more stable fluidization state than ‘adding magnetic field later’. Increasing of the static bed height reduces the bed expansion rate. The bed expansion rate is up to 112.5% at a static bed height of h0 = 40 mm and H = 5 KA/m. This will broaden the range of density regulation of a single magnetic particle and lay the advantage of gas-solid magnetically fluidized bed for microfine particles in the field of separation of fine coal.

A review on upflow anaerobic sludge blanket reactor: Factors affecting performance, modification of configuration and its derivatives.

The upflow anaerobic sludge blanket (UASB) reactor can be considered as one of the promising anaerobic wastewater treatment technologies suitable for the treatment of high-strength wastewater. In the recent period, researchers have focused on the treatment of low-strength wastewater using this technology. This review focuses on the key factors affecting the reactor performance such as hydraulic retention time (HRT), temperature, organic loading rate (OLR), pH and alkalinity, granulation, wastewater characteristics, mixing, and modification to conventional configuration. Start-up and granulation played a major role in the determination of reactor performance, and various theories have been proposed to understand the mechanism of granulation. Correlation between start-up time and OLR was found to be low, as other operating parameters might have been influencing the start-up time. Flowchart depicting the development of UASB reactor over time is included. In the present work, further development and derivatives of the UASB reactor such as static granular bed reactor (SGBR) and expanded granular sludge bed (EGSB) reactor are analyzed. The optimal conditions for UASB for treating various types of substrates was found to be HRT of 3-24 h, OLR of 1-15 kg COD/m3 /d, and operational temperature in mesophilic range (30-40°C). Analysis of various modifications that pave the way for identification of future areas of research to improve reactor performance is also presented.

Effects of SiO2/Al2O3 Ratio in ZSM-5 Zeolite on the Activity and Selectivity of a Bifunctional Cobalt Catalyst for Synthesis of Low-Pour-Point Diesel Fuels from CO and H2

This study investigates the production of diesel fuels by integrated\t\t\t\t\tFischer–Tropsch synthesis over a bifunctional cobalt catalyst consisting of a\t\t\t\t\tcobalt component\t\t\t\t\t\t(Co–Al2O3/SiO2)\t\t\t\t\tand a zeolite-containing component (ZSM-5). The catalytic properties were tested\t\t\t\t\tin a continuous-flow reactor with a stationary catalyst bed at 240–250°C, 2 MPa,\t\t\t\t\tand gas WHSV 1000 h–1. The effects of the\t\t\t\t\t\tSiO2/Al2O3\t\t\t\t\tratio in a HZSM-5 zeolite on the catalytic performance, catalyst deactivation\t\t\t\t\trate, and hydrocarbon and fractional compositions of the synthetic product were\t\t\t\t\tidentified. The low-temperature properties of the synthesized diesel fuel\t\t\t\t\tsatisfy the current requirements for winter fuels.

CHARACTERIZATION AND UNDERSTANDING OF THERMAL TRANSPORT IN STATIONARY AND MOVING PARTICLE BEDS FOR CONCENTRATING SOLAR POWER

CHARACTERIZATION AND UNDERSTANDING OF THERMAL TRANSPORT IN STATIONARY AND MOVING PARTICLE BEDS FOR CONCENTRATING SOLAR POWER

Long-time-scale transients in an industrial-scale slurry pipeline near the laminar–turbulent transition

We revisit the laminar–turbulent transition of a fine-grained slurry in a large pipe. The combination of long measurement times in an industrial-scale facility and ultrasound imaging allows us to observe and address anomalous trends. Under turbulent conditions, the flow is homogeneous and steady. However, under laminar conditions, two types of long-time-scale transient behaviours are captured. In the first scenario, the system has been homogenized, following which the flow rate is reduced to laminar conditions. The flow rate continues to gradually drop, while particles settle and form a stationary bed. In the second scenario, the system has been shut down for a prolonged period and the flow rate is slowly increased. The flow rate continues to rise while particles are slowly resuspended from the gradually eroding bed. Near the laminar–turbulent transition point, two types of intermittent structures are responsible for resuspension. The equilibrium phase, with steady flow rate, coincides with complete resuspension. These two long-time-scale transients correspond to the phenomena of ‘slow settling’ and ‘self-equilibration’, respectively. While the former can lead to shutdowns, the latter generates a stable system. Being aware of these phenomena is of relevance while operating slurry pipelines near the favourable operating point of the laminar–turbulent transition.