Inverse Fluidization Research Articles

Sorption Kinects and Equilibrium for The Removal of Cadmium and Lead from Aqueous Phase on Rice Husk in Inverse Fluidization Technique

The objectives of this study are to use the inverse fluidization technique to remove heavy metals from wastewater using inexpensive agricultural waste (Rice Husks) and to investigate the effects of operating factors on the dynamic behavior of the adsorption procedure in the inverse fluidized bed, such as the mass of modified rice husks, flow rate (Q), and particle size (dp ). During batch experiments, the best metal ion removal effectiveness was found to be at pH 5, which was discovered after investigating several pH values to achieve this goal. The ideal shaking speed for batch adsorption was 180 rpm. Adsorption efficiency was seen to rise as contact time in the process increased, and the ideal contact time was 3 hours. According to the findings, Cd and Pb had high removal efficiencies from aqueous solutions, 96.83 percent and 91.90%, respectively. Continuous column experiments (inverse fluidized bed) were used to confirm the adsorbent loading capacities for cadmium and lead, which were evaluated by batch research. The proposed adsorbent’s highest adsorption capacity in a batch system was determined to be 7.38 mg/g for Cd and 6.93 mg/g for Pb. Three models-Temkin, Freundlich, and Langmuir-were fitted to a series of equilibrium isothermal tests. The Freundlich isotherm model, with correlation coefficients R2 of 0.98 for Pb and 0.97 for Cd, offered the best fit to the experimental data for this system. The rice husk equilibrium isotherms were determined to be of a favorite kind. To investigate the impact of initial concentrations, bed depth, flow rate, and particle size at a temperature of 30 on the effectiveness of the adsorption process, numerous experiments were conducted in an inverse fluidized bed column. According to the results, rice husk appears to be a material that shows promise for cleaning wastewater of contaminants and toxins.

Mass transfer in inverse fluidized beds

In this work, the coefficient of fluid-wall mass transfer in an inverse fluidized bed was determined using the adsorption method. The experiments were carried out in a column with a diameter of 45 mm with spherical and non-spherical particles of polypropylene and polyethylene with a diameter of 3.3?4.9 mm and a density of about 930 kg m-3. A diluted solution of methylene blue was used as a fluidization medium, which was adsorbed on part of the surface of the column on silica gel. The obtained results showed that the presence of particles during inverse fluidization does not contribute significantly to mass transfer compared to the influence of particles on transfer in conventional fluidized beds. Therefore, the pseudo-fluid concept was introduced into the analysis and an empirical correlation was performed to determine the mass transfer coefficient. The obtained results were compared with literature correlations for inverse and conventional fluidized beds.

Hydrodynamic characteristics of a rectangular gas-driven inverse liquid-solid fluidized bed

The hydrodynamic characteristics of a rectangular gas-driven inverse liquid-solid fluidized bed (GDFB) using particles of different diameters and densities were investigated in detail. Rising gas bubbles cause a liquid upflow in the riser portion, enabling a liquid downflow that causes an inverse fluidization in the downer portion. Four flow regimes (fixed bed regime, initial fluidization regime, complete fluidization regime, and circulating fluidization regime) and three transition gas velocities (initial fluidization gas velocity, minimum fluidization gas velocity, and circulating fluidization gas velocity) were identified via visual observation and by monitoring the variations in the pressure drop. The axial local bed voidage (ε) of the downer first decreases and then increases with the increase of the gas velocity. Both the liquid circulation velocity and the average particle velocity inside the downer increase with the increase of the gas velocity in the riser, but decrease with the particle loading. An empirical formula was proposed to successfully predict the Richardson-Zaki index “n”, and the predicted ε obtained from this formula has a ±5% relative error when compared with the experimental ε.

Effectiveness of Algae in Wastewater Treatment Systems

Abstract: Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) play important role in determining the quality of wastewater. Hence it is necessary to calculate COD and BOD of water before setting up of wastewater treatment plant. Algae has been used for decades for various purposes. It is one of the important characteristics is to nitrogen, phosphorus etc., which are harmful for drinking and other purposes but they act as food for algae. Thus in this study COD and BOD analysis is done for sterilized and non-sterilized wastewater after and before treating it with algae in inverse fluidization under aerobic condition, for different time interval and found that percentage reduction in COD and BOD for sterilized wastewater gives greater value than non-sterilized water the reason for this difference being the decrease in the competition between algae and other micro-organism which are present in raw wastewater and COD % reduction is 65-70 % and BOD % reduction is 68.75- 70.5%.Organic and inorganic substances which are released into the environment as a result of domestic, agricultural and industrial water activities lead to pollution.

Hydrodynamics of a gas‐driven inverse liquid‐solid fluidized bed

AbstractA novel reactor named gas‐driven inverse liquid‐solid fluidized bed (GDFB) was developed in this research. It adopts gas as the driving force to benefit chemical processes requiring minimum liquid flow. The column is divided into a riser section for upward gas flow and a downer section as the main fluidized bed for light particles. The inverse fluidization occurs in the downer, where hydrodynamics and their influencing factors were studied. In the solid‐baffle system, four fluidization regimes were observed, including the packed bed, semi‐fluidized bed, fully‐fluidized bed, and circulating bed. Moreover, the meshed‐baffle system possesses some distinct characteristics, and the shifted bed regime was found between the fully‐fluidized bed and the circulating bed.

An Experimental Investigation of Synergistic Pulsation Bubble Column with Inverse Fluidized Loop Reactor for Removing Chloroform from Wastewater

In this study, the feasibility of using the developed design for the removal of organic pollutants from wastewater was examined. The design includes the integration of the work of both pulsation bubble column (PBC) and the inverse fluidization airlift loop reactor (IFALR). The experimental podium was fabricated and installed which that consists of a bubble column with a diameter of 5 cm and a height of 210 cm, contains at the top a solenoid valve which is electrically turned via at least two timers, and its connection with the loop reactor by a one-way valve. The loop reactor consists of an outer rectangular tube with dimensions (29 cm long x 15.5 cm wide x 150 cm high) and an internal draft tube with 9 cm diameter and 120 cm long as granular activated carbon is put as an adsorbent in the annulus region between the inner and outer tube. Experiments were conducted using one of the organic pollutants namely chloroform, with a work scenario that includes changing both the airflow rate (2-20) liters/minute, the total survival time of the treatment (5-60) minutes, the molar ratio of the chloroform pollutant to the oxidizing agent of hydrogen peroxide (1/10 - 1/20). The results showed removal efficiency near to 89%, and it gives an indication of the success of the proposed design, with the possibility of recycling the treated water and releasing it to the environment due to the low risk of the organic pollutant in it.

Phenol removal using pulsation bubble column with inverse fluidization airlift loop reactor

Phenol and phenolic compounds are omnipresent organic contaminants which are sent out to water bodies and wastewater systems produced from industrial processes, and they require specific attention due to their extraordinary features such as high toxicity, carcinogenic characteristics, and ability to accumulate, which affects the health of humans and the environment. In this practical study, the integrated system of a pulsation bubble column with an inverse fluidization air loop reactor was tested to remove phenol. The test platform was made and operated with a bubble column containing at its upper end an electrical solenoid valve engaged via at least two timers, and connected to the air loop reactor consisting of an outer rectangular tube and an internal draft tube by one-way valve, where the granular activated carbon is put as an adsorbent material in the annulus region between the inner and outer tube. The effects of various parameters [molar ratio of Phenol to H2O2 (1/10, 1/15 and 1/20), airflow rate (5-20 L/min), remediation time (5-60 min), initial phenol concentration (10- 150 mg L-1) have been studied. Removing 90% of the contaminated phenol as a result of this study may represent a partial solution to the ecological problem.

A review on hydrodynamic parameters and biofilm characteristics of inverse fluidized bed bioreactors for treating industrial wastewater

Abstract Wastewater treatment processes play crucial role in keeping the human health and environment at proper hygiene. Currently, biological wastewater treatment methods are dominant in the effluent treatment process because of their cost-effectiveness in the treatment. However, the rapid increase in population has created a need for the implementation of highly efficient wastewater treatment methods. In the recent past, the treatment of wastewater through fluidized-bed bioreactor has proven as one of the best processes from the currently available methods of chemical and biochemical engineering fields. This review aims to explore and compile the methods of fluidization used for the treatment of wastewater in the recent past, majorly by the inverse fluidization method. In the inverse fluidization process, the density of solid particles utilized in the fluidization is lower than that of the liquid and compared to an up-flow fluidized bed bioreactor, and it is a very effective system for biological wastewater treatment. This review discusses the developments made in recent years with regard to aerobic inverse fluidized bed bioreactors, with more emphasis placed on the reported applications on treating industrial wastewaters. The influence of hydrodynamic parameters (minimum fluidization velocity, phase holdup, bed expansion, and bed height, pressure drop, superficial gas velocity, liquid velocity, hydraulic retention time, biofilm carriers and ratio of volume of settled bed to the volume of reactor) are highlighted in the discussion, and also the effect of these parameters on the biofilm and its subsequent effect on wastewater is included. Recent trends of application of aerobic inverse fluidized bed bioreactors for the removal of COD and scope of future study elements have been discussed in this manuscript.

Biosorption of Cationic Dyes onto Cork Stopper Particles by Inverse Fluidized Bed

In this study cork stopper particles was used as a low cost biosorbent to remove the cationic dyes (Methylene blue (MB), Malachite green (MG), and Methyl violet (MV)) from simulated wastewater. Continuous experiments were studied in a laboratory scale in inverse fluidized-bed packed with cork stopper particles for removal these dyes. A set of continuous mode experiments was carried out in inverse fluidized bed column to study the effect of flow rate (10, 15, 20 l/h), bed depth (5, 10, 15 cm), and influent concentration (10, 20, 30 mg/l) on the performance of biosorption process onto cork stopper particles. The minimum inverse fluidized velocity was calculated and it was found to be 8 ×10-5 m/s. The results indicate that cork adsorbs dyes efficiently and can be used as a low-cost alternative for the removal of cationic dyes in wastewater treatment.

Treatment of the oilfield-produced water and oil refinery wastewater by using inverse fluidization - A review

<p>Oilfield wastewater or produced water is a complex mixture contains oil, organic and inorganic matter and other compounds dissolved in water that ranges from fresh to brine. Discharging produced water pollute soil surface and underground water and create environment hassle. The objective of this study is to investigate and summarize the novel method of fluidization processes, used for the treatment of oilfield produced water and oil refinery wastewater. Characteristics of oilfield produced water and oil refinery wastewater from different field and various methods for treating these wastewaters are discussed. Oilfield produced water and oil refinery wastewater are strongly acidic (pH 3-4), have a high chemical oxygen demand (1200-2600 mg/L), high polyphenol content (23 mg/L) and are highly variable. Primary attention is focused on the fluidization treatment of oilfield produced water and oil refinery wastewater, mainly by inverse fluidization. Finally, areas where further research and attention are required are identified.</p>

Numerical simulation of the hydrodynamics of an inverse liquid–solid fluidized bed using combined Lattice Boltzmann and smoothed profile methods

ABSTRACTKnowledge of an inverse fluidized-bed fluid hydrodynamics is advantageous in optimal adjustment and designing high-efficiency beds. In the present study, a combination of a single relaxation time collision operator lattice Boltzmann method (LBM) and the smoothed profile method (SPM) is employed to simulate the hydrodynamics of an inverse liquid–solid fluidized bed comprising circular monodisperse and polydisperse particles in a rectangular channel. A numerical instance of inverse fluidization involving 231 particles is illustrated to show the capability of the combined methods. Moreover, comparison of the numerical results is performed with the Ergun equation and the Richardson–Zaki correlation. The comparison demonstrates that the present model can simulate the fluid flow behavior in an inverse fluidized bed. Several different models were also presented to investigate the effect of different fluid properties and size of particles in the bed. Simulations indicate that the more the superficial liquid velocity, the higher the porosity of the bed. The present simulations show that porosity of the bed increases by increasing the particles size, and also the vertical velocity of the bed decreases with an increase in liquid viscosity. Finally, polydisperse particle systems are also simulated. The results show that porosity in an inverse fluidized bed comprising polydisperse particles is more than that of a monodisperse particle bed.

Process development and intensification for enhanced production of Bacillus lipopeptides

The growing interest in Bacillus lipopeptides for high-value applications has driven process design, development and optimization for enhanced lipopeptide production. Traditional optimization approaches have been directed towards improving the overall titres by modification of media components and environmental parameters, almost exclusively in submerged cultures. Carbon and nitrogen sources, trace elements and oxygen availability have all been demonstrated to exhibit significant influences on lipopeptide yield, productivity and selectivity. This insight into process-linked kinetics, especially selectivity, has led to the introduction of novel process intensification and integration strategies which further promote process efficiency, and which include foam fractionation, inverse fluidization, rotating disc contacting and microfiltration with recycle. These strategies have not only transformed the production capabilities, but have also successfully integrated upstream production with downstream purification through cell retention and in situ product removal. This review analyses and critically discusses the impact of process conditions and process optimization strategies for improving lipopeptide production kinetics, specifically highlighting the emerging trend of process intensification and integration strategies and further, proposes a heuristic route to enhance lipopeptide production.

Holdup prediction in inverse fluidization using non-Newtonian pseudoplastic liquids: Empirical correlation and ANN modeling

The bed expansion characteristics in inverse fluidization using non-Newtonian liquids are reported. Experiments have been carried out using single and binary systems of four different polymeric solids and four different non-Newtonian pseudoplastic liquids in two different columns. Empirical correlation has been developed to determine the bed expansion characteristics as a function of physical and dynamic variables of the system. A multilayer perceptron trained with backpropagation and Levenberg–Marquardt algorithm have been used for the Artificial Neural Network (ANN) analysis. Four different standard transfer functions in a single hidden layer are used. The ANN model with Levenberg–Marquardt algorithm with transfer function 2 having 12 processing elements in hidden layer gives good predictability of the bed height. Statistical analysis indicates that both the empirical correlation and the ANN prediction give acceptable results.

Study the Performance of Low Cost Material (Peanut Hulls) for Dye Adsorption Using Inverse Fluidized Bed

The present study dealt with the removal of methylene blue from wastewater by using peanut hulls (PNH) as adsorbent. Two modes of operation were used in the present work, batch mode and inverse fluidized bed mode. In batch experiment, the effect of peanut hulls doses 2, 4, 8, 12 and 16 g, with constant initial pH =5.6, concentration 20 mg/L and particle size 2-3.35 mm were studied. The results showed that the percent removal of methylene blue increased with the increase of peanut hulls dose. Batch kinetics experiments showed that equilibrium time was about 3 hours, isotherm models (Langmuir and Freundlich) were used to correlate these results. The results showed that the (Freundlich) model gave the best fitting for adsorption capacity. Different size ranges of peanut hulls (PNH) were fluidized by a downward flow of an methylene blue dye dissolved in water in an inverse fluidization mode. In the inverse fluidized bed experiments, the hydrodynamics characteristics, the effect of initial methylene blue concentration Co 5, 10 and 20 mg/L, particle size 1.18-2, 2-3.35 and 3.35-4 mm, mass of adsorbent 25, 60 and 80 g, superficial fluid velocity 0.016, 0.019 and 0.027 m/s and effect of chemical modification were studied. The optimum conditions of adsorption in inverse fluidized bed were initial concentration was 5 mg/L, particle size was 1.18-2 mm size, mass of PNH is 80 g and superficial fluid velocity was 0.019 m/s. Also the adsorption capacity of PNH increased after modification by Nitric acid. UV-Spectrophotometer was used to determine the methylene blue concentration.

Fluid bed porosity mathematical model for an inverse fluidized bed bioreactor with particles growing biofilm

A new mathematic model to estimate bed porosity as a function of Reynolds and Archimedes numbers was developed based in experimental data. Experiments were performed using an inverse fluidized bed bioreactor filled with polypropylene particles, Lactobacillus acidophillus as the immobilized strain and fluidized with a Man-Rogosa-Sharpe culture medium under controlled temperature and pH conditions. Bed porosity was measured at different flow rates, starting from 0.95 to 9.5 LPM. The new model has several advantages when compared with previously reported. Among them, advantages such as standard deviation values ≤ 1% between experimental and calculated bed porosity, its applicability in traditional and inverse fluidization, wall effects do not take account, it gives excellent agreement with spherical particles with or without biofilm, and inertial drag coefficient allow extend the new model a non-spherical particles.

Optimal Aerations in the Inverse Fluidized Bed Biofilm Reactor When Used in Treatment of Industrial Wastewaters of Various Strength

The aim of this work was the determination of the optimal aerations, and more specifically the corresponding optimal air velocities uopt, at which the largest COD removals were achieved in treatment of industrial wastewaters of various strength conducted in the inverse fluidized bed biofilm reactor. The largest COD removals were achieved at the following air velocities uopt and retention times ts, and (Vb/VR) = 0.55: i) for CODo = 72,780 mg/l at uopt = 0.052 m/s and ts = 80 h ; ii) for CODo = 62,070 mg/l at uopt = 0.042 m/s and ts = 65 h; iii) for CODo = 49,130 mg/l at uopt = 0.033 m/s and ts= 55 h ; iv) for CODo = 41,170 mg/l at uopt = 0.028 m/s and ts = 45 h; v) for CODo = 35,460 mg/l at uopt = 0.025 m/s and ts = 27.5 h; and vi) for CODo = 26,470 mg/l at uopt= 0.014 m/s and ts = 22.5 h. In the treatment operation conducted in a reactor optimally controlled at the above values of uopt, ts and (Vb/VR), the following decreases in COD were obtained: i) from 72,780 to 5410 mg/l; ii) from 62,070 to 3730 mg/l; iii) from 49,130 to 2820 mg/l; iv) from 41,170 to 1820 mg/l; v) from 35,460 to 1600 mg/l; and vi) from 26,470 to 1180 mg/l, that is, approximately a 93%, 94%, 95%, 96%, 95% and 96% COD reduction was attained, respectively.

Evaluation of the Inverse Fluidized Bed Biological Reactor for Treating High-Strength Industrial Wastewaters

The aim of this work was to investigate the aerobic degradation of high-strength industrial (refinery) wastewaters in the inverse fluidized bed biological reactor, in which polypropylene particles of density 910 kg/m3 were fluidized by an upward flow of gas through a bed. Measurements of chemical oxygen demand (COD) versus residence time t were performed for various ratios of settled bed volume to reactor volume (Vb/VR) and air velocities u. The largest COD reduction, namely, from 54,840 to 2,190 mg/l, i.e. a 96% COD decrease, was achieved when the reactor was operated at the ratio (Vb/VR) = 0.55, air velocity u = 0.046 m/s and t = 65 h. Thus, these values of (Vb/VR), u and t can be considered as the optimal operating parameters for a reactor when used in treatment of high-strength refinery wastewaters. In the treatment operation conducted in a reactor optimally controlled at (Vb/VR) = 0.55, u = 0.046 m/s and t = 65 h, the conversions obtained for all phenolic constituents of the wastewater were larger than 95%. The conversions of about 90% were attained for other hydrocarbons.

Inverse fluidization using non-Newtonian liquids

Experiments have been carried out to determine the minimum inverse fluidization velocity using single and binary systems of four different solids of polymeric origin, and four different non-Newtonian liquids in two different columns. Empirical correlations have been developed to predict the minimum inverse fluidization velocity as a function of physical and dynamic variables of the system. Statistical analysis of the correlation suggests that is of acceptable accuracy with correlation coefficient more than 0.99.

Stratification pattern in inverse binary–solid liquid–fluidized beds

The inverse fluidization of unequal solid species of a binary-pair leads to the occurrence of their stratification along the height of the bed. This phenomenon depends upon the difference in the physical properties and the relative composition of the individual species comprising the binary-pair besides the fluid velocity. Packing models are used here to account for the observed volume-contraction owing to the mixing of unequal solid species. In view of stability considerations, the minimum bulk density condition is used to predict the composition of the upper-layer located below the distributor. Predictions are consistent with the observed stratification pattern reported in the literature.

Removal of emulsified oil from water by inverse fluidization of hydrophobic aerogels

Different size ranges of surface-treated hydrophobic silica aerogels (Nanogel ®) provided by Cabot Corporation are fluidized by a downward flow of an oil-in-water emulsion in an inverse fluidization mode. Surface areas, pore size distributions, and pore diameters are investigated by using BET and contact angle is measured by a goniometer. The hydrodynamics characteristics of the Nanogel granules of different size ranges are studied by measuring the pressure drop and bed expansion as a function of superficial water velocity. The density of the Nanogel granules is calculated from the plateau pressure drop after the bed is fully fluidized. The oil removal efficiency of a dilute (1000 ppm COD or lower), stabilized (using the emulsifier Tween 80) oil-in-water emulsion and the capacity of the Nanogel granules in the inverse fluidized bed are also studied. A model was developed to predict the inverse fluidized bed experimental results based on equilibrium and kinetic batch measurements of the Nanogel granules and the stabilized oil-in-water emulsion. The results show that the major factors which affect the oil removal efficiency and capacity are the size of the nanogel granules, bed height, fluid superficial velocity and the proportion of emulsifier in the oil-in-water emulsion. The Nanogel particles can absorb as much as 2.8 times their weight of oil by the inverse fluidization process.