Jet Loop Reactor Research Articles

Comparison of k–ε, RSM and LES models for the prediction of flow pattern in jet loop reactor

Jet loop reactors (JLR) are frequently employed in the process industry as an alternative to impeller mixers due to the existence of relatively intense convective flow leading to enhanced rate of macro-mixing at the same power consumption. In JLR, close to the nozzle, high shear zone is present and most of the turbulence models fail to predict the jet spreading. As a consequence, the bulk motion (outside the jet region) does not get appropriately described. It may be pointed out, that the bulk region occupies a major portion of the reactor and houses the processes of mixing and chemical reaction.In the present work, CFD simulations have been undertaken by using standard k–ε, RSM and LES turbulence models. It is known that the computationally cheaper models such as k–ε and Reynolds stress model (RSM) have many simplifying assumptions which limit their accuracy. In order to compare the turbulence models, the LES results have been used to evaluate the exact terms in turbulent kinetic energy (k) and turbulent kinetic energy dissipation (ε) transport equations in standard k–ε model and RSM. From the Large eddy simulation (LES) simulations, the time series of velocity and pressure were stored and were subsequently used for the detailed estimations of two terms. The conservation equations for k and ε consist of convective transport, diffusive transport, dispersive transport, production and dissipation. In the following paper, each of these terms has been quantified accurately in the exact form (i.e. without any assumption) and in the modeled form. This has enabled the direct comparison between the two and has given a clear insight into each modeling assumption.

Optimization of anaerobic co-digestion of olive mill wastewater and liquid poultry manure in batch condition and semi-continuous jet-loop reactor

Anaerobic co-digestion of olive mill wastewater (OMW) with liquid poultry manure (LPM) was investigated in a jet-loop reactor (JLR) as a new approach for upgrading the efficiency of bioprocess. Optimum proportion of LPM was evaluated by determining biochemical methane potential. Methane yields were compared by applying one way ANOVA method followed by post hoc Tukey’s test with a 0.05 significance level. Results demonstrated that the addition of LPM at proportion of 10% and 30% (v/v) improved methane yield of OMW digestion but differences between these mixtures and raw OMW are not significant. JLR results confirmed that the proportion 30% LPM gives the optimum condition for excellent stability of digester. Methane production was significantly high until an organic loading rate of 9.5gCOD/Lreactor/day. Overall; this study indicates the technical feasibility and effectiveness of using JLR as one-stage anaerobic system for the co-digestion of OMW and LPM.

Intensified hydroformylation as an example for flexible intermediates production

One of the future challenges for chemical engineering is the design of flexible plants allowing an adaptation of production output to market development. Consequently, the target for the design of new processes must be the identification of equipment allowing such an expansion close to market development. To leverage the full benefit of this approach flexibility analysis has to be integrated into process design workflow. In this article the conventional technology for hydroformylation is compared to an intensified process design. This new design consists of a jet loop reactor followed by a membrane section to separate and recycle the homogenous catalyst. In the first part of the article it will be shown that process intensification leads to a net present value improvement of 30% compared to state of the art hydroformylation at a capacity of 100kt/a. In the second part suitability of the intensified process for a stepwise plant expansion will be demonstrated. In an expansion scenario with two steps equivalent annual annuity is increased by 5% compared to a one step investment.

CO2 absorption characteristics of a jet loop reactor with a two-fluid swirl nozzle in an alkaline solution

To investigate the performance of a jet loop reactor with the two-fluid swirl nozzle (TSN), CO2 absorption experiments in an alkaline solution were performed. The experimental results obtained in the reactor were compared with those in a jet loop reactor with the two-fluid conventional nozzle (TCN). The neutralization time of alkaline solution and the CO2 removal efficiency were used as the indices for a comparison of the reactor performance. Due to the swirling flow, the neutralization times of alkaline solutions by CO2 in the reactor with the TSN were shortened compared with those in the reactor with the TCN. Also, the instantaneous and/or overall CO2 removal efficiencies in the reactor with the TSN were higher than those in the reactor with the TCN at the same liquid circulation flow rate.

Kinetics of cyclooctene hydroformylation for continuous homogeneous catalysis

The kinetics of Rh-catalysed cyclooctene hydroformylation were investigated, based on the mechanism described for a single tris(2,4-di-tert-butylphenyl)phosphite ligand coordinated to a rhodium center. The rate limiting step was found to be the coordination of cyclooctene to the metal center as suggested in literature. Parameters of the corresponding rate equation were estimated by nonlinear regression. Experimental data obtained from semi-batch reactions were compared with model predictions and shown to be in good agreement. A continuous jet-loop reactor with coupled nanofiltration was designed and the kinetics were validated.

Jet loop reactor application for mine water treatment using fly ash, lime and aluminium hydroxide

Recent studies have shown that a combination of coal fly ash (FA) and Al(OH)3 can be used to treat neutral mine drainage (NMD) and reduce sulphate concentration to within South African drinking water quality levels, Class II (400–600 mg/L). The shortcomings of this method were the large amounts of FA required to raise the pH to greater than 11 (3:1 liquid-to-solid ratio) so that Al(OH)3 can be added to facilitate removal of sulphate ions through ettringite precipitation. This requires large silos to store FA, making up-scaling of this treatment technology using normal mixing methods to be unrealistic. In the current study, a jet loop reactor was used to reduce the amount of FA needed to increase the pH to greater than 11. The pH was raised to greater than 11 by mixing 0.25 % of lime (w/v ratio) and 13 kg of coal FA with 80 L of NMD in a jet loop reactor. After the pH of the mixture was above 11, amorphous Al(OH)3 (83.2 g) was added to the mixture. This resulted in the sulphate concentration decreasing to less than 500 mg/L. Bench-scale studies using 0.25 % (w/v) of lime and 6:1 coal mine water to FA ratio could not reduce the sulphate concentration to below 500 mg/L. Therefore, the impingement and cavitation mixing techniques that happen in a jet loop reactor played an important role in enhancing sulphate removal.

Semi-batch Jet Loop Reactor에서 연소 배가스중 CO<sub>2</sub>를 이용한 알칼리 폐수 중화

In this study, we tested the absorption of <TEX>$CO_2$</TEX> in combustion gas into an alkaline wastewater to simultaneously control <TEX>$CO_2$</TEX> and wastewater. During the experiment, we investigated the effects of operating parameters on neutralization characteristics of the wastewater by using <TEX>$CO_2$</TEX> in a bench-scale semi-batch jet loop reactor (0.1 m diameter and 1.0 m in height). The operating parameters investigated in the study are gas flow rate of 1.0-2.0 L/min, liquid recirculation flow rate of 4-32 L/min, and liquid temperature of <TEX>$20-25^{\circ}C$</TEX>. It was shown that the initial pH of wastewater rapidly decreased with increased gas flow rate for a given liquid recirculation flow rate. This was due to the increase in the gas holdup and the interfacial area at higher gas flow rate in the reactor. At constant gas flow rate, the time required to neutralize the wastewater initial pH of 10.1 decreased with liquid recirculation flow rate (<TEX>$Q_L$</TEX>), reached a minimum value in the range of <TEX>$Q_L$</TEX> = 16-24 L/min, and then increased with further increase in <TEX>$Q_L$</TEX>. Further, the time required to neutralize the wastewater was shortened at higher temperatures.

Semi-batch Jet Loop Reactor에서 연소 배가스중 CO&lt;sub&gt;2&lt;/sub&gt;를 이용한 알칼리 폐수 중화

In this study, we tested the absorption of in combustion gas into an alkaline wastewater to simultaneously control and wastewater. During the experiment, we investigated the effects of operating parameters on neutralization characteristics of the wastewater by using in a bench-scale semi-batch jet loop reactor (0.1 m diameter and 1.0 m in height). The operating parameters investigated in the study are gas flow rate of 1.0-2.0 L/min, liquid recirculation flow rate of 4-32 L/min, and liquid temperature of . It was shown that the initial pH of wastewater rapidly decreased with increased gas flow rate for a given liquid recirculation flow rate. This was due to the increase in the gas holdup and the interfacial area at higher gas flow rate in the reactor. At constant gas flow rate, the time required to neutralize the wastewater initial pH of 10.1 decreased with liquid recirculation flow rate (), reached a minimum value in the range of

Removal of heavy metals from aqueous solutions by liquid cation exchanger in a jet loop contactor

The paper focuses on the use of naphthenic acid as a low cost ion exchanger for removing heavy metal ions from aqueous solutions. Extraction of Cu++ from dilute aqueous solutions by naphthenic acid dissolved in kerosene in a simple jet loop reactor was studied. Variables studied were; circulation velocity, initial Cu++ concentration, nozzle diameter and nozzle height (the vertical distance between nozzle and the surface of the liquid in the reactor). An increase in the rate of extraction was observed with increasing nozzle diameter and circulation velocity. Increasing initial metal ion concentration and the nozzle height was found to decrease the rate of extraction. The rate of extraction was expressed in terms of the volumetric mass transfer coefficient (kA), the data were correlated by the dimensionless equation:Shm=0.044Sc0.33Re1.54Ldn−0.36The possibility of using the present reactor for removing heavy metals such as removal of copper from printed circuit etching solution, pickling solutions, electroplating and electroless plating rinse solution and copper mines drainage solutions was highlighted.

Removal of selected chlorinated micropollutants by ozonation

AbstractFeasibility of ozone oxidation for the elimination of selected dissolved organic micropollutants from water and wastewaters was studied. Five organochlorine pesticides, i.e. hexachlorobutadiene, pentachlorobenzene, hexachlorobenzene, lindane, and heptachlor, were used as organic contaminants of model water. The first four of them are classified as priority hazardous substances. The oxidation treatment process was performed in a jet loop reactor. Ozone was prepared from pure oxygen. Quantification of the organochlorine pesticides in water was achieved by the gas chromatographic method after liquid-liquid extraction. Significant contribution of stripping to the removal of the investigated compounds during the ozonation treatment was also proven by the results. Effective ozonation time with regard to treatment efficiencies was 30 min, which corresponds to the ozone input of 317 mg per liter of active volume of the ozonation reactor. Single power law kinetic models were used to describe experimental data and kinetic parameters were estimated. The best fit of the experimental degradation data of all studied pollutants was obtained by the second order kinetic model. It can be concluded, based on the results obtained, that the applied ozonation process is a promising procedure for the removal of the investigated pesticides from aquatic environment.

Measurements of Flow Hydrodynamics in a Jet-Loop Reactor Using Piv Method

Abstract The aim of this work was determining optimal parameters of the investigated jet-loop reactor by means of the built by authors low cost PIV system. The criterion of optimization was value of flow rate in a draft tube. It was found that flow rate in the draft tube increases with the increase of flow rate in the supplying nozzle, what is caused by increase of outlet velocity of supplying liquid stream. With increase of distance between the nozzle and the upper edge of the draft tube the diameter of the stream with high velocity increases, what causes growth of flow rate of liquid at the outlet. Long draft tube causes disturbance of flow, backward circulation and decrease of flow rate, because of decrease of distance from its lower edge to the bottom of the reactor. As a result, the liquid circulation may be stopped. Liquid circulation is more intensive in wider draft tubes, wider than diameter of flowing out stream. In the case of a narrow draft tube the liquid stream flowing out of the nozzle may flow outside the draft tube wall disturbing circulation.

MLVSS에 따른 Jet Loop Reactor (JLR)에서 동력량과 공기량이 산소전달률에 미치는 영향

Abstract : Oxygen transfer rate generally determines the performance of an aerobic wastewater treatment process that treats high strength wastewater such as food wastewater, animal wastewater and landfill leachate. In this paper, OUR and K L ･a were evaluated by using Jet Loop Reactor (JLR) according to the concentration of a mixed liquor volatile suspended solid (MLVSS), oxygen (air) flow rate and energy input as the variable of the operating conditions. Also, a nonlinear regression model was proposed by the statistical methods with the calculated K L ･a. As a results, in case of applying the high strength wastewater which has to maintain high MLVSS, the energy input and the air flow rate are major parameters oxygen transfer rate in JLR. Finally, the final nonlinear regression model had been developed as a function of E/V, Q g , and µ c . Key Words : Jet Loop Reactor (JLR), Oxygen Transfer Rate, Volumetric Mass Transfer Coefficient (K L ･ a) 요약: 산소전달률은 음폐수, 축산폐수 그리고 매립지 침출수와 같은 고농도 폐수처리를 호기성 공정으로 처리할 시 그 성과를 결정하는 아주 중요한 요소이다. 본 논문에서는, Jet Loop Reactor (JLR)를 이용하여 공기유량과 동력량을 운전조건의 변수로 두고 미생물의 농도에 따른 산소소비율(Oxygen uptake rate, OUR)과 물질전달계수(Volumetric mass transfer coefficient, K

Ammonia removal by air stripping in a semi-batch jet loop reactor

Ammonia is very toxic chemical and it can be removed by air stripping at high pH. JLRs have found applications in wastewater treatment processes due to their high mass transfer rates. In JLRs, intrinsic high turbulence result in a very large air-liquid surface area for greater mass transfer. Therefore, in this study, ammonia removal by air stripping from synthetically prepared ammonia solution at the high pH in a semi-batch JLR due to its high mass transfer capabilities have been investigated. Investigated parameters in a JLR were initial ammonia concentration (10–500 mg/L), temperature (20–50 °C), air flow rate (5–50 L/min) and liquid circulation rate (35–50 L/min). While it was demonstrated that temperature and air flow rate have a significant effect on the ammonia removal, it was determined that initial ammonia concentration and liquid circulation rate have no significant effect on the ammonia removal. The overall volumetric mass transfer coefficients ( K L a) have been calculated from obtained model and it was determined that increasing temperature and air flow rate have a very significant effect on K L a. It was concluded that JLR provides higher mass transfer capabilities than other type of reactors even if less air is given.

The investigation of dairy industry wastewater treatment in a biological high performance membrane system

The dairy industry is generally considered to be the largest source of food processing wastewater in many countries. The highly variable nature of dairy wastewaters in terms of volumes and flowrates and in terms of high organic materials contents such as COD 921–9004 mg L −1, BOD 483–6080 mg L −1, TN of 8–230 mg L −1 and SS of 134–804 mg L −1 makes the choice of an effective wastewater treatment regime difficult. A high performance bioreactor, an aerobic jet loop reactor, combined with a ceramic membrane filtration unit, was used to investigate its suitability for the treatment of the dairy processing wastewater. The oxygen transfer rates of the bioreactor were found to be very high (100–285 h −1) on the operating conditions. A loading rate of 53 kg COD m −3 d −1 resulted in 97–98% COD removal efficiencies under 3 h hydraulic retention time. The high MLSS concentrations could be retained in the system (up to 38,000 mg L −1) with the contribution of UF (ultrafiltration) unit. During the filtration of activated sludge, the fluxes decreased with increasing MLSS. Cake formation fouling was determined as dominant fouling mechanisms. The results demonstrate that jet loop membrane bioreactor system was a suitable and effective treatment choice for treating dairy industry wastewater.

Molecular assessment of microbiota structure and dynamics along mixed olive oil and winery wastewaters biotreatment

The major parcel of the degradation occurring along wastewater biotreatments is performed either by the native microbiota or by added microbial inocula. The main aim of this study was to apply two fingerprinting methods, temperature gradient gel electrophoresis (TGGE) and length heterogeneity-PCR (LH-PCR) analysis of 16S rRNA gene fragments, in order to assess the microbiota structure and dynamics during mixed olive oil and winery wastewaters aerobic biotreatment performed in a jet-loop reactor (JLR). Sequence homology analysis showed the presence of bacterial genera Gluconacetobacter, Klebsiella, Lactobacillus, Novosphingobium, Pseudomonas, Prevotella, Ralstonia, Sphingobium and Sphingomonas affiliated with five main phylogenetic groups: alpha-, beta- and gamma-Proteobacteria, Firmicutes and Bacteroidetes. LH-PCR analysis distinguished eight predominant DNA fragments correlated with the samples showing highest performance (COD removal rates of 67 up to 75%). Cluster analysis of both TGGE and LH-PCR fingerprinting profiles established five main clusters, with similarity coefficients higher than 79% (TGGE) and 62% (LH-PCR), and related with hydraulic retention time, indicating that this was the main factor responsible for the shifts in the microbiota structure. Canonical correspondence analysis revealed that changes observed on temperature and O(2) level were also responsible for shifts in microbiota composition. Community level metabolic profile analysis was used to test metabolic activities in samples. Integrated data revealed that the microbiota structure corresponds to bacterial groups with high degradative potential and good suitability for this type of effluents biotreatments.

Gas holdup in a two‐phase reversed flow jet loop reactor

AbstractExperimental investigations have been carried out in Reversed Flow Jet Loop Reactor (RFJLR) to study the influence of liquid flow rate, gas flow rate, immersion height of two‐fluid nozzle in reactor and nozzle diameter on gas holdup without circulation, that is, gas–liquid mixture in draft tube only (Egd) and gas holdup with circulation loop (Eg). Also critical liquid flow rate required for transition from draft tube to circulation loop has been determined. Gas holdup was measured by isolation valve technique. Gas holdup in draft tube and circulation loop increased with increase in liquid flow rate and gas flow rate. It is observed that the increased flow rate is required for achieving a particular value of gas holdup with larger nozzle diameter. Nozzle at the top edge of draft tube have higher gas holdup as compared to other positions. It has been noted that, no significant recirculation of gas bubbles into the top of draft tube from annulus section has been observed till a particular liquid flow rate is reached. A plot of gas holdup with no circulation and with circulation mode determines minimum liquid flow rate required to achieve complete circulation loop. Critical liquid flow rate required to achieve complete circulation loop increases with increase in gas flow rate and is minimum at lowest immersion height of two‐fluid nozzle.

Characterization of gas-liquid parameters in a down-flow jet loop bubble column

In order to characterize the gas-liquid parameters of a down-flow jet loop reactor, experiments were carried out to study the gas holdup, bubble sizes and their distribution, mass transfer area and mass transfer coefficient. The experiments were performed in the bubbly flow regime because of its stability and uniformity. Analysis of experimental data showed an unambiguous relationship between gas holdup, bubble size, bubble size distribution and interfacial area. It has also been found that gas holdup and interfacial area is a strong function of slip velocity. The variation of interfacial area and mass transfer coefficient were also analyzed and expressed as a function of operational and geometric parameters.

Investigation of the local specific energy dissipation rates in a jet‐zone loop reactor for halogenation of ketones

AbstractWithin the framework of process intensification there is a growing demand for novel reactor technologies. For the improvement of halogenation of ketones a jet‐zone loop reactor (JZR) is used, which leads to an enormous increase in yield and selectivity compared to stirred vessels (Kutschera et al., 2008). This JZR is a special jet loop reactor with high specific mass transfer performance and good macromixing behaviour. It is obvious that there is direct relation between the reaction and the hydrodynamics in the reactor. Despite several aspects of hydrodynamics in jet loop reactors have been investigated, the essential flow characteristics behind a two‐component jet are not sufficiently understood. In these investigations, the flow field in the jet zone of the JZR was analysed by 2D particle image velocimetry (PIV) and the kinetic energy dissipation rate ε was determined from the spatial gradients of the fluctuating velocity.

Analysis of flow structures and energy spectra in chemical process equipment

Studies have been carried out to extract relevant information on flow structures, their break-up distribution and the associated local turbulence phenomena using the 1D and 2D energy spectra. The 1D analysis uses the hot film anemometry (HFA) and large eddy simulation (LES) data sets, while the 2D analysis uses the PIV results. The chemical process equipment considered for the study are jet loop reactor (JLR), channel flow (CHA) and bubble column reactor (BCR). The work involves relative comparison of spectral methods, namely, fast Fourier transform (FFT), discrete wavelet transform (DWT), continuous wavelet transform (CWT), eddy isolation methodology (EIM) and proper orthogonal decomposition (POD) in evaluating the 1D and 2D spectra for the three equipment. FFT studies are used to identify the dominant frequencies, but they do not reveal the time dependent changes in the flow structure. This limitation is overcome by using the EIM, DWT and CWT and methodologies for identification of flow structures are discussed. Using DWT, a novel intermittency-based quantifier, namely, the scale relative local intermittency measure (SRLIM) is found to be particularly useful for identification of intermittent flow structures. For example, it has been used to track the intermittent bursts in the CHA, the vortex tube related intermittencies in the JLR and the bubble induced eddies in the BCR. The advantages of CWT for obtaining the eddy time-scale and length-scale distribution from the velocity time series is shown. The evaluation of distributions has been carried out using wavelet transform modulus maxima (WTMM) along with a symbolic analysis of the loci of the maxima lines. The structure break-up distribution and the energy break-up distribution that are obtained show a generalization to the known L and P models for intermittencies. The turbulence parameters, i.e., local turbulent kinetic energy, energy dissipation rate and turbulent viscosity, have been calculated and compared using the results obtained from the FFT, DWT, CWT and EIM. For the different approaches these parameters lie in reasonable ranges.

Computational and experimental fluid dynamics of jet loop reactor

AbstractA computational analysis using standard k‐ε model, RSM and LES has been carried out for jet loop reactors (JLR) to investigate the mean and turbulence quantities. These simulations have revealed that the flow in JLR was different from the self‐similar round jets. RSM and LES showed better agreement with PIV measurements compared with standard k‐ε model. The modeled turbulence production and transport in k‐ε model overpredicted those estimated from LES data. To reduce the limitations, modified k‐ε models have been evaluated for JLR. Also, a hybrid k‐ε model has been suggested, which was found to perform better than other modified k‐ε models. This model was also found to hold for stirred tank reactors (STRs). Mixing time analysis has been carried out for JLR and STR at same power consumption. It has been shown that JLR can be inferior to STR if proper nozzle diameter is not selected. © 2009 American Institute of Chemical Engineers AIChE J, 2009