Mixed Reactor Research Articles

Light Intensity Effects on Bioproduct Recovery from Fuel Wastewater Using Purple Phototrophic Bacteria in a Hybrid Biofilm-Suspended Growth System.

This research looked at how three different light intensities (1600, 4300, and 7200 lx) affect the biomass development, treatment of fuel synthesis wastewater and the recovery of valuable bioproducts between biofilm and suspended growth in a purple-bacteria enriched photobioreactor. Each condition was run in duplicate using an agricultural shade cloth as the biofilm support media in a continuously mixed batch reactor. The results showed that the highest chemical oxygen demand (COD) removal rate (56.8 ± 0.9%) was found under the highest light intensity (7200 lx), which also led to the most biofilm formation and highest biofilm biomass production (1225 ± 95.7 mg). The maximum carotenoids (Crts) and bacteriochlorophylls (BChls) content occurred in the suspended growth of the 7200 lx reactor. BChls decreased with light intensity in suspended growth, while in biofilm both Crts and BChls were relatively stable between light conditions, likely due to an averaging effect as biofilm thickened at higher light intensity. Light intensity did not affect protein content of the biomass, however, biofilm showed a lower average (41.2% to 43.7%) than suspended biomass (45.4% to 47.7%). For polyhydroxybutyrate (PHB) the highest cell concentration in biofilm occurred at 1600 lx (11.4 ± 2.4%), while for suspended growth it occurred at 7200 lx (22.7 ± 0.3%), though total PHB productivity remained similar between reactors. Shading effects from the externally located biofilm could explain most variations in bioproduct distribution. Overall, these findings suggest that controlling light intensity can effectively influence the treatment of fuel synthesis wastewater and the recovery of valuable bioproducts in a biofilm photobioreactor.

Application of Box-Behnken design in monoglycerides production via glycerolysis of palm oil using homogenizer reactor

The glycerolysis of triglycerides (TG) to produce monoglycerides (MG) is an important pathway for glycerol valorization. However, mass transfer resistance has significantly hindered the process efficiency because the reaction is a two-phase liquid-liquid reaction. In this study, a homogenizer was used as a high shear mixing reactor (HSM) to address such issue of mass transfer resistance, and was compared to a conventional mechanically stirred reactor (MS). The effects of the rotational speed, catalyst amount, molar ratio of Gly-to-TG, reaction temperature and reaction time on MG yield were investigated using NaOH as a homogeneous catalyst. Three reaction variables were investigated by statistical analysis using the Box-Behnken (BBK) experimental design, including Gly-to-TG molar ratio (2:1–4:1), catalyst loading (0.1–0.3 wt% TG), and reaction time (15–45 min). The results indicated that the predicted maximum MG yield of 63.4 % was achieved at a reaction time of 29 min, a Gly-to-TG molar ratio of 2.7:1, and a catalyst loading of 0.274 wt% of TG, which agreed with the experimental results. The yield efficiency of HSM was 1.27×10−4 g/J, which was 9.14-fold higher than that of MS at 1.39×10−5 g/J.

High mixing enhancement for continuous uniformity Li/Al-LDHs in lithium extraction from low grade salt lakes

The enhancement of lithium extraction from low grade salt lake through the development of advanced adsorbents has become a primary focus in current research. A new method was developed in this work for the continuous fabrication of ultra-highly uniform lithium-aluminum layered double hydroxides (H-LDHs), used as lithium adsorbents, through a high mixing reactor. These H-LDHs featured a more consistent particle size distribution, which facilitated an enhanced vibrational density. This not only significantly increased the powder content in granules but also improved lithium adsorption efficiency. Computational fluid dynamics (CFD) modeling showed that the reactor reached peak mixing efficiency with a minimal gap size of 1 mm. The analysis further indicated that a Reynolds number of 75 led to enhanced mixing effects and stronger flow dynamics. Experiments with Qarhan salt lake brine demonstrated that the H-LDHs powders reached a lithium adsorption capacity of up to 7.27 mg/g, while the volumetric adsorption capacity of these H-LDHs granules exceeded that of traditional granules by 1.179 times. Subsequent desorption and cycling experiments verified the material’s enduring lithium adsorption efficacy and structural integrity, underscoring its considerable potential for industrial use.

Aluminate 2K systems in digital concrete: Process, design, chemistry, and outlook

Digital concrete is advancing due to growing economic incentives for construction automation. Achieving more sustainable concrete construction requires carbon reduction, and digital concrete technologies enable material-saving designs. By decoupling production strength from design strength, two-component (2K) systems utilizing aluminate precipitation offer the most flexibility, allowing more sustainable mixes with higher substitution levels. However, 2K aluminate systems are complex and demand a deeper understanding of their chemistry and strength buildup. This article reviews the basics of 2K aluminate systems, specifically aluminum sulfate-based and calcium aluminate cement/calcium sulfate-based systems, and their use in an inline active mixing reactor. An example reaction engineering analysis predicts the degree of reaction in a given reactor design, relating it to yield stress. The two chemical systems are compared, and future research recommendations are provided.

Analysis and Design of Sequencing Batch Reactor Basin for Sewage Treatment Plant by using Autocad

bstract: The objectives of this project are to review and evaluate sewage treatment technologies and propose a method to improve or select appropriate technology. Sequencing batch reactor (SBR) is a part of the secondary treatment process of sewage treatment. It is fill and draw-type of activated sludge system involving a single complicated mix reactor where all steps of an activated sludge process take place. The objectives of this project are to review and evaluate sewage treatment technologies and propose a method to improve or select appropriate technology. Sequencing batch reactor (SBR) is a part of the secondary treatment process of sewage treatment. It is fill and draw-type of activated sludge system involving a single complicated mix reactor where all steps of an activated sludge process take place.

CONSERVATION LAWS OF CHEMICAL REACTIONS IN A CLOSED NONISOTHRUM INCOMPLETE MIXING REACTOR

In chemical reactions occurring stationary or non-stationary in closed isothermal ideal mixing reactors (CSTR), the classical linear stoichiometric laws of conservation are always satisfied, reflecting the constancy of atoms of one type or another during the entire reaction. In real conditions, taking into account possible deviations from ideal mixing conditions or violations of the constancy of temperature conditions, various macroscopic factors (mass transfer, heat transfer) can have a noticeable influence on the course of the reaction. To study the kinetics of such processes, a more general mathematical model of an incomplete mixing reactor (IMR) is used. It is of interest to study the influence of diffusion and convection on the patterns of stationary modes of non-isothermal chemical reactions associated with the existence of more general (non-stoichiometric) conservation laws (kinetic invariants). It is more difficult to detect such invariants (especially temperature ones) in IMRs than in CSTR, and at present they are practically not studied. In this work, for chemical reactions occurring in a closed non-isothermal IMR according to the kinetic law of mass action, linear concentration and temperature conservation laws are established, which take into account the complicating processes of diffusion and convection. These conservation laws relate the stoichiometry of the reaction mechanism to the concentrations of reagents, the temperature of the reaction medium and the intensity of macrokinetic processes, which allows them to be used for a more reasonable identification of linear and nonlinear mechanisms of chemical reactions when solving the inverse problem of chemical kinetics. The new kinetic conservation laws presented in the work can be discovered a priori and verified experimentally. For citation: Kol'tsov N.I. Conservation laws of chemical reactions in a closed nonisothrum incomplete mixing reactor. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 7. P. 111-118. DOI: 10.6060/ivkkt.20246707.6976.

A draft tube to improve mixing in swirling flow-based solid–liquid mixing reactors

The Swirl Flow Reactor (SFR) is a recently proposed specially designed reactor to address challenges of solid–liquid mixing for high-temperature and high-pressure processes. Previous research has shown that the mixing homogeneity of the SFR is not yet optimal and has still potential for improvement. To enhance the homogeneity of the SFR and to optimize the utilization of the previously identified Precessing Vortex Core at the nozzle, an improvement is proposed by the inclusion of a draft tube in the reactor center. Computational Fluid Dynamics is used to study the flow structure, particle distribution, and large-scale coherent structures in the SFR. The improved SFR has been validated for its more homogeneous mixing, where the homogeneity is improved from 0.945 for the original reactor to 0.991 in the new proposed design. Also, the influence of the draft tube on the fluctuating velocities and turbulence within the improved SFR has been indicated. In addition, Spectral Proper Orthogonal Decomposition (SPOD) is used to identify and reconstruct the coherent structures in the reactor. A flattened double-layer helical precessing vortex core (PVC) and its second-order harmonic at frequencies of 35.8 Hz and 71 Hz have been identified, which introduce extra large scale mixing near the nozzle of the reactor.

The Physicochemical Basis for the Production of Rapeseed Oil Fatty Acid Esters in a Plug Flow Reactor

This article describes the results of a comprehensive comparative study of the production of fatty acid ethyl esters (FAEEs) for use as biodiesel in perfect mixing reactors (PMRs) and plug flow reactors (PFRs). The products obtained on a laboratory scale at all stages of the separation and purification of the FAEE phase were analyzed using the FTIR, XRF and GC-MS methods. We compared distillation methods for the separation of stoichiometrically excessive ethanol from the reaction mixture. Neutralization methods with H2SO4 solution and carbonation with CO2 were applied for FAEE phase purification from the catalyst. Emulsions formed during the water flushing stage were analyzed via the optical microscopy method. The optimal conditions of stirring speed and temperature were selected to maintain a high level of FAEE–water phase contact area with minimum phase separation time. The efficiency of the carbonation method for catalyst neutralization in the FAEE phase has been proven, allowing us to consider this method as an alternative to the traditional acid neutralization method. According to the results of experimental studies, we have developed a new high-performance technological scheme for the production of fatty acid esters in PFRs. The synthesis of FAEEs in a stoichiometric excess of ethanol of about 1:50 allowed us to increase the reaction rate and productivity of the synthesis unit after the transition from a PMR to a PFR. The yield of the product amounted to 86.7%. The purified FAEE fraction complied with most EN14214 specifications.

Study on the Efficacy of Recessed Green Space in Rainwater Harvesting and Utilization in Urban Roads

Abstract In order to confirm the performance of recessed green space in rainwater collection and utilization of urban roads, this paper proposes a corresponding experimental test program, which mainly covers the evaluation of rainwater infiltration, the evaluation of rainwater purification, and the simulation of rainfall-runoff reduction. Using the above test methods, the effectiveness of recessed green space in collecting and utilizing rainwater was analyzed. The results showed that in the one-way analysis of the compositional structure of the undercroft green space, the gravel layer, the media layer, and the vegetation layer had no significant difference in the infiltration rate sig<0.05, and all three had no significant difference with the infiltration rate. The order of rainwater infiltration effect of the four reactors was 3/7 mixed media reactor (23.08 ml/min) > red loam reactor (23.04 ml/min) > 2/8 mixed media reactor (23 ml/min) > black loam reactor (23.08 ml/min), while the order of purification effect was 3/7 mixed media > 2/8 mixed media > red loam > black loam. In addition, the combined high infiltration hypolimnetic green space had a better retention effect (flow yield range from 0 to 10 L) in rainfall-runoff with a reproduction period of 3 and 4 years. Based on the analysis results, the application effect of undercroft green space in urban road rainwater collection and utilization is comprehensively verified, and it is hoped that the investigation of this paper can bring certain references and references to the relevant personnel.

Enzymatic degradation of pea fibers changes pea protein concentrate functionality

Pea proteins are gaining increased interest from both the food industry as well as from consumers. Pea protein isolates (PPI) excel at forming meat-like textures upon heating while pea protein concentrates (PPC) are more challenging to transform into highly sought-after foods. PPCs are richer in dietary fibers (DF) and are more sustainable to produce than PPI. In this work, degradative enzymes were used to modify the functionality of PPC-water blends with a focus on texturization upon heating. Three enzyme solutions containing β-glucanases, hemicellulases, pectinases, xylanase, and cellulases were added to 65 wt% PPC blends. The effect of these enzymatic pretreatments was measured by monitoring the torque in a mixing reactor during blending, differential scanning calorimetry (DSC), high-pressure shear rheology (HPSR), and DF content and size analysis. Four endothermic peaks were detected in the DSC thermograms of PPC, namely at 63 °C, 77 °C, 105 °C and 123 °C. The first three peaks were attributed to phase transition and gelation temperatures of the starches and proteins constituting PPC. No endothermic peaks were measured for PPI blends. Enzyme solutions containing β-glucanases, hemicellulases, pectinases, and xylanases increased the endothermic energy of all peaks, hinting at an effect on the gelation properties of PPC. The same enzymes decreased the resistance to flow of PPC blends and induced a shift of the weight average molecular weight (Mw) distribution of soluble dietary fibers (SDF) towards smaller values while increasing the fraction of SDF by decreasing the insoluble dietary fiber (IDF) content. The solution containing cellulases did not change the DSC results or the viscosity of the PPC mixture, nor did it affect the IDF and SDF contents. On the other hand HPSR measurements of heated PPC samples up to 125 °C showed that all tested enzyme solutions decreased the complex viscosity of PPC-water blends to values similar to PPI-water blends. We demonstrated that degradative enzymes can enhance the functionality of less refined protein-rich ingredients based on pea and other vegetal sources. Using optimized enzyme blends for targeted applications can prove to be a key changer in the development and improvement of sustainable protein-rich foods.

Grazing resistance developed in Escherichia coli K-12 during coexistence with a bacterivorous protist.

A development of grazing resistance in Escherichia coli K-12 was examined in the presence of a bacterivorous protist, Spumella sp. TGKK2. Two transformants were generated from E. coli K12 for grazing experiments. One was E. coli K-12-TGF, which possesses tetracycline resistance and green fluorescence. The other was E. coli K-12-KRF with kanamycin resistance and red fluorescence. These strains can be selectively colonized on antibiotic-containing agar media and further confirmed by their fluorescent colors. First, we added protist-untouched E. coli K-12-KRF to protist-touched residual E. coli K-12-TGF that had been attacked by Spumella sp. TGKK2 in a batch test. Then the survivability of the respective strains was investigated. Consequently, E. coli K-12-KRF was predated preferentially. On the other hand, E. coli K-12-TGF in the same tube was less predated, indicating some grazing resistance. Similar phenomena were observed when the conditions of these two strains of bacteria were reversed. Also, a continuous culture device supplied with a glucose-containing medium as a substrate was operated. The device connected two complete mixed reactors in series. E. coli K-12-TGF was cultivated in the first reactor, and then grown E. coli K-12-TGF was predated by Spumella sp. TGKK2 in the second reactor. The effluent in the second reactor containing residual E. coli K-12-TGF and Spumella sp. TGKK2 was supplemented with batch-cultured E. coli K-12-KRF. Consequently, it was confirmed that bach-cultured E. coli K-12-KRF never exposed to protist was predated preferentially. These findings reveal that E. coli K12 acquires some predation resistance through coexistence with the bacterivorous protist.

Evaluating hydrogen production from glucose using graphite felt beads as a solid matrix in immobilized mixed cell reactor at thermophilic fermentation

This study has successfully evaluated graphite felt (GF) beads as a solid matrix to immobilize or trap the mixed cultures in an immobilized mixed-cell reactor (IMcR). The anaerobic sludge of palm oil mill effluent was used as an inoculum source in the IMcR with mixed culture. Here, glucose, sucrose, and starch were used as the model substrates to evaluate the performance of IMcR with GF beads for producing bio-hydrogen (BioH2). BioH2, effluent, and surface morphology of GF beads were analyzed by using gas chromatography equipped with a thermal conductivity detector, high-performance liquid chromatography, and scanning electron microscopy, respectively. The highest H2 yield (YH2) and production rates were obtained at 304.0 ± 13.2 mL g?1COD (corresponding to 2.26 mol mol?1glucose) and 1403 ± 61 mL L?1 day?1, respectively. IMcR with GF beads is a new approach for generating high YH2, which can be used for more than two months in an experimental run.

Enhancing biodiesel production in stirred tank reactors through the implementation of a baffle array: Creating a reactor with unique characteristics

This study focuses on enhancing biodiesel production from expired refined palm oil by implementing baffle arrays with a suitable dimension ratio into a conventional stirred tank reactor. This reactor functions as a deglycerolizing reactor at low agitation speeds (250 rpm), or an intensive mixing at high agitation speeds (500 rpm). With these unique characteristics, this reactor outperformed its traditional counterparts and could produce biodiesel via a simplified, single-step transesterification process. The optimal reaction condition was 1:6 oil to MeOH ratio, 1.0 wt% KOCH3, 30-minute reaction time and 60 °C reaction temperature. Ester content of 98.13 wt% was obtained in the deglycerolizing reactor and 98.54 wt% in the intensive mixing reactor with the number of baffles of 16. This achievement represents a 50 % reaction time reduction and 30 % reactor cost reduction compared to the conventional reactor with similar reaction condition and production capability.

Premise Plumbing Pipe Materials and In-Building Disinfectants Shape the Potential for Proliferation of Pathogens and Antibiotic Resistance Genes.

In-building disinfectants are commonly applied to control the growth of pathogens in plumbing, particularly in facilities such as hospitals that house vulnerable populations. However, their application has not been well optimized, especially with respect to interactive effects with pipe materials and potential unintended effects, such as enrichment of antibiotic resistance genes (ARGs) across the microbial community. Here, we used triplicate convectively mixed pipe reactors consisting of three pipe materials (PVC, copper, and iron) for replicated simulation of the distal reaches of premise plumbing and evaluated the effects of incrementally increased doses of chlorine, chloramine, chlorine dioxide, and copper-silver disinfectants. We used shotgun metagenomic sequencing to characterize the resulting succession of the corresponding microbiomes over the course of 37 weeks. We found that both disinfectants and pipe material affected ARG and microbial community taxonomic composition both independently and interactively. Water quality and total bacterial numbers were not found to be predictive of pathogenic species markers. One result of particular concern was the tendency of disinfectants, especially monochloramine, to enrich ARGs. Metagenome assembly indicated that many ARGs were enriched specifically among the pathogenic species. Functional gene analysis was indicative of a response of the microbes to oxidative stress, which is known to co/cross-select for antibiotic resistance. These findings emphasize the need for a holistic evaluation of pathogen control strategies for plumbing.

Diffusive–layered convection in Y-shaped continuous-flow microreactor

Efficient and rapid mixing of fluids in continuous-flow microfluidic devices plays an important role in a wide range of applications. Although there are many different methods to enhance mixing in such reactors, the potential of natural convection to mix fluids has been overlooked because of its possible limitations at the microscale. Recent studies have challenged this statement by demonstrating the significance of both gravity-dependent and gravity-independent types of natural convection in improving mixing efficiency. It was shown that inducing double-diffusive convection, Marangoni convection, or Rayleigh–Taylor convection can greatly enhance the mixing of two aqueous solutions in a continuous-flow microreactor. In this study, we experimentally investigate the influence of another type of differential-diffusion instability, known as diffusive–layered convection, on the mixing of two aqueous solutions of chemically inert substances in a Y-shaped continuous-flow microreactor. We consider the scenario when two miscible solutions flow into the main channel through distinct tubes, in which they come into contact and mix, thus causing the onset of diffusive–layered convection. We used two experimental methods, including laser interferometry and dye visualization, to analyse the mixing process. Surprisingly, despite the vigorous convective motion driven by diffusive–layered convection, the intensity of mixing of pumped fluids remains comparable to the scenario when solutions mix only via a diffusion mechanism. We explain this unexpected result by the unique structure of the convective motion, which prevents system homogenization. A comparison with the results previously obtained for double-diffusive convection is performed, and pure diffusive mixing scenarios are implemented.

PROTECTIVE METAL COATINGS MADE OF MOLYBDENUM ON STEEL 12Cr18Ni10Ti FOR FLUORIDE MELTS. OBTAINING, CERTIFICATION, EFFICIENCY

The successful use of molten alkali metal fluorides as an electrolyte for high-temperature devices requires the development of such reactor materials that have high corrosion resistance in melts with compositions characteristic of liquid-salt mixing reactors. This is one of the most important unresolved problems. One of the effective ways to reduce corrosion losses is to create a layer on the surface of the material that protects the metal from the corrosive effects of the environment. In this paper, molybdenum insulating coatings on steel 12Kh18Ni10Ti obtained in molten salts of various compositions and by various methods are considered as protective layers. Experiments were carried out on the electrodeposition of molybdenum coatings on structural materials based on iron (steel 12Cr18Ni10Ti). The coatings obtained by the electrochemical method are inhomogeneous and easily exfoliating. The thickness of molybdenum coatings obtained from molten salts is 8.15 and 20.34 μm on steel in FLiNaK and LiCl–KCl melt, respectively. Corrosion tests have shown the inefficiency of the molybdenum coating obtained from both chloride and fluoride melts. The corrosion rate of 12Cr18Ni10Ti steel in FLiNaK/FLiNaK + 5% CeF3 melts at 650°C and a holding time of 100 hours decreases in the following row: 12Cr18Ni10Ti + Mo (0.75/0.77 mm/year) 12Cr18Ni10Ti (0.45/0.50 mm/year).

Design the mechanical–chemical reactor for oily wastewater treatment

This study explains the mechanical design of a mixer with a focus on the fluid forces generated by the fluid continuum in the mixing reactor on the impellers. The research demonstrates that the forces are caused by transient asymmetries in fluid flow that act on the mixing impeller. The mixer shaft and gear reducer receive these dynamic loads from the impeller blades. A general equation for the fluid force behavior can be developed. The research also stresses on the significance of the mechanical interaction of the mixing process with the mixing vessel and impeller. Four parameters were measured; impeller speed for coagulation and flocculation, mixing time for coagulation, and flocculation. The experimental results in the final section will explain that impellers with four blades provide higher oil removal than impellers with two blades in oily wastewater treatment.

Tank Jet Mixer Design, Arrangement & Applications

Side entry mixers or jet mixers are commonly used to achieve mixing in storage tanks and reactors. Impellers are other conventional devices used for mixing in industry, but they are expensive for large storage tanks and underground tanks. Jet mixers have been a better alternative to impellers in the process industry. Compared with Mechanically agitated mixers, these mixers use jet technique to create high turbulence, high shear rates and vortex motion offer several advantages in achieving rapid mixing over a short period of time without any moving parts. Jet mixing has become an alternative to conventional impeller mixing for various applications in process industries. To ensure optimal mixing performance, it is important to understand the basis of jet mixer design & also impact of different parameters in jet mixer design & preferred installation of mixers.

A solid-liquid mixing reactor based on swirling flow technology

Solid-liquid mixing is often applied in the chemical industry to keep solids in suspension for, amongst others, crystallization, adsorption, heterogeneous catalysis, etc. The most widely used technology to obtain a good degree of mixing is the mechanically stirred tank reactor. However, this technology is limited to small reactor volumes in case of high pressure/temperature processes due to sealing issues. An alternative for solid-liquid mixing is the application of swirling flow. This work studies the mixing capacities of a specially designed reactor geometry, the Swirling Flow Reactor (SFR). Computational Fluid Dynamics (CFD) is used to simulate the flow field and particle distribution in the SFR, where the RNG k−ϵ model and the Eulerian-Eulerian (E-E) multi-phase approach with a Kinetic Theory of Granular Flow (KTGF) model are applied for their proven effectiveness in the study of dense solid-liquid mixing problems. The effectiveness of mixing in the SFR is assessed by the axial particle distribution and homogeneity H. The mechanism of particle recirculation in the SFR is also identified, in which a Coanda jet flow (CoJF) formed by a specially designed inlet nozzle plays an important role in washing the reactor bottom surface. Additionally, Spectral Proper Orthogonal Decomposition (SPOD) is used to identify and reconstruct the coherent structures in the swirling flow. The results indicate that precessing coherent flow structures are present, which include the dominant double layer double helical vortex core and its second order harmonic, the double layer quadruple helical vortex core.

Development of a scale-up strategy for an aerated coaxial mixer containing a non-Newtonian fluid: A mass transfer approach

Coaxial mixers have been shown to be effective in enhancing the hydrodynamic stress and shear environment inside the aerated systems. However, the scale-up study of the aerated coaxial mixing reactors based on a constant mass transfer coefficient has never been reported in the literature. In this study, for the first time, a practical technique is suggested to evaluate the scalability of these systems in terms of a constant mass transfer coefficient. The effects of impeller speed, impeller type, aeration rate, and pumping direction on the mass transfer, power consumption, gas holdup profile, fluid hydrodynamics, and energy dissipation rate were explored for gas dispersion in non-Newtonian fluids inside coaxial mixers through tomography, dynamic gassing-in, and computational fluid dynamics. It was found that a practical approach to preserve the mass transfer coefficient of the large-scale coaxial mixer the same as its small-scale counterpart was to maintain the volumetric aeration rate per working fluid volume constant.