Batch Stirred Tank Reactor Research Articles

Heap and tank leaching of copper and nickel from a Platreef flotation concentrate using ammoniacal solutions

The technical feasibility of ammonia leaching of platinum group mineral (PGM)-bearing Platreef flotation concentrates was investigated as an alternative method for the recovery of base metals before precious metal recovery. The composition of the concentrate sample included 2·02% Cu and 3·17% Ni, mainly as chalcopyrite and pentlandite. A solution containing 4M NH4OH, 4M (NH4)2CO3, buffered in the pH range 9–10, was used as base case lixiviant in column and batch stirred tank reactor tests, around which the effects of total ammonia concentration and operating temperature were explored further. At optimal conditions nearly 100% Cu and Ni extraction were obtained in the batch stirred tank reactor, and 95% Cu and 60% Ni extraction was obtained in columns. The activation energy for chalcopyrite and pentlandite was 36 and 16 kJ mol− 1, respectively, in both reactors, indicating different reaction pathways for the two minerals. Gas-liquid mass transfer appears to be the limiting reaction step in columns much more than in tanks, and the degree of ammonia loss to air is significant. This initial test work indicates the feasibility of using ammonia leaching for this and similar materials as an alternative route to conventional smelting and refining before PGM recovery, but a number of technical challenges still need to be overcome.

Studies on the effect of coal particle size on biodepyritization of high sulfur coal in batch bioreactor

Abstract The moderate thermophilic mix culture bacteria were used to depyritize the Illinois coal of varying particle sizes (-100 μm, 100-200 μm, +200 μm). Mineral libration analysis showed the presence of pyrite along with other minerals in coal. Microbial depyritization of coal was carried out in stirred tank batch reactors in presence of an iron-free 9K medium. The results indicate that microbial depyritization of coal using moderate thermophiles is an efficient process. Moreover, particle size of coal is an important parameter which affects the efficiency of microbial depyritization process. At the end of the experiment, a maximum of 75% pyrite and 66% of pyritic sulphur were removed from the median particle size. The XRD analysis showed the absence of pyrite mineral in the treated coal sample. A good mass balance was also obtained with net loss of mass ranging from 5-9% showing the feasibility of the process for large scale applications.

Heterogeneous biocatalytic processes of vegetable oil interesterification to biodiesel

The heterogeneous biocatalytic interesterification of vegetable oils to ethyl esters of fatty acids is studied. Interesterification with ethanol or ethyl acetate is performed using biocatalysts obtained by incorporating cell lysates of the rE. coli/lip recombinant strain that produces thermostable Thermomyces lanuginosus lipase, into silica xerogel. The interesterification of vegetable oils is performed in both a batch stirred-tank reactor and a continuous reactor with a fixed bed of the prepared biocatalyst. It is shown that ethyl acetate is the best acylating reagent for the interesterification of vegetable oil triglycerides to ethyl esters of fatty acids. Unlike ethanol, ethyl acetate does not inactivate the biocatalyst irreversibly. Under the investigated conditions, the biocatalyst’s half-inactivation time was 720 hours at 40°C.

Synthesis of Methacrylic Anhydride by Batch Reactive Distillation: Reaction Kinetics and Process

The reaction kinetic of the synthesis of methacrylic anhydride was investigated with a batch stirred-tank reactor at atmospheric pressure using methacrylic acid and acetic anhydride as raw materials. The reactions were conducted at several temperatures between 343.15 and 363.15 K and at various starting reactant compositions. A homogeneous reversible reaction of the second order was described. A batch reactive distillation column was employed to obtain methacrylic anhydride. The influence of feed molar ratio, reflux ratio, and entrainer on the reaction was investigated, and a suitable operating parameter was obtained. Under these conditions, the conversion of methacrylic acid was 99.95%, and the yield of methacrylic anhydride was 86.99%.

Fermentative production of dextran using Leuconostoc spp. isolated from fermented food products

Leuconostoc spp. (LS1and LI1) isolated from sauerkraut and idli batter was selected for dextran production. To enhance the yield of dextran, effects of various parameters such as sucrose concentration, pH, temperature, incubation and inoculum percentage were analyzed. The optimum sucrose concentration for the Leuconostoc spp. (LS1 and LI1) was found to be 15% and 25% respectively. Isolates produced maximum dextran after 20 h of incubation at 29° C and the optimum pH was found between 8 and 8.5. The inoculum concentration of 7.5% was more favorable for the production of dextran by Leuconostoc spp. (LS1 and LI1). The growth kinetic parameters were studied and compared for the strains LS1 and LI1. Mass production of dextran was carried out using a stirred tank batch reactor. FTIR analysis was done to determine the functional groups of dextran. sephadex is prepared by cross linking dextran using epichlorohydrin and the functional groups are determined by FTIR analysis.

Operational stability of naringinase PVA lens-shaped microparticles in batch stirred reactors and mini packed bed reactors-one step closer to industry.

The immobilization of naringinase in PVA lens-shaped particles, a cheap and biocompatible hydrogel was shown to provide an effective biocatalyst for naringin hydrolysis, an appealing reaction in the food and pharmaceutical industries. The present work addresses the operational stability and scale-up of the bioconversion system, in various types of reactors, namely shaken microtiter plates (volume ⩽ 2 mL), batch stirred tank reactors (volume <400 mL) and a packed-bed reactor (PBR, 6.8 mL). Consecutive batch runs were performed with the shaken/stirred vessels, with reproducible and encouraging results, related to operational stability. The PBR was used to establish the feasibility for continuous operation, running continuously for 54 days at 45°C. The biocatalyst activity remained constant for 40 days of continuous operation. The averaged specific productivity was 9.07 mmol h(-1) g enzyme(-1) and the half-life of 48 days.

Methyl Esters Selectivity of Transesterification Reaction with Homogenous Alkaline Catalyst to Produce Biodiesel in Batch, Plug Flow, and Continuous Stirred Tank Reactors

Selectivity concept is essential in establishing the best operating conditions for attaining maximum production of the desired product. For complex reaction such as biodiesel fuel synthesis, kinetic studies of transesterification reaction have revealed the mechanism of the reaction and rate constants. The objectives of this research are to develop the kinetic parameters for determination of methyl esters and glycerol selectivity, evaluate the significance of the reverse reaction in transesterification reaction, and examine the influence of reaction characteristics (reaction temperature, methanol to oil molar ratio, and the amount of catalyst) on selectivity. For this study, published reaction rate constants of transesterification reaction were used to develop mathematical expressions for selectivities. In order to examine the base case and reversible transesterification, two calculation schemes (Case 1 and Case 2) were established. An enhanced selectivity was found in the base case of transesterification reaction. The selectivity was greatly improved at optimum reaction temperature (60°C), molar ratio (9 : 1), catalyst concentration (1.5 wt.%), and low free fatty acid feedstock. Further research might explore the application of selectivity for specifying reactor configurations.

Antimicrobial activity of n-butyl lactate obtained via enzymatic esterification of lactic acid with n-butanol in supercritical trifluoromethane

The lipase-catalyzed synthesis of n-butyl lactate by esterification was performed in supercritical trifluoromethane. Immobilized lipase B from Candida antarctica (Novozym 435) was used as a biocatalyst. Process conditions (pressure and temperature) were optimized performing experiments in a high-pressure batch stirred-tank reactor. Experiments were carried out in the operative pressure ranges from 7.5 to 30MPa and at temperatures 35°C and 55°C. For this purpose phase behavior for d,l-lactic acid/n-butanol/Novozym 435/supercritical fluid system at temperature 55°C and different pressures was studied. The highest conversion of lactic acid after 26h of reaction performance was obtained in supercritical trifluoromethane at 30MPa and 55°C.The n-butyl lactate (standard and enzymatically synthesized) and d,l-lactic acid were tested against four food-borne fungi: Saccharomyces cerevisiae, Aspergillus niger, Trichoderma viride and Penicillium cyclopium and three health-damaging bacteria: Escherichia coli, Pseudomonas fluorescens and Bacillus cereus by the agar well diffusion.

Study of a multi-phase hybrid heat exchanger-reactor (HEX reactor): Part I – Experimental characterization

This study focuses on gaining fundamental insights into the sparsely explored area of reacting multiphase flows in a compact heat exchanger. Chevron plate heat exchangers have been demonstrated to possess superior thermal performance, scalability, and mixing capability compared to more traditional shell-in-tube heat exchangers or stirred tank batch reactors. This study explores the hydrodynamic behavior of gas-evolving reacting flows in chevron plate heat exchangers. Experimental characterization of a plate heat exchanger/chemical reactor (in multi-phase flow configuration) utilizing high-speed video and axial pressure measurements was conducted. Existing correlations that were developed using air–water flow in PHEs predicted with acceptable accuracy the total pressure drop in the HEX reactor.

Multi-Objective Optimization Firefly Algorithm Applied to (Bio)Chemical Engineering System Design

Modern engineering problems are often composed by objectives that must be taken into account simultaneously for better design performance. Normally, these objectives are conflicting, i.e., an improvement in one of them does not lead, necessarily, to better results for the other ones. To overcome this difficulty, many methods to solve multi-objective optimization problems (MOP) have been proposed. The MOP solution, unlike the single objective problems, is given by a set of non-dominated solutions that form the Pareto Curve, also known as Pareto Optimal. Among the MOP algorithms, we can cite the Firefly Algorithm (FA). FA is a bio-inspired method that mimics the patterns of short and rhythmic flashes emitted by fireflies in order to attract other individuals to their vicinities. For illustration purposes, in the present contribution the FA, associated with the Pareto dominance criterion and the anti-stagnation operator, is applied to (bio)chemical engineering system design. The first one is related to the alkylation process optimization; the second deals with the optimization of batch stirred tank reactor. The sensitivity analysis of some relevant parameters of the algorithm is performed and compared with the Non-dominated Sorting Genetic Algorithm (NSGA II). The results indicate that the proposed approach characterizes an interesting alternative for multi-objective optimization design.

A thermostable exo-β-fructosidase immobilised through rational design

Thermotoga maritima exo-β-fructosidase (BfrA) secreted by a recombinant Pichia pastoris strain was optimally immobilised on Glyoxyl–Sepharose CL 4B using the Rational Design of Immobilised Derivatives (RDID) strategy. Covalent attachment of the N-glycosylated BfrA onto the activated support at pH 10 allowed total recovery of the loaded enzyme and its activity. The immobilisation process caused no variation in the catalytic properties of the enzyme and allowed further enhancement of the thermal stability. Complete inversion of cane sugar (2.04M) in a batch stirred tank reactor at 60°C was achieved with a productivity of 22.2g of substrate hydrolysed/gram of biocatalyst/hour. Half-life of the immobilised enzyme of 5days at 60°C was determined in a continuously operated fixed-bed column reactor. Our results promote the applicability of the BfrA-immobilised biocatalyst for the complete hydrolysis of concentrated sucrose solutions under industrial conditions, especially at a high reaction temperature.

Precipitation of hydroxyapatite at 37 °C in a meso oscillatory flow reactor operated in batch at constant power density

A meso oscillatory flow reactor (meso‐OFR) was successfully applied for the precipitation of hydroxyapatite (HAp) nanoparticles. Mixing efficiency of the mesoreactor operated batchwise in a vertical tube was evaluated at constant power density, by monitoring variation of hue values upon mixing both spatially and temporally. The best operating conditions for fast mixing and a more homogeneous reaction medium were verified for f = 0.83 Hz and x0 = 4.5 mm. HAp precipitation was then carried out under these conditions at 37 °C for different mixing Ca/P molar ratios. HAp nanoparticles with a mean size (d50) of about 67 nm and a narrow size distribution were obtained. Furthermore, the obtained results show the advantages of the meso‐OFR over a stirred tank batch reactor due to the production, about four times faster, of smaller and more uniform HAp nanoparticles. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4483–4493, 2013

Concentration of eicosapentaenoic acid (EPA) by selective alcoholysis catalyzed by lipases

In this work eicosapentaenoic acid (EPA) enriched acylglycerols were obtained from tuna and sardine oils (9 and 19% weight EPA, respectively) by selective ethanolysis catalyzed by lipases. First, eight immobilized lipases were tested and the best EPA concentration and recovery were attained with lipases QLC® and QLG® from Alcaligenes sp. Lipase QLG® was selected to study the influence of reaction time, temperature and lipase/oil and ethanol/oil ratios. Under the optimized conditions attained (48 h, 20°C, lipase/oil ratio 20% w/w and ethanol/oil molar ratio 2.3:1) and for 59.4% conversion, acylglycerols were obtained with 38.6% EPA and 81.6% recovery from sardine oil. In these optimized conditions the reaction was scaled up to 233 g of sardine oil and carried out in a batch stirred tank reactor, with the lipase contained in a cartridge filter attached to the stirring rod. In this reactor, for 54.8% conversion, acylglycerols were obtained with 35.9% EPA and 82.1% recovery. The EPA‐enriched acylglycerols were separated from the ethyl esters in a short‐path vacuum distiller. At an evaporation temperature of 200°C, a residue with 87.4% acylglycerols (12.6% ethyl esters) was obtained, with an EPA concentration of 33.8 and 64.4% EPA recovery.Practical applications: Marine oils have been shown to have beneficial effects on human health, including positive effects on atherosclerosis, coronary heart disease, inflammatory disease, and perhaps even behavioral disorders. They are attributed to the long‐chain n‐3 polyunsaturated fatty acids, mainly eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). However, it is not clear if both EPA and DHA are equally important in cardiovascular protection, because in most oils both species coexist. In this sense, it is necessary to develop large‐scale purification processes to provide sufficient amounts of oils with high concentrations of both PUFAs on the one hand, and with a high concentration of only one of them on the other. This work studies a method to obtain acylglycerols rich in EPA or in EPA and DHA by selective ethanolysis catalyzed by lipases.

Palm-based medium-and-long-chain triacylglycerol (P-MLCT): production via enzymatic interesterification and optimization using response surface methodology (RSM).

Structured lipid such as medium-and long-chain triacylglycerol (MLCT) is claimed to be able to suppress body fat accumulation and be used to manage obesity. Response surface methodology (RSM) with four factors and three levels (+1,0,-1) faced centered composite design (FCCD) was employed for optimization of the enzymatic interesterification conditions of palm-based MLCT (P-MLCT) production. The effect of the four variables namely: substrate ratio palm kernel oil: palm oil, PKO:PO (40:60-100:0 w/w), temperature (50-70°C), reaction time (0.5-7.5h) and enzyme load (5-15% w/w) on the P-MLCT yield (%) and by products (%) produced were investigated. The responses were determined via acylglycerol composition obtained from high performance liquid chromatography. Well-fitted models were successfully established for both responses: P-MLCT yield (R (2) = 0.9979) and by-products (R (2) = 0.9892). The P-MLCT yield was significantly (P < 0.05) affected by substrate ratio, reaction time and reaction temperature but not enzyme load (P > 0.05). Substrate ratio PKO: PO (100:0 w/w) gave the highest yield of P-MLCT (61%). Nonetheless, substrate ratio of PKO: PO (90:10w/w) was chosen to improve the fatty acid composition of the P-MLCT. The optimized conditions for substrate ratio PKO: PO (90:10 w/w) was 7.26h, 50°C and 5% (w/w) Lipozyme TLIM lipase, which managed to give 60% yields of P-MLCT. Up scaled results in stirred tank batch reactor gave similar yields as lab scale. A 20% increase in P-MLCT yield was obtained via RSM. The effect of enzymatic interesterification on the physicochemical properties of PKO:PO (90:10 w/w) were also studied. Thermoprofile showed that the P-MLCT oil melted below body temperature of 37°C.

Characterization of tributyrin hydrolysis by immobilized lipase on woolen cloth using conventional batch and novel spinning cloth disc reactors

Optimal loading and operating conditions for a new, superior immobilization of amano lipase from Pseudomonas fluorescens on woolen cloth were determined. The optimal enzyme loading was 46.8mggdrycloth−1 with activity of 200U. A batch reactor was used to characterize process conditions important to industrial application of the wool immobilized lipase. The optimal pH for immobilized lipase in tributyrin hydrolysis was 7, slightly lower than that of free lipase (pH 8). The optimal temperature for both free and immobilized lipase was 45°C. The immobilized lipase was more stable to reuse than some other lipase immobilizations, maintaining 85% of its activity after 6 long term runs and 75.8% of the original activity after storage of 40 weeks at 4°C. The thermal stability of lipase was improved by 2.4 times after immobilization. The thermal deactivation rate of immobilized lipase followed the Arrhenius law with Ed=199kJmol−1. The Michaelis–Menten constant (Km) of the lipase increased from 1.63mM to 4.48mM after immobilization. The immobilized lipase was also successfully applied for tributyrin hydrolysis in a novel enzyme process intensification technology – the spinning cloth disc reactor (SCDR): conversion increased by around 13% under similar conditions compared to a conventional batch stirred tank reactor. The SCDR is therefore key to exploiting the advantages of the wool immobilized lipase developed in this work.

Using Y-shaped microreactor for continuous decolorization of an Azo dye

This study reports the decolorization of an Azo dye (DR16) in a Y-shaped microreactor using Fenton process. The effect of important operation parameters, including dye, H2O2, and Fe2+ concentrations; solution pH; and feed flow rates on the decolorization efficiency under continuous conditions, has been studied. The results showed that at pH values between 3 and 4, more DR16 vanished from feed stream. Moreover, higher decolorization efficiencies were obtained at higher Fe2+ and H2O2 concentrations as well as lower dye concentration and feed flow rate. The results indicated that it is possible to reach an efficiency of 86% for DR16 dye decolorization in just 4.2 s, as residence time, using this microreactor. This was obtained due to efficient reactants mixing in the microreactor mixing point. This study illustrates the advantage of using microreactors for continuous flow decolorization process in the comparison with conventional use of batch stirred tank reactors.

Glycerol acetals as diesel additives: Kinetic study of the reaction between glycerol and acetaldehyde

Certain acetals can be produced from renewable resources (bioalcohols) and seem to be good candidates for different applications, such as oxygenated diesel additives. This paper addresses the production of acetals (5-hydroxy-2-methyl-1,3 dioxane and 4-hydroxymethyl-2-methyl-1,3 dioxolane) from glycerol and acetaldehyde using Amberlyst 47 acidic ion exchange resin. This ion exchange resin performed well, recording 100% selectivity toward acetal formation at a suitably high initial glycerol concentration. When the initial acetaldehyde concentration was significantly higher than the glycerol concentration, 2,4,6 trimethyl-1,3,5 trioxane was the main reaction product. Unlike other acetalization reactions, the one studied here does not have thermodynamic limitations, and 100% conversion is achieved under different reaction conditions. A kinetic study was performed in a batch stirred tank reactor to study the influence of different process parameters, such as temperature, feed composition and stirring speed. A pseudo-homogeneous kinetic model was developed to describe this reaction kinetics, proving that its rate is just first order on the acetaldehyde concentration under the conditions studied.

Microbial depyritisation of three different coals by Acidithiobacillus ferrooxidans in a batch stirred tank reactor

The present study aimed to investigate the depyritisation potential of Acidithiobacillus ferrooxidans on two different types of coals, namely lignite and anthracite collected from three different countries (Korea, China and Indonesia). The experimental work was conducted on a batch mode in a stirred tank reactor. All the batch biooxidation of pyrite in the different coal samples were conducted in a pH controlled condition (pH = 1·5). The growth medium employed for the batch biooxidation of pyritic coal was free from iron supplement. At. ferrooxidans oxidised mineral pyrite of Korean anthracite at a greater rate (98%) compared to 96 and 92% of pyrite oxidation for Indonesian and Chinese lignite respectively. The ratio of bioleach residue to the feed was reasonably good with range of 8·56–9·06 stating the net mass loss of 9–14. Coal depyritisation was carried out by the available Fe3+ ion in the inoculum producing Fe2+ ion as a product and this Fe2+ ion was further oxidised to Fe3+ ion by At. ferrooxidans. This Fe3+ ion produced by At. ferrooxidans continued the oxidation of the residual pyrite in the coal until all pyrite content was oxidised completely. The three different coals were found to be feasible for biological depyritisation of the coal could be scaled up for further studies in a continuous stirred tank bioreactor.L’étude présente avait pour but d’examiner le potentiel d’enlèvement de la pyrite par Acidithiobacillus ferrooxidans dans deux types de charbons, soit le lignite et l’anthracite, récoltés dans trois pays, soit la Corée, la Chine et l’Indonésie. On a effectué le travail expérimental dans un mode en vrac, dans un réacteur agité. On a effectué toute la bio-oxydation en vrac de la pyrite des échantillons de charbon à un pH contrôlé de 1·5. Le médium de croissance utilisé pour la bio-oxydation en vrac du charbon pyritique ne contenait pas de supplément de fer. At. ferrooxydans oxydait le minerai de pyrite de l’anthracite coréen en plus grande proportion (98%) que l’oxydation de la pyrite du lignite indonésien (96%) ou chinois (92%), respectivement. Le rapport de résidu de biolixiviation à l’alimentation était raisonnablement bon, avec une gamme de 8·56 à 9·06, établissant la perte de masse nette de 9 à 14. L’enlèvement de la pyrite du charbon était effectué par l’ion Fe3+ disponible dans l’inoculum, donnant lieu à l’ion Fe2+ comme produit et cet ion Fe2+ était davantage oxydé en ion Fe3+ par At. ferrooxidans. Cet ion Fe3+ produit par At. ferrooxidans continuait l’oxydation de la pyrite résiduelle dans le charbon jusqu’à ce que toute la pyrite soit complètement oxydée. On a trouvé qu’il était possible d’effectuer l’enlèvement biologique de la pyrite des trois charbons et d’augmenter l’échelle pour des études futures dans un bioréacteur en continu agité.

Bench-scale batch bioleaching of spent petroleum catalyst using mesophilic iron and sulfur oxidizing acidophiles

Microbial leaching of a petroleum spent catalyst was carried out using mixed mesophilic iron and sulfur oxidizing acidophiles. Bench-scale batch stirred tank reactors with a working volume of 1 L were used in this study at 35 °C. The pulp density considered for the study was 10% (w/v), while the particle size of the spent catalyst was varied by 45–106, 106–212 and >212 μm. The leaching percentage of Ni from the spent catalyst was found to be highest (97–98%) with varying particle size. However, the leaching yield for rest of the metals like Al, Fe, V and Mo was 70–74%, 66–85%, 33–43% and 22–45%, respectively. Influence of particle size was predominant on the recovery of all metals except Ni. Assessment of the generation of the bioleach residue after bioleaching showed a weight loss of 54–62% due to the dissolution of the metal values from the spent catalyst. The mineralogical study conducted by X-ray diffraction and scanning electron microscopy supports the dissolution of metals from the spent catalyst. Jarosite mineral phase was the dominant mineral phase in the bioleach residue due to the dissolution of the oxidic and sulfidic mineral phases present in the feed spent catalyst.

The spinning cloth disc reactor for immobilized enzymes: A new process intensification technology for enzymatic reactions

The spinning cloth disc reactor (SCDR) is an innovative enzyme reaction intensification technology. Based on spinning disc technology, the SCDR uses centrifugal forces to allow an even spread of a thin film across a spinning horizontal disc which holds a cloth with immobilized enzyme. This geometry promotes accelerated reactions due to high mass transfer rates and rapid mixing. Here, the SCDR has been benchmarked against a conventional batch stirred tank reactor (BSTR) using tributyrin emulsion hydrolysis as a model reaction and lipase immobilized on woolen cloth as the biocatalyst. Reaction intensification has been shown to occur: the conversion in the SCDR was significantly higher than that in a conventional BSTR under comparable conditions. Spinning speed and flow rate control reaction rate and conversion: conversion increased nearly 7% on average as the flow rate rose from 2 to 5mLs−1 and the highest conversion (72.1%) occurred at 400rpm. A Ping Pong Bi Bi kinetic model fitted reaction progress data well. The immobilized lipase showed excellent stability to repeat reactions in the SCDR: 80% of the original activity was retained after 15 consecutive runs. The robustness of the SCDR to industrially relevant feeds was also demonstrated through successful hydrolysis of different vegetable oils at reaction rates 5 times higher than other reactors in the literature. Overall, the above results indicate that the SCDR is an innovative, superior and robust technology for enhancing enzyme reactions, taking enzyme reactors beyond the current state-of-the-art. This concept can readily be extended to other enzyme-catalyzed reactions, where enhanced mass transfer and enzyme stability is needed.