CSTR Reactor Research Articles

Kinetics Reaction and Mechanism of Thiozole with Sodium Methoxide in CSTR Reactor

Sulphur and nitrogen containing organic compounds are gaining importance in synthetic and pharmaceutical fields. Thiazoles are a heterocyclic organic compound is well known intermediates in thesynthesis of clinically important heterocycles such as 4-thiozolidinones and benzothiozoles. Thiazoles are found in medicaments like vitamin-B, sulphathiozoles, promizole, niridazole, aminotrizole and tetramisole. Therefore, and because of the importance of these compounds, the understanding and study of the mechanism and kinetic of their reactions are particularly important.

Pilot plant experience on anaerobic codigestion of source selected OFMSW and sewage sludge

Anaerobic codigestion of source selected organic fraction of municipal solid waste (SS-OFMSW) and sewage sludge may be one of the most viable solutions to optimize oversized digesters efficiency in wastewater treatment plants. Based on results of BMP tests obtained for sewage sludge and SS-OFMSW, pilot plant tests were carried out by 3.4m3 CSTR reactor at mesophilic temperature. A mix of fruit and vegetable waste from wholesale market and canteen waste was used as SS-OFMSW substrate. Tests were conducted applying an OLR (organic loading rate) ramp with 6 different phases until a value of 3.2kgVS/m3d. Feedstock and digestate characteristics, efficiency and process parameters were monitored. The anaerobic codigestion development was stable in each phase: early indicators like VFA (volatile fatty acids) and FOS/TAC ratio were always below instability threshold values. The maximum OLR tested determined a GPR (gas production rate) of 0.95Nm3/m3d and SGP (specific gas production) of 0.49Nm3/kgVS with a VS abatement of 67.3%.

Sampling Frequency and Digital Noise Filtering for Transient Kinetic Study in CSTR via Temperature Scanning and Composition Modulation Technique

Temperature Scanning and Composition Modulation technique (TS-CM) is a technique for estimating reaction parameters under transient conditions in a CSTR reactor. Studies of reaction kinetics performed under transient conditions can lead to savings of time and resources as compared to the conventional steady-state method. This is because a collection of data necessary for extracting the reaction kinetics can be obtained within a single experiment. This research focused on the refinement of TS-CM technique as an efficient tool for reaction kinetics studies. The alkaline hydrolysis of ethyl acetate was used as a model reaction. Different degrees of noise intensity were added to the output signal of NaOH concentration in order to study the effect of noise (0.5, 1.0, 3.0 and 5.0%) and sampling period (1, 30 and 60 seconds) on the accuracy of reaction kinetics. Results revealed that the sampling period of 1 second yielded only slight errors of kinetic parameters compared to that of without noise . The second part dealt with noise filtering. In order to smooth the NaOH concentration data, TS-CM technique was applied with three digital filters: a) the first-order filter or first-order filter, b) the second-order filter or second-order filter and c) the Savitzky-Golay filter. Results showed that the best filter was the Savitzky-Golay, which filtered with 81 points of window size and 2 nd order of polynomial degree.

Evaluation of anaerobic co-digestion of dairy manure with food wastes via bio-methane potential assay and CSTR reactor

The introduction of food wastes into anaerobic digestion (AD) brings a promising scenario of increasing feedstock availability and overall energy production from AD. This study evaluated the biodegradability and methane potential from co-digestion of two typical food wastes, kitchen waste and chicken fat, with dairy manure. For single substrate, the bio-methane potential assays showed that kitchen waste had the highest methane yield of 352 L-CH4 kg–1-VS added, 92% more than dairy manure alone. Chicken fat at the same Volatile Solid (VS) level (2 g L–1) inhibited bio-methane production. Addition of kitchen waste and chicken fat to a VS percentage of up to 40% improved overall methane yield by 44% and 34%, respectively. Synergistic effect was observed when either combining two or three substrates as AD feedstock, possibly as a result of increased biodegradability of organic materials in chicken fat and kitchen waste compared with dairy manure. Addition of chicken fat improved methane yield more than kitchen waste. However, addition of chicken fat VS over 0.8 g L–1 should be cautiously done because it may cause reactor failure due to decrease in pH. The maximum methane yield was 425 L-CH4 kg–1-VS, achieved at a VS ratio of 2:2:1 for kitchen waste, chicken fat, and dairy manure. Results from batch AD experiment demonstrated that supplementing dairy manure to chicken fat and/or kitchen waste improved alkalinity of substrate due to the inclusion of more titratable bases in dairy manure, and therefore stabilized the methanogenesis and substantially improved biogas yield. A mixture of substrates of kitchen waste, chicken fat, and dairy manure at a ratio of 1:1:3 was fed to a continuously stirred tank reactor operated at organic loading rates of 3.28, 6.55, and 2.18 g-COD L–1-day (hydraulic retention time of 20, 10, and 30 days, respectively) under mesophilic condition, and methane production rate reached 0.65, 0.95, and 0.34 L-CH4 L–1-reactor-day.

Kinetic modelling of anaerobic hydrolysis of solid wastes, including disintegration processes

A methodology to estimate disintegration and hydrolysis kinetic parameters of solid wastes and validate an ADM1-based anaerobic co-digestion model is presented. Kinetic parameters of the model were calibrated from batch reactor experiments treating individually fruit and vegetable wastes (among other residues) following a new protocol for batch tests. In addition, decoupled disintegration kinetics for readily and slowly biodegradable fractions of solid wastes was considered. Calibrated parameters from batch assays of individual substrates were used to validate the model for a semi-continuous co-digestion operation treating simultaneously 5 fruit and vegetable wastes. The semi-continuous experiment was carried out in a lab-scale CSTR reactor for 15weeks at organic loading rate ranging between 2.0 and 4.7gVS/Ld. The model (built in Matlab/Simulink) fit to a large extent the experimental results in both batch and semi-continuous mode and served as a powerful tool to simulate the digestion or co-digestion of solid wastes.

Augmented biogas production from protein-rich substrates and associated metagenomic changes

This study demonstrates that appropriate adaptation of the microbial community to protein-rich biomass can lead to sustainable biogas production. The process of acclimation to these unusual mono-substrates was controlled by the protease activity of the microbial community. Meat extract (C/N=3.32) and kitchen waste (C/N=12.43) were used as biogas substrates. Metagenome analysis highlighted several mesophilic strains that displayed a preference for protein degradation. Bacillus coagulans, Bacillus subtilis and Pseudomonas fluorescens were chosen for detailed investigation. Pure cultures were added to biogas reactors fed solely with protein-rich substrates. The bioaugmentation resulted in a 50% increase in CH4 production even without any acclimation. The survival and biological activity of the added bacteria were followed in fed-batch fermenters by qPCR. Stable biogas production was observed for an extended period of time in laboratory CSTR reactors fed with biomass of low C/N.

From Batch to Continuous Chemical Synthesis—A Toolbox Approach

A toolbox approach for the transfer of batch to continuous chemical synthesis is presented. The approach considers reaction kinetics (Type A, B, C), reacting phases (single phase, liquid–liquid, gas–liquid and liquid–solid), and the reaction network (parallel and consecutive reactions) in order to select the most appropriate reactor module (Plate, Coil, or CSTR) for continuous operation. Then, three case studies using these three fundamental reactors are presented but require special considerations. For the reaction of dimethyl-oxalate with ethylmagnesium chloride, a plug-flow multi-injection technology must be used to decrease the local heat generation and improve yield. For the nitration of salicylic acid, a Plate reactor with mixing elements favoring some back-mixing followed by a plug-flow system at elevated temperatures is used instead of a tandem mixed-flow CSTR and plug-flow Coil reactor in order to minimize the risk of thermal decomposition of intermediates with a reduced volume penalty. Finally, a ring-closing metathesis reaction is discussed for which the utilization of a CSTR allows the removal of catalyst-poisoning ethylene formed during the reaction and keeps the substrate concentration low to increase the yield above that of a batch or plug-flow system.

Li(Ni1-x-yCoxMny)O2계 이차전지 공정 스크랩으로부터 회수한 전이금속을 활용한 리튬이차전지 양극재 제조

Cathode materials and their precursors are prepared with transition metal solutions recycled from the the waste lithium-ion batteries containing NCM (nickel-cobalt-manganese) cathodes by a <TEX>$H_2$</TEX> and C-reduction process. The recycled transition metal sulfate solutions are used in a co-precipitation process in a CSTR reactor to obtain the transition metal hydroxide. The NCM cathode materials (Ni:Mn:Co=5:3:2) are prepared from the transition metal hydroxide by calcining with lithium carbonate. X-ray diffraction and scanning electron microscopy analyses show that the cathode material has a layered structure and particle size of about 10 <TEX>${\mu}m$</TEX>. The cathode materials also exhibited a capacity of about 160 mAh/g with a retention rate of 93~96% after 100 cycles.

Trace element supplementation in the biogas production from wheat stillage – Optimization of metal dosing

A trace element dosing strategy for the anaerobic digestion of wheat stillage was developed in this study. Mesophilic CSTR reactors were operated with the sulfuric substrate wheat stillage in some cases under trace element deficiency. After supplementing trace elements during the start-up, one of the elements of Fe, Ni, Co, Mo, and W were depleted in one digester while still augmenting the other elements to determine minimum requirements for each element. The depletion of Fe and Ni resulted in a rapid accumulation of volatile fatty acids while Co and W seem to have a long-term effect. Based on the results it was possible to reduce the dosing of trace elements, which is positive with reference to economic and environmental aspects.

Formación acelerada de gránulos productores de hidrógeno para el arranque de reactores UASB utilizando vinazas

&lt;p&gt;Se estudió la formación de gránulos productores de hidrógeno en un reactor CSTR, con el fin de transfe­rirlos luego un reactor UASB y así acortar el tiempo de arranque del mismo. El sustrato utilizado fueron vinazas provenientes de una agroindustria nacional productora de etanol a partir de melazas de caña de azúcar y su fermentación anaerobia se llevó a cabo bajo condiciones mesofílicas. Los lodos para realizar la inoculación del sistema se tomaron de un reactor UASB de una planta de tratamiento de agua industrial, a los cuales se les realizó un tratamiento térmico con el objetivo de inhibir el crecimiento de bacterias metanogénicas. Se generaron curvas de crecimiento de materia viable y no viable total, con las cuales se determinó que la fase de crecimiento exponencial de las bacterias en cultivo mixto pre­tratadas térmicamente se encontraba entre las 20 y las 120 h. Finalmente, la fermentación anaeróbica de las vinazas durante 70 horas en modo “batch” (por lotes) y posteriormente durante 7 días en modo continuo tipo CSTR demostró ser un pro­cedimiento efectivo para acelerar la formación de los gránulos productores de hidrógeno, lográndose obtener gránulos con un tamaño promedio de 1,24 mm. La alta eficiencia del proceso se le atribuye a la elevada transferencia de masa que se obtiene en el reactor CSTR.&lt;/p&gt;

Synthesis and Characterization of Spinel-Layered Mixed Cathode Materials for Li-Ion Batteries From Ni-Mn Precursor in CSTR Reactor At Different Feeding Times

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Modeling on scale-up of an ebullated-bed reactor for the hydroprocessing of vacuum residuum

An ebullated reactor for heavy vacuum residuum (VR) hydroprocessing under a high hydrogen pressure of 15MPa and a high temperature of 425°C was simulated using a two-bubble class model. To account for the influence of the strong back-mixing of the liquid phase and the non-uniform distribution of the catalyst on the performance of the reactor, axial dispersions for the two phases are incorporated into the plug flow model. Based on the bench-scale experiments conducted in a reactor of 0.036m ID and 2.0m in height, scaling up of the reactor to an annual processing capacity of 1.0milliont of VR was proposed. To determine the optimal reactor dimension, a reactor of 3m ID and 36.86m in height and one with 4.5m ID and 16.38m in height are compared. It shows although the two reactors give very similar conversions as a CSTR reactor, the 3m ID reactor shows a higher gas–liquid mass transfer coefficient and a larger slurry circulation velocity than the 4.5m ID one, which suggests the 3m ID reactor is a better choice in the scale up.

Biogas production from wheat straw and manure – Impact of pretreatment and process operating parameters

Non-treated or steam-exploded straw in co-digestion with cattle manure was evaluated as a substrate for biogas production compared with manure as the sole substrate. All digestions were performed in laboratory-scale CSTR reactors (5L) operating with an organic loading late of approximately 2.8 g VS/L/day, independent of substrate mixture. The hydraulic retention was 25 days and an operating temperature of 37, 44 or 52°C. The co-digestion with steam exploded straw and manure was evaluated with two different mixtures, with different proportion. The results showed stable performance but low methane yields (0.13-0.21 N L CH4/kg VS) for both manure alone and in co-digestion with the straw. Straw appeared to give similar yield as manure and steam-explosion treatment of the straw did not increase gas yields. Furthermore, there were only slight differences at the different operating temperatures.

Batch and Continuous Mesophilic Anaerobic Digestion of Food Waste: Effect of Trace Elements Supplementation

Trace metals are essential for the enzyme cofactors involved in the biochemistry of methane formation and are needed in a balanced anaerobic digestion process. Food and kitchen waste generally contains low concentrations of trace elements, especially metals. As a consequence the anaerobic digestion process may result instable. The aim of this study is to evaluate the effect of metals addition on mesophilic anaerobic digestion of food waste, both in batch tests and in laboratory scale CSTR reactors. Batch anaerobic trials using source-separated food waste as substrate with inoculums of different origins were carried out under mesophilic conditions. Reactions were operated both with and without trace elements (Co, Mo, Ni, Se, W) supplementation. Supplementation with trace metals had either neutral or slightly negative effects with inoculums originating from reactors with a high background level of metals, such as those for the co-digestion of biowaste and waste activated sludge. For inoculums from reactors treating food waste only, which inherently contain low levels of trace metals, supplementation with these metals increased methane production. In particular, Mo concentrations in the range of 3-12 mg/kgTSfed and Se concentrations of 10 mg/kgTSfed increased methane production to as high as 30-40 %. Supplementation with a metal mixture (Co, Mo, Ni, Se, W) increased the methane production to the range 45-65 % for inoculums with low background concentrations of trace metals. These findings demonstrate the importance of Co, Mo, Ni, Se, W for high-performance anaerobic digestion process. Trace metals additions that showed the best batch results (100mgNi/kgTSfed, 100mgCo/kgTSfed, 6mgMo/kgTSfed, 10mgSe/kgTSfed, 10mgW/kgTSfed) were selected for CSTR experimentation. Performances of a continuous anaerobic digester fed with trace elements were compared to a “control reactor” fed with the same substrate but without metals addition. Preliminary CSTR results showed that metals addition allowed for a stable anaerobic digestion process at Organic Loading Rate greater than 3 kgVSfed m 3 •d but were not essential.

Ammonia loading rate: an effective variable to control partial nitrification and generate the anaerobic ammonium oxidation influent

Anaerobic ammonium oxidation (ANAMMOX) is an innovative process for the treatment of ammonia-contaminated waters. ANNAMOX is usually preceded by a nitrifying step in which ammonia is partially oxidized to nitrite. The effectiveness of the overall process depends on control of the nitrification and creation of a suitable influent for ANAMMOX. In this work, impacts of ammonia concentration and loading rate on partial nitrification and composition of the resulting effluent were investigated in continuous stirred tank (CSTR) and biofilm reactors fed with various ammonia concentrations (17.6–61.5 mM; 299–1045 ppm). Regardless of ammonia concentration, loading rates from 3.1 to 5.4 mM/h in the CSTR and 6.4–12.1 mM/h in the biofilm reactor generated effluents with nitrite to ammonia ratios of 1.2±0.3 (suitable ANAMMOX influent). Under these conditions, the highest ammonia loading and nitrite production rates in the CSTR and biofilm reactors were 5.4 and 2.5 mM/h (HRT: 3.7 h) and 12.1 and 6.5 mM/h (HRT: 1.6 h), respectively. Results reveal that ammonia loading rate can be used effectively to achieve suitable ANAMMOX influent without the need for precise control of dissolved oxygen (DO). Considering the difficulty in regulating DO in large-scale systems and the need for the nitrifying process to be flexible with respect to various ammonia concentrations, the loading rate appears to be a practical option to control partial nitrification. Verifying the range of ammonia loading rates that generate ANAMMOX influent allows operation of the nitrifying step with any level of ammonia in the feed, with the proper loading rate achieved through adjustment of hydraulic residence time.

Repeated Batch Biotransformation from Isoeugenol to Vanillin by Immobilized &lt;i&gt;Bacillus fusiformis&lt;/i&gt; Cells in CSTR Reactor

Bacillus fusiformis CGMCC1347, screened from soil, was immobilized successfully to biotransform isoeugenol to vanillin. The optimal immobilization conditions were 2.5% sodium alginate, 10% cell density and Ca2+ 0.1 mol l-1. The optimal reaction conditions in a 2 L CSTR reactor with immobilized Bacillus fusiformis CGMCC1347 cells were isoeugenol 600 mL, immobilized cells 400 g, pH 3.5 dH2O 400 mL, 37 oC, 200 r min-1 shaking speed and 0.8 vvm air capacity. The average vanillin concentration reached 39.26 g l-1 after 6 times reuse of immobilized cells in 2 L CSTR.

Enhancing the performance of dark fermentative hydrogen production using a reduced pressure fermentation strategy

The partial pressure of hydrogen is an extremely important factor for hydrogen generation. This study investigated the effect of reduced pressure (via vacuum) on hydrogen production in a CSTR reactor. The results show that the reduced pressure condition is more effective in enhancing H2 production at lower HRT (e.g., 8–4 h) than at higher HRT (e.g., 12 h). The optimal hydrogen yield and overall hydrogen production efficiency occurred at a HRT of 6 h with a value of 4.50 mol H2/mol sucrose and 56.2%, respectively. Meanwhile, at HRT 6 h the hydrogen production rate was 0.937 mol/L/d. In addition, the HPR could be further improved to 1.196 mol/L/d when the HRT was shortened to 4 h, obtaining a 37–271% increase in HPR when compared with that described in the relevant reports. For all experiments, butyrate and acetate were the two primary soluble metabolites, accounting for 85–99% of total soluble microbial products. Predominant production of acetate and butyrate demonstrates the efficient H2 fermentation with reduced pressure processes.

Process enhancement through waste minimization and multiobjective optimization

Abstract A simultaneous approach to maximize profit, while minimizing waste through source reduction with the implementation of multiobjective optimization with process simulation is presented in this paper. To demonstrate this methodology, the acrylonitrile process case study was selected. The approach involved four steps: process modeling and analysis, identification of process alternatives, selection of process alternatives and incorporation of multiobjective optimization. The simulator ASPEN PLUS™ 12.1 was used to model and evaluate the process. Process alternatives were identified from both literature and sensitivity analysis procedures. Sensitivity analysis helps initially in quickly eliminating inferior alternatives and then in enhancing the superior alternative to develop an efficient optimization procedure. Through this work, a general methodology was developed for the application of process optimization to process design. A sensitivity curve that shows the effect of waste treatment on the profit for the process was developed. Based on the sensitivity analysis results, the Plug Flow reactor scheme was the better alternative as compared to the base case, CSTR reactor scheme. After process modification and optimization, the process can earn a maximum net savings of $ 3.59 × 108 in seven years, an increase of 69% over the base case. At the other end of the spectrum, the modified process could generate waste of 1884 kg h−1, a 38% reduction compared to the base case. The modified optimized process is observed to show significant improvements in environmental impacts as analyzed by the Waste Reduction Algorithm.

Dynamic simulation and control of auto-refrigerated CSTR and tubular reactor for bulk styrene polymerization

Dynamic simulation and control of a two-stage continuous bulk styrene polymerization process is developed to predict the performance of auto-refrigerated CSTR and tubular reactors. The tubular reactor is subdivided into three temperature-control jacket zones. In this paper temperature control of auto-refrigerated continuous stirred tank reactor and tubular reactor are carried out, simultaneously. Two strategies are proposed for the control of tubular reactor. At the first strategy the controlled variable is jacket temperature and in the second strategy the controlled variable is the reactor temperature at the exit of each section. The set points for polymer grade transition are obtained using optimization of reactors temperatures via genetic algorithm (GA). Simulation results show that both of the control strategies are successful but second strategy has better performance in the control of polymer properties in the presence of disturbance and model mismatch.

Escherichia coli (XL1-BLUE) for continuous fermentation of bioH2 and its separation by polyimide membrane

In this work continuous hydrogen production by Escherichia coli (XL1-BLUE) and its purification by membrane gas separation were studied. Firstly, a kinetic investigation was performed on formate supplemented broth in order to determine exponential growth phase (5–7 h) while the most intense hydrogen fermentation takes place. Furthermore, important process design parameters such as saturation constant and maximal growth rate were calculated (KS = 0.77 g l−1, μmax = 0.39 h−1). Afterward, based on the kinetic study, continuous hydrogen fermentations using cultures of E. coli (XL1-BLUE) were carried out in a CSTR reactor configuration applying various hydraulic retention times (HRT) related to both exponential and stationary growth period (5 h, 7 h, 9 h). The results indicated that highest hydrogen yield (0.26 mmol H2/mmol formate added) and productivity (5.1 mmol H2 l−1 d−1) could be achieved by applying HRT = 7 h that does not allow the living cells to reach stationary phase. In addition to hydrogen production, the concentration of bioH2 by polyimide membrane under different operational circumstances was investigated using pure and mixed gases, as well. The results of single gas experiments indicated that increasing the temperature has positive effect on separation efficiency. Moreover, the influence of retentate and feed flow ratio (QR/QF) was studied applying binary H2/CO2 gaseous mixture and it was found that polyimide membrane has high potential for H2 purification since 18% increase in H2 concentration and 22% decrease in CO2 content could be attained in the permeate by a one-step separation process.