Stirring and Stirred‐Tank Reactors

Nienow, Alvin W.

doi:10.1002/cite.201400087

Cited by 53 publications

(33 citation statements)

References 52 publications

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“…This means that there is minor formation of internal structures when the liquid is at rest, which is why the process may be suitable for intermittent mixing. In addition, the risk of cavern-formation around the impeller and the presence of stagnant zones is low at low yield stress conditions [38].…”

Section: Viscositymentioning

confidence: 99%

Viscosity dynamics and the production of extracellular polymeric substances and soluble microbial products during anaerobic digestion of pulp and paper mill wastewater sludges

Ekstrand

Svensson

Šafarič

et al. 2019

Bioprocess Biosyst Eng

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The production processes of the pulp and paper industry often run in campaigns, leading to large variations in the composition of wastewaters and waste sludges. During anaerobic digestion (AD) of these wastes, the viscosity or the production of extracellular polymeric substances (EPS) and soluble microbial products (SMP) may be affected, with the risk of foam formation, inefficient digester mixing or poor sludge dewaterability. The aim of this study was to investigate how viscosity and production of EPS and SMP during long-term AD of pulp and paper mill sludge is affected by changes in organic loading rate (OLR) and hydraulic retention time (HRT). Two mesophilic lab-scale continuous stirred tank reactors (CSTRs) were operated for 800 days (R1 and R2), initially digesting only fibre sludge, then co-digesting fibre sludge and activated sludge. The HRT was lowered, followed by an increase in the OLR. Reactor fluids were sampled once a month for rheological characterization and analysis of EPS and SMP. The production of the protein fraction of SMP was positively correlated to the OLR, implicating reduced effluent qualities at high OLR. EPS formation correlated with the magnesium content, and during sulphate deficiency, the production of EPS and SMP increased. At high levels of EPS and SMP, there was an increase in viscosity of the anaerobic sludges, and dewatering efficiency was reduced. In addition, increased viscosity and/or the production of EPS and SMP were important factors in sludge bulking and foam formation in the CSTRs. Sludge bulking was avoided by more frequent stirring.

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Section: Viscositymentioning

confidence: 99%

Viscosity dynamics and the production of extracellular polymeric substances and soluble microbial products during anaerobic digestion of pulp and paper mill wastewater sludges

Ekstrand

Svensson

Šafarič

et al. 2019

Bioprocess Biosyst Eng

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“…The stirred tank reactor (STR) has been the dominant vessel of choice in the biotechnology industry since its inception (Nienow, ). It offers good liquid mixing as well as a decent gas‐to‐liquid mixing in systems where the volumetric gas input is relatively modest (Nienow and Wisdom, ).…”

Section: Introductionmentioning

confidence: 99%

Mixing and mass transfer in a pilot scale U‐loop bioreactor

Petersen

Villadsen

Jørgensen

et al. 2016

Biotech & Bioengineering

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A system capable of handling a large volumetric gas fraction while providing a high gas to liquid mass transfer is a necessity if the metanotrophic bacterium Methylococcus capsulatus is to be used in single cell protein (SCP) production. In this study, mixing time and mass transfer coefficients were determined in a 0.15 m forced flow U-loop fermenter of a novel construction. The effect on the impeller drawn power when a gas was introduced into the system was also studied. Mixing time decreased and mass transfer increased with increasing volumetric liquid flow rate and specific power input. This happened also for a large volume fraction of the gas, which was shown to have only minor effect on the power drawn from the pump impeller. Very large mass transfer coefficients, considerably higher than those obtainable in an STR and previous tubular loop reactors, could be achieved in the U-loop fermenter equipped with static mixers at modest volumetric liquid and gas flow rates. Biotechnol. Bioeng. 2017;114: 344-354. © 2016 Wiley Periodicals, Inc.

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“…The stirred tank reactor is the most frequently used in process industries [66] to bring about an excellent solid-liquid, gas-liquid or gas-solid-liquid contact. The adequate degree of suspension of solid particles mean homogenization of slurry so formed or a near homogenization such that the suspension ensures uniform process conditions leading to predictable results.…”

Section: Chemical-industrial Reactor Designmentioning

confidence: 99%

Industrial Manufacturing of Aqueous Solutions of Sodium Sulfhydrate (NaHS 43%) in a Multi-Phase Reactor

Reátegui-Romero¹,

Castillejo-Melgarejo²,

King-Santos³

2019

TOCENGJ

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Background:This research deals with the manufacture of sodium sulphides and sodium sulfhydrate in an isothermal multiphase chemical reactor to produce concentrated aqueous solutions of sodium sulfhydrate (greater than 43%) through Gas-Liquid-Solid reactions from hydrogen sulfide and hydroxide of sodium at 50%. Methods:A method is proposed that integrates the recovery of hydrogen sulfide from an industrial chemical process where the H 2 S gas is generated as a sub product, the strategy of the developed process was integrated into a manufacturing plant of dithiophosphoric acids (ADTF) where it was possible to recover the hydrogen sulfide in the form of an aqueous solution of NaHS with a concentration higher than 43%. Results:The experimental tests showed that the biphasic reaction mixture formed by Na 2 S, NaHS and H 2 O with global compositions of 13.3%; 26.9% and 59.7% respectively, is appropriate to obtain 43% sodium sulfhydrate in a stirred tank reactor, operated at temperatures ranging from 50°C to 55°C, where gaseous hydrogen sulfide is continually bubbled. Conclusion:Sodium sulfide (specifically Na 2 S.5H 2 O crystals) of the biphasic mixture is produced from a solution of sodium sulfhydrate (43% NaHS) and aqueous sodium hydroxide (50% NaOH). The environmental problem generated by the H 2 S was solved with a 90% recovery in the multiphase reactor and 5% in the safety absorber.

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Stirring and Stirred‐Tank Reactors

Cited by 53 publications

References 52 publications

Viscosity dynamics and the production of extracellular polymeric substances and soluble microbial products during anaerobic digestion of pulp and paper mill wastewater sludges

Viscosity dynamics and the production of extracellular polymeric substances and soluble microbial products during anaerobic digestion of pulp and paper mill wastewater sludges

Mixing and mass transfer in a pilot scale U‐loop bioreactor

Industrial Manufacturing of Aqueous Solutions of Sodium Sulfhydrate (NaHS 43%) in a Multi-Phase Reactor

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