Reaction In Continuous Stirred Tank Reactor Research Articles

Biohydrogen Production from Molasses Wastewater Used Mixed Culture Fermentation

Hydrogen production from molasses wastewater was investigated in continuously-stirred tank reactor (CSTR). The CSTR was operated at an hydraulic retention time (HRT) of 6 hours and the temperature at 35°C. The highest gas production of 25.39 L/d using mixed culture fermentation, corresponding to a peak hydrogen production volume of 11.39 L/d were achieved in the CSTR reactor. While the variation of chemical oxygen demand (COD) ranged from 5500 to 8000 mg/L, the soluble end product system underwent a transition of fermentation type and the reactor gave fluctuating and increasing of ORP. These experimental results demonstrate that the shock-loading and micro-anaerobic circumstance are important factors for enhancing and stabilizing H2 production.

Simultaneous Biohydrogen and Bioethanol Production from Anaerobic Fermentation with Immobilized Sludge

The effects of organic loading rates (OLRs) on fermentative productions of hydrogen and ethanol were investigated in a continuous stirred tank reactor (CSTR) with attached sludge using molasses as substrate. The CSTR reactor with attached sludge was operated under different OLRs, ranging from 8 to 24 kg/m3·d. The H2 and ethanol production rate essentially increased with increasing OLR. The highest H2 production rate (10.74 mmol/h·L) and ethanol production rate (11.72 mmol/h·L) were obtained both operating at OLR = 24 kg/m3·d. Linear regression results show that ethanol production rate (y) and H2 production rate (x) were proportionately correlated and can be expressed as y = 1.5365x − 5.054 (r2 = 0.9751). The best energy generation rate was 19.08 kJ/h·L, which occurred at OLR = 24 kg/m3·d. In addition, the hydrogen yield was affected by the presence of ethanol and acetic acid in the liquid phase, and the maximum hydrogen production rate occurred while the ratio of ethanol to acetic acid was close to 1.

Biohydrogen production with anaerobic sludge immobilized by granular activated carbon in a continuous stirred-tank

A continuous stirred-tank reactor (CSTR) process with granular activated carbon (GAC) was developed for fermentation hydrogen production from molasses-containing wastewater by mixed microbial cultures. Operation at 35°C, an initial biomass of 17.74 g·L−1 and hydraulic retention time (HRT) of 6 h, the CSTR reactor presented a continuous hydrogen production ability of 5.9 L·d−1 and the biogas was free of methane throughout the experiment. Dissolved fermentation products were predominated by ethanol and acetate acid, with smaller quantities of propionic acid, butyric acid and valeric acid. It was found that GAC could make the immobilized system durable and stable in response to organic load impacting and low pH value. When the organic loading rate (OLR) ranged from 8 kgCOD/(m3d) to 4 kgCOD/(m3d), stable ethanol-type fermentation was formed, and the ethanol and acetate concentrations account for 89% of the total liquid products.

The Operation Characteristics of Biohydrogen Production in Continuous Stirred Tank Reactor with Molasses

The feasibility and operation characteristics of anaerobic fermentation biohydrogen production in a continuous stirred tank reactor (CSTR) were investigated for treating molasses wastewater. The research indicates that the reactor has the capacity of continuously producing hydrogen in an initial biomass (as volatile suspension solids) of 17.74 g/L, temperature of (35±1) °C, hydraulic retention time (HRT) of 6 h, and the reactor can start up the ethanol-type fermentation in 12 days and realize stable hydrogen production. Furthermore, the CSTR reactor enjoys a favorable stability even with an organic shock loading. When the organic loading rate (OLR) increased from 8 kg/(m3•d) to 24 kg/(m3•d), the CSTR system reached a new steady state within 9 d. The hydrogen yield and COD removal increased from 3 L and 8% to 12 L and 20% respectively with the hydrogen content of 47 %.

Effect of reactor configuration on biogas production from wheat straw hydrolysate

The potential of wheat straw hydrolysate for biogas production was investigated in continuous stirred tank reactor (CSTR) and up-flow anaerobic sludge bed (UASB) reactors. The hydrolysate originated as a side stream from a pilot plant pretreating wheat straw hydrothermally (195 °C for 10–12 min) for producing 2nd generation bioethanol [Kaparaju, P., Serrano, M., Thomsen, A.B., Kongjan, P., Angelidaki, I., 2009. Bioethanol, biohydrogen and biogas production from wheat straw in a biorefinery concept. Bioresource Technology 100 (9), 2562–2568]. Results from batch assays showed that hydrolysate had a methane potential of 384 ml/g-volatile solids (VS) added. Process performance in CTSR and UASB reactors was investigated by varying hydrolysate concentration and/or organic loading rate (OLR). In CSTR, methane yields increased with increase in hydrolysate concentration and maximum yield of 297 ml/g-COD was obtained at an OLR of 1.9 g-COD/l d and 100% (v/v) hydrolysate. On the other hand, process performance and methane yields in UASB were affected by OLR and/or substrate concentration. Maximum methane yields of 267 ml/g-COD (COD removal of 72%) was obtained in UASB reactor when operated at an OLR of 2.8 g-COD/l d but with only 10% (v/v) hydrolysate. However, co-digestion of hydrolysate with pig manure (1:3 v/v ratio) improved the process performance and resulted in methane yield of 219 ml/g-COD (COD removal of 72%). Thus, anaerobic digestion of hydrolysate for biogas production was feasible in both CSTR and UASB reactor types. However, biogas process was affected by the reactor type and operating conditions.

Biohydrogen production from pig slurry in a CSTR reactor system with mixed cultures under hyper-thermophilic temperature (70 °C)

A continuous stirred tank reactor (CSTR) (750 cm 3 working volume) was operated with pig slurry under hyper-thermophilic (70 � C) temperature for hydrogen production. The hydraulic retention time (HRT) was 24 h and the organic loading rate was 24.9 g d � 1 of volatile solid (VS). The inoculum used in the hyper-thermophilic reactor was sludge obtained from a mesophilic methanogenic reactor. The continuous feeding with active biomass (inoculum) from the mesophilic methanogenic reactor was necessary in order to achieve hydrogen production. The hyper-thermophilic reactor started to produce hydrogen after a short adapted period of 4 days. During the steady state period the mean hydrogen yield was 3.65 cm 3 g � 1 of volatile solid added. The high operation temperature of the reactor enhanced the hydrolytic activity in pig slurry and increased the volatile fatty acids (VFA) production. The short HRT (24 h) and the hyper-thermophilic temperature applied in the reactor were enough to prevent methanogenesis. No pre-treatment methods or other control methods for preventing methanogenesis were necessary. Hyper-thermophilic hydrogen production was demonstrated for the first time in a CSTR system, fed with pig slurry, using mixed culture. The results indicate that this system is a promising one for biohydrogen production from pig slurry.

Anaerobic digestion technology in poultry and livestock waste treatment — a literature review

A literature review has been undertaken to investigate the performance of the different anaerobic process configurations and operational conditions used in poultry and livestock waste treatment. The results of the extensive literature review showed that a wide range of different reactor volumes varying from 100 mL to 95 m3 were utilized in the investigation of anaerobic processing of poultry manure. Retention times studied were between 13.2 h and 91 days. Most of studies were carried out under mesophilic conditions maintained between 25 and 35 degrees C. Chemical oxygen demand (COD) removals and organic loading rate (OLR) ranged from 32 to 78%, and from 1.1 to 2.9 kg COD m(-3) day(-1), respectively. Biogas yields were achieved between 180 mL g(-1) COD added and 74 m3 day(-1) for a wide range of different reactor configurations. Up-flow anaerobic sludge blanket (UASB) seems to be a suitable process for the treatment of poultry manure wastewater and the liquid fraction of hen manure, due to its ability to maintain a sufficient amount of active biomass. The literature review showed that various reactor configurations such as fixed-film reactor, attached-film bioreactor, anaerobic rotating biological reactor, batch reactors, downflow anaerobic filter, fixed dome plant, UASB, continuously stirred tank reactor (CSTR), up-flow anaerobic filter (UAF), temperature-phased anaerobic digestion (TPAD), anaerobic hybrid reactor (AHR), and two-stage anaerobic systems are well suited to anaerobic processing of cattle manure. At both mesophilic and thermophilic conditions, high COD removals (87-95%) were achieved for treatment of cattle manure wastewaters. The COD and volatile solids (VS) reductions obtained were 37.9 to 94% and 9.6 to 92%, respectively. During the studies, OLR and retention times ranged between 0.117 and 7.3 g VS L(-1) day(-1) and between 0.5 and 140 days, respectively. In anaerobic processing of cattle manure, methane yields between 48 mmol CH4 L(-1) and 4681.3 m3 CH4 month(- 1) were found for the corresponding reactor volumes of 120 mL and 1300 m3, respectively. In anaerobic processing of swine manure, OLR ranged from 0.9 to 15.42 g VS L(-1) day(- 1) at mesophilic conditions (25-35 degrees C). The reactor volumes varied between 125 mL and 380 L. Temperature and retention times ranged from 25 to 60 degrees C, and 0.9 to 113 days, respectively. COD and VS reductions achieved were between 57 and 78% and between 34.5 and 61%, respectively. Moreover, methane yields were obtained between 22 and 360 mL CH4 g(-1) VS added. The results showed that UASB, anaerobic baffled reactors, CSTR, and anaerobic sequencing batch reactor (ASBR) were successfully utilized in anaerobic processing of swine manure at both mesophilic and thermophilic conditions.

Oxygen delignification kinetics: CSTR and batch reactor comparison

AbstractIn the past, oxygen delignification studies were mostly performed in batch reactors, whereby the caustic and dissolved oxygen concentrations are changing during the reaction. Also the lignin content and cellulose degradation of the pulp are only established at the end of an experiment when the sample is removed from the reactor. To overcome these deficiencies, a differential reactor system (called Berty reactor) has been adopted. In this continuous stirred‐tank reactor (CSTR), the dissolved oxygen concentration and the alkali concentration in the feed are kept constant, and the rate of lignin removal is determined from the dissolved lignin concentration in the outflow stream measured by UV–vis spectroscopy. The delignification rate is found to be first‐order in HexA‐free residual lignin content. The delignification rate reaction order in [NaOH] and oxygen pressure are 0.412 ± 0.060 and 0.305 ± 0.260 respectively. The activation energy is 54.5 ± 6.8 kJ/mol. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Study on methane fermentation and production of vitamin B12 from alcohol waste slurry.

We studied biogas fermentation from alcohol waste fluid to evaluate the anaerobic digestion process and the production of vitamin B12 as a byproduct. Anaerobic digestion using acclimated methanogens was performed using the continuously stirred tank reactor (CSTR) and fixed-bed reactor packed with rock wool as carrier material at 55 degrees C. We also studied the effects of metal ions added to the culture broth on methane and vitamin B12 formation. Vitamin B12 production was 2.92 mg/L in the broth of the fixed-bed reactor, twice that of the CSTR. The optimum concentrations of trace metal ions added to the culture liquid for methane and vitamin B12 production were 1.0 and 8 mL/L for the CSTR and fixed-bed reactor, respectively. Furthermore, an effective method for extracting and purifying vitamin B12 from digested fluid was developed.

The stability of a near-adiabatic Endex batch CSTR reactor

AbstractMany tens of serious incidents involving reactors occur in the developed countries each year. The disaster at the chemical plant in Bhopal, India in 1984 was particularly notable where a thermal runaway process led to more than 3000 tragic fatalities from the cloud of extremely toxic methyl isocyanate that boiled out of a storage tank. This signalled the design of special types of chemical reactors to reduce the risk of thermal runaway by planning (at the design stage) integral safety and thermal stabilization mechanisms. The Endex CSTR (continuously stirred tank reactor) proposed by Gray and Ball [3] involves a reactor in two parts with heat exchange allowed between them. The two parts of the reactor operate side by side in tandem, such that the thermal runaway of one part is offset by an endothermic reaction in the other reactor—hence the term ‘endex’.It is found that the adiabatic endex system has a large region of parameter space where the operation can be made safe. However adiabatic conditions rely on the continuous supply of reactants to the endothermic side of the reactor, for operation of the system. The risks involved are such that it is always safer to operate batch reactors in a non-adiabatic mode. Thus we consider the limiting case of the approach to adiabatic conditions where although the mathematics produces no oscillatory causes for instability, yet there is a narrow but significant area where the stable solution branch is lost and consequently a persistent and unexpected region of instability in what otherwise appears to be a simple CSTR system.

Effect of process configuration and substrate complexity on the performance of anaerobic processes

The roles of substrate complexity (molecular size of the substrate) and process configuration in anaerobic wastewater treatment were investigated to determine optimal methanogenic technology parameters. Five substrates (glucose, propionate, butyrate, ethanol, and lactate) plus a mixed waste (60% carbohydrate, 34% protein, and 6% lipids) were studied under five reactor configurations: batch-fed single-stage continuous stirred tank reactor (CSTR), continuously fed single-stage CSTR, two-phase CSTR, two-stage CSTR, and single-stage upflow anaerobic sludge blanket (UASB). The substrate feed concentration was 20,000 mg/L as COD. The solids retention time (SRT) and hydraulic retention time (HRT) in the CSTR reactors were 20 d, while HRT in the UASB was 2 d. All reactors were operated for at least 60 d (equal to 3SRT). Substrate complexity was observed to be less significant under two-phase, two-stage and UASB reactor configurations. Two-phase CSTR, two-stage CSTR, and single-stage UASB configurations yielded the lowest effluent chemical oxygen demands (130–550, 60–700, and 50–250 mg/L, respectively). The highest effluent chemical oxygen demands were detected when feeding glucose, propionate, and lactate to continuously fed single-stage CSTRs (10, 400, 9900, and 4700 mg/L COD, respectively) and to batch-fed single-stage CSTRs (11, 200, 2500, and 2700 mg/L COD, respectively). Ironically, the one stage CSTR — most commonly utilized in the field — was the worst possible reactor configuration.

High solids content miniemulsion polymerization of vinyl acetate in a continuous stirred tank reactor

The dynamics of high solids content miniemulsion polymerization of vinyl acetate produced in a continuous stirred tank reactor (CSTR), under different emulsification processes and hydrophobes were studied. In order to gain more insight into the process, a previous kinetic study in a batch reactor was performed. In addition, the rheological behavior of latexes produced by miniemulsion was compared with those obtained by conventional emulsion. From the experiments made in batch mode, it was observed that poly(vinyl acetate) or polystyrene as the sole hydrophobes were able to create miniemulsions as far as the time elapsed between sonication and polymerization was small. The same behavior was observed in the CSTR, where the feasibility of those systems to eliminate the oscillatory performance of CSTR reactors, also at high solids content was demonstrated. The sonication itself or the sole presence of hydrophobe — without sonication — was not enough to avoid the oscillatory behavior. Further, it was shown that the viscosity of miniemulsions at the beginning of the CSTR process is notably lower than emulsions, thus preventing the initial mixing and heating problems.

Comparison between conventional emulsion and miniemulsion polymerization of vinyl acetate in a continuous stirred tank reactor

The conventional emulsion and miniemulsion polymerization of vinyl acetate in a continuous stirred tank reactor (CSTR) were studied in an attempt to demonstrate the feasibility of miniemulsion polymerization as a strategy to eliminate the oscillatory behaviour of CSTR reactors, even in very unfavourable conditions. Reactions were carried out under a wide range of operating conditions. No oscillations in the time evolution of the conversion and particle number were observed in any of the miniemulsion polymerizations, while the opposite was found in most of the conventional emulsion polymerizations. Different dependencies of the emulsifier and initiator concentrations on the reaction rate and particle number were obtained for both emulsion and miniemulsion polymerizations, as a consequence of the different nucleation mechanisms. Further, almost the same average molecular weight was obtained for the emulsions and miniemulsions carried out under similar experimental conditions.

Development of a Continuous Homogeneous Metal Complex Catalyzed, Asymmetric Hydrogenation under High Pressure (270 bar)

A kinetic model and simulation as well as a continuous stirred tank reactor (CSTR) system for the synthesis of (S)-2-(4-fluorophenyl)-3-methylbutanoic acid, an important optically active intermediate in the synthesis of mibefradil (POSICOR, a new type of calcium antagonist), by asymmetric hydrogenation of 2-(4-fluorophenyl)-3-methylbut-2-enoic acid under high pressure (270 bar) are described. It was demonstrated that a continuous, homogeneous metal complex catalyzed, enantioselective hydrogenation under high pressure is not only feasible but also a very attractive possibility. Using such a CSTR system one may achieve a space-time yield of 5.0 kg/L/day. Compared to a batch mode under high pressure, the CSTR reactor system has a more favourable space-time yield, is safer, would need less investment, and allows easier temperature control.

Living Polymerisation Reactors. Part II. Theoretical and Experimental Tests on an Algorithm Which Predicts Mwds From CSTRs with Perturbed Feeds

ABSTRACT In Part 1 of this work (Gosden et al., 1996) a novel algorithm has been described for the fast calculation of complex molecular weight distributions (MWD) produced in living anionic polymerisation conducted in periodically perturbed continuous stirred tank reactor (CSTR). Here it is shown by rigorous derivation that the new formula of Gosden et al gives the correct solution of the sets of differential equations which describe living polymerisation reactions in CSTR reactors where mixing can be regarded as perfect. A numerical validation of the algorithm is also reported where computed solutions have been compared with the results obtained by traditional numerical integration methods and perfect agreement has been found. Experiments are also reported which have been carried out with a computer controlled laboratory-scale polymerisation reactor in an attempt to validate the simulation predictions. Results are presented which show that, for a simple square-pulse input perturbation in monomer and ini...

Optimum residence time (in CSTR and airlift reactor) for bacterial leaching of metals from anaerobic sewage sludge

The bacterial process of metal solubilization from sewage sludges was studied using two types of reactors: a continuously stirred tank reactor (CSTR) and an airlift reactor, with partial sludge recycling in each case. Both reactors showed similar metal solubilization efficiencies. After parameter optimization and steady state were obtained, a mean hydraulic residence time ( t ) of 0.75 day allowed 91% Cu, 94% Zn, 93% Mn, 67% Ni and 67% Cd solubilization in the CSTR while 89% Cu, 91% Zn and 82% Cd were solubilized in the airlift reactor. The equation r v = 1.23 C + 0.44, expressing the solubilization rate of Cu or Zn according to their respective concentrations, had an explained variance ( r 2) of 0.93 for t = 0.75 d . This equation applies equally to the CSTR and to the airlift, thus showing the equality of the efficiency of either reactor. A significant first order kinetic equation has been formulated for each t . These results represent a 4:1 reduction of the required t in comparison to t used in earlier work and 0.75 day is therefore an optimum mean hydraulic residence time for bacterial leaching of metals from anaerobic sewage sludge.

A continuous stirred tank reactor investigation of the gas‐phase reaction of hydroxyl radicals and toluene

AbstractA continuous stirred tank reactor (CSTR) was used to study the gas‐phase reaction between HO⋅ and toluene. HO⋅ was generated by the in situ photolysis of nitrous acid. Flow reactor operation at steady‐state conditions with a residence time of 20 min allowed investigation of primary and very rapid secondary reactions. CSTR and batch reactor experiments were also performed with selected products. Both gas‐phase and aerosol products were identified by chromatography and mass spectroscopy, with total product yields between 55 and 75% of reacted carbon. Toluene reaction products included cresols, nitrocresols, nitrotoluenes, 3,5‐dinitrotouluene, benzaldehyde, benzyl nitrate, nitrophenols, methyl‐p‐benzoquinone, glyoxal, methylglyoxal, formaldehyde, methyl nitrate, PAN, and CO. The fraction of HO⋅ methyl hydrogen abstraction was calculated to be 0.13 ± 0.04. The ratio of reaction rate constants for nitrotoluene versus cresol formation from the HO⋅‐adduct was calculated to be about 3.3 × 104. Also, the ratio of cresol formation versus O2 addition to the HO⋅‐adduct was estimated to be ≥0.5 for atmospheric conditions. Comparisons of these measurements with previous values and the implications with respect to photochemical kinetics modeling of the atmosphere are discussed.

Multiplicity, stability and dynamics for isothermal autocatalytic reactions in CSTR

Multiplicity, stability and dynamics for autocatalytic reactions of the type A⋯ → rR + ⋯ with overall rate expression r A = kC A m C R n in a continuous stirred tank reactor (CSTR) are studied. Exact multiplicity criteria are defined in the parameter space. Stability analysis shows that no periodic oscillation is possible for the system. When multiplicity occurs, some minimum of R present initially in the reactor is required in order for the high steady state to be achieved. Loci of transient extreme for product are also investigated. Multiplicity and uniqueness criteria are further compared with reported experimental data in literature.