Operation Of Continuous Stirred Tank Reactor Research Articles

A novel microbial community restructuring strategy for enhanced hydrogen production using multiple pretreatments and CSTR operation

To achieve rapid enrichment of the targeted hydrogen-producing bacterial population and reconstruction of the microbial community in the biological hydrogen-producing reactor, the activated sludge underwent multiple pretreatments using micro-aeration, alkaline treatment, and heat treatment. The activated sludge obtained from the multiple pretreatments was inoculated into the continuous stirred tank reactor (CSTR) for continuous operations. The community structure alteration and hydrogen-producing capability of the activated sludge were analyzed throughout the operation of the reactor. We found that the primary phyla in the activated sludge population shifted to Proteobacteria, Firmicutes, and Bacteroidetes, which collectively accounted for 96.69% after undergoing several pretreatments. This suggests that the multiple pretreatments facilitated in achieving the selective enrichment of the fermentation hydrogen-producing microorganisms in the activated sludge. The CSTR start-up and continuous operation of the biological hydrogen production reactor resulted in the reactor entering a highly efficient hydrogen production stage at influent COD concentrations of 4000 mg/L and 5000 mg/L, with the highest hydrogen production rate reaching 8.19 L/d and 9.33 L/d, respectively. The main genus present during the efficient hydrogen production stage in the reactor was Ethanoligenens, accounting for up to 33% of the total population. Ethanoligenens exhibited autoaggregation capabilities and a superior capacity for hydrogen production, leading to its prevalence in the reactor and contribution to efficient hydrogen production. During high-efficiency hydrogen production, flora associated with hydrogen production exhibited up to 46.95% total relative abundance. In addition, redundancy analysis (RDA) indicated that effluent pH and COD influenced the distribution of the primary hydrogen-producing bacteria, including Ethanoligenens, Raoultella, and Pectinatus, as well as other low abundant hydrogen-producing bacteria in the activated sludge. The data indicates that the multiple pretreatments and reactor's operation has successfully enriched the hydrogen-producing genera and changed the community structure of microbial hydrogen production.

Tracking Control of a Continuous Stirred Tank Reactor Using Advanced Control Algorithms

The Continuous Stirred Tank Reactor (CSTR) is a common type of industrial equipment used in chemical processes with second-order nonlinear dynamics. CSTR is a nonlinear and linked nature makes it challenging to develop a robust control with a bigger operating zone. In the process industry, a CSTR is a crucial component. It serves as a foundation for studying and controlling other chemical reactors. Good state estimation and disturbance rejection are required in industrial processes. The most important characteristic for CSTR operation is temperature. The behavior is obtained by steady-state and dynamic analysis of the model which is usually represented by a set of differential equations. An event-based Neural network, Model Predictive Control (MPC), and Model Reference Adaptive Control (MRAC) controller are presented in this work to provide robustness to the system with the added benefit of conserving energy expenditure under parameter variations and fast changing dynamics. Numerical simulations were used to confirm the controller's robustness and efficacy. In comparison to the ANN and MPC, the simulation results clearly show that the MRAC technique delivers appropriate performance in terms of process functional improvements, more flexibility, and improved system-tracking precision in control action.

Performance Monitoring of Anaerobic Digestion at Various Organic Loading Rates of Commercial Malaysian Food Waste.

Application of anaerobic digestion (AD) has become common in treating palm oil mill effluent in Malaysia; however, employing AD in treating the organic fraction of municipal solid waste (OFMSW), especially food waste, is still scarce. This study aims to characterize the commercial Malaysian food waste (CMFW) and determine its potential as sustainable bioenergy feedstock through biogas production. The sample was digested via the biomethane potential (BMP) test with the variation of organic loading rates (OLRs), ranging from 0.38 to 3.83 gCOD/L. day, under mesophilic conditions. The digestion process was further evaluated in continuous operation using a 6-L continuous stirred-tank reactor (CSTR). The kinetic properties of the process were also determined. It was found that the CMFW had a significant amount of chemical oxygen demand of 230 g/L and an acidic pH of 4.5 with the carbon to nitrogen (C/N) ratio at 121:1. A maximum methane composition of 81% was obtained at 1.92 gCOD/L in the BMP test with specific methane production (SMP) at 0.952 L. CH4/L.COD fed. The biogas production was well-fitted with the modified Gompertz model with R 2 at 0.9983 and the maximum biogas potential production rate at Rm 0.1573 L/day, whereas in the CSTR operation, a maximum methane composition of 85% was produced at OLR 6 gCOD/L. day with the SMP of 1.13 L. CH4/L.COD fed. The CSTR system was in high stability as the pH was maintained in a range of 6.6–6.7, with an alkalinity ratio of 0.28. This study indicates the CMFW is a sustainable feedstock for biogas production in Malaysia. Toward a circular economy approach, the authorities shall introduce commercial scale CMFW AD as part of managing municipal solid waste issues in Malaysia.

Analysis of Proportional Integral Derivative Controller Parameters for CSTR

Continuous Stirred Tank Reactor (CSTR) plays a vital role and presents a various scope of researchers in the field of control and chemical engineering which exhibits of highly nonlinear behaviour and has wide operating ranges. Different control methods have been implemented on CSTR to control these parameters. Tragically, in the realcase, the behaviour of the CSTR is very different from that expected ideal CSTR which leads to the outcomes of the wrong product. However, it is a challenging task for every engineer to control the CSTR.PID controller has been proposed for adjust enhanced PID parameters in a CSTR operation utilizing a weighted mix of target capacities. Streamlining of PID controller parameters is the key objective of concoction and biochemical businesses. PID controllers have restricted the working scope of procedures with effective nonlinearity. This work considers some issues in CSTR and presents the efforts of existing researchers and it comes into view as an essential new method to adjust the control parameters. This work plans to investigate the various techniques in CSTR along with its solutions and these schemes have been surveyed in this work. This survey presents the comparison of various methods for optimizing parameters in CSTR are employed and compared with certain parameters.

Forward-osmosis anaerobic-membrane bioreactors for brewery wastewater remediation

Since most of the water used for brewing becomes wastewater, the reduction of wastewater streams is of great importance for the brewing industry. Anaerobic membrane bioreactors incorporating forward osmosis membranes (FO-AnMBRs) could provide an energy-efficient solution for the treatment of brewery wastewater, while recovering water and simultaneously producing biogas. The start-up period of two lab-scale FO-AnMBRs fed with real (Rreal) and synthetic (Rsynth) brewery wastewater was assessed and compared to continuous stirred tank reactor operation without membranes. During reactor start-up, the hydraulic retention time (HRT) of the reactors was reduced from 20 to 2.5 days while increasing the organic loading rate. The CH4 production of Rsynth and Rreal increased up to nine-fold when the membranes were integrated, demonstrating the principle that FO-AnMBR can be used for brewery wastewater treatment. However, process stability decreased with decreasing HRT, possibly due to shear stress and the inadequate C/N ratio of the wastewater.

Biodiesel production using calcium‐based catalyst from venus shell: Modeling of startup production in an industrial reactor

Calcium oxide‐based catalyst was produced from Venus shell by fast fluidized bed calcination for biodiesel synthesis. The kinetics of biodiesel synthesis was found to be a pseudo‐first‐order reaction at the experimental conditions. The obtained kinetic parameters were used for modeling the startup operation of biodiesel production in an industrial continuous stirred tank reactor (CSTR). The model was found to agree well with the reagent concentration and temperature profiles in a real production practice during biodiesel production. The variations of initial temperature, initial reagent concentration in the reactor was investigated. It was found that the reagent concentration and temperature oscillated around the final steady state. From safety operation perspective, the first 4 h were found to be the most unsteady period during continuous production. The initial concentration of waste fry oil (WFO) was also found to be critical to the safe operation of CSTR. A violation of the settings for safe operation of CSTR will be triggered once the initial concentration of WFO in CSTR reaches 500 mol m−3. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13053, 2019

A Simple Monte Carlo Method for Modeling Arborescent Polymer Production in Continuous Stirred Tank Reactor

AbstractA dynamic model is developed to simulate arborescent polyisobutylene (arbPIB) production via self‐condensing vinyl copolymerization in a continuous stirred tank reactor (CSTR). A kinetic Monte Carlo algorithm is proposed that discretizes inflow and outflow separately from reaction steps. The model predicts dynamic changes in monomer and inimer (IM) concentrations, as well as , , and molecular weight distribution (MWD). The CSTR produces arbPIB with broader MWD, compared to a batch reactor using the same recipe and operation time. Predictions of and agree with a previous deterministic model. CSTR operation with high [IM] is unstable because large molecules tend to become even larger as time increases.

Optimal design of the inlet temperature based periodic operation of non-isothermal CSTR using nonlinear output frequency response functions

The periodic operation of a non-isothermal continuous stirred tank reactor (CSTR) using inlet temperature modulation is investigated in this paper. The DC component of the CSTR output concentration is optimized by tuning the modulation parameters of the inlet temperature in order to achieve a maximum conversion using a Nonlinear Output Frequency Response Functions (NOFRFs) based approach. The results show that the new approach is fast and efficient in the analysis and design of the periodic operation of CSTR and can potentially be applied to conduct the optimal design of periodic operation of other chemical engineering processes.

Evaluation of a low‐cost magnesium product for phosphorus recovery by struvite crystallization

AbstractBackgroundThe development of a cost‐effective process of struvite crystallization requires the selection of appropriate sources of alkali and magnesium. In this study, the effectiveness of two industrial grade products, MgO and Mg(OH)2, as magnesium and alkali sources to recover phosphorus as struvite were investigated and compared in a first set of experiments. Subsequently, the use of industrial Mg(OH)2 was compared in two different struvite crystallization systems, an upflow fluidized bed reactor (FBR) and a continuous stirred tank reactor (CSTR) coupled to a settler tank.ResultsAt the same operational conditions, the consumption of MgO was higher than Mg(OH)2 consumption. Moreover, industrial Mg(OH)2 consumption for FBR and the CSTR operation was 1.6 and 1.1 1 mol Mg added mol‐1 P precipitated, respectively. This difference was caused by the high mixing intensity and the higher contact time between the Mg(OH)2 slurry and the influent in the CSTR, favouring the conversion.ConclusionsBoth industrial grade magnesium products are promising options for struvite crystallization. However, Mg(OH)2 was more effective than the starting material, MgO, to recover phosphorus. Struvite crystallization by adding an industrial grade Mg(OH)2 could be economically viable with regard to alternative physico‐chemical P removal processes using metal salts, increasing the attractiveness of this P recovery process. © 2017 Society of Chemical Industry

Start-up and operation of continuous stirred-tank reactor for biohydrogen production from restaurant organic solid waste

The hydrogen production from a variety of substrates, including organic solid waste (OSW), has been studied at different organic loading rate (OLR), finding different behavior on the hydrogen production rate (HPR) that can be related to the particular waste characteristics and particular operational conditions. The objective of this study was to evaluate the start-up and operation of a continuous stirred-tank reactor (CSTR) to generate hydrogen from food waste applying different OLR in order to determine the operational conditions to obtain the maximal HPR. Three OLR, controlled via the influent flow rate, were studied: 19, 38 and 57 gVS/Lreactor/d. It was found that the OLR has an influence on the hydrogen production in the CSTR. The increase of OLR results in a decrease of COD removal, protein removal, and hydrogen yield (YH2). The highest HPR (19.8 mmol H2/Lreactor/d) and YH2 (0.6 mmol H2/gVS) were obtained at the OLR of 37.1 and 19.8 gVS/Lreactor/d, respectively. The H2 percentage in biogas had variations between 25 and 55% independently of the OLR. The VS and COD removal efficiencies were 51 ± 9% and 27 ± 9% respectively. Acetic acid was the principal VFA produced during the CSTR operation.

Treatment of Nitrate-Rich Saline Effluent by Using Citrate-Rich Waste as Carbon Source and Electron Donor in a Single-Stage Activated Sludge Reactor

Disposing of nitrate-containing effluents from seawater-fed intensive aquacultural applications is a major environmental problem. A possible solution is to mix nitrate-rich effluents from marine recirculating aquaculture systems (RASs) with citrate-rich liquid wastes (CLW), a common by-product of the food industry. Where possible, such strategy can alleviate two environmental problems simultaneously, in a cost-effective fashion. However, concerns are often raised regarding secondary pollution stemming from the use of CLW, particularly related to phosphorus and heavy metals. This work showed that both phosphorus and heavy metal were completely absorbed by the bacterial sludge generated in the process, indicating low environmental risk associated with the disposal of the treated effluent to the environment. Operation of continuous stirred-tank reactor (CSTR) single-sludge denitrification reactor with CLW as electron and carbon donor resulted in high nitrate removal efficiency (>95 %) and denitrification rate of up to 1.6 g NO3-N L−1 reactor day−1 along with low bacterial biomass yield [0.23 g chemical oxygen demand (COD) new cells g−1 COD citrate]. Moreover, the use of CLW was found to be environmentally safe and equally efficient to the use of traditional, costly carbon sources such as methanol and acetic acid, rendering this alternative attractive for treatment of nitrate-rich saline effluents.

Non-sterile bio-hydrogen fermentation from food waste in a continuous stirred tank reactor (CSTR): Performance and population analysis

Bio-hydrogen production from food waste by anaerobic mixed cultures was conducted in a continuous stirred tank reactor (CSTR). The hydraulic retention time (HRT) was optimized in order to maximize hydrogen yield (HY) and hydrogen production rate (HPR). The maximum hydrogen content (38.6%), HPR (379 mL H2/L. d) and HY (261 mL H2/g-VSadded) were achieved at the optimum HRT of 60 h. The major soluble metabolite products were butyric and acetic acids which indicated a butyrate-acetate type fermentation. Operation of CSTR at HRT 60 h could select hydrogen producing bacteria and eliminate lactic acid bacteria and acetogenic bacteria. The microbial community analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) revealed that the predominant hydrogen producer was Clostridium sp.

Anaerobic monodigestion of poultry manure: determination of operational parameters for CSTR

In this work the anaerobic monodigestion for the treatment of turkey manure was evaluated, without its codigestion with another substrate. The effect of the organic loading rate (OLR) and the substrate concentration (high total solids (TS) concentration) or product concentration (high volatile fatty acids (VFA) and/or ammonia (NH(3)-N) concentrations) was studied. The results show that for a continuous stirred tank reactor (CSTR) operation, a maximum of 40 g/L of TS and 4.0 g/L of ammonium (NH(4)(+)) was required. In addition, the maximum organic loading rate (OLR) will not exceed 1.5 kg VS/m(3)d. Higher TS and NH(4)(+) concentrations and OLR lead to a reduction on the methane productivity and volatile solids (VS) removal. During the CSTR operation, a high alkalinity concentration (above 10 g/L CaCO(3)) was found; this situation allowed maintaining a constant and appropriate pH (close to 7.8), despite the VFA accumulation. In this sense, the alkalinity ratio (α) is a more appropriate control and monitoring parameter of the reactor operation compared to pH. Additionally, with this parameter a VS removal of 80% with a methane productivity of 0.50 m(3)(CH4)/m(3)(R)d is achieved.

Continuous hydrogen production from tofu processing waste using anaerobic mixed microflora under thermophilic conditions

We carried out continuous fermentative H 2 production from tofu (soybean curd)–processing waste (TPW) using anaerobic mixed microflora under thermophilic (60 °C) conditions and compared the rates and yields of H 2 production in a continuous stirred-tank reactor (CSTR) and a membrane bioreactor (MBR), wherein the membrane filtration unit was coupled to the CSTR. The TPW was diluted with tap water and then hydrolyzed by blending for 5 min in the presence of 0.5% HCl, and it was found that this protocol significantly increased the amount of soluble material in the mixture. The soluble chemical oxygen demand (SCOD)–to–total COD (TCOD) ratio jumped from 14% to 60%, and the soluble carbohydrate concentration was increased threefold, from 2.4 g/L to 7.2 g/L. Accordingly, H 2 production potential was increased 2.8-fold. In a CSTR operation using pretreated TPW as the substrate, a stable volumetric H 2 production rate (VHPR) of 8.17 ± 0.32 L H 2/L/d and a H 2 yield of 1.20 ± 0.05 mol H 2/mol hexose added at 8-h HRT were achieved. Substantial increases in the VHPR and H 2 yield over those obtained with the CSTR were observed in the MBR operation. The role of the MBR was to increase the retention time of the solid substrate and the concentration of microorganisms, thereby enhancing the substrate utilization rate for H 2 production. Acetic and butyric acids were the main liquid-state metabolites produced during the fermentation process, thus indicating that the thermophilic operation provided favorable conditions for H 2 production from TPW. A maximum H 2 yield of 1.87 mol H 2/mol hexose added was achieved at 8-h HRT and then gradually decreased to 1.00 mol H 2/mol hexose-equivalent at 2-h HRT. Meanwhile, the VHPR continuously increased to a maximum of 19.86 L H 2/L/d at 4-h HRT and then decreased with a high dilution rate as the HRT was lowered to 2 h (minimum). At 2-h HRT, the degradation of soluble carbohydrate was limited.

Effect of organic loading rate on fermentative hydrogen production from continuous stirred tank and membrane bioreactors

Abstract The influence of organic loading rates (OLRs) on the performance of fermentative hydrogen-producing bioreactors operating in continuous stirred tank reactor (CSTR) and membrane bioreactor (MBR) modes was examined. Five OLRs were examined, ranging from 4.0 to 30 g COD L −1 d −1 , with influent glucose concentrations ranging from 1.3 to 10 g COD L −1 . At OLRs up to 13 g COD L −1 d −1 , all influent glucose was utilized and the H 2 yield was not significantly influenced by OLR, although the yield in the CSTR mode was significantly higher than that in the MBR mode, 1.25 versus 0.97 mol H 2 (mol Gluc. Conv.) −1 , respectively. At an OLR of 30 g COD L −1 d −1 , both reactor modes were overloaded with respect to glucose utilization and also had significantly higher H 2 yields of 1.77 and 1.49 mol H 2 (mol Gluc. Conv.) −1 for the CSTR and MBR modes, respectively, versus the underloaded operation. At the intermediate OLR of 22 g COD L −1 d −1 , the H 2 yield was maximized at 1.78 mol H 2 (mol Gluc. Conv.) −1 for both the CSTR and MBR operation. Overall H 2 production was 50% higher in the MBR mode, 0.78 versus 0.51 moles d −1 , because the CSTR mode was overloaded with respect to glucose utilization at this OLR. These results suggest that an optimum OLR that maximizes H 2 yield and H 2 production may be near the OLR that causes overload with respect to substrate utilization. Additionally, while the CSTR mode is easier to operate and provides higher H 2 yields at underloaded and overloaded OLRs, the MBR mode may be preferable when operating near the optimum OLR.

Mediating operation of catalytic CSTR to stabilize intermediate steady state

AbstractA novel approach for stabilizing the intermediate steady state of a continuous stirred‐tank reactor (CSTR) is proposed by using a special type of periodic forced operation, the so‐called mediating operation. The mediating operation enables new additional steady states for which one of the new intermediate steady states is stable to be produced. Thus the proposed approach employs a periodic forcing for stabilization of a selected steady state by control of a steady‐state multiplicity. The feed flow rate is considered to be a manipulated variable. Changing CSTR multiplicity is investigated for two‐step control inputs. It is shown, analytically, that under two‐step control CSTR can exhibit at most five steady states with a stable intermediate steady state. A constructive procedure is proposed for finding control parameters corresponding to maximal multiplicity, that is, for stabilizing an intermediate steady state by two‐step control.

Continuous production of gluconic acid and sorbitol from Jerusalem artichoke and glucose using an oxidoreductase of Zymomonas mobilis and inulinase

Gluconic acid and sorbitol were simultaneously produced from glucose and Jerusalem artichoke using a glucose-fructose oxidoreductase of Zymomonas mobilis and inulinase. Inulinase was immobilized on chitin by cross-linking with glutaraldehyde. Cells of Z. mobilis permeabilized with toluene were coimmobilized with chitin-immobilized inulinase in alginate beads. The optimum amounts of both chitin-immobilized inulinase and permeabilized cells for coimmobilization were determined, and operational conditions were optimized. In a continuous stirred tank reactor operation, the maximum productivities for gluconic acid and sorbitol were about 19.2 and 21.3 g/L/h, respectively, at the dilution rate of 0.23 h(-1) and the substrate concentration of 20%, but operational stability was low because of the abrasion of the beads. As an approach to increase the operational stability, a recycle packed-bed reactor (RPBR) was employed. In RPBR operation, the maximum productivities for gluconic acid and sorbitol were found to be 23.4 and 26.0 g/L/h, respectively, at the dilution rate of 0.35 h(-1) and the substrate concentration of 20% when the recirculation rate was fixed at 900 mL/h. Coimmobilized enzymes were stable for 250 h in a recycle packed-bed reactor without any loss of activity, while half-life in a continuous stirred tank reactor (CSTR) was observed to be about 150 h.

Mixing effects in the bromination of resorcin

The product distribution from the bromination of resorcin (m-dihydroxybenzene) is influenced by mixing in an experimentally convenient range of concentration and mixing intensity at room temperature. The degree of bromination is insensitive to mixing, a fact which can be explained chemically. Similarly explicable is the high sensitivity of the composition of the isomeric dibromoresorcins; the % 2,4-dibromoresorcin formed has been used to characterise mixing in semi-continuous and continuous stirred tank reactor operation. In the latter case the influences of the concentration and flow rate of the feed, turbine speed and feed positions near the turbine were investigated. Although full reaction kinetics are not available, these reactions are fast and sensitive enough to study micromixing.

Continuous Cellulase Production

AbstractTrichoderma viride QM 9414 growth characteristics on glucose were investigated in single stage continuous stirred tank reactor operation and growth parameters μmax, Ks, QO2 identified. Multistage stirred tank fermentors in series with the first stage utilizing glucose and the subsequent stages utilizing cellulose yielded results in general agreement with theoretical predictions. Significant increase in enzyme productivity over single stage fermentation was obtained in multistage operation.