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1
Lindeque, Rowan, and John Woodley. "Reactor Selection for Effective Continuous Biocatalytic Production of Pharmaceuticals." Catalysts 9, no. 3 (March 14, 2019): 262. http://dx.doi.org/10.3390/catal9030262.
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Enzyme catalyzed reactions are rapidly becoming an invaluable tool for the synthesis of many active pharmaceutical ingredients. These reactions are commonly performed in batch, but continuous biocatalysis is gaining interest in industry because it would allow seamless integration of chemical and enzymatic reaction steps. However, because this is an emerging field, little attention has been paid towards the suitability of different reactor types for continuous biocatalytic reactions. Two types of continuous flow reactor are possible: continuous stirred tank and continuous plug-flow. These reactor types differ in a number of ways, but in this contribution, we focus on residence time distribution and how enzyme kinetics are affected by the unique mass balance of each reactor. For the first time, we present a tool to facilitate reactor selection for continuous biocatalytic production of pharmaceuticals. From this analysis, it was found that plug-flow reactors should generally be the system of choice. However, there are particular cases where they may need to be coupled with a continuous stirred tank reactor or replaced entirely by a series of continuous stirred tank reactors, which can approximate plug-flow behavior. This systematic approach should accelerate the implementation of biocatalysis for continuous pharmaceutical production.
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Molin, Paul, and Patrick Gervais. "Convergence of a series of well-stirred reactors to plug-flow reactor." AIChE Journal 41, no. 5 (May 1995): 1346–48. http://dx.doi.org/10.1002/aic.690410533.
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Allain, Florent, Jean-François Portha, and Laurent Falk. "Analysis of Equilibrium Shifting by Inter-Stage Reactant Feeding in a Series of Isothermal Reactors." International Journal of Chemical Reactor Engineering 12, no. 1 (January 1, 2014): 163–79. http://dx.doi.org/10.1515/ijcre-2013-0116.
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Abstract This paper focuses on the impact of reactant staging on conversion for one single reversible reaction in a two-stage, isothermal, continuous reactor. The analytical expression of global conversion has been derived for a series of two continuously stirred-tank reactors. Improvements in the overall conversion and yield by staging can be obtained for low Damköhler number systems leading to low conversions, when the volumetric flow rate of the staged reactant has a higher value than that of the other one. The example of triolein transesterification involving three reversible reactions in a two-stage plug flow reactor is also studied as a concrete example of a consecutive/parallel reversible reactions system. Results are obtained by using a pseudo-homogeneous model and are compared with those obtained with a heterogeneous model from a previous study.
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Azizan, Amizon, and Nornizar Anuar. "Simulating Trambouze reaction for a series reactor." Malaysian Journal of Chemical Engineering and Technology (MJCET) 3, no. 1 (November 30, 2020): 1. http://dx.doi.org/10.24191/mjcet.v3i1.10930.
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Simulating the existing data on Trambouze reaction is compiled in this article. The objective of the work is to present the change of volumetric flow rate and the inlet concentration of key reactant A in a series continuous stirred tank reactor-plug flow reactor (CSTR-PFR) configurations. The volumetric flow rate does not affect selectivity and conversion for a constant volumetric flow rate operating condition, entering CSTR and PFR, at a specific concentration of reactant. The CSTR-PFR series reactor configuration is proposed for the aim of maximizing the selectivity of the desired product B in comparison to the undesired products X and Y. CSTR as the first reactor is capable to achieve the maximum conversion at the highest selectivity of A. PFR is then proposed after CSTR in a configuration of CSTR-PFR, to allow higher conversion value to be achieved for the resulted outlet stream conditions coming out of the first reactor, CSTR. Both reactors commonly encounter a decrease in the initial concentration of A and an increase to the formation of other products. The CSTR entering volumetric flow rate influence the volume sizes needed in achieving the maximum selectivity and conversion
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Raboni, Massimo, Renato Gavasci, and Paolo Viotti. "Influence of denitrification reactor retention time distribution (RTD) on dissolved oxygen control and nitrogen removal efficiency." Water Science and Technology 72, no. 1 (April 21, 2015): 45–51. http://dx.doi.org/10.2166/wst.2015.188.
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Abstract Low concentrations of dissolved oxygen (DO) are usually found in biological anoxic pre-denitrification reactors, causing a reduction in nitrogen removal efficiency. Therefore, the reduction of DO in such reactors is fundamental for achieving good nutrient removal. The article shows the results of an experimental study carried out to evaluate the effect of the anoxic reactor hydrodynamic model on both residual DO concentration and nitrogen removal efficiency. In particular, two hydrodynamic models were considered: the single completely mixed reactor and a series of four reactors that resemble plug-flow behaviour. The latter prove to be more effective in oxygen consumption, allowing a lower residual DO concentration than the former. The series of reactors also achieves better specific denitrification rates and higher denitrification efficiency. Moreover, the denitrification food to microrganism (F:M) ratio (F:MDEN) demonstrates a relevant synergic action in both controlling residual DO and improving the denitrification performance.
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Tanthapanichakoon, Wiwut, Shinichi Koda, and Burin Khemthong. "Dynamic Simulation of Adiabatic Catalytic Fixed-Bed Tubular Reactors: A Simple Approximate Modeling Approach." ASEAN Journal of Chemical Engineering 14, no. 1 (October 23, 2014): 25. http://dx.doi.org/10.22146/ajche.49713.
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Fixed-bed tubular reactors are used widely in chemical process industries, for example, selective hydrogenation of acetylene to ethylene in a naphtha cracking plant. A dynamic model is required when the effect of large fluctuations with time in influent stream (temperature, pressure, flow rate, and/or composition) on the reactor performance is to be investigated or automatically controlled. To predict approximate dynamic behavior of adiabatic selective acetylene hydrogenation reactors, we proposed a simple 1-dimensional model based on residence time distribution (RTD) effect to represent the cases of plug flow without/with axial dispersion. By modeling the nonideal flow regimes as a number of CSTRs (completely stirred tank reactors) in series to give not only equivalent RTD effect but also theoretically the same dynamic behavior in the case of isothermal first-order reactions, the obtained simple dynamic model consists of a set of nonlinear ODEs (ordinary differential equations), which can simultaneously be integrated using Excel VBA (Visual BASIC Applications) and 4th-order Runge-Kutta algorithm. The effects of reactor inlet temperature, axial dispersion, and flow rate deviation on the dynamic behavior of the system were investigated. In addition, comparison of the simulated effects of flow rate deviation was made between two industrial-size reactors.Keywords: Dynamic simulation, 1-D model, Adiabatic reactor, Acetylene hydrogenation, Fixed-bed reactor, Axial dispersion effect
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Mitroo, Dhruv, Yujian Sun, Daniel P. Combest, Purushottam Kumar, and Brent J. Williams. "Assessing the degree of plug flow in oxidation flow reactors (OFRs): a study on a potential aerosol mass (PAM) reactor." Atmospheric Measurement Techniques 11, no. 3 (March 27, 2018): 1741–56. http://dx.doi.org/10.5194/amt-11-1741-2018.
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Abstract. Oxidation flow reactors (OFRs) have been developed to achieve high degrees of oxidant exposures over relatively short space times (defined as the ratio of reactor volume to the volumetric flow rate). While, due to their increased use, attention has been paid to their ability to replicate realistic tropospheric reactions by modeling the chemistry inside the reactor, there is a desire to customize flow patterns. This work demonstrates the importance of decoupling tracer signal of the reactor from that of the tubing when experimentally obtaining these flow patterns. We modeled the residence time distributions (RTDs) inside the Washington University Potential Aerosol Mass (WU-PAM) reactor, an OFR, for a simple set of configurations by applying the tank-in-series (TIS) model, a one-parameter model, to a deconvolution algorithm. The value of the parameter, N, is close to unity for every case except one having the highest space time. Combined, the results suggest that volumetric flow rate affects mixing patterns more than use of our internals. We selected results from the simplest case, at 78 s space time with one inlet and one outlet, absent of baffles and spargers, and compared the experimental F curve to that of a computational fluid dynamics (CFD) simulation. The F curves, which represent the cumulative time spent in the reactor by flowing material, match reasonably well. We value that the use of a small aspect ratio reactor such as the WU-PAM reduces wall interactions; however sudden apertures introduce disturbances in the flow, and suggest applying the methodology of tracer testing described in this work to investigate RTDs in OFRs to observe the effect of modified inlets, outlets and use of internals prior to application (e.g., field deployment vs. laboratory study).
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Shilton, Andy N., and Julius N. Prasad. "Tracer studies of a gravel bed wetland." Water Science and Technology 34, no. 3-4 (August 1, 1996): 421–25. http://dx.doi.org/10.2166/wst.1996.0459.
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Current rational design methods for subsurface flow wetlands idealise these systems as plug flow reactors. This assumption ignores the existence of longitudinal dispersion, short-circuiting, stagnant zones and so on. This paper reports on a series of three tracer experiments performed on a gravel bed wetland with a design hydraulic retention time of four days in order to study its hydraulic characteristics. The results present the hydraulic retention time distributions. The first tracer run using a single point inlet source had a mean time of 2.71 days. The second and third had the influent distributed across their width using an inlet manifold and yielded mean retention times of 3.47 and 3.41 days respectively. Further interpretation of these results indicates that the current plug flow assumption used in design can result in over estimation of treatment efficiency.
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Terashima, M., M. Iwasaki, H. Yasui, R. Goel, K. Suto, and C. Inoue. "Tracer experiment and RTD analysis of DAF separator with bar-type baffles." Water Science and Technology 67, no. 5 (March 1, 2013): 942–47. http://dx.doi.org/10.2166/wst.2013.584.
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This paper describes the development of a new dissolved air flotation (DAF) separator with a flow streamlining baffle to improve solid separation efficiency. The analysis of the RTD (residence time distribution) curves indicated that the parameter θ10 (dimensionless time at which 10% of tracer has discharged) increased from 0.38 for control reactor to 0.54 for the test reactor, suggesting significant reduction in short circuit flow. The RTD curves were also used to develop a compartment model for white water (rich in micro-bubbles and water flow is turbulent) and clear water (little or no air content and water flow is quiescent) zones in the reactor using a series of CSTR (continuous stirred tank reactors) and plug flow regime respectively. The proportion of the volume occupied by the white water zone was different in control and test configurations. In the test reactor, the fraction of the clear water zone was found to increase from 6 to 37%, resulting in improvement of the suspended solid (SS) removal efficiency from 97 to 99%.
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Nandi, Biswajit, Pamela Chelme-Ayala, Mark Loewen, and Mohamed Gamal El-Din. "A new compartmental model for describing the mixing behaviour in a multi-transversal jet reactor." Canadian Journal of Civil Engineering 45, no. 2 (February 2018): 125–34. http://dx.doi.org/10.1139/cjce-2017-0284.
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The axial dispersion model (ADM) and tank-in-series model (TiSM) are conventionally used for determining mixing performance of a reactor, which is generated by transverse jets in many engineering applications. The effect of transverse jets on the mixing performance is not well determined by the ADM and TiSM when the Reynolds number of the mainstream flow is higher than ∼104. In this study, this problem was solved by a dispersive compartmental model (DCM). The DCM was a modification of the conventional compartmental model by adding a dispersive nature of plug flow compartment. The results of a series of tracer studies showed that the experimental data were better matched by the DCM than by the conventional models. The effect of transverse jets on the mixing characteristics was significant when the experimental data were modelled by the DCM. The DCM could be used for practical reactors where the E-curve shows a single peak.
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Markoš, Jozef, and Alena Brunovská. "Modelling of fixed bed catalytic reactors with catalyst deactivation under constant-pattern travelling wave assumption." Collection of Czechoslovak Chemical Communications 53, no. 1 (1988): 45–55. http://dx.doi.org/10.1135/cccc19880045.
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The models of fixed bed catalytic reactors in which catalyst deactivation takes place can be significantly simplified by introducing quasi-steady state and constant-pattern travelling wave assumption. This results in faster algorithms. In the present paper the plug-flow, radial dispersion, and well-mixed regions in the series pseudohomogenous models under the above assumptions are discussed. The obtained results are compared with experimental ones in the case of hydrogenation of benzene on a nickel catalyst with thiophene as a poison (irreversible deactivation).
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Wanner, O., and E. Morgenroth. "Biofilm modeling with AQUASIM." Water Science and Technology 49, no. 11-12 (June 1, 2004): 137–44. http://dx.doi.org/10.2166/wst.2004.0824.
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AQUASIM is a computer program for the identification and simulation of aquatic systems. The program includes a one-dimensional multisubstrate and multispecies biofilm model and represents a suitable tool for biofilm simulation. The program can be used to calculate substrate removal in biofilm reactors for any user specified microbial system. One-dimensional spatial profiles of substrates and microbial species in the biofilm can be predicted. The program also calculates the development of the biofilm thickness and of the substrates and microbial species in the biofilm and in the bulk fluid over time. Detachment and attachment of microbial cells at the biofilm surface and in the biofilm interior can be considered, and simulations of sloughing events can be performed. Furthermore, AQUASIM allows pseudo two-dimensional modeling of plug flow biofilm reactors by a series of biofilm reactor compartments. The most significant limitation of the model is that it only considers spatial gradients of substrates and microbial species in the biofilm in the direction perpendicular to the substratum.
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Kovacs, Ildiko, Richard V. Jones, Krisztian Niesz, Csaba Csajagi, Bernadett Borcsek, Ferenc Darvas, and Laszlo Urge. "Automated Technology for Performing Flow-Chemistry at Elevated Temperature and Pressure." JALA: Journal of the Association for Laboratory Automation 12, no. 5 (October 2007): 284–90. http://dx.doi.org/10.1016/j.jala.2007.06.009.
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Over the past few years, a series of novel microfluidic-based instruments were developed by ThalesNano, Inc. to carry out dangerous and difficult to perform chemical reactions in a safe and fast manner, resulting in superior performance to what commercial batch reactors could provide. Importance of microfluidic devices is continuously raising, as seen there are more and more publications, applications and devices in this field expanding the borders of chemistry. Furthermore, as one of the main advantages for pharmaceutical applications, these new revolutionary reactors allow the fast, on-the-fly mode optimization of different heterogeneous reactions in a high-throughput fashion. The heart of the reactor systems is the actual reactor bed, called the CatCart system. CatCarts allow easy handling of heterogeneous catalyst or immobilized reagents without further purification of products. In addition, the shoe-box size of these reactors makes them available from laboratories to industrial applications.
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Almeida, F., F. Rocha, and A. Ferreira. "Analysis of Liquid Flow and Mixing in an Oscillatory Flow Reactor Provided with 2D Smooth Periodic Constrictions." U.Porto Journal of Engineering 4, no. 2 (October 31, 2018): 1–15. http://dx.doi.org/10.24840/2183-6493_004.002_0001.
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In this research paper the residence time distribution (RTD) was monitored for a range of fluid oscillation, frequency, amplitude and flow rate in two oscillatory flow reactors (OFR) provided with 2D smooth periodic constrictions (2D-SPC) with different designs. It was studied the axial liquid dispersion using axial dispersion model and the mixing efficiency using tank-in-series model for continuous mode. Two cases, with and without fluid oscillation, were studied and determined the optimum conditions to ensure a close plug flow, an efficient mixing and a low axial liquid dispersion. The optimum operation conditions for the two 2D-SPC designs were found. Moreover, the effect of open cross-sectional area (a) on mixing and axial dispersion was also investigated. For low cross-sectional area values the mixing is higher. It was observed that fluid oscillation increases the mixing intensity even at lower flow rates, and the axial dispersion increases as the flow rate increases.
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Nagaki, Aiichiro, Katsuyuki Hirose, Yuya Moriwaki, Masahiro Takumi, Yusuke Takahashi, Koji Mitamura, Kimihiro Matsukawa, Norio Ishizuka, and Jun-ichi Yoshida. "Suzuki–Miyaura Coupling Using Monolithic Pd Reactors and Scaling-Up by Series Connection of the Reactors." Catalysts 9, no. 3 (March 25, 2019): 300. http://dx.doi.org/10.3390/catal9030300.
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The space integration of the lithiation of aryl halides, the borylation of aryllithiums, and Suzuki–Miyaura coupling using a Pd catalyst supported by a polymer monolith flow reactor without using an intentionally added base was achieved. To scale up the process, a series connection of the monolith Pd reactor was examined. To suppress the increase in the pressure drop caused by the series connection, a monolith reactor having larger pore sizes was developed by varying the temperature of the monolith preparation. The monolithic Pd reactor having larger pore sizes enabled Suzuki–Miyaura coupling at a higher flow rate because of a lower pressure drop and, therefore, an increase in productivity. The present study indicates that series connection of the reactors with a higher flow rate serves as a good method for increasing the productivity without decreasing the yields.
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Neumaier, Jochen M., Amiera Madani, Thomas Klein, and Thomas Ziegler. "Low-budget 3D-printed equipment for continuous flow reactions." Beilstein Journal of Organic Chemistry 15 (February 26, 2019): 558–66. http://dx.doi.org/10.3762/bjoc.15.50.
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This article describes the development and manufacturing of lab equipment, which is needed for the use in flow chemistry. We developed a rack of four syringe pumps controlled by one Arduino computer, which can be manufactured with a commonly available 3D printer and readily available parts. Also, we printed various flow reactor cells, which are fully customizable for each individual reaction. With this equipment we performed some multistep glycosylation reactions, where multiple 3D-printed flow reactors were used in series.
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Papp, K., G. Christiner, H. Popelka, and M. Schwan. "High voltage series reactors for load flow control." e & i Elektrotechnik und Informationstechnik 121, no. 12 (December 2004): 455–60. http://dx.doi.org/10.1007/bf03055412.
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Dragone, Vincenza, Victor Sans, Mali H. Rosnes, Philip J. Kitson, and Leroy Cronin. "3D-printed devices for continuous-flow organic chemistry." Beilstein Journal of Organic Chemistry 9 (May 16, 2013): 951–59. http://dx.doi.org/10.3762/bjoc.9.109.
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We present a study in which the versatility of 3D-printing is combined with the processing advantages of flow chemistry for the synthesis of organic compounds. Robust and inexpensive 3D-printed reactionware devices are easily connected using standard fittings resulting in complex, custom-made flow systems, including multiple reactors in a series with in-line, real-time analysis using an ATR-IR flow cell. As a proof of concept, we utilized two types of organic reactions, imine syntheses and imine reductions, to show how different reactor configurations and substrates give different products.
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Kristanto, Dedy, and Yulius Deddy Hermawan. "Comparative Analysis Between PI Conventional and Cascade Control in Heater-PFR-Series." Reaktor 20, no. 3 (October 13, 2020): 129–37. http://dx.doi.org/10.14710/reaktor.20.3.129-137.
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The goals of this work are to compare and analyze the use of PI conventional and Cascade control configuration in heater-plug-flow-reactor-series (Heater-PFR-series) to produce benzene through the reaction of hydrodealkylation of toluene (HDA).The two control configurations were rigorously examined in UniSim dynamic simulation environment. The PI control parameters were tuned by using “autotuner” mode of UniSim. As shown in dynamic simulation study, the two control configurations with its tuning parameters gave the fast and stable responses. This study revealed that the Cascade control acted very well and its responses were better and faster than those in PI-conventional.Keywords: cascade control; dynamic simulation; PFR; PI conventional; UniSim
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Toson, Peter, Pankaj Doshi, and Dalibor Jajcevic. "Explicit Residence Time Distribution of a Generalised Cascade of Continuous Stirred Tank Reactors for a Description of Short Recirculation Time (Bypassing)." Processes 7, no. 9 (September 10, 2019): 615. http://dx.doi.org/10.3390/pr7090615.
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The tanks-in-series model (TIS) is a popular model to describe the residence time distribution (RTD) of non-ideal continuously stirred tank reactors (CSTRs) with limited back-mixing. In this work, the TIS model was generalised to a cascade of n CSTRs with non-integer non-negative n. The resulting model describes non-ideal back-mixing with n > 1. However, the most interesting feature of the n-CSTR model is the ability to describe short recirculation times (bypassing) with n < 1 without the need of complex reactor networks. The n-CSTR model is the only model that connects the three fundamental RTDs occurring in reactor modelling by variation of a single shape parameter n: The unit impulse at n→0, the exponential RTD of an ideal CSTR at n = 1, and the delayed impulse of an ideal plug flow reactor at n→∞. The n-CSTR model can be used as a stand-alone model or as part of a reactor network. The bypassing material fraction for the regime n < 1 was analysed. Finally, a Fourier analysis of the n-CSTR was performed to predict the ability of a unit operation to filter out upstream fluctuations and to model the response to upstream set point changes.
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Naméche, T., and J. L. Vassel. "New method for studying the hydraulic behaviour of tanks in series -- application to aerated lagoons and waste stabilization ponds." Water Science and Technology 33, no. 8 (April 1, 1996): 105–24. http://dx.doi.org/10.2166/wst.1996.0158.
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All attempts to modelize and wastewater treatment process must go through the imperative knowledge of its mixing characteristics. Such a knowledge calls for the realization of tracing experiments, classically one per basin; an operation that becomes rapidly tedious, especially when it has to be repeated for a series of reactors. The transfer function theory would allow to avoid such a multiplication of tracing operations. The transfer function which characterizes every system is indeed equal, under well defined initial conditions, to the Laplace transform of the distribution of residence times (R.T.D.) in this same reactor. The R.T.D. can then be calculated from the transfer function by a deconvolution process. The main interest of this method consists in the fact that, unlike the R.T.D. the transfer function can be evaluated from any input/output signals whatsoever. Thus, the hydraulic pattern of a series of reactors can be easily and, more important, individually studied by means of tracer concentrations measured during only one tracing experiment at the exit of each basin. The only difficulty in applying this method lies in the choice of the deconvolution procedure used to estimate the R.T.D. Four different methods of calculation are proposed and compared: * deconvolution by Fourier transforms. * deconvolution by multilinear regression. * deconvolution by the algebraic resolution of a set of n equations with n unknowns. * adjustment by the least-square method to an n order ARX model. The last mentioned gives the best results. This method provides, for each pond, different parameters like Peclet number, percentage of dead-space or short-circuits. From these results, correlations between dispersion numbers and other state variables can be evaluated. Finally several hydraulic models (completely-stirred, dispersive plug flow, completely mixed tanks in series) may be simulated and compared with observed R.T.D.s.
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Amaral, Andreia, Oliver Schraa, Leiv Rieger, Sylvie Gillot, Yannick Fayolle, Giacomo Bellandi, Youri Amerlinck, et al. "Towards advanced aeration modelling: from blower to bubbles to bulk." Water Science and Technology 75, no. 3 (September 29, 2016): 507–17. http://dx.doi.org/10.2166/wst.2016.365.
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Aeration is an essential component of aerobic biological wastewater treatment and is the largest energy consumer at most water resource recovery facilities. Most modelling studies neglect the inherent complexity of the aeration systems used. Typically, the blowers, air piping, and diffusers are not modelled in detail, completely mixed reactors in a series are used to represent plug-flow reactors, and empirical correlations are used to describe the impact of operating conditions on bubble formation and transport, and oxygen transfer from the bubbles to the bulk liquid. However, the mechanisms involved are very complex in nature and require significant research efforts. This contribution highlights why and where there is a need for more detail in the different aspects of the aeration system and compiles recent efforts to develop physical models of the entire aeration system (blower, valves, air piping and diffusers), as well as adding rigour to the oxygen transfer efficiency modelling (impact of viscosity, bubble size distribution, shear and hydrodynamics). As a result of these model extensions, more realistic predictions of dissolved oxygen profiles and energy consumption have been achieved. Finally, the current needs for further model development are highlighted.
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Wang, Rong Chang, Shuang Lin Dai, Yun Fei Tang, and Jian Fu Zhao. "Hydrodynamic Characteristics Assessment and Modeling of a Novel Membrane-Aerated Reactor." Advanced Materials Research 516-517 (May 2012): 763–68. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.763.
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The research study is aimed at the characterization of the hydrodynamics of a novel membrane-aerated reactor. Hydrodynamics was determined by means of impulse tracer trials in clean reactor and calculating residence time distribution (RTD) curves at different recirculation flow rates and hydraulic retention time. Thus the typical RTD curves were analyzed to calculate the average residence time, the dimensionless variance, the number of stirred tank reactors in series, and the dispersion number.The results showed that the hydraulic characteristics in the membrane-aerated reactor was essentially correlated with circulation rate. With the circulation velocity increasing, the number of stirred tank reactors in series decreased gradually, approaching to 1, while the dispersion number increased up to 0.2. It was concluded that the flow patterns within the membrane-aerated reactor are perfectly mixed under all the conditions tested. A simple correlation between the Reynolds number and the mixing was developed which can be used for design and scale-up purposes.
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Dong, Xiao-Jian, Yi-Jun He, Jia-Ni Shen, and Zi-Feng Ma. "Multi-zone parallel-series plug flow reactor model with catalyst deactivation effect for continuous catalytic reforming process." Chemical Engineering Science 175 (January 2018): 306–19. http://dx.doi.org/10.1016/j.ces.2017.10.007.
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Davies, L. C., A. Vacas, J. M. Novais, F. G. Freire, and S. Martins-Dias. "Vertical flow constructed wetland for textile effluent treatment." Water Science and Technology 55, no. 7 (April 1, 2007): 127–34. http://dx.doi.org/10.2166/wst.2007.136.
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A pulse feed vertical flow constructed wetland (VFCW) proved to be efficient in the treatment of a textile effluent being able to buffer, dilute and treat an Acid Orange (AO7) accidental discharge. The influence of the flooding level (FL) and pulse feed (PF) duration on the removal efficiencies of a VFCW was examined. Average AO7 removal efficiencies of 70% were achieved for an AO7 Inlet concentration of 700 mg l−1 applied during 15 min cycle−1 (every three hours) at a hydraulic load of 13 l m−2 cycle−1 and an FL of 21%. The VFCW was modelled by analogy with a combination of ideal reactors. The simplest combination that best reproduced the experimental results was an association of 2 reactors in series plus 1 reactor accounting the dead volumes. The model parameters helped to understand the hydrological and kinetic processes occurring in VFCW. Through the model simulation it was shown that 3 VFCW in series were enough to efficiently treat an organic mass load of 76 gAO7 m−2 day−1 in 9 hours and fulfil the discharge legislation. In this work it was possible to establish that the overall degradation kinetics was of first order.
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Narayanan, C. M. "Studies on Computer-Aided Design and Analysis of Three-Phase Semifluidized Bed Bioreactors." Chemical Product and Process Modeling 10, no. 1 (March 1, 2015): 55–70. http://dx.doi.org/10.1515/cppm-2014-0029.
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Abstract Attempts have been made to perform computer-aided analysis and simulation of the performance of a three-phase semifluidized bed bioreactor. The bioreactor is of biofilm type. Cocurrent operation with liquid (substrate solution) forming the continuous phase has been considered. Both air and feed solution are thus admitted from the bottom, the air moving up as tiny bubbles. Being semifluidized, the bioreactor is composed of a fully fluidized bed at the bottom and a packed bed at the top. The performance of the bioreactor is analysed by assuming it to be equivalent to two plug flow dispersion reactors (PFDRs) in series, each with a different value of dispersion number/axial dispersion coefficient. The performance equations (assuming dispersed flow) for both sections are written separately and then solved numerically using fourth-order Runge–Kutta method/successive over-relaxation method, based on appropriate boundary conditions. The specific case considered is the aerobic synthesis of Xanthan gum from cheese whey permeate, which follows Contois-type kinetic equation. The fractional gas holdup in both sections, height ratio of fluidized section to packed section and the semifluidization velocity are computed at the outset from selected experimental correlations (compiled from available literature). The results obtained from the developed software package, after verifying experimentally, are used to study and illustrate the performance characteristics of the bioreactor. It is observed that the three-phase semifluidized bed biofilm reactor of proposed design provides substantially large fractional conversion of substrate at large capacities, with relatively low reactor volume requirement.
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Gill, Laurence W., and Orlaith A. McLoughlin. "Solar Disinfection Kinetic Design Parameters for Continuous Flow Reactors." Journal of Solar Energy Engineering 129, no. 1 (November 15, 2005): 111–18. http://dx.doi.org/10.1115/1.2391316.
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The main UV dose-related kinetic parameters influencing solar disinfection have been investigated for the design of a continuous flow reactor suitable for a village-scale water treatment system. The sensitivities of different pathogenic microorganisms under solar light in batch processes have been compared in order to define their relative disinfection kinetics with E. coli used as a baseline organism. Dose inactivation kinetics have been calculated for small scale disinfection systems operating under different conditions such as reflector type, flow rate, process type, photocatalytic enhancement, and temperature enhancement using E. coli K-12 as a model bacterium. Solar disinfection was shown to be successful in all experiments with a slight improvement in the disinfection kinetic found when a fixed TiO2 photocatalyst was placed in the reactor. There was also evidence that the photocatalytic mechanism prevented regrowth in the post-irradiation environment. A definite synergistic solar UV∕temperature effect was noticed at a temperature of 45°C. The disinfection kinetics for E. coli in continuous flow reactors have been investigated with respect to various reflector shapes and flow regimes by carrying out a series of experiments under natural sunlight. Finally, photocatalytic and temperature enhancements to the continuous flow process have been evaluated.
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Freitas, Daiane Cristina de, Fernando Hermes Passig, Cristiane Kreutz, Karina Querne de Carvalho, Eudes José Arantes, and Simone Damasceno Gomes. "Effect of hydraulic retention time on hydrodynamic behavior of anaerobic-aerobic fixed bed reactor treating cattle slaughterhouse effluent." Acta Scientiarum. Technology 39, no. 4 (September 15, 2017): 469. http://dx.doi.org/10.4025/actascitechnol.v39i4.30995.
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The study of the hydrodynamic behavior in reactors provides characteristics of the flow regime and its anomalies that can reduce biological processes efficiency due to the decrease of the useful volume and the hydraulic retention time required for the performance of microbial activity. In this study, the hydrodynamic behavior of an anaerobic-aerobic fixed bed reactor, operated with HRT (hydraulic retention time) of 24, 18 and 12 hours, was evaluated in the treatment of raw cattle slaughterhouse wastewater. Polyurethane foam and expanded clay were used as support media for biomass immobilization. Experimental data of pulse type stimulus-response assays were performed with eosin Y and bromophenol blue, and adjusted to the single-parameter theoretical models of dispersion and N-continuous stirred tank reactors in series (N-CSTR). N-CSTR model presented the best adjustment for the HRT and tracers evaluated. RDT (residence time distribution) curves obtained with N-CSTR model in the assays with bromophenol blue resulted in better adjustment compared to the eosin Y. The predominant flow regime in AAFBR (anaerobic aerobic fixed bed reactor) is the N-CSTR in series, as well as the existence of preferential paths and hydraulic short-circuiting.
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Alaşahan, Yusuf, and Salih Tosun. "DAĞITILMIŞ SERİ REAKTÖRLERİN(DSR) GÜÇ SİSTEMLERİNE ETKİLERİ." e-Journal of New World Sciences Academy 15, no. 4 (October 31, 2020): 50–63. http://dx.doi.org/10.12739/nwsa.2020.15.4.2a0184.
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Distributed Flexible Alternating Current Transmission System (DFACTS) devices are devices that are connected in series to the transmission line and even adding reactance. Devices, also referred to as Distributed Serial Reactors (DSR), have the ability correct impedance imbalance by interfering with line parameters in the power system. In addition, voltage balancing as a result of balanced load flow enables more power transmission or more efficient use of the power system's transmission capability. For this reason, the use of the system to control its loadability without expanding its dimensions is becoming more and more widespread. In this study, the effects of DSR devices on system loadability and voltage stability and their applicability are analyzed. The analysis was carried out on the Institute of Electrical and Electronics Engineers (IEEE) 6-bus Standard system using the Power World Simulator Program. The effects of DSR on the system were investigated by performing load flow.
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Yang, Chen, Haochuang Wu, Kangjie Deng, Hangxing He, and Li Sun. "Study on Powder Coke Combustion and Pollution Emission Characteristics of Fluidized Bed Boilers." Energies 12, no. 8 (April 13, 2019): 1424. http://dx.doi.org/10.3390/en12081424.
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The fluidized reactor is widely used in a number of chemical processes due to its high gas-particle contacting efficiency and excellent performance on solid mixing. An improved numerical framework based on the multiphase particle-in-cell (MP-PIC) method has been developed to simulate the processes of gas–solid flow and chemical reactions in a fluidized bed. Experiments have been carried out with a 3-MW circulating fluidized bed with a height of 24.5 m and a cross section of 1 m2. In order to obtain the relationship between pollutant discharge and operating conditions and to better guide the operation of the power plant, a series of tests and simulations were carried out. The distributions of temperature and gas concentration along the furnace from simulations achieved good accuracy compared with experimental data, indicating that this numerical framework is suitable for solving complex gas–solid flow and reactions in fluidized bed reactors. Through a series of experiments, the factors affecting the concentration of NOx and SOx emissions during the steady-state combustion of the normal temperature of powder coke were obtained, which provided some future guidance for the operation of a power plant burning the same kind of fuel.
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Boltz, Joshua P., Bruce R. Johnson, Imre Takács, Glen T. Daigger, Eberhard Morgenroth, Doris Brockmann, Róbert Kovács, Jason M. Calhoun, Jean-Marc Choubert, and Nicolas Derlon. "Biofilm carrier migration model describes reactor performance." Water Science and Technology 75, no. 12 (March 17, 2017): 2818–28. http://dx.doi.org/10.2166/wst.2017.160.
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The accuracy of a biofilm reactor model depends on the extent to which physical system conditions (particularly bulk-liquid hydrodynamics and their influence on biofilm dynamics) deviate from the ideal conditions upon which the model is based. It follows that an improved capacity to model a biofilm reactor does not necessarily rely on an improved biofilm model, but does rely on an improved mathematical description of the biofilm reactor and its components. Existing biofilm reactor models typically include a one-dimensional biofilm model, a process (biokinetic and stoichiometric) model, and a continuous flow stirred tank reactor (CFSTR) mass balance that [when organizing CFSTRs in series] creates a pseudo two-dimensional (2-D) model of bulk-liquid hydrodynamics approaching plug flow. In such a biofilm reactor model, the user-defined biofilm area is specified for each CFSTR; thereby, Xcarrier does not exit the boundaries of the CFSTR to which they are assigned or exchange boundaries with other CFSTRs in the series. The error introduced by this pseudo 2-D biofilm reactor modeling approach may adversely affect model results and limit model-user capacity to accurately calibrate a model. This paper presents a new sub-model that describes the migration of Xcarrier and associated biofilms, and evaluates the impact that Xcarrier migration and axial dispersion has on simulated system performance. Relevance of the new biofilm reactor model to engineering situations is discussed by applying it to known biofilm reactor types and operational conditions.
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Rodgers, M., and D. Burke. "Nitrogen removal using a vertically moving biofilm system." Water Science and Technology 47, no. 1 (January 1, 2003): 71–76. http://dx.doi.org/10.2166/wst.2003.0019.
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The aim of this laboratory study was to establish the efficacy of a new experimental biofilm system for the removal of nitrogen from synthetic wastewater. The system consisted of six reactors in series: one anaerobic, one anoxic and four aerobic reactors. In both the anaerobic and anoxic reactors, a plastic cuboid module was repeatedly moved up and down in the wastewater, while being totally submerged at all times. In each of the aerobic reactors, an identical module to that used in the anaerobic and anoxic reactors was intermittently and repeatedly immersed in and lifted out of the wastewater. All the individual reactors had a bulk fluid volume of 28.2 litres and the average temperature of the wastewater was about 10°C. Each module consisted of crossflow corrugated plastic sheets with a surface area of 1.824 m2. The nitrate recycle flow from the fourth aerobic tank to the anoxic tank was twice the inflow to that tank. In the anoxic reactor, filtered COD was removed at an average rate of 2.22 kg COD/m3.d and nitrate-nitrogen was denitrified at a rate of 0.42 kg NO3-N/m3.d. The average nitrification rate in the second aerobic reactor was 0.12 kg NH4-N/m3.d. The new biofilm system was simple to construct and operate.
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Nicol, D. G., R. C. Steele, N. M. Marinov, and P. C. Malte. "The Importance of the Nitrous Oxide Pathway to NOx in Lean-Premixed Combustion." Journal of Engineering for Gas Turbines and Power 117, no. 1 (January 1, 1995): 100–111. http://dx.doi.org/10.1115/1.2812756.
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This study addresses the importance of the different chemical pathways responsible for NOx formation in lean-premixed combustion, and especially the role of the nitrous oxide pathway relative to the traditional Zeldovich pathway. NOx formation is modeled and computed over a range of operating conditions for the lean-premixed primary zone of gas turbine engine combustors. The primary zone, of uniform fuel-air ratio, is modeled as a micromixed well-stirred reactor, representing the flame zone, followed by a series of plug flow reactors, representing the postflame zone. The fuel is methane. The fuel–air equivalence ratio is varied from 0.5 to 0.7.The chemical reactor model permits study of the three pathways by which NOx forms, which are the Zeldovich, nitrous oxide, and prompt pathways. Modeling is also performed for the well-stirred reactor alone. Three recently published, complete chemical kinetic mechanisms for the C1–C2 hydrocarbon oxidation and the NOx formation are applied and compared. Verification of the model is based on the comparison of its NOx output to experimental results published for atmospheric pressure jet-stirred reactors and for a 10 atm. porous-plate burner. Good agreement between the modeled results and the measurements is obtained for most of the jet-stirred reactor operating range. For the porous-plate burner, the model shows agreement to the NOx measurements within a factor of two, with close agreement occurring at the leanest and coolest cases examined. For lean-premixed combustion at gas turbine engine conditions, the nitrous oxide pathway is found to be important, though the Zeldovich pathway cannot be neglected. The prompt pathway, however, contributes small-to-negligible NOx. Whenever the NOx emission is in the 15 to 30 ppmυ (15 percent O2, dry) range, the nitrous oxide pathway is predicted to contribute 40 to 45 percent of the NOx for high-pressure engines (30 atm), and 20 to 35 percent of the NOx for intermediate pressure engines (10 atm). For conditions producing NOx of less than 10 ppmυ (15 percent O2, dry), the nitrous oxide contribution increases steeply and approaches 100 percent. For lean-premixed combustion in the atmospheric pressure jet-stirred reactors, different behavior is found. All three pathways contribute; none can be dismissed. No universal behavior is found for the pressure dependence of the NOx. It does appear, however, that lean-premixed combustors operated in the vicinity of 10 atm have a relatively weak pressure dependence, whereas combustors operated in the vicinity of 30 atm have an approximately square root pressure dependence of the NOx.
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Pishnamazi, Mahboubeh, Ali Taghvaie Nakhjiri, Mashallah Rezakazemi, Azam Marjani, and Saeed Shirazian. "Mechanistic modeling and numerical simulation of axial flow catalytic reactor for naphtha reforming unit." PLOS ONE 15, no. 11 (November 20, 2020): e0242343. http://dx.doi.org/10.1371/journal.pone.0242343.
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Naphtha catalytic reforming (NCR) process has been of tremendous attention all over the world owing to the significant requirement for high-quality gasoline. Industrialized naphtha reforming unit at oil refineries applies a series of fixed bed reactors (FBRs) to improve the quality of the low-octane hydrocarbons and convert them to more valuable products. The prominent purpose of this research is to understand the catalytic reactor of naphtha reforming unit. For this aim, an appropriate mechanistic modeling and its related CFD-based computational simulation is presented to predict the behavior of the system when the reactors are of the axial flow type. Also, the triangular meshing technique (TMT) is performed in this paper due to its brilliant ability to analyze the results of model’s predictions along with improving the computational accuracy. Additionally, mesh independence analysis is done to find the optimum number of meshes needed for reaching the results convergence. Moreover, suitable kinetic and thermodynamic equations are derived based on Smith model to describe the NCR process. The results proved that the proceeding of NCR process inside the reactor significantly increased the concentration amount of aromatic materials, lighter ends and hydrogen, while deteriorated the concentration amount of naphthene and paraffin. Moreover, the pressure drop along the reactor length was achieved very low, which can be considered as one of the momentous advantages of NCR process.
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Sato, Chikashi, Verona Veturia Nicolae, Bharath Ramalingam, Malcolm Shields, and Hiroaki Tanaka. "Inactivation of E. coli Using Flow-Through Ultrasound and Ultraviolet Light Reactors in Series." Journal of Environmental Engineering 141, no. 11 (November 2015): 04015034. http://dx.doi.org/10.1061/(asce)ee.1943-7870.0000973.
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Sharp, R. R., A. B. Cunningham, J. Komlos, and J. Billmayer. "Observation of thick biofilm accumulation and structure in porous media and corresponding hydrodynamic and mass transfer effects." Water Science and Technology 39, no. 7 (April 1, 1999): 195–201. http://dx.doi.org/10.2166/wst.1999.0359.
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A series of flat plate, porous media reactor studies was performed to characterize the development and structure of thick biofilms in porous media and the subsequent effects on porous media hydrodynamics and mass transport variables including average pore velocity, hydrodynamic dispersivity, and (dye tracer) breakthrough curve features. Biofilms composed of either a mucoid strain of Pseudomonas aeruginosa or a non-mucoid strain of Ps. aeruginosa were established in the reactors over a 2-3 week period. Analysis of porous media biofilms was performed using a combination of image analysis, photography, microbial vital stains, enumerations, and microscopy. Bulk fluid flow and flow channel distribution in the porous media/biofilm matrix were monitored by imaging a pulse of nigrosine dye. Hydrodynamics of the systems were determined by evaluating fluorescein dye breakthrough curves. Destructive sampling of the flat plate reactors at the end of each study provided additional information on the distribution and cell density of the porous media biofilms. Imaging results indicated the creation and closure of flow channels within the biofilm/porous media matrix for both mucoid and non-mucoid strains. Both systems exhibited accelerated tracer breakthrough and slightly increased hydrodynamic dispersivity as the biofilm matrix developed. Gray scale analysis of nigrosine pulses, along with fluorescein dye studies, suggests that biofilm development transforms the flow regime within the reactor from well defined porous media flow with a symmetric breakthrough curve to a skewed breakthrough curve with accelerated time to breakthrough.
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Lloyd, B. J., C. A. Vorkas, and R. K. Guganesharajah. "Reducing hydraulic short-circuiting in maturation ponds to maximize pathogen removal using channels and wind breaks." Water Science and Technology 48, no. 2 (July 1, 2003): 153–62. http://dx.doi.org/10.2166/wst.2003.0109.
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This paper reports the impact of four sequential maturation pond interventions on the removal of thermotolerant “faecal” coliform bacteria at a full scale WSP system in tropical Colombia. Each intervention was designed to increase hydraulic retention time and was followed by continuous physico-chemical logging and meteorological monitoring, and simultaneous tracer studies to define hydraulic retention time, flow paths and dispersion. Inlet and outlet monitoring showed that, primarily due to hydraulic short-circuiting, the open maturation pond only achieved a 90% reduction in thermotolerant “faecal” coliforms. By contrast, an in-pond batch decay rate study for thermotolerant faecal coliforms showed that a 1 log (90%) reduction was achieved every 24 hours for 4 days at 26°C, so that the maximum theoretical efficiency would be a 2.6 log reduction (99.7%) if hydraulic efficiency was perfect for plug flow. The second intervention was the conversion of the maturation pond to a parallel series of three open channels to attempt to control short-circuiting and convert to plug flow. The channels raised performance to 96%. The introduction of top baffles, at the end of the first and second channels, to attempt to further reduce the effect of surface and sub-surface flow on short-circuiting, actually reduced performance to 92.64%, and were removed. The final intervention, a 2.1 m high wind break around the maturation channels raised efficiency to 98.13%; this performance is almost a half log (0.47) greater than the efficiency (95.1%) predicted from Marais' equation for a completely mixed reactor, and 0.77 log greater than recorded in the open pond. The results have fundamental implications for improving WSP efficiency, for meeting re-use guidelines, for savings in land area and improvement of design of WSPs; they also highlight short-comings in the indiscriminate use of the Marais design equation for faecal coliform removal.
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Tulun, Şevket. "Treatment of Leachate Using Up-Flow Anaerobic Sludge Blanket Reactors/Vertical Flow Subsurface Constructed Wetlands." Ecological Chemistry and Engineering S 27, no. 1 (March 1, 2020): 129–37. http://dx.doi.org/10.2478/eces-2020-0008.
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AbstractThe composition of local solid waste consists mainly of biodegradable waste with high moisture and organic content. After being landfilled, the waste decomposes through a series of combined physico-chemical and biological processes, resulting in the generation of landfill leachate. Unless treated properly, the leachate poses a serious threat to the environment and to public health. In this study, the use of an engineered system consisting of an up-flow anaerobic sludge blanket reactor and a vertical flow subsurface constructed wetland for the treatment of landfill leachate was investigated. The leachate obtained from a landfill facility in Aksaray, Turkey was fed into both systems and laboratory tests showed that, over the 6-week study period, the systems were able to efficiently remove chemical oxygen demand (88.6 %) and total nitrogen (80.7 %). The results of this study suggested that Typha angustifolia significantly increased the removal of total nitrogen. The higher ammonia removal occurred in the anaerobic system and also the removal efficiency increased in planted bed, it is presumed to be the result of the ammonia nitrogen uptake by the roots of the plant.
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Hatzell, Marta C., Kelsey B. Hatzell, and Bruce E. Logan. "Using Flow Electrodes in Multiple Reactors in Series for Continuous Energy Generation from Capacitive Mixing." Environmental Science & Technology Letters 1, no. 12 (November 10, 2014): 474–78. http://dx.doi.org/10.1021/ez5003314.
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Cambeiro, Xacobe C., Rafael Martín-Rapún, Pedro O. Miranda, Sonia Sayalero, Esther Alza, Patricia Llanes, and Miquel A. Pericàs. "Continuous-flow enantioselective α-aminoxylation of aldehydes catalyzed by a polystyrene-immobilized hydroxyproline." Beilstein Journal of Organic Chemistry 7 (October 31, 2011): 1486–93. http://dx.doi.org/10.3762/bjoc.7.172.
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The application of polystyrene-immobilized proline-based catalysts in packed-bed reactors for the continuous-flow, direct, enantioselective α-aminoxylation of aldehydes is described. The system allows the easy preparation of a series of β-aminoxy alcohols (after a reductive workup) with excellent optical purity and with an effective catalyst loading of ca. 2.5% (four-fold reduction compared to the batch process) working at residence times of ca. 5 min.
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El Hafiane, F., and B. El Hamouri. "Anaerobic reactor/high rate pond combined technology for sewage treatment in the Mediterranean area." Water Science and Technology 51, no. 12 (June 1, 2005): 125–32. http://dx.doi.org/10.2166/wst.2005.0445.
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Two high-rate, anaerobic/aerobic units were used to treat the sewage of the Institut Agronomique st Vétérinaire Hassan II (Morocco) campus in a 1,100 m2-plant designed for 1,500 e.p. and receiving 63 m3 per day. The anaerobic pre-treatment consisted of a two-step up-flow anaerobic reactor (TSUAR) comprising two reactors and one external settler all in series. The aerobic line, or post-treatment, consisted of a high-rate algal pond (HRAP) and one maturation pond in series. The system totalized a hydraulic retention time (HRT) of 9 days. A gravel filter (GF) was constructed behind the TSUAR to trap low-density particles. The TSUAR removed 80% of COD and 90% of SS within 48 h. Solids retention time in the reactors averaged 32 d with a specific sludge production of 0.28 g SS g−1 COD removed. Almost 93% of the sludge evacuated from the settler was stabilized. Specific biogas production from both reactors was 0.25 m3 kg−1 COD removed. Used in this configuration, the HRAP lost its BOD removal activity and increased its nutrients and pathogens removal capabilities (tertiary treatment). Results showed that 85% of total nitrogen and 48% of total phosphorus were removed by the HRAP. Land area requirement of this combination was less than 1 m2 per capita and filtered final effluent was of excellent quality (COD, 82 mg/l; TKN, 8.3 mg/l; total P, 2.7 mg/l, faecal coliforms, 2.4 103/100 ml and zero helminths eggs).
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Xu, Ningjin, and Don R. Collins. "Design and characterization of a new oxidation flow reactor for laboratory and long-term ambient studies." Atmospheric Measurement Techniques 14, no. 4 (April 13, 2021): 2891–906. http://dx.doi.org/10.5194/amt-14-2891-2021.
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Abstract. Oxidation flow reactors (OFRs) are frequently used to study the formation and evolution of secondary aerosol (SA) in the atmosphere and have become valuable tools for improving the accuracy of model simulations and for depicting and accelerating realistic atmospheric chemistry. Driven by rapid development of OFR techniques and the increasing appreciation of their wide application, we designed a new all-Teflon reactor, the Particle Formation Accelerator (PFA) OFR, and characterized it in the laboratory and with ambient air. A series of simulations and experiments were performed to characterize (1) flow profiles in the reactor using computational fluid dynamics (CFD) simulations, (2) the UV intensity distribution in the reactor and the influence of it and varying O3 concentration and relative humidity (RH) on the resulting equivalent OH exposure (OHexp), (3) transmission efficiencies for gases and particles, (4) residence time distributions (RTDs) for gases and particles using both computational simulations and experimental verification, (5) the production yield of secondary organic aerosol (SOA) from oxidation of α-pinene and m-xylene, (6) the effect of seed particles on resulting SA concentration, and (7) SA production from ambient air in Riverside, CA, US. The reactor response and characteristics are compared with those of a smog chamber (Caltech) and of other oxidation flow reactors: the Toronto Photo-Oxidation Tube (TPOT), the Caltech Photooxidation Flow Tube (CPOT), the TUT Secondary Aerosol Reactor (TSAR), quartz and aluminum versions of Potential Aerosol Mass reactors (PAMs), and the Environment and Climate Change Canada OFR (ECCC-OFR). Our studies show that (1) OHexp can be varied over a range comparable to that of other OFRs; (2) particle transmission efficiency is over 75 % in the size range from 50 to 200 nm, after minimizing static charge on the Teflon surfaces; (3) the penetration efficiencies of CO2 and SO2 are 0.90 ± 0.02 and 0.76 ± 0.04, respectively, the latter of which is comparable to estimates for LVOCs; (4) a near-laminar flow profile is expected based on CFD simulations and suggested by the RTD experiment results; (5) m-xylene SOA and α-pinene SOA yields were 0.22 and 0.37, respectively, at about 3 × 1011 molec. cm−3 s OH exposure; (6) the mass ratio of seed particles to precursor gas has a significant effect on the amount of SOA formed; and (7) during measurements of SA production when sampling ambient air in Riverside, the mass concentration of SA formed in the reactor was an average of 1.8 times that of the ambient aerosol at the same time.
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Dahab, M. F., and J. Kalagiri. "Nitrate removal from water using cyclically operated fixed-film bio-denitrification reactors." Water Science and Technology 34, no. 1-2 (July 1, 1996): 331–38. http://dx.doi.org/10.2166/wst.1996.0388.
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In this paper, a study of cyclically-operated fixed-film bio-denitrification to remove nitrates from drinking water is reported. The purpose of the study was to investigate the ability of these two-stage systems to remove nitrate and residual organics from treated water as compared to single-stage units. In the cyclically-operated system, the second stage (i.e. follow) reactor is operated in series with the first stage (i.e. lead) reactor. After a given period of operation, the flow regime is reversed so that the follow reactor becomes the lead one and vice versa. The active solids remaining in the follow reactor (previously the lead one) are capable of removing residual soluble organics and nitrates to levels below the concentrations provided by single-stage units. Cyclically operated fixed-film bio-denitrification reactors were found to reduce long term effluent residual organics concentrations without adverse effects on the nitrate concentrations. The system also was found to be more effective in reducing nitrates, nitrites and soluble organic concentrations in the effluent than a single-stage system operated at the same hydraulic retention times and organic loading rates.
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Coen, F., B. Petersen, P. A. Vanrolleghem, B. Vanderhaegen, and M. Henze. "Model-based characterisation of hydraulic, kinetic and influent properties of an industrial WWTP." Water Science and Technology 37, no. 12 (June 1, 1998): 317–26. http://dx.doi.org/10.2166/wst.1998.0557.
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This paper illustrates the modelling of a full-scale industrial wastewater treatment plant. First, the hydraulics of the plant were characterised by a model-based interpretation of the results of a tracer test. The plant consists of three parallel reactors. The hydraulics of each reactor could be modelled by two tanks in series with non-equal volume. These results were confirmed by calculation of the single pass residence time distribution. Also it was found that the influent flow and the recycle flow were not distributed equally to the three reactors, resulting in different loading rates. Secondly, off-line respirometric experiments were performed to characterise the influent and to determine the sludge kinetics. The same model structure could be applied to describe the influent characteristics and the biokinetics over a period of 1 year. It was found that all wastewaters could be fractionated into three fractions and that one of the fractions was acetate-like. Concentrations of the fractions changed significantly over the year. From on-line respirometric experiments the diurnal dynamics of the influent characteristics and the kinetics of the sludge were assessed. Analysis of the respirograms showed that the wastewater composition and kinetics of the sludge did not change significantly over a short-term period of 40 hours.
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Walsh, F. C. "Electrochemical technology for environmental treatment and clean energy conversion." Pure and Applied Chemistry 73, no. 12 (January 1, 2001): 1819–37. http://dx.doi.org/10.1351/pac200173121819.
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The applications of electrochemical technology in environmental treatment, materials recycling, and clean synthesis are briefly reviewed. The diversity of these applications is shown by the number of industrial sectors involved. The scale of operation ranges from microelectrodes to large industrial cell rooms. The features of electrochemical processes are summarized. Available and developing electrode designs are considered and illustrated by examples including the regeneration of chromic acid electroplating baths, metal ion removal by porous, 3-dimensional cathodes, rotating cylinder electrodes (RCEs), and a reticulated vitreous carbon (RVC) RCE. The use of performance indicators based on mass transport, electrode area, and power consumption is emphasized. Electrochemical reactors for energy conversion are considered, with an emphasis on load-leveling and proton-exchange membrane (PEM) (hydrogenoxygen) fuel cells. Ion-exchange membranes play an essential role in such reactors, and the variation of electrical resistance vs. membrane thickness is described for a series of extruded, Nafion® 1100 EW materials. The characterization of high-surface-area, platinized Nafion surfaces is also considered. The development of modular, filter-press cells as redox flow cells in electrical load-leveling applications is concisely described. Trends in electrode, membrane, and reactor design are highlighted, and the challenges for the development of improved reactors for environmental treatment are noted.
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Ibrahim, Husham T., Ali H. Al-Aboodi, and Saramad A. Abbas. "Nutrients Removal from Domestic Wastewater in Basrah City (Southern Iraq) using Combined A2/O Bio Contact Oxidation Technology." E3S Web of Conferences 65 (2018): 05001. http://dx.doi.org/10.1051/e3sconf/20186505001.
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The nutrients removal from domestic wastewater in Basrah City (Southern Iraq) by using the technology of up flow A2-O Bio Contact Oxidation with bypass flow was studied in this research. The treatment system was designed in order to treating 100 L/day of domestic wastewater by using a laboratory scale Anaerobic-Anoxic-Aerobic Moving Bed Biofilm Reactors (MBBRS) in series form with effective volume equal to 15 L, 15 L, and 30 L respectively. Kaldnes polyethylene media (K1) was used in this study in order to achieve attached biofilm process with filling ratio equal to 30% for both anaerobic anoxic MBBRS. and with filling ratio 50% for aerobic MBBR. After the biofilm was developed in the carriers the system was operated under internal recycle ratio equal to 100%. bypass ratio equal to 40%. and under 3 different external recycle ratio (25%, 50%, and 100%). The experimental results showed that the optimal value of the external recycle ratio was equal to 50 %, which the average values of removal efficiencies of COD, NH4+-N, TN and TP were equal to 98.15 %, 97.16%, 82.12%, and 93.39 % respectively. Under the condition of the optimum value of external recycle ratio the average concentration of the dissolved oxygen in both anoxic and aerobic reactors were equal to 0.151 mg/L, and 3.57 mg/L respectively, and the temperature of water wras controlled in the range of 35° C in the anaerobic reactor and in the range of 30°C in both anoxic and aerobic reactors by used temperature controlled.
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Jacobsen, J. L., H. Madsen, and P. Harremoès. "A stochastic model for two-station hydraulics exhibiting transient impact." Water Science and Technology 36, no. 5 (September 1, 1997): 19–26. http://dx.doi.org/10.2166/wst.1997.0156.
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The objective of the paper is to interpret data on water level variation in a river affected by overflow from a sewer system during rain. The simplest possible, hydraulic description is combined with stochastic methods for data analysis and model parameter estimation. This combination of deterministic and stochastic interpretation is called grey box modelling. As a deterministic description the linear reservoir approximation is used. A series of linear reservoirs in sufficient number will approximate a plug flow reactor. The choice of number is an empirical expression of the longitudinal dispersion in the river. This approximation is expected to be a sufficiently good approximation as a tool for the ultimate aim: the description of pollutant transport in the river. The grey box modelling involves a statistical tool for estimation of the parameters in the deterministic model. The advantage is that the parameters have physical meaning, as opposed to many other statistically estimated, empirical parameters. The identifiability of each parameter, the uncertainty of the parameter estimation and the overall uncertainty of the simulation are determined.
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Frassinetti, Paula, Cavalcanti Catunda, and Adrianus C. van Haandel. "Improved performance and increased applicability of waste stabilisation ponds by pretreatment in a UASB reactor." Water Science and Technology 33, no. 7 (March 1, 1996): 147–56. http://dx.doi.org/10.2166/wst.1996.0133.
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Traditionally waste stabilisation ponds (WSPs) are built as flow-through systems with an anaerobic, a facultative and one or more maturation ponds in series. The anaerobic pond can be substituted with great advantage by an upflow anaerobic sludge blanket (UASB) reactor. The practical advantages are that the required volume for the UASB reactor is much smaller than the anaerobic pond (20 to 30 times) and that the biogas in the UASB reactor is captured, so that odour problems can be eliminated. The UASB reactor is neighbour friendly and can be used in densely populated areas. The UASB reactor is more efficient than the anaerobic pond, so that the residual organic load is small and the subsequent pond configuration can be designed with the specific purpose of eliminating pathogens. By adopting a plug flow regime, the required area for a particular hygienic effluent quality can be greatly reduced. Also, since the UASB effluent has good transparency, photosynthesis in the ponds is intense and pH increases due to biological carbon dioxide consumption, accelerating the death rate of pathogens and opening the possibility of reducing nutrients: Nitrogen by desorption of gaseous NH3 and phosphorus by phosphate precipitation. The fact that an odour free system with a high quality effluent can be produced in relatively small system composed by a UASB reactor + maturation ponds, increases the applicability of this system for sewage treatment in urban areas. As operation of both UASB and ponds is very simple, several small treatment plants instead of one large central unit may be constructed. Thus a very significant of the sewerage network may be achieved.
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Suri, Saadat Ullah Khan. "Potential Impact of Computational Techniques to Express the Solid Dynamics in (Gas-Liquid-Solid) Multiphase Reactors." NUST Journal of Engineering Sciences 11, no. 2 (December 1, 2018): 63–70. http://dx.doi.org/10.24949/njes.v11i2.504.
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The computational fluid dynamics codes play a paramount role by demonstrating the system dynamics. The solid dynamics in a multiphase reactor can be analysed from (Chaos, Fractures, Clustering Discrete Element and Eulerian-Langrangian) simulation methods. The Chaos analysis is studied from pressure variation and time series. It includes the characterization of the flow region and their transition. The correlation dimension from the gas phase will describe the scale behaviour in the Chaos analysis. An effective flow model with definite investigation is obtained from this analysis. The flow regimes will be characterized by the structures variation. The volume of fluid and continuum surface force models elaborate on the fluidized bed bubble dynamics in the reactor. The bubbles formation and gasification process of (Fuel gas) are studied from parameters by including (Minimum fluidization velocity, Gas surface tension, Gas viscosity and Density). The results demonstrate the parameters which are influenced by (Particle density and Size). The investigation in time series signals for the biomass gasification process will be demonstrated from the fluidized bed hydrodynamics and system basics. The solid dynamics has been investigated by indicating a novel bubbling in biomass (Wood) in the gasification process time signals. The indication of complex signals in solid dynamics can be obtained from it simultaneously.
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Abu Reesh, Ibrahim M. "Acrylonitrile Process Enhancement through Waste Minimization: Effect of Reaction Conditions and Degree of Backmixing." Sustainability 13, no. 14 (July 15, 2021): 7923. http://dx.doi.org/10.3390/su13147923.
Full textAbstract:
Waste minimization in reactor design is an effective approach for pollution control, when compared to the traditional practice of the end-of-pipe treatment. Reactor degree of backmixing and operating conditions are important factors that determine the performance of chemical process, including environmental impact. For the purpose of waste minimization, two modeling methods were used for simulating the performance of the acrylonitrile production reactor, based on the ammoxidation of propylene. The effect of residence time, temperature, degree of backmixing on the steady-state propylene conversion, and production of waste were determined. The tanks-in-series model and the axial dispersion model were used to account for the degree of backmixing. The two main by-products in the acrylonitrile process are acetonitrile and hydrogen cyanide, which are both highly toxic waste. Extensive reactor backmixing reduces propylene conversion, especially at high temperature and residence time. Minimum acetonitrile production is favored by low residence time, high to moderate temperature, and no backmixing. Minimum hydrogen cyanide production is favored by low residence time, low temperature, and no backmixing. At 450 °C, the percentage of increase in the selectivity of acrylonitrile, with respect to hydrogen cyanide at plug-flow reactor conditions, as compared to a continuous stirred tank reactor, is 87.1, 74.3, 50.9, 30.4, and 12.4% at a residence time of 1, 2, 4, 6, and 8 s, respectively. The reactor degree of backmixing and operating conditions are important factors that affect the environmental friendliness of the acrylonitrile production process.