Analysis of Equilibrium Shifting by Inter-Stage Reactant Feeding in a Series of Isothermal Reactors

2014 ◽  
Vol 12 (1) ◽  
pp. 163-179
Author(s):  
Florent Allain ◽  
Jean-François Portha ◽  
Laurent Falk
Keyword(s):  
Flow Reactor ◽  
Homogeneous Model ◽  
Plug Flow ◽  
Volumetric Flow Rate ◽  
Continuous Reactor ◽  
Two Stage ◽  
Heterogeneous Model ◽  
Number Systems ◽  
Reversible Reactions ◽  
The Impact

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.

Optimisation of CO Turndown for an Axially Staged Gas Turbine Combustor

2020 ◽  
Author(s):  
Jacob E. Rivera ◽  
Robert L. Gordon ◽  
Mohsen Talei ◽  
Gilles Bourque
Keyword(s):  
Residence Time ◽  
Parametric Study ◽  
Gas Turbines ◽  
Flow Reactor ◽  
Operating Conditions ◽  
Independent Effect ◽  
Inlet Temperature ◽  
Operating Characteristics ◽  
Two Stage ◽  
The Impact

Abstract This paper reports on an optimisation study of the CO turndown behaviour of an axially staged combustor, in the context of industrial gas turbines (GT). The aim of this work is to assess the optimally achievable CO turndown behaviour limit given system and operating characteristics, without considering flow-induced behaviours such as mixing quality and flame spatial characteristics. To that end, chemical reactor network modelling is used to investigate the impact of various system and operating conditions on the exhaust CO emissions of each combustion stage, as well as at the combustor exit. Different combustor residence time combinations are explored to determine their contribution to the exhaust CO emissions. The two-stage combustor modelled in this study consists of a primary (Py) and a secondary (Sy) combustion stage, followed by a discharge nozzle (DN), which distributes the exhaust to the turbines. The Py is modelled using a freely propagating flame (FPF), with the exhaust gas extracted downstream of the flame front at a specific location corresponding to a specified residence time (tr). These exhaust gases are then mixed and combusted with fresh gases in the Sy, modelled by a perfectly stirred reactor (PSR) operating within a set tr. These combined gases then flow into the DN, which is modelled by a plug flow reactor (PFR) that cools the gas to varying combustor exit temperatures within a constrained tr. Together, these form a simplified CRN model of a two-stage, dry-low emissions (DLE) combustion system. Using this CRN model, the impact of the tr distribution between the Py, Sy and DN is explored. A parametric study is conducted to determine how inlet pressure (Pin), inlet temperature (Tin), equivalence ratio (ϕ) and Py-Sy fuel split (FS), individually impact indicative CO turndown behaviour. Their coupling throughout engine load is then investigated using a model combustor, and its effect on CO turndown is explored. Thus, this aims to deduce the fundamental, chemically-driven parameters considered to be most important for identifying the optimal CO turndown of GT combustors. In this work, a parametric study and a model combustor study are presented. The parametric study consists of changing a single parameter at a time, to observe the independent effect of this change and determine its contribution to CO turndown behaviour. The model combustor study uses the same CRN, and varies the parameters simultaneously to mimic their change as an engine moves through its steady-state power curve. The latter study thus elucidates the difference in CO turndown behaviour when all operating conditions are coupled, as they are in practical engines. The results of this study aim to demonstrate the parameters that are key for optimising and improving CO turndown.

scholarly journals Impact of Host Heterogeneity on the Efficacy of Interventions to ReduceStaphylococcus aureusCarriage

2015 ◽  
Vol 37 (2) ◽  
pp. 197-204 ◽  
Author(s):  
Qiuzhi Chang ◽  
Marc Lipsitch ◽  
William P. Hanage
Keyword(s):  
Bacterial Infections ◽  
Homogeneous Model ◽  
Healthcare Setting ◽  
Host Population ◽  
Intervention Strategies ◽  
Control Measures ◽  
Heterogeneous Model ◽  
The Impact ◽  
Carriage Prevalence ◽  
Host Heterogeneity

BACKGROUNDStaphylococcus aureusis a common cause of bacterial infections worldwide. It is most commonly carried in and transmitted from the anterior nares. Hosts are known to vary in their proclivity forS. aureusnasal carriage and may be divided into persistent carriers, intermittent carriers, and noncarriers, depending on duration of carriage. Mathematical models ofS. aureusto predict outcomes of interventions have, however, typically assumed that all individuals are equally susceptible to colonization.OBJECTIVETo characterize biases created by assuming a homogeneous host population in estimating efficacy of control interventions.DESIGNMathematical model.METHODSWe developed a model ofS. aureuscarriage in the healthcare setting under the homogeneous assumption as well as a heterogeneous model to account for the 3 types ofS. aureuscarriers. In both models, we calculated the equilibrium carriage prevalence to predict the impact of control measures (reducing contact and decolonization).RESULTSThe homogeneous model almost always underestimatesS. aureustransmissibility and overestimates the impact of intervention strategies in lowering carriage prevalence compared to the heterogeneous model. This finding is generally consistent regardless of changes in model setting that vary the proportions of various carriers in the population and the duration of carriage for these carrier types.CONCLUSIONSNot accounting for host heterogeneity leads to systematic and substantial biases in predictions of the effects of intervention strategies. Further understanding of the clinical impacts of heterogeneity through modeling can help to target control measures and allocate resources more efficiently.Infect. Control Hosp. Epidemiol.2016;37(2):197–204

scholarly journals Simulating Trambouze reaction for a series reactor

2020 ◽  
Vol 3 (1) ◽  
pp. 1
Author(s):  
Amizon Azizan ◽  
Nornizar Anuar
Keyword(s):  
Flow Rate ◽  
Coming Out ◽  
Flow Reactor ◽  
Plug Flow ◽  
Volumetric Flow Rate ◽  
Continuous Stirred Tank Reactor ◽  
Maximum Conversion ◽  
Outlet Stream ◽  
Continuous Stirred Tank ◽  
Flow Rate Influence

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

scholarly journals Nanostructured catalysts for BIOEthanol transformation to industrially important chemicals

2021 ◽  
Vol 14 (1) ◽  
pp. 66-78
Author(s):  
Blažej Horváth ◽  
Matúš Petrík ◽  
Dana Gašparovičová ◽  
Tomáš Soták
Keyword(s):  
Flow Reactor ◽  
Low Cost ◽  
Plug Flow ◽  
Value Added ◽  
Nanostructured Catalysts ◽  
Product Distribution ◽  
Catalytic Transformation ◽  
Basic Catalysts ◽  
Acid Catalyzed ◽  
The Impact

Abstract Utilization of a low-cost biomaterial, such as bioethanol, to produce value–added compounds for current industry has been investigated. This work is focused on the catalytic transformation of bioethanol into industrially significant alkenes. Catalytic transformation of ethanol was studied using catalysts based mainly on nanostructured materials as Mg-Al hydrotalcites, sepiolites and zeolites doped with Cu, K, Sr, Zn and Mn. The catalytic tests were carried out in a plug-flow reactor in the temperature range of 350—550 °C. Undoped zeolites promote acid-catalyzed dehydration of ethanol, while in case of basic catalysts, such as hydrotalcites, the product distribution is shifted toward butadiene. The impact of the hydrotalcites preparation method on their structure and catalytic activity is reported. It was found that hydrotalcite with well-developed layered structure, prepared by slow hydrolysis, promotes the formation of butadiene (with butadiene yield of 28.2 % at 400 °C vs. ethylene yield of 17.2 % at 550 °C).

scholarly journals Impact of Chemistry–Turbulence Interaction Modeling Approach on the CFD Simulations of Entrained Flow Coal Gasification

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6467
Author(s):  
Jakub Mularski ◽  
Norbert Modliński
Keyword(s):  
Gas Phase ◽  
Coal Gasification ◽  
Flow Reactor ◽  
Plug Flow ◽  
Interaction Model ◽  
Chemical Kinetic ◽  
Reaction Model ◽  
Phase Reaction ◽  
Entrained Flow ◽  
The Impact

This paper examines the impact of different chemistry–turbulence interaction approaches on the accuracy of simulations of coal gasification in entrained flow reactors. Infinitely fast chemistry is compared with the eddy dissipation concept considering the influence of turbulence on chemical reactions. Additionally, ideal plug flow reactor study and perfectly stirred reactor study are carried out to estimate the accuracy of chosen simplified chemical kinetic schemes in comparison with two detailed mechanisms. The most accurate global approach and the detailed one are further implemented in the computational fluid dynamics (CFD) code. Special attention is paid to the water–gas shift reaction, which is found to have the key impact on the final gas composition. Three different reactors are examined: a pilot-scale Mitsubishi Heavy Industries reactor, a laboratory-scale reactor at Brigham Young University and a Conoco-Philips E-gas reactor. The aim of this research was to assess the impact of gas phase reaction model accuracy on simulations of the entrained flow gasification process. The investigation covers the following issues: impact of the choice of gas phase kinetic reactions mechanism as well as influence of the turbulence–chemistry interaction model. The advanced turbulence–chemistry models with the complex kinetic mechanisms showed the best agreement with the experimental data.

scholarly journals Volatile fatty acids build-up and its effect on E. coli inactivation during excreta stabilisation in single-stage and two-stage systems

2018 ◽  
Vol 8 (2) ◽  
pp. 257-267 ◽  
Author(s):  
Joy Riungu ◽  
Mariska Ronteltap ◽  
Jules B. van Lier
Keyword(s):  
Fatty Acids ◽  
Decay Rate ◽  
Volatile Fatty Acids ◽  
Flow Reactor ◽  
Plug Flow ◽  
Single Stage ◽  
Pathogen Inactivation ◽  
Two Stage ◽  
E Coli ◽  
Reactor Length

Abstract Digestion and co-digestion of faecal matter collected from urine diverting dehydrating toilet faeces (UDDT-F) and mixed organic market waste (OMW) was studied in single stage pilot scale mesophilic plug-flow anaerobic reactors at UDDT-F:OMW ratios 4:1 and 1:0. Escherichia coli inactivation and volatile fatty acids (VFA) build-up was monitored at sampling points located along the reactor profile. When applying UDDT-F:OMW ratio of 4:1 at 12% total solids (TS), E. coli inactivation achieved was 2.3 log times higher than that achieved in UDDT-F:OMW ratio of 1:0. In subsequent trials, a two-stage reactor was researched, applying a UDDT-F:OMW ratio of 4:1 and 10 or 12% TS slurry concentrations. Highest VFA concentrations of 16.3 ± 1.3 g/L were obtained at a pH of 4.9 in the hydrolysis/acidogenesis reactor, applying a UDDT-F:OMW ratio of 4:1 and 12% TS, corresponding to a non-dissociated (ND)-VFA concentration of 6.9 ± 2.0 g/L. The corresponding decay rate reached a value of 1.6 per day. In the subsequent methanogenic plug-flow reactor, a decay rate of 1.1 per day was attained within the first third part of the reactor length, which declined to 0.6 per day within the last third part of the reactor length. Results show that a two-stage system is an efficient way to enhance pathogen inactivation during anaerobic digestion.

scholarly journals Pemodelan dan simulasi reverse flow reactor untuk oksidasi katalitik metana: pengembangan prosedur operasi start-up

2018 ◽  
Vol 10 (2) ◽  
pp. 70
Author(s):  
Yogi Wibisono Budhi ◽  
Teguh Kurniawan ◽  
Yazid Bindar
Keyword(s):  
Thermal Condition ◽  
Flow Reactor ◽  
Switching Time ◽  
Reverse Flow ◽  
Energy Requirement ◽  
Homogeneous Model ◽  
Modelling And Simulation ◽  
Heterogeneous Model ◽  
Start Up ◽  
Reverse Flow Reactor

Modeling and simulation of reverse flow reactor for the catalytic oxidation of methane: the development of start-up operating procedures In this modelling and simulation study, three operating procedures during start-up of lean methane (1%-v) oxidation in reverse flow reactor (RFR) have been investigated to get auto-thermal condition, high methane conversion, faster pseudo steady state, and low preheating energy requirement. The RFR model developed based on one-dimension pseudo-homogeneous model for mass balance and heterogeneous model for energy balance. Procedure 1 , the preheating was employed only on the catalyst zone, fails to conduct the auto-thermal reaction and to achieve high conversion. Procedure 2, the preheating was employed for inert and catalyst of left side only, able to achieve the auto-thermal up to switching time (ST) 230 s. Procedure 3, the preheating was employed along the reactor bed, achieve the auto-thermal condition up to ST 300 s. Procedure 2 and 3 achieved the pseudosteadystate at 1000 s for ST 200 s with total conversion during start-up are 95% and 99%. The conversion of Procedure 3 higher than Procedure 2, unfortunately the heat load of Procedure 3 two times higher than Procedure 2. Keywords: modelling and simulation, catalytic methane oxidation, start-up procedure, reverse flow reactor, switching timeAbstrakDi dalam studi pemodelan dan simulasi ini, berbagai prosedur operasi reverse flow reactor (RFR) selama start-up untuk oksidasi katalitik metana encer (1%-v) dikaji dengan target sistem beroperasi secara ototermal, konversi metana tinggi, waktu pencapaian kondisi tunak semu (pseudosteady state) cepat, dan beban panas rendah. Pemodelan reaktor didasarkan pada model satu dimensi dan pseudohomogeneous untuk neraca massa, serta heterogen untuk neraca energi. Pemanasan katalis saja pada awal reaksi (Prosedur 1) tidak dapat mencapai kondisi reaktor yang ototermal. Pemanasan katalis dan inert bagian kiri (Prosedur 2) mampu mencapai kondisi reaktor yang ototermal hingga switching time (ST) 230 detik. Pemanasan seluruh bagian reaktor pada awal reaksi (Prosedur 3) mampu mencapai kondisi reaktor yang ototermal pada ST paling lama 300 detik. Prosedur start-up 2 dan 3 untuk ST 200 detik sama-sama mencapai waktu pseudosteady state pada 1000 detik dengan konversi total selama start-up masing-masing 95% dan 99%. Meskipun Prosedur 3 memberikan konversi sedikit lebih tinggi daripada Prosedur 2, namun beban panas Prosedur 3 mencapai dua kali lebih besar daripada Prosedur 2.Kata kunci: emisi metana, pemodelan dan simulasi, prosedur start-up, reverse flow reactor, switching time.

scholarly journals New Surface Properties in Porcelain Gres Tiles with a Look to Human and Environmental Safety

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
C. L. Bianchi ◽  
C. Pirola ◽  
S. Gatto ◽  
S. Nucci ◽  
A. Minguzzi ◽  
...  
Keyword(s):  
Gas Phase ◽  
Flow Reactor ◽  
Plug Flow ◽  
Environmental Safety ◽  
Photocatalytic Efficiency ◽  
Manufactured Products ◽  
New Generation ◽  
Digital Simulations ◽  
The Impact

Traditional photocatalysis is here brought forward for both the use of nanosized TiO2crystallites and the possibility to have a release of TiO2particles during the final use of the manufactured products. In the present paper both the preparation and characterization of a new generation of photocatalytic tiles are presented. The originality of these products is the surface presence of microsized TiO2as it is not clear yet the impact of the nanoparticles on both human and environmental safety. TiO2is here mixed with a silica compound and the final thermal treatment at 680°C allows the complete surface vitrification which, in turn, makes the tiles surface strongly resistant to abrasion. Photocatalytic efficiency towards the degradation ofNOxin gas phase was measured in both a batch and a plug-flow reactor. The latter reactor configuration was also modeled by digital simulations.

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