scholarly journals Numerical Simulation and Validation in Scrubber Wash Water Discharge from Ships

2020 ◽  
Vol 8 (4) ◽  
pp. 272
Author(s):  
Yong-Seok Choi ◽  
Tae-Woo Lim
Keyword(s):  
Cfd Simulation ◽  
Water Discharge ◽  
Reaction Model ◽  
Wash Water ◽  
Turbulent Schmidt Number ◽  
Wide Range ◽  
Fuel Oils ◽  
Treatment Equipment ◽  
Initial Ph ◽  
Low Sulfur

A regulation on the sulfur emissions of ships sailing in global sea areas has been enforced since 1 January 2020. In this new regulation, ships are required to use low-sulfur fuel oils or to install an after-treatment equipment, such as a scrubber. Open and hybrid scrubbers wash the exhaust gas using seawater and then discharge the wash water overboard. According to the regulation promulgated by the International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC), the wash water must have a pH of 6.5 or higher at 4 m from the discharge point. Wash water is generally acidic, with a pH of 2.5–3.5, whereas seawater is alkaline, with a pH of approximately 8.2. The wash water is dispersed after being discharged overboard through a nozzle, and its pH is restored through dilution with the surrounding seawater. In this study, the pH was calculated by using a theoretical chemical reaction model, and then the dispersion of wash water was analyzed using CFD simulation. This study describes the process of selecting the appropriate turbulent Schmidt number in a wide range of nozzle diameters. Finally, the appropriate nozzle diameter was determined based on the initial pH of the discharged scrubber wash.

scholarly journals Gradient HPLC in the determination of drug lipophilicity and acidity

2001 ◽  
Vol 73 (9) ◽  
pp. 1465-1475 ◽  
Author(s):  
Roman Kaliszan ◽  
Piotr Haber ◽  
Tomasz Baczek ◽  
Danuta Siluk
Keyword(s):  
Mobile Phase ◽  
High Performance ◽  
Standard Procedure ◽  
Gradient Elution ◽  
Log P ◽  
Retention Data ◽  
Organic Modifier ◽  
Wide Range ◽  
Aqueous Component ◽  
Initial Ph

The linear-solvent strength (LSS) model of gradient elution in high-performance liquid chromatography (HPLC) has been demonstrated to provide parameters of lipophilicity and acidity of analytes. pKa and log kw values are determined in three gradient runs. The first two experiments use an aqueous buffered eluent with a wide-range organic modifier gradient at pH of buffer, providing suppression of ionization of the analyte. That experiment allows an estimate of contents of the organic modifier in the mobile phase (%B), producing requested retention coefficient, k, for the nonionized form of the analyte. The next experiment is carried out with the latter %B and a pH-gradient of the aqueous component of the eluent that is sufficient to overlap possible pKa value of the analyte. The initial pH of the buffer used to make the mobile phase is selected to insure that the analyte is in nonionized form. The resulting retention time allows an estimate of pKa in a solvent of the given %B.The log kw parameter obtained correlated well with the corresponding value obtained by the standard procedure of extrapolation of retention data determined in a series of isocratic measurements. The correlation between log kw and the reference parameter of lipophilicity, log P, was very good for a series of test analytes. The values of pKa were found to correlate with the literature pKa data determined in water for a set of aniline derivatives studied.

CFD Simulation of Fluid Flow Through Porous Media: Application to Decomposed Gases Flow Through Foam Pattern in Lost Foam Casting

Materials ◽  
2003 ◽  
Author(s):  
Sayavur I. Bakhtiyarov ◽  
Ruel A. Overfelt
Keyword(s):  
Cfd Simulation ◽  
Reynolds Numbers ◽  
Phase Flow ◽  
Flow Through Porous Media ◽  
Foam Material ◽  
Element Analysis ◽  
Wide Range ◽  
Flow Through ◽  
Foam Pattern ◽  
Lost Foam

Numerical simulation of decomposed gases through foam pattern was conducted using finite element analysis. A new kinetic model is proposed for gaseos phase flow between molten metal and foam material. The computations were performed for a wide range of Reynolds numbers. The results of the simulations are compared with the experiemental data obtained in this study.

Reaction Model Development of Selected Aromatics as Relevant Molecules of a Kerosene Surrogate – The Importance of M-Xylene Within the Combustion of 1,3,5-Trimethylbenzene

2021 ◽  
Author(s):  
Astrid Ramirez Hernandez ◽  
Trupti Kathrotia ◽  
Torsten Methling ◽  
Marina Braun-Unkhoff ◽  
Uwe Riedel
Keyword(s):  
Atmospheric Pressure ◽  
Burning Velocity ◽  
Model Development ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Reaction Model ◽  
Pollutant Emissions ◽  
Similar Species ◽  
Ignition Delay Times ◽  
Wide Range

Abstract The development of advanced reaction models to predict pollutant emissions in aero-engine combustors usually relies on surrogate formulations of a specific jet fuel for mimicking its chemical composition. 1,3,5-trimethylbenzene is one of the suitable components to represent aromatics species in those surrogates. However, a comprehensive reaction model for 1,3,5-trimethylbenzene combustion requires a mechanism to describe the m-xylene oxidation. In this work, the development of a chemical kinetic mechanism for describing the m-xylene combustion in a wide parameter range (i.e. temperature, pressure, and fuel equivalence ratios) is presented. The m-xylene reaction submodel was developed based on existing reaction mechanisms of similar species such as toluene and reaction pathways adapted from literature. The sub-model was integrated into an existing detailed mechanism that contains the kinetics of a wide range of n-paraffins, iso-paraffins, cyclo-paraffins, and aromatics. Simulation results for m-xylene were validated against experimental data available in literature. Results show that the presented m-xylene mechanism correctly predicts ignition delay times at different pressures and temperatures as well as laminar burning velocities at atmospheric pressure and various fuel equivalence ratios. At high pressure, some deviations of the calculated laminar burning velocity and the measured values are obtained at stoichiometric to rich equivalence ratios. Additionally, the model predicts reasonably well concentration profiles of major and intermediate species at different temperatures and atmospheric pressure.

Analysis of the Mixing and Emission Characteristics in a Model Combustor

2018 ◽  
Author(s):  
Shan Li ◽  
Shanshan Zhang ◽  
Lingyun Hou ◽  
Zhuyin Ren
Keyword(s):  
Gas Turbines ◽  
Schmidt Number ◽  
Numerical Study ◽  
Flame Temperature ◽  
Scalar Dissipation ◽  
Mixing Process ◽  
Nox Formation ◽  
Turbulent Schmidt Number ◽  
Wide Range ◽  
Air Mixing

Modern gas turbines in power systems employ lean premixed combustion to lower flame temperature and thus achieve low NOx emissions. The fuel/air mixing process and its impacts on emissions are of paramount importance to combustor performance. In this study, the mixing process in a methane-fired model combustor was studied through an integrated experimental and numerical study. The experimental results show that at the dump location, the time-averaged fuel/air unmixedness is less than 10% over a wide range of testing conditions, demonstrating the good mixing performance of the specific premixer on the time-averaged level. A study of the effects of turbulent Schmidt number on the unmixedness prediction shows that for the complex flow field involved, it is challenging for Reynolds-Averaged Navier-Stokes (RANS) simulations with constant turbulent Schmidt number to accurately predict the mixing process throughout the combustor. Further analysis reveals that the production and scalar dissipation are the key physical processes controlling the fuel/air mixing. Finally, the NOx formation in this model combustor was analyzed and modelled through a flamelet-based approach, in which NOx formation is characterized through flame-front NOx and its post-flame formation rate obtained from one-dimensional laminar premixed flames. The effect of fuel/air unmixedness on NOx formation is accounted for through the presumed probability density functions (PDF) of mixture fraction. Results show that the measured NOx in the model combustor are bounded by the model predictions with the fuel/air unmixedness being 3% and 5% of the maximum unmixedness. In the context of RANS, the accuracy in NOx prediction depends on the unmixedness prediction which is sensitive to turbulent Schmidt number.

Reactions of the radical cation derived from 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS·+) with amino acids. Kinetics and mechanism

2000 ◽  
Vol 78 (8) ◽  
pp. 1052-1059 ◽  
Author(s):  
C Aliaga ◽  
E A Lissi
Keyword(s):  
Amino Acids ◽  
Radical Cation ◽  
Sulfonic Acid ◽  
Biological Fluids ◽  
Reaction Rates ◽  
Kinetics And Mechanism ◽  
Specific Rate ◽  
Wide Range ◽  
Initial Ph ◽  
Secondary Reactions

Stable free radicals derived from 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS·+) have been extensively employed to monitor the antioxidant capacity of biological fluids and beverages. Besides reacting with typical antioxidants (such as phenols or thiols) these radicals react with a variety of hydrogen or electron donors. The present work reports on the kinetics and mechanism of these radical reactions with several amino acids. Reaction rates notably increase when the pH of the media increases and, when measured under similar conditions, follows the ordercysteine > > tryptophan > tyrosine > histidine > cystineThe kinetics of the process is interpreted in terms of a mechanism comprising an initial pH dependent reversible step, followed by secondary reactions of the substrate derived radical with itself or with another ABTS·+; this simple three-step mechanism leads to very complex kinetic expressions. The specific rate constants of several of the elementary steps were determined by working under a wide range of substrate, radical, and ABTS concentrations. The values obtained for the initial interaction between the ABTS derived radical and the substrate range from 0.5 M–1 s–1 to 1.9 × 106 M–1 s–1 for histidine and cysteine, respectively.Key words: ABTS radical cation, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), amino acids, kinetics.

scholarly journals Influence of inlet air distributor geometry on the fluid dynamics of conical spouted beds: A CFD study

2018 ◽  
Vol 24 (4) ◽  
pp. 369-378 ◽  
Author(s):  
J.N.M. Batista ◽  
R.C. Brito ◽  
R. Béttega
Keyword(s):  
Fluid Dynamics ◽  
Cfd Simulation ◽  
Low Cost ◽  
Scale Up ◽  
Straight Tube ◽  
Spouted Bed ◽  
Bed Height ◽  
Spouted Beds ◽  
Wide Range ◽  
Solid Dynamics

The spouted bed presents limitations in terms of scale-up. Furthermore, its stability depends on its geometry as well as the properties of the fluid and solid phases. CFD provides an important tool to improve understanding of these aspects, enabling a wide range of information to be obtained rapidly and at low cost. In this work, CFD simulation was used to evaluate the effects of different inlet air distributors (Venturi and straight tube) and the effects of static bed height on the fluid and solid dynamics of a conical spouted bed. Simulations were performed using the two-dimensional Euler-Euler approach. In order to evaluate the fluid dynamics model, static pressure data obtained by simulation were compared with experimental data obtained with the Venturi distributor. The fluid and solid dynamics of the conical spouted bed were obtained by CFD simulation. The results showed that the pressure drop was lower for the straight tube air distributor, while the Venturi air distributor provided higher stability and a more homogenous air distribution at the bed entrance.

scholarly journals Stochastic parcel tracking in an Euler-Lagrange compartment model for fast simulation of fermentation processes

2021 ◽  
Author(s):  
Cees Haringa ◽  
Wenjun Tang ◽  
Henk Noorman
Keyword(s):  
Cellular Response ◽  
Cfd Simulation ◽  
Mixing Time ◽  
Compartment Model ◽  
Reaction Model ◽  
Heterogeneous Environments ◽  
Cfd Simulations ◽  
Fermentation Processes ◽  
Spatially Resolved ◽  
Unit Operations

Compartment modeling (CM) is a well-known approach for computationally affordable, spatially-resolved hydrodynamic modeling of unit operations. Recent implementations use flow profiles based on CFD simulations, and several authors included microbial kinetics to simulate gradients in bioreactors. However, these studies relied on black-box kinetics, that do not account for intra-cellular changes and cell population dynamics in response to heterogeneous environments. In this paper, we report the implementation of a Lagrangian reaction model, where the microbial phase is tracked as a set of biomass-parcels, each linked with an intra-cellular composition vector and a structured reaction model describing their intra-cellular response to extracellular variations. A stochastic parcel tracking approach is adopted, in contrast to the resolved trajectories used in prior CFD implementations. A penicillin production process is used as a case-study. We show good performance of the model compared to full CFD simulations, both regarding the extra-cellular gradients and intra-cellular pool response, provided the mixing time in the CM matches the full CFD simulation; taking into account that the mixing time is sensitive to the number of compartments. The sensitivity of the model output towards some of the inputs is explored. The coarsest representative CM requires a few minutes to solve 80 hours of flow time, compared to approx. 2 weeks for a full Euler-Lagrange CFD simulation of the same case. This alleviates one of the major bottlenecks for the application of such CFD simulations towards analysis and optimization of industrial fermentation processes.

Organic matter and heavy metal removals from complexed metal plating effluent by the combined electrocoagulation/Fenton process

2010 ◽  
Vol 61 (10) ◽  
pp. 2617-2624 ◽  
Author(s):  
I. Kabdaşlı ◽  
T. Arslan ◽  
I. Arslan-Alaton ◽  
T. Ölmez-Hancı ◽  
O. Tünay
Keyword(s):  
Organic Matter ◽  
Metal Removal ◽  
Treatment Method ◽  
Fenton Process ◽  
Toc Removal ◽  
Operation Conditions ◽  
Metal Plating ◽  
Wide Range ◽  
Initial Ph ◽  
H2o2 Addition

In the present study, the treatment of metal plating wastewater containing complexed metals originating from the nickel and zinc plating process by electrocoagulation (EC) using stainless steel electrodes was explored. In order to improve the organic matter removal efficiency, the effect of H2O2 addition to the electrocoagulation (the combined EC/Fenton process) application was investigated. For this purpose, a wide range of H2O2 concentrations varying between 15 and 230 mM was tested. All EC and EC/Fenton processes were performed at an initial pH of 2.6 and at an optimized current density of 22 mA/cm2. Although up to 30 mM H2O2 addition improved the EC process performance in terms of organic matter abatement, the highest COD and TOC removal efficiencies were obtained for the combined EC/Fenton process in the presence of 20 mM H2O2. Nickel and zinc were completely removed for all runs tested in the present study after pH adjustments. At the optimized operation conditions, the combined EC/Fenton process proved to be an alternative treatment method for the improvement of organic matter reduction as well as complexed metal removal from metal plating industry wastewater.

Modelling casein aggregation and curd firming in goats' milk from backscatter of infrared light

2003 ◽  
Vol 70 (3) ◽  
pp. 335-348 ◽  
Author(s):  
Manuel Z Castillo ◽  
Fred A Payne ◽  
Clair L Hicks ◽  
José S Laencina ◽  
María-Belén M López
Keyword(s):  
Kinetic Model ◽  
Diffuse Reflectance ◽  
Block Design ◽  
Reaction Model ◽  
Order Reaction ◽  
Infrared Light ◽  
Wide Range ◽  
Data Points ◽  
Increasing Temperature ◽  
Reflectance Ratio

A kinetic model was proposed for describing the curd assembly of skimmed goats' milk during enzymic coagulation. The enzymic coagulation of milk was monitored using an optical sensor that measured diffuse reflectance (light backscatter) at 880 nm. The appearance of a shoulder, at low temperatures and protein concentrations, in the diffuse reflectance ratio profile after the inflection point of the curve (Tmax) appeared to separate the aggregation and curd firming steps. The diffuse reflectance ratio profile after Tmax was attributed to the overlapping of casein micelles aggregation and curd firming reactions. The developed kinetic model combined a second order reaction model to describe aggregation reactions and a first order reaction model to describe firming processes reactions. A completely randomised block design with three replications was used to determine the effect of protein concentration and temperature on kinetic constants. Milk was adjusted to three levels of protein (30, 50 and 70 g/kg), and coagulated at five temperatures (20, 25, 30, 35 and 40°C) to test a wide range of processing conditions. Data points from each profile after Tmax were fitted to the proposed model using non-linear regression. The average R2 and standard error of prediction (SEP) for 45 tests conducted were in the range of 0·9975±0·0027 and 0·0081±0·0037, respectively. A significant increase in characteristic times for aggregation (τ2) and curd firming processes (τ1) were found when temperature decreased or protein increased. Theoretical asymptotic value of reflectance ratio, R∞, increased with increasing level of protein and temperature (P<0·05). The parameter β1, which represented the fraction of diffuse reflectance ratio attributed to aggregation, decreased with increasing temperature and decreasing protein.

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