Download or read book Multi scale Modeling of High temperature Chemistry and Soot Formation of Bio fuels written by Hyunguk Kwon and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Soot refers to carbonaceous particles that have negative impacts on the environment and human health. To intelligently manage ongoing changes in fuel composition, there is an expanding interest in quantifying chemical propensity to form soot from different fuel compounds, ranging from traditional fuels to more sustainable alternative fuels. The overarching objective of this thesis is thus to develop multi-scale modeling combining computational fluid dynamics (CFD) and ReaxFF reactive force field based molecular dynamics (MD) that can determine the yield-based sooting tendency of a fuel and identify the chemical reactions leading to soot formation. The Yield Sooting Index (YSI) measured in a fuel-doped methane/air coflow diffusion flame is chosen as the specific sooting tendency metric in this thesis. For fuels with well-known combustion chemistry, CFD simulation combined with a kinetic model is performed to complement the YSI methodology. To calculate YSIs efficiently, a 1D flamelet-based YSI simulation approach is employed. The CFD of reacting flows specifically deals with two research topics. First, the pressure-dependence of YSI is investigated to identify the applicability of the YSI methodology at elevated pressures. Second, the YSIs of a large number of biofuels with complex chemistry are predicted using 1D flamlet-based YSI simulation combined with a large kinetic model. Detailed 2D CFD simulations are difficult to achieve this due to their very high computational cost. A new sensitivity analysis developed in this thesis is applied to quantify the impact of kinetic parameter uncertainties on YSI predictions. For advanced biofuels with poorly-known chemical kinetics and no associated existing kinetic models, the kinetic-based CFD simulation is not applicable. Therefore, we develop a ReaxFF reactive force field based MD simulation framework to study sooting tendencies of biofuels both quantitatively and qualitatively. For aromatic fuels, we develop a unique ReaxFF MD simulation framework that can quantitatively predict yield-based sooting tendencies, and this framework is applied to toluene and phenol as a proof-of-concept. For non-aromatic fuels, this thesis presents the methodology to study the sooting tendencies qualitatively. Polycyclic alkanes and alkyl-substituted 1,3-dioxolanes recently synthesized as potential jet-fuels and biodiesels, respectively, are specifically studied, since very little effort has been made on their combustion chemistry and sooting tendency. The findings and methodologies provided in this thesis will help to accelerate the introduction of low soot emitting advanced combustion fuels.
Download or read book Development of a Multi scale Approach Using Chemical Kinetics and Reactive Force Field Molecular Dynamics to Model Soot Formation and Oxidation written by Michel Keller and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present study bond formation reactions between soot precursors and their role in the soot inception process is investigated. The soot precursors were generated in macroscopic detailed gas-phase kinetic calculations and according to certain criteria introduced in simulation boxes to model bond formation between soot precursor molecules with reactive force field molecular dynam-ics modeling. The impacts of temperature, fuel mixture and equivalence ratio have been investigated on the rate and structure of the newly formed molecules. The resulting structures compare well to previously reported experimental results. Furthermore, the bond formation rate between PAH is found to be linearly correlated with the temperature at which the PAH precursors are generated, while fuel and equivalence ratio do not have a direct impact on the reaction rate. The generated growth structures are lumped in: 1) directly linked, 2) aliphatically linked and 3) pericondensed polycyclic hydrocarbons. It is found that the amount of aliphatically linked PAH increases with the amount of aliphatic content of fuel mixture. Finally, a reaction scheme is presented displaying the most representative reaction pathways to form growth structures in each lumping class and their eventual intercon-version. The present work - that applies a combined approach of macroscopic gas-phase kinetic calculations and atomistic reactive force field simulations - offers a good alternative to obtain structural differences of nascent soot for a broad range of thermodynamic conditions and detailed reaction mechanisms for soot inception process.
Download or read book Thermochemical Processing of Biomass written by Robert C. Brown and published by John Wiley & Sons. This book was released on 2019-05-28 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive examination of the large number of possible pathways for converting biomass into fuels and power through thermochemical processes Bringing together a widely scattered body of information into a single volume, this book provides complete coverage of the many ways that thermochemical processes are used to transform biomass into fuels, chemicals and power. Fully revised and updated, this new edition highlights the substantial progress and recent developments that have been made in this rapidly growing field since publication of the first edition and incorporates up-to-date information in each chapter. Thermochemical Processing of Biomass: Conversion into Fuels, Chemicals and Power, 2nd Edition incorporates two new chapters covering: condensed phased reactions of thermal deconstruction of biomass and life cycle analysis of thermochemical processing systems. It offers a new introductory chapter that provides a more comprehensive overview of thermochemical technologies. The book also features fresh perspectives from new authors covering such evolving areas as solvent liquefaction and hybrid processing. Other chapters cover combustion, gasification, fast pyrolysis, upgrading of syngas and bio-oil to liquid transportation fuels, and the economics of thermochemically producing fuels and power, and more. Features contributions by a distinguished group of European and American researchers offering a broad and unified description of thermochemical processing options for biomass Combines an overview of the current status of thermochemical biomass conversion as well as engineering aspects to appeal to the broadest audience Edited by one of Biofuels Digest’s "Top 100 People" in bioenergy for six consecutive years Thermochemical Processing of Biomass: Conversion into Fuels, Chemicals and Power, 2nd Edition will appeal to all academic researchers, process chemists, and engineers working in the field of biomass conversion to fuels and chemicals. It is also an excellent book for graduate and advanced undergraduate students studying biomass, biofuels, renewable resources, and energy and power generation.
Download or read book Multi scale Chemistry Modeling of the Thermochemical Conversion of Biomass in a Fluidized Bed Gasifier written by Addison Killean Stark and published by . This book was released on 2015 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thermochemical conversion of biomass to fuels via syn-gas offers a promising approach to producing fungible substitutes for petroleum derived fuels and chemicals. In order for these fuels to be adopted, they must be produced in a cost-competitive way. Unfortunately, there exist a number of challenges in the chemical conversion of solid fuels to the gaseous intermediate syn-gas at an industrially relevant scale due to the complex interplay of chemical kinetics and transport processes which must be addressed to improve the feasibility of this conversion. In this thesis the multiple scales of the chemical conversion of solid biomass in a fluidized bed biomass gasifier (FBBG) as well as the influence of transport processes are analyzed and detailed models are developed capable of predicting reactor performance over a wide range of operating conditions on industrially relevant (fast) computational timescales. First, the particle scale conversion, devolatilization, is considered and a model is developed capturing the interactions of external and internal heat transfer with primary devolatilization chemistry. It is shown that the particle diameter, via internal heat transfer, plays a controlling in the conversion kinetics which is manifested in both the particle conversion time as well as the product gas distribution. This is later shown to play an important role in the gas-phase conversion of the devolatilization products, and a direct correlation is shown between particle diameter and polycyclic aromatic hydrocarbon (PAH) production in a pyrolysis reactor. Next, a reactor network model (RNM) is developed for FBBGs utilizing a detailed chemical kinetic modelling frame-work. The influence of reactor conditions (temperature, air-fuel ratio and residence times) on tar and PAH formation is elucidated, and improved kinetics are proposed that capture catalytic effects of solids on the gas conversion. This RNM is also extended to a reactor operated under pyrolytic conditions yielding good agreement with experimental results. Finally, the influence of solids-solids mixing and bubble growth in the bed on the chemical conversion in the reactor is analyzed with reactive 3D computational uid dynamic (CFD) simulations, and an improved RNM is developed capable of capturing inhomogeneity in the bed-zone. It is shown that both non-uniform devolatilization zones and oxidant by-pass in the bubble phase lead to relatively rich zones in the emulsion which are suitable for PAH formation and growth. Operational strategies are proposed for the minimization of these inhomogeneities, in order to maximize the carbon conversion eciency to syn-gas.
Download or read book Theoretical and Numerical Combustion written by Thierry Poinsot and published by R.T. Edwards, Inc.. This book was released on 2005 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: Introducing numerical techniques for combustion, this textbook describes both laminar and turbulent flames, addresses the problem of flame-wall interaction, and presents a series of theoretical tools used to study the coupling phenomena between combustion and acoustics. The second edition incorporates recent advances in unsteady simulation methods,
Download or read book Physical and Chemical Aspects of Combustion written by F Dryer and published by CRC Press. This book was released on 1997-08-20 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains a collection of papers prepared by leading experts on selected areas of particular importance to researchers in combustion science. The editors have gathered writings on fundamental physical and chemical aspects of combustion, including combustion chemistry, soot formation, and condensed phase and turbulent combustion intended to be a source of current understanding on the topics covered. The materials were originally presented as part of a Colloquium on Combustion held in honor of Professor Irvin Glassman.
Download or read book Advances in Physical Organic Chemistry written by and published by Academic Press. This book was released on 2015-11-20 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Physical Organic Chemistry series of volumes is the definitive resource for authoritative reviews of work in physical organic chemistry. It aims to provide a valuable source of information not only for physical organic chemists applying their expertise to both novel and traditional problems but also for non-specialists across diverse areas who identify a physical organic component in their approach to research. Its hallmark is quantitative, molecular level understanding of phenomena across a diverse range of disciplines. Reviews the application of quantitative and mathematical methods to help readers understand chemical problems Provides the chemical community with authoritative and critical assessments of the many aspects of physical organic chemistry Covers organic, organometallic, bioorganic, enzymes, and materials topics The only regularly published resource for reviews in physical organic chemistry Chapters are written by authoritative experts Wide coverage of topics requiring a quantitative, molecular-level understanding of phenomena across a diverse range of disciplines
Download or read book Chemical Kinetic Modeling of Biofuel Combustion written by Subram Maniam Sarathy and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bioalcohols, such as bioethanol and biobutanol, are suitable replacements for gasoline, while biodiesel can replace petroleum diesel. Improving biofuel engine performance requires understanding its fundamental combustion properties and the pathways of combustion. This study's contribution is experimentally validated chemical kinetic combustion mechanisms for biobutanol and biodiesel. Fundamental combustion data and chemical kinetic mechanisms are presented and discussed to improve our understanding of biofuel combustion. The net environmental impact of biobutanol (i.e., n-butanol) has not been studied extensively, so this study first assesses the sustainability of n-butanol derived from corn. The results indicate that technical advances in fuel production are required before commercializing biobutanol. The primary contribution of this research is new experimental data and a novel chemical kinetic mechanism for n-butanol combustion. The results indicate that under the given experimental conditions, n-butanol is consumed primarily via abstraction of hydrogen atoms to produce fuel radical molecules, which subsequently decompose to smaller hydrocarbon and oxygenated species. The hydroxyl moiety in n-butanol results in the direct production of the oxygenated species such as butanal, acetaldehyde, and formaldehyde. The formation of these compounds sequesters carbon from forming soot precursors, but they may introduce other adverse environmental and health effects. Biodiesel is a mixture of long chain fatty acid methyl esters derived from fats and oils. This research study presents high quality experimental data for one large fatty acid methyl ester, methyl decanoate, and models its combustion using an improved skeletal mechanism. The results indicate that methyl decanoate is consumed via abstraction of hydrogen atoms to produce fuel radicals, which ultimately lead to the production of alkenes. The ester moiety in methyl decanoate leads to the formation of low molecular weight oxygenated compounds such as carbon monoxide, formaldehyde, and ketene, thereby reducing the production of soot precursors. The study concludes that the oxygenated molecules in biofuels follow similar combustion pathways to the hydrocarbons in petroleum fuels. The oxygenated moiety's ability to sequester carbon from forming soot precursors is highlighted. However, the direct formation of oxygenated hydrocarbons warrants further investigation into the environmental and health impacts of practical biofuel combustion systems.
Download or read book Soot Formation in Combustion written by Henning Bockhorn and published by Springer Science & Business Media. This book was released on 2013-03-08 with total page 595 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soot Formation in Combustion represents an up-to-date overview. The contributions trace back to the 1991 Heidelberg symposium entitled "Mechanism and Models of Soot Formation" and have all been reedited by Prof. Bockhorn in close contact with the original authors. The book gives an easy introduction to the field for newcomers, and provides detailed treatments for the specialists. The following list of contents illustrates the topics under review:
Download or read book Molecular Weight Growth Pathways in Fuel rich Combustion written by David Franklin Kronholm and published by . This book was released on 2000 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book MILD Combustion Modelling Challenges Experimental Configurations and Diagnostic Tools written by Alessandro Parente and published by Frontiers Media SA. This book was released on 2021-11-26 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Modeling in Lignocellulosic Biofuel Production written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Detailed Modeling of Soot Formation oxidation in Laminar Coflow Diffusion Flames written by Qingan Zhang and published by . This book was released on 2009 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first goal of this thesis is to develop and validate a modeling tool into which fundamental combustion chemistry and aerosol dynamics theory are implemented for investigating soot formation/oxidation in multi-dimensional laminar coflow diffusion flames taking into account soot polydispersity and fractal-like aggregate structure. The second goal is to use the tool to study soot aggregate formation/oxidation in experimentally studied laminar coflow diffusion flames to advance the understanding of soot aggregate formation/oxidation mechanism.The first part of the thesis deals with the large CPU time problem when detailed models are coupled together. Using the domain decomposition method, a high performance parallel flame code is successfully developed. An advanced sectional aerosol dynamics model which can model fractal-like aggregate structure is successfully implemented into the parallel flame code. The performance of the parallel code is demonstrated through its application to the modeling of soot formation/oxidation in a laminar coflow CH4/air diffusion flame. The parallel efficiency reaches as high as 83%.In the third part of the thesis, the effects of oxidation-driven soot aggregate fragmentation on aggregate structure and soot oxidation rate are studied. Three fragmentation models with different fragmentation patterns are developed and implemented into the sectional aerosol dynamics model. The implementation of oxidation-driven aggregate fragmentation significantly improves the prediction of soot aggregate structure in the soot oxidation region.The second part of the thesis numerically explores soot aggregate formation in a laminar coflow C2H4/air diffusion flame using detailed PAH-based combustion chemistry and a PAH-based soot formation/oxidation model. Compared to the measured data, flame temperature, axial velocity, C2 H2 and OH concentrations, soot volume fraction, the average diameter and the number density of primary particles are reasonably well predicted. However, it is very challenging to predict effectively the average degree of particle aggregation. To do so, particle-particle and fluid-particle interactions that may cause non-unitary soot coagulation efficiency need to be considered. The original coagulation model is enhanced in this thesis to accommodate soot coagulation efficiency. Different types of soot coagulation efficiency are numerically investigated. It is found that a simple adjustment of soot coagulation efficiency from 100% to 20% provides good predictions on soot aggregate structure as well as flame properties.
Download or read book Experiments and Modeling of Multi Component Fuel Behavior in Combustion written by Peter R. Solomon and published by . This book was released on 1988 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computer model was developed to relate pyrolysis and soot formation to fuel properties. A Fourier Transform-Infrared Spectrometer (FT-IR) was used to characterize the effect of temperature, pressure, reaction time, and hydrogen and oxygen concentration of fuels undergoing pyrolysis. The problem of how to identify and measure the hydrogen available for release during pyrolysis was investigated. A detailed data base of a variety of fuels undergoing pyrolysis was developed. The data base conditions included: temperature 800-1500 C; pressure 1-15 atm; and reaction time 100ms-1 sec. Experimental data results show that fuels decompose to form small hydrocarbon species prior to the onset of soot formation. A hydrocarbon model was extended to include Rice-Kossiakoff-Herzfeld mechanism to predict the decomposition of long chain aliphatics to small molecules. A free radical soot model was developed to predict the growth of soot precursors from the small molecules. Keywords: Combustion pyrolysis model; Soot formation; Fourier transform-infrared spectroscopy; Rice-Kossiakoff-Herzfeld mechanism; Free radical.
Download or read book Detailed Chemical Kinetic Modeling of Biofuels and Their Blends with Conventional Fuel Components written by Rupali Tripathi and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multiscale Simulation of Methane Assisted Fluidized Bed Biomass Gasification written by Richard Burton Bates and published by . This book was released on 2016 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: Owing to increasing concerns that climate change poses an urgent threat to the existence of human society, there is a need to develop cost-effective and scalable technologies to produce renewable, drop-in transportation fuels. Fluidized bed biomass gasification (FBBG) is one of the most promising options for the thermochemical conversion of lignocellulosic biomass to synthetic liquid fuels. When biomass is introduced into the high temperature bed (700-900 °C), it rapidly devolatilizes and subsequently reacts with steam, carbon dioxide, and oxygen to form syngas (hydrogen, carbon monoxide) as well as a complex assortment of light gases and condensable compounds known as tar. The main technical challenges facing FBBG technologies are incomplete char conversion and generation of polycyclic aromatic hydrocarbons (PAH's), which require expensive cleanup steps to avoid downstream operational issues. Existing approaches to optimize the performance of FBBG have examined the manipulation of operational parameters such as temperature, pressure, in-bed additives, steam to carbon ratio (SCR), and air fuel equivalence ratio (ER). However, the optimization of FBBG through experimental studies has proven difficult because the extremely complex, coupled, physical and chemical phenomena obscure the actual causal mechanisms. Prior modeling efforts are deficient in several key areas including gas-phase chemistry and char conversion processes, rendering them unable to conclusively determine operating conditions which achieve high cold gas efficiency and complete char/tar conversion. The first part of this work describes the development of a flexible, modular, robust, coupled reactor network model (CRNM) enabling the steady-state simulation of a variety of feedstocks over a wide-range of conditions. The CRNM consists of three independently validated and parameterized sub-models that consider i) particle devolatilization, ii) char conversion, and iii) hydrodynamics and homogeneous reaction kinetics. For each sub-module, the dominant physico-chemical processes and modeling assumptions are identified using characteristic time-scale analyses. The proposed char conversion model describes simultaneous and competing particle-scale processes including gasification, combustion, inhibition, intra/extra particle mass transfer, attrition, and elutriation both under transient and steady-state conditions. Bed hydrodynamics is described using the two-phase theory of fluidization resulting in a network of idealized reactors. This enables the efficient solution of comprehensive gas-phase kinetics mechanisms (327 species and 10933 reactions). The second part of this study validates the CRNM by comparing its results with data from lab-scale steam/air blown gasification experiments performed in collaboration with the National Renewable Energy Laboratory (NREL) and the MIT Chemical Engineering Practice School. The experimental results show that the composition of tar is highly sensitive to the addition of air/oxygen, which appears to accelerate the conversion of lighter PAH's into soot precursors at a fixed operating temperature. Experimental data and modeling results agree that the char reacts with very significant fraction of air/oxygen, improving its overall conversion drastically and reducing the steady state bed inventory of char. The validated model is used to carry out a constrained parametric analysis and optimization of the key operating variables, feed location, and fluidizing agent options. Standalone biomass gasification with steam and air tends to result in a syngas with low H2:CO ratio (/=1). The addition of steam improves the hydrogen content and reduces tars slightly; however, complete conversion of the methane and tar compounds (99%) is ultimately only possible if sufficient secondary air is injected into the freeboard to raise its temperature above 1300 °C. The modeling results demonstrate that methane and biomass act synergistically in the gasifier: the addition of methane acts to significantly improve the carbon yield and energy content of the syngas while the catalytic impact of minerals contained in the biomass act to promote the water-gas shift reaction in the bed region.
Download or read book Modeling Soot Formation Derived from Solid Fuels cAlexander Jon Josephson written by Alexander Jon Josephson and published by . This book was released on 2018 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: While the main focus of this work is the presentation of the three computational models and their implementations, a considerable bulk of this work will discuss some of the technical tools used to accomplish this work. Some of these tools include an introduction to Bayesian statistics used in parameter inference and the method of moments with methods to resolve the 'closure' problem.
