Towards first-principles based kinetic modeling of biomass fast pyrolysis (original) (raw)
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Biomass Pyrolysis Kinetics: A Review of Molecular-Scale Modeling Contributions
Brazilian Journal of Chemical Engineering
Decades of classical research on pyrolysis of lignocellulosic biomass has not yet produced a generalized formalism for design and prediction of reactor performance. Plagued by the limitations of experimental techniques such as thermogravimetric analysis (TGA) and extremely fast heating rates and low residence times to achieve high conversion to useful liquid products, researchers are now turning to molecular modeling to gain insights. This contribution briefly summarizes prior reviews along the historical path towards kinetic modeling of biomass pyrolysis and focusses on the more recent work on molecular modeling and the associated experimental efforts to validate model predictions. Clearly a new era of molecular-scale modelingdriven inquiry is beginning to shape the research landscape and influence the description of how cellulose and associated hemicellulose and lignin depolymerize to form the many hundreds of potential products of pyrolysis.
Approaches to Biomass Kinetic Modelling: Thermochemical Biomass Conversion Processes
Jordanian Journal of Engineering and Chemical Industries, 2021
Modeling of biomass pyrolysis kinetics is an essential step towards reactors design for energy production. Determination of the activation energy, frequency factor, and order of the reaction is necessary for the design procedure. Coats and Redfern's work using the TGA data to estimate these parameters was the cornerstone for modeling. There are two significant problems with biomass modeling, the first is the determination of the kinetic triplet (Activation energy, Frequency factor, and the order of reaction), and the second is the quantitative analysis of products distribution. Methods used in modeling are either One-step or Multistep methods. The one-step techniques allow the determination of kinetic triplet but fail to predict the product distribution, whereas multistep processes indicate the product's distribution but challenging to estimate the parameters. Kissinger, Coats, and Redfern, KAS, FWO, Friedman are one-step methods that have been used to estimate the kinetic parameters. In this work, after testing more than 500 data points accessed from different literature sources for coal, oil shale, solid materials, and biomass pyrolysis using one-step global method, it was found that the activation energy generated by KAS or FWO methods are related as in the following equations: = 0.9629 * + 8.85, with R² =0.9945 or = 1.0328 * − 8.0969 with R 2 = 0.9945. The multistep kinetic models employed the Distributed Activation Energy Model (DAEM) using Gaussian distribution, which suffers from symmetry, other distributions such as Weibull, and logistic has been used. These multistep kinetic models account for parallel/series and complex, primary and secondary biomass reactions by force-fitting the activation energy values. The frequency factor is assumed constant for the whole range of activation energy. Network models have been used to account for heat and mass transfer (diffusional effects), where the one-step and multistep could not account for these limitations. Three network models are available, the Bio-CPD (Chemical Percolation Devolatilization) model, Bio-FLASHCHAIN, and the Bio-FG-DVC (Functional Group Depolymerization Vaporization Crosslinking models). These models tried to predict the product distributions of the biomass pyrolysis process.
Chemical Kinetics of Biomass Pyrolysis
Energy & Fuels, 2008
This paper analyzes the main kinetic features of biomass pyrolysis, devolatilization, and the gas phase reactions of the released species. Three complex steps are faced in sequence: the characterization of biomasses, the description of the release of the species, and finally, their chemical evolution in the gas phase. Biomass is characterized as a mixture of reference constituents: cellulose, hemicellulose, and lignin. This assumption is verified versus experimental data, mainly relating to thermal degradation of different biomasses. Devolatilization of biomasses is a complex process in which several chemical reactions take place in both the gas and the condensed phase alongside the mass and thermal resistances involved in the pyrolysis process. A novel characterization of the released species is applied in the proposed devolatilization models. The successive gas phase reactions of released species are included into an existing detailed kinetic scheme of pyrolysis and oxidation of hydrocarbon fuels. Comparisons with experimental measurements in a drop tube reactor confirm the high potentials of the proposed modeling approach.
Modeling Biomass Pyrolysis Kinetics and Mechanisms
ACS Division of Fuel Chemistry Preprints, 1997
Over the next decade there will be a renewed emphasis on the production of chemicals and liquid fuels from biomass, the use of agricultural wastes as feedstocks, and the co-firing of coal and biomass materials. In view of the tremendous diversity of biomass feedstocks, a great need exists for a robust, comprehensive model that could be utilized to predict the composition and properties of pyrolysis products as a function of feedstock characteristics and process conditions. The objective of this work is to adapt an existing coal pyrolysis model and make it suitable for the pyrolysis of biomass. The soundness of this approach is based on numerous similarities between biomass and coal. There are important differences, however, which preclude direct application of the coal model. This work involved: I) selection of a set of materials representing the main types of biomass; 2) development of a biomass classification scheme; 3) development of a modeling approach baaed on modifications of a coal pyrolysis model; 4) calibration of the model for a set of standard materials against pyrolysis data taken over a range of heating rates; 5) validation of the model against pyrolysis data taken under other (higher) heating rate conditions.
Modeling of biomass pyrolysis kinetics
Proceedings of the 27th Symposium (International) on Combustion, pp. 1327-1334, 1998
Over the next decade there will be a renewed emphasis on the use of biomass as a fuel and the co-firing of coal and biomass materials. In view of the tremendous diversity of biomass feedstocks, a great need exists for a robust, comprehensive model that could be utilized to predict the composition and properties of pyrolysis products as a function of feedstock characteristics and process conditions. The objective of this work was to adapt an existing coal pyrolysis model, the Functional Group-Depolymerization, Vaporization Crosslinking (FG-DVC) model, and make it suitable for the pyrolysis of biomass. The soundness of this approach is based on numerous similarities between biomass and coal. However, there are important differences, which preclude direct application of the coal model. This work involved: (1) selection of a set of materials representing the main types of biomass, (2) development of a classification scheme, (3) development of a modeling approach based on an extension of a coal pyrolysis model, (4) calibration of the model for a set of standard materials against pyrolysis data taken over a range of heating rates, and (5) validation of the model against pyrolysis data taken under higher heating rate conditions. A streamlined version of the FG-DVC coal pyrolysis model was successfully developed for whole biomass samples and demonstrated to have predictive capability when extrapolated to high heating rate conditions (1000 C/sec). Improvements will be needed in the model to properly account for mineral effects and secondary reactions, and the model has not yet been tested under the very high heating rates that may exist in some combustion devices (10,000–100.000 C/sec).
Comprehensive Kinetic Modeling Study of Bio-oil Formation from Fast Pyrolysis of Biomass
Energy & Fuels, 2010
The aim of this work is to analyze the optimal operating conditions for fast biomass pyrolysis. The operating conditions required to maximize the yield of liquid products are investigated and discussed on the basis of a comprehensive mathematical model of wood/biomass devolatilization. Crucial issues are the fast and complete heating of biomass particles to reduce char formation and the rapid cooling of released products to reduce the role of secondary gas-phase pyrolysis reactions. Chemical kinetics as well as heat-and mass-transfer phenomena play an important role in this process; thus, a comprehensive kinetic model is applied. The proposed model, when compared to the majority of other devolatilization models, attempts to characterize pyrolysis reactions with a lumped stoichiometry using a limited number of equivalent components to describe not only gaseous products but also tar species. Model predictions are compared to experimental measurements not only with further validation in mind but also principally to verify the reliability of this comprehensive kinetic model of biomass devolatilization and combustion.
Kinetic Studies of Model Reactions to Transform Biomass into Fuels
2014
Mehta, Dhairya D. Ph.D., Purdue University, December 2014. Dissertation Kinetic studies of model reactions to transform biomass into fuels. Major Professors: Fabio H. Ribeiro, Rakesh Agrawal, and W. Nicholas Delgass. Second-generation biofuels utilizing lignocellulosic biomass are considered to be a promising alternative to fossil-based fuels. Lignocellulosic biomass is structurally diverse and therefore requires detailed understanding of the thermal depolymerization and catalytic hydrodeoxygenation reactions to optimize the overall process. This dissertation describes the experimental work using model compounds to elucidate the role of bimetallic catalyst and control the reaction operating parameters such as temperature and hydrogen pressure to maximize energy recovery in the liquid product from biomass resource. Water-gas shift (WGS) is a well-known reaction to produce hydrogen and finds application industrially in steam-reforming of methane and other fossil-based feedstocks. Trad...
Fast pyrolysis of biomass: A review of relevant aspects. Part I: Parametric study
Recent years have witnessed a growing interest in developing biofuels from biomass by thermochemical processes like fast pyrolysis as a promising alternative to supply ever-growing energy consumption. However, the fast pyrolysis process is complex, involving changes in phase, mass, energy, and momentum transport phenomena which are all strongly coupled with the reaction rate. Despite many studies in the area, there is no agreement in the literature regarding the reaction mechanisms. Furthermore, no detailed universally applicable phenomenological models have been proposed to describe the main physical and chemical processes occurring within a particle of biomass. This has led to difficulties in reactor design and pilot industrial scale operation, stunting the popularization of the technology. This paper reviews relevant topics to help researchers gain a better understanding of how to address the modeling of biomass pyrolysis.
Journal of the Energy Institute
Pyrolysis is a versatile technology for exploiting diversified feedstocks to produce a wide range of products, including biochar, bio-oil, and syngas with high potential in diverse applications. The cardinal motivation of pyrolysis research is to productively use diverse biomass to reduce adverse impacts on ecology and enhance process economics. However, complex reactions of pyrolysis pose operational challenges. Thus, the present review targets the reaction mechanisms and kinetics of pyrolysis to enhance the understanding for better process control, improved performance, and product distribution. Pyrolysis mechanisms of the major structural components of biomass, such as cellulose, lignin, and hemicellulose, as well as proteins, lipids, and carbohydrates, are discussed in detail. Various modeling techniques and tools, viz., mathematical, kinetic, computational fluid dynamic modeling, and machine learning algorithms, have been employed to better understand the pyrolysis mechanisms and product distribution. In addition, the most critical challenges, namely aerosol formation, tar formation and their removal mechanisms, that severely impact the pyrolysis process and products are identified and reported. Thus, the present work critically discusses state-of-art biomass pyrolysis, focusing on the reaction mechanism, modeling, and associated challenges to overcome, given that the pyrolysis products and the process are enhanced.