Thermochemical modeling of isothermal carbonization of thick wood particle – Effect of reactor temperature and wood particle size (original) (raw)

A New Algorithm for Solving Isothermal Carbonization of Wood Particle

A new algorithm based on the lattice Boltzmann method (LBM) is proposed as a potential solver for one-dimensional heat and mass transfer for isothermal carbonization of wood particles. To check the validity of this algorithm, the LBM results have been compared with the published data and a good agreement is obtained. Then, the model is used to study the effect of reactor temperature and particle size on the evolution of the local temperature and mass loss inside the wood particle

Thermogravimetric analysis and kinetics modeling of isothermal carbonization of olive wood in inert atmosphere

Thermochimica Acta, 2006

The kinetics of olive wood carbonization is investigated by means of isothermal thermogravimetric analysis method. Measurements were carried out in a thermobalance for different fixed temperatures between 498 and 648 K. A two-stage semi-global kinetic model consisting of four sequential steps was proposed to derive kinetic parameters. The olive wood is classified in three pseudo-components. For the first two, similar thermal degradation mechanisms take place in a single reaction step. For the third, the thermal degradation takes place in two consecutive steps. The isothermal conditions allow the kinetic constants (activation energy and pre-exponential factors) to be estimated by means of the analytical solution of the mass conservation equations. An overall good agreement was obtained with activation energy values available in the literature.

A thermo fluid dynamic model of wood particle gasification-and combustion processes

In order to qualitatively understand and evaluate the thermo-fluid dynamic situation within a wood gasification reactor, a 1D particle model has been created. The presented tool accounts for the highly in-stationary, kinetic-and thermo chemical effects, leading to partial gasification and combustion of a wood particle embedded within a packed bed collective. It considers the fluid-dynamic situation within the changing porous bulk structure of the packed bed, its impact on species-and heat transition mechanisms, the energy-and mass balances of wood, coal, pyrolysis-gas, wood-gas and off-gas phases, the thermodynamics of locally developing gasification-and combustion reaction equilibria, as well as the presence of the chemical species hydrogen, water, carbon (dioxide de, methane, oxygen, solid carbon and gaseous, longer chain hydrocarbons from pyrolysis. Model results can be shown to yield very good, qualitative agreement with measurements, found in literature.

Influence of Operating Conditions on the Thermal Behavior and Kinetics of Pine Wood Particles Using Thermogravimetric Analysis

Energies

Although there are many studies available in literature about biomass pyrolysis or devolatilization using thermogravimetric analysis (TGA), the effects of important operating parameters have infrequently been investigated for pine wood particle combustion. Consequently, the present study investigates the influence of particle size (63 µm to 1 mm), heating rate (5 to 243 °C/min), and air flow rate (10 to 150 mL/min) on the mass loss of pine wood using TGA. Additionally, the kinetic parameters considering the different conditions were determined to be incorporated in a numerical model. The effect of the heating rate on the thermal decomposition behavior has shown that the thermogravimetric and derivative thermogravimetric curves were shifted to higher temperatures with the increase in the heating rate. In this way, the heating rate affects the temperature at which the highest mass loss rate occurs as well as its value. Furthermore, comparing the higher and lower heating rate, the time...

A meta-analysis of thermo-physical and chemical aspects in CFD modelling of pyrolysis of a single wood particle in the thermally thick regime

Chemical Engineering Journal, 2022

Thermochemical conversion of larger biomass particles (thermally thick regime) toward high-end products still suffers from an unrevealed quantitative relationship between process and product parameters. The main issue relates to the influence of heating rate within the particle, critical conversion-wise but difficult to assess experimentally. Computational fluid dynamics (CFD) modelling may help, but first the model must prove its reliability to prevent error transfer to the results. This study aimed to provide an unbiased, state-of-the-art model constructed in a stepwise mode to investigate the heating rate's distribution. Several datasets with broadly varying parameters from the literature were used for the development and validation since the reproduction of datasets would not bring novelty to solving the problem. Instead of the model's calibration to fit to the data, the parameters for each step-model were meticulously selected to match the experimental conditions. The stepwise development showed the best accuracy when the anisotropy and the heat sink drying sub-model were implemented. Moreover, using the Ranzi-Anca-Couce (RAC) scheme led to more accurate results than the Ranzi scheme. The comprehensive model was positively validated against a broad range of production parameters (pyrolysis temperature: 500°C-840 °C, diameter of particles: 10 mm-20 mm, shapes: cylinders and spheres). Investigation showed a pattern in volatiles release profiles and homogeneous heating rate distribution when particle size is below 4 mm. Despite basing the models on the literature's data, the study includes novel and valuable insights for biomass conversion and constitutes a solid foundation for future development.

Kinetics Modeling of Wood Torrefaction - Weight Loss Kinetics

Torrefaction is a thermal treatment step in a relatively low temperature range of 210-240˚C, which aims to improve the dimensional stability and durability of wood. The weight loss kinetics for torrefaction of wood samples was studied using equipment specially conceived to measure mass losses during thermal treatment. Laboratory experiments were performed under nitrogen for heating rates of 1˚C.min-1. A mathematical model for the kinetics of the thermodegradation process was used and validated. Measurements of temperature distribution and anhydrous weight loss were performed on dry sample of poplar wood during pyrolysis in an inert atmosphere at 230°C. The mathematical formulation describing the simultaneous heat and mass transfers requires coupled nonlinear partial differential equations. These unsteady-state mathematical model equations were solved numerically by the commercial package FEMLAB. A detailed discussion of the computational model and the solution algorithm is given. Once the validity of different assumptions of the model had been analyzed, the experimental results were compared with those calculated by the model. Acceptable agreement was achieved.

Modelling of pyrolysis of large wood particles

Bioresource Technology, 2009

A fully transient mathematical model has been developed to describe the pyrolysis of large biomass particles. The kinetic model consists of both primary and secondary reactions. The heat transfer model includes conductive and internal convection within the particle and convective and radiative heat transfer between the external surface and the bulk. An implicit Finite Volume Method (FVM) with Tridiagonal Matrix Algorithm (TDMA) is employed to solve the energy conservation equation. Experimental investigations are carried out for wood fines and large wood cylinder and sphere in an electrically heated furnace under inert atmosphere. The model predictions for temperature and mass loss histories are in excellent agreement with experimental results. The effect of internal convection and particle shrinkage on pyrolysis behaviour is investigated and found to be significant. Finally, simulation studies are carried out to analyze the effect of bulk temperature and particle size on total pyrolysis time and the final yield of char.

Parametric Studies Of Wood Pyrolysis Particles

2015

In the present study, a numerical approach to describe the pyrolysis of a single solid particle of wood is used to study the influence of various conditions such as particle size, heat transfer coefficient, reactor temperature and heating rate. The influence of these parameters in the change of the duration of the pyrolysis cycle was studied. Mathematical modeling was employed to simulate the heat, mass transfer, and kinetic processes inside the reactor. The evolutions of the mass loss as well as the evolution of temperature inside the thick piece are investigated numerically. The elaborated model was also employed to study the effect of the reactor temperature and the rate of heating on the change of the temperature and the local loss of the mass inside the piece of wood. The obtained results are in good agreement with the experimental data available in the literature.

Lattice Boltzmann Simulation of the Carbonization of Wood Particle

A numerical study based on the Lattice Boltzmann Method (LBM) is proposed to solve one, two and three dimensional heat and mass transfer for isothermal carbonization of thick wood particles. To check the validity of the proposed model, computational results have been compared with the published data and a good agreement is obtained. Then, the model is used to study the effect of reactor temperature and thermal boundary conditions, on the evolution of the local temperature and the mass distributions of the wood particle during carbonization.