Treatment of Wood Pyrolysis Data via a Multiple Gas−Solid Reaction Model

Abstract

Wood pyrolysis consisting of water evaporation, consecutive, and parallel reactions was modeled through a multiple gas−solid reaction scheme. Effective kinetic parameters were determined through the model and compared to the results of a conventional differential method where the results differed substantially. The behavior of global wood conversion is compared to the experimental results. System parameters and variables, transport coefficients, and thermophysical properties are determined transiently. The millimeter sized pellets were found to have substantial gradients within. The heating rate of thermogravimetric analysis equipment is also considered in the model. The rate expressions were developed based on molar solid concentrations in the wood fibers. For the simulation grain (pore or fiber), pellet and reactor spaces of different magnitudes were considered. The effective quantities were ΔE 1 = 255.7 kJ/mol, k 10 = 8.5 × 1018 s-1, ΔE 3 = 140.7 kJ/mol, and k 30 = 4 × 106 s-1.

Detailed Chemical Kinetic Modeling of Vapor-Phase Reactions of Volatiles Derived from Fast Pyrolysis of Lignin

“…Owing to its renewability, carbon neutrality, and low sulfur content, biomass has the potential to help relieve the energy and environmental crisis. − Biomass can be converted into heat, fuels, and chemicals through pyrolysis, gasification, liquefaction, and combustion. , Pyrolysis is always involved in biomass thermal conversion processes as either the entire process or an important step to cause fragmentation of the biomass structure. , Thus, the pyrolysis of biomass has been an attractive research subject in recent years. The effects of pressure, temperature, heating rate, heat and mass transfer, and reactor configuration on the product distributions, product upgrading, and the chemistry and kinetics have been thoroughly reviewed. ,,− During pyrolysis, typically 75–90 wt % of biomass is converted into volatiles at temperatures higher than 773 K. Volatiles escape from biomass particles and continue to crack, combine, or condense in vapor phase. This process is named as vapor-phase reactions of volatiles, which is unavoidable during biomass pyrolysis. ,, This high conversion into volatile products suggests that vapor-phase reactions have an important role during biomass pyrolysis, influencing the formation of the final products.…”

A Simple Sampling Method for the Reaction History in Fluidized or Transport Reactors

“…Although a comprehensive modeling approach could be used, , the following assumptions were made to describe the process theoretically for simplicity: (i) The pellets are uniform in size and keep their shape during drying. (ii) There is a gas film around each pellet for convective mass and heat transfer.…”