A Compact Kinetic Model for Biomass Pyrolysis at Gasification Conditions

Abstract

Computational fluid dynamics (CFD) tools are increasingly gaining importance to obtain detailed insight into biomass gasification. A major shortcoming of the current CFD tools to study biomass gasification is the lack of computationally affordable chemical kinetic models, which allows detailed predictions of the yield and composition of various gas and tar species in complex reactor configurations. In this work, a detailed mechanism is assembled from the literature and reduced to a compact model describing the gas-phase reactions of biomass gasification in the absence of oxygen. The reduction procedure uses a graph-based method for unimportant kinetic pathways elimination and quasi-steady-state species selection. The resulting reduced model contains 39 gas species and 118 reactions and is validated against the detailed model and two experimental configurations: the pyrolysis of volatile species, such as levoglucosan, in a tubular reactor, and the fast pyrolysis of biomass particles in a drop tube reactor. The reduced model predicts the evolution of major gas products (e.g., CO, CO2, CH4, H2) and various classes of tar (e.g., single-ring aromatics, oxygenated aromatics, PAHs) produced during biomass gasification. The capability of the reduced model to adequately capture the chemical process in a complex reactor geometry at an acceptable computational cost is demonstrated by employing it in a simulation of a pseudo two-dimensional laboratory-scale fluidized bed reactor.

Modeling Biowaste Biorefineries: A Review

“…A (fast) pyrolysis process transforms the biomass, in the absence of oxygen, into noncondensable gases (like CO, CO 2 , and H 2 ), tar or bio-oil, and biochar or solid carbon. (Fast) pyrolysis processes occur at relatively low temperatures (between 300 and 600 • C) and are characterized by a high liquid fuel yield, i.e., bio-oil (Anca-Couce and Scharler, 2017; Goyal and Pepiot, 2017). Bio-oil is considered to be a suitable replacement for fossil fuels and displays many advantageous properties, like its ease of storing and transportation (Cai et al, 2018).…”

“…Bio-oil is considered to be a suitable replacement for fossil fuels and displays many advantageous properties, like its ease of storing and transportation (Cai et al, 2018). Gasification processes are in their essence pyrolysis processes, but occur at higher temperatures (800-1,200 • C) and mostly in the presence of oxygen (Goyal and Pepiot, 2017;Jin et al, 2017). Because of the higher process temperatures, the yield of gaseous products is higher than in the case of pyrolysis processes.…”

“…The main product obtained during gasification processes is syngas, mainly consisting of H 2 , CO, CO 2 , CH 4 , and other lightweight hydrocarbons. Syngas can be directly used as a gaseous fuel, but can also be transformed into other products, like alcohols and acids, using (bio-)chemical processes (Goyal and Pepiot, 2017;Hejazi et al, 2017a). While the gasification process is in its essence a rigorous pyrolysis process, both processes display a high level of resemblance.…”

Thermo-chemical equilibrium modeling and simulation of biomass gasification

“…Along with the processes of heat and mass transfer, thermodynamic and chemical processes have to be adequately addressed in the models. The equilibrium [8][9][10] and kinetic [11][12][13] approaches are used in most known models. Many kinetic models are based on the concept of a perfectly stirred reactor, considering detailed mechanisms of chemical reactions.…”

A computational study of the effects of multiphase dynamics in catalytic upgrading of biomass pyrolysis vapor

“…Most EL studies to date consider two‐dimensional flows with a relatively small number of particles (e.g., Refs. ). Recent work has demonstrated that two‐dimensional simulations are only capable of capturing qualitative features of particle clustering, and a fully three‐dimensional description is required to accurately capture the quantitative flow behavior in CFB risers.…”