Development of a Thermophysical Properties Model for Flowsheet Simulation of Biomass Pyrolysis Processes

Abstract

A properties model was developed for use in commercial process simulators to model pyrolysis of lignocellulosic biomass. The component list was chosen to enable process simulations based on a recently published lumped pyrolysis kinetics model. Since many of the compounds involved in pyrolysis are not found in simulator databanks, estimation based on available literature data was used to establish missing parameters. Standard solid enthalpy of formation, solid heat capacity, and solid density estimates calculated from the limited experimental data available were prepared for six biomass constituents and nine intermediate and end-products of their pyrolysis. Ideal gas enthalpy of formation and heat capacity, critical property, and vapor pressure estimates were prepared for another four pyrolysis end-products and one biomass component. The estimates were all validated against the closest available experimental data in the literature. The addition of these new components and properties allows thermodynamically rigorous simulation of lumped biomass pyrolysis reactions with accurate energy balances. Enthalpies of reaction calculated from the properties model were compared with reported reaction enthalpies for the same lumped biomass pyrolysis reactions and found to be in general agreement.

A rigorous process modeling methodology for biomass fast pyrolysis with an entrained‐flow reactor

“…It should be noted that the equation-of-state properties model developed by Gorensek et al [10] predicts two liquid phases in the pyrolysis vapor product condensate, with essentially all of the xylosan and free fatty acid collecting in a separate liquid phase. (If only one liquid phase is allowed, the model keeps xylosan and free fatty acid in the vapor phase, which is unrealistic.)…”

“…In Humbird et al's original model, [8] ash is characterized using proximate and ultimate analyses, but here it is treated as a chemical compound (calcium oxide), simplifying the stream structure. The model also makes use of the thermophysical properties model recently developed by Gorensek et al, [10] which covers all 49 components appearing in Table 1, of which 20 are not found in commercial simulator databanks. This includes the heat of formation, heat capacity, and solid density of all solid components and the ideal gas enthalpy of formation, critical properties, ideal gas heat capacity, vapor pressure, and acentric factor of all fluid components.…”

“…This includes the heat of formation, heat capacity, and solid density of all solid components and the ideal gas enthalpy of formation, critical properties, ideal gas heat capacity, vapor pressure, and acentric factor of all fluid components. The reader is referred to Gorensek et al [10] for details.…”

“…T A B L E 1 Biomass pyrolysis reaction mechanism adapted from Ranzi et al [9] (compound names defined by Gorensek et al [10] )…”

“…With the goal of establishing a rigorous process modeling methodology to support heat and mass balance calculations and process design for fast biomass pyrolysis using entrainedflow reactors, this work builds on that of Humbird et al, [8] incorporating improvements necessary to correct model deficiencies. Specifically, the kinetic scheme is updated with additional components and revised reactions as proposed by Ranzi et al [9] ; the component-based thermophysical properties model reported by Gorensek et al [10] is incorporated to facilitate heat balance calculations; and the original nonadiabatic heat transfer equations are replaced with rigorous differential enthalpy balance equations. The model includes all unit operations necessary for a biomass to bio-oil processing plant, including reactor, separations, and heat generation by combustion of by-products.…”