Theoretical Models for Rates of Heterogeneous Reactions During Combustion and Gasification of Liquid Fuels in Fluidized Beds

Abstract

Two mathematical models to allow computations of chemical species production or consumption rates by heterogeneous reactions taking place during combustion and gasification of liquid fuels sprayed on or injected into fluidized beds of solid particles are proposed. The possibilities envisaged here are called: the CIP (Coated Inert Particles) and the CSP (Coke Shell Particle) models. The former assumes that the injected liquid fuel immediately coats the fluidized inert particles in the bed and then goes through pyrolysis, combustion and gasification reactions. The latter presumes that the liquid fuel drops go through fast pyrolysis before meeting any inert particles and the remaining coke hollow particles react with gases in the bed. Analytical solutions for various geometries of the inert particles in the bed are presented. The work does not include the governing equations which constitute the whole mathematical model of fluidized-bed reactors. Such can be found elsewhere. The present work concentrates only on the theoretical aspects. Experimental tests would allow verification if they properly represent the processes of liquid consumption during combustion and gasification processes consuming liquid fuels in fluidized beds and which model would better fit each individual situation.

Theoretical Study on the Effect of Glycerol Fraction in Slurries with Biomass Consumed by a Power-Generation Process

“…Detailed description of its mathematical structure can be found elsewhere . That model has been expanded to include the possibility of consuming mixed solid and liquid fuels . The gasifier exergetic efficiency was chosen as the main objective function for that optimization that was carried in two rounds.…”

“…41 That model has been expanded to include the possibility of consuming mixed solid and liquid fuels. 43 The gasifier exergetic efficiency was chosen as the main objective function for that optimization that was carried in two rounds. Those are detailed later in this work.…”

“…It assumes that the feeding liquid fuel coats solid particles in the bed. Details of those models can be found in the literature. , The gas leaving the gasifier should be cleaned to decrease particle content and their sizes to values acceptable for injections into commercial gas turbines. In addition, the alkaline concentrations in that gas must also be decreased for the same aim. − Ceramic filters might be applied to tar removal, , and dropping the temperatures to 800 K, which is below the dew-points of alkaline components, allows for the removal or, at least, significant decrease in the concentrations of alkaline species in the gas stream .…”

“…It assumes that the feeding liquid fuel coats solid particles in the bed. Details of those models can be found in the literature. , …”

“…It is interesting to observe that, contrary to the exergetic efficiency, high cold efficiencies were found at the lower ranges of glycerol and air injection rates. That can be understood because according to the coated inert particle or CIP model, 43 the liquid glycerol is assumed to coat the surface of solid fuel. This allows the gas around the particle to react with the glycerol layer but impairs the straight access of those reacting gases to the solid fuel.…”