Char was considered as pure carbon. The kinetic expressions
used to define the reaction rates are shown in earlier
works [40,41].
The hydrodynamic model is based on the two phase theory
of fluidization where the fluidized bed consists of two regions,
bubbles and emulsion, interacting with each other through
gas interchange simulated by means of a mass transfer coefficient,
kbe.
The model assumes plug flow for gas both in the emulsion
and in the bubble phase, and complete mixing for solids in the
emulsion phase. The hydrodynamic model was integrated
with the chemical model. Several assumptions are employed.
The wake and cloud regions are included in the emulsion
phase, so only one dense phase is considered to be present in
the gasifier and bubbles are assumed completely free of solid
particles. In the emulsion phase, gas flows at the minimum
fluidization velocity, umf.