Two-phase free jet model of an atmospheric entrained flow gasifier

Abstract

We present a steady-state two-phase fluid dynamic model based on a classical free jet approach for the simulation of the main reaction zone in an atmospheric entrained flow gasifier. Radial Gaußian profiles of the mixing ratio and velocity for single-phase free jets taken from literature are adapted to the two-phase free jet. Exchange of momentum and mass between the jet and the surrounding is described by a parameter derived from atomization experiments under ambient conditions. With the free jet equations, a pattern of gas phase velocity and temperature is calculated. Droplets are introduced at the nozzle, accelerated, heated up and evaporated. Initial droplet size fractions are measured under ambient conditions. Sub-process models for fuel decomposition, oxidation and the water gas shift reaction are included in the model. The interaction of the sub-process models and the free jet equations are considered via balance equations for momentum, mass and enthalpy, solved in each control volume. The two-phase free jet model (2Ph-FJM) calculates the local composition, velocity and temperature of the gas phase as well as velocity, temperature and evaporation of the fuel droplet fractions. Simulation results are approved for a set of experimental data (i.e. droplet velocity, droplet size distribution and flame structure via OH*-chemiluminescence imaging) from the bench-scale atmospheric entrained flow gasifier REGA.