Fluid dynamics in coal liquefaction reactors using neutron absorption tracer technique

Hydrodynamic properties in the coal liquefaction reactors at the Kaskima pilot plant, which was constructed based on the NEDOL process, were investigated using the neutron absorption tracer technique. The reactor system is composed of three vessels, each with 1.0 m ID and 11.8 m in height. The gas velocity in the reactors under coal liquefaction conditions was estimated using a reaction simulator that contained reaction rates and vapor-liquid equilibrium. The axial dispersion coefficients in the first and third reactors at superficial gas velocities of 0.06-0.07 m/s were much smaller than those reported for air-water systems under ambient conditions. This suggests that the pilot-plant reactors operated fundamentally in the homogeneous bubble flow regime.