Process and Reactor Level Simulations of Coal-Direct Chemical-looping Combustion - Novel Combustion Concepts for Sustainable Energy Development - page 343

Fig. 12 Geometry outline with five pressure taps (left), mesh (middle), and wireframe (right)of
the complete CD-CLC con guration

Based on the particle tracks in Fig. 13 , a prominent gas bubble can be observed
to form during the first 480 ms of the high-velocity central jet injection. Due to the

presence of the particle recirculation duct on one side, the bubble becomes slightly
asymmetric. The leading front of the spouted bed reaches the ceiling of the fuel
reactor around 480 ms, and a large number of particles are slammed into the
cyclone through the connecting duct, as can be seen between 520 and 600 ms.
Between 480 and 800 ms, the pressure buildup in the fuel reactor vanishes and the
remaining particles in the fuel reactor fall back into the fl fluidized bed. In the

meantime, particles in the cyclone get separated from the flue stream and begin to

deposit in the downcomer. In addition, recirculation of small number of particles
from the loop seal back into the fuel reactor is observed from about 60

fl

360 ms.
From around 400 ms onward, there is a large number of stagnant particles at the
bottom of the fuel reactor. At the same time, the high-velocity jet forms an unsteady
pathway for the air to rapidly bypass the dense bed regime in the fuel reactor. Such
a pathway is very undesirable since no new gas bubbles can get initiated due to its

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