Improved techniques for gasifying coal. Third quarterly report, January 1--March 31, 1977

Abstract

Fluidization experiments conducted with power station fly ash in the 6-inch system provided a dramatic demonstration that cohesive solids which could hardly be fluidized in the low-velocity bubbling regime could be maintained in vigorous fluidization in high-velocity beds. Experiments were cnducted to study the various fluidization regimes and the transitions between them. The transitions from slugging to the turbulent state observed with Dicalite 4200 and a new solid, HFZ-20, were not as sharp as that observed with FCC. Additional experiments with FCC lend further confirmation to the possibility that a turbulent fluidization regime, distinct from the fast bed state, exists and bridges bubbling and fast fluidization. Gas backmixing was appreciable in the bubbling regime; it is considerably less, though not insignificant, in the turbulent regime, and the gas is essentially in plug flow in the fast fluidized bed. Experiments carried out to measure the pressure drop across the primary cyclone and its capture efficiency with FCC as the test solid confirmed that at high solid rates the capture efficiency increases with decreasing gas velocity at the entrance to the cyclone. Experiments in flash hydrogenation and flash hydrolysis are described.