Studies in support of recirculating bed reactors for the processing of coal. Final report

Abstract

Task I, Coal Mixer Modelling Studies, examined the physical mixing of densely-laden, gas-solids streams in the upflow (riser) leg of a recirculating bed reactor. The experiments were conducted in a Plexiglas cold model, using a three-inch diameter, nineteen-feet high riser, with air as the motive fluid and HFZ-20, a microspheroidal cracking catalyst (60..mu.. diameter, 56 lb/ft/sup 3/ bulk density), as a recirculating solids. The riser was operated under the conditions described for fast fluidization. Invasive (probe and x-ray) measurements of the riser flow field revealed the existence of a high velocity, dilute phase transport regime occupying a central core and turbulent annular regime of high density but with no net transport of solids. These findings are consistent with those reported in investigations of the large-scale risers used in petroleum refinery. Consequently, they are at variance with the claim that there is a fast fluidization regime with fine-scale dispersal of solids throughout the gas phase. Gas mixing experiments (a foreign gas stream was injected co-axially into the riser core) indicated that the mixing rate was determined by the velocity of the riser gas stream. Solids mixing experiments (a foreign, entrained solids stream was injected co-axially into the riser core) revealed fairlymore » rapid penetration of the jet but poor fine-scale mixing of the solids. Other experimental results elucidated the factors which govern the equilibrium distribution of sulfur between organic sulfur in char and gaseous hydrogen sulfide. « less

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