Design of high-velocity fluid beds for flash hydrogenation

Abstract

Successful commercial development of flash hydrogenation for the production of light liquids and gases from coal is largely dependent on the design of the coal-hydrogen reactor. Reactors which operate in the high velocity regimes of fluidization (turbulent and fast fluid beds) offer potential advantages over dilute phase reactor systems. Lower hydrogen circulation rates, lower hydrogen preheat temperatures and reactor temperatures are the most significant of these, resulting in lower capital costs, increased energy efficiency and reduced product cost. Pilot plant experience with high velocity beds fed with caking coal is promising for the development of flash hydrogenation reactors. These trials suggest criteria for design of the coal injection zone and show how growth of char agglomerates can be controlled. Two design examples are developed to explore the applicability of high velocity beds to flash hydrogenation in concrete terms. The first deals with processing of lignite in a fast fluidized bed, the second with processing a bituminous coal in a turbulent bed. The designs in both cases show the advantage of this approach, as well as its uncertainties and limitations. They suggest that further development would be rewarding.