Process for the production of fuel gas from coal

Claim 1

In a process for the conversion of a solid, agglomerating hydrocarbonaceous solid to a more valuable gaseous product wherein (i) an oxygen containing gas in admixture with steam is contacted with the solid at elevated temperatures in a fluidized bed gasification reaction zone, (ii) ash is agglomerated in the bottom portion of the reaction zone, and (iii) the ash is selectively separated from the fluidized bed by withdrawing the ash from the bottom portion of the reaction zone through a withdrawal nozzle having a constricted central opening wherein the ash agglomerates have a tendency to occlude the nozzle and the central opening thereof, the improvement which comprises (a) passing an oxygen containing gas into the nozzle, through a separate conduit concentrically positioned within the nozzle, the discharge end of the conduit being positioned substantially above the constricted central opening, said oxygen containing gas passing through the separate conduit having an oxygen concentration of about 30-75% by volume, (b) passing an additional gaseous fluid upward into the fluidized bed through the withdrawal nozzle and past the outside of the separate conduit, said additional gaseous fluid having an oxygen concentration less than the oxygen concentration in the gas passing through the separate conduit, said nozzle being positioned below the fluidized bed and being concentrically surrounded by a fluid distribution and support grid, and (c) passing an additional gaseous fluid substantially free of oxygen through the fluid distribution and support grid, said oxygen containing gas, said additional gaseous fluid passing through said nozzle, and said additional gaseous fluid passing through said grid providing a superficial gas velocity of at least 2 ft/sec. through the fluidized bed.