GB632386A - Improvements in or relating to the production of fuel gas - Google Patents

Abstract

Tail gas obtained by reacting CO and H2 and removing normally liquid hydrocarbons and other synthesis products is contacted with a hydrogenating catalyst under hydrogenating conditions for the formation of saturated gaseous hydrocarbons whereby a gas of high heating value and low hydrogen content is obtained. A further increase in heating value may be obtained by removal of water and carbon dioxide. Suitable catalysts are iron group metals, e.g. Co or Ni, oxides and sulphides of Group 6 metals, e.g. Cr, Mo and W, and spent catalyst from the synthesis, particularly spent iron catalysts. Hydrogenation temperatures are preferably 650-850 DEG F. using Fe, Ni or Group 6 catalysts, and 500-750 DEG F. with Co. Pressure may be that of the original synthesis, preferably 100-1000 p.s.i. Reaction time is chosen so that substantially all the hydrogen present is consumed. Extraneous hydrogen may be added. Fluidized catalysts may be used with a particle size from 400 mesh - 1/2 inch diameter-and a linear velocity of the fluidizing gas of 0.1-5 ft./sec. Fluidized operation is preferably used also for the synthesis and for production of the synthesis gas from carbonaceous solids and steam. Carbon dioxide may be removed from the hydrogenated tail gas by a two-stage scrubbing, for example with monoethanolamine, the scrubbing liquid of the first stage being partly regenerated by flashing, and that of the second stage being regenerated by substantially complete removal of carbon dioxide. In an example, bituminous coal is converted with steam at 1800-1900 DEG F. and 5-50 p.s.i., the water gas desulphurized and contacted with an iron catalyst at 650 DEG F. and 325 p.s.i., and the tail gas converted with nickel at 625-675 DEG F. and 300 p.s.i.