Process for reducing the sulfide sulfur content of char with carbon dioxide and H.sub.2 O

#Char is used as a fuel and is manufactured by partially pyrolyzing coal or other carbonaceous materials. Char contains sulfur which is objectionable because upon combustion, the sulfur forms sulfur dioxide, an air pollutant. Governmental air purity standards limit the use of fuels to fuels containing relatively low concentrations of sulfur. The presence in char of sulfur concentrations which exceed such limits has restricted the use of char as a fuel. The need for a relatively sulfur-free char has therefore become very important, especially in view of dwindling supplies of oil and natural gas and abundant supplies of coal.

#Methods have been devised to desulfurize char but they are commercially unacceptable for removing enough of the sulfur to comply with air purity standards. One such method is to treat the char with hydrogen gas at elevated temperatures to cause a reaction between the hydrogen and the sulfur to form hydrogen sulfide gas. This method reduces the levels of sulfur present as organic sulfur and pyritic sulfur, but it increases the levels of the remaining sulfide sulfur due to reactions which convert some of the pyritic and organic sulfur to sulfide sulfur. Thus, the benefit to be gained by minimizing the pyritic and organic sulfur contents is offset by an increase in the sulfide sulfur content.

#Organic sulfur refers to the sulfur which forms a part of organic molecules contained in the char. Pyritic sulfur refers to the sulfur that forms a part of iron pyrite, FeS.sub.2, found in char. Sulfide sulfur refers to the sulfur that forms a part of inorganic sulfur compounds found in char, such as, for example, FeS and CaS. Pyritic sulfur is an inorganic sulfur but is not comprehended by the term "sulfide sulfur" as used herein.

#An embodiment of the invention is schematically depicted in the accompanying drawing.

#A reactor 10 is provided and has a char feed line 12 and a hydrogen inlet line 14 in communication therewith. Cyclone 18 is disposed within said reactor 10 and communicates with the interior thereof through outlet 19 to a hydrogen recovery system (not shown) through outlet 20. Standpipe 22 is provided in the bottom portion of reactor 10 for communication with said reactor 10 and with steam-carbon dioxide reactor 28 through char feed line 26. Slide valve 24 is provided in standpipe 22 and in char feed line 26. Reactor 28 is in communication with gas line 36 in the bottom portion thereof which is in communication with steam line 32 and carbon dioxide line 34. Cyclone 40 is provided within the interior of reactor 28 and is in communication therewith through outlet 41 and with a hydrogen recovery system (not shown) through outlet 42. Standpipe 44 is provided in reactor 28 for communication therewith and with char outlet line 48. Slide valve 46 is provided in standpipe 44 and in char outlet line 48.

#In operation, char is crushed to a particle size suitable for gravity flow through char feed line 12 and is fed through char line 12 to form a bed of char particles in reactor 10. Hydrogen gas enters reactor 10 through inlet pipe 14, and depending upon the pressure of said hydrogen gas and the particle size of the char, will cause the reactor 10 to be operated as either a fluidized bed, an entrained bed, or expanded bed system. The char is held in reactor 10 for a prescribed residence time sufficient to convert the organic and pyritic sulfur to sulfide sulfur. Thereafter slide valve 24 is opened to allow the reacted char particles to flow through standpipe 22 and line 26 and into the steam-carbon dioxide reactor 28. The char is caused to flow through standpipe 22 by introducing unreacted char particles through line 12. The unreacted char from line 12 accumulates at the bottom portion of reactor 10 to cause the level of the reacted char bed to rise and flow into standpipe 22.

#Any excess hydrogen gas and the gases evolved from the hydrogen reaction with the char exit out of reactor 10 through cyclone 18 which prevents the char particles from leaving the reactor 10 with the exit gases.