Reforming methane and higher hydrocarbons in syngas streams

Abstract

Oxygen is added to a raw syngas stream that contains hydrogen and CO, one or more light hydrocarbons, and that may also contain tars, produced by gasification of carbonaceous feed material, while imparting heat at a rate greater than 125 BTU per pound of oxygen added, to partially oxidize light hydrocarbons and convert tars if present to lower molecular weight products.

What is claimed is: 
     
         1 . A method of syngas treatment, comprising
 (A) providing a raw syngas stream obtained by gasification of carbonaceous feed material, wherein the raw syngas stream may optionally contain tars, and comprises hydrogen and CO as well as one or more light hydrocarbons selected from the group consisting of methane, hydrocarbons containing 2 or 3 carbon atoms, and mixtures thereof; and   (B) adding oxygen to the raw syngas stream while imparting heat to the raw syngas stream at a rate greater than 125 BTU per pound of oxygen added, and partially oxidizing one or more of said light hydrocarbons to increase the amounts of hydrogen and CO in the syngas while converting tars if present to lower molecular weight products including hydrogen and CO.   
     
     
         2 . A method according to  claim 1  wherein step (B) comprises mixing fuel and oxygen and combusting a portion of the oxygen in the mixture with said fuel to form a hot oxidant stream that has a temperature of at least 2000 F and that contains oxygen and products of said combustion, and feeding said hot oxidant stream into said raw syngas stream. 
     
     
         3 . A method according to  claim 2  wherein said fuel that is mixed with oxygen and combusted to form said hot oxidant stream, comprises gaseous byproducts formed in the production of product fuels from syngas formed in step (B). 
     
     
         4 . A method according to  claim 1  wherein step (B) comprises adding fuel and oxygen to said raw syngas and combusting said added fuel after it is added to said raw syngas stream. 
     
     
         5 . A method according to  claim 4  wherein said fuel that is added to said raw syngas comprises gaseous byproducts formed in the production of product fuels from syngas formed in step (B). 
     
     
         6 . A method according to  claim 1  wherein step (B) comprises combusting fuel and oxidant comprising at least 90 vol. % oxygen in a burner to produce a flame that heats said raw syngas stream, while adding oxygen to said raw syngas stream. 
     
     
         7 . A method according to  claim 6  wherein said fuel that is combusted in said burner comprises gaseous byproducts formed in the production of product fuels from syngas formed in step (B). 
     
     
         8 . A method according to  claim 1  wherein step (B) comprises heating, by indirect heat transfer, oxygen that is added to said raw syngas stream. 
     
     
         9 . A method according to  claim 1  further comprising feeding treated syngas produced in step (B) to a reactor that produces product fuel from said treated syngas, wherein said reactor also produces a tail gas and liquid byproduct stream, a portion of or all of which is added to the raw syngas and combusted to provide heat in step (B). 
     
     
         10 . A method according to  claim 9  wherein said reactor produces one or more products selected from the group consisting of methanol, ethanol and F-T liquids. 
     
     
         11 . A method according to  claim 1  which further comprises converting syngas produced by step (B) to product fuel. 
     
     
         12 . A method of syngas treatment, comprising
 generating a raw syngas stream by gasification of carbonaceous feed material, wherein the raw syngas stream may optionally contain tars, and comprises hydrogen and CO as well as one or more light hydrocarbons selected from the group consisting of methane, hydrocarbons containing 2 or 3 carbon atoms, and mixtures thereof; and treating said raw syngas stream by the method of  claim 1 .   (B) adding oxygen to the raw syngas stream while imparting heat to the raw syngas stream at a rate greater than 125 BTU per pound of oxygen added, and partially oxidizing one or more of said light hydrocarbons to increase the amounts of hydrogen and CO in the syngas while converting tars to lower molecular weight products.   
     
     
         13 . A method according to  claim 12 , further comprising converting syngas produced by step (B) to product fuel. 
     
     
         14 . A method according to  claim 1  wherein said raw syngas stream contains tars, and wherein tars in said raw syngas stream are converted to lower molecular weight products.