Conversion of carbonaceous materials to synthetic natural gas by reforming and methanation

Abstract

A process for the production of synthetic natural gas from a carbonaceous material, preferably a biomass material, such as wood. The carbonaceous material is steam reformed to produce a syngas, which is then fed to a methanation zone to produce synthetic natural gas.

1 . A process for converting carbonaceous material to synthetic natural gas, which process comprising:
 a) passing said carbonaceous material and an effective amount of superheated steam to a reforming zone operated at a temperature of about 850° C. to about 1200° C. and a pressure form about 3 psig to about 500 psig wherein said carbonaceous material is reformed to produce a synthetic gaseous product comprised of hydrogen, carbon monoxide, carbon dioxide, and methane, which synthetic gaseous product stream is at an elevated temperature;   b) passing said synthetic gaseous product stream at an elevated temperature to a heat recovery zone wherein its temperature is substantially lowered;   c) passing said lowered temperature synthetic gaseous product stream to a solids recovery zone wherein substantially all remaining solids are removed;   d) passing said synthetic gaseous product stream from said solids recovery zone to an organics removal zone wherein substantially all of any organic material is removed by contact with an organic liquid in which the organic material is substantially soluble;   e) passing said synthetic gaseous product stream from said organics removal zone to an acid gas removal zone wherein substantially all acid gases are removed;   f) passing said synthetic gaseous product stream from said acid gas removal zone to a methanation process unit containing at least one methanation catalyst and operated at methanation process conditions thereby resulting in a product stream comprised predominantly of methane.   
     
     
         2 . The process of  claim 1  wherein the carbonaceous material is a source of fossil fuels selected from the group consisting of coal, peat, lignite, tar sands,and bitumen from oil shale. 
     
     
         3 . The process of  claim 1  wherein the carbonaceous material is a biomass material. 
     
     
         4 . The process of  claim 3  wherein the biomass material is a cellulosic material. 
     
     
         5 . The process of  claim 4  wherein the cellulosic material is selected from the group consisting of wood, bagasse, rice hulls, rice straw, kennaf, old railroad ties, dried distiller grains, corn stalks and cobs and straw. 
     
     
         6 . The process of  claim 5  wherein the cellulosic material is selected from wood and dried distiller grains. 
     
     
         7 . The process of  claim 1  wherein the carbonaceous material is dried to a moisture content of less than or equal to about 15% by weight before reforming. 
     
     
         8 . The process of  claim 1  wherein the carbonaceous material is with the size range of about 1/32 inch to about ½ inch. 
     
     
         9 . The process of  claim 1  wherein the heat recovery zone uses water to recover heat and wherein at least a portion of the heated water is used as preheated steam to the reforming process unit. 
     
     
         10 . The process of  claim 1  wherein the acid gas scrubbing agent used in the acid gas removal zone is selected from the group consisting of amines and alcohols. 
     
     
         11 . The process of  claim 10  wherein the acid gas scrubbing agent is an alcohol. 
     
     
         12 . The process of  claim 11  wherein the alcohol is methanol. 
     
     
         13 . The process of  claim 10  wherein the acid gas scrubbing agent is an amine selected from the group consisting of diethanol amine and mono-ethanol amine. 
     
     
         14 . The process of  claim 13  wherein the amine is diethanol amine. 
     
     
         15 . The process of  claim 1  wherein the methanation zone contains three reactors in series and wherein heat is removed from the stream passing from the first reactor and the second reactor. 
     
     
         16 . The process of  claim 1  wherein at least a portion of the methane produced in the methanation unit is introduced into a natural gas pipeline. 
     
     
         17 . The process of  claim 14  wherein methane is removed from a pipeline and converted to a syngas. 
     
     
         18 . The process of  claim 1  wherein prior to organic removal step (j) the synthetic gaseous product stream is subjected to a water wash wherein is flowed countercurrent to a stream of water to remove any remaining solids material.