Method of producing a hydrocarbon composition

Abstract

A method of producing a hydrocarbon composition, the method including providing a biomass raw-material; gasifying the raw-material in the presence of oxygen to produce a gas containing carbon monoxide, carbon dioxide, hydrogen and hydrocarbons possibly together with inert components; separately increasing the hydrogen-to-carbon monoxide ratio of the gas to a value of about 2; feeding the gas to a Fischer-Tropsch reactor; converting in the Fischer-Tropsch reactor at least a significant part of the carbon monoxide and hydrogen contained in the gas into a hydrocarbon composition containing C 4 -C 90 hydrocarbons; and recovering the hydrocarbon composition. Fresh external hydrogen is introduced into the gas before feeding into the Fischer-Tropsch reactor. By using external hydrogen feed, the capacity of a biomass gasification process can be increased and any need for a Water Gas Shift for producing hydrogen from carbon monoxide and steam can be eliminated.

What is claimed is: 
     
         1 . A method of producing a hydrocarbon composition, the method comprising:
 providing a biomass raw material;   gasifying the raw material in the presence of oxygen to produce a gas containing carbon monoxide, carbon dioxide, hydrogen and hydrocarbons;   separately increasing the hydrogen-to-carbon monoxide ratio of the gas to a value of about 2;   feeding the gas to a Fischer-Tropsch reactor;   converting in the Fischer-Tropsch reactor at least a part of the carbon monoxide and hydrogen contained in the gas into a hydrocarbon composition containing C 4 -C 90  hydrocarbons; and   recovering the hydrocarbon composition,   wherein fresh hydrogen is introduced into the gas before the gas is fed into the Fischer-Tropsch reactor.   
     
     
         2 . The method according to  claim 1 , wherein the fresh hydrogen is introduced into the gas at a point immediately before the Fischer-Tropsch reactor in order to raise the hydrogen-to carbon monoxide ratio of the gas to about 2. 
     
     
         3 . The method according to  claim 1 , wherein the fresh hydrogen is derived from an external source of hydrogen. 
     
     
         4 . The method according to  claim 1 , wherein the fresh hydrogen is obtained from a source that is natural gas, methane, hydrogen gas produced by bioelectricity, or methane hydrate. 
     
     
         5 . The method according to  claim 1 , wherein the fresh hydrogen is obtained from natural gas or another source of methane and other light hydrocarbons by catalytic reforming. 
     
     
         6 . The method according to  claim 1 , wherein the fresh hydrogen is obtained from natural gas or another source of methane and other light hydrocarbons in a cascade formed by at least one unit for catalytic reforming and one unit for a water gas shift reaction. 
     
     
         7 . The method according to  claim 1 , further comprising:
 feeding the gas obtained by gasification of the raw material into a reformer;   reforming the gas in the presence of oxygen in order to increase the ratio of hydrogen to carbon monoxide in a gaseous effluent of the reformer to a value in the range of 0.5 to 1.5;   withdrawing the gaseous effluent from an outlet of the reformer; and   further increasing the hydrogen-to-carbon monoxide ratio of the gaseous effluent to a value of about 2 by introducing the fresh hydrogen therein.   
     
     
         8 . The method according to  claim 7 , wherein gasification is carried out at a first temperature and reforming at a second temperature, said second temperature being higher than the first temperature. 
     
     
         9 . The method according to  claim 7 , wherein reforming is carried out in a catalyst bed reformer at a temperature in excess of 850° C. 
     
     
         10 . The method according to  claim 1 , comprising:
 gasifying the raw material in the presence of oxygen at a temperature in excess of 1000° C.; and   further increasing the hydrogen-to-carbon monoxide ratio of the gas effluent to a value of about 2 by introducing fresh hydrogen into the gas.   
     
     
         11 . The method according to  claim 1 , wherein carbon dioxide is withdrawn from the gas before it is fed into the Fischer-Tropsch reactor and used for forming carbon monoxide by a reversed water gas shift. 
     
     
         12 . The method according to  claim 11 , wherein carbon dioxide is withdrawn from the gas downstream any gas washing process arranged before the Fischer-Tropsch reactor. 
     
     
         13 . The method according to  claim 11 , wherein carbon dioxide is separated from the gas by membrane filtration, by pressure swing absorption or by washing with a liquid capable of absorbing carbon dioxide. 
     
     
         14 . The method according to  claim 11 , wherein substantially all of the carbon dioxide contained in the gas is removed before it is fed into the Fischer-Tropsch reactor and used for forming carbon monoxide by a reversed water gas shift reaction by use of external hydrogen. 
     
     
         15 . The method according to  claim 11 , wherein only a part of the carbon dioxide contained in the gas is removed and used for forming carbon monoxide by a reversed water gas shift reaction by use of external hydrogen. 
     
     
         16 . The method according to  claim 15 , wherein external hydrogen is both fed into the gas in order to increase hydrogen-to-carbon monoxide ratio and used for forming carbon monoxide by reversed water gas shift reaction. 
     
     
         17 . The method according to  claim 16 , wherein the molar ratio between the fresh hydrogen and CO 2  fed into the gas and used for forming carbon monoxide, respectively, is in the range of 0.5:1 to 6:1. 
     
     
         18 . The method according to  claim 11 , comprising:
 feeding the withdrawn carbon dioxide together with fresh hydrogen into a gaseous effluent of a reformer or a high-temperature gasifier in order to produce a modified gaseous effluent; and   feeding the modified gaseous effluent into a reaction zone for a reversed water gas shift reaction.   
     
     
         19 . The method according to  claim 14 , wherein the reversed water gas shift reaction is carried out at a temperature in the range of about 500 to 1000° C. 
     
     
         20 . The method according to  claim 1 , wherein less than 20 mole-% of the carbon monoxide produced from the biomass raw material is used for producing hydrogen gas for use in the Fischer-Tropsch reactor. 
     
     
         21 . The method according to  claim 20 , wherein substantially none of the carbon monoxide produced from the biomass raw material is used for producing hydrogen gas for use in the Fischer-Tropsch reactor. 
     
     
         22 . The method according to  claim 1 , wherein a molar ratio of the fresh hydrogen fed into the gas to the carbon monoxide produced by gasification of the biomass raw material is from 0.55 to 2.4. 
     
     
         23 . The method according to  claim 1 , wherein the recovered hydrocarbon composition is further treated to produce a fuel or lubricant for a combustion engine. 
     
     
         24 . The method according to  claim 23 , comprising producing from the recovered hydrocarbon composition a hydrocarbon composition suitable for a fuel application having distillation cut points in the range of about 150 to 300° C. 
     
     
         25 . The method according to  claim 23 , comprising producing from the recovered hydrocarbon composition a hydrocarbon composition suitable for a lubricant application, wherein said composition has a compound having a carbon number in the range of 30 to 40. 
     
     
         26 . The method according to  claim 1 , wherein an external hydrogen is fed directly into a reformer or into a reversed water gas shift reactor or into both. 
     
     
         27 . The method according to  claim 1 , wherein the gas containing carbon monoxide, carbon dioxide, hydrogen and hydrocarbons, further contains inert components. 
     
     
         28 . The method according to  claim 7 , wherein reforming is carried out in a catalyst bed reformer at a temperature of about 900-1200° C. 
     
     
         29 . The method according to  claim 16 , wherein the molar ratio between the fresh hydrogen and CO 2  fed into the gas and used for forming carbon monoxide, respectively, is in the range of 0.9:1 to 4:1. 
     
     
         30 . The method according to  claim 14 , wherein the reversed water gas shift reaction is carried out at a temperature in the range of about 700 to 850° C. 
     
     
         31 . The method according to  claim 1 , wherein less than 10 mole-% of the carbon monoxide produced from the biomass raw material is used for producing hydrogen gas for use in the Fischer-Tropsch reactor. 
     
     
         32 . The method according to  claim 1 , wherein less than 5 mole-% of the carbon monoxide produced from the biomass raw material is used for producing hydrogen gas for use in the Fischer-Tropsch reactor. 
     
     
         33 . The method according to  claim 23 , comprising producing from the recovered hydrocarbon composition a hydrocarbon composition suitable for a fuel application having distillation cut points in the range of about 180 to 240° C.