Method for the gasification of moisture-containing hydrocarbon feedstocks

Abstract

A method for the gasification of a hydrocarbon feedstock that has a high moisture content to produce useful co-products such as high-value hydrocarbon fuels, pure H 2 , electricity, and/or ammonia. The method advantageously gasifies the carbon in the feedstock to carbon monoxide (CO) without producing large quantities of carbon dioxide (CO 2 ). Supplemental hydrogen (H 2 ) is co-produced by reacting steam (H 2 O) generated from the moisture in the hydrocarbon feedstock with a molten metal.

1 . A method for the gasification of a hydrocarbon feedstock to form a syngas, comprising the steps of: 
 (a) injecting a hydrocarbon feedstock comprising at least about 10 wt. % H 2 O into a molten metal reactor, the reactor containing a molten metal phase comprising a reactive metal and a slag phase, wherein a portion of the H 2 O from the feedstock reacts with the reactive metal to reduce the portion of the H 2 O to H 2  and form a reactive metal oxide, and wherein a first portion of carbon from the hydrocarbon feedstock reduces reactive metal oxide contained in the slag phase to the molten metal phase;    (b) during the injection of hydrocarbon feedstock, injecting oxygen into said molten metal reactor to oxidize at least a second portion of carbon from said hydrocarbon feedstock to carbon oxides; and    (c) recovering a syngas comprising H 2  and CO from the reactor, where the recovered syngas comprises not greater than about 15 vol. % CO 2 .    
     
     
         2 . A method as recited in  claim 1 , wherein the recovered syngas comprises not greater than about 10 vol. % CO 2 .  
     
     
         3 . A method as recited in  claim 1 , wherein the recovered syngas comprises not greater than about 5 vol. % CO 2 .  
     
     
         4 . A method as recited in  claim 1 , wherein the hydrocarbon feedstock is selected from the group consisting of pet coke, coal, municipal waste, rubber tires, wood and biomass.  
     
     
         5 . A method as recited in  claim 1 , wherein the hydrocarbon feedstock comprises at least about 25 wt. % H 2 O.  
     
     
         6 . A method as recited in  claim 1 , further comprising the step of injecting a second hydrocarbon feedstock into said reactor, where the second hydrocarbon feedstock comprises less H 2 O than said first hydrocarbon feedstock.  
     
     
         7 . A method as recited in  claim 1 , wherein the partial pressure ratio of oxidizing gases to total gases in the reactor as expressed by the fraction:  
       
         
           
             
               
                 ( 
                 
                   
                     
                       H 
                       2 
                     
                     ⁢ 
                     O 
                   
                   + 
                   
                     CO 
                     2 
                   
                 
                 ) 
               
               
                 ( 
                 
                   
                     H 
                     2 
                   
                   + 
                   
                     
                       H 
                       2 
                     
                     ⁢ 
                     O 
                   
                   + 
                   CO 
                   + 
                   
                     CO 
                     2 
                   
                 
                 ) 
               
             
           
         
       
       is determined for the hydrocarbon feedstock by minimizing Gibbs' free energy for the reduction reaction employing the hydrocarbon feedstock, and wherein the input rate of a reactant selected from oxygen and hydrocarbon feedstock to the reactor is adjusted to minimize the Gibbs' free energy.  
     
     
         8 . A method as recited in  claim 1 , wherein the hydrocarbon feedstock further comprises sulfur-bearing or chlorine-bearing compounds.  
     
     
         9 . A method as recited in  claim 8 , further comprising the steps of: 
 (i) recovering sulfur-containing compounds from said syngas;    (ii) oxidizing said sulfur-containing compounds to form SO 2 ;    (iii) contacting said SO 2  with H 2 S or H 2 ; and    (iv) extracting elemental sulfur from said contacting step.    
     
     
         10 . A method as recited in  claim 8 , further comprising the steps of: 
 (i) removing chlorine-containing compounds from said syngas by dissolving the chlorine-containing compounds in water; and    (ii) removing said chlorine-containing compounds by water purification.    
     
     
         11 . A method as recited in  claim 1 , wherein said reactive metal comprise iron.  
     
     
         12 . A method as recited in  claim 11 , wherein the rate of injection of the hydrocarbon feedstock is maintained such that the iron oxide content in the slag phase does not deviate during the process by more than about 5 weight percent.  
     
     
         13 . A method as recited in  claim 11 , wherein the rate of injection of the hydrocarbon feedstock is maintained such that the iron oxide content in the slag phase is at least about 30 wt. % and is not greater than about 65 wt. %.