Methods, Systems, And Apparatuses For Recycling Fischer-Tropsch Water And Fischer-Tropsch Tail Gas

Abstract

A method of producing reformed gas as part of a Fischer-Tropsch (“FT”) hydrocarbon synthesis is disclosed, including the steps of superheating at least a first portion of an FT tail gas produced as a by-product of an FT synthesis process, and forming a mixed gas by injecting at least a portion of an FT water stream, produced as a by-product of an FT synthesis process, into the superheated FT tail gas to form a mixed gas. The mixed gas is used as a feed to a front end of a syngas preparation unit. The amount of at least a portion of the FT water stream is selected to keep the mixed gas at least mostly and preferably entirely in a vapor phase. In some embodiments, a water-gas shift reactor converts the mixed gas to a converted mixed gas upstream of the front end. Other methods, apparatuses and systems are disclosed.

What is claimed is: 
     
         1 . A system for producing a syngas, the system comprising:
 a. a superheater for superheating a Fischer-Tropsch (“FT”) tail gas produced by an FT reactor;   b. an injector for injecting at least a portion of an FT water stream produced by an FT reactor into the superheated FT tail gas to form a mixed gas for use as a feed to a front end of a syngas preparation unit.   
     
     
         2 . The system of  claim 1 , wherein the syngas preparation unit comprises a steam methane reformer. 
     
     
         3 . The system of  claim 1 , wherein the syngas preparation unit comprises an autothermal reformer. 
     
     
         4 . The system of  claim 1 , wherein the syngas preparation unit comprises a partial oxidation reformer. 
     
     
         5 . The system of  claim 1 , wherein, wherein the syngas preparation unit comprises a hybrid reformer. 
     
     
         6 . The system of  claim 1 , wherein the injector is configured to inject a pre-selected amount of the at least a portion of the FT water stream into the superheated FT tail gas to form the mixed gas, the pre-selected amount being selected to keep the mixed gas in at least a mostly vapor phase. 
     
     
         7 . The system of  claim 6 , further comprising a separator drum positioned to remove excess water from the mixed gas in the mostly vapor phase. 
     
     
         8 . The system of  claim 1 , wherein the injector is configured to inject a pre-selected amount of the at least a portion of the FT water stream into the superheated FT tail gas, the pre-selected amount being selected to keep the mixed gas in an entirely vapor phase. 
     
     
         9 . The system of  claim 1 , wherein the injector is configured to inject a pre-selected amount of the at least a portion of the FT water stream into the superheated FT tail gas, the pre-selected amount being selected to keep the mixed gas in a phase that is at least 75% vapor by weight. 
     
     
         10 . The system of  claim 1 , further comprising:
 d. a connection between a first flowline and a second flowline, carrying the sweet natural gas and the FT tail gas respectively, upstream of the injection of the at least a portion of the FT water stream, so that the injection of the at least a portion of the FT water is into a mixture of the sweet natural gas and the FT tail gas.   
     
     
         11 . The system of  claim 10 , wherein a carbon dioxide stream is added to the FT tail gas upstream of the injection of the at least a portion of the FT water stream. 
     
     
         12 . The system of  claim 11 , wherein the carbon dioxide stream added to the FT tail gas has been recovered by a carbon dioxide removal unit from a second portion of the FT tail gas. 
     
     
         13 . The system of  claim 10 , wherein the injection of at least a portion of the FT water stream is performed in two or more stages, the second stage using a second injector, with wherein both the injector and the second injector are configured to inject first and second portions of the FT water stream into the mixture of the superheated FT tail gas and sweet natural gas in first and second amounts, respectively, that keep the mixed gas in an at least mostly vapor phase, and further comprising:
 e. a separator drum positioned to remove excess water from the mixed gas.   
     
     
         14 . The system of  claim 1 , wherein the injection of at least a portion of the FT water stream is performed in two or more stages, the second stage using a second injector, with wherein both the injector and the second injector are configured to inject first and second portions of the FT water stream into the mixture of the superheated FT tail gas and sweet natural gas in first and second amounts respectively in first and second amounts, respectively, that keep the mixed gas in an entirely vapor phase. 
     
     
         15 . The system of  claim 10 , further comprising:
 e. a water-gas shift reactor, located downstream of the injection of the at least a portion of the FT tail gas, that forms a converted mixed gas from the mixed gas; and   f. a connection downstream of the water-gas shift reactor and upstream of the front end of the syngas preparation unit by which steam is added to the converted mixed gas to form a converted feed, comprising a feed for the front end of the syngas preparation unit.   
     
     
         16 . An apparatus for preparing a Fischer-Tropsch (“FT”) tail gas produced by an FT reactor and an FT water produced by an FT reactor for recycling into a front end of a syngas preparation unit, comprising:
 a. a superheater for superheating the FT tail gas; and 
 b. an injector for injecting at least a portion of the FT water stream into the superheated FT tail gas to form a mixed gas, while keeping the mixed gas in at least a mostly vapor phase. 
 
     
     
         17 . The apparatus of  claim 16 , wherein the injector injects at least a portion of the FT water stream into the superheated FT tail gas to form the mixed gas, while keeping the mixed gas in an entirely vapor phase. 
     
     
         18 . The apparatus of  claim 17 , further comprising:
 c. a water-gas shift reactor, downstream of the injection of the at least a portion of the FT tail gas, that forms a converted mixed gas from the mixed gas; and   d. a connection downstream of the water-gas shift reactor and upstream of the front end of the syngas preparation unit by which steam is added to the converted mixed gas to form a converted feed, comprising a feed for the front end of the syngas preparation unit.   
     
     
         19 . The apparatus of  claim 18 , further comprising:
 e. a connection between a first and a second flowline, carrying a sweet natural gas and the FT tail gas respectively, upstream of the injection of the at least a portion of the FT water stream, so that the injection of the at least a portion of the FT water is into a mixture of the sweet natural gas and the FT tail gas.   
     
     
         20 . The apparatus of  claim 19 , further comprising:
 f. a connection between the second flowline and a third flowline carrying carbon dioxide, upstream of the injection of the at least a portion of the FT water stream, so that the injection of the at least a portion of the FT water is into a mixture of the sweet natural gas, the carbon dioxide and the FT tail gas.   
     
     
         21 . A system for producing Fischer-Tropsch (“FT”) hydrocarbons, comprising:
 a. a syngas preparation unit having a feed comprising a carbonaceous feed and a steam stream for producing a syngas; 
 b. a syngas conditioning unit fluidly connected to the syngas output of the syngas preparation unit for removing condensate from the syngas; 
 c. a FT reactor having an FT catalyst fluidly connected to the conditioned syngas output of the syngas conditioning unit to produce, under FT operating conditions, a stream of liquid FT hydrocarbons, with an FT tail gas and an FT water stream; 
 d. a superheater for superheating FT tail gas; 
 e. an injector for injecting at least a portion of the FT water stream into the superheated FT tail gas to form a mixed gas to be added to the feed of the syngas preparation unit, injector having a configuration to inject a pre-selected amount of the at least a portion of the FT water stream into the superheated FT tail gas to form the mixed gas, the pre-selected amount being selected to keep the mixed gas in at least a mostly vapor phase. 
 
     
     
         22 . The system of  claim 21 , the injector having a configuration for injecting at least a portion of the FT water stream into the superheated FT tail gas to form the mixed gas, while keeping the mixed gas in an entirely vapor phase.