Modification of a methanol plant for converting natural gas to liquid hydrocarbons

Abstract

A gas-to-liquid (GTL) process and system for converting a natural gas) into liquid hydrocarbons (e.g. diesel, naphtha, distillates, etc.) wherein the equipment subsystems from existing gas-to-methanol plants are re-utilized in the (GTL) process. The syngas generator from the methanol plant is used to generate syngas in the present process. The syngas is then adjusted to remove CO 2 and H 2 before the syngas is passed through a Fischer-Tropsch (FT) reactor to convert the syngas to liquid hydrocarbons. The FT reactor is comprised of the same equipment that was use previously to convert syngas into methanol except for the respective catalysts. The liquid hydrocarbons are then upgraded and separated into individual hydrocarbon products.

1 - 9 . (canceled)  
   
   
       10 . A system for converting natural gas into liquid petroleum products, the system comprising: 
 a syngas synthesis subsystem for converting natural gas to a syngas which, in turn, comprises carbon monoxide, carbon dioxide, hydrogen, and water;    a syngas adjusting subsystem for removing carbon dioxide and hydrogen from said syngas to produce an adjusted syngas; and    a product synthesis subsystem for converting said adjusted syngas into said liquid hydrocarbon products.    
   
   
       11 . The system of  claim 10  wherein said syngas synthesis and compression subsystem comprises: 
 a steam reformer for converting said natural gas to said syngas.    
   
   
       12 . The system of  claim 11  wherein said product synthesis subsystem comprises; 
 at least one Fischer-Tropsch reactor.    
   
   
       13 . The system of  claim 10  wherein said syngas adjusting subsystem comprises: 
 a means for removing said carbon dioxide from said syngas; and    a means for removing hydrogen from said syngas.    
   
   
       14 . The system of  claim 13  including: 
 means for mixing at least some of said removed carbon dioxide into said natural gas before said natural gas enters said steam reformer.    
   
   
       15 . The system of  claim 10  including: 
 a liquid hydrocarbon products upgrading subsystem comprising:    a distillation column.    
   
   
       16 . The system of  claim 10  wherein said syngas synthesis subsystem and said product synthesis subsystem are comprised of previously used components from the syngas synthesis subsystem and the product synthesis subsystem of a plant which was previously used to convert natural gas to methanol.  
   
   
       17 - 29 . 
   
   
       30 . A system for converting natural gas into liquid petroleum products using components of a previous natural gas to methanol conversion plant, said system comprising: 
 a syngas synthesis subsystem comprising: 
 a syngas generator from said previous natural gas to methanol conversion plant for converting natural gas to a syngas which, in turn, comprises carbon monoxide, carbon dioxide, hydrogen, and water;  
   a syngas adjusting subsystem comprising: 
 means for removing at least a portion of said carbon dioxide from said syngas; and  
 means for removing at least a portion of said hydrogen from said syngas to produce an adjusted syngas having a ration of hydrogen to carbon dioxide of about 2; and  
   a product synthesis subsystem for converting said adjusted syngas into said liquid hydrocarbon products.    
   
   
       31 . The system of  claim 30  wherein said syngas generator comprises: 
 a steam reformer from said previous natural gas to methanol plant for converting said natural gas to said syngas.    
   
   
       32 . The system of  claim 31  wherein said product synthesis subsystem comprises; 
 at least one Fischer-Tropsch reactor from said previous natural gas to methanol plant.    
   
   
       33 . The system of  claim 32  wherein said Fischer-Tropsch reactor is comprised of a pressure vessel_having a plurality of tubes therein which are filled with a catalyst for converting the adjusted syngas to said liquid hydrocarbons.  
   
   
       34 . The system of  claim 32  including: 
 a product upgrading subsystem adapted to receive said liquid hydrocarbons from said reactor in said product synthesis subsystem and separate said liquid hydrocarbons products into the desired individual products.    
   
   
       35 . The system of  claim 30  wherein one of said desired individual products is diesel.  
   
   
       36 . The system of  claim 34  including: 
 means within said product synthesis subsystem for recycling a portion of said liquid hydrocarbon products to said Fischer-Tropsch reactor before said liquid hydrocarbons enter said product upgrading subsystem to control the temperature in said reactor.    
   
   
       37 . The system of  claim 36  including: 
 means within said product synthesis subsystem for recycling a portion of said liquid hydrocarbon products to said Fischer-Tropsch reactor after said liquid hydrocarbons have been processed in said product upgrading subsystem to control the temperature in said reactor.    
   
   
       38 . The system of  claim 36  including: 
 means for recycling carbon dioxide separated from said syngas in said syngas adjusting subsystem to the inlet natural gas stream before said inlet stream enters said syngas synthesis subsystem.    
   
   
       39 . The system of  claim 38  including: 
 means for returning at least a portion of said removed hydrogen to said syngas synthesis subsystem for use as fuel therein.    
   
   
       40 . The system of  claim 39  including: 
 means for returning at least a portion of said removed hydrogen to said product upgrading subsystem for use in upgrading said liquid hydrocarbons.    
   
   
       41 . The system of  claim 40  wherein said product upgrading subsystem includes: 
 a fractionating column adapted to receive said liquid hydrocarbon products from said Fischer-Trospch reactor for separating said liquid hydrocarbon products into individual liquid hydrocarbon products.    
   
   
       42 . The system of  claim 41  wherein one of said desired individual products is diesel.