Oxidative Coupling of Methane Implementations for Olefin Production

Abstract

The present disclosure provides oxidative coupling of methane (OCM) systems for small scale and world scale production of olefins. An OCM system may comprise an OCM subsystem that generates a product stream comprising C 2+ compounds and non-C 2+ impurities from methane and an oxidizing agent. At least one separations subsystem downstream of, and fluidically coupled to, the OCM subsystem can be used to separate the non-C 2+ impurities from the C 2+ compounds. A methanation subsystem downstream and fluidically coupled to the OCM subsystem can be used to react H 2 with CO and/or CO 2 in the non-C 2+ impurities to generate methane, which can be recycled to the OCM subsystem. The OCM system can be integrated in a non-OCM system, such as a natural gas liquids system or an existing ethylene cracker.

What is claimed is: 
     
         1 . A method for performing oxidative coupling of methane (OCM), comprising:
 (a) in an OCM unit, reacting oxygen (O 2 ) with methane (CH 4 ) in an OCM process to yield a product stream comprising (i) compounds with two or more carbon atoms (C 2+  compounds), including ethylene (C 2 H 4 ) and propylene (C 3 H 6 ), (ii) hydrogen (H 2 ), and (iii) carbon monoxide (CO) or carbon dioxide (CO 2 );   (b) directing said product stream to a substantially adiabatic cracking unit that increases a concentration of said C 2 H 4  in said product stream; and   (c) directing said H 2  and CO or CO 2  in said product stream to a methanation unit that reacts said H 2  with said CO or CO 2  to form CH 4 .   
     
     
         2 . The method of  claim 1 , further comprising directing one or more alkanes to said substantially adiabatic cracking unit. 
     
     
         3 . The method of  claim 2 , wherein said one or more alkanes are directed to said substantially adiabatic cracking unit along a stream external to said OCM unit. 
     
     
         4 . The method of  claim 2 , wherein said one or more alkanes comprise ethane (C 2 H 6 ), and wherein said substantially adiabatic cracking unit cracks said C 2 H 6 . 
     
     
         5 . The method of  claim 4 , wherein at least a portion of said C 2 H 6  is produced in said OCM unit. 
     
     
         6 . The method of  claim 1 , wherein said OCM unit is substantially adiabatic. 
     
     
         7 . The method of  claim 1 , further comprising, subsequent to (b), increasing a pressure of said product stream. 
     
     
         8 . The method of  claim 7 , wherein said pressure is increased to up to about 60 bar. 
     
     
         9 . The method of  claim 7 , wherein said pressure is increased with the aid of a compressor downstream of said a substantially adiabatic cracking unit. 
     
     
         10 . The method of  claim 1 , further comprising, subsequent to (b), enriching said C 2 H 4  in said product stream. 
     
     
         11 . The method of  claim 10 , wherein said C 2 H 4  is enriched using at least a portion of heat liberated from said OCM process. 
     
     
         12 . The method of  claim 10 , wherein said C 2 H 4  is enriched in a separations unit. 
     
     
         13 . The method of  claim 12 , wherein said separations unit yields a stream comprising ethane that is directed to said substantially adiabatic cracking unit. 
     
     
         14 . The method of  claim 1 , wherein said OCM unit is integrated with said a substantially adiabatic cracking unit. 
     
     
         15 . The method of  claim 1 , wherein said OCM unit comprises a plurality of OCM reactors. 
     
     
         16 . The method of  claim 1 , wherein said a substantially adiabatic cracking unit comprises a plurality of cracking vessels. 
     
     
         17 . The method of  claim 1 , wherein said methanation unit operates at a pressure from about 3 bar to 50 bar and a temperature from about 150° C. to 400° C. 
     
     
         18 . The method of  claim 1 , wherein said product stream has a pressure of at least about 10 bar. 
     
     
         19 . The method of  claim 1 , wherein said methanation unit comprises a plurality of methanation reactors. 
     
     
         20 . The method of  claim 1 , further comprising directing at least a portion of said CH 4  formed in said methanation unit to said OCM unit. 
     
     
         21 . The method of  claim 20 , wherein at least a portion of said CH 4  formed in said methanation unit is returned to said OCM unit through a heat exchanger. 
     
     
         22 . The method of  claim 1 , wherein said methanation unit has a methanation catalyst that converts said CO or CO 2  into CH 4  at a selectivity for formation of CH 4  that is at least about 10-fold greater than a selectivity of said catalyst for formation of coke from said CO or CO 2 . 
     
     
         23 . The method of  claim 1 , further comprising using a power generation unit in thermal communication with said OCM unit to convert at least a portion of heat liberated in said OCM process to power.