Ethylene-to-liquids systems and methods
Integrated systems are provided for the production of higher hydrocarbon compositions, for example liquid hydrocarbon compositions, from methane using an oxidative coupling of methane system to convert methane to ethylene, followed by conversion of ethylene to selectable higher hydrocarbon products. Integrated systems and processes are provided that process methane through to these higher hydrocarbon products.
1. A method for performing oxidative coupling of methane (OCM), comprising:
(a) directing oxygen (O 2 ) and methane (CH 4 ) to an OCM unit that is upstream of a separations unit, wherein said OCM unit is integrated with and in fluid communication with a cracking unit, and wherein in said OCM unit, said O 2 and said CH 4 react in an OCM process to yield compounds with two or more carbon atoms (C 2+ compounds), including ethylene (C 2 H 4 );
(b) directing at least a portion of said C 2+ compounds to said cracking unit to yield a first stream comprising (i) compounds having triple bonds or (ii) compounds having more than one double bond, wherein said cracking unit operates substantially adiabatically, and wherein said at least said portion of said C 2+ compounds is directed to said cracking unit without passage through said separations unit; and
(c) directing said first stream to said separations unit to yield a second stream having a lower concentration of said (i) compounds having triple bonds or (ii) compounds having more than one double bond with respect to said first stream.
2. The method of claim 1 , wherein said OCM unit has an inlet temperature between about 450° C. and about 600° C.
3. The method of claim 1 , wherein said OCM unit has a pressure between about 15 pounds per square inch gauge (psig) and about 125 psig.
4. The method of claim 1 , wherein said OCM process has a C 2+ selectivity of at least about 50%.
5. The method of claim 1 , further comprising directing said second stream to an ethylene-to-liquids (ETL) unit to convert C 2 H 4 in said second stream to yield an ETL product stream comprising higher hydrocarbon product(s).
6. The method of claim 5 , wherein said second stream, when directed to said ETL unit, has less than about 100 parts per million (ppm) of acetylene.
7. The method of claim 5 , wherein said second stream, when directed to said ETL unit, has less than or equal to about 5 mol % carbon monoxide (CO).
8. The method of claim 5 , wherein said ETL product stream has less than about 50 weight percent (wt %) water.
9. The method of claim 5 , wherein said ETL unit is operated at a temperature greater than or equal to about 200° C.
10. The method of claim 5 , wherein said ETL unit is operated at a pressure greater than or equal to about 200 pounds per square inch.
11. The method of claim 5 , further comprising directing at least a portion of said ETL product stream to an additional separations unit that recovers a liquid stream comprising said higher hydrocarbon product(s) and a gas stream comprising hydrogen (H 2 ) and CO or carbon dioxide (CO 2 ).
12. The method of claim 11 , further comprising directing said gas stream to a methanation unit to react said H 2 with said CO or CO 2 to form CH 4 .
13. The method of claim 12 , further comprising directing at least a portion of said CH 4 from said methanation unit to said OCM unit.
14. The method of claim 1 , wherein said at least said portion of said C 2+ compounds is directed to a treatment unit prior to being directed to said cracking unit.
15. The method of claim 1 , wherein an inlet temperature of said OCM unit is at most about 600° C.
16. The method of claim 1 , wherein said OCM unit comprises a plurality of OCM reactors.
17. The method of claim 1 , wherein said cracking unit comprises a plurality of cracking vessels.
18. The method of claim 1 , further comprising directing one or more alkanes to said cracking unit along a stream external to said OCM unit.
19. The method of claim 1 , wherein said first stream comprises said compounds having triple bonds and said compounds having more than one double bond.