Process and apparatus for the production of hydrocarbon compounds from methane
View Patent ↗Higher molecular weight hydrocarbon compounds or oxygenates are produced from a gas comprising methane in a process comprising the steps of generating synthesis gas (“syngas”) comprising carbon monoxide and hydrogen by reaction of a gas comprising methane with steam and/or an oxidant gas comprising oxygen, producing higher molecular weight hydrocarbon compounds or oxygenates in a syngas conversion process, removing offgas comprising unreacted hydrogen and unreacted carbon monoxide from said syngas conversion process and separating cryogenically unreacted hydrogen from said offgas or from a gas derived therefrom to produce separated hydrogen product that is substantially free of unreacted carbon monoxide and a first cryogenic liquid comprising unreacted carbon monoxide. The unreacted hydrogen is preferably separated from the offgas in a liquid methane wash column.
1. A process for producing higher molecular weight hydrocarbon compounds or oxygenates from a gas comprising methane, said process comprising:
generating synthesis gas (syngas) comprising carbon monoxide and hydrogen by reaction of a gas comprising methane with steam and/or an oxidant gas comprising oxygen;
producing higher molecular weight hydrocarbon compounds or oxygenates in a syngas conversion process;
removing offgas comprising unreacted hydrogen and unreacted carbon monoxide from said syngas conversion process;
separating unreacted hydrogen from said offgas or from a gas derived therefrom to produce separated hydrogen product, wherein unreacted hydrogen is separated in a cryogenic separation process to produce separated hydrogen product that is substantially free of unreacted carbon monoxide and a first cryogenic liquid comprising unreacted carbon monoxide and argon;
combining the separated hydrogen product with the syngas prior to the syngas conversion process;
separating unreacted carbon monoxide from said first cryogenic liquid or from a cryogenic liquid derived therefrom in a cryogenic distillation column to produce separated carbon monoxide product and substantially carbon monoxide-free cryogenic liquid; and
removing at least one argon-enriched stream from a region above a bottom of the cryogenic distillation column.
2. A process as claimed in claim 1 wherein the cryogenic separation process is a liquid methane wash.
3. A process as claimed in claim 1 , wherein higher molecular weight hydrocarbon compounds are produced, said process further comprising using separated hydrogen product for hydrogenation of a fraction of said higher molecular weight hydrocarbon compounds to produce liquid hydrocarbon compounds.
4. A process as claimed in claim 3 , wherein said separated hydrogen product is used in the hydrogenation of said hydrocarbon fraction without purification.
5. A process as claimed in claim 1 , further comprising recycling separated carbon monoxide product for conversion into higher molecular weight hydrocarbon compounds or oxygenates.
6. A process as claimed in claim 1 , wherein the substantially carbon monoxide-free cryogen liquid is substantially pure liquid methane, said process further comprising recycling a vaporised portion of said substantially pure liquid methane for conversion into syngas.
7. A process as claimed in claim 1 , wherein said off gas further comprises helium, said process further comprising separating helium from said separated hydrogen product using a membrane separation system.
8. A process as claimed in claim 1 , wherein said offgas further comprises low molecular weight hydrocarbon compounds, said process further comprising:
cooling said off gas or a gas derived therefrom to condense said low molecular weight hydrocarbon compounds to produce liquefied petroleum gas (“LPG”) and removing said LPG to produce substantially LPG-free offgas;
cooling and at least partially condensing said substantially LPG-free offgas to produce partially condensed substantially LPG-free offgas; and
separating unreacted hydrogen from a vapour portion of said partially condensed substantially LPG-free offgas in said cryogenic separation process to produce said separated hydrogen product and said first cryogenic liquid.
9. A process as claimed in claim 8 , wherein unreacted hydrogen is present in said first cryogenic liquid, said process further comprising separating unreacted hydrogen from said first cryogenic liquid or a cryogenic liquid derived therefrom in a further cryogenic separation process to produce separated hydrogen fuel by-product and a second cryogenic liquid comprising unreacted carbon monoxide.
10. A process as claimed in claim 9 , wherein the further cryogenic separation process is a liquid methane wash.
11. A process as claimed in claim 9 , wherein said offgas further comprises helium and wherein separated hydrogen product is recycled for conversion into higher molecular weight hydrocarbon compounds, said process further comprising removing a portion of said separated hydrogen product once the concentration of the helium in the separated hydrogen product is between from 1 mol % to 20 mol %.
12. A process as claimed in claim 11 wherein said portion is adjusted in flowrate so that the helium concentration reaches the required concentration.
13. A process as claimed in claim 1 , further comprising at least partially vaporising liquid nitrogen (“LIN”) to provide refrigeration duty to keep the process in heat balance.
14. A process as claimed in claim 1 , wherein the oxidant gas is oxygen with a purity below 99 mol % produced in an integrated cryogenic air separation process, said LIN being produced in said air separation process.
15. A process as claimed in claim 1 , wherein said separated hydrogen product is recycled for conversion into higher molecular weight hydrocarbon compounds.
16. A process as claimed in claim 1 , wherein said syngas is generated by partially oxidizing natural gas with oxygen and by refining natural gas with steam.
17. A process as claimed in claim 1 , wherein said syngas conversion process is a Fisher-Tropsch (“FT”) process.