Recovery of Co-Rich Product From a Mixed Gas Containing Heavy Hydrocarbons

• US 20090133437A1
• Filed: 07/28/2005
• Published: 05/28/2009
• Est. Priority Date: 07/28/2005
• Status: Abandoned Application

• Current Assignee: Ineos USA LLC (Ineos AG)
• Original Assignee: Ineos USA LLC (Ineos AG)
• Inventors: Reyneke, Rian, Foral, Michael J.
• Application Number:
  US11/922,760
• Publication Number:
  US 20090133437A1
• Time in Patent Office: Days
• US Class Current: 62/617
• CPC Class Codes: C01B 2203/046 Purification by cryogenic separation
• CPC Class Codes: C01B 2203/047 the impurity being carbon monoxide
• CPC Class Codes: C01B 2203/048 the impurity being an organic compound
• CPC Class Codes: C01B 3/506 at low temperatures
• CPC Class Codes: F25J 2200/70 Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
• CPC Class Codes: F25J 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/78 Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
• CPC Class Codes: F25J 2200/90 Details relating to column internals, e.g. structured packing, gas or liquid distribution
• CPC Class Codes: F25J 2205/02 using simple phase separation in a vessel or drum
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2205/30 using a washing, e.g. "scrubbing" or bubble column for purification purposes
• CPC Class Codes: F25J 2205/40 using hybrid system, i.e. combining cryogenic and non-cryogenic separation techniques
• CPC Class Codes: F25J 2205/60 using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• CPC Class Codes: F25J 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2270/02 Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/24 Quasi-closed internal or closed external carbon monoxide refrigeration cycle
• CPC Class Codes: F25J 2290/40 Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers etc.
• CPC Class Codes: F25J 3/0219 Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
• CPC Class Codes: F25J 3/0233 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0238 : separation of CnHm with 2 carbon atoms or more
• CPC Class Codes: F25J 3/0252 : separation of hydrogen production of hydrogen containing gas in general C01B3/00, e.g. separation of hydrogen or hydrogen containing gases form gaseous mixtures at low temperatures C01B3/506
• CPC Class Codes: F25J 3/0261 : separation of carbon monoxide production of carbon monoxide containing gas in general C01B32/40, C10J, C10K
• CPC Class Codes: F25J 3/0271 : separation of H2/CO mixtures, i.e. of synthesis gas production of carbon monoxide containing gas in general C01B32/40, C10J, C10K, production of hydrogen containing gas C01B3/00
• CPC Class Codes: Y02P 20/10 : Process efficiency

Abstract

A novel process is disclosed which produces a CO-rich stream from a stream containing hydrogen, carbon monoxide, methane, and components heavier than methane. The process utilizes a combined CO purification and demethanizer column (5) which reduces the overall capital cost of the process, and efficient heat integration which reduces the energy required by the process. This process is useful in recovering a CO-rich stream (10) from the effluent (1) of an autothermal cracking reactor. It is particularly useful when one or more of the heavy components (6) has a higher value as pure product than when admixed with methane (11), and when product of a purified hydrogen stream (8) is also desirable.

Claims

1. A process for the recovery of a CO-rich stream comprising at least 50 mol % carbon monoxide and at least 2 mol % hydrogen from a mixed stream comprising carbon monoxide, hydrogen, methane and hydrocarbons with two or more carbon atoms, said process comprising the steps of:

i. passing the mixed stream to a first separation step to separate the mixed stream into one or more first intermediate streams comprising hydrocarbons with two or more carbon atoms and a reduced quantity of the carbon monoxide, hydrogen and methane relative to the mixed stream, and a second intermediate stream comprising carbon monoxide, hydrogen, methane and a reduced quantity of the hydrocarbons with 2 or more carbons atoms relative to the mixed stream,

ii. passing the second intermediate stream to a second separation step to separate the second intermediate stream into one or more third intermediate streams comprising carbon monoxide and methane and a reduced quantity of hydrogen relative to the second intermediate stream, and a hydrogen-rich stream which comprises a reduced quantity of carbon monoxide and methane relative to the second intermediate stream, and

iii. passing at least one of the one or more first intermediate streams and at least one of the one or more third intermediate streams to a third separation step to recover a CO-rich stream comprising at least 50 mol % carbon monoxide and at least 2 mol % hydrogen, a methane-rich stream and a heavy hydrocarbon stream comprising hydrocarbons with 2 or more carbon atoms,

wherein the at least one of the one or more first intermediate streams and the at least one of the one or more third intermediate streams are passed to the third separation step without treatment to separate hydrogen.

2. The process of claim 1 wherein the third separation step comprises a single distillation column which acts as a combined demethanizer/CO purification column, and from which is removed a gaseous overhead stream, a liquid sidestream, and a liquid bottoms stream, as respectively said CO-rich stream, said methane-rich stream and said heavy hydrocarbon stream.

3. The process of claim 1 wherein the CO-rich stream comprises at least 80 mol % carbon monoxide and at least 5 mol % hydrogen.

4. The process of claim 2 wherein each of the one or more third intermediate streams enters the single distillation column at a location above that where the liquid sidestream is recovered, and each of the one or more first intermediate streams enters the single distillation column at a location below that where the liquid sidestream is recovered.

5. The process of claim 2 wherein the top pressure of said single distillation column is above 7 bara.

6. The process of claim 5 wherein the top pressure of said single distillation column is above 1.0 bara.

7. The process of claim 1 wherein the first separation step comprises passing the mixed stream to a chilling train comprising one or more stages of partial condensation of the process stream.

8. The process of claim 1 wherein the second separation step comprises at least one step of chilling and partial condensation of the second intermediate stream.

9. The process of claim 8 wherein the second separation step comprises at least one step of rectification of the second intermediate stream.

10. The process of claim 1 in which the hydrogen in said CO-rich stream is removed through adsorption onto a suitable adsorbent or through reaction with the carbon monoxide contained in said CO-rich stream to produce a purified carbon monoxide stream containing less than 1 mol % hydrogen.

11. The process of claim 1 wherein at least a portion of said CO-rich stream is used as at least a portion of the working fluid in a CO-rich vapor recompression refrigeration system, the CO-rich vapor recompression refrigeration system providing process chilling duty to one or more of the first, second, and/or third separation steps.

12. The process of claim 11 in wherein said CO-rich vapor recompression refrigeration system comprises the steps of:

i. Compressing at least a portion of said CO-rich stream to a relatively high pressure to form a relatively high-pressure CO-rich stream,

ii. Cooling and partially condensing at least a portion of the relatively high-pressure CO-rich stream of step (i) to produce a cooled and at least partially condensed working fluid stream,

iii. Reducing the pressure of the cooled and at least partially condensed working fluid stream of step (ii) to produce a reduced-pressure working fluid stream,

iv. Heating and at least partially vaporizing the reduced-pressure working fluid stream of step (iii) to provide the process chilling duty to one or more of the first, second, and/or third separation steps and produce a heated reduced pressure working fluid stream, and

v. Recompressing at least a portion of the heated reduced pressure working fluid stream in step (i)

13. The process of claim 12 in which the methane-rich stream is recovered as a liquid stream and at least a portion of said methane-rich stream is reduced in pressure, warmed, and at least partially vaporized to provide at least a portion of the cooling duty needed in step (ii).

14. The process of claim 13 wherein said methane-rich stream is optionally pumped and then cooled to a temperature at least 5°

C. below its bubble point before it is reduced in pressure, warmed, and at least partially vaporized, said bubble point being defined at the pressure at which said methane-rich stream is recovered and prior to the optional pumping step.

15. The process of claim 13 wherein the at least a portion of said methane-rich stream is first mixed with at least a portion of said hydrogen-rich stream and the combined stream is warmed and at least partially vaporized to provide at least a portion of the cooling duty needed in step (ii).

16. The process of claim 1 wherein the methane-rich stream contains less than 5 mol % hydrocarbons with 2 or more carbon atoms.

17. The process of claim 1 wherein the concentration of hydrogen in the hydrogen-rich stream is at least 80 mol %.

18. The process of claim 1 wherein the concentration of hydrogen in the CO-rich stream is no more than 20 mol %.

19. The process of claim 1 wherein at least a portion of the CO-rich stream is mixed with an externally-generated synthesis gas stream which has a different molar hydrogen to carbon monoxide ratio than the CO-rich stream to produce a combined synthesis gas stream which has a molar hydrogen to carbon monoxide ratio which is different from that of either the CO-rich stream or the externally-generated synthesis gas stream.