Combined synthesis gas separation and LNG production method and system

• US 20090205367A1
• Filed: 02/15/2008
• Published: 08/20/2009
• Est. Priority Date: 02/15/2008
• Status: Active Grant

• Current Assignee: Black & Veatch International Company (Black & Veatch Corporation)
• Original Assignee: Black & Veatch International Company (Black & Veatch Corporation)
• Inventors: Price, Brian C.
• Granted Patent: US 9,243,842 B2
• Time in Patent Office: Days
• US Class Current: 62/612
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2215/04 Recovery of liquid products
• CPC Class Codes: F25J 2240/02 Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
• CPC Class Codes: F25J 2270/12 External refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/42 Quasi-closed internal or closed external nitrogen refrigeration cycle
• CPC Class Codes: F25J 2270/66 Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
• CPC Class Codes: F25J 3/0223 H2/CO mixtures, i.e. synthesis gas; Water gas or shifted synthesis gas production of carbon monoxide containing gas in general C01B32/40, C10J, C10K; production of hydrogen containing gas C01B3/00
• CPC Class Codes: F25J 3/0233 separation of CnHm with 1 carbon atom or more
• 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

Abstract

A method and system for the separation of a synthesis gas and methane mixture which contains carbon monoxide, hydrogen and methane with the process producing synthesis gas and liquid natural gas (LNG).

Claims

1. A method for separating a feed gas stream containing carbon monoxide, hydrogen and methane into a gas stream containing carbon monoxide and hydrogen and a liquefied gas stream containing methane, the method comprising:

a) cooling the feed gas stream to a temperature from about −

145 to about −

160°

C. at a pressure from about 4 to about 6 MPa to produce a cold mixed gas and liquid gas stream; and

,

b) fractionating the cold mixed gas and liquid stream in a fractionator to produce a carbon monoxide and hydrogen stream (CO/H₂) and a liquefied gas stream comprising methane.

2. The method of claim 1 wherein the cold mixed gas and liquid stream is separated into a gas stream and a liquid stream and wherein the gas stream is expanded and wherein the expanded gas stream and the liquid stream are charged to a fractionator.

3. The method of claim 1 wherein the feed gas stream is cooled to a selected temperature from about −

70 to about −

100°

C., passed from a refrigeration heat exchanger to heat a reboiler for a fractionator and thereafter returned to the refrigeration heat exchanger.

4. The method of claim 1 wherein the carbon monoxide and hydrogen stream is recovered as a product stream at a temperature of about 30°

C. and at a pressure of about 2.4 MPa.

5. The method of claim 1 wherein the liquefied gas stream is passed in heat exchange with the carbon monoxide and hydrogen stream after fractionation.

6. The method of claim 1 wherein at least a portion of the CO/H₂ overhead stream from the fractionator is chilled by heat exchange with nitrogen and thereafter passed in heat exchange with a liquefied gas stream recovered as a fractionator bottoms stream.

7. A system for separating a feed gas stream containing carbon monoxide, hydrogen and methane into a carbon monoxide/hydrogen (CO/H₂) gas stream containing carbon monoxide and hydrogen and a liquefied gas stream containing methane, the system comprising:

a) a refrigeration heat exchanger having a feed gas stream inlet, a refrigerant inlet, a refrigerant expansion valve, a spent refrigerant outlet and a cold mixed gas and liquid stream outlet; and

,

b) a fractionator having a cold mixed gas and liquid stream inlet in fluid communication with the refrigeration heat exchanger cold mixed gas and liquid stream outlet, a CO/H₂ gas stream outlet and a liquefied gas stream outlet.

8. The system of claim 7 wherein the system includes a heat exchanger in fluid communication with the liquefied gas stream outlet and the CO/H₂ gas stream outlet and adapted to pass the CO/H₂ gas stream in heat exchange contact with the liquefied gas stream.

9. The system of claim 7 wherein the CO/H₂ gas stream is passed to a reflux drum wherein a portion of the CO/H₂ stream is passed from the reflux drum via a line to an inlet to an upper portion of the fractionator as a reflux stream.

10. A system for separating a feed gas stream containing carbon monoxide, hydrogen and methane into a carbon monoxide/hydrogen (CO/H₂) gas stream containing carbon monoxide and hydrogen and a liquefied gas stream containing methane, the system comprising:

a) a refrigeration heat exchanger having a feed gas stream inlet, a refrigerant inlet, a refrigerant expansion valve, a spent refrigerant outlet and a cold mixed gas and liquid stream outlet;

b) a cold separator having a cold mixed gas and liquid stream inlet in fluid communication with the cold mixed gas and liquid stream outlet from the refrigerant heat exchanger and having a cold gas stream outlet and a cold liquid stream outlet;

c) a fractionator having a cold gas stream inlet in fluid communication with the cold gas stream outlet from the cold separator and adapted to pass the cold gas stream into the fractionator, the fractionator having a cold liquid stream inlet in fluid communication with the cold liquid outlet stream and adapted to pass the cold liquid stream into the fractionator, a fractionator overhead gas outlet, a reflux inlet and a liquefied gas stream outlet;

d) a CO/H₂ gas stream chilling heat exchanger adapted to pass a fractionator overhead gas stream in heat exchange contact with a chilling stream to produce a chilled CO/H₂ gas stream via a chilled CO/H₂ gas stream outlet;

e) a reflux drum having at least one of a fractionator overhead gas inlet and a chilled CO/H₂ gas stream inlet, a reflux drum outlet in fluid communication with the fractionator reflux inlet and a reflux drum overhead gas outlet;

f) a liquefied gas stream heat exchanger in fluid communication with the reflex drum overhead gas outlet and the liquefied gas stream from the fractionator liquefied gas stream outlet to warm the reflux drum overhead gas outlet stream to produce a warmed reflux drum overhead gas stream and a chilled liquefied gas stream for discharge as a product stream; and

,

g) a first compressor in fluid communication with and driven by the cold gas stream from the cold gas stream outlet from the cold separator to produce an expanded cold gas stream and drive a second compressor in fluid communication with the warmed reflux drum overhead gas stream to compress the reflux drum overhead gas stream to produce a CO/H₂ gas stream.

11. The system of claim 10 wherein a warmed chilling stream compressor is positioned in fluid communication with the CO/H₂ gas stream chilling heat exchanger outlet and a warmed chilling stream inlet into the heat exchanger.

12. The system of claim 10 wherein the cold gas steam outlet from the cold separator is in fluid communication with a cold gas expander having a reduced pressure cold gas outlet in fluid communication with the cold gas stream inlet into the fractionator.

13. The system of claim 10 wherein the system includes a nitrogen refrigerant loop wherein nitrogen is compressed cooled and expanded to produce the chilling stream.