Process for separation of hydrocarbon gases

• US 4,710,214 A
• Filed: 12/19/1986
• Issued: 12/01/1987
• Est. Priority Date: 12/19/1986
• Status: Expired due to Term

• Current Assignee: MW Kellogg Limited (KBR Incorporated)
• Original Assignee: MW Kellogg Limited (KBR Incorporated)
• Inventors: Durr, Charles A., Sharma, Shanmuk, Hill, Donnie K.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/944,272
• Time in Patent Office: 347 Days
• Field of Search: 62/23, 62/24, 62/27, 62/28, 62/32, 62/34, 62/36, 62/38, 62/39, 62/42, 62/44
• US Class Current: 62/621
• CPC Class Codes: C07C 7/09 by fractional condensation
• CPC Class Codes: F25J 2200/04 in a dual pressure main column system
• 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 2200/72 Refluxing the column with at least a part of the totally condensed overhead gas
• 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 2210/02 Multiple feed streams, e.g. originating from different sources
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• CPC Class Codes: F25J 2235/60 the fluid being (a mixture of) hydrocarbons
• 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 2270/02 Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/04 Internal refrigeration with work-producing gas expansion loop
• 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 3/0242 separation of CnHm with 3 carbon atoms or more
• CPC Class Codes: F25J 3/0247 separation of CnHm with 4 carbon atoms or more

Abstract

A process for separation of a high pressure gas stream such as light refinery gases in which the gas mixture is expanded, preferably through a turbine, and separated into first vapor and liquid portions. The first vapor portion may be recovered as, for example, methane-rich product gas. The first liquid portion is raised to an intermediate pressure, revaporized, and introduced to a fractionator from which an ethane-containing stream is recovered. The ethane-containing stream is then cooled and separated into a second vapor portion and a second liquid portion which is then expanded and combined with the expanded starting gas mixture to increase the amount of refrigeration that may be recovered from the first liquid stream prior to its fractionation.

Claims

1. A process for separation of a high pressure gaseous stream containing mixed light hydrocarbons which comprises:

(a) expanding the high pressure gaseous stream to a first intermediate pressure and introducing the resulting expanded stream to a first single equilibrium separation zone;

(b) recovering a first vapor stream and a separate first liquid stream from the first single equilibrium separation zone;

(c) elevating the first liquid stream to a second intermediate pressure;

(d) recovering refrigeration from the first liquid stream at the second intermediate pressure through indirect heat exchange by cooling the high pressure gaseous stream prior to its expansion thereby forming a revaporized stream from the first liquid stream at the second intermediate pressure and introducing the revaporized stream to a multi-equilibrium separation zone;

(e) recovering and cooling an ethane-containing gaseous mixture from the multi-equilibrium separation zone;

(f) introducing the cooled ethane-containing gaseous mixture to a second single equilibrium separation zone;

(g) recovering a second vapor stream and a separate second liquid stream from the second single equilibrium zone; and

(h) expanding the second liquid stream into the first single equilibrium separation zone.

2. The process of claim 1 wherein the high pressure gaseous stream is expanded through a turbine.

3. The process of claim 1 wherein the high pressure gaseous stream contains hydrogen, methane, and ethane, the first and second intermediate pressures are between 3 and 35 kg/cm² a, and the high pressure gaseous stream is at a pressure between 5 and 55 kg/cm² a.

4. The process of claim 1 wherein the high pressure gaseous stream contains between 10 and 90 volume percent nitrogen and the first and second vapor streams contain principally nitrogen.