Hydrocarbon gas processing

• US 9,637,428 B2
• Filed: 08/18/2014
• Issued: 05/02/2017
• Est. Priority Date: 09/11/2013
• Status: Active Grant

• Current Assignee: UOP Llc (Honeywell International Inc.), SME Products LP
• Original Assignee: Ortloff Engineers, Ltd. (Honeywell International Inc.), SME Products LP
• Inventors: Hudson, Hank M., Wilkinson, John D., Lynch, Joe T., Miller, Scott A., Cuellar, Kyle T., Johnke, Andrew F., Lewis, W. Larry
• Primary Examiner(s): Nguyen, Tam M
• Application Number:
  US14/462,056
• Publication Number:
  US 20150073194A1
• Time in Patent Office: 988 Days
• Field of Search: None
• CPC Class Codes: C07C 7/04 by distillation
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 2200/02 in a single 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 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/80 using integrated mass and heat exchange, i.e. non-adiabatic rectification in a reflux exchanger or dephlegmator
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2210/06 Splitting of the feed stream, e.g. for treating or cooling in different ways
• CPC Class Codes: F25J 2215/04 Recovery of liquid products
• CPC Class Codes: F25J 2215/60 Methane
• CPC Class Codes: F25J 2230/20 Integrated compressor and process expander; Gear box arrangement; Multiple compressors on a common shaft
• CPC Class Codes: F25J 2230/60 the fluid being hydrocarbons or a mixture of hydrocarbons
• 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 2240/40 Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
• CPC Class Codes: F25J 2270/90 External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
• CPC Class Codes: F25J 2290/12 Particular process parameters like pressure, temperature, ratios
• 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 2290/80 Retrofitting, revamping or debottlenecking of existing plant
• CPC Class Codes: F25J 3/0209 Natural gas or substitute natural gas
• 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 3/0242 : separation of CnHm with 3 carbon atoms or more

Abstract

A process and an apparatus are disclosed for a compact processing assembly to improve the recovery of C₂ (or C₃) and heavier hydrocarbon components from a hydrocarbon gas stream. The preferred method of separating a hydrocarbon gas stream generally includes producing at least a substantially condensed first stream and a cooled second stream, expanding both streams to lower pressure, and supplying the streams to a fractionation tower. In the process and apparatus disclosed, the expanded first stream is heated to form a vapor fraction and a liquid fraction. The vapor fraction is combined with the tower overhead vapor, directed to a heat and mass transfer means inside a processing assembly, and cooled and partially condensed by the expanded first stream to form a residual vapor stream and a condensed stream. The condensed stream is combined with the liquid fraction and supplied to the tower at its top feed point.

Claims

1. In a process for the separation of a gas stream containing methane, C₂ components, C₃ components, and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing a major portion of said C₂ components, C₃ components, and heavier hydrocarbon components or said C₃ components and heavier hydrocarbon components, in which process

(a) said gas stream is treated in one or more heat exchange steps and at least one division step to produce at least a first stream that has been cooled under pressure to condense substantially all of it, and at least a second stream that has been cooled under pressure;

(b) said substantially condensed first stream is expanded to a lower pressure whereby it is further cooled, and thereafter supplied at a top feed position on a distillation column that produces at least an overhead vapor stream and a bottom liquid stream;

(c) said cooled second stream is expanded to said lower pressure, and thereafter supplied to said distillation column at a mid-column feed position; and

(d) at least said expanded further cooled first stream and said expanded second stream are fractionated in said distillation column at said lower pressure whereby the components of said relatively less volatile fraction are recovered in said bottom liquid stream and said volatile residue gas fraction is discharged as said overhead vapor stream;

the improvement wherein

(1) said expanded further cooled first stream is heated in a heat and mass transfer means housed in a processing assembly and thereafter discharged as a vapor fraction and a liquid fraction;

(2) said overhead vapor stream is combined with said vapor fraction to form a combined vapor stream;

(3) said combined vapor stream is cooled in said heat and mass transfer means, thereby to supply at least a portion of the heating of step (1) while simultaneously condensing the less volatile components from said combined vapor stream, thereby forming a condensed stream and a residual vapor stream, and thereafter discharging said residual vapor stream from said processing assembly as said volatile residue gas fraction;

(4) said condensed stream is combined with said liquid fraction to form a combined liquid stream;

(5) said combined liquid stream is supplied to said top feed position of said distillation column; and

(6) the quantity and temperature of said combined liquid stream to said distillation column are effective to maintain the overhead temperature of said distillation column at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered in said bottom liquid stream.

2. The process according to claim 1 wherein said combined liquid stream is supplied to said top feed position of said distillation column using a pumping means.

3. The process according to claim 2 wherein said pumping means is housed in said processing assembly.

4. The process according to claim 1, 2, or 3 wherein

(1) said gas stream is cooled under pressure in said one or more heat exchange steps sufficiently to partially condense it;

(2) said partially condensed gas stream is separated thereby to provide a vapor stream and at least one liquid stream;

(3) said vapor stream is divided in said at least one division step to produce at least a first vapor stream and a second vapor stream;

(4) said first vapor stream is cooled under pressure in said one or more heat exchange steps to condense substantially all of it and thereby form said substantially condensed first stream;

(5) said second vapor stream is expanded to said lower pressure, thereby forming said expanded second stream;

(6) at least a portion of said at least one liquid stream is expanded to said lower pressure, whereupon said expanded liquid stream is supplied to said distillation column at a lower mid-column feed position below said mid-column feed position; and

(7) at least said expanded further cooled first stream, said expanded second stream, and said expanded liquid stream are fractionated in said distillation column at said lower pressure whereby the components of said relatively less volatile fraction are recovered in said bottom liquid stream.

5. The process according to claim 4 wherein

(1) said first vapor stream is combined with at least a portion of said at least one liquid stream to form a combined stream, whereupon said combined stream is cooled under pressure in said one or more heat exchange steps to condense substantially all of it and is thereafter expanded to said lower pressure whereby it is further cooled;

(2) said expanded cooled combined stream is heated in said heat and mass transfer means and thereafter discharged as said vapor fraction and said liquid fraction; and

(3) any remaining portion of said at least one liquid stream is expanded to said lower pressure, whereupon said expanded liquid stream is supplied to said distillation column at said lower mid-column feed position.