Olefin plant refrigeration system

Details Olefin plant refrigeration system Olefin plant refrigeration system

2003-01-15

2004-03-16

Doerrler, William C. (Department: 3744)

Refrigeration

Cryogenic treatment of gas or gas mixture

Liquefaction

C062S620000, C062S913000

Reexamination Certificate

active

06705113

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention pertains to a refrigeration system to provide the cooling requirements of an olefin plant. More particularly, the invention is directed to the use of a tertiary or trinary refrigerant comprising a mixture of methane, ethylene and propylene for cooling in an ethylene plant.
Ethylene plants require refrigeration to separate out desired products from the cracking heater effluent. Typically, a propylene and an ethylene refrigerant are used. Often, particularly in systems using low pressure demethanizers where lower temperatures are required, a separate methane refrigeration system is also employed. Thus three separate refrigeration systems are required, cascading from lowest temperature to highest. Three compressor and driver systems complete with suction drums, separate exchangers, piping, etc. are required. An additional methane refrigeration compressor, either reciprocating or centrifugal, can partially offset the capital cost savings resulting from the use of low pressure demethanizers.
Mixed refrigerant systems have been well known in the industry for many decades. In these systems, multiple refrigerants are utilized in a single refrigeration system to provide refrigeration covering a wider range of temperatures, enabling one mixed refrigeration system to replace multiple pure component cascade refrigeration systems. These mixed refrigeration systems have found widespread use in base load liquid natural gas plants. The application of a binary mixed refrigeration system to ethylene plant design is disclosed in U.S. Pat. No. 5,979,177 in which the refrigerant is a mixture of methane and either ethylene or ethane. However, such a binary refrigeration system cascades against a separate propylene refrigeration system which provides the refrigeration in the temperature range of −40° C. and warmer. Therefore, two separate refrigeration systems are required.
SUMMARY OF THE INVENTION
It is an object of the present invention, therefore, to provide a simplified, single refrigeration system for an olefin plant, particularly an ethylene plant having a low pressure demethanizer, utilizing a mixture of methane, ethylene and propylene as a tertiary refrigerant. This tertiary system replaces the separate propylene, ethylene and methane refrigeration systems associated with a recovery process using a low pressure demethanizer. The invention involves the separation of the tertiary refrigerant from the discharge of the final stage of a compressor into a methane-rich vapor fraction and two levels of propylene-rich liquids so as to provide various temperatures and levels of refrigeration in various heat exchange stages while maintaining a nearly constant refrigerant composition, as measured by molecular weight, in the compressor and with the bulk of the total return refrigerant flow going to the first stage compressor suction. This enables the tertiary refrigerant system to compete favorably on a thermodynamic basis with the use of separate compressors for separate refrigerants. This tertiary system can also be applied to an ethylene plant with a high pressure demethanizer in which case the tertiary system only supplies propylene and ethylene refrigeration temperature levels. The objects, arrangement and advantages of the refrigeration system of the present invention will be apparent from the description which follows.
BRIEF DESCRIPTION OF THE DRAWING
The drawing is a schematic flow diagram of a portion of an ethylene plant illustrating one embodiment of the refrigeration system of the present invention.


REFERENCES:
patent: 3855810 (1974-12-01), Simon et al.
patent: 4094655 (1978-06-01), Krieger
patent: RE30085 (1979-08-01), Perret
patent: 4251247 (1981-02-01), Gauberthier et al.
patent: 5613373 (1997-03-01), Grenier
patent: 5979177 (1999-11-01), Sumner et al.
patent: 6334334 (2002-01-01), Stockmann et al.

Affiliated with

Also associated with

Rating

Olefin plant refrigeration system does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Olefin plant refrigeration system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Olefin plant refrigeration system will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3261256