Olefin plant refrigeration system
AssigneeABB Lummus Global Inc.
InventorsVitus Tuan Wei, Qi Ma, James Tzong-Chaur Wu, Charles Sumner
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Abstract
The refrigeration system for an ethylene plant comprises a closed loop tertiary refrigerant system containing methane, ethylene and propylene. The tertiary refrigerant from a compressor final discharge is separated 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 flowing back to the compressor and with the bulk of the total return refrigerant flow going to the first stage compressor section. This tertiary system can also be applied to an ethylene plant with a high pressure demethanizer.
Claims8
In a process for the production of olefins from a charge gas containing hydrogen, methane, ethylene and other C2 and heavier hydrocarbons wherein said charge gas and additional olefin plant process streams are cooled by a refrigeration system having a series of heat exchangers, a method for cooling said charge gas and additional olefin plant process streams by the use of a tertiary refrigerant in said refrigeration system comprising the steps of:
- (a) compressing a tertiary refrigerant vapor comprising a selected mixture of methane, ethylene and propylene in a multistage compressor having a first stage, at least one intermediate stage and a last stage with a last stage discharge wherein the composition of said last stage discharge is greater than 50 mol percent propylene;
- (b) cooling to condense a portion of said tertiary refrigerant vapor from said last stage discharge to form a remaining tertiary refrigerant vapor and a heavy liquid refrigerant having a greater percentage of propylene than said selected mixture;
- (c) separating said heavy liquid refrigerant from said remaining tertiary refrigerant vapor in a separator;
- (d) cooling to condense at least a portion of said remaining tertiary refrigerant vapor from said separator and thereby forming a medium liquid refrigerant and forming a light vapor refrigerant of any uncondensed portion thereof;
- (e) bringing said heavy and medium liquid refrigerants and any light vapor refrigerant into heat exchange contact with themselves and each other and with said charge gas and additional olefin plant process streams in said series of heat exchangers whereby said charge gas and additional olefin plant process streams are cooled and said heavy and medium liquid refrigerants are subcooled and then heated and vaporized and said light vapor refrigerant is first cooled and condensed and then vaporized;
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- (f) returning said light and medium and heavy vaporized refrigerants to said compressor.
Dependencies are inferred from the claim text.