Efficient Refrigeration for Olefin Plant Separation Stages
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Summary
Problems
The existing refrigeration cycle in olefin plants, which uses vaporized ethylene for low-temperature separation stages, increases capital costs and operational risks due to the compressor cycle required for ethylene refrigerant generation.
Innovation solutions
Using a portion of the liquid olefin fraction with two carbon atoms from the front end deethanizer as refrigerant, omitting the compressor cycle, and vaporizing it through heat exchangers to generate refrigeration power for the low-temperature separation stages, with the vaporized ethylene being recirculated to the raw gas compression stage.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If a compressor cycle is used to generate ethylene refrigerant for the low-temperature separation stage, then the refrigeration power is reliably provided, but the capital costs and device complexity increase significantly
Why choose this principle:
The patent extracts and eliminates the compressor cycle from the refrigeration system. Instead of using a complex compressor cycle to generate refrigerant, the invention directly uses the ethylene fraction from the front end deethanizer as refrigerant, removing the compressor, turbine, heat exchanger, separator, and outlet vessel from the refrigeration loop. This extraction of the unnecessary compressor cycle reduces device complexity while maintaining refrigeration functionality through direct expansion of the ethylene fraction.
Principle concept:
If a compressor cycle is used for ethylene refrigerant generation, then the refrigeration requirement is met, but the capital costs increase
Why choose this principle:
The ethylene fraction from the front end deethanizer serves itself as the refrigerant for the low-temperature separation stage. The system uses its own process stream (ethylene fraction) to provide the necessary refrigeration, eliminating the need for separate refrigerant generation equipment. This self-service approach reduces capital costs by avoiding the compressor cycle infrastructure while still meeting the refrigeration requirements of the separation stage.
Application Domain
Data Source
AI summary:
Using a portion of the liquid olefin fraction with two carbon atoms from the front end deethanizer as refrigerant, omitting the compressor cycle, and vaporizing it through heat exchangers to generate refrigeration power for the low-temperature separation stages, with the vaporized ethylene being recirculated to the raw gas compression stage.
Abstract
A method is described for refrigerant supply of a low-temperature separation stage in a plant for producing olefins from hydrocarbon-containing feed (olefin plant). During the separation sequence beginning with a front end deethanizer ( 3 ) downstream of raw gas compressor ( 1 ), precooler and dryer ( 2 ), first separation is performed into an olefin fraction having at most two carbon atoms and an olefin fraction having at least three carbon atoms. The fraction having at least three carbon atoms is conducted to the further separation sequence for longer-chain olefins ( 4 ). The fraction having at most two carbon atoms is conducted via a catalytic hydrogenation stage ( 5 ) connected in between to the low-temperature separation stage ( 6 ) which comprises three condensation stages in the temperature range from −50° C. to −100° C. From the low-temperature separation stage, gaseous hydrogen ( 9 ) and methane ( 10 ) are drawn off, while the olefins having at most two carbon atoms are conducted to a further fractionation stage ( 7 ). The refrigeration power for the low-temperature separation stage is provided by the vaporization via heat exchangers of a portion of the liquid ethylene fraction ( 8 ) resulting in the front end deethanizer. The vaporized ethylene fraction is recirculated to the raw gas compressor ( 11 ).