Technology Unit

Open Loop C₂ Fractionation System:

C₂ Splitter overhead product is heated then pressurized in the 3^rd stage of C₂ ref. compressor.
Further compression in the 4^th stage and the balance stream is cooled against the cold overhead vapours and condensed in the reboiler of the C₂ splitter:

• mainly subcooled and used as a reflux.
• others are condensed against propylene refrigerant and stored in Ethylene Collecting Drum.

Temperature levels of ethylene refrigerant:

• Low pressure (LP) C₂ refrigeration:  -101°C
• Medium pressure (MP) C₂ refrigeration:  -80°C
• High pressure (HP) C₂ refrigeration: -57°C

Propylene Refrigerant Cycle:

• Intermediate temperature range between cooling water and ethylene refrigerant.
• Temperature levels of propylene refrigerant :
  • Low pressure (LP) C₃ refrigeration: -38°C
  • Medium pressure (MP) C₂ refrigeration: -20°C
  • High pressure (HP) C₃ refrigeration: +10°C

Source: Y.A. Sastry & Uday Krishna Dy, DUAL FEED CRACKER UNIT & ASSOCIATED UNIT, ONGC Petro additions Limited (OPaL), Uploaded on 28^th Jan 2018 on SCRIBD.