"Despite our stable operation and improvement efforts, the facility has continuously suffered from a decline in competitiveness," SKGC said.
The decision was made before the coronavirus outbreak and the recent collapse in energy futures, a market participant close to the company said.
The naphtha-fed cracker can produce 190,000 t/yr of ethylene, which is currently being used for downstream production at polyethylene (PE) units at the same location.
SKGC produces a total of 430,000 t/yr of linear low-density/high-density PE (LLDPE-HDPE) from two lines in Ulsan, as well as another 190,000 t/yr of HDPE from the same location.
It also operates a second, larger cracker at Ulsan that produces 680,000 t/yr of ethylene. This cracker will continue to operate at stable rates.
South Korea has focused on petrochemical investments to support its export-reliant economy in recent years.
Fellow Korean producer S-Oil last year completed a residue-upgrading and olefin-downstream complex, and plans to build a steam cracker and olefins facility by 2022.
Hyundai Chemical is also scheduled to increase its polymer capacity by 1.15mn t/yr by 2022.
By Mahua Chakravarty, Muhamad Fadhil and Suzi Shin