Proses pemisahan ethylene–ethane yang terjadi di ethylene fractionator merupakan salah satu proses penting di ethylene plant PT Chandra Asri petrochemical Tbk. Mengingat pentingnya fungsi dari ethylene fractionator yang menghasilkan ethylene sebagai salah satu produk utama dari PT Chandra Asri Petrochemical Tbk. maka dilakukan evaluasi kinerja terhadap ethylene fractionator sehingga dapat diketahui posisi pencapaian sasaran produksinya. Evaluasi dilakukan dengan cara menghitung efisiensi tray overall desain dan aktual dari ethylene fractionator. Data masukan merupakan data lapangan dari tanggal 5 Maret 2012 s/d 13 Maret 2012. Dilakukan pula penentuan nilai reflux ratio optimum menggunakan simulator agar dihasilkan ethylene dengan kemurnian tinggi dan mencapai sasaran yang diinginkan, yaitu 0,9996. Hasil perhitungan yang dilakukan menunjukkan bahwa nilai efisiensi tray overall desain adalah sebesar 52,09%, sedangkan nilai efisiensi tray overall rata-rata adalah sebesar 51,16%. Hal tersebut menunjukkan bahwa kinerja ethylene fractionator pada saat ini sudah cukup bagus. Rata-rata fraksi mol ethylene yang dihasilkan, yaitu 0,99976. Nilai tersebut melebihi sasaran produksi. Berdasarkan hasil simulasi, nilai reflux ratio optimum adalah 3,2. Terdapat beberapa faktor yang mempengaruhi tingkat kemurnian ethylene yang dihasilkan, yaitu nilai reflux ratio, pressure drop, dan fraksi mol ethylene yang diumpankan. Kata kunci : Ethylene Fractionator, ethylene , efisiensi tray, reflux ratio, pressure drop.

Ethylene–ethane separating process using ethylene fractionator is one of the main processes in Ethylene Plant PT Chandra Asri Petrochemical Tbk. Considering the importance of the function of ethylene fractionator in producing ethylene as one of main products of PT Chandra Asri Petrochemical Tbk. evaluation of ethylene fractionator performance was conduced to observe the position of production target achievement. Evaluation process was done by calculating overall tray efficiency design and actual of ethylene fractionator. Data were collected from March 5th, 2012 until March 13th, 2012. Optimum reflux ratio was also calculated by simulator to produce ethylene with high purity and reach the production target of 0.9996. As a result, the design overall tray efficiency of ethylene fractionator was 52.09%, while the average of actual overall tray efficiency was 51.16%. It shows that ethylene fractionator performance observed was quite good. Mole fraction average value of ethylene in distillate was 0.99976 which is higher than the production target. Based on the simulation, optimum reflux ratio was 3.2. From this observation it can be concluded that there are severals factors affecting purity of ethylene product, i.e. reflux ratio, pressure drop, and mole fraction of ethylene in feed. Keywords : Ethylene Fractionator, ethylene, tray efficiency, reflux ratio, pressure drop.

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