PENINGKATAN RECOVERY EMAS DI CARBON IN LEACH PLANT PT. ANTAM TBK UNIT BISNIS PERTAMBANGAN EMAS PONGKOR, JAWA BARAT (STUDI KASUS KADAR BIJIH 3,5 – 4,5 GPT DI PLANT 1)

Abstract

ABSTRAK

Sejarah pengolahan mineral emas di Unit Bisnis Pertambangan Emas (UBPE) Pongkor PT Antam Tbk menunjukkan adanya tren menurunnya kadar bijih. Meskipun demikian, metallugist di UBPE Pongkor PT Antam Tbk secara berkelanjutan mencari berbagai penyebab dan cara untuk meningkatkan nilai recovery Plant walaupun kadar bijih yang cenderung menurun. Berdasarkan hasil pengolahan data terhadap Plant 1 dan Plant 2 di UBPE Pongkor, menunjukkan adanya potensi perbaikan di area Plant 1 UBPE Pongkor PT Antam Tbk. Makalah ini akan berfokus pada pengurangan kadar emas dalam sand tailing saat kadar bijih antara 3,5 sampai 4,5 gram per ton (gpt) di Plant 1 dalam rentang 2 bulan. Berdasarkan hasil analisa data yang diperoleh dengan menggunakan metode Anova, diperoleh hasil bahwa fraksi halus, kadar sianida, dan waktu tinggal slurry adalah hal – hal yang paling berpengaruh dalam proses pengolahan emas di UBPE Pongkor. Serangkaian perbaikan dan inovasi dilakukan untuk menyelesaikan masalah ini, yaitu dengan cara memodifikasi distribusi ukuran grinding ball, mengatur waktu mixing dan injeksi sianida dalam tangki, serta mengatur waktu dan memonitoring waktu tinggal slurry di dalam tangki leaching dan CIL.

Berdasarkan hasil perbaikan dan inovasi yang dilakukan, terlihat bahwa nilai recovery plant meningkat dari sebelumnya 89,4% menjadi 92,7%. Hal ini diperoleh dari nilai perbandingan distribusi ukuran bola 1 : 2 untuk grinding ball 40-60 mm dan 60-80 mm. Sementara itu, penyesuaian terbaik kadar CN adalah 600 - 650 ppm ditambah dengan optimalisasi injeksi sianida menggunakan pompa dosing sehingga dapat mengurangi waktu mixing sianida yang 3x sehari menjadi 1x sehari dan menurunkan kadar CN dari 1,23 menjadi 1,13 kg NaCN/ton bijih. Berdasarkan hasil pengaturan mill feeder dan pompa slurry, waktu tinggal di tangki leaching dari 51 jam menjadi 60 jam.

Kata Kunci : Emas, recovery, fraksi halus, sianida, waktu tinggal slurry

ABSTRACT

History of mineral processing at Gold Business unit at PT Antam Tbk shows a consistent trend of decreasing grade due to intensive mining operations. Therefore, The Metallurgist  PT Antam Tbk Gold Business Unit is looking for roots caused and solutions to raise up plant recovery although the grade of gold declined. After deep data analyzing process at plant 1 & 2, it’s shown that plant 1 at Gold Business Unit PT Antam Tbk have a room for recovery improvement. This research focus on reducing sand tailing to improved gold recovery at feed grade between 3.5 and 4.5 ppm at plant 1. Deep analysis was applied to processing big data from the plant using ANOVA Methode, it’s shown that fine fraction, Cyanide and slurry residence time were the major factor of gold recovery. Series improvement were applied to solved this problem, such as modifying grinding ball particle size distribution, adjusting cyanide feeding on leaching thank based on feed grade, and monitoring slurry residence time.

It was observed that the plant plant 1 recovery was increasing from 89,4% to 92.7%. The best grinding ball particle size distribution was 1 : 2 for 50 & 80 mm grinding ball. While the best applied cyanide concentration was between 600 - 650 ppm with some modification to improve process control of cyanide feeding. It’s shown that cyanide mixing process was decreased from 3 times a day to only one a day and also the cyanide consumption was reduced from 1.23 to 1.13 kg/ton ore.  Some modification also carried out to increase slurry residence time. It’s proved that by applying the improvement it’s shown that the slurry residence time rose from 50 h to 61 h.

Keywords : gold, recovery, fine fraction, cyanide, residence time.