Studi Pengoperasian Regulator Penurun Tekanan untuk Menghindari Pembentukan Hidrat pada Proses Dekompresi CNG Menggunakan COMSOL dan Aspen HYSYS
Abstract
Abstrak. Compressed Natural Gas (CNG) diproduksi dengan cara memampatkan gas alam sampai tekanan 200 bar pada temperatur ambien lalu disimpan dalam tabung bertekanan tinggi. Dalam penggunaannya, CNG dialirkan pada regulator penurun tekanan untuk diturunkan tekanannya menjadi 3 bar melalui dua tahap penurunan. Penurunan tekanan tahap pertama adalah dari tekanan 200 bar menjadi 70 bar. Penurunan tekanan yang drastis menimbulkan potensi terbentuknya hidrat yang mengakibatkan penyumbatan aliran gas. Penelitian ini bertujuan untuk mencari solusi pencegahan terbentuknya hidrat melalui studi fenomena aliran pada regulator tahap pertama menggunakan perangkat lunak COMSOL dan studi kurva pembentukan hidrat dengan bantuan ASPEN HYSYS. Penelitian ini menunjukkan bahwa pada bukaan 25%, hidrat akan terbentuk pada daerah celah katup dan pada outlet regulator. Hidrat pada celah katup dapat tersapu oleh kecepatan gas yang mencapai 400 m/s sedangkan hidrat pada outlet regulator dapat menyebabkan sumbatan karena kecepatan gas hanya 0,05 m/s. Selain itu, bukaan katup 50% mampu mencegah pembentukan hidrat meskipun tekanan outlet mencapai 120 bar sedangkan tekanan outlet yang diinginkan hanya 70 bar. Kemudian, pemanasan gas inlet sebesar 25oC dapat mencegah pembentukan hidrat pada bukaan katup 25%. Lalu, injeksi metanol sebesar 2%-wt dari laju alir gas dapat menghilangkan potensi terbentuknya hidrat tanpa memanaskan umpan pada bukaan katup 25% karena injeksi metanol mampu menggeser kurva pembentukan hidrat ke area sebelah kiri.
Kata kunci: ASPEN HYSYS, CFD, gas alam, hidrat, regulator, simulasi.
Abstract. Simulation of Pressure Regulator to Avoid the Formation of Hydrates in Natural Gas Decompression. Compressed Natural Gas (CNG) is produced by compressing natural gas to a pressure of 200 bar at ambient temperature and then stored in high-pressure cylinders. In its use, CNG is flowed to the pressure reducing regulator to reduce the pressure to 3 bar through two stages. The pressure drop in the first stage is from 200 to 70 bar. A drastic pressure drop creates the potential for hydrate formation, which results in blockage of gas flow. This study aims to find solutions to prevent the hydrate formation through the study of phenomena in the first stage regulator using COMSOL software and the study of the hydrate formation curve with the help of ASPEN HYSYS. This research shows that at 25% opening, hydrate will form in the valve gap area and at the regulator's outlet. The hydrate at the gap can be swept away by the gas velocity reaching 400 m/s, while the hydrate at the regulator outlet can cause blockage because the gas velocity is only 0.05 m/s. In addition, the 50% valve opening can prevent hydrate formation even though the outlet pressure reaches 120 bar while the desired pressure is only 70 bar. Then, heating the inlet gas by 25oC can prevent the formation of hydrates at 25% valve opening. Furthermore, methanol injection at 2%-wt of gas flow rate can eliminate the potential for hydrate formation without heating the feed at 25% valve opening because methanol injection can shift the hydrate formation curve to the left area.
Keywords: ASPEN HYSYS, CFD, hydrate, natural gas, regulator, simulation.
Keywords
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