Natural gas is a source of energy that has been highly utilized for fuel especially cooking, heating and for electricity. In particular natural gas can be altered to various products such as fertilizer, methanol, and other useful products. According to the data of Ministry of Energy and Mineral Resources that the demand of natural gas in 2025 as big as 10.557 MMSCFD (Million Standard Cubic Feet per Day) is being increasingly in 2030 to become 11.144 MMSCFD. Nowaday Indonesia has been discovered new resource of natural gas with the estimated resource of natural gas in The East Natuna Block with the gas is 46 TCF (Trillion Cubic Feet). The East Natuna Gas Field faces some of the obstacle due to the CO2 content of the resource about 71 %. Therefore the key of utilizing natural gas in east natuna is choosing processing plant which can be purify raw natural gas effectively. There are certain processing of natural gas consist of Controlled Freeze Zone (CFZ), Pressure Swing Adsorption (PSA), and membrane technology.
Cryogenic distillation technology is the pravelent method for separating subtances through boilling point. This technology separating CO2 and H2S from natural gas will be concentrated on the bottom of distillation coloumn whereas the light component will be concentrated on the overhead of distillation coloumn but for the higly CO2 content about 71 % will be creating this subtance freezing. The technology for modify this problem is Controlled Freeze Zone (CFZ). This technology used single coloumn distillation for separating CH4 and other impurites such as CO2, H2S and H2O.
To distinguish among coventional cryogenic distillation and controlled freeze zone technology is to avoid freezing of the subtances by way of automation systems. Based on thermodynamic aspect, the equlibrium curve among temperatures toward compositions of CH4 and CO2 showed the equilibrium zone between solid and vapor phase at the same time the zone which is vapor-liquid are above and below the solidification zone of CO2. In the distillation coloumn divided to be three parts consist of stripping section, CFZ section and retifying section. The function of stripping section is separating product like CH4 from liquified CO2. CFZ section is the place for freezed and liquified of CO2 and then the function of retifying section is separating CO2 from the light component. The applicated of controlled freeze zone tchnology has been succsessfully in several place such as La Barge, USA and Clear Lake, Texas.
Subsequently, Pressure Swing Adsorption is advanced technology which applicated for separating gas using selective materials to adsorp specific gass. The process occur in pressure swing adsorption has two mechanisms involving high pressure and low pressure. When the high pressure operating, adsorbent will be bonding spesific gas in this surface while low pressure operation, adsorbent will be removing spesific gas. The famous selective materials that used for pressure swing adsorption such as zeolite, CMS and activated carbon.
The last technology for processing natural gas is using membrane technology. Membrane is thin layer that could be used for removal CO2 from natural gass based on permeability. The common materials which are used for membrane such as cellulose acetate, polyamide and polycarbonate. The principle of processing membrane fo removal CO2 is the difference of solubility and diffusion. Universal Oil Company barelly implemented membrane technology for Enhanced Oil Recovery (EOR). These systems were processed gasses inlet with capacity of plant around 120 MMSCFD with containing CO2 around 70 %. The products of hydrocabon that were resulted still containing CO2 as much as 5 %.
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