Natural gas from an underground reservoir is typically saturated with water vapor. Removal of this water vapor is required in the gas processing to avoid serious problems. This study investigated the technical and economic aspects of a triethylene glycol (TEG) regeneration unit in a domestic natural gas processing plant. This study aims to improve the performance of this dehydration unit to meet sales gas specifications while minimizing the Total Annual Cost (TAC). The important variables in this work are TEG circulation mass flow and rerouting the gas from TEG Flash Drum to TEG Regenerator as stripping gas. The flash gas, instead of discharged directly to the Flare system, is routed to the TEG Regenerator and serves as stripping gas agent to improve the TEG purity. The results revealed that utilizing flash gas as stripping gas has allowed lower TEG circulation mass flow rate and reduced the reboiler duty from 1.464 to 0.934 GJ/h (a 36.2% reduction). The TAC was reduced from $ 296 058/year to $ 236 890 /year (20.0% reduction). Through this work, a more economical design was obtained compared to the base case design. K E Y W O R D Sdehydration unit, total annual cost, triethylene glycol 1 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Common problem in natural gas purification is Hydrate Formation. Hydrate is a solid – ice – like crystals in which gas molecules are trapped in the structure of solid water and causing problems especially clogging in the pipe line. Hydrate Formation usually happens at Dew Point Control Unit (DPCU) where the temperature is lowered to separate natural gas with heavy fraction by using Joule – Thomson effect. This paper aims to predict the Hydrate Formation Temperature at certain pressure by using some of HFT calculation methods. Kartz, Towler, Bahadori, and New Correlation are used to predict the Hydrate Formation Temperature with the pressure range of 700 – 2200 kPa. The obtained temperatures forming the gas at pressure of 700 kPa using Kartz, Towler, New Correlation, and Bahadori Calculation respectively are 274.26 K, 274.92 K, 275.02 K, and 275.2 K with Dew T at pressure of 700 kPa is 279.06 K, that means the Dew Point temperature is higher than the HFT, while at pressure 2200 kPa the temperature of Hydrate Formation respectively are 283.15 K, 283.46 K, 283.54 K, and 283.7 K with Dew T at pressure of 2200 kPa is 299.75 K, that means the Dew Point temperature is higher than the HFT.

Natural gas is one of the most desired raw materials which can be used in petrochemical industries or as energy resource. Natural gas usually obtained from underground reservoirs and it must go through purification process so it can be utilized. All acid gas compounds such as H2S, CO2 and all liquids including H2O must be removed. Most industries use triethylene glycol (TEG) dehydration unit to absorb water from natural gas streams. Therefore, further research about design and optimization of dehydration unit using TEG should be conducted since the optimization of dehydration unit using TEG affects to safety, operability, and stability of the process. In this study, the optimization of TEG Dehydration Unit process is conducted to minimize the Total Annual Costs (TAC) and improve the efficiency of the process. Aspen Plus software is used to perform the simulation of TEG dehydration process. Optimization is conducted by changing several of the base case operating conditions which have been created using existing condition to obtain the optimum conditions with minimum TAC on the existing circumstances. The variables that are used in this research is absorber column pressure (35-45 barg with 2.5 barg interval) and lean TEG temperature (39-49°C with 2°C interval). The constrain of the absorber column pressure is less than 45 barg, since the natural gas feed pressure from well is 45.16 barg. The results show that by changing some operating conditions can reduce the size of the column, reduce the energy costs including steam, cooling water, and electricity costs. Therefore, it can reduce the TAC of the natural gas dehydration unit. The validation simulation results of the steady state of the TEG Dehydration Unit using Aspen Plus and the real plant produces relatively small % error, so it can be used to create a base case using the existing data. The mole fraction of H2O in dehydrated gas after optimization using Aspen Plus is 0.000178 while in real plant the result is 0.000200. The simulation results can reduce the TAC from 3, 416, 739 USD to 2, 973, 219 USD.