Process Design and Steady State Simulation of Natural Gas Dehydration Using Triethylene Glycol (TEG) to Obtain The Optimum Total Annual Costs (TAC)

Abstract

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.