SIMULATION OF GAS DEHYDRATION ON AN FPSO USING ASPEN HYSYS
Natural gas is an important energy source among other sources of fossil fuels. It is usually produced saturated with water vapor under production conditions. The dehydration of natural gas is very essential in the gas processing industry to remove water vapor. Water vapor in natural gas stream, poses threat to process facilities if the dew point temperature is not properly controlled. Dehydration of natural gas is the process removal of the water that is associated with natural gases. The mixtures of water in natural gas can cause the problems for the production operation, transportation, storage and use of the gas. The four major methods of dehydration are absorption, adsorption, gas permeation and refrigeration. The process of dehydration by using TEG is absorption, involves the use of a liquid desiccant to remove water content from the gas.
The objective of this experiment is to carry out a simulation on TEG dehydration unit using AspenHYSYS process software. This is important in an FPSO since the removal of water from natural gas is necessary before processing, and due to the fact that Natural gas from the reservoir contains large amount of water which can cause several problems to downstream processes and equipment. TEG was used because it has gained nearly universal acceptance as the most cost effective of the glycols due to its superior dew point depression, operating cost and operational reliability. The composition of the natural gas has been provided on a water-free basis, therefore to ensure water saturation it was mixed with water before entering the first unit operation. The units involved in this simulation are; Contractor, Regenerator, Valve, Component splitter, Cooler, Stripper and Splitter, alongside with an adjust logical tool which was used to find the point at which water is just formed (dew point with a temperature of -13.67Oc). At the end of the converged simulation, 89.92 wt% methane was recovered at a flow rate of 9177kg/hr. which might have resulted due to loss of some of the gases at certain stage of the process.