Why Some TEG Dehydration Units Fail to Perform
TEG dehydration is extremely popular to dehydrate natural gas at a reasonably high pressure. Normal natural gas moisture specification of 65 mg/Sm³ can easily be achieved through a TEG unit. Though the design of a TEG unit does not involve complex unit operations, large numbers of units fail to achieve the specifications. The purpose of this paper is to present the salient features that a designer should consider during the design of a TEG unit.
A typical TEG unit consists of coalescers, contactor, heat exchangers, reboiler, pump etc. Major problems a TEG unit face are underperformance of the contactor, blockage of packing, poor dehydration, low reboiler temperature, excessive glycol loss etc.
The inlet pressure and temperature are very important in the design of TEG unit, high pressure and low temperature improves the performance. Different types of internals are used for the contactor with structured packing the most common. It is preferable to avoid very dense structured packing to reduce fouling problems. High moisture content in the dehydrated gas is normally associated with poor contactor design and mal operation including poor regeneration of lean glycol, low glycol flow rate and high temperature of lean glycol returning to the contactor. Excessive glycol loss and poor regeneration of lean glycol generally caused due to poor design of the regeneration system particularly the design of reboiler and fire tube.