Triethylene Glycol (TEG) for Gas Dehydration

Natural gas from wells must be dehydrated prior to transfer or it can freeze and plug the pipeline. Triethylene Glycol (TEG) is used as a desiccant to remove the water at a dehydration plant.

In a simplified dehydration plant, wet gas enters a contact tower where lean liquid TEG is cascaded countercurrent to the gas, absorbing the water, and dry gas exits the tower. This now rich TEG flows through a reboiler where water is removed, and is then pumped back to the contact tower against natural gas line pressures

Pump requirements include high pressure (up to 1500 PSI / 102 bar), high temperature (up to 230ᵒF / 110ᵒC), low viscosity (3-8 cPs), handling abrasive particles and remote 24/7 operations. A particularly difficult challenge is thermal shock at startup, a common mode of failure for some pumps, whose internals may expand faster than the casing when hit with hot fluid. Positive displacement pumps are uniquely suited to handle the pressures, temperatures, viscosities, abrasives and duty cycle.

Viking in the Process

While natural gas-driven reciprocating positive displacement pumps were used for decades, they exhausted this potent greenhouse gas and their use is now discouraged or prohibited. Multiplex reciprocating pumps are also used, but suffer high maintenance as they are not usually considered a continuous duty pump.

Viking motor-driven rotary positive displacement TEG pumps handle all of the pressure, temperature, viscosity, abrasive and duty cycle challenges. Significantly, they have been designed and validated to withstand up to a 225⁰ thermal differential without contact, simplifying dehydrator startup routines that otherwise would require slowly warming the pump under low pressure through a bypass. These pumps are usually duplexed with one as a standby, periodically alternating operation, using explosion-proof drives.