One of the biggest challenges in operating a glycol gas dehydration system is addressing glycol loss. Most dehydration units are designed with a margin of 0.1 gallons of glycol per million feet of natural gas treated. If the system loses more than this it affects processes.
One of the most common ways glycol is lost is through foaming.
What is Glycol Foaming?
Glycol foaming happens when entrained hydrocarbons from production enter the glycol fluid.
As the entrained glycol processes through the contactor tower (or “absorber”) it will carry over the top of the tower with the sales gas when stable foam builds up on the trays.
Foaming also causes poor contact between the gas and the glycol, significantly reducing the drying of the gas.
There are four primary elements that promote the unwanted foaming in glycol:
- Hydrocarbon liquids
- Field corrosion inhibitors
- Finely-divided suspended solids
Excessive turbulence and high liquid-to-vapor contacting velocities will also cause the glycol to foam. This condition can be caused by mechanical or chemical troubles. The best cure for foaming problems is proper care of the glycol, as we’ll see in the next section.
How To Address Glycol Loss Due to Glycol Foaming
To dehydrate natural gas properly, your system needs clean glycol that is free from hydrocarbons and any other impurities. If you encounter foaming, your first step is to lower pressure and use an anti-foaming agent. This temporarily reduces the foam and continue processing gas.
However, this is a temporary fix.
To address the underlying issue, the best solution is to examine your filtration system and consider adding a carbon filter. Carbon filters are designed to remove dissolved impurities from the glycol solution.
If you have added a carbon filter and are still experiencing foaming and/or glycol loss, here are three other things to check:
- Temperature. Excessive temperatures can lead to a loss of glycol in the glycol reboilers. Temperatures above 400 F cause the vaporization and/or thermal decomposition of glycol. In particular, excessive top temperatures in the still column of the reboiler can allow vaporized glycol to escape from the to atmosphere with the water vapor.
- Turbulence. Excessive turbulence and high liquid-to-vapor contacting velocities can also cause the glycol to foam. This condition may point to underlying mechanical or chemical issues.
- Contaminants. Other causes of foam that may be present in the process fluid include field corrosion inhibitors, salt, or finely-divided suspended solids.
To speak with an expert about glycol dehydration, contact your local Kimray store or authorized distributor.