When extracted, natural gas typically contains large amounts of water. Natural gas dehydration removes ice-like hydrates that can grow as crystals, plugging lines and retarding the flow of gaseous hydrocarbon streams. Dehydration also reduces corrosion, eliminates foaming, and prevents problems with catalysts downstream.
Natural gas compressor stations typically contain some type of liquid separator to dehydrate the gas prior to compression. The most common dehydration method is the absorption of water vapor in a liquid desiccant. Liquid desiccants include diethylene glycol (DEG), triethylene glycol (TEG), and tetraethylene glycol (TETRA EG).
This blog post, part of the Magnetrol® series on natural gas processing applications, discusses how natural gas dehydration is typically accomplished and suggests level measurement solutions for this application.
Level Measurement Challenges and Considerations
Many facilities use a glycol skid for the dehydration process. Ethylene glycol flows downward from the top of a tower and meets a rising mixture of water vapor and hydrocarbon gases. Dry gas exits from the top of the tower while the glycol/water mixture is pumped out of the bottom. The glycol and water are separated, and the glycol is recycled. The withdrawal of the water-rich glycol from the bottom of the absorber is facilitated by a level control, and high and low level shutdown can be applied to the reboiler, surge tank and flash separator.
In addition, any water remaining in the natural gas can cause significant problems downstream, ranging from impurities to accidents and corrosion. Reliable level control throughout the process can ensure that the natural gas is properly dehydrated and no water remains.
Level Measurement Solutions
MAGNETROL has produced level measurement solutions for natural gas dehydration:
- For point level:
Tuffy® II float-actuated switch; Echotel® Model 961 ultrasonic switch; or Thermatel® TD1/TD2 thermal dispersion switch
- For continuous level:
Eclipse® Model 706 guided wave radar transmitter or Jupiter® JM4 magnetostrictive transmitter
- For visual indication:
Atlas or Aurora® magnetic level indicators
For more information on level measurement solutions for gas dehydration and other natural gas processing applications, download the natural gas processing brochures.