Three process requirements must be met for gas to be dried in a standard glycol dehydration unit: 1. The gas velocity through the contactor tower must not be great enough to entrain glycol into the dried gas. Theoretically, the entrainment of glycol does not interfere with drying. In practice, the continuous loss of glycol will… Read More »
Drying towers in natural gas service can become rapidly fouled with drilling mud or formation and frac sand. The sand appears in the wellhead gas when the rate of gas production becomes excessive, and the sand is thus sucked out of the formation and into the well’s tubing. Drilling mud is found in natural gas… Read More »
A distillation column can flood due to dry damage, undersized liquid downcomers, high liquid level in the bottom of the tower, foulcommonly encountered in natural gas conditioning. The troubleshooter should first check for flooding due to excessive vapor velocities. The following correlation may be used for trayed columns 2 feet or more in diameter with… Read More »
The field supervisor’s first indication of a flooded contactor tower is usually a report of excessive glycol loss. A check of a lowpoint bleeder on the gas pipeline downstream of the tower will show glycol. After refilling the glycol reboiler, the level in the reboiler gauge glass noticeably decreases after a few hours. This is… Read More »
The hot glycol from the reboiler is cooled by heat exchange with the wet glycol from the contactor. This heat transfer typically takes place in a double-pipe or plate-type exchanger. On one of the double-pipe heat exchangers, I noticed that the reboiled glycol was being cooled to a rather low temperature. I suspected that this… Read More »
The gas exiting the top of the contactor in Figure 6-1 can be assumed to be in equilibrium with the reboiled—i.e., dry—glycol. The higher the glycol reboiler temperature, the dryer the glycol. The dryer the glycol, the dryer the treated natural gas. For most of the year in El Gringo, critical control of the glycol… Read More »
The first oddity I noticed was the noise from the vents associated with the individual reboilers. As Figure 6-1 shows, the expanding gas, used to drive the glycol pumps is also used as fuel to reboil the glycol. The excess gas not burned in the reboiler is vented under pressure control to the atmosphere. When… Read More »
Natural gas transported through common carrier pipelines must meet a moisture specification of 7 pounds of water per MMscf. Gas is usually dried to meet this requirement by scrubbing with a concentrated glycol solution. Figure 6-1 shows a standard glycol contactor tower, regenerator, and pump. Gas flows into the bottom of this tower where entrained… Read More »