Wet gas enters the glycol contact tower through an inlet which located in base and flows upwards through the bubble caps. Dry glycol will flow across the tray from top of the tower; the number of trays which typically installed in a glycol contact tower is six to eight trays. Before it went to the contactor, the dry glycol is cooled by gas from the outlet to condensate its water vapor and any other liquid. To maximize the gas contact area with glycol it must form bubbles on its way up. This is what bubble cap is about, it make sure that the gas is dispersed into small bubbles.
So the gas went up the glycol went down and they met and make contact on their way. The wet glycol – yes, it’s wet because glycol will absorb the gas water vapor during their contact – will leaves the tower from the base and flow to reboiler or reconcentrator through heat exchanger, gas separator and filter. So what’s happened in the reboiler? Glycol is heated so its water content could form steam. After the water vapor is removed from glycol then we have a dry glycol again and it’s ready to pumped back to the contact tower. Most glycol contact tower dehydrator use triethylene glycol, it’s expensive but it can handle hotter gas with minimal losses.