OPERATING TEMPERATURE

Operating Temperature Conditions for Effective Glycol Conditioning and Reduction of Glycol Losses

First we look at operating temperatures in the contactor, re-boiler and still overhead. Than we look at operating pressures in next post.

Contactor Operating Temperature
In the contactor the temperature of inlet gas and the glycol affect the amount of water removal from the saturated gas. Now if you recall that constant pressure of natural gas can be hold pure water as the temperature the gas increases and what is that mean, well its mean if we keep the inlet gas temperature low the unit will have less water content to remove from the gas. Now you also want to keep the lean glycol temperature down to minimum when entering the contactor but still 10oF-15oF (5oC-7oC) higher than the inlet gas temperature.
Why? For several reasons,

Advantages of Low Inlet Temperature
  • Warm glycol absorbs water more easily that hot glycol.
  • Cool inlet gas has less water in it.
  •  Hydrocarbons condensation is prevented.

Re-Boiler Operating Temperature
Now the re-boiler temperature is important because it controls the concentration of water and lean glycol.
At constant pressure higher re-boiler temperature results in greater glycol purity. The temperature for TEG should be set at 380oF to 400oF (193oC to 204oC).

Why?
Because we want the range higher than 212oF (100oC) temperature where water boils so that water can remove quickly but lower than the temperature of glycol dehydration because 404oF (207oC).

Still Column Operating Temperature
Remember what the still column does. It removes water from rich glycol and it recaptures glycol trying to leave with water vapor. The temperature range we want to set for the still over heat temperature is between where water boils and where glycol boils.
Still overhead temperature range between
Higher Than
Lower Than
212oF (100oC)
546oF (286oC)

It easy because water boils at 212oF and TEG boils at 546oF

Importance of Still Column Operating Temperature
The recommended ranges for the still overhead temperature is 212oF (100oC) to 215oF (102oC) at sea level.
  • Low still overhead temperature can cause boiler over load and excessive fuel combustion, 
  • High still overhead temperature can cause glycol losses, due to vaporization.

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