Hydrocarbon dew point across joule thomson Valve and exchanger

[I2P]

I am working in a gas conditioning and processing plant,where we have a water dehydration system using TEG as solvent and a gas gas plate type Aluminium gas gas exchanger and Joule thomson valve for hydrocarbon dew point control.Our problem is that during daytime we are unable to maintain our Dew point across the JT valve and we have to operate the bypass valve.I feel the ambient conditons are having some effect on the gas gas exchanger,because in night hours the JT valve does not pinch to the extent that there is a large pressure drop.Can this problem be solved if this gas gas exchanger and the JT valve are provided with cold insulation.has anyone experienced such problems?

 

[TD2K]

Which bypass valve are you talking about? Is it the bypass valve for the JT valve?

A little more description how your system is arranged and controlled would help.

Is there any change in the inlet gas pressure/temperature coming in from the field to the TEG contactor during the day? That is going to have a significant effect on this system IF I understand overall what you are trying to do.

 

[I2P]

TD2K,thanks for replying.Yes the bypass valve which I am referring to is the bypass valve of the J-T control valve.To give u an idea of our flow chart,the gas from the separators is taken through the gas gas exchanger which is a plate type Aluminium exch.gas then goes to the TEG contactors,from where after water absorption,it is led back to the gas gas exchanger for further cooling.The gas from the gas gas exchanger passes thr, the JT valve and then through the low temp.separator.The temperature,and pressure at the inlet of the TEG contactors are fairly constant.
Any way would like to know how the temperature and pressure at the TEG contactor inlet will affect the performance of the gas gas exchanger and hence the dewpoint control.

 

[TD2K]

Something isn't right in your description. If your process is set up as you described it (gas from the separators going through the gas/gas exchanger, through the TEG contactors, through the gas/gas exchanger and then through the JT valve), the gas/gas exchanger would do nothing as the gas leaving the separators would be the essentially the same temperature as the gas leaving the TEG contactor that, per your description, goes back through the gas/gas exchanger.

Typically, I've seen the cold gas from the LT separator used to cool the feed gas to the JT valve after you've dehydrated it to avoid possible hydrate problems.

What is the specific process parameter(s) that are you controlling with the JT valve? If you have to open the bypass around the JT valve, that sounds like a capacity problem with the JT valve. Opening the bypass would have no effect on the dew point you'd be getting from the main JT valve. Both are isentalphic expansions, there would be no difference if the gas flowed through the JT valve or the bypass.

The TEG contactor only removes water vapor, it has no effect (or basically no effect) on the hydrocarbon dewpoint.