joule thomson effect

[msalajeel]

How can we prevent joule Thomson effect on valves (natural gas plant)? and how should we deal with this effect in case it happen to a valve (pressure drop)? is there any procedure regard this matter?
best,

 

[MortenA]

No of course not - its fundamental thermodynamics! But you could of course heat the gas before or after the valve.

 

[msalajeel]

MortenA, thanks for posting your answer.
yes indeed its thermodynamics! but my question is How we can prevent it! because 4 years a go i was in gas plant and this "pressure drop" happened and it caused a problem to the facility operators! so after they studied the case its shows that its JT effect. and im wondering if there any way to prevent it or if there is any procedure in case it already happen?
thx

 

[zdas04]

You cannot prevent it, just like you can't prevent steam formation or freezing.

People have minimized its effects by taking big pressure drops in a number of smaller step and providing enough pipe between steps to pick up some heat from the atmosphere. This is really expensive and takes a lot of steps. I saw one plant where they took the pressure drop into a hearter/treater, but that must have been very expensive as well because that was the only time I ever saw that technique used.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[davefitz]

I think you need to deal with the problems caused by JT , and as indicated earlier in cannot be prevented.

If the valve is a single stage pressure reducing valve, then there will be an extreme JT effect at the "vena contracta" and this may cause condensation of liquids ( or even solids in the case of some gases ,such as CO2) , and the later flashing of these liquids downstream of the vena contracta can cause erosion/ corrosion . This particular problem might be addressed by using a multistage valve, such as a CCI self-drag valve.

If condensation will occur nonetheless, then you would need to add drain pots or separators to remove the liquids that are condensed- similar issues happen in natural gas pipelines as the product is delivered to the comsumer's lower pressure gate.

And finally, you can in theory get power out of the pressure reducing station if the valve is replaced with a turbine, but the JT effect would then be greatly magnified. The power turbine can be synched to the grid using modern solid state electronics, as used at Capstone micro-turbines or at wind turbines.

"Whom the gods would destroy, they first make mad "

 

[zdas04]

Another tool that works well is to use ejectors instead of chokes. In either case (turbines or ejectors) you have to have a fluid stream to work on, but often that just takes a bit of creativity.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat