gas dehydration design

[sah14002000]

Dear Sir;
I am involved in one project which includes one gas dehydration unit which use TEG(Triethylene Glycol) to dehydrate the gas .
In the process there is one circulation pump which shoud increase pressure of TEG(with purity of 99%) from 6 bara(and 37 C) to 118 bar.
The strange matter is that the temperature of TEG decrease in outlet of pump by 3 C.
the software which used for simulation is HYSYS and the equation of state is peng robinson.
the question is that in actual case and reality what happens for TEG. Does actualy TEG temperature decrease after pump?
I asked it from one who do the simulation and he confirmed that it happens in actual operation of plant,but i need some evidence.
can you help me?
Best Regards

 

[dcasto]

heat transfer to the air and temp transmitter can account for this.

 

[rneill]

If you want to confirm the temperature drop, use the same temperature gauge to measure both upstream and downstream otherwise calibration errors between the instruments could easily account for this difference.

 

[sah14002000]

dear frineds
thanks for your responses.
but i heard that TEG is especial liquid.
can anybody find T-P diagram for teg (99% purity+1%water).

 

[sshep]

It wasn't clear if your 3deg-C temp drop was a simulation result, or a plant observation. On re-read, it seems like you have an unusual simulation result supported by anecdotal plant observation (the worst kind of plant data).

A TEG system could have all sorts of simulation related phase change phenomon that might happen in a simulation with an unrepresentative property set choice: hydration, freezing, dissolved gas, two liquid phases, etc, but will not happen in the plant. As Peng-rob is limited in its ability to calculate any sort of phase changes (beyond VL I suspect) to account for a temperature drop, I hypothesize that your simulation result is giving a bit of vapor formation at the pump outlet. This is a calculational anomaly, and not a real phenomonen. Please go back to your simulation and check for vapor or for two liquid phases at the pump outlet.

Another note: The GPSA manual has a very practical section on dehydration.

best wishes,
sshep

 

[moltenmetal]

Raising any liquid from 6 bar to 118 bar takes a lot of mechanical power, using real pumps that have efficiencies that are not 100%. That wasted energy will end up heating, rather than cooling, this liquid.

 

[sah14002000]

thanks my friends.
it seems that this case is a limitation by hysys.
the person who do simulation in final stage use on dummy heater to compensate tempperature decrease in pump.