HYSYS Depressurization

[srihari5043]

I am in process of calculating depressurization rate for condensate dehydrator .
LPG condensate composition as follows :

Component Mole %
NITROGEN 0.0009
H2S 0.0009
CO2 0.0028
METHANE 0.0911
ETHANE 0.1548
PROPANE 0.3015
i-A-BUTANE 0.0805
n-A-BUTANE 0.2154
i-PENTANE 0.0503
n-PENTANE 0.0612
n-HEXANE 0.0307
n-HEPTANE 0.0089

I specified the following for the depressurization module in HYSYS:

Total System Volume 87.1 M3
Liquid Inventory 87.1 M3
Wetted Surface area 117.2 M2
Initial Pressure 58.6 BarG
Initial Temperature 37.8 Deg C
Orifice size 400 mm2
Flow equation supersonic
Valve type Liquid
Environmental Factor 1
Heat flux Model API521
PV Work Term Contribution = 93%
Coefficient of Discharge for Orifice = 0.84

Results of simulation showing out let temperature are in negative

Can any facing the same problem... please share your experience

please check the hysys simulation on the hyper link.

http://www.4shared.com/file/R8YyAOLTba/Condensate_dehydration.html

 

[chemebabak]

Depressurization within a vessel results in adiabatic cooling. Lowered temperature (even negative) is expected. At the outlet of a valve, the gas could either warm or cool, depending on the Joule-Thompson coefficient. These are both described in most textbooks about thermodynamics.

As a practical consideration, in real world applications the cooling could be so great that specialized metallurgy (low temperature carbon steel or stainless steel) would be required because of the possibility of metal embrittlement. This could be a significant cost impact to the project.