7 replies to this topic

[NGL Licensor]

Good day all,

I am a Marine Engineer but am using the software Aspen HYSYS for my MSc. dissertation on 'Liquefaction systems for an Offshore LNG unit' at the Newcastle University, UK.

I am stuck at configuring the LNG Exchanger. I have tried to go through all the online tutorials as well as the help section in the software as well. But I just cannot seem to get it right due to a lack of experience with this software even after a lot of trial and error efforts with all the tabs in the LNG exchanger configuration window.

I would be very grateful if anyone could guide me with the same. I am attaching an image of the LNG exchanger that needs to be configured. Left hand side represents the interaction between streams and the right hand side the complete 'cold box'.

Queries:
1. What are zones and layers? Do I need to show 4 different exchangers or would that be 4 zones in one exchanger?

2. How to achieve Zero Degree of Freedom to correctly configure the exchanger?

3. I get 'Overspecified' as a message. Tried reducing the stream conditions but in vain.


Would anyone have a step by step guide to configuring an LNG exchanger? Alternatively I would not mind getting in touch over email or phone since as you can imagine I am in a pretty desperate situation with my dissertation.

Thanking you in anticipation. Would be glad to help out with any possible Marine Engineering related queries.

Kind Regards,

Shival Sapre

shival.sapre@ncl.ac.uk
+44 (0) 7503950872

Hi Shival,

The left side of the attachment represents a good presentation of the work.

The overspecified message is due to extra specs you have it on the model

If ok with you, please send me (ngltechnology@yahoo.com) the run and we can take it from their.

Regards,
A.King

[NGL Licensor]

Hello Mr. King,

Thank you for the reply. I had mailed you on your yahoo account. Was wondering if you received my mail?

Regards,
S.Sapre

Dear Shival,
Following are some points I changed in the simulation model:

All recycle streams have to be fitted with recycle unit operation to enable solution
Normally you do not specify a temperature spec on the compressor outlet.
You rather input a poly efficiency (e.g 75%)
Change all outlet temp spec of the respective water coolers to a DP instead
K102 is overspecified. I removed the temperature spec
Same for K101
If this all is done, the flowsheet will converge. However, unfortunately the cold box has a temp cross
The flow sheet is lacking the coolant to liquefy the LNG. You choose to use N2 only for liquefaction.
The cold box can now solve if:
N2 rate is around 720 MMSCFD
E1in Temp is –55 instead of –47F
E2in Temp is around –230 instead of –239F

I do not believe that this is a practical solution. N2 expander for LNG is some how new technology , as claimed by major players, however it should be coupled with others.

One question, what you shall do with liquid LNG product of this flow sheet!!!!!

Please feel free to any clarification. Please see atached PFD and MB Table

Regards,



A.King

Attached Files

•  LNG_Fourem.doc   45.5KB   306 downloads

[suresh2]

Shival,
I have modeled an LNG plant in HYSYS steady state and i have used the LNG Exchanger in HYSYS. Check your inbox for the HYSYS file. You can use this model as a reference for your work.

Some specification tips:
Compressor: specify the downstream pressure
Cooler: Specify the downstream temperature (DP = 5 psi)
Heater: Specify the downstream temperature (DP = 5 psi)
Heat Exchanger: Leave UA as default, specify LMTD or Min. Temperature Approach (if DOF is not zero then use both of them)

Best Regards,
Suresh

Good day all,

I am a Marine Engineer but am using the software Aspen HYSYS for my MSc. dissertation on 'Liquefaction systems for an Offshore LNG unit' at the Newcastle University, UK.

I am stuck at configuring the LNG Exchanger. I have tried to go through all the online tutorials as well as the help section in the software as well. But I just cannot seem to get it right due to a lack of experience with this software even after a lot of trial and error efforts with all the tabs in the LNG exchanger configuration window.

I would be very grateful if anyone could guide me with the same. I am attaching an image of the LNG exchanger that needs to be configured. Left hand side represents the interaction between streams and the right hand side the complete 'cold box'.

Queries:
1. What are zones and layers? Do I need to show 4 different exchangers or would that be 4 zones in one exchanger?

2. How to achieve Zero Degree of Freedom to correctly configure the exchanger?

3. I get 'Overspecified' as a message. Tried reducing the stream conditions but in vain.


Would anyone have a step by step guide to configuring an LNG exchanger? Alternatively I would not mind getting in touch over email or phone since as you can imagine I am in a pretty desperate situation with my dissertation.

Thanking you in anticipation. Would be glad to help out with any possible Marine Engineering related queries.

Kind Regards,

Shival Sapre

shival.sapre@ncl.ac.uk
+44 (0) 7503950872

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[Michael Zhang]

For the steady status model, it is easy to configure, because you can fill in the key parameters which are you concerned, to make the freedom become zero.
Herein, I just remind you the components chosen. if you LNG heat exchanger is MCHE exchanger, its cold stream should be mixture: like C1 36.5%,C2 59%, C3 3% and N2 1.5%; if it is SCHE exchanger, the cold stream will be pure N2.

In fact, the LNG exchanger is not perfect. the tube bundle model should be used for cooling down the LNG in real plant.

Edited by Michael Zhang, 09 March 2011 - 04:25 AM.