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Lpg Recovery Troubleshooting


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#1 Ahcingan

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Posted 30 January 2021 - 07:43 AM

Good morning,

 

I work in a gas treatment unit, we mainly recover DRY GAS and LPG and condensate. The Ortloff GPL (OHR) over head recycle recovery process is used, and 88% LPG is recovered. for a while now we have noticed a slight drop in the 85% GPl recovery which resulted in a loss of LPG in the dry GAS. How can I remedy this problem and regain the initial level of recovery which was 88% ???



#2 Pilesar

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Posted 30 January 2021 - 09:06 AM

Compare the current operation with the base case operation when performance was good. Account for the differences. Look particularly at equipment efficiencies for distillation and expander/compressor. Understand why there is a difference and what remedial steps make economic sense. Steady state simulation of the process by a chemical engineer might be useful in the analysis. If you are a chemical engineer, then this is a good opportunity. If you are not an engineer, it will be more difficult for you as the fundamentals of process operation are not necessarily intuitive.



#3 Ahcingan

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Posted 30 January 2021 - 09:36 AM

Thank you very much for your reply PILESAR.

curiously all the parameters of the LPG recovery unit are identical to those when we had a good recovery of the propane, the temperatures of the exchangers and the columns and the pressure profiles! we cannot understand why this sudden drop in LPG recovery efficiency



#4 latexman

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Posted 30 January 2021 - 10:27 AM

Are rates the same?



#5 Bobby Strain

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Posted 30 January 2021 - 07:21 PM

Your problem statement is too vague for anyone to give suggestions. Your column temperature profile must be different if you are experiencing lower propane recovery. And, as latexman suggests, you need a process simulator and a Chemical Engineer who knows how to use it. Or enlist the services of someone who has the tools and experience necessary.

 

Bobby



#6 breizh

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Posted 30 January 2021 - 08:49 PM

hi,

Your statement is puzzling me:

"curiously all the parameters of the LPG recovery unit are identical to those when we had a good recovery of the propane"

To get a meaningful answer you should submit detailed information with a comparison table "before and after " including balances , simulations ,....

People are willing to help but we need you to help us. 

Breizh 



#7 Ahcingan

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Posted 31 January 2021 - 06:20 PM

Thank you everyone for your responses.

Here I try to collect the maximum information concerning the changes of the parameters which can be the cause of this loss in recovery of LPG, I find that the reflux temperature of the absorbing has been increased by approximately 1,5°C (from -61.41°C to 60°C) ... this problem must come from the deethanizer head condenser.

I have consulted the documents published by Ortloff LTD, and I have found that the rate of recovery of propane is directly related to the rate of compression as indicated on the diagram that I will attach as an attachment.

I would like someone to explain to me what the ratio of propane recovery to the compression ratio means and what compression ratio do they talk about in their publication?

 

I would like to ask you kindly to explain to me how this process works which is OHR, from which party we will recover the maximum of propane?

 

DCS image : https://drive.google...iew?usp=sharing

(propane recovery ratio %) / (HP/MMSCF) : https://drive.google...iew?usp=sharing



#8 Bobby Strain

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Posted 31 January 2021 - 07:36 PM

Looks like I don't have access to your link. And, the higher reflux temperature indicates a greater propane content, perhaps. So, you should begin by evaluating the deethanizer operation. This is quite a complex system to troubleshoot. I suggest if you wish to improve the operation that you enlist the services of a professional. You will not resolve your issue without a process simulator and a Chemical engineer with gas plant experience.

 

Bobby


Edited by Bobby Strain, 31 January 2021 - 10:58 PM.


#9 ChEf

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Posted 01 February 2021 - 11:07 AM

If I understand well, your plant is based on an OHR Process where the ethane stream from a deC2 column is condensed and used to wash the the outlet of the expander in an absorber. Usually, the wash of cold natural gas with liquid ethane offers a good recovery of c3+ products.

 

I would suggest to control the composition, temperature and pressure at the deC2 overhead and more generally the dec2 column operation. Then a check on the ethane condenser should be performed and finally a look into the expander performance.

 

In addition you need to check the conditions at the flash vessel upstream the expander, because the bottom liquid from this vessel is fed to the deC2.

 

Regards



#10 Ahcingan

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Posted 01 February 2021 - 01:04 PM

Thank you very much for your clarification Mr Francesco.

 

We are more or less trying to implement your instructions that you quoted in your post. however I can not understand the report of the compression of the residual gas with the rate of recovery of propane !!

 

how does the increase in the compression ratio of the residual gas lead to an increase in the recovery of propane?

 

what is the link between these two parameters? I'm desperately trying to find out how I can't

 

try to explain this to me please

 

(propane recovery ratio %) / (HP/MMSCF) : https://postimg.cc/LYDY4KQG



#11 Bobby Strain

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Posted 01 February 2021 - 02:07 PM

Don't be concerned about that graph from Ortloff. Just turn the knobs you have. You must have operating instructions from Ortloff on controlling your process. If you don't, contact them. Where are you located?

 

Bobby



#12 breizh

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Posted 01 February 2021 - 09:31 PM

Hi,

https://www.yumpu.co...ocess-score-uop

 

You may be able to contact them , contact on the 2nd page of the doc (link above).

Good luck

Breizh






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