10 replies to this topic

[process_persia]

Dear All,

We use propane (97 wt%) as the feed of our plant. Propane is supplied from Outside battery limit, stored in high pressure spherical storage tanks and then pumped to the plant. The owner has decided to install a propane desulphurization package (with adsorption mechanism)propane line. I should perform a study about the location of this package.

My question is: should this package be placed before the storage tanks or before entering the main plant? Personally, I think the answer to this question relies only on cases of emergency shutdown. In another word, we should investigate which scheme would have the lowest impact on our plant and its feed if we have an emergency shutdown event. I would be thankful to hear your feedbacks on this issue.

[Zauberberg]

I wouldn't say the decision will depend on ESD issues, but rather on unit availability aspects. Having the treater section upstream of product storage tank increases the overall availability of the plant since there is a surge volume of desulfurized propane available for downstream processing, regardless of possible trips/shutdowns of Adsorber section.

[process_persia]

Dear Zauberberg,

Thank you so much. Actually, I am sorry I forgot to add something maybe important to the description:

The desulphurization package outlet sulphur content is zero. However, we need a minimum sulphur content in propane for some reasons. Therefore, the desulphurization system is using a bypass system in a way that a three-way valve is located upstream of the package and the outlet of package is analyzed for sulphur. the sulphur content of the package outlet, is adjusted by the bypass flowrate to maintain a predetermined amount of sulphur entering the plant.

Now my question is that: would this bypass system affect the location of our package (downstream or upstream)?

[Zauberberg]

As long as there is an option for continuous and controlled supply of untreated Propane upstream of storage tank/Adsorber unit, having the treaters upstream of Propane storage seems to be a better option to me. You can always allow some bypassing of the Adsorber/Tank into the process. The trade-off in this scheme is that you don't have any quality control of the incoming C3 upstream of plant battery limit. Can you afford that?

If the only controlled source of Propane is from your storage tank, then you don't have any choice but to install Adsorber unit downstream of storage tank.

[Art Montemayor]

Dear All,

We use propane (97 wt%) as the feed of our plant. Propane is supplied from Outside battery limit, stored in high pressure spherical storage tanks and then pumped to the plant. The owner has decided to install a propane desulphurization package (with adsorption mechanism)propane line. I should perform a study about the location of this package.

My question is: should this package be placed before the storage tanks or before entering the main plant? Personally, I think the answer to this question relies only on cases of emergency shutdown. In another word, we should investigate which scheme would have the lowest impact on our plant and its feed if we have an emergency shutdown event. I would be thankful to hear your feedbacks on this issue.

Process Persia:

Please stop making multiple posts of the same identical topic in different Forums. I have stated numerous times that it is against Forum policy to do so and it gains you no added value to your posting. It only causes confusion and the inability to organize and handle the responses - if any.

I have deleted your other posting. PLEASE STOP THIS PRACTICE. I am getting tired of deleting multiple postings because I don't know which one has priority and where they are located.

[process_persia]

Dear Art,

With all respect, I should say that It was not my fault. Honestly, sometimes when I post the topic, I recieve an error from the website, then I try to post the topic again. but after a while I see two posts with the same topic. Believe me that it was not intentional. I will always do my best to follow the rules and regilations.

Sorry again

[process_persia]

Dear Zauberberg,

I am attaching a sketch of the options we discussed. now lets imagine these cases:

1) Sulphur removal package upstream of tanks: the tank is initially filling with on-spec propane, then something causes the sulphur removal package to shut down for a while. during this time, propane with high sulphur content will be added to the tank. however, due to the large volume of the tank, this flowrate will not affect the sulphur content of the tank outlet flow.

2)Sulphur removal package downstream of tanks: in this case, the tank is always full of propane with high sulphur content. if anything causes the sulphur package to shutdown, we will have a flow of high sulphur content to our plant until this package is back into the service.

This suggests that case 1 is better from the ESD point of view. Am I right?

Attached Files

•  Arrangement.xlsx   133.97KB   23 downloads

[Zauberberg]

Can you control both the inflow and the quality of Propane at the battery limit in case (1), or you have to take whatever comes in? You haven't answered that question.

Option (1) certainly looks better from availability point of view, but if there are any constraints regarding incoming Propane quality or flow control upstream of Adsorber unit, you have to address those issues first. What are the feed specifications for downstream processing plant?

Await your reply.

[process_persia]

Dear Zauberbeg,

I checked the PIDs and there was only a flow control valve at battery limit and no analyzer. So we have only control on the flowrate.

The feed contains 80 ppm wt sulphur at battery limit and after the desulphurization package it should reach 35 ppm wt.

Best

Edited by process_persia, 09 August 2010 - 12:06 AM.

[Zauberberg]

If you can control the flow to the Desulfurization package, and you don't expect significant fluctuations in Propane quality, the tank can be installed downstream of the package. I would also consider a recycle line/pump from storage tank to the Desulfurization unit, in case you have - for some reason - an off-spec product in the tank unsuitable for downstream processing. A bypass line around the Treater unit is also helpful in case you make a Sulfur-free product (or well below 35ppm) so that you can blend it with untreated feed before you route it to the downstream unit. This option will minimize quality giveaway, and certainly increase your margin.

This option will not work in the case you have to receive larger quantities of untreated Propane than your Adsorber Unit can handle, or if the Sulfur content of incoming Propane cannot be removed by the Adsorber unit down to the required levels. As said, recycle line from the tank to the Adsorber would help in such scenario, but you have to evaluate all possible options before making the final decision. There are always trade-offs whichever design you choose for your plant.

Best regards,

[process_persia]

Zauberberg,

Many thanks for your instructive reply. I'll try to study the existing trade-offs and make a suitable choice based on our discussions.

Thanks again