21 replies to this topic

[pandarobot]

Hi,

how do i go about the selection and sizing a storage vessel for ethylene gas? the gas is to be stored as compressed gas and i was wondering if there were guidelines to doing this.

Edited by pandarobot, 13 April 2015 - 10:23 AM.

[Art Montemayor]

By "design", I have to presume you mean the mechanical design, not the process design, since the latter is quite a simple calculation.

 

The basic and fundamental engineering "guidelines" to follow in this application would be such pressure vessel codes as ASME (American Society of Mechanical Engineers) Section VIII for unfired pressure vessels.

 

Additionally, you should apply all the legal and mandatory features dictated by your local authorities governing safety and industrial installations.

[pandarobot]

Hi,

 

i actually mean the process design, i am also reading that it is more sensible to store it as a liquid instead, if you could provide any help on this it would be appreciated, thank you.

Edited by Art Montemayor, 13 April 2015 - 01:41 PM.

[Bobby Strain]

You must supply more information. How much storage? Where is it located? Is refrigeration, like propane, available?
What pressure?
Delivery from storage requirements?

Bobby

[pandarobot]

• the gas will be leaving the storage and going to a compressor and heat exchanger at around 1000kg/hr.
• storage of 4 weeks is needed.
• process water, steam, cooling water, electricity and compressed and instrument air are available on site.
• as it is withdrawn, it will be compressed/heated up to 80bar and 25C, so it will need to be stored at a lower pressure than 25 bar.
• i guess i'm trying to calculate/design volume needed.

Edited by Art Montemayor, 13 April 2015 - 01:42 PM.

[Art Montemayor]

Please pay careful attention to what Bobby Strain states and USE COMMON SENSE.  What he is asking is what will confront you in the real world should you graduate as an engineer.  For example:

 

There are 24 x 7 = 168 hours/week
There are 168 x 4 = 672 hours in four weeks.

 

This means you are proposing to store 672 tons of gas (as gas?) in a single vessel.  Without going into any level of calculations and just using common sense should tell you that this is going to be a HUMONGOUS vessel.  You fail to tell us the name or composition of the gas.  You MUST identify it and give its density at the storage condition in order to begin to make the basic calculation.  This should tell you the “size” of the proposed vessel.  However, I (and I’m sure Bobby will agree) strongly feel the required vessel (if one is indeed required) should store a liquefied product rather than a gaseous one.  Of course, since we don’t know ALL of the story, I could be wrong.

[pandarobot]

Hi Art,

thank you for your reply

the gas is ethylene, density is 1.15kg/m3, i also meant 1055kmol/hr of the gas. if it will end up as a really big vessel, could i store it in more than one (but smaller in size) containers.

[Bobby Strain]

This is 30 tons per hour. So you will need to have an atmospheric pressure storage tank. Which requires that you liquify the ethylene and cool it to storage temperature at atmospheric pressure. It's a special, double-wall tank. And you will need pumps and vaporizer to deliver gaseous ethylene from storage to your compressor.

 

Bobby

[pandarobot]

Hi Bobby,

Thank you. 

how would i go about sizing this tank, from a bit of reading, i realise i can store this in a Horton Sphere? and it will be double walled because that is the type used for temperatures colder than -33C. by vaporiser, you mean heat exchanger?, could i possibly heat the liquid back up to a gas using a shell and tube heat exchanger?

[Bobby Strain]

You need to do a Google search about ethylene storage.

Bobby

[breizh]

Hi ,
Use the search tool in this forum and you should get useful info , next to FAQ.

Good luck

Breizh

[farid.k]

Yes, I do agreed with art.

 

For tank sizing (any tank), the demand from user, future forecast, margin, logistic, operating philosophy must be really need to be carefully determined and agreed with the team member. After agreed with the team member, then we can come out the proposed size of the tank that can supply to the xx demand on xx storage time and can also cater for the xx year forecast. Daily logistic send and received also need to be incorporated in the design (if any). We cannot just simply assumed to store 4 week. There are a lot more parameter need to be considered. All this things need to be documented as basis of design for the storage.

[curious_cat]

 

 

Where does gas come to storage from? Just curious since you mention 4 weeks of storage. 

[pandarobot]

Hi,

from a near by plant. this is actually for my final year project. so it's not an actual plant, but we are to have 4 weeks worth of storage in our own plant too.-

[curious_cat]

 

Someone with more experience on the forum might be able to help you but 4 weeks of storage seems a lot for ethylene coming by pipeline (presumably) from a plant next door.

 

I could be wrong. 

[farid.k]

Regardless for your final year project or actual plant, that info is important. I also chemical engineer student before and have to involve plant design.we must have detail basis before proceed to the Desig.

[breizh]

Hi ,
The reason for the storage in house may be linked to the difficulty of supply in particular during periodic shut down of the supplier (maintenance,....) .

The OP should clearly state the reasons.

Breizh

[pandarobot]

yes that is the reason there is extra storage in the plant.

[curious_cat]

 

@OP:

 

What is the product that you are manufacturing? Does the revenue of 4 weeks of production make it worthwhile to provide the investment needed for 700 tons of ethylene storage?  What is the estimated Capex? 

[pandarobot]

Hi Curiouscat,

the product is ethylene, i just have to size the tank that will store 4 weeks worth of storage, the capex is not important, it's more important that i size the tank.

[pandarobot]

Hi,

i believe i might have found out why the answers above were alarmed at storing the gas for 4 weeks. i found the liquid density of ethylene calculated at 1 bar at its boiling point 282.4K, (which would be the temperature and pressure i'm using to store it as a cryogenic liquid), which was 567.65kg/m3, if i was trying to store 4 weeks worth of ethylene for the theoretical plant, i would need a 35,000 m3 tank?

Edited by pandarobot, 15 April 2015 - 03:44 PM.

[Bobby Strain]

It's simple arithmetic, right. By the way, these new LNG boats can haul as much as 266,00 cubic meters of LNG. Ethylene boats are being built to haul about the volume you estimate for your tank.

 

Bobby