Propane/Butane storage & export

[swtmoon]

During propane and butane storage and export facility design, I met some dimed points because of my lack of experience.
Please advise me about following questions;

In this plant we have two Propane storage tanks and two Butane storage tank.
Also 2.5 km away from the tank farm, there are two loading arms one for propane and the other for butane.
The loading operations will happen every 20 days.

1. To cooldown the loading lines, circulation with the product should be circulated continously? or circulated just few hours before a ship's arrival?

2. To condense the boil off gas in Butane storage tank, we plan to operate small capacity circulation pump and cooler. During loading the Butane product, what is better way between below two operation scheme?
- one is runing large capacity loading pump and circulation pump simulteneously
- the other one is increse loading pumps capacity and recycle the increased flow two cooler.

your kind advise will be highly appreciated.

 

[joerd]

1. If you'r talking atmospheric cryogenic storage and ships, you probably don't want to cool the loading lines all the time. This will cost you a lot of money! A short time before the ship arrives will do, but you will have to think about the big vapor volume that you will receive back initially when you put butane or propane through a line at ambient conditions.

2. Since you will have a circulation system in place why would you go through the trouble of switching it off during a loading operation? I would just keep it running and design the loading pumps to suit their duty.

Regards

 

[swtmoon]

Thank you for your kind advices.

But still I worry about this;

1. If pipe line cooldown performed intermittently, is there no thermal fatigue on pipe(LTCS) expected?

2. Currently circulation and loading header is common. If we operate loading and circulation pump by parallel, small capacity circulation pump may operated bellow it's rated capacity.

regards,

 

[joerd]

1. I don't think that 60 cycles per year will give problems, but you should check it with a mechanical / materials engineer.

2. I guess I didn't (and maybe still don't ) understand fully how your system is set up. If you have a circulation pump just to cool down the loading lines, then you stop it before loading starts and you can stop circulation altogether during the loading operation. You may need a vapor line to condense vapors coming off the ship (the ship usually has a vapor recovery system, but this may not be adequate to condense all the displaced vapors in the ships tanks).

regards

 

[hk59]

You could say that design pressure & temperature of line which used your system. Do you have recyle line from loading line to your storege system