2 replies to this topic

[ist10]

Dear all,

We are designing a methanol unloading&storage terminal. At the current stage of the project, it is desired to check the applicability to purge the line to battery limit that is full of methanol using nitrogen. The project does not foresee a dedicated closed drain for the drainage of methanol. Therefore, it is assumed that it will be possible to empty the line via vacuum trucks.
Can anybody comment on this process, both on operation and safety side. Operation experiences on vacuum trucks are also appreciated. (Is a methanol vapor-air mixture possible inside the vacuum truck?)

Thanks in advance

[ankur2061]

ist10,

Yes, a methanol-air mixture vapor pocket in the vacuum truck is possible simply because the methanol-air mixture would be heavier than nitrogen. You would need to have an initial purging by nitogen gas to purge out the air through the vacuum truck before you start applying vacuum at the truck to suck out the liquid methanol from the line to the truck.

As far as safety part is concerned you need to know the concentration of the methanol-air mixture which is flammable based on the Lower Flammable Limit (LFL) and the Upper Flammable Limit (UFL). Any hydrcarbon-air mixture which is below the LFL is too lean to form a flammable mixture and any hydrocarbon-air mixture above the UFL is too rich to form a flammable mixture. A safety concern arises when the hydrocarbon-air mixture is between the LFL & the UFL and appropriate safety measures are required to prevent a fire / explosion.

Hope this helps.

Regards,
Ankur.

[ist10]

Thanks Ankur,

I was not pretty sure about whether air will be present or not during vacuum truck operation and this clears my doubts.
definitely helps