4 replies to this topic

[winanto]

Dear All,

Many reference, design or textbook said that Boil-off gas rate of LNG tank shall be 0.05%/day.
Could you explain what is the background/consideration?
How was it selected as design basis? Is there any international agreement?

Thank you.

[Zauberberg]

Are you speaking about LNG carriers or LNG tanks in onshore plants? The principle of operation of both systems is quite a bit different - e.g. in carriers there is average heat gain that generates BOG and provides self-refrigeration of the system, whereas in LNG plants there are other factors that contribute to BOG generation: LNG production rate (tank inflow), last Methane flash stage pressure (= temperature of LNG going to the storage), ship cooldown/loading (tank outflow) etc.

[Zauberberg]

Here are some materials that may be of interest to you:

Attached Files

•  Cryogenic Refrigeration Cycle for LNG Reliquefaction.pdf   232.4KB   171 downloads
•  On Board Reliquefaction.pdf   446.5KB   146 downloads
•  LNG Tank.pdf   750.72KB   185 downloads

[winanto]

Are you speaking about LNG carriers or LNG tanks in onshore plants? The principle of operation of both systems is quite a bit different - e.g. in carriers there is average heat gain that generates BOG and provides self-refrigeration of the system, whereas in LNG plants there are other factors that contribute to BOG generation: LNG production rate (tank inflow), last Methane flash stage pressure (= temperature of LNG going to the storage), ship cooldown/loading (tank outflow) etc.

Dear,

I mean is the BOG rate based on heat leak to tank only, for on-shore LNG Tanks.
I read some references, that up to now the average generated BOG is around 0.05%. Is the limitation is material to build tank? Is is possible to select other material to reduce the heat leak?

[Zauberberg]

Tank heat gain is just one of the factors contributing to BOG generation. These include:

- LNG transfer/loading pump(s) heat gain
- LNG flash vapor
- Piping heat gain
- LNG vapor displacement (tank inflow)
- Ship vapor displacement (ship vapor return)
- Ship vapor return line heat gain, etc.

Below is attached the design document for one of LNG plants, showing BOG generation summary.

Attached Files

•  BOG Summary.pdf   7.2KB   187 downloads