You Do Need power plug adapter while traveling from Ireland (Eire) to Lebanon.

Here is Why You Need An Adapter

The outlet and plug type used in Lebanon are C, D and G and in Ireland (Eire) is G. This is how they look like.

Ireland (Eire)

In Ireland (Eire), outlets of type G are in use.

Type G

Lebanon

In Lebanon, outlets of type C, D and G are in use.

Type C

Type D

Type G