Modular plant and process for liquid/gas separation, in particular for liquid and gaseous phases of a crude oil

A unitary device for liquid/gas separation of respective liquid and gaseous phases of a fluid, wherein said unitary device for liquid/gas separation comprises a single enclosure comprising a leaktight wall that withstands pressure at the sea bottom and the internal pressure of said fluid, the leaktight wall being arranged about a vertical axis of revolution, and said enclosure containing:

• 1) a first internal pipe for delivering the multiphase fluid, the first internal pipe rising within said enclosure from a bottom end of said first internal pipe that includes or co-operates with a first orifice passing through a wall portion referred to as the end wall of the enclosure up to an open top end opening out into the top portion of the end wall of the enclosure, and continuing up to an open top end of said first internal pipe, and opening out into a top portion of the enclosure;
• and
• 2) a gas-discharge second internal pipe extending within said enclosure from an open top end to a bottom end of said second internal pipe that includes or co-operates with a second orifice passing through the end wall of the enclosure;
• and
• 3) a third orifice passing through said end wall of the enclosure coaxially around said first and second orifices in the end wall of the enclosure.