insulation 130 such that the temperature of the foam 118 does not drop the gas continues towards the vacuum pump the path indicated with v while the product follows the path r a return line 122 bringing it back to a position downstream the exit 114 from the separation vessel 104 the return line 122 may debouch downstream the exit 114 yet upstream a pump 124 used to pump the deaerated liquid onward in the process a vortex breaker 132 may be arranged downstream the exit 114 to prevent any vortex from being generated inside the separation vessel 104 a simple design for a vortex breaker is a pipe segment having a pair of baffle plates in a cross arrangement in the longitudinal direction thus creating four longitudinal compartments there are other more or less elaborate designs for vortex generators which could be used in another embodiment the return line 122 comprises either of a return valve or a pump such as a liquid ring pump ensuring that the liquid level in the return line 122 is controlled another alternative which may be used in combination with the other ones or as a solitary solution is to use an ejector to entrain the liquid from the return line 122 in a downstream direction.