Again, it will be assumed that the molar flowrate of liquid and vapor in the bottom section of the column are constant. This is complicated if the steam put into the column is not saturated at the pressure the column operated at. IF The steam is superheated, the steam will exchange heat with the liquid stream coming from stage N, converting the steam to a saturated phase, but also vaporusing part of the liquid stream to vapor. This creates a vapor flow in the column that is larger than the steam feed (VN+1), and a liquid flow in the column that is larger than the bottom product (B).