The use of open steam in distillation columns has already been discussed in section 3.3.3. A diagram of an open steam column for use with the MCCabe-Thiele technique is given in Figure 3.37.
Note that it is still useful to know the feed enthalpy for use in the q-line, the distillate product enthalpy (to calculate Qc), and it is essential to know the enthalpy of the bottom product and steam in order to perform an energy balance to calculate the molar flowrates of liquid and vapor in the bottom of the column.