During distillation, the vapour passes upward through the column. The whole column is an enriching section. The vapour is condensed into liquid at the top of the column. Part of the liquid is returned to the column as reflux, and the remainder withdrawn as distillate. Nothing is added or withdrawn from the still until the run is completed. As distillation progress, the MVC in the batch still decreases. In principle, the alternative setup as shown in Fig. is also feasible. Here the vessel is located at the top of the column that is operated as a stripping column. Such a set-up is often known as the inverted batch distillation or the batch stripper. During operation, the LVC are primarily separated from the system. The liquid is the still depletes in LVC and enriches in MVC. In a batch process, the main steps are operated discontinuously. In contrast with a continuous process, a batch process does not deliver its product continuously but in discrete manner. In practice, most batch processes are made up of a series of batch and semi-continuous steps. A semi-continuous step runs continuously with periodic start-ups and shutdowns. higher boiling point. d) Where the material to be distilled is thermally unstable or reacts with other components associated with it at the boiling temperature. e) Where the material cannot be distilled by indirect heating even under low pressure because of the high boiling temperature. f) Where direct-fired heaters cannot be used because of fire hazards.