The first start-up strategy is derived from the works of Wu et al. and Pan et al. and will be called discontinuous start-up strategy in this work. The steps involved in both strategies are shown in Fig. . The initial part of the discontinuous and continuous start-up strategy is almost identical, with the only difference that the feed stream is stopped after the reboiler mixture has reached boiling temperature for the discontinuous strategy, while there is no interruption of the feed stream in the continuous case. As eventually, vapor reaches the top of the column, the pressure controller (PC) connected to the condenser duty is activated. The ascending vapor condenses and the condenser fills. When the condenser reaches the specified level, the cascade level control connected to the reflux stream is activated and a liquid reflux establishes in the column.