The present disclosure relates generally to processes and apparatuses for separating an effluent in an acetic acid production unit. Accordingly, one aspect of the disclosure provides a process including introducing a feed stream comprising acetic acid and water into a distillation column through a feed inlet, separating the feed stream to form a water-rich first fraction and an acetic acid-rich second fraction, measuring an internal temperature and an internal pressure of the column at positions between a first outlet and a second outlet of the column, determining a corrected temperature of the column based on the measured internal pressure and internal temperature of the column, adjusting a heating rate of a heat source in thermal communication with a bottom section of the column if the corrected temperature differs from a target value, and then withdrawing at least a portion of the separated acetic acid-rich second fraction, the fraction comprising 500-1,500 ppm water by weight (ppmw).

A rotatable, reflux distillation system is disclosed that includes a rotatable, reflux distillation column, a lower end transition pipe, an upper end transition pipe, a rotational drive assembly, and a vapor reduction system. The rotatable, reflux distillation column is angled between 10-20 degrees from horizontal, and has a lower vapor input end and an upper fluid exit end. The lower end of the reflux distillation column is operatively associated with a lower seal housing, and the upper end of the reflux distillation column is operatively associated with an upper seal housing. The lower end transition pipe is operatively associated with the lower end of the reflux distillation column and includes a lower thermocouple, while the upper end transition pipe is operatively associated with the upper end of the reflux distillation column and includes an upper thermocouple and a fluid exit gate. The rotational drive assembly rotates the reflux distillation column. The vapor reduction system reduces the vapor into condensate liquid.

A distillation method includes supplying a batch type distillation column with a liquid that is a process fluid; increasing pressure and temperature of a fluid, with a compressor and supplying the fluid to a reboiler; exchanging heat in the reboiler between the liquid, which has been supplied to the distillation column, and the fluid, which has been increased in pressure and temperature, to heat the liquid and acquire overhead vapor and to condense the fluid; delivering the overhead vapor to a condenser and condensing the overhead vapor into a condensate through heat exchange, removing the condensate; removing residual liquid from the distillation column; and regulating pressure of the distillation column to distill the liquid with heat generated by a heat pump operated over a narrower temperature rising range in the pressure-temperature increasing step.