Distillation process and apparatus with pressure corrected temperature heat source control

A process for separating a feed stream comprising acetic acid and water in a distillation column, the column comprising

• a bottom section in thermal communication with a heat source, the heat source having internal surfaces;
• a feed inlet positioned above the bottom section;
• a first outlet positioned above the feed inlet;
• and
• a second outlet positioned below the feed inlet;
• the process comprising
• introducing the feed stream into the column through the feed inlet;
• at a first heating rate of the heat source, separating the feed stream to form a water-rich first fraction and an acetic acid-rich second fraction;
• measuring an internal temperature of the column at a first position between the first outlet and the second outlet;
• measuring an internal pressure of the column at a second position between the first outlet and the second outlet;
• determining a corrected temperature of the column based on the measured internal pressure and internal temperature of the column;
• and
• determining that the corrected temperature is greater than a target value, and then adjusting the heat source to a second heating rate lower than the first heating rate;
• or
• determining that the corrected temperature is lower than a target value, and then adjusting the heat source to a second heating rate greater than the first heating rate;
• withdrawing at least a portion of the first fraction through the first outlet;
• and
• withdrawing at least a portion of the second fraction through the second outlet, wherein water is present in the withdrawn second fraction in an amount within the range of 500 ppm to 1500 ppm by weight (ppmw),
• wherein at least one of the bottom section, the second outlet, the internal surfaces of the heat source, any connecting pipework between the second outlet and the heat source, and any internals in the bottom section of the column comprise zirconium.