A fractionation apparatus, comprising: a dividing wall column having a dividing wall forming a feed side and a product side, the dividing wall column having a separator positioned above the dividing wall of the dividing wall column, an aqueous reflux outlet above the dividing wall and an organic reflux outlet above the dividing wall, the feed side having a feed inlet below a top of the dividing wall and above the bottom of the dividing wall, a feed side reflux inlet below a top of the dividing wall and above the feed inlet in fluid communication with the organic reflux outlet, and the product side having a product outlet below a top of the dividing wall and above the bottom of the dividing wall, and a product side reflux inlet below the top of the dividing wall and above the product outlet in fluid communication with the aqueous reflux outlet and the organic reflux outlet; wherein the apparatus further comprises: a ratio controller, an associated flow rate controller (50; 56), and a control valve controlling reflux flow in communication with the organic reflux outlet of the separator to maintain a desired flow rate to the product side and the feed side of the dividing wall column; and a ratio controller, an associated flow rate controller (39; 46), and a control valve controlling reflux flow in communication with the aqueous reflux outlet of the separator to maintain a desired flow rate to the feed side and the product side of the dividing wall column. a dividing wall column having a dividing wall forming a feed side and a product side, the dividing wall column having a separator positioned above the dividing wall of the dividing wall column, an aqueous reflux outlet above the dividing wall and an organic reflux outlet above the dividing wall, the feed side having a feed inlet below a top of the dividing wall and above the bottom of the dividing wall, a feed side reflux inlet below a top of the dividing wall and above the feed inlet in fluid communication with the organic reflux outlet, and the product side having a product outlet below a top of the dividing wall and above the bottom of the dividing wall, and a product side reflux inlet below the top of the dividing wall and above the product outlet in fluid communication with the aqueous reflux outlet and the organic reflux outlet; wherein the apparatus further comprises: a ratio controller, an associated flow rate controller (50; 56), and a control valve controlling reflux flow in communication with the organic reflux outlet of the separator to maintain a desired flow rate to the product side and the feed side of the dividing wall column; and a ratio controller, an associated flow rate controller (39; 46), and a control valve controlling reflux flow in communication with the aqueous reflux outlet of the separator to maintain a desired flow rate to the feed side and the product side of the dividing wall column. a ratio controller, an associated flow rate controller (50; 56), and a control valve controlling reflux flow in communication with the organic reflux outlet of the separator to maintain a desired flow rate to the product side and the feed side of the dividing wall column; and a ratio controller, an associated flow rate controller (39; 46), and a control valve controlling reflux flow in communication with the aqueous reflux outlet of the separator to maintain a desired flow rate to the feed side and the product side of the dividing wall column.