Effect of cooling conditions on separation of volatile compounds in grappa using tray column and packed columns without reflux

Marcs were distilled using an industrial batch distillation plant. The performance of a tray column and a packed column without reflux were studied under different conditions of vapour cooling obtained by changing the water flow rates (100–350 L h)1). The temperature of cooling water was +12 C. With this kind of plant the cooling conditions normally used for producing grappa in the tray column is a water flow of 200 L h)1 and 250 L h)1 in the packed column. Each distillate was collected in fractions and analysed for ethanol, lower volatile alcohols and esters. The results show that the tray column under a water flow rate of 200 L h)1 has a strong rectification effect on the volatile compounds and it has a significant decrease in separation efficiency at 300 L h)1. Instead, the packed column is poorly affected by the change of the water flow rates from 150 to 350 L h)1 and a distillate very rich of volatile compounds can be obtained. It was concluded that in order to maintain the classical method of grappa production, which consists in cutting the initial and the final fractions of distillate, the packed column is the most suitable.