Modeling and Simulation of Batch Distillation in a Copper Still: Economic Assessment for Pisco Production

Pisco is a traditional Peruvian grape spirit whose artisanal production often relies on empirical process control, leading to variability in distillate quality and yield. The lack of quantitative criteria for defining head and tail cuts affects regulatory compliance and reduces profitability for small-scale producers. To address this challenge, a dynamic mathematical model was developed to simulate the batch distillation of fermented grape must in a traditional Charentais-type copper still. The model integrates molar and energy balances, vapor-liquid equilibrium, and segment-wise heat transfer to describe the separation dynamics of a mixture of ethanol, methanol, acetaldehyde, and water. Implemented in MATLAB®, the simulation evaluated head-cut strategies across three initial fermented must compositions-denominated low, intermediate, and high concentration-based on literature ranges of methanol and acetaldehyde content reported for grape-based wines. For low concentrations, no head cut was required to meet regulatory thresholds, maximizing yield. At the intermediate concentration, reducing the head cut from 1.0 to 0.5 % v/v increased distillate recovery by 3.4 % while maintaining compliance. At high concentrations, even extensive cuts were insufficient, indicating the need for upstream fermentation control. Model predictions qualitatively reproduced literature data, and sensitivity analysis showed that the boiler heat-input rate governs the duration of distillation, whereas ambient temperature variations have negligible influence on the separation dynamics. A cash-flow-based economic assessment showed that, when both the higher recovery-based on the 0.5 % v/v head-cut criterion-and the improved selling price were considered, the net present value (NPV) increased by 30.4 %.