Comparison of PID-IMC and Hill Control applied to heating power of a fruit-derived alcohol production alembic

Distillation is the most important process in producing fruit distillates, since it defines its aromatic composition. Moreover, it is inevitable to recover toxic compounds during distillation. In particular, methanol, an abundant compound in fruit wines, is toxic for human consumption. Therefore, its concentration may be regulated in alcoholic beverages as lower as possible. The objective of this work is implement a new automatic control strategy, the Hill Controller, to operate automatically an alembic for spirits production, and its performance is compared with a PID_IMC strategy. For minimizing the methanol concentration and maximizing the ethanol concentration, an optimal trajectory of the partial condenser temperature evolution in the alembic was established. The aim of the control system is to track this temperature trajectory. This temperature evolution ensures low methanol concentrations (0.8g/L.a.a.) and high ethanol recoveries. The results are very similar with both controllers. Nevertheless, the response of Hill controller was improved adjusting its parameters in a simple form, but the tuning of IMC-PID involves many paths.