Startup operation of an energetically-intensified single-tube type falling film distillation column: Insights from a pilot-scale study

Abstract

Technological advancements in the field of energetically intensified falling film distillation columns have not been paralleled by sufficient published research on comparative startup evaluations for the single-tube falling film distillation column under different thermal energy transfer methods. The present study's originality and significance stem from presenting a startup procedure for a single-tube type falling film distillation column that employs a biphasic thermosyphon as a heat source for producing hydrated ethanol at a pilot scale. The concept of three discrete phases, the discontinuous, semi-continuous, and continuous phases, was employed to characterize the startup operation. The time and energy required for each phase of the startup operation were determined. This study also examined the startup operation with respect to two possible thermal energy transfer methods from the steam chamber to the distillation tube: isothermal and non-isothermal. The experiments were conducted in a pilot distillation column consisting of a single vertical tube, which processed a binary mixture of water and ethanol with a flow rate of 33 kg h−1. No relevant variation in startup time was detected for the three distinct stages when comparing the two heating modes, with a total startup duration of 2.2 h being observed irrespective of the heating configuration utilized. The isothermal heating configuration can produce hydrated ethanol at a rate of 3.0 kg h−1, with an ethanol content increase from 12.5 to 62.8 wt%. However, the non-isothermal heating mode yields a higher ethanol content an increase in ethanol content from 12.5 to 64.3 wt.%, albeit with a lower productivity rate of 1.3 kg h−1. Operating the single-tube type falling film distillation column with the steam chamber under the non-isothermal heating mode required only 2.12 kW for the startup, resulting in a 30.30 % reduction in energy demand compared to the isothermal heating configuration. The presented findings provide an empirical foundation for improving the efficiency and effectiveness of energetically intensified falling film distillation columns.