Revisiting heat losses in lab-scale distillation columns: Quantification, improvement, and influence on miniaturized 3D-printed packings

Abstract

Lab-scale distillation columns with a diameter of 50 mm (DN50) are widely established for experimental investigations during process development and scale-up. In recent years, the diameter was successfully reduced to 20 mm (DN20) by utilizing additive manufacturing to attain new miniaturized packings that attend to the specific miniaturization obstacles. However, since heat losses have a higher influence in a DN20 column, this publication investigates their impact on the operation and data obtained from an additively-manufactured laboratory distillation column. A comparison is provided between the state-of-the-art DN50 size and a miniaturized DN20 size. The heat loss rate is estimated by simulations and experimentally measured for both column diameters with and without thermal insulation. The impact on the internal flow variation and the gas load (F-factor) uncertainty is presented. The findings provided motives for further improvement to minimize the heat loss rate in the DN20 column. This led to the development of a novel active insulation system where custom-dimensioned flexible silicon heaters are utilized for external heat compensation. The system reduces the heat losses significantly and led to a decrease in the F-factor uncertainty from ± 0.09 Pa0.5 to 0.04 Pa0.5 compared to the passively insulated case. Finally, the effect of the heat loss reduction on the mass transfer efficiency is discussed using two additively-manufactured packings, a 3D-printable version of the Rombopak 9M structure (RP9M-3D) and a new miniaturized packing (XW-Pak). The RP9M-3D showed a decrease in separation performance with heat loss reduction while the performance of the XW-Pak remained unaffected.