Vacuum Stripping Methanol from Biodiesel in a Rotating Packed Bed
Date Issued
2010
Date
2010
Author(s)
Leng, Yih-Shiou
Abstract
This work presented a vacuum stripping process in a rotating packed bed (RPB or HIGEE) to intensify the methanol recovery step in the biodiesel production. The study conducted at system temperatures of 30, 45℃, pressure ranging from 40 to 120Torr, and 1% to 8% of methanol concentration in biodiesel. The stripping ratio increased with increasing temperature and decreasing pressure. Increasing liquid flow rates from 10mL/min to 100~150mL/min lowered stripping ratio by 20% or less. However, the stripping ratio decreased less than that by air stripping. At lower pressure, higher temperature and, the stripping ratio was almost independent of rotor speed and liquid flow rates, which indicated that the liquid concentration was relatively close to equilibrium value. It implied better mass transfer rate, mainly due to higher mass transfer driving force. At the higher methanol concentration, obvious mass transfer intensification was noted with increased rotor speeds. For 8% feed concentration, stripping ratio increased more than 10% when rotor speed increased from 600 to 2400rpm. The highest stripping ratio was 70% for 1% feed concentration, 90% for 4% feed concentration and 72% for 8% feed concentration in our experiments. According to the experimental data, more than 95% stripping efficiency was obtained for 8% feed concentration with two rotating packed bed in series.
The temperature difference between inner and outer edge of the RPB decreased as increasing rotor speed in this vacuum stripping process, suggesting both mass transfer and radial direction heat transfer increasing with rotor speed. At 30℃, 80Torr, 600rpm and 8% feed concentration, 12.6℃ temperature difference was observed in a 4cm packing depth RPB. All temperature differences were carefully recorded in this HIGEE system. Hopefully, it would show some light not only for the further study of vacuum stripping processes, but also for the investigation of temperature-sensitive chemical engineering processes in the rotating packed beds.
Subjects
Rotating Packed Bed
HIGEE
Vacuum
Stripping
Temperature
Pressure
Mass Transfer
Type
thesis
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