Enlargement of the pulsing flow regime by periodic operation of a trickle-bed reactor

Potential advantages of pulsing flow in trickle-bed reactors include capacity increase and elimination of hot spots through the enhanced mass and heat transfer rates. A disadvantage of naturally occurring pulsing flow is the necessity of relatively high gas and liquid flow rates, especially at elevated pressures, resulting in rather short contact times between the phases. To maintain the advantages but to avoid the drawbacks of pulsing flow, a study has been set up to expand the pulsing flow regime. This is achieved by periodic operation of a trickle-bed, e.g. by cycling the liquid, respectively, the gas feed. It is observed that, due to the periodic operation of a trickle bed, it is possible to shift the transition boundary from trickling to pulsing flow towards lower average gas and liquid flow rates. An additional effect of induced pulsing flow is the possibility to predetermine the pulse frequency, and therefore the time constant of the pulses. (C) 1999 Elsevier Science Ltd. All rights reserved.