PFTR Packing

Phases gas-liquid, liquid-liquid, gas-liquid and solid (bio). Intermediate reaction rates. High capacity, high conversion in both gas and liquid phases. Intensive dispersion of gas in liquid. Large number of plates gives plug flow. Some flexibility in varying liquid holdup and exchange heat via cods on plates, d = 40-100 0.6 Ha 3. 

Gas-liquid Residence time, short. Use for very fast reactions, all reaction is in the liquid film and is mass transfer controlled. Gas-liquid surface area max. observed area 800 m /m with the usual range 200-500 m /m or slightly higher than a bubble column. Target species Henry s law constant 10 kPa/mol fraction feed gas concentration 1 vol%. Not for foaming. Limited in handling corrosive or particulates. Some flexibility in varying the gas/liquid volumetric flowrates. Related topic about surface area Section 1.6.1. 

Liquid-liquid can operate as gravity flow or with fluid pulsed operation. For pulsed operation surface area 75-3000 m /m Related topics solvent extraction. Section 4.10, direct contact heat exchange, Section 3.6 and size reduction, Section 8.3. 

Gas-liquid liquid holdup = 0.15 with some flexibility in that the liquid holdup can be adjusted by the weir height typical liquid mass transfer coefficient = kia = 0.01-0.05 1/s = 1-5 X 10 -4.5 X lO m/s for gas phase = 0.02- 

Liquid-liquid Sieve tray holes 3-8 mm with a smaller diameter as the surface tension increases spacing between the holes 3 to 4 times the diameter of the holes to prevent coalescence soon after the drops are formed. For pulsed operation superficial velocities 2 X 10 -0.02 m/s. 

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PFTR pack- Very fast reactions, essentially... 

The fluid in a packed bed reactor flows from one end of the reactor to the other so our first approximation will be to assume no mixing, and therefore the mass balance on the fluid win be a PFTR,... 

For the packed bed reactor we now solve the PFTR equation to yield... 

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