PFTR Bubble Reactor

A bubble reactor is also used for aerobic reactors for the treatment of waste water. The configuration may be a basin, pond or lagoon. See Sections 6.31 and 6.32 for activated sludge reactors. 

A specialized unit is an ozone generator and contact reactor. 

Many other options are available for GL contacting and OTR, Sections 1.6.1 and 1.6.3 provide data to guide in selecting the options. 

Phases GL, GLcS and LL. Relatively slow reactions. Use if the order of the reaction is positive and 95 % conversion is the target, and for consecutive reactions with an intermediate as the target product. The bubble columns tend to operate isothermally and, unless heat is removed in the external loop, this configuration is not used for highly exothermic reactions. 

Gas-liquid For large liquid holdup, slow reactions that are kinetically controlled reactions that require long residence times and low viscosity liquids. Preferred if large gas volumes needed or if the liquid vol 40 m OK for high pressure. Cocurrent surface area 50-400 m /m Downflow surface area 20-1000 m /m. Ha 0.3 and = 4000-10000. Can handle solids. Incurs a high pressure drop. Gas-liquid-catalytic solid Surface area 50-350 m /m.  

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Gas residence time 0.5 to 1.3 s gas velocity 3 to 10 m/s Re > 10, L/D > 100. To eliminate backmixing, Pe > 100. Liquid residence time 1 to 6 s liquid velocity 1 to 2 m/s Re > 10, L/D > 100. PFTR is smaller and less expensive than CSTR. PFTR is more efhcient/volume than CSTR if the reaction order is positive with simple kinetics. For fast reactions, nse small-diameter empty tube in turbulent flow. For slow reactions, use large-diameter empty tubes in laminar flow. If reaction is complex and a spread in RTD is harmful, consider adding motionless mixer (Section 16.11.6.10). Examples hydrolysis of corn starch to dextrose polymerization of styrene hydrolysis of chlorobenzene to phenol esterification of lactic acid. Gas-liquid see transfer line. Section 16.11.6.9, or bubble reactors. Section 16.11.6.11. Liquid-liquid see transfer line. Section 16.11.6.9, or bubble reactors. Section 16.11.6.11. 

If an isolated drop or bubble rises or falls in the reactor, then the flow pattern in this phase is clearly unmixed, and this phase should be described as a PFTR. However, drops and bubbles may not have simple trajectories because of stirring in the reactor, and also drops and bubbles can coalesce and breakup as they move through the reactor. 

Liquid-liquid creation of drops, see Sections 5.3 and 8.3. Superficial dispersed drop velocity 0.001-0.02 m/s with usual values 5.5 L/s m. This bubble column gives the smallest reactor volume compared with STR. For example, for esterification reactor volume divided by the daily production, m dayfkg. PFTR 0.7 m day/kg. 3 CSTR in series. Section 6.26, 0.85 m day/kg. Batch STR, Section 6.27, 1.04 m/ day/kg. CSTR, Section 6.29, 1.22 m day/kg. 

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