Tubular Reactors with a Continuous Polymer Phase

2 Tubular Reactors with a Continuous Polymer Phase 

Web-coating polymerizations (e.g., as used for photographic film and coated abrasives) literally achieve a piston flow reaction environment. Mechanically driven screw devices used as finishing reactors for PET closely approximate piston flow. Motionless mixers can do this as well. However, polymer reactors that closely approximate piston flow are the exception. 

Velocity profile elongation. Low fluid velocities near the tube wall give rise to high extents of pol5merization, high viscosities, and yet lower velocities. The velocity profile elongates, possibly to the point of hydrodynamic instability. 

Thermal runaway. Temperature control in a tubular polymerizer depends on convective diffusion of heat. This becomes difficult in a large-diameter tube, and temperatures may rise to a point where a thermal runaway becomes inevitable. 

Tube-to-tube interactions. The problems of velocity profile elongation and thermal runaway can be eliminated by using a multitubular reactor with many small-diameter tubes in parallel. Unfortunately, this introduces another form of instability. Tubes may plug with pol5nner that cannot be displaced using the low-viscosity inlet fluid. Imagine a 1000-tube reactor with 999 plugged tubes  

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