Lecture 4: continuous reactors Flashcards
advantages of constant production
- this will give consistent product quality
- they have a simpler control system
- allow for easier automation
- redued manpower requirements
Fundamental principles of continuous reactors
- completely well mixed - stirred tanks
- Plug flow ( not back mixing)- tubes
CSTR
Continuous stirred tank reactor
total moles of a component reacted in a given time frame
Unit output (W)
Equation for unit output for batch
unit output = moles reacted/time
Design equation for continuous reactor
τ = (CA0 - CA)/rA
used when no back mixing is prferred and the fluid moves as a ‘plug’
plug flow reactor
PFR
Plus flow reactor
Each plus acts like a small batch reactor
The concentration changes with length
The time domain is effectively replaced
Tubular reactors
when elements in the reactor mix to some extent prohibiting the ability to achieve perfect plug flow
dispersion
In tubular reactors, net movement of materials can be via:
- Lamina element to flow
- Slippage
- Eddies etc.
a pulse injection
C curve
Fick’s Law for diffusion in the x direction
dC/dt = D (d^2C/dx^2)
Dispersion coefficient
D/uL
