Reactor Basics Flashcards
What are the three types of reactors?
- Batch - no flow in/out
- Continuously/completely stirred (CSTR)
- Plug flow
These may occur in different combinations in different process trains
What is the mass balance for all reactors?
Accumulation = inflow - outflow +- sources/sinks
What assumptions are made for batch reactors?
Assume perfect mixing and constant volume. No flow in or out.
Where does the reaction take place in CSTR reactors? What are the assumptions made for CSTR reactors?
Reaction takes place only in the effluent (not in influent/effluent pipes)
Assumptions:
- Instantaneous and completed mixing
- Concentration inside reactor = concentration in effluent
What are the advantages and disadvantages to series reactors?
Advantages:
- improves efficiency
- operational flexibility
- design flexibility (location)
Disadvantages:
- more complex operation
- more costly (construction, operation, maintenance)
How do plug flow reactors work?
Biomass and substrate are continuously fed to reactor, then biomass and degraded substrate are removed from the outlet.
Assume uniform velocity and concentration in radial direction and no mixing or diffusion in axial direction.
Why does a PFR outperform a CSTR?
CSTR:
- concentration inside reactor is equal to outflow
- very low overall concentration
PFR:
- lowest concentration is at the effluent
- higher average concentration overall
