Question

Continuous stirred tank reactor (CSTR) is characterized by

• A. No mixing
• B. Plug flow
• C. No reaction
• D. Complete mixing

Hint:

Remember: \[ \boxed{\text{CSTR}=\text{Complete Mixing}} \] Whereas a Plug Flow Reactor (PFR) assumes no axial mixing along the flow direction.

Answer 1

The Correct Option is D

Concept: A Continuous Stirred Tank Reactor (CSTR) is one of the most commonly used industrial bioreactors. Fresh medium continuously enters the reactor while an equal amount of culture continuously leaves it. Continuous stirring ensures that the entire reactor contents remain homogeneous.

Step 1: Working principle of a CSTR.
A mechanical impeller continuously stirs the reactor. As a result,
• Nutrients remain uniformly distributed.
• Temperature remains constant.
• Oxygen is evenly supplied.
• Microorganisms experience identical environmental conditions.

Step 2: Characteristic feature.
The defining property of a CSTR is complete mixing. This means that: \[ \boxed{\text{Concentration inside reactor} = \text{Concentration in outlet stream}} \] Every portion of the reactor has nearly identical composition.

Step 3: Eliminate incorrect options.

• No mixing is incorrect because stirring is continuous.
• Plug flow describes a Plug Flow Reactor (PFR), not a CSTR.
• Chemical or biological reactions certainly occur in a CSTR.
• Complete mixing is the defining feature. Final Answer: \[ \boxed{Option (D) is correct \]