Question

The purpose of a plug-flow reactor is to

• A. Minimize reactor volume
• B. Maximize contact time between substrate and microorganisms
• C. Allow continuous addition and removal of substrate
• D. Enhance heat transfer

Hint:

• Plug Flow Reactor (PFR): Idealized reactor with no axial mixing, perfect radial mixing.
• All fluid elements have the same residence time.
• Concentration gradients exist along the length of the reactor.
• Often achieves higher conversion per unit volume than CSTR for many reaction types.
• Purpose is to provide a controlled environment for reactions to proceed over a defined path and time.

Answer 1

The Correct Option is B

In biotechnology, the design and function of reactors are crucial for optimizing biochemical processes. A plug-flow reactor (PFR) is notably used to maximize contact time between substrate and microorganisms. This is achieved due to the following characteristics:

1. Flow Pattern: The substrate flows through the reactor in a manner analogous to a sequence of "plugs." This maintains a uniform flow and ensures that the substrates and microorganisms remain in contact for the longest possible duration before exiting.
2. Reaction Efficiency: The design inherently allows for a gradient of concentrations from inlet to outlet, maximizing the contact and reaction time within each 'plug' as it travels through the reactor.
3. Continuous Operation: While continuous reactors like Continuous Stirred-Tank Reactors (CSTRs) allow for easy addition and removal of substrates, in PFRs, the focus is more on the efficient conversion within the space given its flow nature.
4. Heat Transfer: Although PFRs can enhance heat transfer due to their tubular designs, the primary objective remains the prolonged interaction between reactants for effective conversion.

Considering these features, the primary objective of a plug-flow reactor is to ensure optimal contact time between substrate and microorganisms, making it efficient for biochemical and chemical processing applications.