Biotechnology: Stirred Tank Reactors

Questions and Answers

What is the primary function of a sparger in a stirred tank bioreactor?

To measure the liquid height in the tank

To improve gas distribution throughout the vessel (correct)

To heat the culture medium

To add pressure to the liquid

If the height of liquid in a stirred tank bioreactor is twice the tank diameter, what is the recommended configuration of agitators?

Three sets of agitators with varying sizes

Multiple separate shafts for agitators

Two sets of agitators mounted on the same shaft (correct)

One set of agitators mounted at the bottom

What happens when the mass flow rate in a continuous stirred tank reactor does not equal the flow rate out?

The stirring speed increases automatically

The exit stream becomes denser

The reactor reaches transient state (correct)

The volume of the reactor decreases

How is the residence time in a CSTR calculated?

By dividing the volume of the tank by the average volumetric flow rate Signup and view all the answers

What is a key characteristic of the exit stream of a CSTR?

It has the same composition as the liquid in the tank Signup and view all the answers

What role do impellers play in a stirred tank bioreactor?

They break down bubbles and enhance mixing Signup and view all the answers

When installing multiple sets of impellers in a stirred tank, what is the recommended separation distance?

Four times the height of liquid Signup and view all the answers

In a stirred tank bioreactor, what is the consequence of having a non-uniform gas distribution?

Poor mixing and mass transfer Signup and view all the answers

What must be true about the composition of the feed in a continuous stirred tank reactor?

It is uniform throughout the reactor Signup and view all the answers

Which of the following describes a steady state in a CSTR?

Input flow rate equals output mass flow rate Signup and view all the answers

Study Notes

Stirred Tank Bioreactors (STRs)

Air is introduced into the culture medium under pressure via a sparger, which can be a ring with holes or a tube with a single orifice.
Spargers, in conjunction with impellers (agitators), facilitate effective gas distribution throughout the bioreactor.
Impellers break down air bubbles into smaller sizes, ensuring uniform dispersion of gas in the medium, thus creating a homogeneous environment.

Agitator Specifications

The number of agitators on the shaft correlates with the height of the liquid in the vessel.
For optimal mixing, the liquid height should align with the designated height; mixing occurs efficiently with a single set of agitators.
If liquid height exceeds two or three times the tank diameter (H = 2T or 3T), additional agitators are required on the same shaft.
Impellers should be spaced at a distance of 4T apart to enhance mixing and mass transfer performance.

Continuous Stirred-Tank Reactor (CSTR) Characteristics

CSTR operates at steady state, where the inlet flow rate must equal the outlet mass flow rate to prevent overflow or emptying.
The feed has a uniform composition; the exit stream mirrors the concentration found within the tank.
Reaction rates are dependent on the final output concentration.
An impeller is installed to ensure efficient mixing within the reactor.
The residence time is calculated by dividing the tank's volume by the average volumetric flow rate, representing how long a reagent spends in the tank.

Description

This quiz explores the principles and mechanisms of stirred tank bioreactors (STRs). Learn about the role of spargers and impellers in enhancing gas distribution in culture mediums. Test your knowledge on the various types of spargers used and their impact on cell culture processes.