What is a CSTR?

What is a CSTR?

• A. This idealized continuous reactor assumes perfect mixing.
• B. A reactor where the flow is plug flow.
• C. A batch reactor used for fermentation.
• D. A fixed-bed reactor with no mixing.

Answer: (A)

A CSTR is an idealized continuous reactor with perfect mixing. That means the liquid inside is uniform in composition and temperature, so the exiting stream has the same concentration as the contents inside. Because of this uniformity, a simple mass balance applies: in steady state, rate in equals rate out plus generation (or, equivalently, accumulation is zero). The light consequence is that you can relate the input and output concentrations directly through the reactor’s volume and flow rate, without worrying about variations inside the vessel. This differs from a plug flow reactor, where there is little mixing across the cross-section and concentrations can vary along the length; a batch reactor operates with no flow in or out during the reaction, charging, reacting, then discharging; and a fixed-bed reactor involves flow through a packed bed where mixing is not the same as in a perfectly stirred tank. So the description of a continuous, well-mixed tank best captures what a CSTR is.

A CSTR is an idealized continuous reactor with perfect mixing. That means the liquid inside is uniform in composition and temperature, so the exiting stream has the same concentration as the contents inside. Because of this uniformity, a simple mass balance applies: in steady state, rate in equals rate out plus generation (or, equivalently, accumulation is zero). The light consequence is that you can relate the input and output concentrations directly through the reactor’s volume and flow rate, without worrying about variations inside the vessel. This differs from a plug flow reactor, where there is little mixing across the cross-section and concentrations can vary along the length; a batch reactor operates with no flow in or out during the reaction, charging, reacting, then discharging; and a fixed-bed reactor involves flow through a packed bed where mixing is not the same as in a perfectly stirred tank. So the description of a continuous, well-mixed tank best captures what a CSTR is.