Understanding Flow Chemistry and the Different Flow Reactors

Setting up a chemical reaction as a continuously flowing stream brings with it many advantages to chemical production. From cost savings to energy efficiency, increased productivity, improved safety, scalability and more.


The transition to flow chemistry and continuous manufacturing requires a solid understanding of the continuous flow process and how it can be embedded into your production. After working with clients across the globe, we’ve compiled the most frequently asked questions we receive in order to offer clarity on the fundamentals of flow chemistry and types of flow reactors.


What is Plug Flow?

Plug flow is an important characteristic of flow reactors, whereby any two molecules entering the reactor at time zero, exit at a similar time.


What is a plug flow reactor?

A plug flow reactor is such that along the direction of the flow, all the reaction mixture moves along at the same speed; there is no mixing or backflow.


What is Residence Time?

The time any given molecule spends in a flow reactor.


What is Residence Time Distribution (RTD)​?

The probability distribution of time that solid or fluid materials stay inside a continuous flow system. It is used as a measure of plug flow.


What is a CSTR?

A CSTR, also known as a continuous stirred tank reactor, is a reactor whereby the contents are stirred so uniformly that it is assumed that no variation or concentration gradients exist within the vessel. There is a continuous stream in and out of the reactor.


What is a series of Continuous Stirred Tank Reactors?

A series of CSTRs are used to achieve conditions similar to plug flow. An infinite series is hydraulically equivalent to an ideal plug flow reactor.


What is a tubular flow reactor?

A tubular flow reactor has a cylindrical reactor tube with a constant diameter, within which the reaction mixture flows continuously.


What is Passive Mixing? 

Passive mixing utilises no energy input except the pressure from the pump used to drive the fluid flow at a constant rate.

What is Active Mixing?

Also referred to as "Dynamic Mixing". The fluid disturbance that is applied via an external energy source, usually an agitator within the process channel.


What is a scale up in flow chemistry?

Migration of a process from the laboratory scale to the pilot plant scale or commercial scale. Coflore reactors offer a clear scale up route from 30 mL to 100 L, allowing you to manufacture grams to kilotonnes of material continuously!

Useful Terminology in Flow Chemistry

Your flow chemistry jargon buster!

Heat Transfer: the exchange of heat between the physical systems of a flow reactor and reaction media.

Mass Transfer: the movement of material within a flow reactor, more typically applied to the transfer of material between phases within a multi-phase process medium.

Microreactor:  is a device in which chemical reactions take place within a microchannel with typical lateral dimensions below 1 mm.

Microchannel: a process channel within a microreactor with typical lateral dimensions below 1 mm.

Blocking: where the reaction media impedes the flow of a process channel within a flow reactor, commonly due to a build-up of solids. A dynamically mixed reactor is one potential solution to blocking!

Fouling: a build-up of solids on the wetted surfaces of a flow reactor within the flow channel.

Flow Channel: the process channel within a flow reactor.

Flow Rate: a constant rate of flow of the process medium through a flow reactor.

Related Pages...

Plug flow reactors

Useful External Links

Flow Chemistry (organic-chemistry.org)

“One of today's most important tools for modernizing the pharmaceutical industry is a process known as continuous manufacturing”

Director of the FDA’s Center for Drug Evaluation and Research, Janet Woodcock M.D.