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Flow Reactor System

What is a flow reactor?

Flow reactors employ continuous flow technology to execute chemical reactions continuously. Reagents are continuously added to a flow reactor vessel inlet whilst product is constantly collected at the reactor outlet, to create a continuously flowing stream of reactants and outputs.

A continuous flow reactor embodies the principles of flow chemistry. Flow reactors are designed to operate at a continuous steady state, which means the internal stream, temperature, reagent feed and flow rates are all constant, to produce an unceasing flow of chemical reactant material which generates a continuous product output.

A flow reactor can provide chemical manufacturers with a more versatile and efficient reactor than the existing batch alternative.

Flow reactor systems vs other reactor types:

Chemical manufacturing is everywhere, this results in a demand for advanced methods of manufacturing which combat drawbacks of traditional chemical manufacturing processes. Within many industrial sectors, types of chemical reactors include:

Continuous flow technology entered the market to overcome problems surrounding scalability, poor heat transfer, safety, sustainability and lack of control found with batch production.


The most suitable reactor is entirely dependent on its desired application. Batch reactors are still routinely employed worldwide due to a historic wealth of information on technical parameters such as heat transfer and mass transfer. Passively mixed reactors can offer heat transfer improvements many orders of magnitude greater than batch reactors, but limitations such as the inability to handle reagent slurry feeds or solids precipitation has limited widespread adoption.

On the other hand, continuous flow reactors can be favourable from a supply chain management standpoint due to its high efficacy, consistency, and QC. Find out more about the benefits and limitations of batch vs flow.

How does a continuous flow reactor system work?

The flow reactor administers the integration of two or more reactive compounds, which are then mixed and flowed through a highly controlled stream to generate a continuous reaction. 


Flow reactions take place in tubular system, whether it be a capillary or micro-structured device made from a non-reactive material. Coiled tubing is commonly added within the design to aid both mixing and heat transfer. Temperature control is then maximized by adding heat or coolant transfer fluid.

The core principle of all flow reactors remains the same, they both involve a continuous flowing mechanism, however, there are different types of flow reactors. Which should be chosen depends on the application but ultimately, the principles remain the same.


Diagram of a flow reactor mechanism 
Comparison of the different flow reactor systems

 Chemical processes in batch production vs flow reactor systems


Diagram of the PFR system 

CSTR flow reactor system explained

Diagram of the CSTR mechanism 

What is the difference between active vs passive mixing in flow reactors?

Several mixing methods are used to combine the raw materials in flow reactors; either by diffusion alone, passive or active (dynamic) mixing.

Passively mixed reactors rely on the fluid velocity of each reagent combining with a particular vessel geometry in order to generate mixing between reagents.

Conversely, active mixing relies on external energy, such as an agitator, which mixes all reactants (similar to how the contents of a batch vessel are mixed with an overhead stirrer). Find out more about active vs passive mixing here.


Plug flow reactors and CSTRs

Continuous flow reactors are all designed to produce chemical reactions within a continuously flowing stream. However, there are different designs used to expedite the process:

Chemical reactions within plug flow reactors use passive mixing technology, meaning they are not continuously stirred, but instead  the reactants flow through the tube as a ‘plug’.

Continuous stirred tank reactors (CSTR) employ active mixing techniques, using an agitated vessel for the continuous feed and discharge of the reaction mixture. Here, the contents are stirred continually, and connecting multiple CSTRs in series results in improved residence time distribution. 

What are the advantages of flow reactors?

Flow reactors primarily offer excellent capabilities to control various reaction conditions and parameters. The main advantages of utilising a flow reactor also include:

  • Advanced heat transfer, improved mixing, (often leading to faster reactions)

  • Easier scalability when compared to batch production

  • Improved safety with better management of hazardous reagents

  • Improved sustainability; lower energy consumption and cost, lower solvent use and low emissions

Scalability is a highly beneficial feature of a flow reactor-based production approach. The reactors can assist with establishing a proof of concept at benchtop R&D phases, and fuel the transition from an initial product to continuous large-scale manufacturing.

Transitioning to continuous flow also ensures that any large-scale production skid is inherently safer due to lower reactive volumes at any one time. Flow reactors are closely partnered with the principles of green chemistry, establishing themselves as a more sustainable solution through maximized energy efficiency, waste reduction, reduced solvent use and more. 

What are the industry uses of flow reactors?


Flow reactors are employed by the life sciences, pharmaceutical, fine chemical, academic, cosmetic and other areas of manufacturing. They are beneficial to a range of applications due to their versatile handling capabilities. The Coflore reactor range is available to customers around the world through our global distributors. They have also been adapted to handle a diverse range of reaction conditions and materials including gas, liquid and solid forms. This makes them suitable for a variety of uses globally:

Laboratory R&D scale in Belgium and beyond

Continuous API manufacturing in India

Flow bioreactors and biocatalysts in research

Safe and scalable fine chemical manufacturing 

The flexible nature of continuous flow reactors means that their use is applicable to various reaction types including chemical transformations, synthesis, polymerizations, hydrogenation and more.  Our Coflore flow reactors can be integrated or stand-alone, for example, we can enhance the mixing approach of the Coflore ATR by integrating the Coflore ACR cell block to process a wide range of multiphase reactions.  

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

Director of the FDA’s Centre for Drug Evaluation and Research,

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