Understanding Flow Chemistry and the Different Flow Reactors

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.

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FAQ's

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What is the basic principle of flow chemistry?

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In summary, flow chemistry is the principle of performing a chemical reaction as a continuously flowing stream, meaning the reactant reagants are pumped into a reactor at the same rate at which the output is produced. Want to learn more about flow chemistry and how it works? Check out our Overview of Flow Chemistry. 

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Where is flow chemistry used?

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Flow chemistry is used by a number of different sectors within the production and manufacturing industry. Setting up a chemical reaction as a continuously flowing stream brings with it many advantages to chemical production, reaping these benefits are businesses in the fine chemical, pharmaceutical, life sciences, academic and oil and gas sectors, to name a few. 

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What is flow chemistry used for?

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Flow chemistry provides chemical manufacturers with more control over their reactions. It is used to enable improved control through streamlined continuous flow processes. Chemists can enhance their reaction process with flow chemistry to reap a number of business-wide benefits, from cost savings to energy efficiency, increased productivity, continued reproducibility, improved safety, scalability and more. 

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Flow chemistry offers an alternative method of chemical reaction, which can be used in circumstances where batch manufacturing is not a suitable method of production. It is also used to offer a proof of concept for new chemical reactions, whereby reagants are in limited supply and benchtop reactions are preferable. 

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What is a steady-state in flow chemistry?

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In flow chemistry, steady-state is a situation in which all variables are constant, for example, the process temperature and reagent feed flow rates are constant.

 

Typically a Coflore flow reactor takes 2-3 reactor volumes to reach steady-state. Once a flow reactor has reached a steady state then the outlet stream of the flow reactor will remain constant, provided that the variables can be kept constant (i.e. reagent stocks are replenished). Flow reactors can operate at steady-state for days, weeks, or months, depending on the particular chemical process and cleaning/maintenance requirements. 

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What is heat transfer in flow chemistry? 

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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?

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!

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Useful Terminology

Your flow chemistry jargon buster!

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

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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.

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

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

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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!

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

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Flow Channel: the process channel within a flow reactor.

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

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