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The unsung benefits of continuous flow to the wider production industry

Continuous manufacturing has solidified its place as a more sustainable alternative to batch production and manufacturing across various sectors.

It’s marketed as a greener, safer, more reliable, versatile, productive, scalable and efficient approach. All of these are key selling points that make continuous flow a more sought-after production process. But what about those less obvious, subsequent benefits of continuous flow that often slip through the cracks?

The merits of flow chemistry that are focused on are those which align with the goals of efficient and high-value production. We see attention drawn to how flow chemistry employs green chemistry and how improved reaction times and product yields are illustrated with a continuous flow approach.

What we don’t see as much is concentration on those more commercial benefits that should still be promoted.

In this blog series, we’ll address in detail how continuous flow technology is more than just a versatile, productive and efficient method of manufacturing- but rather how it also unlocks a number of key advantages which modernize the fine chemical and pharmaceutical industries.

Flow chemistry propels energy cost savings

This benefit is derived from one that has received a magnitude of attention - green chemistry - since it became an aspect of compliance with government regulations. However, as many manufacturers choose to embed continuous flow into their manufacturing process, they overlook the fact that energy efficiency inevitably translates into lower energy consumption.

One of the twelve principles of green chemistry is to maximise energy efficiency. This is done by removing the requirements for extreme temperatures or pressures and opting for ambient process alternatives.

Being more efficient with the amount of energy required and maximising the energy that is being used can be appear difficult. Ultimately, it can be improved in one of two ways, with the starting feedstocks (raw materials) and the reaction methods themselves.

How do continuous reactors compare to batch ones?

When performing a chemical reaction in a batch or fed-batch reactor, the average amount of time the reactor is actually being used for the required chemistry is roughly 30% of the overall time the reactor is running.

Batch reactors require sufficient rest time, which typically involves heating up, cooling down and cleaning. With larger reactors, such as those that process the fermentation for beverage products, they can be running for an average of 10 hours per batch before they’re emptied and the process starts again.

Comparing this to a flow reactor, which doesn’t require much downtime and very little maintenance intervention; flow reactors can achieve almost 100% capacity utilisation for a given production time. They’re built on the principle of continuous reactor operation, after all.

Flow reactors don’t just stop there, in many cases human intervention is next to none. A Continuous flow process can be configured to account for pre and post reaction stages. From avoiding unwanted impurities to preparing reagents or other by-products ready for the next stage of the process.

The entire process can be configured as a single entity rather than individual stages of operation. This means that each stage of a pilot plant in chemical production is operating simultaneously, output products are created and reagents are being prepared in various other pre-reaction stages, whilst there’s a reaction ongoing. This highlights the potential of a flow process to be 100% efficient.

When a flow reactor is running, theoretically, outputs are continuously being produced. But no manufacturing process is completely foolproof, and so occasionally there are instances where downtime is required.

How does energy efficiency lead to energy savings?

It may seem obvious that if something is made more efficient, it is also saving your business economic value too, right? Well, continuous flow can be a difficult one to pinpoint where exactly in the transition the energy costs are reduced.

A more efficient reaction process leads to better optimisation of reaction conditions, including temperature requirements. Heat is an unnegotiable factor in many chemical reactions, particularly if they’re exothermic, such as nitrations and oxidations. In batch, these types of reactions would require an abundance of monitoring time in order to control the input of exothermic chemicals, adding very slowly to avoid overheating.

In flow, the smaller working volumes ensure that chemicals can be added continuously without the risk of overheating. Not only this but flow chemistry better allows for ‘heat recovery,’ ‘heat retention’ and ‘heat transfers’ which all avoid thermal runaways.

Heat recovery in continuous flow technology ensures that the heat which would normally be lost after a batch reaction has completed, is actually collected and re-used continuously during the flow process. This is done through a heat transfer (typically achieved using a heat exchanger) which ensures that the heat transfer/exchanger fluid can be used as an ongoing stream to heat the reaction fluids.

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The heat gained by the reaction fluid is usually equal to the heat lost by the transfer/exchanger fluid, which equates to the total heat transferred. This avoids any surplus heat raising the temperature of the reaction mass and ensures that the heat is continuously transferred into the reaction rather than bulk added, preventing potentially hazardous thermal runaways.

A much larger percentage of the heat put into a flow reactor is recoverable, with little to no room in batch to be able to come even close to this. Pairing a heat exchanger with a flow reactor can ensure that any heat in the outlet stream is recovered and retained to continue heating the incoming feed stream. Recovering heat and reusing it to preheat the incoming feed stream significantly reduces the amount of energy needed throughout a reaction to heat reactants to their desired temperatures.

In batch, it's common for the heat used to be lost, with heat recovery usually impossible. Heating a reaction to its desired temperature in this instance is an ongoing cost as heat is constantly supplied to the system for each reaction batch. As a result, continuous flow reactors offer a more cost-effective solution to heating chemical processes.

A lot of the cost savings are process specific, however knowing the batch reactor volume, the daily productivity, the average heating and cooling demands, the peak cooling demand and the electrical power required, will give you enough insight to assess the ballpark savings in energy if switching to Coflore.

The wider commercial value of continuous flow

The energy cost savings of production not only advance flow chemistry as the go-to alternative for chemical synthesis, but it also paves the way for continuous flow technology as a key player in net zero ambitions of the chemical sector and the corporate economic and sustainability goals of manufacturing businesses, which is the next focus of this blog series.

Scaling up benchtop reactions, after proving the energy savings costs that can be outlined through a flow chemistry switch, maximises the savings available with multi-tonne production. Making an annual heat consumption saving of 2,000,000 MJ whilst heating up the feed stream can lead to an average annual saving of over $55,000.

Convert energy cost-saving prediction numbers. Speak with us to find out how we can turn cost-saving estimates into real, financial value.

Think efficiency, think Coflore!

“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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