FLOW CHEMISTRY
Saltigo successfully transferred the reaction to a pilot-scale continuous unit( pictured), where a multi-week test campaign confirmed stable operation under production-relevant conditions and demonstrated the technical feasibility of continuous manufacturing.
For the HEP manufacturing step, a tubular reactor of approximately 60 L could, based on its space-time yield, replace a 20 m 3 batch reactor. Where the reaction time was around 15 hours in batch operation, the continuous process reduced it to about four minutes. In a conventional batch set-up, the required heating and cooling phases prolong the overall thermal exposure of the reaction mixture and increase the risk of decomposition.
Based on these results, Saltigo developed a conceptual design for a commercial-scale tubular reactor system with integrated heat recovery. This combines the continuous reaction with a continuous distillation set-up. The resulting reaction and separation train is therefore significantly more compact than a conventional batch-based configuration.
Furthermore, effective heat management concepts that reduce overall energy consumption can be implemented more readily than in batch processes. This aspect is becoming increasingly important for process economy and environmental performance with rising energy costs and tightening climateprotection regulations.
In this example, the heat energy of the reaction mass is recovered efficiently in a recuperating step. The recovered energy heats the feed stream as it enters the reaction zone in a counterflow heat exchanger. Only a small amount of additional energy is required to compensate for dissipative losses and maintain the high isothermic temperature in the plug-flow reactor.
This case illustrates that continuous processing creates value not only through the reaction step, but also through the integration of reaction and downstream separation.
Scaling combined concepts
The examples illustrate that successful process design requires more than selecting a reactor type for an individual reaction. The interaction between reaction kinetics, mixing behaviour, residence-time distribution, phase behaviour, heat transfer, materials of construction and downstream processing determines whether a batch, continuous or hybrid concept is appropriate.
Depending on the reaction stage and the relevant process requirements, different reactor concepts can be applied, ranging from microreactors and plug-flow reactors, such as tubular and plate reactors, to CSTR systems, annulargap reactors and hybrid batch / flow approaches. The decisive factor is the reliable transfer of the overall process concept from laboratory development to commercial implementation.
Increasing integration of automated dosing systems, inline analytics and process control technology can further support stable operating windows, facilitate multistage operation and reduce intermediate storage requirements for unstable species.
Where batch is still best
Despite its technical advantages, continuous processing is not a universal replacement for batch operation. Challenges remain particularly in solids dosing, slurry transport, fouling or plugging and in processes requiring long residence times.
In such cases, the flexibility and comparatively low investment requirements of conventional batch processes often remain advantageous. This is especially true for small production volumes or infrequent manufacturing campaigns.
Continuous processing demonstrates its strengths particularly in safetycritical, highly exothermic reactions or wherever precise residence-time control, gas handling, heat removal or reduced reactor inventory are crucial. The objective is therefore not to maximise the number of continuous steps, but to combine operating modes in a way that delivers a robust, safe and economically viable overall process.
Conclusion
Batch and continuous processes are complementary technologies. Early evaluation of batch, continuous and hybrid processing concepts is key to identifying manufacturing routes that combine robust operation, economic viability and consistent product quality. ●
*- Saltidin is a registered trademark of Saltigo
Klemenz Kromm
PROCESS DEVELOPMENT ENGINEER
SALTIGO
Continuous mini-plant for process development and long-term operation
J j klemenz. kromm @ saltigo. com www. saltigo. com
SEP / OCT 2026 SPECCHEMONLINE. COM
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